This first lesson of the course reviews some important definitions related to sustainability and sustainable development. We start with very general concepts and then narrow it down to specific principles and how they apply to technologies. Understanding the role of technology in sustainable society is central to this course. As we go from one topic to another, we will always return to the practical question: Is this particular method, product, or design good for our future or should we better look for alternatives? This lesson sets the context. We get introduced to the principles of sustainable design and sustainable engineering and see how they can direct our thinking, innovation, and eventually lifestyle. This lesson also includes introduction to the systems analysis, which becomes an effective tool in understanding interactions between environmental, economic, and social factors in sustainable development.

Learning Objectives

By the end of this lesson, you should be able to:

• understand definitions and principles of sustainable development;
• understand how these principles apply to design and engineering;
• recall the basics of the systems analysis and apply this approach to a simple system as an example;
• identify the role of technology in sustainability framework.

Readings

You will be asked to read the following items throughout your lesson. Look for these readings in the required reading boxes throughout the lesson pages.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

Sustainability as a Term

The term sustainability has a multidisciplinary use and meaning. In dictionaries, sustainability is typically described by many sources as a capability of a system to endure and maintain itself. Various disciplines may apply this term differently.

In history of humankind, the concept of sustainability was connected to human-dominated ecological systems from the earliest civilizations to the present. A particular society might experience a local growth and developmental success, which may be followed by crises that were either resolved, resulting in sustainability, or not resolved, leading to decline.

In ecology, the word sustainability characterizes the ability of biological systems to remain healthy, diverse, and productive over time. Long-lived and healthy wetlands and forests are examples of sustainable biological systems.

Since the 1980s, sustainability as a term has been used more in the sense of human sustainability on planet Earth, and this leads us to the concept of sustainable development, which is defined by the Brundtland Commission of the United Nations (March 20, 1987) as follows:

Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

The following video will further elaborate on this definition and will give a few examples on its meaning.

Video: What is Sustainability (9:43)

With human decision-making involved, sustainability attains a significant ethical aspect and transforms the social paradigm on success, growth, profit, standards of living. This reevaluation requires a broader and more synergistic overview of many components of anthropological ecosystems, including technology.

The topic of sustainable development gained enough importance in the last few decades of the 20th century to become a central discussion point at the 1987 General Assembly of United Nations (UN). Concerned by the quick deterioration of the human environment, uneven development, poverty, population growth, extreme pressure on planet's land, water, forest, and other natural resources, UN issued an urgent call to the World Commission on Environment and Development to formulate a "global agenda for change" [UN, 1987]. The result of this action was the report "Our Common Future," which further served as the global guideline for the world's nations in formulating their political and economic agenda. This document is almost 40 years old now and was followed up by a long array of actions and movements in subsequent years. But let us go back for a little bit and see how it all started.

The original 1987 Report prepared by the World Commission on Environment and Development is a big document (over 300 pages), so I do not advise you to read it all right away. The following reading (about 16 pages) is Chapter 2 of the report, which talks specifically about the concept of sustainable development. So, some of the terms, definitions, and perspectives outlined there will be especially useful for our further work and discussions in this course. So, here is your first reading assignment:

Three Pillars of Sustainability

Sustainable development involves environmental, economic, and social aspects. For a particular process to be sustainable, it should not cause irreversible change to the environment, should be economically viable, and should benefit society. An illustration of the interplay among these three spheres is schematically provided in Figure 1.1. Sustainability is represented as the synergy between society, economics, and environment. The environmental aspects include use of natural resources, pollution prevention, biodiversity, and ecological health. The social aspects include standards of living, availability of education and jobs, and equal opportunities for all members of society. The economic factors are drivers for growth, profit, reducing costs, investments into research and development, etc. There are more factors that will affect sustainability of a social system - these few are listed as examples.

Interaction of social and economic spheres results in the formulation of combined socio-economic aspects. Those are, for instance, business ethics, fair trade, and worker's benefits. At the same time, a combination of economic and environmental interests facilitate increasing energy efficiency, the development of renewable fuels green technologies, and also the creation of special incentives and subsidies for environmentally sound businesses. Intersection of social and environmental spheres lead to creation of conservation and environmental protection policies, establishment of environmental justice, and global stewardship for sustainable use of natural resources. This framework is in some way a simplification, but it proved to be helpful in identifying key areas of impact and set the basis for objective analysis. Further in this course particular processes and technologies will be often evaluated in terms of social, economic, and environmental impacts, although we should understand that those three pillars are never fully isolated from one another.

Figure 1.1. Interplay of the environmental, economic, and social aspects of sustainable development.

Credit: Mark Fedkin. Adopted from the University of Michigan Sustainability Assessment [Rodriguez et al., 2002]

Dimensions of Sustainability

The above-mentioned three pillars of sustainability are very common terms in the literature, media, and communications and convey a simple idea to grasp. However, the interconnections between these three pillars are not at all simple and can actually occur in different planes of thinking. Three fundamental meanings or dimensions of sustainability were defined by Christian Becker in his book "Sustainability Ethics and Sustainability Research" as continuance, orientation, and relationships. To understand what those dimensions exactly mean, please refer to the following reading. As discussed in this chapter, the multi-dimensional nature of sustainability is something that often results in confusion and miscommunication between different entities and spheres involved. For example, an environmentalist, economist, and politician can discuss sustainability as a project goal but actually have three different goals in mind. So, new project developers in the sustainability era should certainly seek to broaden their perspective and, at the same time, develop sufficient depth in articulation of their sustainability vision. Enjoy the reading:

If you completed the short reflection note in the box above - good job! You will find it very beneficial to write down some of your own thoughts while you are still fresh off your reading.

United Nations’ 17 Sustainable Development Goals (SDG)

In September 2015, the UN General Assembly adopted the 2030 Agenda for Sustainable Development, which converged in setting 17 sustainable development goals. These goals link the conceptual understanding of sustainability to specific focus areas, where actions are needed.

These goals became the common framework for governments and organizations developing sustainability plans, assessing new initiatives and emerging technologies, and tracking progress. So, it would be wrong not to include them here:

UN Sustainable Development Goals 

Credit: n.a. “UN Sustainable Development Goals” UN. 

I do have to note that most of these goals still sound very general and would require specific measures (or metrics) to assess their achievement.

Further in this course, we will occasionally revisit the definitions and interpretations of sustainability. This is one of the concepts that sets context for our main focus in this course - technology role and assessment. In the next section of this lesson, we will start seeing how technology is sometimes considered the cornerstone of the society development and survival. While some theories heavily bet on technology as the universal solution to society's ever-growing needs, others are much more skeptical. So, prepare for some controversy.

Steady State Economy

Herman E. Daly (1938-2022), a renowned expert in ecological economics, who has been a longtime proponent of the concept of sustainable steady state economy (as opposed to economic growth), formulated several basic rules for a sustainable society, known as Daly Rules:

1. Renewable resources - e.g., groundwater, biomass - must be used no faster than the rate at which they regenerate.
2. Nonrenewable resources - e.g., minerals, fossil fuels - must be used no faster than renewable substitutes for them can be put into place.
3. Pollution and wastes must be emitted no faster than natural systems can absorb them, recycle them, or render them harmless.

Sustainable steady state theory states that human societies can grow to a special state, where resource supply and consumption are balanced. This should be considered a sustainable steady state. After this balance point has been reached, only refinement of societies (via better use of available resources through more efficient technologies) instead of growth (increase in supply and consumption of resources) should be pursued.

According to Daly’s theory, economic growth cannot be maintained forever because the planet and its resources have finite physical dimensions and capacity:

“If resources could be created out of nothing, and wastes could be annihilated into nothing, then we could have an ever-growing resource throughput by which to fuel the continuous growth of the economy. But the first law of thermodynamics says NO. Or if we could just recycle the same matter and energy through the economy faster and faster we could keep growth going. The circular flow diagram of all economics principles texts unfortunately comes very close to affirming this. But the second law of thermodynamics says NO.” [Daly, 2009]

But is reaching a sustainable steady state in fact realistic and practically achievable? Daly argues that there is a practical alternative to the economic growth paradigm. That would rely on a number of critical economic steps and policies. Daly's measures may seem controversial and somewhat radical at a national or international scale, but they touch an important scaling question: how large can a system be and keep its potential for sustainability?

If you are interested in learning more about Dr. Daly's views on economic growth and a steady state economy, check out his interview below.

Video: "Herman Daly on the Economy and the Environment" (51:06)

Oscillating Steady State

Contrary to the steady-state paradigm, an alternative view expressed in works by Howard T. Odum and collaborators (for example “Environmental Accounting: Emergy and Decision Making” 1995) considers the whole planet a self-organizing system, where storages of resources are continuously depleted and replaced at different rates, and matter recycling and reorganization is driven by solar, geothermal, and gravitational energies. It is hypothesized that one of the possible reasons for oscillating systems to be preferable over steady state systems is that they are governed by the system feedback to changing environmental conditions or depletion of one or other storage. The system should be able to tune its performance according to the changing environment.

As the diagram in Figure 1.2. illustrates, net primary production and storage of resources (expressed as Quantity Q) develop faster than consumer assets (expressed as Quantity C) until the system reaches a threshold where autocatalytic and higher order pathways are accelerated. At the threshold, consumer assets show a sudden increase at the expense of the environmental storage (consumer pulse). As the resources are used up quickly, consumer assets drop, allowing a new cycle of building resource storage to begin. In the case of global economy, the storages can be represented, for example, by oil, minerals, topsoil, and other slowly renewable resources, while the consumer assets are human economies and civilization. The theory presumes that this kind of pulsation can be sustained over time.

Figure 1.2. Pulsing growth paradigm.

Credit: Odum, 1988

Anthropogenic Ecology Theory

Some contemporary scientists find Daly's arguments overly pessimistic. For example, Erle Ellis, an associate professor of geography and environmental systems at the University of Maryland, Baltimore County, and a visiting associate professor at Harvard’s Graduate School of Design, argues that over the course of the anthropogenic history, humans have almost never relied simply on the carrying capacity of natural ecosystems, but rather created specially engineered ecosystems. Such artificial eco-niches utilize intelligent approaches and technologies for extracting more usable resource from the nature. So, essentially, Ellis infers, there is no problem of limiting carrying capacity due to creative transformative powers of humankind.

Within the anthropogenic ecology theory, the emergence of new sociocultural niches in human society is represented as a novel evolutionary process in the Earth system. These niches are the result of re-shaping the biosphere into new organizational level which allows virtually unlimited upscaling of societies through culturally mediated changes.

To better understand and to analyze the dynamics of feedback and oscillations within socio-ecological systems, it would be useful for us to look at the basics of the systems thinking approach. This thinking framework is especially important to sustainability science, because it allows tracking logical interconnections between natural factors, economic factors, social motifs. More details are given further in Sections 1.5-1.8 of this lesson.

The next question for us to explore is how the meanings of sustainability extend into technical spheres, specifically engineering, design, and technology development.

The term design is normally referred to the "way of doing things or making things" in various areas of human activity. Design is always driven by a specific objective, such as making the product or system most efficient, or most profitable, or most aesthetically impressive, etc. Such objectives can be drastically polar and to reach them, designing phase may require change of thinking and high level of creativity. So, what is sustainable design?

This concept was largely advocated by William McDonough, an American designer, architect, author, and thought leader, who espouses a message that we can design materials, systems, companies, products, buildings, and communities that can continuously improve over time.

"If design is the first signal of human intention, our intention today can be to love all ten billion people who will live on our planet by 2050. We can do this. If we imagine and embrace our cities as part of the same organism as the countryside, the rivers and the oceans, then we can celebrate ourselves, all species and the natural systems we support and that support us. This is our design assignment. If we are principled and have positive goals, we can rise to this occasion. It will take us all; it will take forever—that is the point." (McDonough, 1992)

The concept of sustainable design is supplied with some lively illustrations in McDonough's TED Talk

Watch this video: William McDonough's TED Talk (19:46)

McDonough crafted sustainable design principles for Expo 2000, The World’s Fair, which became known as "The Hannover Principles: Design for Sustainability." This document has wide philosophical and ethical dimensions and should be seen as a living document committed to the transformation and growth in the understanding of our interdependence with nature and future generations.

Book cover of the Hannover Principles

Credit: McDonough, 1992

THE HANNOVER PRINCIPLES

1. "Insist on rights of humanity and nature to coexist in a healthy, supportive, diverse and sustainable condition.
2. Recognize interdependence. The elements of human design interact with and depend upon the natural world, with broad and diverse implications at every scale. Expand design considerations to recognizing even distant effects.
3. Respect relationships between spirit and matter. Consider all aspects of human settlement including community, dwelling, industry and trade in terms of existing and evolving connections between spiritual and material consciousness.
4. Accept responsibility for the consequences of design decisions upon human well-being, the viability of natural systems and their right to coexist.
5. Create safe objects of long-term value. Do not burden future generations with requirements for maintenance or vigilant administration of potential danger due to the careless creation of products, processes, or standards.
6. Eliminate the concept of waste. Evaluate and optimize the full lifecycle of products and processes, to approach the state of natural systems, in which there is no waste.
7. Rely on natural energy flows. Human designs should, like the living world, derive their creative forces from perpetual solar income. Incorporate this energy efficiently and safely for responsible use.
8. Understand the limitations of design. No human creation lasts forever and design does not solve all problems. Those who create and plan should practice humility in the face of nature. Treat nature as a model and mentor, not as an inconvenience to be evaded or controlled.
9. Seek constant improvement by the sharing of knowledge. Encourage direct and open communication between colleagues, patrons, manufacturers and users to link long term sustainable considerations with ethical responsibility, and reestablish the integral relationship between natural processes and human activity."

It is a philosophy that can be applied in the fields of architecture, landscape architecture, urban design, urban planning, engineering, graphic design, industrial design, interior design, fashion design, human-computer interaction, and many other areas depending on modern technologies.

In the consideration of the above principles, a strong emphasis is put on #6 [waste elimination], since it perhaps has the most profound impact on environment and human health as well as contains possible solutions for smart use and reuse of limited natural resources. A good waste prevention strategy would require that everything brought into a facility or process be recycled for reuse or recycled back into the environment through biodegradation. This would mean a greater reliance on natural materials or products that are compatible with the environment. Any resource-related development is going to have two basic sources of solid waste — materials purchased and used by the facility and those brought into the facility by visitors. The following are some waste prevention strategies that apply to both, although different approaches will be needed for implementation:

• Low-impact materials: Choose non-toxic, sustainably produced or recycled materials which require little energy to process.
• Energy efficiency: Use manufacturing processes and produce products which require less energy.
• Emotionally Durable Design: Reduce consumption and waste of resources by increasing the durability of relationships between people and products, through design.
• Design for reuse and recycling: "Products, processes, and systems should be designed for performance in a commercial 'afterlife'."
• Biomimicry: "redesigning industrial systems on biological lines ... enabling the constant reuse of materials in continuous closed cycles..."
• Service substitution: Shift the mode of consumption from personal ownership of products to provision of services which provide similar functions, e.g., from a private automobile to a carsharing service. Such a system promotes minimal resource use per unit of consumption (e.g., per trip driven).
• Renewability: Materials should come from nearby (local or bioregional), sustainably managed renewable sources that can be composted when their usefulness has been exhausted.

Here are some of the examples how design approaches attempt to promote the sustainability principles:

Emotionally Durable Design

 

The 2CV Chronicles Project

Credit: Liz Nehdi / The 2CV Chronicles Project

The concept and philosophy of Emotionally Durable Design was pioneered by Jonathan Chapman, Professor of the University of Brighton (UK). According to this philosophy, increasing the resilience of relationships established between consumers and products reduces the consumption and waste of natural resources. Chapman states that "the process of consumption is, and has always been, motivated by complex emotional drivers, and is about far more than just the mindless purchasing (and discarding) of newer and shinier things". For example, these couple of images illustrate personalized design of products, when in addition to their normal function, the objects also help the owner to make a statement or express their style of life. To this end, 'emotional durability' can be achieved through consideration of the following five elements:

CAPTION_CONTENTS.

Credit: Making It Magazine

• Narrative: How users share a unique personal history with the product.
• Consciousness: How the product is perceived as autonomous and in possession of its own free will.
• Attachment: Can a user be made to feel a strong emotional connection to a product?
• Fiction: The product inspires interactions and connections beyond just the physical relationship.
• Surface: How the product ages and develops character through time and use.

As a strategic approach, "emotionally durable design provides a useful language to describe the contemporary relevance of designing responsible, well-made, tactile products which the user can get to know and assign value to in the long-term."

Biomimicry

Morpho Butterfly

Credit: CREDIT_CONTENTS

Biomimicry is the imitation of the models, systems, and elements of nature in design, engineering, and science, primarily for finding new solutions to scientific or technological challenges. Biomimicry has given rise to new technologies created from biologically inspired engineering at both the macro scale and nanoscale levels. In fact, humans have been looking at nature for answers to both complex and simple problems throughout world history. Nature has solved many of today's engineering problems, such as hydrophobicity, wind resistance, self-assembly, and harnessing solar energy through the evolutionary mechanics of selective advantages. Here are several examples (out of many) showing the use of biological subjects as models in technology.

Because natural systems are a priori sustainable, designs observed in the nature can be viewed as prototypes of smart technologies for potential anthropogenic sustainability systems.

1. A. The morpho butterfly (shown in the image above from Wikipedia) gains its color due to the special structural orientation of scale in its wings. Incident light is reflected at specific wavelengths to create vibrant colors due to multilayer interference, diffraction, thin film interference, and scattering properties. Now, some companies (Qualcomm) use this principle in manufacturing colored displays at much lower power consumption (as compared to production of dyes).

CAPTION_CONTENTS.

Credit: http://en.wikipedia.org

1. B. Researchers studied the termite's ability to maintain virtually constant temperature and humidity in their termite mounds in Africa despite outside temperatures that vary from 1.5 °C to 40 °C (35 °F to 104 °F). Researchers initially scanned a termite mound and created 3-D images of the mound structure, which revealed construction that can influence human building design. The Eastgate Centre, a mid-rise office complex in Harare, Zimbabwe (image on the left), stays cool without air conditioning and uses only 10% of the energy of a conventional building of its size (Source: Biomimicry).
2. C. Holistic planned grazing, using fencing and/or herders, seeks to restore grasslands by carefully planning movements of large herds of livestock to mimic the vast herds found in nature, where grazing animals are kept concentrated by pack predators and must move on after eating, trampling, and manuring an area, returning only after it has fully recovered. Developed by Allan Savory, this method of biomimetic grazing holds tremendous potential in building soil, increasing biodiversity, reversing desertification, and mitigating global warming, similar to what occurred during the past 40 million years as the expansion of grass-grazer ecosystems built deep grassland soils, sequestering carbon and cooling the planet (Source: Biomimicry).
3. Paper wasps' nests are made out of cellulose (or chewed-up wood) and wasp saliva. The wasp uses saliva that has a lot of protein in it, and that protein mixed with the cellulose creates a water-insoluble but also waterproof covering. It is interesting that in rainy environments, wasps are found to use more protein in their saliva in order to make the nest more waterproof. And because protein is quite expensive from a wasp’s standpoint because they have to go get more insects to get more protein, they are only going to use it if they really need it. So, if this is in a dry environment or protected from overhead, they are not using as much protein. This idea can be borrowed to make non-toxic, waterproof paper, or other biodegradable materials (Source: Biomimicry Case Examples)

"Engineering in context, engineering with a conscience, engineering for a finite planet and the indefinite future"

Sustainable engineering should be based on principles that support sustainable development, as defined in the upper sections of this lesson. Engineering forms an interface between the design (i.e., the idea how to provide a sustainable solution to a technical problem) and implementation and production. In case of technology development, engineering phase is linked to almost every level of technology readiness spectrum. Sustainable engineering principles should be contemplated and applied early to ensure that technology development and scale-up follow the environmentally benign route. It will be hard to turn back to redo and redesign things from later stages! In that sense, the sustainable engineering principles should be taken into account in decision making for both research and industrial projects, as well as in policy making and decisions regarding funding of technological research.

There have been multiple attempts by academic and industrial institutions to formulate sustainable engineering principles. All of them fall within the triangle with Environmental, Social, and Economic values as cornerstones. The overarching goal is to generate a balanced solution to any engineering problem. If an engineering project benefits one of these three aspects but ignores the others, we have a lopsided system which creates tension, instability, and new problems in the long run.

Here are some of the aspects that differentiate the traditional and sustainable approaches in engineering:

The diagram in Figure 1.3. presents a consolidated framework for sustainable engineering principles, which are in part adopted from the work of Gagnon and co-authors "Sustainable development in engineering: a review of principles and definition of a conceptual framework" (2008) and from the green engineering principles established by Sundestin Conference (2003).

Figure 1.3. Classification of sustainable engineering principles versus environmental, social, and economic criteria.

Click for text description. This will expand to provide more information.

Figure 1.3 text description

Various principles of sustainable engineering are placed on the perimeter of the triangle. On the triangle's bottom edge are the Society pole (left) and the Economy pole (right). From left to right, the four principles shown are as follows:

• Offer individuals and communities the opportunity to increase their capabilities.
• Know your "needs" and "wants." Put primary focus on achieving needs of larger number of individuals.
• Allocate in a fair manner benefits and costs related to economic activity and public policies.
• Maintain a positive genuine long term investment considering all types of capital.

On the triangle's left edge are the Society pole (bottom) and the Environment pole (top). From bottom to top, the four principles shown are as follows:

• Ensure that all material and energy inputs and outputs are as inherently safe and benign as possible.
• Look beyond your own locality and the immediate future.
• Preserve access to exosystems services essential to health and wellbeing.
• Preserve biodiversity and respect all life forms, regardless of how useful they are to humankind.

On the triangle's right edge are the Environment pole (top) and the Economy pole (bottom). From top to bottom, the four principles shown are as follows:

• Stay within ecosystem's carrying capacity in terms of resource development and waste assimilation.
• Develop closed cycles of operation and consumption to minimize waste.
• Offset the use of non-renewable resources by investments in renewable substitutes.
• Stimulate innovation to facilitate the adaption of more efficient and greener technologies.

The principles shown at the center of the triangle are as follows:

• Engineering processes holistically, use system analysis, and integrate environmental impact assessment tools.
• Seek stakeholder involvement while respecting local subsidiarity and cultures.
• Internalize all costs within the value of goods and services (polluters must pay).

Credit: based on concepts from Gagnon et al., 2008

Figure 1.3 lists the various principles of sustainable engineering versus environmental, social, and economic poles. Some of these principles clearly gravitate towards one of the corners of this triangle and thus address particularly societal, environmental, or economic concern. But some others, which are placed along the sides of the triangle, have connections to two of the poles of the diagram and address both societal and economic, or both economic and environmental concerns in some proportion. Those principles placed in the center of the diagram combine all three aspects of sustainability to a certain degree and hence their implementation would benefit all societal, environmental, and economic stakeholders. We should not consider this collection of principles set in stone. Many sources and organizations build on the existing documents and provide their own visions. I invite you to reflect on this diagram and provide your comments for making it more complete and more concrete for our future consideration.

These principles can be viewed as guidelines for a specific engineering project. We are going to look at a specific example where the engineering solution was able to address the need and benefit sustainability, not sacrificing one for the other.

Jubilee River Case Study

This example presents a success story about how sustainable engineering has been applied to address a critical community need. The need is always placed in the center of an engineering project and directs design efforts. In this case, the need was a flood prevention system. While the traditional approach of creating the concrete trapezoidal channel would address the need perfectly and cost-effectively, it would have environmental and social trade-offs. For example, construction would destroy or disturb natural vegetation and wildlife, cause high soil erosion, create a large amount of construction waste, and have a negative aesthetic impact.

The alternative approach was to convert these problematic trade-offs into benefits. That required some additional investment and a wider range of collaboration among civil engineers, ecologists, and landscape architects. The result was creation of a permanent, landscaped, ecologically compatible relief channel, with amenities and environmental features of a natural river (Figure 1.5), which eventually became an asset to the community and increased rather than decreased the quality of life.

Figure 1.4. Current state of the Jubilee River landscape.

Credit: David Short (via Flickr)

To summarize the information in this reading, please provide answers to the following questions:

The goal of an engineering project can be to create a system, a device, a process, or any other outcome that would provide a certain service or benefit to society. One of the important outcomes of an engineering project is the creation of technology.

Role of Technology

Role of technology can be actually viewed as the interface that provides connection of an idea realized through design and engineering effort with practical and consumable outcomes, such as products or services. The latter would affect and shape societal lifestyle over time. Figure 1.4 presents a hierarchical view of these connections in the sustainability context.

Figure 1.5. Hierarchy of sustainability guidelines and role of technologies emphasized.

Credit: Mark Fedkin © Penn State is licensed under CC BY-NC-SA 4.0

Figure 1.5 shows how the most general sustainability principles are narrowed down to specific material outcomes for the society. The principles of sustainability guide the sustainable design, the process of thinking. This stage determines how things are supposed to be made and how they will function over their whole lifecycle. Further down the funnel, the sustainable engineering stage deals with technical implementation of ideas. Sometimes it is not an easy process, and some aspects of design may be changed or compromised. When eventually the design and engineering routes practically converge, we may have a technology created. Technology provides processes and products. Only then the benefits of new ideas and new engineering developments become available to society. Here we can identify the role of technology as some sort of portal through which the established principles of sustainable design and engineering may affect people’s lifestyle. Because of people's strong dependence on multiple technologies, those become the factors that can facilitate change in society and can even become tools of manipulation and initiation of global trends.

This way of thinking emphasizes the importance of technologies in the whole hierarchy of causes and factors that regulate the sustainable development.

To build the contextual framework for applying the sustainability principles, we need to develop some background in systems. We often hear terms like “systems thinking” or “systems approach”. Or in some cases, to initiate a sustainable and long-lasting change, we need to change the “system” rather than trying to change the final result. The material in this section is the tip of a bigger iceberg – system analysis is applicable to a very broad scope of problems, from economics to climatology, and it very often becomes a powerful tool in strategic decision-making. In this course, the systems approach will be essential when we consider technology trends and implementation in a broader societal context, where multiple forces – economic, environmental, political, educational, and psychological - come into play. It is not about simple ‘yes/no’ questions – it is our way to explore the complexity and possibly to find answers to ‘why’ questions for the most part. Let us start with some definitions.

Are we dealing with a system?

A system is an interconnected set of elements that is organized in a way that achieves a purpose. Three distinct entities of any system are elements, interconnections, and purpose (or function). These ensure system’s integrity and often determine such system’s properties and behaviors as development, resiliency, self-organization, self-repair, and eventually - sustainability. You can tell that you are dealing with a system, not a random collection of components, if you can identify the mutual impacts between the components and observe the outcome or behavior over time that is different from the outcomes or behavior of the separate components on their own.

For example, a forest is a system consisting of trees, soil, multiple species of flora and fauna – all of which are interconnected via food chains, nutrient flows, energy exchange, and many other chemical and physical processes. Its function is to provide environment and nutrition for sustaining living organisms and also to produce oxygen via photosynthesis. If one takes an element out of the system (e.g., taking a certain tree species and planting it in an isolated environment, or taking an animal and placing it in a zoo), those elements would behave differently, the same as the system deprived of a certain element will be affected and will react to the change.

In a social context, for example, a village is also a system, not a simple aggregation of houses and people. Houses may be connected through the utility networks, people are connected through trade, collaboration, and social relationships. Disruption of life and function on one side of the village would cause system’s reaction and change.

In the technical world, system functions can be even more obvious, since many engineering systems are designed by people for a specific purpose. Thus, a power plant system has a purpose to produce electric power and distribute it to a community or facility. It consists of equipment, workers, transportation means, fuel stocks, etc., all of which are interconnected in power production cycle.

System elements

Next, we are going to cover three types of elements that will be used in system analysis further on. Specifically, those include: stocks, factors, and decision points.

Figure 1.6. Notations of three types of elements included in system analysis.

Credit: Mark Fedkin © Penn State is licensed under CC BY-NC-SA 4.0

Stocks

Stocks can be represented by sort of matter, commodity, or good. Stocks are cumulative and are characterized by measurable amount. They can accumulate (increase), deplete (decrease), or stay steady. In system diagrams, we are going to show each stocks as a box.

Examples of stocks:

• Money on the bank account
• Number of trees in the forest
• Number of people living in a town
• Amount of food stored for winter
• Amount of energy stored or generated at a power plant

Very often, the stability of a system depends on the maintenance of its stocks. If the bank account is stable or growing, we believe that whatever system maintains it is working well. If there is no decline in tree population, we assume the forest is healthy.

Factors

Factors can be represented by processes, flows, phenomena, actions, and even feelings that have influence within a system. Factors are measurable, but not necessarily cumulative, and are typically characterized by rates or intensity of process rather than countable amounts. Rates are important since they will affect the variations of stocks. In system diagrams, we are going to include factors in ovals.

Examples of factors:

• Rate of tree growth in the forest
• Air temperature at the forest location
• Electricity price at local market
• Solar irradiance at a specific location
• Number of cups of coffee you drink per day

Almost anything can be included as a factor in a system, as long as its variation influences the system state or other elements.

Decision Points

Decision points are very special elements that represent deliberate controls of the system by humans. Humans make a variety of decisions, which may or may not be dictated by the system behavior, and can be based on knowledge, personal choices, feelings, political views, conscience, etc.

Examples of decision points:

• Adopting a policy
• Decision to invest in growth of business (or not)
• Decision to restrict construction or practice
• Decision whether the stock level is dangerously low

In system diagrams, we are going to depict decision points as diamonds.

There may be other elements that are distinguished in various system models. But for the sake of simplicity, we are going to mainly operate with the three elements described above.

System Connections

In a system, elements are interconnected and may influence one another. If connections are not identified, the collection of elements you have, may not be a system after all. The following types of connections are most important.

Positive Coupling

Positive coupling is when an increase in A results in an increase in B.

• Increase in sunlight leads to higher solar panel output
• Increase in coal combustion results in growth of CO2 emissions
• More chickens, more eggs

This will also work backward: Fewer chickens, fewer eggs, etc.

This type of connection can be shown with a regular arrow:

Figure 1.7. Example of a positive coupling.

Credit: Mark Fedkin © Penn State is licensed under CC BY-NC-SA 4.0

Negative Coupling

Negative coupling is when an increase in A results in a decrease in B.

• Increase in mileage decreases car’s service life
• Amount of food consumed decreases the feel of hunger
• Increase in spending decreases amount of money in the bank account

And again, vice versa, in case of a negative coupling, a decrease in A would increase B. You can check if this opposite connectivity works with the above examples (it is not always the case).

This type of connection can be shown with a circular arrow:

Figure 1.8. Example of a negative coupling.

Credit: Mark Fedkin © Penn State is licensed under CC BY-NC-SA 4.0

It is important to understand that the connection drawn from A to B is not at all identical to the connection from B to A. We cannot simply put the arrow both ways automatically. For one of the example of positive coupling, we said: “increase in sunlight leads to higher solar panel output”. Obviously, the reversed relationship will not work: increase in solar panel output will NOT increase the amount of sunlight, and in fact it will not affect the amount of sunlight at all. So, before drawing the arrow from B to A, we need to think first if there is actually a reverse impact, and if yes, then whether it is a positive or negative coupling.

Feedback Loops

Feedbacks are very interesting properties of systems. Feedbacks are higher in the hierarchy of causal connections than couplings. While a coupling simply denotes the influence of one system element on another, feedbacks go further to show how those other elements impact the original cause. A feedback is always a loop, and therefore must contain at least two, but often more couplings in it. Here are some examples.

• More chickens, more eggs. But if we have eggs that can hatch and produce more chickens, we have a reverse connection: more eggs, more chickens. This is feedback.

Figure 1.9. Example of a feedback loop – chicken and egg problem.

Credit: Mark Fedkin © Penn State is licensed under CC BY-NC-SA 4.0

• More stuff bought, less money left. That is a negative coupling. However, the less money is available, the less stuff we can further buy. This is a positive connection on the way back. And again, using these two couplings, we can identify a feedback loop between these two elements.

Figure 1.10. Example of a feedback loop – shopping dilemma.

Credit: Mark Fedkin © Penn State is licensed under CC BY-NC-SA 4.0

We can see from these two simple examples that feedback always “backfires” to the original element and affects any other element in the loop via circular impact.

Feedbacks are interesting internal mechanisms that can either stabilize or destabilize the system. In the next section of this lesson, we will consider two main feedback types – positive and negative – and see what effects they can cause.

Positive feedbacks

Imagine that you have some money in your bank account. The more money you have, the more interest you earn annually. That interest is added to your account balance, which earns you even more interest. So we can definitely see how A affects B, and B affects A in this case:

Figure 1.11. Positive feedback loop consisting of two stocks and two positive couplings.

Credit: Mark Fedkin

As the two positive couplings act in circles within this loop, your account balance keeps growing. Such a feedback loop is called positive or reinforcing (here is the “+” sign in the loop), because the system sort of feeds itself continuously, amplifying the impacts over time. In the beginning, the growth may seem slow, but year after year, it goes faster and faster (see typical growth in savings in Figure 1.12). The more money is there, the more is added. This kind of growth is called exponential in mathematical terms (and there is an equation to describe this curve as a function of time).

Figure 1.12. Growth of account balance with a 6% interest rate.

Credit: Mark Fedkin

Evidently, exponential growth can be a good thing or a bad thing, depending on what stock is growing. Here are some other examples of growth stimulated by positive feedback:

• The more chickens there are in the barn, the more eggs they can lay. The more eggs there are to hatch, the more chicks will be produced which will grow the population of chickens.
• The more soil is eroded, the fewer trees are able to grow on it. The fewer trees there are to stabilize the soil, the more erosion will occur.
• The more individuals are infected with a virus, the more people they can potentially infect. The unrestricted dynamics of virus spread follow the infamous exponential curve.
• In war or conflict, the more damage one side causes to the other, the more hatred and resistance are generated from the other side back to the first. Stronger pushback causes even harsher aggression, thus escalating the conflict.
• The more a child plays a musical instrument, the more pleasure she gets from the sound, and the more willing she is to practice more.

Now think and add a couple of examples to the list. Can you draw a system diagram for any of these examples?

The positive feedback reinforces any change in whatever direction it goes. For that matter, it can be the reason for growth, and it can be the reason for decline and collapse. For example:

• Profits fall because investments fall, but investments fall because profits fall…
• The poorer people are, the harder it is for them to get an education. The less education they have, the harder for them to get out of poverty.

In the context of sustainability, positive feedbacks are classic de-stabilizers, often catering to short-term gains. Although called “positive”, ironically, these feedbacks can be responsible for “runaway” and “snowballing” effects, throwing the system out of balance and often leading to crisis, especially when system growth starts to push against system boundaries.

Negative feedbacks

Consider this example. The population of deer in the area leads to a higher rate of road collisions. The collisions kill a certain number of deer, thus reducing its population. Once the population of deer goes down, the road collisions become less frequent.

Figure 1.13. Negative feedback loop consisting of two stocks and positive and negative couplings.

Credit: Mark Fedkin

We can still clearly see here how the result of the first positive coupling affects the initial stock. Such a feedback loop is called negative or balancing feedback (here is the “—“ sign inside the loop), because it does not allow the deer population to grow out of control. Of course, it is a simplified example, and in reality, there may be other ways of regulating the deer population (e.g. hunting) and minimizing collisions (e.g. fences, driver alerts).

Negative feedbacks are mechanisms of stability. They work both ways, not allowing the stock to go too low or too high. These feedbacks are very common in the natural world, where many systems are homeostatic. Some more examples:

• Warmer weather induces more evaporation from rivers and lakes, thus creating clouds, which cool the air temperature. Once the temperature is cooler, evaporation is reduced, thus resulting in fewer clouds and a sunnier sky.
• Carbon dioxide concentration in the atmosphere stimulates plant growth. More plants consume carbon dioxide from the atmosphere due to photosynthesis. Thus, bringing its concentration down.
• Market price variation: if any product becomes of very high demand, its price grows until the supply meets the demand. If the price rises too high, fewer customers would buy it, so the price would go down again.
• An office worker has to work, but feels sleepy, so he may drink some coffee to get his energy up. But drinking too much coffee can cause some health effects from too much caffeine, and he may decide to limit his coffee consumption. Here, the human decision to drink or not to drink coffee attempts to bring the energy level to the optimal level.

Now think and add a couple of examples to the list. Can you draw a system diagram for any of these examples?

When considering system resilience - the ability to bounce back from disturbances – look for negative feedback loops. Negative feedbacks are also culprits of resistance to change. Sometimes, changing undesirable existing practices is difficult because of feedbacks acting within the system.

How to determine the sign of feedback

Here is the rule of thumb for determining whether a feedback loop is positive or negative: combine signs of all couplings involved in the loops. For example: a loop of 2 positive couplings results in a positive loop:

$$( + 1 ) ( + 1 ) = ( + 1 )$$

A loop of 1 negative and 1 positive coupling results in a negative loop:

$$( + 1 ) ( - 1 ) = ( - 1 )$$

This is the same rule that we use in math when multiplying negative and positive numbers. If you count an odd number of negative couplings in the closed loop, the feedback is negative. If you count an even number of negative couplings in the loop, the feedback is positive.

This rule becomes especially useful when you analyze the feedback loops consisting of multiple couplings. Let us check out a couple of examples.

Examples of how feedbacks work in systems

Example 1: Albedo feedback in climate science.

Here we will consider the connections between four natural elements: solar energy absorbed by the Earth, atmospheric temperature, polar ice, and Earth albedo (reflective ability) (Figure 1.14). Polar ice caps play an important role in controlling the amount of solar energy obtained by the Earth. Due to the high reflective ability of ice, overall Earth’s albedo increases with the expansion of polar ice and decreases when ice melts. Here is the positive coupling between polar ice and albedo. When albedo is high, a large fraction of solar radiation is reflected back to space and is not absorbed by the Earth. Therefore, we can draw a negative coupling arrow from albedo to solar energy absorbed by the Earth’s surface. Next, we will establish the positive coupling between the solar absorption and surface temperature. The more energy is absorbed by the earth’s surface, the more heat will be emitted off the ground into the atmosphere, thus raising the atmospheric air temperature. Finally, higher global air temperature will result in a decline in polar caps by causing ice to melt – hence the negative coupling arrow to close the loop of connections. We have a feedback in the system!

Figure 1.14. System diagram for albedo feedback loop.

Credit: Mark Fedkin

To decide whether this feedback loop is negative or positive, we need to count all couplings involved:

$$( + 1 ) ( - 1 ) ( + 1 ) ( - 1 ) = ( + 1 ) \text{ this is a positive feedback! }$$

What does it mean, and what development can we expect from this system?

As we previously learned, positive feedbacks are destabilizing forces, which often lead to the accelerated shift of system from its current state. Indeed, the currently observed rise in global atmospheric temperature (global warming) is responsible for shrinking the polar ice caps. The fast decline in polar ice is observed in both poles and Greenland. This change gradually decreases the Earth’s albedo, and that makes the planetary surface absorb more solar radiation, thus pushing the atmospheric temperature further up. That secondary warming causes more ice melting etc. The more this process continues, the more warming is intensified, and the faster ice melts.

There is strong scientific evidence that the cause of the currently observed global temperature rise is anthropogenic CO2 emissions. And albedo feedback is an additional amplifier that can act fast and push the warming to much higher rates than CO2 alone.

This positive feedback can work in reverse as well. In the history of the Earth, the albedo feedback played a big role in establishing the “ice ages” on Earth, which were accompanied by very fast expansion of glaciers (polar caps) towards the continents.

Example 2: Fish Pond

This example presents a much smaller system that is a very typical example of ecosystem that has reaching its carrying capacity. Imagine a small pond with a certain population of fish in it. To survive, the fish needs some food and oxygen in the water. The stock of fish is regulated by the factors such as reproduction rate and death rate. Let us identify some key couplings:

• Reproduction rate is positively coupled with the number of fish. The higher the reproduction rate, the high the fish population
• Death rate is negatively coupled with the number of fish. The high the death rate (for any reason, e.g. environmental conditions, disease, predators), the lower the fish population

We can depict these relationships in the system notation as follows:

Figure 1.15. Reproduction rate and death rate of fish.

Credit: Mark Fedkin

• Food availability in the pond favors fish growth and reproduction rate. So this is a positive coupling.
• In a finite-size system like a pond, the food supply can be limited, so if it is too low to support all the fish, fish will starve and die. Hence we can assume the negative coupling with the death rate

Let us add it to the diagram:

Figure 1.16. Reproduction rate, food availability, and death rate of fish.

Credit: Mark Fedkin

• The same as with food, oxygen supply is important for fish population health and growth – this is another positive coupling.
• The limited oxygen supply due to any factors (e.g., eutrophication, overpopulation, etc.) will stress the fish, limits its reproduction, and possibly increase the death rate as well – this another negative coupling.

Figure 1.17. Factors impacting fish longevity

Credit: Mark Fedkin

There are a couple more important arrows to add:

• The more fish are there in the pond, the less food remains available (food is not unlimited). This is the same situation as we have in any ecosystem, including humans – you need more and more food to feed a larger population. So we will draw a negative coupling between Fish and Food availability.
• The more fish are there, the less oxygen is available. While the atmosphere can be considered unlimited compared to the size of the pond, oxygen has a limited and quite low solubility in water. Fish will consume it by breathing, but also dead fish decomposition will consume some of it. So there is definitely a negative coupling between the Fish and Oxygen.

Putting these final two connections onto the diagram, we obtain:

Figure 1.18. Factors impacting fish longevity

Credit: Mark Fedkin

Now let us identify the feedbacks. Are there any closed loops in the diagram? To have a complete feedback, we must be able to trace the couplings in one direction.

Now let us determine whether each feedback is negative or positive using the rule of thumb explained in the previous sections. For example, for the upper left loop, starting with Fish, we have:

$$( - 1 ) ( + 1 ) ( + 1 ) = ( - 1 ) \text{ It is a negative feedback! }$$

We can do the same to identify the other three loops in the diagram:

Figure 1.19. System diagram for Fish Pond system with four negative feedback loops (colored circles). Multiplication rule of thumb is shown for each loop to determine the feedback sign.

Credit: Mark Fedkin

This system appears to be full of negative feedbacks, and that is quite common for natural ecosystems. There are many regulating factors that keep the population of biological species in check. Once the system starts growing out of its capacity limits (food, oxygen supply), the feedbacks start dialing the numbers down until the optimum state (homeostasis) is restored. This example is a demonstration of how negative feedbacks tend to maintain the stability of the system at a certain level. Here we have as many as four mechanisms that help the system execute this goal.

Feedback loops with human decisions

The beauty and power of the system approach is that it can help explore inter-domain connections. Many systems currently exist at the interface of the natural and technological worlds and hence can include factors of economic, social, and environmental nature.

Many causal connections in the environmental systems are sort of predetermined and dependent on the laws of nature. For instance, if temperature increases, gas solubility in water decreases. If a ton of coal is burned, a certain amount of heat is released. If the ocean becomes more acidic, carbonate shells do not form. Those things are just physics and chemistry – there is no intelligent ruling behind them. However, causal connections may be different in human systems, because very often humans have a choice: to turn left or right; to approve or reject a policy; to invest or not to invest; to start the war or negotiation. Those decisions can make an impact within the system, but it does not mean they control the system. In fact, some intelligent (or dumb) decisions can very much be a product of system behavior. In other words, people may take decisions without realizing that they are being controlled by the system itself!

We mentioned before that one of the important system’s properties is function or purpose. The word purpose is more linked to human thinking, so systems can be created to fulfill a particular purpose. The word function is more typical for non-human systems, and function is often visible from the system’s behavior. Please note that human decisions can be made with a purpose in mind, but that purpose in the mind of an individual (perceived or apparent purpose) does not necessarily coincide with the purpose of the system (actual purpose). This is an important distinction. Here are some examples of such dual-purpose dilemma:

• A musician may initially perceive their career in the music industry as art and a way of self-expression (perceived purpose), but the system may steer them towards songs that gain most popularity and make the most money (actual purpose);
• A parent chooses to punish their child for bad grades with the purpose to make them work harder and to improve learning (perceived purpose), but punishment may cause the child to hide their grades or cheat for the sake of a better grade (actual purpose);
• Cat meows loudly in the middle of the night to demand food from the owner. The owner gives the cat the food so that it let her sleep. But guess what – the cat comes back to meow every night now! Perceived purpose = keep the owner happy, actual purpose = keep the cat happy.

Understanding the system behavior can actually help us make smart decisions and steer the system purpose in the desired direction, even those decisions are not always intuitive.

Example 3: Honey Bee Hive

There are a number of environmental factors that sustain the purpose of the honey beehive. It needs a specific habitat with natural flora that provides bees with sources of nectar, clean air and water, which sustain vegetation. Human activities, such as agriculture using pesticides, industrial development, and water and air pollution can be highly disruptive to honey bee populations. We will try to put those factors onto the system diagram (Figure 1.20).

You can identify the positive feedback in this system, which is responsible for ecosystem growth under healthy environmental conditions, with bees and plants mutually benefitting each other. The anthropogenic (human activity) factors, shown by shaded circles, are negatively coupled with different factors in the system. We know that when a positive feedback exists in the system, it can work both ways. A drastic decrease in any of the factors in the loop can result in a fast decline of the entire system.

Figure 1.20. System diagram for the honey beehive system. The anthropogenic factors (shown by shaded circles) negatively impact the bee population directly and by undermining the key stocks: flora and clean air.

Credit: Mark Fedkin

Human decisions can interfere. For example, a decline in the main stock – honey bee population - below a certain critical level can be an alarm signal for the local conservation agencies, who can work with policy makers to protect the natural habitat and resources from excessive exploitation or pollution. That additional factor, when introduced to the system, creates several negative feedback loops that forcefully regulate the industrial factors and keep the system in balance (Figure 1.21).

Credit: Mark Fedkin

Sustainability in system thinking

So, what would make the system like the ones exemplified above sustainable? A simple answer within the arbitrarily identified boundaries would be: the balance of the main stocks. The balance does not mean constancy, but rather refers to a range where system can recover from stock fluctuations through internal mechanisms. We already saw how stocks can be regulated by feedback loops that involve both physical forces (natural laws) and intellectual forces (human decisions). Here, we come to an important observation: human decisions need to conform with the natural processes. Natural and human forces must work with each other, not against each other, to support the capacity of the life-providing stocks. This takes us back to the first Hanover Principle of sustainable design. Systems thinking brings us to the right mindset for applying sustainability principles to a variety of case studies we will discuss in the remainder of this course. To extend your learning of the systems approach, you can refer to the additional reading materials:

Growth

Since this lesson has some analysis and discussions of growth, it would be interesting to see how growth happens in system dynamics. Two types of growth we want to pay attention to are linear and exponential. Linear growth is when a value grows at a constant rate (slope). Positive couplings in systems are a usual cause of linear growth. For example, more product sold means higher profit; more fuel burned, more energy is released – those are simple observations. Exponential growth is different – it goes at an increasing rate – it accelerates! Systems with positive feedback loops often exhibit exponential growth, because the initial stock is continuously compounded by the positive couplings included in the loop.

Mathematically, these two types are schematically represented in Figure 1.22.

Figure 1.22. Graphic and mathematical representation of linear (left) and exponential (right) growth.

Credit: Mark Fedkin

One of the examples shown in the previous section was about the bank account with interest. Adding interest to your balance increases the initial stock and thus earns you higher interest. This illustrates how a positive feedback works. Another example is population growth. When unhindered, the positive feedback loops are expected to cause exponential changes in system stocks.

Example: How to Use Exponential Formula

$$\mathrm{f} ( \mathrm{x} ) = a b^{\mathrm{x} }$$

This mathematical expression generically represents an exponential process. In this formula:

f(x) is a function – the amount we try to track over time. In the case of a bank account, it will be the account balance, or in case of population growth - the number of chickens, bacteria, or people.

a is the initial value, e.g., the account balance to start from or starting population of species.

b is the base, which indicates the factor by which the initial amount changes per unit of time. For example, if the number of bacteria doubles every hour, b=2. Or if the bank account grows by 6% every year, b=1.06.

x is an exponent, which acts essentially as a time coordinate. For example, if you try to calculate the function for 10 hours ahead, x=10.

Starting with 1 bacteria (a=1) and hourly doubling increase (b=2), in 10 hours we will have $f ( x ) = 1 \times 2^{10 }= 1024$ bacteria.

Figure 1.23. Exponential growth with doubling rate.

Credit: Mark Fedkin

From the above examples, we can make a few interesting observations:

• Exponential growth starts slow, but it becomes fast very fast.
• The result of exponential growth is very hard to predict intuitively because we are used to thinking linearly
• Very often, exponential growth is the result of positive feedback in the system
• Negative (balancing) feedbacks are one way to limit system growth
• Exponential growth cannot be sustainable within a finite-size system and reaching capacity crisis is only a matter of time.

Delays

When we discussed couplings in systems, we mentioned that such causal connections exist when A affects B in either a positive or negative way, but we did not pay much attention to how fast that happens. Some changes can be almost instantaneous (or at least seem like that). For example, clouds moving across the sky immediately change the flow of solar energy coming down to earth, and suddenly we feel cooler, or if the sunlight is used for electric generation, the voltage of the solar panel quickly drops. But other changes may take minutes, hours, days, years, and even millennia. That essentially means we have a delay between the cause and its effect.

Examples of systemic delays are multiple. Here are just a few:

• Incubational period of a viral disease – time between virus entering the body and symptoms
• Forest growth – time between seeds germinate in the soil and trees reaching a certain height;
• Greenhouse effect in climate – time between atmospheric carbon dioxide concentration increase and global temperature increase
• Prices in the market – time between supply or demand grow and decision to adjust the price for a product.

The larger the system, the greater the volume of the stock, the longer it takes for it to respond to change. That is why planetary system often experiences changes (climate, ocean chemistry, geochemical cycles) with significant delays - at the scale of thousands and millions of years. That is why technological, economical, and cultural changes often happen much faster at the community level than at the national level.

Delays are important to take into account in system analysis, since they impact system behavior and resilience. Delays in every coupling in the negative feedback loop would add up, thus postponing system response to perturbation. When uncompensated, the perturbation lasts longer, pulling system further off balance.

One of the favorite examples of systemic delay is shower. Have you ever experienced this situation: the water feels too cold and you adjust the hot water knob to make it warmer, but nothing happens, so you adjust it even more, and a little bit more… and then you feel it! It finally gets warmer, but soon enough it feels too hot, and you jump aside and start adjusting the knob in the opposite direction. It takes quite a bit before it is comfortable to stand under water again, but once you think you finally got it, water gets too cold again, and the fine-tuning continues..

We can also depict this process in a system diagram if you wish:

Figure 1.24. Shower system diagram with water regulation feedbacks. Coldness of water draws down the comfort level and prompts the responder to adjust the knob to increase the hotness of water, which is supposed to bring the comfort level to optimal. There are two negative feedback loops that help stabilize the system. However, the delay in the couplings between the knob adjustment and actual hotness of water felt by the person (shown by red marks) results in the adjustments being disproportional with the anticipated temperature change.

Credit: Mark Fedkin

In this process, the temperature of water goes up and down, only bypassing the optimal comfort temperature, resulting in oscillation. Eventually, understanding the delay, you start being more patient, wait for the change and make smaller adjustments. With a few more overshoots, you finally reach the optimal temperature. The system is stabilized!

Why are you able to stabilize the system eventually? In the process of regulating water temperature, you learn – you get information about how long the delay is between the knob turn and actual water temperature change. You also learn how much the temperature changes per certain degree of knob turning. Of course, you process this information almost subconsciously, and it takes a little bit of trial and error.

Figure 1.25. Common oscillation pattern for a parameter observed in systems that are regulated by negative feedbacks with delays.

Credit: Mark Fedkin

Many other systems with negative feedbacks – for instance, regulation of inventory stock based on supply and demand, regulation of earth climate by biota – may exhibit similar oscillations that complicate the system behavior.

Very often, regulating the system operation to improve its performance comes down to managing its delays. Interestingly, acting fast in the system with delays may only exacerbate the situation and make negative impacts and further delays even more dramatic. Instead, understanding delays and letting them run their course may be a better strategy to optimize system performance [Eakes, 2018].

Tipping points

Tipping points is another interesting phenomenon that occurs in some systems. This topic can certainly be a subject for a deeper discussion, but it is worth mentioning it here at least briefly.

Tipping point is a special condition in a system, at which a very small perturbation or causes a large or even catastrophic change. Obviously, the small change is not the main cause, but only a trigger, the last drop in a long and sometimes complicated chain of interactions and events that lead the system to this condition. The term “tipping point” originated in the mathematical catastrophe theory and only recently started to be used in the global environmental context. Most frequently, tipping points are investigated in the relation to climate science and ecology.

Tipping points are frightening because they are not easily predictable, and when the tipping events are triggered, there is no way to reverse the process. Also the events that occur when a system passes through a tipping point are usually dramatic, proceed at a high rate, and have no forewarning. Therefore, understanding the nature and the actual causes behind the tipping points is important for designing preventive measures. Tipping points are very characteristic of systems with counteracting negative and positive feedbacks.

If you are compelled to read more about this concept, additional explanations and some good examples are given in the following reading:

It should be understood that tipping points are not results of external forces, which can also cause dramatic shifts and catastrophes, but are rather internally justified. Another take-away is that, like any other systemic phenomena, tipping points can happen in both natural and social worlds – they are not only confined to the physical processes. Tipping points are observed in societal systems and can be marked by major paradigm shifts, dramatic changes in thinking, decision making, and political transformations. It is very possible that passing of the human society from the current state to a new state with a higher degree of sustainability may also require passing through a tipping point when some traditional worldviews are rejected, and new ones are adopted. Hence, the tipping points do not only present risks, but also opportunities in socio-economic evolution.

Boundaries and system hierarchy

It should be noted that any system model is always a simplification, and system analysis has to be iterative to identify the most significant controls and relationships that determine system operation and stability. Although limited, system analysis can provide interesting insights into system behavior, helps understand the trends in social and technological development, and provides grounds for short-term and long-term predictions.

While real systems are often complicated, making the system model overly complex is not practical - it is important to set boundaries, which would help constrain the analysis and provide answers to practical questions. Boundaries are defined by the observer. Boundaries do not mean that the system is isolated from the outer world, they simply set limits; any entities beyond system boundaries are assumed to be of minor relevance and are not examined in detail until the current model requires. For example, in the honeybee hive system described earlier, we do not consider the factor of climate, even though it is important. In the short term analysis, we simply assume it is constant. Also, we do not include economic factors such as the honey market or artificial beekeeping, etc., leaving them outside the system boundaries and just focusing on the health of the natural ecosystem.

Virtually any system is a hierarchy. That means that any system consists of smaller subsystems, and any system, in turn, may be considered as an element of a bigger system. The tree itself is a system; the soil bed is a system; any biological organism is a system with its own control factors. At the same time, the forest can be considered as a sub-system of eco-region, which is, in turn, may be perceived as a sub-system of the planet, etc. This is another reason for setting boundaries and choosing system scale before engaging in system analysis.

Global sustainability system

To set the framework for applying sustainability principles to engineering activities and technologies, let us for a while widen the angle of our view and first look at the global interconnections. Later on, when zooming in to particular processes and technologies, some of these global elements and loops may remain beyond the boundaries of our viewfinder. However, it will be important to keep these large-scale connections in mind.

Figure 1.26. Sustainability framework for engineering.

Credit: Gagnon et al. Sustainable development in engineering: a review of principles and definition of a conceptual framework, November 2008. Gagnon et al.

The scheme in Figure 1.26 includes both physical and social systems in consideration. Physical systems are shown by several overlapping spheres in the upper part of the diagram: the first one is biosphere (which includes the aquatic and terrestrial ecosystems), the second one is the anthroposphere (which encompasses the agricultural, industrial, and urban systems); both of these are positioned at the triple boundary between the atmosphere, lithosphere, and hydrosphere of the earth. The sun symbol above indicates the unlimited light resource. We can expand the anthroposphere box, indicating the significant role played by engineering projects as human activity. Design and engineering result in creation of products, infrastructures, processes, and services, which all increase the extent and influence of the technical cycle. The Engineering Projects box is linked to Individuals box, meaning that technical progress is incurred by and benefits individuals in the social sphere. The feedback we can assume here is possible disturbance of the natural systems due to expansion of the anthropogenic technical systems. This expansion, in turn, can jeopardize the benefits human beings and societies derive from the environment. Individuals are given a central place in the framework since physical and social systems both contribute towards their well-being. The Social Systems box at the bottom of the diagram provides a more detailed representation of those benefits, which include economic, political, scientific, legal, educational values and communications. Shown social sub-systems, such as Families, Communities, Networks, and Organizations, interact to a various degree with the main social systems and fulfill certain functions. This framework diagram is very broad, and each box could be presented as a separate sub-system with its own internal connections. But this is the big picture, which allows us to contemplate on the diversity of the factors that contribute to the sustainability of human society.

Now, think where technology fits into this diagram. Virtually, it fits anywhere at the connections of the anthropogenic spheres with the physical systems. For example, through technologies, society can utilize natural resources. We also understand that technologies can do both: reconcile the processes and matter flows between the anthroposphere and environmental spheres and create conflicts between them. Thus, engineering projects undermining the resilience or adaptability of ecosystems, social systems, or individuals might bring benefits in the short term but are likely to have long-term negative outcomes. What we call sustainable technologies are designed to render the feedbacks and connections mutually harmless or mutually beneficial in the best-case scenario. To assess technologies from this angle, we need to learn to recognize the feedbacks and effects they create on a large scale.

Lesson #1 started introducing you to the sustainability context, reviewing the main philosophical principles of sustainability as well as practical guidelines applied to sustainable design and engineering. From these philosophies, we can clearly see that any analysis of engineering projects, technologies, and processes from the standpoint of sustainable development must be done in a wider framework, which includes environmental, economic, and social forces.

Here, we also browsed through the important background of systems approach, which emphasizes interconnections and feedbacks as controls of system stability or instability. Based on this review, we started to determine the role of technology in the dynamics and function of anthropogenic systems. We can see that technologies work at interfaces between the physical world and society. Technologies can be efficient tools regulating the system inputs and outputs, and also can serve as drivers of change and lifestyle builders in society. This prepares us for the next step – developing the metric system and methods for technology evaluation in the next lessons.

Assignments for Lesson 1

References for Lesson 1:

In this lesson, we will discuss the role of technology in society and how it develops on its way to commercialization. You will review the technology readiness level (TRL) scale adopted by a number of government agencies and see what kind of information is needed to estimate it. This lesson also sets the background for using the life cycle assessment methodology (LCA), which allows us to view a bigger picture of a technological process, with its multiple pros and cons and impacts on other parts of a sustainability system. Life cycle assessment is a complex approach, which requires extensive data digging and process expertise. While you will not be asked to perform the complete analysis on your own, some LCA-related exercises in this lesson will help you develop a big-picture mindset about technologies and products. Both TRL and LCA assessment methodologies will be useful in your individual course project, so take notes of the resources provided on those topics.

Learning Objectives

By the end of this lesson, you should be able to:

• explain the role of technology in society and in feedback loops of anthropogenic systems;
• articulate the technology readiness levels and identify the data needed for TRL analysis;
• apply the fundamentals of the life cycle assessment (LCA) and draw LCA scope and flow diagrams.

Readings

Journal article: J.B. Guinee et al., Life Cycle Assessment: Past, Present, and Future, Environ. Sci. Technol., 2011, 45, 90-96. (see Canvas)

US EPA Document: Life Cycle Assessment: Principles and Practice, EPA/600/R-06/060, 2006.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

How do we define technology? In this course, specifically, we need to look at a particular technology, process, or product as an active part (component) of an anthropogenic system. In such context, a technology is not simply a piece of human knowledge implemented through design and engineering principles, it is considered a "living" part of a bigger organism. Here, we use the word "living" because our interest will be to assess the entire lifecycle of a technology: development, adaptation, operation, interactions with natural and technical environment, aging, and death (in some cases). Further on, we will try to understand how technology development impacts the viability of the whole system.

The common definition of the term technology is quite broad and multi-colored. The most simplistic one is application of scientific knowledge for practical purpose. And as an extension of it, the tool or device enabling that application is typically also referred to as technology. You can read more on the history and usage of this term in a Wikipedia article on Technology. You may recognize that the meaning strongly depends on the context and the professional area you are in. However, in this course, we need to distill this broad perception of technology to a more specific entity that can be used for practical analysis.

Energy and matter conversion

The most important ability of almost any technology is conversion. A technology uses inputs of energy or matter to create outputs of energy or matter of a different quality. In a general case, any technology can be represented by the following scheme (Figure 2.1):

Figure 2.1. Energy and matter conversion defined as a function of technology.

Credit: Mark Fedkin

So, technology typically serves as a conversion portal in a system. We use energy to produce materials; or use raw materials to produce some more complex products; or we use matter to convert forms energy; etc. Note that conversion can also be performed by natural systems or mechanisms; but we only define technology as a human-made conversion system.

Here are some simple examples:

• Chemical energy of fuel >>> Car >>> Kinetic energy of car motion
• Radiative energy (sunlight) >>> Solar panel >>> Electric energy
• Electric energy >>> Phone >>> Sound, light
• Contaminated water >>> Water treatment plant >>> Clean water
• Electric energy >>> Furnace >>> Thermal energy
• Flour, water >>> Baking machine >>> Bread
• Organic waste >>> Composting >>> Fertilizer
• Electricity, mechanical energy >>> Electric guitar >>> sound

You can continue this list.

Self-Check

See if you can identify the energy and matter inputs and outputs for the following technologies:

•   ?       >>> Coffee maker >>>     ?
•  ?       >>>  Battery  >>>>           ?
•  ?       >>>  Loud speaker >>>    ?
•  ?       >>>  Microwave >>>         ? 

ANSWER

• Water, ground coffee, electricity  >>>  Coffee maker  >>>  Coffee Drink
• Chemical energy  >>>  Battery  >>>>  Electricity   (upon discharge)
• Electricity  >>>  Loud speaker >>>  Sound
• Electricity    >>>  Microwave >>>   Microwave radiation, kinetic energy (rotation) 

Conversion efficiency

Obviously some technologies are better converters than others, and the following metric allows us to compare different technological options and choose a "better deal" in terms of useful output and money spent.

The key characteristic of any conversion process is efficiency. Efficiency is estimated based on the amount of useful output per unit input. In that sense, it is a subjective value which depends on a particular goal or purpose of a technological process, and a particular input resource we are concerned about. Hence, efficiency has widely varying meanings in different disciplines.

For example, efficiency is a very common metric in the field of energy conversion. According to the energy conservation law, the total energy entering a conversion device should be equal to the total energy output by the device:

E_in = E_out

Some of the output energy can be considered useful (based on the purpose of conversion), and some of it can be considered not useful and attributed to "losses":

E_out = E_out(useful) + E_out(loss)

What is useful and what is not is up to us to define (nature does not care!).

So, efficiency determines the fraction of the useful energy as follows:

Efficiency = E_out(useful) / E_in × 100%

Efficiency is important in the sustainability context because it indicates how much of the resource is put to work, and how much of the resource is wasted in the process. The reasons for losses are process dependent and should be analyzed specifically for each application. A big part of the technological research is aimed at increasing efficiency of the conversion process via minimizing losses.

Example 1

A typical incandescent light bulb outputs both light and heat. If you ever touched the working light bulb with a bare hand, you know that there is a good amount of heat generated in this kind of energy conversion.

If I use the bulb to lit my dining area, the useful energy I collect is obviously light, or radiant energy, and efficiency of the conversion process would be defined as:

Efficiency = (Light Output / Electricity Input) x 100%

But if I use the bulb to warm my home incubator (with eggs waiting to hatch), the useful energy in this case would be heat. And the generated light would be in fact , unnecessary; that is not useful output. In this case the efficiency of the conversion process can be defined as:

Efficiency = (Heat Output / Electricity Input) x 100%

Here we can see that efficiency is often defined in the eye of the beholder.

By the way, the efficiency of the incandescent bulb in the first case is much lower than in the second. Conversion to light is on the average 2.2% efficient, while the rest of input energy (97.8%) goes into heat.

Example 2

As another illustration of how this concept works, let us estimate the efficiency of a photovoltaic panel. Photovoltaic technology converts visible solar radiation (energy-in) into electric power (energy-out). So, for this estimation, we need to know or measure these two quantities.

Let us assume that the efficiency is measured in the middle of a sunny day, and the panel is installed perpendicular to the incident rays. Under those conditions, the typical incident radiation flux is ~1000 W/m². We can take this number as the measure of energy-in per unit of time.

Now, let us assume that the panel outputs the power density 120 W/m². Usually, this value can be obtained by measuring the voltage and current density of the panel (power = voltage x current).

Then, the efficiency value can be calculated as follows:

Efficiency = E_out(useful)/E_in × 100% = 120 W/m² / 1000 W/m² × 100% = 12%

This value means that 88% of total solar energy reaching the panel is lost, and only 12% is converted to electricity due to technology limitations or environmental factors. Just FYI, the nominal efficiency of most solar panels on market ranges between 15 and 22% (under ideal conditions). As you can see, efficiency estimations require data on technical performance of the system, so we will be paying attention to how performance of different technologies can be measured and interpreted.

Table 2.1 lists some known efficiencies of various energy technologies for comparison. These are just a few examples to demonstrate the variety of converters. We should note that generally efficiency of a process or technology is not necessarily measured in terms of energy. If the useful output of the converting technology is, for example, some form of matter (e.g., water electrolyzer in this table), the calculation can be made in terms of mass. Sometimes, efficiency analysis is also used to estimate the maximum theoretical efficiency, which cannot be practically exceeded due to inherent physicochemical limitation of the system. Finding maximum theoretical efficiency requires detailed knowledge of how the process works and what unavoidable losses occur in conversion.

Table 2.1. Efficiencies of some energy conversion processes and technologies. Note: Values for a specific system may vary due to operational conditions and component development. [Source: Wikipedia]

Process or Technology	Input	Useful Output	Conversion efficiency
Gas turbine	Gas flow	Electricity	40%
Water turbine	Water flow	Electricity	90%
Solar cell	Light	Electricity	15-40%
Fuel cell	H2(gas), O2(gas)	Electricity	up to 85%
Water electrolyzer	Electricity	H2(gas), O2(gas)	50-70%
Combustion engine	Fuel (gasoline)	Motion (kinetic energy)	10-50%
Geothermal electric plant	Heat	Electricity	10-23%
Solar thermoelectric generator	Sun radiation	Electricity	15%
Electric motor	Electricity	Motion (kinetic energy)	30-90%
Electric heater	Electricity	Heat	up to 100%
Refrigerator	Electricity	Negative heat	20-40%
Fluorescent lamp	Electricity	Light	8-15%
Photosynthesis	Light	Biomass, O2(gas)	3-6%
Muscle	Metabolic energy	Kinetic energy	18-25%

Probing Question

Can energy conversion efficiency be more than 100%? Click on answer below.

YES

Incorrect: (Efficiency above 100% would mean that energy output of a system is greater than energy input. This contradicts the law of energy conservation.

NO

Correct! Output cannot be greater than the input according to the energy conservation law.

Yes, but only in an ideal zero-loss system

Incorrect! Zero losses would mean 100% efficiency, but not higher.

Probing Question

Can you calculate the efficiency of an electric motor that consumes 150 W of electrical power and produces 120 W of mechanical power? Click on answer below.

8%

Try again - divide the useful output of the system by total energy input.

65%

Try again - divide the useful output of the system by total energy input.

80%

Correct! Dividing 120/150 = 0.8 (i.e. 80%)

125%

Efficiency cannot theoretically go above 100%.

Technology Adaptation

To become part of society life, technology needs to be adapted. Not all technologies invented go through successful adaptation, and there are several critical barriers that need to be overcome in order to create a working interface between technology and society.

Figure 2.2. Technology adaptation stages

Credit: Mark Fedkin

Consider the following stages of technology adaptation:

1. Technical Adaptation. Research and development, design, and demonstration. (yellow)
2. Adaptation to the natural environment: matter and energy exchange, use of resources, and absorption of the impact (green).
3. Adaptation to the technical environment: development of infrastructure and supporting technologies (brown).
4. Market Adaptation. Development of economic algorithm. Proof of profit and long-term feasibility (peach).
5. Social Adaptation. Acceptance by target society groups, based on ethical, environmental, cultural, and economic considerations (blue).

The first three stages of adaptation can be reflected in more detail through the Technology Readiness Level scale (TRL) on page 2.2 of this lesson. The fourth stage of adaptation is closely related to economic assessment, which should answer the question if the technology can support itself and make a profit in the short term or in the long term. Finally, the fifth stage of adaptation includes multiple social factors - how ready consumers are to accept this new technology, and what social benefits it promises (for example, higher standard of living, job creation, convenience, faster service, improved health, etc.). The sustainability analysis should be comprehensive enough to cover all of these layers of adaptation and recognize connections and feedbacks between them.

Technology readiness assessment is a systematic, metrics-based process that evaluates the maturity of, and the risk associated with, critical technologies under development. It is a commonly accepted approach used in a number of industry and government organizations to assess the maturity of a technology (e.g., device, material, component, process, etc.) on an entire scale - from its invention to commercialization and wide-scale application. TRL rating actually determines how far a particular technology is from being deployed by industry or public. That, in turn, determines the amount of resources - time, funds, intellectual potential, facilities, etc., - necessary to bring this technology to life. We can illustrate the term 'readiness' with a simple example like the one below.

There are many other examples of technology going through many years of adaptation prior to reaching its broad applicability. What you see in the left-side image below may seem like a hardly recognizable mechanical device. What is on the right side is its contemporary version. The first computer mouse prototype was invented in 1964 by Douglas Engelbart of Stanford Research Institute. The mouse device remained an subject for further development, modifications, demos, and pilot projects for two decades before it was finally adapted for broader use with the personal computer Mackintosh 128K in 1984 (Wikipedia)

Engelbart's first prototype of the computer mouse (1964) (left); modern look of the computer mouse (right). It took two decades for computer mouse to develop to reach the readiness level for broad adoption and use.

Credit:  SRI Computer Mouse by David Levy is licensed under CC Attribution-Share Alike 3.0 Unported

How do we evaluate the maturity or readiness of a particular technology?

Technology Readiness Level (TRL) scale was first employed by NASA in 1974 to evaluate the maturity of technologies for spacecraft design as part of risk assessment. It was demonstrated that transition of emerging technologies at lesser degrees of maturity results in higher overall risk.

Later, the TRL scale developed by NASA was also adopted in the U.S. by the Department of Defense (DOD), Department of Energy (DOE), Air Force, Oil and Gas Industry and also in Europe by the European Space Agency (ESA). The main rankings in the TRL method for technology readiness assessment are classified in the table below.

TRL approach proved to be useful as a tool for:

• general understanding of technology status;
• risk assessment and management;
• decision making with respect to technology funding;
• decision making with respect to technology transfer.

In the context of this course, it will be important to understand the technology readiness levels in order to properly assess the timeline and cost of its development and implementation. When applied to a particular technology, the above listed TRL ranks should be customized for better relevance. Such customization would identify specific milestones as criteria to advance to the next level.

Assigning a TRL rank is not a quick task. These are some serious questions that need to be answered and backed by technical data regarding the current status of technology:

• Is technology widely commercialized?
• Is technology demonstrated in the final form (in a target system)?
• Is technology demonstration in the relevant environment (field conditions)?
• What is the target performance / efficiency level (technically and economically)?
• What is currently achieved performance / efficiency?
• What are the materials involved and what is their availability?
• Is infrastructure available for deployment for this technology?
• What are the main barriers impeding the higher performance? … etc.

You can see that determining the status of technology development often requires search and knowledge of most recent advances, publications, and news releases on the technical performance, demonstration, pilot systems, and prototypes. It also requires independent expertise in subject matter along with understanding the economic criteria, which establish a threshold where the technology becomes economically feasible and is able to compete with existing alternatives.

What kind of data sources can you use for TRL analysis?

• Scientific publications in refereed journals
• Government agency reports
• Company news releases (may withhold technical details that are proprietary)
• Public news, web blogs, ads (secondary sources which may refer you to original information)
• Personal communications with experts, researchers, and entrepreneurs 

I hope you found content on this page useful. Different assignments in this course will tap into the TRL concept repeatedly, and you will be asked to either estimate the TRL ranking or provide some analysis of technology readiness and maturity in your course project.

Additional Resources on Technology Readiness Levels:

• NASA, Technology Readiness Levels Demystified, 2010, URL: https://www.nasa.gov/topics/aeronautics/features/trl_demystified.html
• Disruptive Innovation, Technology Readiness Level (TRL) - Innovation Management, 2016, Youtube Video URL: https://www.youtube.com/watch?v=in4TnQZGYj4

Emerging technologies are technical innovations that breach new territory in a particular field. Over centuries, innovative technologies were developed and opened up new avenues for lifestyle and market transformation. Implementation of an emerging technology involves economic risk, but, if successful, offers a competitive advantage to a company. Some of the emerging technologies are developed via theoretical research, while others are based on commercial research and development.

Often emerging technologies are at the TRL levels 1-5 and require significant research, investment, and marketing to bring them to the commercial stage.

Here are some examples of emerging technologies at various stages of their development.

The following websites post news on emerging technologies and ideas. Check these out - there are a lot of exciting examples of how technological innovations enter society. You may find these resources useful for picking examples for your studies in this course (I keep adding to this list every year:):

• Top emerging technologies for 2013
• Top emerging technologies for 2014
• Top emerging technologies for 2015
• Top emerging technologies for 2016
• Top emerging technologies for 2017
• Top emerging technologies for 2018
• Top emerging technologies for 2019
• Top emerging technologies for 2020
• Top emerging technologies for 2021
• Top emerging technologies for 2022
• Top emerging technologies for 2023

Converging technologies develop from the convergence of different systems evolving towards similar goals. Convergence can refer to previously separate technologies, which create new efficiencies when combined together.

Some examples of technological convergence can be the blend of the mobile telephone and the Internet, design of hybrid vehicles, combination of movie and game industry, combination of nano- and macro-scale science in biology, agriculture, and material design, online education…

Unlike emerging technologies, converging technologies are not necessarily based on technical breakthroughs, but rather involve already developed and commercialized technologies to achieve a new level of performance, human ability, societal outcomes, the nation’s productivity, and the quality of life.

Disruptive technologies are innovations that help create new markets and eventually go on to disrupt an existing market and value networks, displacing an earlier technology. This term, coined by Harvard Business School professor Clayton M. Christensen, is often used in business and technology literature to describe innovations that improve a product or service in ways that the market does not expect.

For example, the automobile was a revolutionary technological innovation, but it was not a disruptive innovation, because early automobiles were expensive luxury items that did not disrupt the market for horse-drawn vehicles. The market for transportation essentially remained intact until the debut of the lower-priced Ford Model T in 1908. The mass-production of automobiles was a disruptive innovation because it changed the transportation market.

Check out this "Disruptive innovation" Wikipedia page which contains a list of some well-known examples of disruptive technologies. Many of these disruptions occurred within the past couple of decades, and we can relate to them. Disruptive innovations can change the way people live and work, re-arrange the values in markets, and lead to the creation of entirely new products and services. "The discovery and identification of disruptive technologies require the researcher to think like an innovator and entrepreneur in order to take full advantage of an “epiphany” moment, i.e., a moment in which you suddenly understand something in a new and potentially life-changing way. Such a moment, if properly acted upon, can accelerate your career toward recognition and long-term research funding." (KSRS, 2014)

Sustaining technology. As opposed to disruptive technology, sustaining technology relies on incremental improvements and innovations to an already established technology. Sustaining innovations or technologies do not create new markets but rather evolve existing ones with a better value, allowing the firms to compete against each other's sustaining improvements. Sustaining innovations may be discontinuous (i.e., transformational) or continuous (i.e., evolutionary).

Here, we also need to acknowledge the hierarchy of technologies. As we defined it above, technology is a human-designed system with a conversion function. At the same time, smaller parts of that system can be also considered technologies, and those can be represented as assemblies of even smaller components (sub-technologies). For example, a car may be considered a technology within a transportation system. However, smaller components within the car, such as the internal combustion engine, tire design, air conditioning, navigation, etc., are also technologies in principle. Should those be separately evaluated?

Our criterion for what level technology in this hierarchy we take for assessment is the role of the technology as a functioning element of the whole system. Our assessment targets are the systems (technologies) that can have a potentially disruptive impact on a bigger system, especially in the social and economic context. This is because progress towards sustainable development requires disruptions and seeks a shift in the existing paradigm. If technology is too subordinate to be responsible for disruption in a social and economic context, it’d be rather considered as a technical element supporting the main key technology.

Life Cycle Assessment (LCA) is a "cradle-to-grave" approach for evaluating products, materials, processes, services, and industrial systems with respect to their environmental impacts. Cradle-to-grave process begins with the extracting of raw materials from the earth to manufacture a product and ends at the point when all materials are returned to the earth in some form. LCA looks at all the stages of the product’s life one by one, estimates various environmental impacts at each stage and, as a result, allows selecting the path or processes that are least impactful based on chosen metrics.

LCA studies help decision-makers select the product, process, or technology that would be "least evil" in terms of its environment footprint, however the final judgment and interpretation of the results always depends on the key metrics and criteria that are most important to specific stakeholders. In that sense, LCA objectives should be set early in the analysis to answer the questions relevant to a particular project or application. Classic LCA deals primarily with environmental impacts, but further can be used with other pieces of information, such as cost and performance data, to find optimal solutions.

The diagram below illustrates the main lifecycle stages to be considered in LCA:

Figure 2.3: The main stages and typical inflows and outflows considered in lifecycle assessment.

Click to expand to provide more information

This diagram is based around a box-shaped system that includes four processes and is surrounded by a System Boundary. The four highlighted stages are:

• Raw Materials Acquisition
• Manufacturing
• Operation/Use/Maintenance
• Recycle/Waste Management

System Inputs are shown as arrows on the left of the system, outside the System Boundary. Inputs are represented by Raw Materials and Energy that flow into the system.

System Outputs shown as arrows on the right and at the bottom of the system, outside the System Boundary. Outputs are represented by Main Product and Co-Products (shown at the bottom), and Atmospheric Emissions, Waterborne Waste, and Solid Wastes (shown on the right).

Credit: Mark Fedkin

As you can see in the diagram above, any product or technology would require input of some raw materials and energy at all stages: from acquisition to manufacturing, operation, and finally disposal. All of the mentioned lifecycle stages may produce atmospheric emissions, waterborne and solid wastes, simply because the efficiency of material use and energy conversion is always below 100% - there are losses and by-products, which sometimes can be highly undesirable. LCA helps to keep track of all useful and harmful outcomes, and the diagram in Figure 2.3 provides a guideline to LCA mapping.

Procedure for Life Cycle Assessment

A standard LCA study would consist of several key steps outlined below:

1. Goal definition and scope: Identify a product / Set system boundaries / Develop LCA map and material flow chart.
2. Inventory analysis: Collect data / Identify and quantify energy, water, and materials as inputs and emissions as outputs.
3. Impact assessment: Set impact categories / Develop metrics / Perform calculations and comparative analysis.
4. Data interpretation: Relate metrics to objectives / Quantify human and ecological effects / Deliver information to target audience / Issue recommendations

The standardized procedure for the LCA recommended for product and technology assessment in the U.S. is documented in the EPA guidelines referred below. Study this document carefully – some parts of this framework will be used as a basis for technology evaluation repeatedly in this course's assignments.

In this Lesson, we are going to do an exercise on LCA scoping for a simple product. That would only cover Stage 1 of the entire process. Still, it is a very important step that sets the ground for the entire analysis and provides directions for collecting data and developing metrics during the Inventory Analysis and Impact Assessment stages of the LCA. Please refer to the Canvas Module 2 for specific directions on this assignment.

LCA Limitations

• LCA thoroughness and accuracy will depend on the availability of data; gathering of data can be problematic; hence a clear understanding of the uncertainty and assumptions is important.
• Classic LCA will not determine which product, process, or technology is the most cost-effective or top-performing; therefore, LCA needs to be combined with cost analysis, technical evaluation, and social metrics for comprehensive sustainability analysis.
• Unlike traditional risk assessment, LCA does not necessarily attempt to quantify any specific actual impacts. While seeking to establish a linkage between a system and potential impacts, LCA models are suitable for relative comparisons, but may be not sufficient for absolute predictions of risks.

Even for relatively small systems, LCA is a comprehensive task that requires interdisciplinary knowledge in the technical and economic areas. Hence, LCA projects are typically assigned to teams of experts and can rarely be performed by a single person with sufficient accuracy.

LCA approach has developed over decades, coming from a product-oriented model used to evaluate environmental impact to a bigger framework that elaborates on a wider environmental, economic, and social scale. At the current stage, LCA is being transformed into Life Cycle Sustainability Analysis (LCSA), which links the sustainability questions with the knowledge and research needed to address them. Check out the following article to learn more about the LCA history and background:

In Lesson 2 we explored the definitions of technology and attempted to characterize its role in sustainability systems. We learned that before technology can become part of society, it has to be developed and pass through a few levels of adaptation. This process of adaptation is largely governed by social and economic factors, not simply by the technical benefits proved through research and science. Decision making as for to deploy or not to deploy a particular technology, on what scale, at which location and when, would rely on (1) technology readiness (which is determined through TRL analysis) and (2) on technology adaptation to the social, economic, and environmental spheres (which is assessed through the LCA analysis). Both types of assessments are complex, require a significant amount of factual data, and must be system-specific and location-specific. This lesson provides important background on both of the above-mentioned methodologies. The next step will be to choose metrics and to develop quantitative indicators for assessment.

In this lesson, we take a step further in the evaluation of technologies from the standpoint of environmental, economic, and social compatibility. Building upon the life cycle assessment concepts presented in Lesson 2, we will learn how to develop or select the metrics that would allow us to quantify the impacts and to decide on viability of technology projects. Metrics are important analytical tools when it comes to objective decisions, but they are not something predefined and ready to use. Metrics are meaningfully designed and tuned for a particular purpose, and it is the job of the evaluator to define that purpose prior to the analysis. This lesson overviews some of the methods that are used in environmental science and economics for technology evaluation. However, we are only scratching the surface here. Those areas of science are quite extensive and can fill whole books. So, while working through the basics and studying examples, be prepared to search further and specialize when you chose the metric set for your final course project down the road.

Learning Objectives

By the end of this lesson, you should be able to:

• understand different levels of metrics and their connection with assessment goals;
• perform calculations of some environmental metrics / indicators and interpret their meaning;
• review the fundamentals of the economic analysis of technologies. Perform calculations of some economic metrics using simple payback and discounted cash flow approaches.

Required Readings

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

One of the challenges in sustainability assessment of technologies or other elements of anthropogenic systems is designing meaningful and quantifiable metrics. Because sustainability frameworks are built on very diverse sets of environmental and economic values, there is difficulty in bringing them to common terms within a unified model.

When we ask the question "Is this process sustainable?", we often do not get a "yes/no" answer. Some parts of the system may benefit sustainable development, some parts may be in conflict with it, and some parts may be rather neutral or flexible. But how can we tell where we are on the scale of sustainability assessment? Further, if we do alter certain parts of the system, how much shift do we create towards sustainability goals? Can we measure the impact of those changes?

All these questions prompted attempts to develop quantifiable metrics or indicators, which would allow researchers and policy makers to make more accurate comparisons between different paths of system development and take better justified decisions.

The existing methods for evaluating products and technologies in terms of environmental impact and sustainable development are numerous, and the scope of their applications and purposes is extremely wide. Metrics have been and continue to be developed by different agencies, companies, and researchers to address a variety of issues, which were often placed in different frameworks. As a result, those methods of assessment may use widely diverging rationale, terminology, and approaches, and often come up with contrasting results. Consistency and compatibility are most difficult issues!

In this lesson, it would be hardly possible to learn all of the methods in detail, especially because most models and evaluation approaches are subject-specific and would rather be learned in the context of a particular technology. But we will take a tour over several evaluation platforms and will try to distill the most important questions to address as we proceed to characterization of particular technological areas in further lessons of this course.

Numerous technologies existing in the world differ in many aspects (e.g., profitability, social popularity, efficiency, scale, local need, resource consumption, etc.). However, our main goal will be to distinguish and characterize the technologies in terms of sustainable development. In the long run, the main question we aim to answer: Is the technology project sustainable or not sustainable? What are the criteria for "good" and "evil" here?

How are metrics developed?

What exactly is a metric? A metric is a system of measurement that includes:

• the item being measured (what we measure),
• the method of measurement (how we measure), and
• the inherent value associated with the metric (why we measure, or what we intend to achieve by this measurement).

According to Werner and Souder [Werner and Souder, Research-Technology Management, 40(2), 1997, 34-42], the choice of an appropriate measurement metric depends on the user’s needs and purpose, the area of study, and the available data. Setting the purpose of evaluation is the key. Without it, the metrics are simply data. There should be a decision focus.

Metrics are categorized into quantitative-subjective, qualitative, and integrated metrics. The type is often determined by the availability and accuracy of raw data. Data must be accessible and affordable; otherwise, assumptions and surrogate information would inevitably undermine the adequacy and validity of assessment.

Standardization and coherence in rules of construction of technology evaluation metrics are yet to be achieved. In the broad area of science and technology, the practice of creating and using metrics is in the form of a "menu." Evaluators select combination of measures, data sources, and instruments that will address their specific objectives and needs.

The following issues make metrics not a straightforward matter:

• A metric may be composed of a single quantity or by a more complex set of measures (for example, indexes and "macro" metrics).
• Metrics in science and technology evaluation are designed to measure a variety of activities, events, and phenomena—some simple and short-lived, others highly complex and durable along an extended time frame and therefore using different units and scales.
• The absence of a unique and single building-block increases the role of subjective reasons for the construction and selection of metrics, which sometimes requires better formalization.

Designing comprehensive universal metrics, which would work as "magic crystal" for decision makers, is difficult, if at all possible, because different stakeholders care about different impacts. Most analytical approaches separate contexts and rather develop multi-metric frameworks for assessment. The table below lists some examples of metrics used for technology evaluation in various contexts. This list is not exhaustive, by any means, and in each assessment project metrics must be justified and modified for specific research purpose.

[Source: National Renewable Energy Laboratory]

While working on this course, you should feel free to modify existing metrics or create new ones for the specific needs of your assessment. There are no "mandatory" criteria for evaluation - it all depends on the purpose and the message you try to deliver.

Lagging versus leading metrics

• Lagging metrics are those that indicate what has already happened (past). For example:
  • amount of soil eroded
  • electricity cost per kWh
  • average annual temperature
  • battery efficiency measured
• Leading metrics are those that indicate what may happen (future). For example:
  • deforestation rate
  • input / output ratio
  • wind direction and speed
• Lagging metrics are mainly actual measures; leading metrics are usually indicators marking rates or trends

Complexity levels of metrics

(In parentheses, some examples of metrics are given for the case of a wastewater treatment facility.)

• Level 1 – Measure a technology’s level of compliance with regulations or its conformance with industrial performance standards (e.g., output concentration of hazardous chemicals versus EPA tolerance standards).
• Level 2 – Measure the inputs, outputs, and performance of a technology during system operation (e.g., cost of purified water per gallon, amount of solid waste generated per year, treatment efficiency).
• Level 3 – Evaluate the potential impact of the technology and associated operation on facility personnel, the surrounding environment, and communities (e.g., eutrophication, local air quality trends, carbon emission cost of facility operation).
• Level 4 – Evaluate the lifecycle effects of the technology. This will involve Level 1-3 metrics as necessary to assess the impact of technology’s manufacturing, operation, and disassembly stages (e.g., amounts of raw materials consumed for building the facility, % carbon emissions related to transportation and infrastructure maintenance, water filter life and disposal).
• Level 5 – Assess how the technology-related activities affect the sustainability balance at the scale of society, region, or planet (if the technology is scaled-up) (e.g., % renewable materials or energy used at different stages of operation, community quality-of-life indicators).

In the above hierarchy, Levels 1 and 2 may be sufficient for understanding the promise of technical performance. These levels would be primary guides in relationships between research and development sector and industry, which look for reliable and efficient systems. Ecological perspective would involve Level 3 in order to understand and track environmental impacts. Furthermore, sustainability analysis would have to involve Level 4 at the community scale and Level 5 at the economy scale, since only via thorough lifecycle assessment and system analysis is it possible to identify the correct targets for metric design.

One of the ways to understand if the choice of metric that is adequate to the purpose is sensitivity analysis. By varying impact factors, see how metrics respond. Simulating a series of "what-if" and "what-if-not" scenarios will lead you to designing a proper metric model and defining the boundaries.

Sustainability Indicators

The framework of sustainability indicators deals with much wider context than just technology assessment. It was developed for assessing socio-ecologic development of communities and associated resources and services, and technology can be certainly part of that context. Applying this framework to technology, we can see how technical performance metrics (such as efficiency and useful output) are connected to the economic, social, and environmental specifics of the locale, thus allowing us to estimate the promise of this technology in a local setting.

Systems of sustainability indicators are typically customized to a particular case study. One of the rationales is to take a more detailed approach to assessing sustainability and move beyond the traditional three-pillar approach, which conventionally classifies factors within social, economic, and environmental domains. Indicators can go through those boundaries and address specific needs of assessment.

Good indicators must be:

1. relevant to the problem or system considered in assessment;
2. understandable and easily interpretable by stakeholders and societies that may use the assessment;
3. reliable; i.e., based on trustworthy information and also sensitive to data variation;
4. built on accessible information (not something that is hidden or will become available in the future).

Collection of data and information for calculating sustainability indicators may be a big task. While much of the data can be available in local, state, and federal reports, and many of those can be available online these days, in some cases, you would need to contact respective agencies and offices to request missing information depending on your specific interest.

One of the criticisms of sustainability metrics and indicators is that they attempt to encapsulate an array of diverse processes and interactions in a few simple measures. Is that simplification fair? And what is the risk of using those simplified measures for taking rational decisions?

In fact, designing metrics can be an obvious approach to deal with the complex world in manageable bits. It is common for scientists to deal with a complex system by breaking it down and studying its components separately before studying how they work together. For example, in natural sciences, scientists have been dealing with complex ecosystems for years, and specific indicators have been long used as tools for gauging ecosystem health and development (Bell and Morse, 2008).

According to Slobodkin (1994):

"Any simplification limits our capacity to draw conclusions, but this is by no means unique to ecology. Essentially, all science is the study of either very small bits of reality or simplified surrogates for complex whole systems. How we simplify can be critical. Careless simplification leads to misleading simplistic conclusions."

To learn more about sustainability indicators, please turn to the following readings:

Environmental metrics are designed to assess the environmental impact of technology or activity. Such impacts are primarily related to using natural resources (lifecycle INPUTS) and generating waste and emissions (lifecycle OUTPUTS). The ultimate sustainability goal is to minimize the environmental impacts due to using non-renewable resources and minimizing waste and pollution. Since the complete elimination of these impacts is hardly possible (any technology has its environmental costs!), it is also important to evaluate the rate at which environment can absorb the impacts and become remediated.

There are a number of common metrics designed to characterize the lifecycle inputs and outputs. Some examples are given below:

* The units in the metrics are typically normalized by unit mass, unit volume, or unit area of a material or product, depending on application. For example, for lifecycle energy, it is common to see the units such as J/kg, which indicate how many jules of energy were spent for manfacturing, use, and disposal of 1 kg of the material or product over its lifecycle.

It should be noted that input metrics primarily characterize the sources of impacts (not impacts themselves), while output metrics aim to quantify the consequences - how the extraction and manufacturing processes and technologies may affect natural ecosystems, human health, and environmental values at large. 

Next we are going to take a closer look at some of the metrics and show how those can be estimated. 

Emergy / Transformity

The concepts of emergy and transformity are introduced as universal measures in the environmental accounting theory. The basic approach in that theory is to use energy units for assessing inputs and outputs of various natural and industrial systems. All types of energy and real wealth products are related to the primordial source - solar energy - through transformity. It is stated that going through multiple transformations via both technological and natural converters, available energy acquires new quality, while the load on the environment due to those transformations increases.

For example, on a hot day, we use an air conditioner. The energy to power the air conditioner comes from the electricity grid. Prior to that, the electric energy is generated at a power plant via conversion of thermal energy of steam and kinetic energy of the turbine into electricity. The thermal energy is, in turn, produced by combustion of fossil fuels. Energy stored in the fossil fuels (which were originally biomass) was actually the solar energy transformed by plants to organic matter via photosynthesis. So, solar energy is indeed the original component of the final energy used by the air conditioner (Figure 3.1).

Figure 3.1. Energy transformations resulting in a new quality of usable energy.

Credit: Mark Fedkin

Transformations of the primary types of energy through an array of energy conversion processes and technologies described in the example above demonstrate the idea of transformity applied to a particular type of usable energy, such as electricity. In other words, transformity indicates how many transformations are necessary to obtain a particular sort of energy in a usable form and also show how “costly” those transformations are for the environment. Quantification of the energy inputs and outputs in terms of primary solar energy may be a tricky task; however, a number of studies provided such data and enabled energy flow analysis for environmental systems.

Emergy is defined as the available solar energy used up directly or indirectly to make a service, product, fuel, or another form of usable resource. This term essentially means the solar energy equivalent. Transformity, in this case, is the equivalence factor:

Emergy [seJ] = Energy stored or available [J] x Transformity [seJ/J]

Emergy is usually measured in solar energy joules [seJ], and transformity is therefore expressed as a ratio of solar energy Joules to regular Joules.

Embodied Energy

Embodied energy is another popular representation of the same concept. By definition: embodied energy is the sum of all the energy required to produce any material or product considered as if that energy was incorporated or 'embodied' in the product itself (Wikipedia, Embodied Energy).

The main difference between the embodied energy and emergy is that the former does not include the energy content in the raw resource (e.g. energy content in growing trees), but rather just accounts for the subsequent energy expenditures associated with the extraction, processing, and manufacturing stages.

Embodied energy is often expressed in the units of energy per making a unit mass [J/kg], unit volume [J/liter], or unit area [J/m²] of material depending how the its amount is accounted. Some data are given below for illustration.

For more complex products consisting of multiple raw materials, the embodied energy increases significantly. For instance, for a common monocrystalline silicon solar PV panel, the embodied energy was estimated at ~4750 MJ/m².

Global Warming Potential

Global Warming Potential (GWP) is a very common way to account for greenhouse gas emissions of a project. It can be used within the Lifecycle Assessment and outside of it as a criterion for choosing the most climate-friendly solution among the alternatives. GWP scale is also commonly used to compare different atmospheric gases and pollutants with respect to their ability to cause greenhouse effect. In that sense GWP is a relative metric - it is always related to carbon dioxide CO₂ as the universal benchmark.

GWP of a gas depends on:

• Heat (IR radiation) absorption properties
• Spectral location of the absorbed wavelength (specific for Earth's radiation range)
• Atmospheric lifetime (longer = more impact)
• Time span of assessment (commonly 100 years)

For example, GWP of methane (CH₄) = 25. That means that a ton of methane causes 25 as much warming in the atmosphere as a ton of CO₂ due to greenhouse effect over a 100-years period.

Here is the list a few common atmospheric pollutants graded on the GWP scale.

It is easy to notice the correlation between the longer lifetime and GWP. Some gases are not necessarily potent IR absorbers, but due to very long persistence in the atmosphere, the overall impact is compounded in the long term.

Let us see how these GWP factors for these chemicals can be used in project assessment.

Example

Assume greenhouse gas (GHG) emissions from an agricultural project are estimated as follows:

• Carbon dioxide: m(CO₂) = 5 ton/year (gasoline and diesel-based machinery, irrigation pump, electric grid emissions)
• Methane: m(CH₄) = 0.1 ton/year (organic decay, on-site waste management)
• Nitrous oxide (N₂O) = 0.01 ton/year (transportation emissions)

All these emissions will contribute to the greenhouse effect and global warming, but not equally. Total contribution can be calculated based on GWP metrics:

Figure 3.2. Contribution of gases to cumulative climate impact according to their GWP factors. 

Credit: Mark Fedkin

As another example of using GWP, you can look at the LCA study by Stoessel et al., 2012, that assessed various crops with respect to a number of environmental metrics. Figure 2 of the paper makes an interesting illustration of environmental costs of production and sales of different types of agricultural produce.

Kaya Equation

Kaya Equation (introduced by the economist Yochi Kaya) is another example of environmental metric, which helps to estimate the total CO₂ emissions of a country based on some common social and economic information, such as population, gross domestic product, energy intensity, and carbon intensity:

$$C{O}_2(emitted)=(P)\times (\frac{GDP }{P})\times (\frac{E}{GDP })\times (\frac{C{O}_2}{E})$$

Where P = population, GDP = gross domestic product, (GDP/P) = GDP per capita, (E/GDP) = energy intensity per unit of GDP, and (CO₂/E) = carbon intensity, i.e., emissions per unit energy consumed.

Obviously, the population is an important factor here since more people means more energy use, so it is included as the first term in this equation. GDP is commonly determined the market value of all officially recognized final goods and services produced within a country in a given period of time. GDP per capita is often considered an indicator of a country's economic well-being and standard of living. GDP per capita appears as the next term in the formula, since bigger economy means higher energy use. The next two terms - energy intensity and carbon intensity - are technology related. As we develop more efficient ways to convert energy or produce goods through technological innovation, we expect that it will take less energy to increase our GDP by another dollar. As efficiency grows, the E/GDP term should go down. Finally, the carbon intensity is primarily affected by the ways we generate energy. As we develop and gradually switch to renewable energy sources and minimize the use of fossil fuels, we should see CO2/E factor to decrease. As a result, less carbon dioxide will be emitted per kW of power produced.

The last metric in the Kaya equation is also useful to understand the real "carbon cost" of the energy converting technologies. The more fossil fuel burning is involved in the production of consumable energy (energy conversion), the higher the “carbon cost” of each bit of that energy. Renewable energy technologies, such as solar, wind, and others are characterized by lower (CO₂/E), or even approach zero carbon in an ideal case. However, from the systems perspective, zero emission is not always achievable, since manufacturing, maintenance, and support system operation of such energy conversion systems may still require a certain amount of energy from fossil fuels.

The Kaya model allows estimating how changing technological solutions for energy conversion can help the economy in terms of emission reduction. Determination of the CO₂/E factor provides a quantitative scale for measuring environmental impact in terms of “carbon cost”. The CO₂/E metric is common in many assessment studies discussing alternative energy sources. We need to keep in mind that reported values usually reflect the lifecycle, "cradle to grave" emissions, i.e.,those related to raw material extraction, manufacturing, delivery, operation, maintenance, and decommissioning altogether (not just operational emissions).

Data Reading Exercise:

Take a look at this example of a National Renewable Energy Laboratory (NREL) study that had a goal to compare the lifecycle greenhouse gas emissions of various energy technologies. The study took into account the total estimated emissions from more than 2100 LCA publications and related those to the total amount of energy generated by those systems during their lifetime operation. The carbon intensity results are summarized on the bar graph (p.2 of the fact sheet). Interpreting the graph, answer the following questions for yourself and write answers in your notes:

• What units are used to express the CO₂/E metric?
• Energy from which technology (out of those studied) has the highest "carbon cost"? Which one has the lowest "carbon cost"?
• Which stage of the technology lifecycle does result in the most CO₂ emissions: in case of renewable energy systems and in case of fossil fuel energy systems?

In summary, a review of the Kaya equation indicates that the development of technologies can lower the global and country's carbon emissions in two ways: (1) increasing conversion efficiency and (2) decreasing carbon content in the lifecycle.

When a systems approach is used for technology evaluation, the financial dimension of the system life cycle cannot be omitted. While it is not the purpose of this course to teach the entire theory of economic assessment, reviewing some fundamentals and practical tools for economic evaluation should be useful here.

The purpose of economic metrics is to provide the quantitative information needed to make a judgment or a decision on deployment of a new technology or to select alternative options. The most complete analysis of an investment in a technology or a project requires the analysis of each year of the life of the investment, taking into account relevant direct costs, indirect and overhead costs, taxes, and returns on investment, plus any externalities, such as environmental impacts that are relevant to the decision to be made.

Cash Flow Analysis

Cash flow is a tool used to show how the project expenses and revenues vary over the term of the project - it is a financial timeline. For the basic cash flow, the following terms need to be defined:

• Term of the project – for how many years the process, technology, or facility will be deployed.
• Initial cost (capital investment) – one-time expense at the beginning (e.g., purchase of major assets - land, equipment, buildings, labor).
• Annuity – annual increment of cash related to the operation of the technology:
  • positive, if it brings revenue;
  • negative, if it brings expense;
  • Note that net (expenditure vs. revenue) balance should be positive in order to repay the investment cost.
• Salvage value – one-time positive cash flow at the end of the planning period (if everything is sold in its actual condition). Usually, salvage value is low compared to initial cost.

General cash flow scheme can be visualized as follows (Figure 3.3):

Figure 3.3. Generic cash flow diagram showing the phases of a technology project.

Click for a text description.

A horizontal line is labeled years and is numbered zero through seven. Above the line is revenue and below the line is maintenance/operation costs. At year zero, a large arrow points down, labeled initial cost investment. From year one to six, double-headed arrows show both revenues and maintenance. Revenues remain constant while maintenance fluctuates. At year seven, a single headed arrow points up and is taller than year one through six revenues and is labeled salvage. Years zero through seven are labeled annuity.

Credit: Mark Fedkin

Modeling the cash flow helps assess the financial viability of a project and answer some of the important questions before the decision is made to start the project.

In this section, we are going to consider two basic approaches to cash flow analysis for a project: (1) Simple Payback approach and (2) Discounted Cash Flow analysis.

The first method is attractive for its simplicity and can be used as a quick-check calculation before any further, more sophisticated analysis is performed. It is best suited to short-term projects, in which the money value is not significantly impacted by inflation. The second method is preferred for long-term projects, when the money value is expected to significantly change over time or if interest is applied to investment over an extended period of time.

Referenced below are two reading sources that provide background on the economic evaluation, which will introduce several key economic metrics. The first source is more important, and its content is linked to one of the homework assignments given in this Lesson. Additional explanations and examples to the concepts discussed in the Vanek and Albright's book are provided further in this section.

Simple payback approach

This approach is suitable for short-term projects with quick return on investment. In this case, discounting (for money value declining over time) may be unnecessary.

In simple payback evaluation, all cash flows into and out of the project are added up to find Net Present Value (NPV) metric. That includes initial cost, annuities, and salvage value.

NPV = – Initial Cost + S(Annuities) + Salvage Value

The break-even point, i.e., the year when the sum of annuities surpasses the initial cost and the initial expenditures have been paid back, is characterized by the Simple Payback Period (SPB):

SPB (years) = Initial Cost / Net annuity

For the case described above:

Capital Recovery Factor (CRF) evaluates the relationship between the cash flow and investment cost. This evaluation is applicable to short-term investments (within N=10 years).

CRF = ACC / NPV

where ACC = Annual Capital Cost

ACC = Annuity – NPV/N

Here, the NPV/N term is the average share of the net present value per each year of the project. So, ACC is the part of the annuity that goes each year to cover the investment; it does not go towards profit.

Discounted Cash Flow Analysis

This approach is better applied to long-term projects with slow payback. Money value declines over time, so it must be taken into account.

For example, many renewable energy projects generate low positive annuity at the beginning, while having high initial costs, so it takes more years to pay back investments. In this case, the discounted evaluation should be used.

In the case of discounted cash flow, we need to evaluate how much any cash flow element would value in the future. That would depend on the interest rate (i) imposed on initial investment and the number of years (N) the project is underway. The following conversion factors are used:

$$\frac{\mathrm{present value} }{\mathrm{future value} }=\frac{P}{F}=\frac{1}{{(1+i) }^N}$$

$$\frac{\mathrm{present value} }{\mathrm{annuity} }=\frac{P}{A}=\frac{{(1+i) }^N-1 }{i{(1+i) }^N}$$

Then the NPV can be calculated using the following equation: 

NPV = – Initial Cost + (P/A) × Annuity + (P/F) × Salvage Value

Another useful metric associated with the discounted cash flow analysis is Internal Rate of Return (IRR), which corresponds to the marginal interest rate that would allow the project to break even in the end of the term.

By calculating NPV future value for the end of the project term at different interest rates, one can find the rate at which NPV is equal to zero. The rate corresponding to that condition is IRR (Figure 3.4).

Figure 3.4. Determining of the Internal Rate of Return (IRR) as the limiting interest rate for a project.

Credit: Mark Fedkin

Another illustration of the comparison of the simple payback and discounted cash flow methods is given by the Example on p.67 of the book [Vanek and Albright, 2008].

Listed below are some other economic measures that can be used in different analyses as metrics to evaluate technological systems:

• TLCC = Total life cycle cost
• LCOE = Levelized cost of energy
• RR = Revenue requirements
• B/C = Benefit to cost ratio
• SIR = Savings to investment ratio

You can refer to supplemental reading source [Short et al., 1995] mentioned above for more details on how these metrics are useful and how they can be estimated.

According to the Western Australia Council of Social Services (WACOSS):

"Social sustainability occurs when the formal and informal processes; systems; structures; and relationships actively support the capacity of current and future generations to create healthy and livable communities. Socially sustainable communities are equitable, diverse, connected and democratic and provide a good quality of life."

When we talk about environmental metrics, we focus on well-being of environment; when we talk about economic metrics, we focus on well-being of economy. Hence, the social metrics should be measures of well-being of society or particular groups of people involved as stakeholders. While understanding the importance of sustainable development, people do not still want to give up wealth, capabilities, convenience of life. Although changes in lifestyles and consumption habits can be considered a necessary sacrifice, social analysis seeks to reveal the ways of social transformation that would be less stressful, yet more efficient in reaching sustainability goals. Comparison of different avenues for development would require establishing social metrics.

The following dimensions can be identified in the social context:

Quality of life - basic needs are met and a good quality of life for all members is fostered at the individual, group, and community level (e.g., health, housing, education, employment, safety).

When evaluating a technology project, one can use the following questions as a checklist to see how the development affects or improves:

• affordable and appropriate housing opportunities for the target group;
• physical health outcomes for the target group;
• mental health outcomes for the target group;
• education, training, and skill development opportunities for the target group;
• employment opportunities for the target group;
• access to transport for the target group;
• ability of the target group to meet their basic needs;
• safety and security for the target group;
• access to community amenities and facilities for the target group.

Equity - equitable opportunities and outcomes for all its members, particularly the poorest and most vulnerable members of the community.

Check how the technology project will:

• reduce disadvantage for the target group;
• assist the target group to have more control over their lives, socially and economically;
• identify the causes of disadvantage and inequality and look for ways to reduce them;
• identify and aim to meet the needs of any particularly disadvantaged and marginalized people within the target group;
• be delivered without bias and promote fairness.

Diversity – co-existence of different viewpoints, practices, ethnic, cultural, racial groups in the community.

Check how the technology project will:

• identify diverse groups within the target group and look at ways to meet their particular needs;
• recognize diversity within cultural, ethnic, and racial groups;
• allow for diverse viewpoints, beliefs, and values to be taken into consideration;
• promote understanding and acceptance within the broader community of diverse backgrounds, cultures, and life circumstances.

Interconnected/Social cohesions – establishment of processes, systems, and structures that promote connectedness within and outside the community at the formal, informal, and institutional level.

Check how the technology project will:

• help the target group to develop a sense of belonging in the broader community;
• increase participation in social activities by individuals in the target group;
• improve the target groups’ understanding of and access to public and civic institutions;
• build links between the target group and other groups in the broader community;
• result in the provision of increased support to the target group by the broader community;
• encourage the target group to contribute towards the community or provide support for others.

Democracy and governance – ensuring democratic processes and open and accountable governance structures.

Check how the technology project will:

• allow for a diverse range of people (especially the target group) to participate and be represented in decision-making processes;
• facilitate a clear decision-making process understandable by staff and stakeholders;
• have a budget sufficient to ensure adequate delivery by qualified, trained staff;
• ensure that the use of volunteers is appropriate and properly governed;
• have duration sufficient to achieve the desired outcomes;
• have Plan B - what will happen when the project ceases.

Maturity - an individual accepts the responsibility of consistent growth and improvement through broader social attributes (e.g., communication styles, behavioral patterns, indirect education, and philosophical explorations).

Check how the technology project will:

• be dependent on the responsible decisions of individuals in the target group;
• require additional knowledge and education of stakeholders.

Most of the social metrics are hard to quantify. In assessments, we have to develop a rubric that explains the low and high values on metric scale and choose a reference system for consistent comparison.

Several quantitative metrics have been constructed by Brown and Ulgiati (1997), based on the emergy theory (see system diagram in Figure 3.5). The treatment below provides a good example of how environmental metrics can be blended with economic and social aspects and link them to the system sustainability in a broader sense.

Figure 3.5. Emergy-based indices, accounting for local renewable emergy inputs (R), local nonrenewable inputs (N), and purchased inputs from outside the system (F).

Credit: Brown, M.T. and Ulgiati, S., Ecological Engineering 9 (1997) 51–69

Figure 3.5 is a system diagram showing the energy flows and transformations within a generic locale (surrounded by the system boundary). The Economic Use box can be seen as a "transformer" of the available energy and resources into some Yield (Y), i.e., some product directly related to the function of this system. The inputs to the system are classified as renewable resources, non-renewable resources, local resources, and non-local (purchased) resources. In this model, it is presumed that system sustainability is favored by using renewable energy resources and local energy resources. The resources that are both renewable and local are denoted by R on this diagram. On the contrary, non-renewable local (N) and any non-local, i.e., purchased (F) resources are assumed to lower overall sustainability of the system. These assumptions set the basis for devising a few sustainability metrics in this study.

One of such metrics, which characterizes the environmental impact of an energy flow, is Environmental Loading Ratio (ELR):

ELR = (F + N) / R

From this relationship, we can see that the more non-renewable and outside resources are involved in the process, the higher the ERL index. An increase in renewable energy use in the denominator translates into a lower ELR value. As you can guess, lower ELR is beneficial for the environment.

Another index introduced here is Energy Yield Ratio (EYR):

EYR = Y / F

This metric characterizes the system's capability to exploit local resources (renewable or not). The more the system depends on imported resources or services (increasing F), the lower the EYR, and the higher the system's vulnerability.

Finally, the Sustainability Index (SI) combines both ELR and EYR as follows:

SI = EYR / ELR

Obviously, for higher sustainability “score”, we are interested in having the highest EYR versus the lowest ELR. Within this approach, SI can be used as an aggregate measure to characterize the sustainability function of a given process, technology, or economy.

Please see further explanation of this method and example calculations of metrics in the reading material referenced below.

Note that the above-described approach to assessing a system sustainability is just a single illustration of how sustainability metrics can be devised. The parameters chosen by the authors were specific to their objectives. Calculations they provide answer some of the questions, but may not answer other questions that different stakeholders may have. In that respect, setting the objectives for your assessment and stating clear definitions and assumptions is a very important step in any assessment study in order to make the results meaningful.

Ideally, we would like to see the environmental, economic and social dimensions, and benefits of new technologies balanced. However, most real-life situations would gravitate differently towards those three dimensions. Results of the metric analysis need to be presented in a way that provides a clear and informative message to stakeholders and investors. Presented below are a couple of examples from sustainability assessments performed by government organizations.

The radial diagram in Figure 3.6 was presented by the National Renewable Energy Laboratory (NREL) to describe the sustainability profiles of several energy technologies. Six selected criteria plotted in 6 different directions in the form of a propeller provide an illustration of balance or lack of balance in system analysis. Note that each of the metrics is not directly comparable to others (like we saw in the case of the energy analysis, when all impacts are normalized to the same unit and scale). In this case, the scale for each metric needs to be defined independently versus boundary conditions (minimum and maximum values) so that it covers the appropriate range of evaluation.

Figure 3.6. A visual representation of different categories of sustainability metrics. Click for a text description

This diagram is basically a six-sided star with one category of sustainability metrics shown at each point. From the top right, and continuing clockwise, are the following categories:

• Climate Friendliness - GHG Emission (g-CO2 eq/kWh) - min=1000, Max=0
• Water Conservation - Annually Available Freshwater Usage (%) Min=35, Max=0
• Safety - Fatalities from Severe Incidents (fatalities/GW-year) Min=0.12, Max=0.000248
• Local Employment Impacts - Contribution to County Employment (%) - Min=0, Max=1
• Energy Affordability - LCOE (USD/kWh) - Min=0.39, Max=0
• Energy Diversity - Change in Diversity Indicator (%) - Min=-5, Max=5

Credit: National Renewable Energy Laboratory

The diagram below (Figure 3.7.) presents another example of how different categories of metrics are balanced to characterize the sustainability profile of a city. From this representation, we can immediately recognize that the most problematic areas the city may want to address first are Emission and Waste, which create a critically bad impact, and Materials and Energy flows (the lowest: red and orange scores in the pie). At the same time, Cultural Engagement and Identity is the most attractive feature of the city (the highest: bright green score). We can also conclude just from a quick glance that the ecological part of this sustainability system is most suppressed, while the cultural part is probably most developed and sound. On the political and economic fronts, some of the impacts are in the favorable range, while others are down to satisfactory. This snapshot of the disbalance provides a tool for comparison when other systems (cities) are evaluated against the same metrics.

Figure 3.7. Radial diagram showing the sustainability of metropolis of Melbourne (Australia) as developed by UN Global Compact Cities Programme.

Credit: Wikimedia Commons

When considering specific technologies in the context of sustainability, the ideal expectation is that they score equally well on all three evaluation domains – environmental, economic, and social. The scoring metrics should be chosen wisely, with primary consideration of the main stakeholders’ interests. When comparing different technologies as alternatives for a project, go with the same set of metrics. Collection of location-specific and accurate data is critical for accurate assessment. Multi-metric assessment may not give you a simple answer, but may provide a more realistic ground for decision making. Resources listed in this lesson will be especially useful in choosing the path for the assessment study in your final course project.

References and Resources:

Bell, S. and Morse, S., Sustainability Indicators: Measuring Immeasurable?, 2nd Ed., London - Sterling VA, 2008.

Brown, M.T. and Ulgiati, S, Emergy-based indices and ratios to evaluate sustainability: monitoring economies and technology toward environmentally sound innovation, Ecological Engineering 9 51–69 (1997).

Hammond, G.P. and C.I.Jones, Embodied Energy and Carbon Footprint Database, Department of Mechanical Engineering, University of Bath, United Kingdom (2006).

Odum, H.T., Environmental Accounting, John Wiley & Sons, 1996.

Short, W., Packey, D.J., and Holt, T., A Manual for the Economic Evaluation of Energy Efficiency and Renewable Energy Technologies, National Renewable Energy Laboratory, Golden, CO, 1995.

Vanek, F.M., and L.D. Albright, Energy Systems Engineering. Evaluation and Implementation, McGraw Hill, 2008.

Over the past three lessons, we looked into different methods and frameworks that can be used for evaluating technologies or technology-dependent systems. Those methods involved both qualitative and quantitative metrics. The main challenge, however, is that there is no unified system of evaluation developed or recommended so far, and we have to be case-sensitive when choosing our path for the evaluation of a particular project. In further lessons, we visit different areas of industry and technology and see how the evaluation approaches are adapted to those specific topics. We will learn from real-life case studies and try to see which of the previously reviewed methods would be applicable for analysis and which would be not. Lesson 4 explores the areas of green chemistry and advanced materials. We will see how the principles of sustainable development are tuned for these areas and what steps are taken to implement them.

Learning Objectives

By the end of this lesson, you should be able to:

• understand and explain the principles of green chemistry;
• articulate the benefits and obstacles of green chemistry applications;
• evaluate the promise of alternative chemical technologies;
• explain the ways the multifunctional materials can impact the technological systems.

Readings

• Website: 12 Principles of Green Chemistry, American Chemical Society, 2014.

Reading materials for this lesson are mostly contained within the course website. The lesson contains multiple links to web resources, and you are alerted to open the most important ones. Some optional reading resources are referenced in blue boxes in the body of the lesson.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

Green chemistry is the approach in chemical sciences that efficiently uses renewable raw materials, eliminating waste and avoiding the use of toxic and hazardous reagents and solvents in the manufacture and application of chemical products. Green chemistry takes into account the environmental impact and seeks to prevent or lessen that impact through several key principles outlined below.

Here are the 12 key principles of green chemistry as formulated by P.T. Anastas and J.C. Warner, in Green Chemistry: Theory and Practice, 1998.

1. Prevention. It is better to prevent waste formation than to treat it after it is formed.
2. Atom economy. Design synthetic methods to maximize incorporation of all material used into final product.
3. Less hazard. Synthetic methods should, where practicable, use or generate materials of low human toxicity and environmental impact.
4. Safer chemicals. Chemical product design should preserve efficacy whilst reducing toxicity.
5. Safer solvents. Avoid auxiliary materials - solvents, extractants - if possible, or otherwise make them innocuous.
6. Energy efficiency. Energy requirements should be minimized: conduct synthesis at ambient temperature and pressure.
7. Renewable feedstocks. Raw materials should, where practicable, be renewable.
8. Reduce derivatives. Unnecessary derivatization should be avoided where possible.
9. Smart catalysis. Selectively catalyzed processes are superior to stoichiometric processes.
10. Degradable design. Chemical products should be designed to be degradable to innocuous products when disposed of and not be environmentally persistent.
11. Real-time analysis for pollution prevention. Monitor processes in real time to avoid excursions leading to the formation of hazardous materials.
12. Hazard and accident prevention. Materials used in a chemical process should be chosen to minimize hazard and risk for chemical accidents, such as releases, explosions, and fires.

Chemists are guided to use these 12 principles as a checklist for evaluation of a specific process or chemical technology at the stage of design and scale-up.

Initiation and development of the above-listed principles was closely tied to the Pollution Prevention Act enacted in the USA in 1990. This document was a turning point in environmental policy by putting a particular focus not on environmental remediation and clean-up (i.e., fixing the damage at the end of the pipe) but rather on waste minimization and elimination of pollutants at the point of origin. This strategy of pollution prevention is also referred to as source reduction and is viewed as the first-choice measure to reduce risk to human health and the environment. Some of the attractive features of the source reduction are cost effectiveness, reduction in raw material use, pollution control savings, reduced risk to workers and the environment.

During the following year (1991), the Environmental Protection Agency (EPA) and National Science Foundation (NSF) initiated the Green Chemistry Program. A number of other similar initiatives were formed in the UK and some other countries. US Presidential Green Chemistry Challenge Award was founded in 1996. All these actions mark stepping stones in the green chemistry movement and philosophy, which gained more momentum in the following decades.

The green chemistry philosophy seeks to respond to public perceptions that chemistry and its applications via chemical technology have been primarily responsible for many of the ways the world degrades the environment. To reverse this stereotype, one of the central goals of green chemistry is to reduce risk to humans and environment from chemical synthesis, manufacturing, and application of chemical products through design of clean and closed-loop procedures.

Mitigating Risk and Hazard

Is there difference? Formally, in chemical fields, risk can be defined as a function of hazard and exposure:

Risk = f (hazard, exposure)

Traditionally, in industry and society, the reduction of risk is achieved through the reduction of exposure. By characterization of hazards (toxicity data) and knowing the effectiveness of the exposure controls ('containing the hazard'), risk can be manipulated or dissipated, especially at the early stages of the chemical chain, when it is easy to identify and measure. However, exposure controls may be not as useful downstream. The farther the hazard is from its source, the less the awareness of the potential hazard. With uncertainties in chronic effects, bio-accumulation, synergistic effects of chemicals, there is an uncertainty in risk mitigation.

The Green chemistry approach, in contrast with traditional practice, targets risk reduction through reduction of hazard. This is a safer approach because, if hazard is eliminated in the first place, there is no way risk can increase through any unpredicted spontaneous exposure increase anywhere downstream (Anastas and Warner, 1998).

Green Chemistry Control Keys

So, what are possible avenues for changing the existing practices towards the minimum-risk alternatives? There are several controls that can be manipulated at different stages of a chemical manufacturing process.

Using alternative feedstock or starting materials: Selection of the starting materials has a major effect through the whole synthetic pathway. It determines what hazards will be faced by the workers extracting the substance, shippers transporting the substance, chemists handling the substance. It also predetermines possible future risks from the end-products and wastes. Using more environmentally benign alternative feedstock may improve the environmental profile of the whole process (this links to green chemistry principle #7). One of the examples of this step is choosing between the petroleum feedstock and biological feedstock. Currently, 98% of all organic chemicals in the USA are produced from petroleum. Petroleum refining is extremely energy-consuming (15% of total national energy use) and contains high-pollution oxygenation processes. Agricultural feedstocks can be a great alternative that eliminate much of that hazard. Research has shown that many agricultural products (e.g., corn, soy, molasses) can be transformed via a variety of processes into textile, nylon, etc. (Anastas and Warner, 1998).

Using alternative reagents: Reagents are needed to transform the starting molecules into a target substance. Reagents are not necessarily consumed and are often recycled, but can still bear harm to people and environment exposed to the process. At this point, a chemist must balance the criteria of chemical efficiency and availability with potential hazards. This practice taps into green chemistry principles #2, 4, and 5.

Using alternative solvents: Solvents are a very common focusing point because a wide range of syntheses are performed in the liquid media. Many of the currently used solvents are volatile organic compounds. Many of those are responsible for air quality problems (smog, etc.) when released to air. While the traditional organic solvents are easily available, well characterized, and regulated, there is a push for alternative systems that are more environmentally benign in the long run – aqueous solvents, ionic liquids, immobilized solvents, supercritical fluids, etc. (Principle #5) The choice of an alternative solvent requires careful and specific analysis, which determines if the new process would be as efficient or as cost-effective. How such trade-offs are resolved is discussed later in this lesson.

Changing target product: Chemistry is function oriented – the target chemical is needed to perform a certain function or possess certain properties. This avenue is related to the search of the alternative final product, which may require radical change in the way synthesis is done (Principle #3). Through chemical research, it is possible to identify those parts of a molecule that provide the chemical with a desired function as well as those parts that provide toxicity. Maximizing the former and minimizing the latter is a worthy challenge for chemical design.

Process monitoring: Real time measurements (sensing) of process parameters and concentrations sometimes provide valuable information and hints how the process should be tuned to avoid adverse effects or risk (Principle #11). Also, process monitoring may open avenues for making the process more cost-effective.

Alternative catalysis: Catalysis bears enormous benefits, not only from the standpoint of technical efficiency. Environmental benefit results from the use of a much smaller amount of reagents in catalyzed reactions, which otherwise would contribute to the waste stream. Using less chemicals is also economically profitable. It should be noted, though, that many classes of catalysis (e.g., heavy metals) are very toxic. Hence, the challenge of alternative catalysis is to develop environmentally benign options (Principle #9).

As you can see, most of these measures are oriented towards reducing hazard in the first place. Eliminating, minimizing, or neutralizing toxic components at earlier stages of the process allows for more relaxed exposure control at later stages. Item 5 is more universal, as sensing can help monitor and control both toxicity and exposure at both inlet and outlet of the chemical system.

The green chemistry principles are also important as guidance for designing metrics for chemical technology evaluation. Some examples of those metrics are discussed further in section 4.3.

Case of Dead Fish - Lake Ariel

The following Video is text set to music. The text of the slideshow can be found in the transcript in the caption below.

Video: Intro to Lake Ariel Case (1:01)

Another example we can look into is the chemical incident on Lake Ariel in Wayne County, Pennsylvania. In 2014, the owners of the land where the recreational lake is located, contracted a New Jersey company to help clean the lake of algae. Accelerated algae growth is believed to be the result of lake pollution due to illegal septic systems flushing their waste into the lake. The contractor applied two algaecide treatments of copper sulfate to the lake, which resulted in killing around 10,000 fish. The Department of Environmental Protection issued a fine stating that copper sulfate applications should be spaced 7 to 14 days apart, whereas the company made two applications spaced only 3 days apart. The owner argued that the extremely hot day during that summer was what ultimately caused the fish death. Nevertheless, the shortened time in between applications was considered negligence.

Check the link below to collect additional facts about this case, then work through a few questions to analyze the situation:

NBC News - Philadelphia

From this example, we see that dealing with sensitive ecosystems requires extra diligence when chemical flows are involved. Quite often, certain aquatic species are only tolerant to a very narrow range of chemical parameters, such as ligand and metal concentration, alkalinity, and pH. Even small fluctuations may turn out lethal for sensitive species and can result in quick and irreversible ecological damage.

This example also provides an opportunity for exercising system thinking, during which we can try to establish multiple causal connections and understand the coupling effects, which are able to quickly amplify the ecological stress. In this case, we observed it with the heat factor. Hotter temperature not only "purges" water of oxygen (due to lower solubility levels), but also promotes algae growth, which in turn removes oxygen from water even further. The system analysis can help reveal this sort of double impact, alert us of the increased risk, and prevent hasty actions.

So, what does it take to change the conventional practice with possibly hazardous or harmful chemicals or processes to a more sustainable solution?

The major step is assessment of alternative solutions, which takes into account a wide range of criteria. When thinking about replacing the existing process with an innovative alternative, chemists and engineers try to avoid so-called "regrettable substitutions". In other words, avoid switching to an alternative process or chemical that either transfers risk to another point in the production chain or lifecycle or contains unknown future risks.

Ideally, in the concluded assessment, chosen alternatives must:

• be technologically feasible;
• provide the same or better value in performance and cost;
• have an improved profile for human health and environment;
• account for economic and social considerations;
• have potential to be sustainable over long period of time (look out for restrictions that may arise in the future; for example, shortage of rare elements, etc.).

We see that choosing the best alternative requires careful investigation! Such investigation must be comprehensive, i.e., would require cross-disciplinary expertise, and based on high quality data.

Let us look at some typical criteria that may be used in chemical industry and research for evaluation of various processes and reactions. In the "green chemistry" context, the main emphasis is put on the environmental profile of a chemical alternative, while economic feasibility is included in the picture at the stage of technology transfer.

Evaluation criteria

Table 4.1 below represents the set of criteria that can be effectively used for assessing alternatives in chemical and material manufacturing. On the left, the top-level criteria are listed, which are key points of concern when introducing new chemicals to the manufacturing process. The middle column lists some sub-criteria, which show how the impacts can be distributed. The right column specifies specific measures for each type of impact, which basically become guides for data search and analysis.

The list of criteria given in Table 4.1 has been proved effective for some case studies. While it puts the main emphasis on the hazard assessment and environmental impact, the technical and economic criteria are also included and can play a significant role even at the stage of selection of particular chemical reagents for the process. Note that the above list of criteria and sub-criteria is not something written in stone. It is presented here as an illustration. For each specific assessment project, choice of criteria needs to be justified through expert and stakeholder involvement and will depend on the goals of assessment. Depending on the assessment team decision, some criteria can be added, some – removed, and weights of all factors can be tuned. Clear identification and justification of the selected criteria is critical.

Data collection

In any assessment project, clear and consistent requirements should be set for the sources of data to be used. Information should meet specific data quality criteria for inclusion into the assessment. Quality of data will determine their utility. Data selection should follow the internationally recognized definition for reliable information: "Reliable information is from studies or data generated according to valid accepted testing protocols in which the test parameters documented are based on specific testing guidelines or in which all parameters described are comparable to a guideline method. Where such studies or data are not available, the results from accepted models and quantitative structure activity relationship (QSAR) approaches may be considered. The methodology by Organization for Economic Cooperation and Development (OECD) can be used for the determination of reliable studies." (Principles of Alternative Assessment, 2012)

Preferably, data should be obtained from authoritative bodies, those referenced by US government agencies (e.g. EPA). The following are links to some of such resources:

• U.S. EPA PBT Profiler software can be used to gain information on persistence, bioaccumulation potential and toxicity of organic substances.
• Government Toxicology Data Network

Technical data sources

Information should be obtained from published studies or directly from technical experts or users of the alternatives. In other cases, information can be requested from product manufacturers. The specific performance information (reactions, energy effects, thermodynamic analysis) available from experimental labs may be needed to draw conclusions about technical feasibility for each individual application. Clear referencing of the data sources is important.

Economic data sources

Data sources for financial information may include manufacturers, stakeholders, the Chemical Economics Handbook, and other standard reference sources. For many emerging alternatives, hard cost information may be unavailable. Cost comparisons today may not be directly extrapolated to emerging technologies because learning curves, scaling, and other factors can affect costs over time. Assumptions and use of surrogate data should be clearly explained in the assessment.

Ranking the alternatives

Quantification (scoring) of the impacts based on the criteria listed above is typically done via a multi-criteria analysis (MCA) model, appropriately build for the project. MCA provides techniques for comparing and ranking different outcomes of existing and alternative processes. When setting up an assessment project, it is important that the scoring system is transparent and is consistently applied to all scenarios under consideration.

MCA is a great tool for comparison of different options, but it is hardly objective because choice of criteria and metrics to quantify impacts varies from case to case. In contrast, cost analysis is aimed at providing objective measure of economic feasibility based on predicted cash flow. Cost analysis requires impacts to be expressed in monetary terms. MCA can use both monetary and non-monetary measures, as well as both quantitative and qualitative measures.

In MCA, ranking of chemicals or processes with respect to the listed criteria can be done in a variety of ways. One way is to assign each criterion a score that spans from 0 to 1, with the value of 1 corresponding to the best (most preferable) choice and the value of 0 corresponding to the worst (least preferable) choice among the available. The rest of the choices would score in between.

Another possible approach for assigning scores is outranking. There is no relative scoring, but instead, alternatives are compared by each criteria in pairs (two at a time). This way, we try to identify the extent to which one alternative out-performs the other. In the end, the dual performance scores (1 - "win"; 0 - "lose") are aggregated, and the preference index is calculated for each alternative.

Evaluation of the economic impacts associated with the implementation of a new product or practice generally focuses on the changes in capital and operational costs and revenues. (These terms of cost analysis were overviewed in Lesson 3.). The main areas where impact is expected are:

• cost of new equipment or production process;
• operation and maintenance costs (labor costs, energy costs, etc.);
• cost differences for different substances;
• cost of transportation;
• cost of design, monitoring, and training;
• regulatory costs.

The data on economic impacts is collected in consultation with relevant supply chain actors and possibly trade associations. Evaluation can be an iterative process, starting from qualitative comparison of the old and new scenarios and ending at quantification of impacts with monetary values.

The European Chemicals Agency (ECHA) website provides a more detailed guide to economic assessment of alternatives and can be used as a resource for this task. There are some documents linked that you are not required to read unless you're specifically interested in the socio-economic assessment.

Weighing factors

In most situations, decision-makers are not equally concerned about all highlighted criteria. For instance, a particular decision-maker may place more importance on whether a household cleaner causes cancer than on whether it contributes to smog formation. Thus, the decision-making method should account for respective “weight" of each criterion in the evaluation process. Since different stakeholders may place different weights upon criteria, the weighting raises significant questions in the context of a regulatory program. For example, can we consistently compare the alternatives without regulating the weight of factors? This is something to watch out for.

The criteria weights can be established by three methods:

1. using generic or recommended weights;
2. calculating the weights based from objective measures; and
3. eliciting weights from stakeholders or experts.

Method (1) is exemplified by Table 4.2 which lists several sets of generic weights recommended by National Institute of Standards and Technology (NIST) based on the data of Environmental Protection Agency (EPA) and Harvard Study for a set of criteria usually used in life cycle assessment (LCA).

In the above table, the NIST panel generated weights from stakeholder consulting that involved 7 building product manufacturers, 7 product users, and 5 LCA experts. EPA weights and Harvard weights were derived by NIST from sets of qualitative rankings of impacts developed respectively by EPA’s Science Advisory Board in 1990 and Harvard researchers in 1992.

Method (2) of calculating corresponding weights can be based on distance-to-target approach, when each criterion is weighted by the variance between the existing and desired conditions. For example, if the global community is further away from achieving the goal for global warming than it is for ozone depletion, then greater weight is given to the global warming potential. Another way to such calculation is monetary evaluation, when weighing is done based on the cost of environmental consequences.

Method (3), which assumes obtaining weights from stakeholders directly, may be based on public opinion surveys, community working group decisions, and different multi-criteria analysis models. The main types of stakeholders to consider: (1) Environmental Non-Government Organizations, Industry, Policymakers, and Consumers (Public). Weight assignments collected through surveys are then averaged across the board of stakeholders and then normalized to 100%.

Use of any of the methods depends on the goals of the assessment project, its scope, resources, and timeline. When building an assessment project, the weighing process should be transparent and well justified. When comparing different cases within one study, keep the weighing scale the same across the evaluation criteria.

Within the MCA approach, the final score (S_i) of a particular option (alternative) with respect to any major top-level criterion i is estimated as an average of all sub-criteria scores under that criterion:

$$S_i=\frac{{\displaystyle {\sum }_{j=1 }^n{s}_j}}{n}$$

where n is number of sub-criteria or metrics used to assess the option under top-level criterion i. The final total score (S_tot) is the weighted sum of all top-level criteria scores:

$$S_{tot }={\displaystyle \sum _{i=1 }^N{S}_i{w}_i}$$

where N is the number of top-level criteria considered in assessment; w_i is the weight factor of a particular criterion. The example study presented in the next section of this lesson demonstrates how the MCA scores are calculated and compared.

Consider the following supplemental reading materials on this topic:

The case study presented below exemplifies the application of a range of criteria to the process in the dry cleaner industry. This kind of analysis can help decision-making process in the green chemistry context.

(Source: UCLA Sustainable Technology & Policy Program, 2011)

Baseline and alternatives

The existing process of garment cleaning utilizes chlorine-based solvent technology, which is not sufficiently benign. This case study examines a few alternative technologies, which aim at making it a greener process. Table 4.3 below lists the alternatives under consideration.

The criteria for evaluation were selected from the list in Table 4.1.

Criteria weighting

Criteria weighting was based on stakeholder elicitation. Four stakeholder groups were considered by the authors: Environmental Non-governmental Organizations (NGO), Industry, Policymakers, and Consumers. The elicitation process was also designed to obtain stakeholder reactions to the criteria; for example, whether any relevant criteria have been left out. During interviews, stakeholder representatives were asked to rank the major criteria on the 100 point scale, and the average weight of that criterion was obtained by averaging scores over all interviews. The list of relative (percentage) weights of all major evaluation criteria, as voted by different stakeholders, is presented in Table 4.4.

As was noted by the authors of the study,

"on average, all stakeholder groups (except Industry) placed more weight on human health and ecological hazards as well as on environmental impact criteria. Industry and Policymakers assigned more weight to technical feasibility as compared to Consumers and Environmental NGOs. Industry placed more weight on economic feasibility than the other three groups. As discussed above, however, the sample sizes for the stakeholder groups were quite small (three in each group), with the goal of getting a sense of the potential differences across and within groups." (UCLA.., 2011)

Scoring methods

One of the goals of this project was to demonstrate the application of two techniques for multi-criteria decision analysis: (1) multi-attribute utility theory MAUT and (2) outranking.

"MAUT is an optimization approach, meaning that it represents the decision-maker's preferences as utility functions, and attempts to maximize the decision-maker's overall utility. MAUT is premised on the assumption that the decision-maker has a fairly well-defined set of preferences that can be represented on a dimensionless utility scale. It also assumes that the decision-maker is rational; that is, they prefer more utility rather than less and are consistent in those preferences. In the context of this project, therefore, a utility function was generated for each criterion, which reflects how a decision maker's preference changes for different values of that criterion. This utility function spans from 0 to 1, with a utility of 1 being assigned to the value of the best (or highest) alternative score for that criterion and 0 being assigned to the value of the worst (or lowest) alternative score. In this case, a linear utility function was used; which assumes that increases in utility are directly related to increases in the alternative's score for the criterion in question. Linear utility function was used as a default. Because the weighted scores for all criteria are added to produce the alternative's total score, MAUT is a 'compensatory' method. This means that poor performance on one criterion can be compensated by better performance on another.

Outranking models do not create utility functions, but instead directly compare the performance of two alternatives at a time, in terms of each criterion, to identify the extent to which one alternative out-performs the other. It then aggregates that information for all possible pairings to rank the alternatives based on overall performance on all criteria. Generally speaking, the PROMETHEE code used in the project creates a 'preference index' for each alternative, which is calculated by reference to the alternative's positive flow (i.e., those instances in which the alternative outperforms another alternative on a given criterion) and negative flow (i.e., those instances in which the alternative is outperformed by another alternative). The value awarded for winning a particular pairing is weighted, meaning it is adjusted to reflect the value placed upon that criterion by the decision-maker. Thus, outperforming another alternative in a minor criterion is worth less than outperforming it with respect to a more highly weighted criterion. As a default in PROMETHEE and most other outranking methods, any difference in performance - however small - will result in an increase in positive flow for the better performing alternative. As in MAUT, PROMETHEE recognizes that a decision-maker may be indifferent to how alternatives perform on certain criteria until certain levels are met or after certain levels are exceeded. Because outranking techniques aggregate the results of pairings for all criteria, they allow superior performance on some criteria to compensate for inferior performance on other criteria. However, they do not necessarily reflect the magnitude of relative under performance in a criterion versus the magnitude of over-performance in another criterion. In other words, if Alternative A is marginally worse than Alternative B in one criterion, but substantially better with respect to another, outranking may not fully 'compensate' Alternative A for its overall better performance. Therefore, outranking models are known as 'partially compensatory.'" (UCLA.., 2011)

Results

As Figures 4.1 and 4.2 demonstrate, for garment care, the two MCDA approaches ranked the alternatives in the same order. Both methods identified wet cleaning as the best overall performer. It was followed by CO₂ cleaning and perchloroethylene. Figure 4.1 displays the total score received by each garment care alternative under MAUT; the higher the score, the better the overall performance.

Figure 4.1. Garment assessment outcome using MAUT scoring system.

Credit: (UCLA.., 2011)

Figure 4.2. Garment care assessment outcome using outscoring method

Credit: Mark Fedkin - adapted from UCLA.., 2011

Figure 4.3 shows the breakdown of scores by each criterion. It is demonstrated that, "taking into account weighting, wet cleaning and CO₂ cleaning's impact on human health, environmental, and ecological criteria drove the outcome in this case. This was so despite CO₂ cleaning's very poor performance in terms of economic impact. Poor performance by DF-2000, nPB, Rynex and Green Earth in terms of physical and chemical hazards placed those alternatives behind the existing technology-perchloroethylene dry cleaning."

Figure 4.3. Garment care criteria contribution to MAUT scores.

Credit: (UCLA.., 2011)

Example of score calculation

Wet cleaning technique, which outscored the other methods based on selected criteria, obtained a score of 0.15 for environmental impacts. This number is the product of the number of points assigned by the MAUT code and the average criterion weight (as prescribed in Table 4.2):

Score (Wet cleaning) = MAUT (Env. Impact) x Weight = 0.82 x 0.1833 = 0.15

The same technique received a MAUT ranking of 1 for physicochemical hazards (meaning it is least hazardous of all considered alternatives). Considering the weight of that criterion of 13.75% we calculate:

Score (Wet cleaning) = MAUT (Phys-Chem) x Weight = 1 x 0.1375 = 0.1375 ~ 0.14

In spite of better performance of wet cleaning on this criterion, its weighted score is lower than that obtained for the environmental impact, because of the lower weighing factor put on this category.

Since chemical products are present in virtually any sphere of technology, we can find numerous examples of studies and innovations that illustrate the application of green chemistry principles. Some of them are given below. In the end of this lesson, you will be asked to research one of these cases (of your choice) in more detail and to provide a brief evaluation of its promise.

A. Innovative propylene oxide process

Companies DOW and BASF jointly developed a technology of conversion of hydrogen peroxide into propylene oxide (HPPO) that has significant "green" advantages over competing technologies:

• It uses hydrogen peroxide and propylene as raw materials, producing only propylene oxide and water.
• It reduces waste water by 70-80%.
• It uses 35% less energy.
• Its capital cost is 25% less.
• It avoids need for co-product infrastructure and markets.

Source: www.epa.gov

B. Advanced amine technology for carbon capture

Alstom-DOW pilot plant captures CO2 from new or existing industrial facilities with an improved sustainability profile:

• Pilot plant in West Virginia is designed to capture 1,800 tons CO2 per year.
• Advanced Amine process leads the industry in carbon capture efficiency.
• Capture rate ~90% with 99.5% purity of CO2.
• Process significantly reduces parasitic energy requirements.

Source: Pump Industry Analyst, 2009

C. Metathesis catalysis for making high-performing, green specialty chemicals at advantageous costs

Elevance employs Nobel-prize-winning catalyst technology to break down natural oils and recombine the fragments into novel, high performance green chemicals. These chemicals combine the benefits of both petrochemicals and biobased chemicals. Elevance produces specialty chemicals for many uses, e.g., concentrated cold-water detergents that provide better cleaning with reduced energy costs.

• Significant energy savings
• Reduction of greenhouse gas emissions by 50% (compared to petrochemical technologies)

Source: ACS

D. An efficient biocatalytic process to manufacture simvastatin

Simvastatin, a leading drug for treating high cholesterol, is manufactured from a natural product. The traditional multistep synthesis was wasteful and used large amounts of hazardous reagents. Professor Y. Tang (UCLA) conceived a synthesis using an engineered enzyme and a practical low-cost feedstock. Codexis optimized both the enzyme and the chemical process.

• great reduction of hazard
• less amount of waste
• cost-effective approach
• better meets needs of customers

Some manufacturers in Europe and India use this process to make Simvastatin.

Source: ACS

E. Enzymes save energy and wood fiber for manufacturing high-quality paper and paperboard

Traditionally, making strong paper required costly wood pulp, energy-intensive treatment, or chemical additives. But that may change. Buckman’s Maximyze®enzymes modify the cellulose in wood to increase the number of "fibrils" that bind the wood fibers to each other, thus making paper with improved strength and quality − without additional chemicals or energy. Buckman's process also allows papermaking with less wood fiber and higher percentages of recycled paper, enabling a single plant to save $1 million per year.

Source: ACS

F. Gas-expanded liquids for sustainable catalysis

Gas-expanded liquid (GXL) is a substance generated by dissolving a compressible gas (for example, CO₂ or a light olefin) in a regular liquid substance at mild pressures (tens of bar). When CO₂ is used as the expansion gas, this process produces CO₂-expanded liquid (CXL). An attractive feature of GXLs is that they combine the advantages of compressed gases and of traditional solvents. GXLs retain the beneficial attributes of the conventional solvent (polarity, catalyst/reactant solubility) but provide higher miscibility of permanent gases (O₂, H₂, CO, etc.), as compared to organic solvents at ambient conditions. GXLs also results in enhanced transport rates compared to regular liquid solvents. The enhanced gas solubility in GXLs have been exploited to alleviate gas starvation (often encountered in homogeneous catalysis with conventional solvents). Environmental advantages of GXL include:

• replacement of harmful organic solvents with environmentally benign CO₂;
• reduced flammability due to CO₂ presence in the vapor phase;
• lower process pressures (tens of bar) compared to supercritical CO₂ (hundreds of bar) which is linked to energy savings.

GXLs thus have many characteristics of an ideal alternative solvent.

Source: Anastas and Zimmerman, 2013, pp. 5-36. (This book is available online through the Penn State Library system.)

G. Synthesis of magnetite (Fe₃O₄) nanoparticles "green" way

Shape-controlling studies of magnetite nanomaterials are pursued actively since their magnetic and electrochemical properties, as well as their catalytic activities, greatly depend on their nanostructures. As catalysts, Fe₃O₄ nanoparticles possess some advantages over natural enzymes (e.g., horseradish peroxidase, HRP) because (i) they can maintain relatively high catalytic activities under a wide range of environmental changes, even in severe conditions (pH = 2–7, 70 °C) and (ii) their preparation and purification procedures are reproducible and cheaper than those of natural enzymes. The robustness, repeatability, and low price of Fe₃O₄ nanoparticles make them suitable as catalysts for H₂O₂ oxidation for a broad range of applications in biotechnology and environmental chemistry.

However, the synthesis of Fe₃O₄ nanoparticles with controlled morphology is still a challenge. Current approaches, such as a hydrothermal process, solvothermal process, and thermal decomposition, involve toxic sources (e.g., organic solvents and surfactants), rigorous conditions (high temperature, high pressure), and tedious synthetic procedures, which prevent the large-scale production and widespread practical applications of Fe₃O₄ nanoparticles. Additionally, the recovery of Fe₃O₄ nanoparticles for repeated use is still difficult. Therefore, nontoxic, water-based approaches for the fabrication of morphology controllable Fe₃O₄ nanoparticles, which can be produced on a large-scale and effectively recovered, are urgently needed.

This article introduces a new straightforward approach developed for fabricating Fe₃O₄ nanoparticles/hydrogel magnetic nanocomposites, in which the morphology of the nanoparticles can be controlled under nontoxic and water-based conditions. The 3D hydrogel networks, which contain a liquid-like microenvironment facilitating small molecule diffusion and transport, can act as an ideal nano/micro-reactor but also as a great carrier for the synthesis and immobilization of nanoparticles. This study was inspired by magnetotactic bacteria, which are capable of producing bacterial magnetic particles (BacMPs) with a highly controlled morphology (e.g., nanocube, nanooctahedron, and nanododecahedron) due to their nanoscaled magnetosome vesicles acting as nanoreactors, and negatively charged proteins playing the role of iron ion-binding sites. With a higher catalytic activity, the magnetic nanocomposite loaded with Fe₃O₄ nanooctahedra has a sensitive response towards H₂O₂ detection with a limit of 5 × 10⁻⁶ mol L⁻¹.

An additional benefit of this work is that the magnetic nanocomposite can be recovered more effectively and easily using the hydrogel as a carrier. "Based on the facile, economical fabrication strategy, large-scale production of this magnetic nanocomposite with a tunable peroxidase-like activity can be expected to revolutionize catalysis applications in biotechnology and environmental chemistry."

Source: Geo et al., 2013

Assignment Details

At the end of this lesson, you will be asked to choose one of the above cases or any other you may find on the Internet for more detailed evaluation. More information can be found on the Lesson 4 Activity Sheet on Canvas.

Multifunctional materials are the materials that perform multiple functions in a system due to their specific properties. Multifunctional materials can be both naturally existing and specially engineered.

For example, some traditional materials that provide, for instance, high mechanical strength can be modified at the nanoscale to attain other properties such as energy absorption, self-healing, etc. The applications of such new "smart" materials include energy, medicine, nanoelectronics, aerospace, defense, semiconductor, and other industries.

Numerous examples of multifunctional materials can be found in nature. Bio-materials routinely contain sensing, healing, actuation, and other functions built into the primary structures of an organism. For example, the human skin consists of many layers of cells, each of which contains oil and perspiration glands, sensory receptors, hair follicles, blood vessels, and other components with functions other than providing the basic structure and protection for the internal organs. Through biological evolution, these structures were seamlessly integrated into the body to serve their functions (Nemat-Naser et al., 2005).

The ability for materials to respond to their environment in a useful manner has broad technological impact. Such "smart" systems are being developed in which material properties (such as optical, electrical, or mechanical characteristics) respond to external stimuli. Materials of this kind have tremendous potential to impact new system performance by reducing size, weight, cost, power consumption, and complexity while improving efficiency, safety, and versatility. The multifunctionality of materials often occurs at scales from nano through macro and on various temporal and compositional levels (Nemat-Nasser et al., 2005).

Innovative advanced materials make a direct and positive impact on economic growth, the environment, and quality of life. They allow for improved processes and products and create several avenues to increasing sustainability.

Note the following areas of impact:

1. reducing environmental effects
2. increasing efficiency of processes
3. lightening the weight of products
4. lowering power consumption
5. reducing system size
6. reducing system weight
7. reducing system cost
8. reducing complexity
9. increasing safety
10. increasing fuel flexibility
11. increasing versatility

Most of these impacts may result in higher efficiency of the system and cost savings.

Examples of advanced materials studies

The following are several examples of sustainable solutions through improved materials chemistry or using alternative innovative materials.

A. Power-generating structural composites

"Researchers at ITN Energy Systems and SRI International have integrated a power-generating function into fiber reinforced composites. Individual fibers are coated with cathodic, electrolytic, and anodic layers to create a battery. The use of the surface area of fibers as opposed to that of a foil in a thin film battery allows greater energy outputs, measured on the order of 50 Wh/kg in a carbon fiber reinforced epoxy laminate. These batteries may be deposited on various substrates, including glass, carbon, and metallic fibers."

Source: Nemat-Nasser, S., et al., Multifunctional Materials, Figure 12.2. in Biomimetics: Biologically Inspired Technologies, Bar-Cohen, Y., Ed., CRC Press, 2005. (This book is available online through the Penn State Library system.)

B. Thermostructural materials for gas turbines

Gas turbines are a core technology in aero-propulsion and industrial power generation. Technological progress in this area depends on advances in thermostructural materials. The requirements to reduce emissions, increase fuel flexibility, and resist environmental attack call for development of new material systems with multifunctional properties. University of California Santa Barbara researchers employ a holistic approach that embraces and integrates all critical aspects of materials technology, including alloys, coatings, and composites, processing, and simulations to create the thermostructural materials that combine mechanical strength and exceptional thermal stability. Materials issues relevant to the high-pressure turbine include higher temperature single crystal alloys that act in concert with coatings, advanced bond coat alloys for environmental protection with improved thermochemical and thermomechanical compatibility with the load-bearing alloy, and thermal barrier oxides with new compositions that enhance temperature capabilities. Ceramic matrix composites (CMCs) and associated environmental barrier coatings are also incorporated in next generation engines, especially for combustors.

C. Nanoparticle assembly using DNA strands

"Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed a general approach for combining different types of nanoparticles to produce large-scale composite materials with special properties. The approach takes advantage of the attractive pairing of complementary strands of synthetic DNA—based on the molecule that carries the genetic code in its sequence of matched bases known by the letters A, T, G, and C. After coating the nanoparticles with a chemically standardized "construction platform" and adding extender molecules to which DNA can easily bind, the scientists attach complementary lab-designed DNA strands to the two different kinds of nanoparticles they want to link up. The natural pairing of the matching strands then "self-assembles" the particles into a three-dimensional array consisting of billions of particles. Varying the length of the DNA linkers, their surface density on particles, and other factors gives scientists the ability to control and optimize different types of newly formed materials and their properties."

Source: Brookhaven National Laboratory

D. Organic batteries provide better recallability

A typical battery consists of two electrodes - anode and cathode, electrolyte layer, separator, and current collectors. Most of traditional battery technologies use metals or metal oxides as electrode-active materials, and metals are not renewable resources. This study describes the use of organic materials as electrodes. The advantage of such organic-based batteries over Li-ion batteries in terms of sustainability is improved recallability, safety, adaptability to wet fabrication process, and extraction of starting material from less limited resources. One recently developed type of organic battery is based on organic radical polymers - "aliphatic or nonconjugated redox polymers with organic robust radical pendant groups as the redox site". The organic batteries have lower energy density compared to Li-ion technology, but this limitation is expected to be overcome in the near future.

Source: Anastas, P.T., Zimmerman, J.B., Innovations in Green Chemistry and Green Engineering, Chapter 8, pp. 235-246. Springer 2013. (This book is available online through the Penn State Library system.)

Lesson 4 introduced a very wide topic - green chemistry - which covers numerous innovations in chemical process design, manufacturing, and materials. Chemistry penetrates almost every aspect of modern technology, so such questions as how the technological components are made, where the starting materials come from, and what happens to them through the lifecycle are pivotal points for decision makers looking for increasing sustainability. There are ongoing efforts in both the US and Europe to develop guidance for assessment of chemical technologies, and a variety of methodologies have been tested so far. There is no unified system of assessment, which is understandable considering the diversity of subjects within the area of green chemistry. What you should take home from this lesson is the understanding of main steps and principles, plus a list of key resources which can help with consistent analysis of emerging chemical technologies. This lesson activity provides you with hands-on practice of examination of a real-life case and should stimulate some critical thinking with respect to what works and what does not in the recommended assessment protocols.

References for Lesson 4:

The waste management technologies are critically important when we try to visualize a sustainable society. In the growing world, a huge share of the output of the industrial processes and society living is waste, which has a dramatic impact on the environment. Turning the "linear" production economy to a "closed-loop" no-waste economy is a primary task underlined by sustainable design principles. And new designs and new technologies can have a big role in this process both at the local and national level.

There are two issues in resource management story: (1) resource conservation and (2) pollution prevention. When natural resources are extracted and turned into products via a manufacturing process, they become involved in a linear lifecycle - cradle-to-grave. If there is a constant demand for the product, more resources will be extracted, more product manufactured, and more end-of-cycle refuse generated. The limitation associated with the first issue is eventual depletion of the resource (especially if it is non-renewable). The limitation associated with the second issue is reaching the environmental capacity for holding or absorbing the "death" products. These limitations create potential for crisis, which has to be addressed in order to reach system sustainability.

In this lesson, we will take a look at some technologies that seem promising along those lines.

Learning Objectives

By the end of this lesson, you should be able to:

• understand and explain the key sustainable technologies in waste management;
• discuss the closed-loop recycling and zero-waste philosophy principles;
• apply life cycle thinking to waste management systems;
• demonstrate some ways to measure the technical performance of waste management processes.

Readings

1. Book chapters: Solid Waste Technology & Management, Christensen, T., Ed., Wiley and Sons., 2011. Chapters 1.1; 3.1; 3.2. (See E-Reserves in Canvas.)
2. EPA Document: Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2011, US EPA 2012.
3. Journal article: Seeberger, J., et al., Special Report: E-Waste Management in the United States and Public Health Implications, Journal of Environmental Health, vol. 79, pp. 8-16 (2016).
4. Website: Types of Composting, US Environmental Protection Agency, 2013.
5. Web Article: Lozanova, S., Are Solar Panels Recyclable, Earth 911, 2018.
6. Web Article: Marsh, J., Recycling Solar Panels in 2018, EnergySage, 2018.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

"In order for something to become clean, something else must become dirty…

But you can get everything dirty without getting anything clean."

--Imbesi's Law of the Conservation of Filth with Freeman’s Extension (Dictionary of Proverbs, Ed. Kleiser, S.B.N. A.P.N. Publishing 2005)

The starting point for this lesson is a general overview of the waste management industry. The following reading will introduce you to the main issues related to waste generation, disposal, recycling, and related problems.

So, how is the problem of waste disposal currently handled? There are a number of established technologies that help remove discarded materials out of our sight. Some of those discarded materials are reused in some form, but much larger amount is dumped or buried in the environment, which creates contained pollution. But is it really contained? And is that practice sustainable?

Watch the following video, which tours waste management facilities near San Francisco. That gives you an idea of the scale of waste accumulation in urban areas and shows what it takes to treat it:

Video: Waste Management and Recycling (9:29)

This is how numerous facilities around US currently operate. For the most part, it is so-called cradle-to-grave scheme, when discarded products and waste are recycled to typically lower grade material (i.e., down-cycled) or packed in a landfill. According to EPA, more than 50% of generated solid waste in the US is discarded, i.e., disposed of in the landfill. The following material is an EPA document showing some concrete numbers, which demonstrate how developing recycling technologies help reverse the trend in waste generation.

Answer the following question to check your learning of this section.

Credit: Zaf via Wikimedia Commons

As we can see from the previous page of this lesson, there are a number of conventional methods of waste treatment which depend on the system scale and type of waste. However, not all of them fit in the sustainability picture. For example, such common methods as incineration or landfilling are not sustainable solutions because, while eliminating problem in one zone (for example, human residence or industrial facility), they create additional pollution in the other (atmosphere, soil, aquifers, natural habitat). The purpose of recycling is to minimize or completely avoid sending waste to landfill or incinerator.

There are two major stages in recycling strategy: collection and processing. Both may consume resources and limit the process efficiency. The main recyclables are metals, plastics, glass, paper, and wood. Those materials are common in consumer products, so the public needs to be involved in the process. Public acceptance is important for the success of recollection of those recyclable materials (for example, public awareness and availability of collection points in public places plays a role – see image above). At the stage of processing, the question of recyclability is often related to the product design. How difficult and expensive is it to retrieve those materials from the product? You need to get those materials separated in a pure form in order to make them reusable in the same or new products.

Some skeptical questions we can often hear from the public are: Is recycling really worth it? Would the energy spent on recycling collection, transportation, and processing offset the benefits of the process? Would the emissions associated with that recycling exceed the overall environmental impact of the original trash? Those questions are good to contemplate on and the answers would require a deeper look into the lifecycle of materials.

To refute those commonplace skeptical arguments, the Environmental Protection Agency (EPA) provides some clear evidence on the benefits of recycling to the planet. Here are just a few facts:

• Recycling aluminum cans saves 95% of the energy needed to make new cans from raw aluminum ore;
• Recycling steel cans saves around 60% of energy;
• Recycling paper saves on the average 60% of energy
• Recycling plastic saves about 75% of energy;
• Recycling glass saves about 20-35% of the energy compared to making those products from virgin materials. In fact, the energy saved by recycling one glass bottle will operate a 100 watt light bulb for four hours
• Recycling helps reduce litter, thus mitigating the spread of bacterial or fungal infections.
• Among the social benefits is creation of jobs: ~1.25 million in the United States alone.

It is important to realize that recycling is far from being a universal remedy to the world’s pollution problems, however most experts say it is an important component in the systemic response to the environmental global change, pollution, and other serious issues of this century. [Howard, B.C., 5 Recycling Myths Busted, National Geographic 2018].

Recycling indeed helps to save energy, resources, and prevent greenhouse gas emissions on the lifecycle scale. You can look up more numbers on the Popular Mechanics website which compares recycling rates for aluminum, glass, newsprint, and some plastics, and links those data to market trends.

As seen from this information, an important factor responsible of viability of recycling business is the cost of the new material production. For example, production of virgin aluminum by bauxite mining is so energy-demanding that recycling of drink cans is very economically attractive. On the contrary, glass recycling, while technically simple, does not bring such high benefits, just because making new glass from silica sand is a relatively cheap technology.

Another factor that affects the viability of recycling system is collectability. Plastic recycling is quite profitable, with 76% energy savings compared to new plastic production. However, the case of polystyrene containers shows that if there is no technology to efficiently separate them from other plastics, process fails.

The bottom line here is that recycling heavily relies on development of new advanced technologies and approaches for material processing (without quality loss), collection, and sorting recyclables.

Unfortunately, many cases of recycling only help postpone permanent waste generation. This happens if an original material gradually loses its quality while being recycled and cannot return to the same manufacturing process. It has to be reprocessed to lower-grade products, which are not necessarily recyclable. For example, recycling of polyester soda bottles results in obtaining polymer fibers, which may be supplied to a carpet manufacturer. Carpet, however, is not easily recyclable since it is a more complex product. Polymeric fabrics are combined with other organic products and adhesives to make the final product. Separation of pure components after its use is not feasible; hence, the used carpet becomes a landfill material. This way of recycling, when a material lives a few lives but becomes less and less usable or pure or safe along its way to the landfill, is often termed "downcycling". In terms of sustainability, it means being "less bad", but still not good enough.

At this point, it would be appropriate to look at different concepts in material recycling.

Open-loop Recycling

Open-loop recycling basically means that a material is not recycled indefinitely and is eventually excluded from the utilization loop and becomes waste. The diagram in Figure 5.1. shows a material flow through the linear (open-loop) system. In this representation, stocks are shown with rectangular boxes, and transforming processes are shown by hexagon boxes.

In Figure 5.1. below, we see that natural resources extracted from the environment are transformed into a product via manufacturing process. After its use, the product may be discarded as one of the outputs: (a) whole product that is not needed anymore, (b) whole product that became obsolete (although still functional), (c) non-functional or old product because of its limited lifetime, (d) recyclable / reusable parts or scrapped materials, and (e) non-recyclable refuse. Those outputs enter one of the post-use channels – reuse, recycle, and garbage disposal, the latter contributing to the landfill. Reuse channel is usually limited, just postponing garbage disposal. Recycling loop results in producing another material, which is typically of lower grade and purity than the original material. It may be transformed further into a different product, which after use creates similar outputs. In the long run, a small part of the original resource may be stuck in the loop, but the majority of it becomes disposed of.

Figure 5.1. Open-loop material flow (“cradle-to-grave”). A major bulk of materials sooner or later contributes to the landfill disposal. Only a fraction of material is recycled indefinitely.

Credit: Mark Fedkin

The bottom line is: even if recycling and reuse are involved, eventual down-grading renders material non-usable, and it contributes to waste generation in the end of the lifecycle. Open-loop recycling postpones disposal and slows down extraction of new natural resources, but does not provide an ultimate solution to the problem.

Closed-loop Recycling

Closed-loop recycling is a more sustainable concept, which means that recycling of a material can be done indefinitely without degradation of properties. In this case, conversion of the used product back to raw material allows repeated making of the same product over and over again.

A few things to consider:

• The recycled materials should provide the same quality of the product (no deterioration). For example, almost all recycled aluminum from soda cans is suitable to produce the same cans.
• There should be no accumulation of contaminants or toxins in the multiple recycling loop, which can make the secondary product less safe.
• The recycled material can also feed a manufacturing process for a different product or industry, which may require a different type of recycling.

The other part of closed-loop recycling concept is biodegradable disposal. Everything that cannot be recycled or comes as a by-product in the manufacturing process should return to the environment with no harm. The diagram in Figure 5.2 summarizes the above considerations. While starting from the same extraction, manufacturing, and use stages, the outputs in the closed-loop scheme become equally usable resource for the manufacturing chain. Greater fraction of materials should be designed for recycling and reuse. The refuse that is inevitable is biodegradable and brings no harm when returned to the environment.

Figure 5.2. Closed-loop material flow. In ideal case no permanent solid waste is generated – all materials are returned as nutrients for natural or technical food chains.

Credit: Mark Fedkin

In any sustainability scenario, closed-loop approach is the goal. But it would take radical changes and innovative thinking at the level of product and process design.

To a greater extent, this closed loop thinking is advocated in the book of William McDonough and Michael Braungart “Cradle-to-Cradle”. The authors suggest that every product and all packaging should have a complete closed-loop cycle mapped out for each component, i.e., pathways should be identified for each component to either be recycled indefinitely or to return to the natural ecosystem.

Zero Waste Strategy

When closed-loop resource management is successfully implemented, we ideally should have zero waste produced, as all products at the end of their lifecycle become assimilated by either technical or natural systems to their benefit. In a wider context, zero waste thinking also covers zero emission and zero water pollution. Such targets seem ambitious and require careful life cycle analysis of all steps.

Zero waste concept responds to the principle #6 of sustainable design, "Eliminate the concept of waste. Evaluate and optimize the full life-cycle of products and processes, to approach the state of natural systems, in which there is no waste" [The Hannover Principles., 1992]

"Zero waste philosophy encourages the redesign of resource life cycles so that all products are reused. No trash is sent to landfills and incinerators. The process recommended is one similar to the way that resources are reused in nature." [Source: Wikipedia Zero Waste Article - read this Wikipedia article to learn more about the historical development of this concept].

Zero-waste strategy supports sustainable development through the following pathways:

• Environmental sustainability:
  • conservation of natural resources
  • minimization of non-degradable waste dumped to the natural ecosystems
• Economic sustainability:
  • less waste = higher efficiency => lower cost
  • cost of compliance with regulations is reduced
• Social sustainability:
  • generation of new jobs
  • more resources and energy become available for society

Source: Zero Waste Alliance

It should be noted, however, that zero-waste concept is not equivalent to closed-loop recycling in technical sense. It involves and relies heavily on the design of systems for reuse of products and resources without additional energy and labor expenditures, which are usually required for classic recycling.

We understand that recycling materials from the waste stream helps to conserve resources. But the question often arises: How much material can be actually recovered, and is it worth spending energy and labor for it, or it is easier to extract fresh material from the environment? A useful metric to characterize technical performance of a recycling line is recycling efficiency. The general approach to estimate efficiency is as follows:

1. Determine the input of the process: Input is measured as the mass or volume of all fractions or materials entering the recycling process per time period (usually per year) - m_i(in)
2. Determine the output of the process: Output includes the mass of the useful recycled components - m_i(out), excluding any unrecycled material sent to refuse. Loss of the components to the refuse can be due to process inefficiencies, such as sorting losses, damages or loss of quality, loss of slag and emissions, accidental presence of non-recyclable items.
3. Calculate the efficiency ratio (η) as follows:

$$\eta =\frac{{\displaystyle \sum m_i(out) }}{{\displaystyle \sum m_i(in) }}\times 100\%$$

Example

Consider the case of recycling Pb-acid batteries. Input will include lead metal (Pb) together with liquids and other solids contained in a battery and also the external jacket. Let us count recovered Pb as useful output, but any chemicals that cannot be salvaged and must be disposed off are not included. Then efficiency of lead recovery can be estimated as: η = m_Pb(out) / m_i(in) x 100%

Let us imagine that a small recycling facility treats 13,000 kg of old batteries per year. If the amount of the recovered lead is for example 7,000 kg per year, then
η = 7,000 / 13,000 × 100% = 54%

That means that the other 46% of material supplied to the recycling process is lost or discarded (e.g., non-recyclable acid and other chemicals, slag, etc.). Note, the above numbers are randomly picked and used merely for example.

100% efficiency is possible only in the ideal case when no waste is sent to the landfill or incineration.

Source: adopted from the method described in the EU Commission Regulation 6/11/2012

1942 Poster encouraging prevention of food waste.

Credit: Public Domain, US National Archives via Wikimedia Commons

Food waste accounts for 14.5% of all generated waste in the US according to EPA report, and only a small portion of it is recovered (1.6%). At the same time, food waste contains loads of nutrients that can be returned to the environment, but it should be done the right way. Disposing of the organic waste in the landfill results in the generation of methane, which can pose a threat or contribute to the greenhouse effect. Hence, developing composting technologies is an important part of a sustainable waste management system.

Compost is a stable organic mixture resulting from the breakdown of organic components; it is typically dark brown or black and contains humus which provides a soil-like, earthy smell. Compost is widely used as fertilizer and soil amendment in agriculture. It is created by piling organic wastes (garden waste, leaves, food waste, manure) with bulking agents (e.g., wood chips) to provide an environment for anaerobic bacteria and fungi to manage the chemical decomposition process. Compost is stabilized through maturation and curing process.

According to US EPA, there are a number of benefits of the composting process. These include:

• reduction and elimination of the need for chemical fertilizers;
• increasing of crop yields;
• facilitation of reforestation, wetland restoration, and habitat revitalization by amending contaminated, compacted, and marginal soils;
• cost-effective remediation of soils contaminated by hazardous waste;
• absorption and removal of solids, oil, grease, and heavy metals from stormwater runoff;
• avoidance of methane and leachate formation in landfills;
• decreased need for water, fertilizers, and pesticides in agriculture;
• serving as a marketable commodity and as a low-cost alternative to standard landfill cover;
• capturing and destruction of 99.6 percent of industrial volatile organic chemicals (VOCs) in contaminated air;
• more cost-effective soil, water, and air remediation compared to conventional technologies;
• extension of municipal landfill life by diverting organic materials from landfills.

Certain physical conditions need to be provided for proper composting process. There are different types of processes, which are overviewed in the following reading.

Watch this short video that illustrates an industrial-scale composting facility in the UK. This is only one of the ways to do it. Which type of composting (from those listed by EPA) is this facility using?

Video: Hi-Tech Composting Plant (5:40)

While having obvious benefits, composting is far from being environmentally clean. When organic components are mixed and concentrated during waste collection, they create aggressive gases and liquid effluents, which should be carefully controlled. In the diagram in Figure 5.3. The side inputs and outputs accompanying the composting process are shown. The pre-composting weighing and pre-processing stages generate liquid leachate, gas exhausts, and solid residue as by-products. The composting stage requires input of air and water, while generating more potentially polluting exhaust and effluents. Some of the residue is reusable, but some is not and need to be disposed of as non-recyclable waste.

Figure 5.3. Composting flow diagram describing stages to produce marketable compost product.

Credit: Mark Fedkin (modified after Christensen, 2010)

Criteria that usually play a role in environmental and economic assessment of composting process are: energy use, transportation, land use, air quality. An example of multi-criteria analysis is presented in the “composting versus landfill case study, referenced below:

Examples of e-waste

Credit: : Mosman Council via Flickr

There are reasons to separate the electronics waste stream:

• rapid growth of the electronic manufacturing volume, market, and rapid change in technology resulting in new products
• complexity of electronic products, which requires special approach in recycling
• use of rare and precious metals and compounds, many of which should be recovered
• presence of toxic chemicals and other substances of environmental concern
• opportunities of efficient material and component reuse

Electronics recycling, computers for instance, is essentially a process of breaking down the final product back to components (some of which can be reused) and initial raw materials (such as copper, gold, silver, other metals, plastics). Because of significant load of technological product with heavy metals and toxic compounds (e.g., mercury, cadmium, lead, flame retardants), discarded electronics are classified as hazardous waste. Hence, recycling also requires strict measures of environmental safety.

There are companies and government programs that take on the challenge of responsible recycling of electronic products; for example, watch this short video about how Liquid Technology helps companies manage their e-waste while protecting the environment from hazardous materials:

Video: How Does Computer Recycling Work? (1:17)

However, currently existing programs of sorting / disassembly are hardly sufficient. The problem is that current computer and other electronic products are not designed to be recycled. End-of-life disassembly and recovery of pure materials is a tedious and expensive process. Few companies manage to build an effective infrastructure for electronic recycling. Even if responsible recycling practices exist, they hardly keep up with growing market for electronics and accelerating e-waste accumulation pace.

Unfortunately, there are businesses that find it more profitable to export the electronic waste overseas to developing countries. This practice, highly non-sustainable on the global scale and harmful to local population and environment, is an ugly illustration of shifting the environmental burden from one part of the global system to another:

For example, this video contains graphic illustrations of such irresponsible “recycling”.

Video: Responsible e-waste recycling: Basel Action Network E-Waste Film (10:00)

So, what are possible sustainable solutions to address the root of the e-waste problem?

• Design devices with environmentally benign components and chemicals.
• Design computers and other fast-rotating systems easily recyclable (to cut cost and increase process efficiency).

• Design “product-of-service” programs. This is exemplified in the book Cradle-to-Cradle as follows:

  "Instead of assuming that all products are to be bought, owned, and disposed of by “consumers”, products containing valuable technical nutrients – cars, televisions, carpeting, computers, and refrigerators, for example – would be preconceived as services people want to enjoy. In this scenario, customers would effectively purchase a service of such a product for a defined user period – say, then thousand hours of television viewing, rather than the television itself. They would not be paying for complex materials that they won’t be able to use after a product’s current life. When they finish with the product, or are simply ready to upgrade to a newer version, the manufacturer replaces it, taking the old model back, breaking it down, and using its complex materials as food for new products." [McDonough and Braungart, 2002]

Currently in the US, many states have active policies to regulate the e-waste. Different models suggest imposing fees to finance e-waste recycling onto various entities – consumers, manufacturers, municipalities. There are also different mechanisms to facilitate collection and processing of the e-waste. Some examples are given in the following reading:

- The Next Big Thing on the Trash List – Solar?

Solar power is probably the fastest-growing market in the world. According to Solar Energy Industries Association (SEIA), in the past decade, solar power industry experienced an average annual growth rate of ~59%. An estimated 500,000 solar panels were installed globally every day in 2015. If we think of rooftops, a typical American home would require 28 to 34 solar panels to cover its power consumption. The U.S. Department of Energy forecasted that by 2050, the U.S. will have cumulatively installed 700 GW of solar, or hundreds of billions of PV modules [Mulvaney, 2015].

But here is the question: What will happen to the billions of those solar panels now spreading across the globe at the end of their useful lives?

Rapid growth of photovoltaic installations over the past decade requires radical action for establishing a robust and economically viable PV disposal and recycling system. 

Credit: Oregon Department of Transportation via Flickr

On the average, solar photovoltaic (PV) modules have a useful lifespan of 25-30 years, so with the current growth rates, the first peak of PV waste can be expected around 2030. And there is still some time to plan ahead. Now, as we know how externalities have magnified due to the lack of foresight with fossil fuels, there is an opportunity to do things right with solar.

As the photovoltaic panels contain a variety of valuable metals and materials, which are mined and refined at increasing rates, it is imperative to create recycling methodologies, infrastructure, and policies to maintain the flow of those materials within the industry. This important action would address two problems – waste regulation and resource depletion.

What are the current US domestic programs designed to address the growing PV waste flow? Until recently, the regulations on PV waste did not exist in the USA, except California. However, things have to change soon. In lieu of introduction to this problem, the video below talks about some of the emerging options and initiatives, many of which utilize the successful experience of the European recycling programs:

Video: Solar Basics: How to plan ahead for U.S. solar panel recycling (3:15)

There are a number of recyclable components included in PV module – some of those are rare, and some of those are toxic and thus require a proactive plan for recycling. Crystalline Si PV modules, in addition to silicon, contain materials such copper, aluminum, silver, and glass. CdTe PV modules contain cadmium, steel, and copper. Metal components are usually much more expensive than non-metal materials, and extracting them during recycling process and reusing in manufacturing brings sensible economic benefits. Materials such as silicon wafers are critical to recycle, as a substantial amount of energy is spent to purify them for use in PV modules. Thin-film modules contain such elements as tellurium, indium, gallium, and molybdenum, which are in limited supply in the Earth’s crust. Indium is the element that will face resource use competition between solar and flat-screen displays. [Williams, B., 2016]

More education on this topic - the following webinar (by International Solar Energy Society - ISES) presents an extended overview of PV recycling practices, policies, and current research innovations around the world. The first talk is more on the legal background and policies existing in different countries. The second presentation explores the way to incorporate PV panel reuse practice in circular economy. The last presentation in the webinar goes deeper into the weeds of the recycling process itself. You will see the actual equipment used for the mechanical, chemical, and thermal extraction of materials from the discarded panels.

Video: ISES Webinar: PV Recycling and End of life Processing (1:22:01)

If you want more insight in the process of recovering of specific elements and design of the material flow, this article provides a comparative analysis of recycling of two types of PV panels - Deutsche Solar and First Solar - including LCA considerations and cost analysis.

The presented analysis and modeling shows that using the external recycling facilities as material source, the PV manufacturers can save on some costs. Joining a recycling association decreases the total cost of c-Si panels by 55.28% and CdTe panels by 2.28%.

References:

Mulvaney, D., Act Now To Handle The Coming Wave Of Toxic PV Waste, Solar Industry Mag 2015. Accessible from URL: https://solarindustrymag.com/

Williams, B., Photovoltaic (PV) Recycling, Final Project, EME 807 Technologies for Sustainability Systems, Renewable Energy and Sustainability Systems (RESS) Program, Penn State University, 2016.

Reuse is the second level of the national solid waste management hierarchy. Reuse is simply repeated using a product or component in its original form. For example, using a glass milk bottle multiple times within the producer – customer chain (instead of using a plastic bottle).

Reuse also means that materials and products are redistributed from one who no longer needs them to those who can still find use in the items. The benefit of reuse is not only in conservation of valuable natural resources, but also in getting materials and products to disadvantaged people and organizations.

US EPA provides grant funding to Reuse Development Organization Inc. (ReDO), a non-profit organization whose mission is "to promote reuse as an environmentally sound, socially beneficial, and economical means for managing surplus and discarded materials. The ReDO company website provides some background on the issue.

Program Soles4Souls redistributes mildly used shoes to schools in developing countries

Credit: Soles4Souls

Here are a few examples of successful material reuse programs, which attempt to divert the flow of useful resources from the waste stream:

1. "LIFT" reuse program accepts gently used equipment designed for persons with disabilities and redistributes it to people in need. They perform safety checks and sanitation of the donated items. The program accepts walkers, wheelchairs, transfer chairs, raised toilet seats, shower chairs, adapted telephones, low-vision aids, reachers, and any other equipment that helps with independence.
2. "Soles 4 Souls" nation-wide program that has a mission "fighting the devastating impact and perpetuation of poverty through the distribution of shoes and clothing... Most new items collected primarily from corporations and retailers are given directly to people in need, both in the U.S. and overseas. The organization has relationships with several of the world’s leading apparel brands, which provides Soles4Souls with new but non-marketable overstocks, returns, discontinued models and other shoes or clothing items."
3. Cooling pack reuse program: Employees of a medical facility initiated a program to divert reusable cooling packs from trash. Cooling packs are very common supplies that are used to keep the medical samples cooled for transportation. They were normally discarded once samples arrive at the facility, which has a stationary refrigeration system. The program established a few routes to reuse the packs while helping local food banks.

This week, in Lesson 5, you are learning about various methods to minimize waste and to avoid putting that additional burden on the environment. Recycling is often thought of as a smart way to deal with waste – something we have to do to reduce the mess that has already been made. However, the same as with green chemistry principles, thinking is being shifted now from dealing with consequences of dealing with the root cause. In fact, recycling should become a part of the product design, so that its efficiency is maximized, and maximum of valuable material included in the product is recovered. In this case, more focus is put on salvaging the resource, rather than just keeping stuff off the landfill.

This way of thinking becomes even more urgent when we realize that for new emerging technologies, we need significant amounts of earth’s minerals that are actually limited. Those critical minerals and materials become strategic stocks for industries producing electronics, batteries, clean energy, aerospace, and other technologies that are going through massive scale-up. Design of closed recycling loops for those minerals is also a strategic task for manufacturers, if they plan staying in business for prolong period of time. For example, recycling metals such as Li, Co, Ni, Mn, rare-earth metals, graphite will be critically important for meeting the demands for energy storage and renewable energy. Thus, recycling becomes not only a key part of waste management, but also an integral link in the so-called circular economy.

Circular Economy is a relatively new term, which I wanted to put on your radar in this lesson. It builds upon the zero-waste concept, but actually goes beyond that. While encompassing stages of product design, and recycling technology, it also assumes establishing new sustainable supply chains for critical materials and strong partnerships among all players in the circle.

The concept of circular economy is not something we suddenly invented. In the nature, we see cyclic processes for matter and energy transformation functioning for millennia. This is the system where waste (as we understand it in society) does not exist! One good example to give here is a tree!

Image credit:Two Brown Trees by Johannes Plenio is licensed by Pexels

The tree absorbs water and nutrients from the soil and grows branches, leaves, fruits, and seeds. The fruits and seeds become food for animals and birds. Leaves are engaged in the photosynthesis producing oxygen, which is used for breathing by organisms. When leaves fall to the ground and decompose, the resulting organic matter enriches the soil, which sustains the growth of other plants, and the tree itself. And then the cycle starts all over again.

Speaking of biomimicry: can we design a technical supply chain system in which all the outputs from one segment of the system become the inputs to another segment of the system, just like it happens in biological environment?

Please watch this short video to learn more about the circular economy concept:

Video: Circular Economy Explained (4:58)

This lesson homework assignment will be on the concept of circular economy. See the instructions on the Summary and Activity page of this lesson and in Module 5 in Canvas.

This lesson contains a significant amount of information on existing and developing methods of resource conservation and waste treatment. This information is mainly related to dealing with municipal waste and does not cover special types of waste such as nuclear or agricultural waste. Wastewater and sewage treatment is a separate topic that will be addressed in the next lesson. The general thought that summarizes this lesson is that treatment of waste is a dirty and expensive business - it is better to prevent it than clean it up. New technologies that would change the situation to a more sustainable world must involve transformative design innovations that increase the recyclability and biodegradability of the waste stream outputs. Life cycle thinking and modeling will help to identify the best scenarios for sustainable actions.

References

Overview

When we examine the sustainability profile of a particular community, we always have to look at the water system that sustains that community. Historically, people dwellings were associated with the sources of water: rivers, springs, or lakes. In modern times, the issue of water remains primary. We have more advanced technologies to extract and distribute water resources, and we have other technologies to utilize and treat water. Those technologies become key links in the universal water cycle, which involves both ecological and anthropogenic spheres. This lesson specifically focuses on the technological methods to provide efficiency for water supply and further to provide sustainability of water resources. Such technologies target the two growing problems - water resource depletion and water pollution. After touching on the background of water management systems, this lesson will direct you to the examples of lifecycle analysis, which helps identify the technologies with the higher promise for sustainability.

Learning objectives

By the end of this lesson, you should be able to:

• understand the water cycle, identify the main processes, and explain connections between natural and anthropogenic water paths;
• name and explain the key sustainable technologies in water management and wastewater treatment;
• estimate water use of anthropogenic systems;
• compare different water treatment technologies against environmental metrics and identify pros and cons of new alternatives.

Readings

• EPA Document: USEPA Water Conservation Plan Guidelines, EPA 1998, Appendix A: Water Conservation Measures, pp. 143-155.
• Journal article: Vorosmarty, C.J., Sahagian, D., Anthropogenic Disturbance of the Terrestrial Water Cycle, BioScience, vol. 50, pp.753-763.
• Journal article: Dhinadhayalan, M., Nema, A., Decentralized wastewater management - New concepts and innovative technological feasibility for developing countries, Sustain. Environ. Res., 22(1), 39-44 (2012).
• Journal article: Bonton, A., Bouchard, C., Barbeau, B., Jedrzejak, Comparative life cycle assessment of water treatment plants, Desalination 283, 42-54 (2012).

These articles are available online through PSU Library system - See the "Library Resources" / E-Reserves link in Canvas.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

Kissimmee River wetland area, Florida

Credit: South Florida Water Management District (via Flickr)

Water is often envisioned as the bloodstream of biosphere. It is a universal medium that is crucial for sustainability of both ecological and human societies. There is no substitute for water. More than 70% of the earth surface is covered by water. However, only 3% of this reserve is fresh water that can be used for human consumption. 90% of the earth's fresh water resources is contained in groundwater and ice, and only 10% is water is contained in surface reservoirs - rivers, lakes, wetlands, and streams. [Girard, 2013].

Although sustaining life is one of the main key purposes of the water, present-day agriculture and many industry branches heavily rely on the abundance of the water resource. For example, water is used as heat transport fluid in thermoelectric energy systems, such as nuclear and fossil fuel fired power plants and concentrating solar power farms. It is used as solvent and raw material in chemical manufacturing. Mining industry utilizes significant amount of water in hydraulic fracturing and oil recovery. Those industries are important parts of modern infrastructure; hence, the water demand must be met to keep the power and food production at the necessary level.

To plan sustainable utilization of water resources, we must understand how the water cycle works at the global and local scales. The amount of water on earth is finite, and the natural water cycle is a system that controls the circulation and redistribution of that resource. You must be familiar with the water cycle concept from your early science classes. But you can get a refresher from the following short video:

Video: Water Cycle | How the Hydrologic Cycle Works (6:46)

This quite general and deceivingly simple concept of water cycle has a number of limitations which are important to understand:

• Capacities of the reservoirs vary dramatically.
• Flow rates between the reservoirs vary dramatically (for example replenishment of a surface stream via precipitation can take days, while replenishment of a deep aquifer may take decades).
• This concept does not directly reflect possible delays or discontinuities.
• Cycle kinetics depends on climate, time of the year, and geographic location.
• This concept does not portray fluctuations in storage zones.

Annual evaporation from the ocean is about 80,000 cubic miles versus 15,000 cubic miles from the land. Given the amounts of water evaporated and precipitated are almost equal, the total amount of water exchanged between the atmosphere and the earth surface is about 95,000 cubic miles. Out of the water evaporated and then returned by rainstorms, 24,000 cubic miles fall on land as precipitation. The average annual precipitation over the land is 26 inches, but it is not evenly distributed. Arid locations may get under 1 inch of precipitation, whereas some others can get more than 400 inches. The total annual precipitation in the United States is about 30 inches per year, which accounts for about 4300 billion gallons per day. The total water flow from surface and subsurface sources is about 8.5 inches per year, i.e., about 1200 billion gallons a day. This amount is available for human use, including domestic, industrial, agricultural, and recreational use. Considering that the difference between precipitation and stream flow is -21.5 inches per year (3100 billion gallons per day), this amount is assumed to return to the atmosphere (through evaporation and transpiration). This returned volume roughly accounts for 70 % of the total water supply. [Source: USDA, 2001]

In nature, the hydrological cycle is well-balanced, and fluctuations of environmental water stocks are reversible. But when some of the parts of the system are interfered, resilience of the system may be jeopardized. This can happen when the anthropogenic water consumption cycle is plugged in to the natural water cycle. The main troubles currently experienced because of mismatch of the anthropogenic and natural cycles include:

• groundwater depletion;
• chemical pollution of surface waters and groundwaters;
• lake drying;
• droughts;
• desertification;
• eutrophication
• loss of habitat
• water and food shortages.

While the above-listed factors may have acute local effect, recent research also shows that large-scale hydraulic engineering produces global-scale impact on the earth's water cycle, raising the global sea level.

The idea of sustainability in water management implies matching the natural water cycle and technical (anthropogenic) water use cycle together with minimal damage and maximum mutual support. A new approach to integrated managing water resources is known as total water cycle management, where water supply, stormwater, and wastewater are all considered during the design process.

The diagram in Figure 6.1. presents the water cycle in terms of stocks and flows. It illustrates the connections between different natural processes and reservoirs and also introduces the anthropogenic water paths into the system. The diagram is quite busy, so it would be useful to walk through it step by step. The video embedded below provides commentary to different parts of the diagram and also shows the links where water-treatment technologies must be applied to provide compatibility between the environmental and anthropogenic spheres. While watching, you may need to switch to 'full-screen' and HD quality setting to better see smaller details.

Click on the image to view the large version

Video: Water Cycle Step by Step (8:37)

As you can see in the diagram in Figure 6.1, the boundaries between the natural and human-controlled water systems are where the sustainable water treatment technologies should come into action. The bottom line is that the role sustainable water technology is to reconcile the natural and anthropogenic cycles and to alleviate mutual harm and system misbalance.

The following list gives you some examples of possible actions that help to keep combined water system sustainable (can vary with location):

Water regime management

• keep the aquifer levels within appropriate range
• prevent flood damage in developed areas
• prevent excessive erosion

Water quality

• minimize the export of pollutants to surface water or groundwater
• minimize waterborne sediment loading
• minimize pollution from sewage protect existing vegetation

Water conservation

• control water extraction and use
• promote the use of rainwater and stormwater where such use does not adversely affect existing environmental values
• promote the reuse of wastewater effluent
• reduce irrigation requirements
• promote opportunities for localized supply

Water value

• enhance water related environmental values
• enhance water related recreational and cultural values
• add value while minimizing development costs

Many of these actions require efficient technologies of water control and water treatment. The following sections of this lesson provide you with some examples and technical details on current practice of water treatment and prospective technologies for the future.

Water use statistics

When water is extracted from the natural water cycle, where does it go?

Based on government statistics, a big part of it (~40%) is used for agricultural needs (e.g., irrigation for crops or livestock), around 47% is used for industrial needs (e.g., power generation, mining, etc.), and around 13% is going to public supply (e.g., domestic or commercial) (Figure 6.1). However, these numbers can vary with location. For example, in Minnesota, the majority of the water extracted is used for power generation, while in California, the dominating use is irrigation [USGS, 2015].

Figure 6.2. A breakdown of anthropogenic water use.

Source: USGS / Public Domain

Figure 6.3. Diverted water fills a channel for crop irrigation.

Source: Wikimedia Commons - Dan Ogle, USDA Natural Resources Conservation Service

Although residential water consumption accounts for a smaller fraction of the whole, domestic water economy is considered an important factor in urban sustainability. The overall domestic water use is expected to grow as world population grows.

According to the U.S. Geological Survey 2015 water census, daily per capita domestic water use in the U.S. was 82 gallons per day, which was an improvement from 88 gallons per day estimated in 2010 census, and 101 gallons per day in 1995 census. This value represents the national average, and the actual local water use can vary broadly - for instance, from 35 gpd in Connecticut to 186 gpd in Idaho [USGS, 2015].

Typical US home water use accounting is:

• Showers - 19.5%
• Washers - 22.1%
• Toilets - 18%
• Dishwashers - 1.5%
• Baths - 2.7%
• Leaks - 8.8%
• Faucets - 23.9%
• Other - 3.4%

One can estimate how much water they use at home with some simple online calculators:

• CSGNetwork - Water Consumption Calculator
• Water Footprint Calculator

Water Conservation strategies

As the population grows, so does the stress on available water resources. Hence, there are a number of water conservation strategies, with some of the most intuitive approaches being:

• Limiting the consumption: Application of policies, economics, and technologies help regulate the demand. Policies may include restrictions and bans on certain types of water use, standards for fixtures and appliances, enforcement on recycling, etc. Economic measures, such as setting prices for water consumption, typically make people more diligent about their water-related activities. Technological advances may help use less water for the same function (water-economy washers, toilets, etc.)
• Reuse and recycling: Designing systems for reuse and recirculation of water in both domestic and industrial applications are involved in this approach. For example, treated wastewater can be used for irrigation; or water can be recycled in certain types of car wash systems.
• Elimination of losses: Regulation, metering, water-sensitive design, and smart technology are key factors contributing to this strategy. Leak identification systems, smart controllers for water use are some of such conservation technologies.
• Pollution prevention: Less pollution creates more opportunity for water reuse and conserves natural water reserves. Regulatory policies are introduced on water discharging facilities. Also, numerous technologies exist to treat the effluents from domestic and industrial facilities.

Sustainability goals and growing demands for clean water require new solutions in water conservation and use. There are technologies in place; however, many existing methods sometimes have low efficiency and are prone to water losses. Some innovative approaches are overviewed in this Guardian article: "The new water technologies that could save the planet."

The technologies mentioned in this article work out a number of issues, such as scalability, cost, and efficiency. In sustainable development, we want the systems to be affordable and compact, not using too many resources. That makes them easy to implement in both urban and rural settings.

US EPA introduced a set of strategic practices and policies to water promote water conservation. There are three levels of control, which are summarized in Table 6.1 below. Level 1 measures represent the most basic practices, Level 2 measures are intermediate-level controls, and Level 3 lists more advanced strategies for water conservation. When organizations design their water conservation programs, they may start at Level 1 and gradually proceed to Levels 2 and 3:

Complete the following reading assignment to learn what each of the above-listed measures involves.

Sewage water before and after treatment.

Credit: Heike Hoffmann (via Flickr)

Water treatment technologies are designed to eliminate harmful effects of pollutants and natural substances to human health and environment. Within the blended water cycle (considered on page 6.1), these technologies are often placed at the transitions between the environment and human sphere to adapt the water quality.

For example, when water passes from the environmental source to the human consumption system, there is a possible risk to human health from some natural bacteria, chemical elements. Hence, natural water (from either surface or underground reservoir) needs to be purified to a certain standard. On the other end of the system, the water containing waste or substances resulting from the domestic, agricultural, or industrial activity must be cleaned before returning to the environmental pathways. If this is not done, harmful effects of concentrated pollutants can cause significant disturbance to the natural water ecology and escalate damage to both ecosystem and society in the long run. Some common effects of wastewater pollution include eutrophication (biological nutrient pollution; for example, releasing access of nitrogen and phosphorus —"overfeeding ecosystem"); oxygen depletion (due to oxidation of organic compounds); odor and aesthetic damage; proliferation of harmful bacteria, viruses, fungi in drinking water supply.

Centralized water treatment

Centralized water treatment approach implies treating large amounts of water at large rates in a "central" location and distributing that water via networks of pipelines, channels, and intermediate reservoirs. Centralized water treatment is largely implemented and maintained in major urban areas and in most parts of the developed world. Probably most of us primarily use the centralized treatment in our lives (maybe except some travel circumstances).

A couple of videos below describe large-scale water treatment systems that are designed to remove undesired contaminants from water.

This first video shows an example of how water is treated during its transfer from the environmental source to the drinking water supply:

Video: Water Treatment Plant Tour (5:26)

This second video illustrates the treatment of the wastewater generated by human activity before it is returned to the environment:

Video: Barry's Wastewater Treatment Tour (5:26)

As we can see from these videos, the design of a large-capacity water treatment plant is very complex and involves not one but many steps, each of those utilizing multiple technologies. It is not our goal to learn all of them in detail in one lesson. However, should you have a specific interest in this topic, the US EPA Wastewater Technology Fact Sheets web page can serve as a great resource for obtaining more technical information about them.

Depending on the degree of cleaning and purification, treated water can be reused for:

• irrigation of agricultural crops or landscape irrigation (e.g., schoolyards, golf courses, residential gardens);
• groundwater recharge;
• recreational use (e.g., lakes and ponds, fisheries, snowmaking, marsh enhancement);
• non-potable urban use (e.g., fire protection, air conditioning, toilet flushing);
• potable use;
• industrial use (e.g., cooling, process water).

The main concern in water reuse is to meet the water quality requirements for its intended use. Quality requirements are determined by federal, state, and regional regulatory authorities and may vary. The general guidelines by EPA with regards to the effluent from the wastewater treatment facilities are given in Table 6.2 below:

Here is an explanation of measures in this table if you are not familiar with the terms:

• BOD₅ is the amount of oxygen needed to oxidize organic matter in a water sample. The difference in oxygen content is usually measured over the time span of 5 days (that is the reason for subscript 5). For reference, water from a very clear source may have a BOD of less than 2 mg/L; sewage water may give readings above 100 mg/L; food processing wastes may have BOD of thousands.
• CBOD₅ is the amount of oxygen needed to oxidize carbonaceous organic matter (excluding nitrogen compounds)
• TSS is the amount of particulate matter (insoluble) present in a water sample, which is usually determined by filtering the solution and weighing the residue remaining on the filter.
• pH is the measure of acidity of solution in chemistry (defined as pH = -log[H+]). Acidic solutions, such as acid rain, may have pH around 1-2, relatively neutral solutions range within 5-9 (distilled water pH=7), and alkaline solutions have pH 10-14.

These limits determined by EPA are included in the government regulations, published in the Rules of Department of Natural Resources [CSR, 2014]. This document also contains extensive data on limitations imposed on the contents of the toxic element in water before it is reused or discharged in a certain way to the environment. Check Table A for the maximum tolerated concentrations of metals (p.24) and organics (p. 26). The toxicity requirements are especially relevant to industrial water use.

Chemical tests to determine the above metrics are used as controls at any wastewater treatment plant. Various technologies are developed to improve the treatment efficiency and to produce a cleaner effluent suitable for further use.

Engineered ecological systems for water treatment

Traditional water treatment plants accomplish an important function. However, these facilities themselves produce significant environmental impact by consuming energy, producing emissions, by-products, and waste to be disposed of. Later in this lesson, an example is given for a life cycle assessment study which analyzes the way to make these systems more benign.

One of the trends in improving the environmental profile of wastewater treatment facilities is the design of ecological systems that mimic natural processes of neutralizing the pollution.

Installation of Living Machine system in the Vermont highway rest area.

Credit: Ed Bolton (via Flickr)

Here are a couple of examples of the development of such systems:

• Living Machine and Biomatrix systems (see photo above):
• Eco-Machines systems - ecological fluidized bed, or a small constructed wetland

These examples show that ecological treatment systems typically work at the small scale being capable to treat liquid waste from a community of 300-1000 people. This makes them attractive for decentralized treatment for secluded autonomous areas.

Decentralized systems for water treatment

Decentralized systems of water purification often become technologies of choice in developing countries because they do not require huge infrastructure or can be set up quicker when infrastructure is destroyed. Small-scale technologies provide quick response to urgent needs. There are multiple ways to approach the issue. Here is one of them: watch this 10 min video to see an example how small-scale technology can help solve large-scale problems.

Video: How to make filthy water drinkable (9:13)

Click on the link below to read about some small innovations that make big difference when applied at the right place at the right time:
6 Water-purifying Devices for Clean Drinking Water in the Developing World

Now, as we have a long list and various scales of water treatment technologies, sustainability goals require their careful assessment in terms of environmental, economic, and social effectiveness. LCA analysis is a very common tool to select specific technologies for a particular sustainability system. Note that specific location, hydrological profile, and available infrastructure are pivoting factors in such assessment. LCA cannot be general - it has to be case-specific. Therefore, it would be best for us to consider a specific example that would describe LCA for a particular prospective water treatment technology.

This real-life LCA project shows that proper assessment requires a great deal of technical detail and a significant amount of data. As a matter of fact, the authors had to perform an autopsy of system components to enlist all included chemical components with their potential environmental impacts at the stage of system manufacturing. Furthermore, operational data have to be closely tied to the specific demographic and geographic setting and the scale of application.

An additional thought on LCA: The output of LCA is quantified environmental impact, so it is most effectively used to compare alternatives - different products, systems, technologies, or methods. It has much less value when performed for a single product or a single technology since, without a clear reference point (a baseline), it is hard to tell if the impact small, large, or catastrophic, if the alternative brings improvement or makes things worse. Zero impact is probably not a good reference because no such ideal technology possibly exists. LCA also allows identifying the relative magnitude of various impacts. For example, we can determine if there is a particular project has a higher contribution to greenhouse gas emissions or to soil contamination, etc. In turn, this would help direct the mitigation measures - actions to reduce impact by redesigning the system, improving the process, or searching for an alternative.

This lesson drew some connections between the global water resources and human needs for water. With the fast-growing population and fresh water needs, the balance in the hydrologic cycle and pollution of water resources become critical issues. While there are technologies in place to adapt natural water for human use and to adapt the human-used water for environmental use, their capacity and effectiveness are not always sufficient. Water conservation and reuse are other important strategies to complement the combined water cycle. Sustainable water management implies the systematic approach to the water resources and considers anthropogenic water flows and storages as parts of the universal water cycle. Because there is no substitute for water (like, for example, substitutes for fossil fuels), societies will continue demanding water in great amounts. Therefore, water management and treatment technologies will continue being top priority, and innovation in this area will play a key role in sustainability.

While there are many hot topics to review in this area (we did it to some extent and you should feel free to explore more background on your own), our main focus in this lesson is to learn how to evaluate prospective technologies based on the available information. This may be not a simple exercise, but rather a quite complex practical task. That is why it is important to tap into real-world studies and learn from them. Activities in this lesson give you some scenarios to work with and will hopefully provide you with some practice of evaluatory thinking.

References for Lesson 6:

Overview

Buildings are one of the most important elements of human societies, and the question of building sustainability is the key question in the context of development and lifestyle of any civilization. Buildings are recognized as the main energy-consuming systems and as one of the high performing greenhouse gas emitters. Furthermore, because people in Western society spend most of their time indoors, buildings have a strong impact on human health and well-being. Multiple issues and criteria of sustainable building design and operation are introduced in this lesson. Following the assigned readings, you will engage in forum discussion and will be asked to perform an activity focusing on the analysis of some of the metrics used in building evaluation.

Objectives

By the end of this lesson, you should be able to:

• understand the principles under sustainable building design;
• list the rating criteria for determining the environmental quality of buildings;
• apply metrics to building analysis and propose scenarios for improvement.

Reading Materials:

• Book: Green Building: Project Planning and Cost Estimating, RSMeans, John Wiley & Sons Inc., 2011. Selected chapters. See lesson sections for specific pages to read (See E-Reserves in Canvas).
• Web article: "The Future of Green Buildings May Be Closer than You Think", Press release, Wharton University of Pennsylvania, May 06, 2013.
• Journal paper: Hakkinen, T., Helin, T., Antuna, C., Supper, S., Schiopu, N., and Nibel., S., Land Use as an Aspect of Sustainable Building, International Journal of Sustainable Land Use and Urban Planning, 1, 21-41 (2013). Selected pages.
• EPRI Report: Sustainable Water Resource Management: Vol. 2 Green Building Case Studies, Electric Power Research Institute, January 2010. Section 2.2.5 (pp. 2-21 to 2-27).

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

The Horniman Museum (London, UK) - CUE building's "green features include grass roof, passive ventilation, and sustainable construction materials."

Credit: Tatinauk via Flickr

High-performance building – (also termed “green building” or “sustainable building”) – is called that because of:

• the higher efficiency of using energy, water, and other resources;
• reducing waste, pollution, and environmental degradation;
• protecting occupant health and improving human productivity.

High-performance buildings are designed, built, renovated, operated in a resource-efficient manner. The main objective of the "green building" strategy is to reduce the overall impact on human health and the environment.

Why did this idea of “building green” come up?

According to US EPA statistics, buildings in the U.S. account for 39% of total energy use, 12% of the total water consumption, 68% of total electricity consumption, and 38% of the carbon dioxide emissions. Furthermore, on the average, Americans spend up to 90% of their time indoors; hence, the built environment has a significant impact on human health, productivity, and emotional state.

Based on US EPA Green Building website, green buildings have environmental, social, and economic benefits:

Environmental benefits:

• enhance and protect biodiversity and ecosystems
• improve air and water quality
• reduce waste streams
• conserve and restore natural resources

Economic benefits:

• reduce operating costs
• create, expand, and shape markets for green product and services
• improve occupant productivity
• optimize life-cycle economic performance

Social benefits:

• enhance occupant comfort and health
• heighten aesthetic qualities
• minimize strain on local infrastructure
• improve the overall quality of life"

What exactly makes a "green building" sustainable?

This is the list of questions to explore when assessing the building design and operation:

Siting

Use of land

Energy Efficiency

Materials

Water Management

Indoor Air Quality

Occupant Health and Comfort

LEED rating system was developed by the U.S. Green Building Council (USGBC) in order to promote a holistic approach to construction and to encourage green certification of buildings. Rating systems developed under LEED allow projects to earn points in a number of categories that comprise the sustainability profile of the building project. LEED certification is flexible enough to apply to various facilities: homes, schools, healthcare facilities, large public sites, and even entire neighborhoods. Currently, it is a nationally recognized certification program.

The main categories of assessment in which buildings can obtain credits are:

• Sustainable sites
• Water efficiency
• Energy and atmosphere
• Materials and resources
• Indoor environmental quality

Go to the LEED website to review the LEED rating systems. Here is the link to LEED Credit Library, which you may want to browse to see how points are scored by various building design features. Certification through LEED is quite a sophisticated process, which requires disclosure of a large amount of data, so it would be best for us to turn to specific examples of LEED-certified projects to understand how this assessment works.

The comprehensive approach and broad scope of the LEED certification has an advantage of wide applicability. So the whole buildings of various size, location, and function can be evaluated within the same system. At the same time, sometimes you can see buildings that are very energy efficient, zero-carbon, water-conserving, and still are not LEED-certified, just because they do not cover all the multiple attributes necessary for that certification. Because of that, it is sometimes useful to apply a single metric to evaluate one specific feature or function of a building.

For example, ENERGY STAR is a single-attribute rating system that only evaluates energy performance. WaterSense is a single-attribute rating system for water conservation. There are a number of other systems and metrics. Some of those will be considered in the following sections under the specific attributes they relate to.

There are four principles that a good assessment system should follow - it should be:

• science-based – results and decisions must be reproducible by others using the same approach;
• transparent – the standards and scoring procedure should be open for examination;
• objective – there should be no conflict of interest in the certification body;
• progressive –the system should advance industry practices.

Here are some examples of sustainable buildings in the U.S.:

The Philip Merrill Environmental Center is recognized as one of the "greenest" buildings ever constructed in the United States. When it was constructed, special consideration was given to material selection and energy use. This facility was the first building to receive a Platinum rating through the U.S. Green Building Council's LEED Rating System.

Pittsburgh's 1,500,000-square-foot David L. Lawrence Convention Center was the largest "green" building in the world, when it opened in 2003. It received Platinum LEED certification in 2012.

Sota Construction Services office building (Pittsburgh, PA) features a super-efficient thermal envelope using cob walls. It also has other energy-saving features: a geothermal well, radiant heat flooring, roof-mounted solar panel array, and day-lighting features. It earned a LEED Platinum rating in 2012 and received one of the highest scores by percentage of total points earned in any LEED category, making it the "greenest" building in Pennsylvania and in the top ten greenest in the world.

Sota Construction Corporate Headquarters, Pittsburgh, PA, is one of the "greenest" buildings in Pennsylvania.

Credit: Dutchrub via Wikimedia Commons

The Energy Use Intensity (EUI) metric is easy to calculate if you know your building’s annual energy use. The most accurate way is to look at your energy bills. Take the total annual amount of energy used and divide it by the total floor area of the house or building:

Before using this metric in analysis, we need to understand the difference between the gross EUI and net EUI metrics and what they indicate.

The gross EUI reflects the total building’s energy demand and includes all available sources: electricity, natural gas, renewables, and delivered fuels. No matter from what sources your energy comes, the building will require a certain amount of energy for annual operation, and this is what is accounted. Thus, the gross EUI will depend on the efficiency of the building envelope, design, and purpose. At the same time gross EUI will not be dependent on the type of energy you choose, it will only depend on the characteristics of the building itself.

The Net EUI reflects the difference between the gross energy demand and on-site generation. This is the metric that can characterize a building on the net zero scale. In this case we need to define the Renewable Production Intensity (RPI), which is essentially all energy supplied by on-site renewable sources, primarily solar, in kbtu/year divided by the total floor area of the building.

In case of a grid-bound solar system, the electricity bill will reflect the net kilowatt-hours taking into account consumption and on-site generation. So the easy way to calculate the Net EUI would be just using your utility bills for purchased energy:

Net EUI = E(elec) + E(gas) / Area

To calculate EUI in kbtu/sf/year (this is how it is presented in the LEED studies), you need to convert your energy units from all sources to kbtu and present the area in square feet.

The following conversion factors can be used:

• Electricity (both grid and onsite solar): 1 kWh = 3.412 kbtu
• Natural gas: 1 therm = 100 kbtu
• Fire wood for space heating: 20,000 kbtu/cord*

*Note: energy content of fire wood would depend on the type of wood and vary. The given value is an average that can be used as first approximation.

It should be noted, though, that within a certain month during the year, the net-zero condition may or may not be achieved. For example, in winter higher energy demand for heating may not be matched by seasonally decreased solar generation. At the same time, extra energy generated over the summer months would be fed to the grid and can be used to offset the winter deficit.

Weather-normalized EUI

What if we have two buildings of similar size located in different climate zones? One – in Minnesota and the other – in California. The first building has EUI of 28 and the second has EUI of 20. Would it be fair to say that the second building is more energy efficient?

As the matter of fact the first building may require more energy through the year not because of its inefficiency, but due to much higher heating load. After all it is placed in much more severe environment and has to withstand much more drastic temperature gradients, especially in the winter time.

To provide a fair comparison of the buildings in this case, we can use weather-normalized EUI. This is the metric that takes into account the weather, specifically heating and cooling needs, which can be expressed as heating degree days (HDD) and cooling degree days (CDD).

If you never heard of heating and cooling degree days, please check out this link. Those are common measures used to estimate the heating and cooling capacities needed for a building. Degree days indicate for how many days the outside temperature stays below or above the reference point of 65 F (this is the standard temperature by convention!). Degree days can be counted for any time period – a day, a month, or a year. Let me give you a short example.

Let us come back to the case of two houses placed in different climate zones. We are going to compare data for those two locations in the table:

From this calculation, we see that the house in California in fact spends more energy per degree day than one in Minnesota to keep the temperature at the comfort level. So the ultimate conclusion is that the building envelope of the first house is more energy efficient.

The above-discussed metrics for house energy efficiency will be included in your lesson activity, so you will have a chance to apply those to your own residence and compare it to others.

Refer to the following reading source to learn about the sustainable choices in building materials and some criteria of their selection.

As you can perceive from this reading, one of the overarching objectives here is to select materials that have high degrees of renewability, reusability, and durability and at the same time have low environmental impact and low embodied energy.

How would you guide your selection? The principles of selection of alternatives discussed in Lesson 4 of this course apply here as well. The process may involve lifecycle analysis for some of the materials and also multi-criteria analysis to ensure the highest feasibility and lowest impact.

Adobe bricks are a good example of low-impact construction materials in the areas where resources are limited. They also enable recycling of other process by-products. For example, the left image demonstrates production of bricks that utilize sugar-case by-products and rubble in a disaster relief zone.

Credit: IDVMedia / Raul Hernandez Gonzalez (via Flickr)

Sometimes, it is not easy to make a definite conclusion about the sustainability of particular materials. The question of sustainability requires wider thinking, which not only describes the material nature, environmental properties, and possible impacts. Sustainability also assumes identifying the specific fate of that material in a particular locale.

For example, if we consider refractory (fired) bricks as a common construction material, would those be a sustainable choice for construction? It really depends on a wider view on material lifecycle. Bricks are produced from extracted earth materials (such as clay) by firing in a furnace. Energy is needed to heat that furnace. In one case, if we burn coal to fire furnace to make bricks, it does not look like a sustainable production. Coal is a fossil fuel (non-renewable), and burning creates significant carbon emission, so this makes brick production apparently not a sustainable choice. But can that furnace be heated using a renewable energy source? For instance, can we use an electric furnace with electricity produced via solar power generation? Without going deeper into the feasibility of that choice, we can immediately see an opportunity to make this process sustainable. On the other end of the story, if the building gets demolished, where do the bricks go? If they contribute to deconstruction waste and are hauled to the dump, non-sustainable practice results. But if there is a plan of responsible demolishing, and if we know that those bricks will be separated from other waste, shipped to the processing facility around the corner, crushed, and re-used as new bricks or as coverage for the jogging trail in the town park, we have a much better feeling about it.

The routes defining the material fate should be outlined at the planning stage, and appropriate system analysis should help with that; and further, the material lifecycle should be regulated according to that plan. That said, sustainability is not so much about materials, but more about design and managing strategy. Also, the sustainability system usually has wider boundaries than the building itself, so sustainable buildings cannot be assessed apart from their infrastructure.

Lifecycle Building

Lifecycle building is known as design for disassembly and design for deconstruction. This innovative approach encourages creating buildings that provide resources for future buildings.

The lifecycle building initiative was catalyzed by a number of problems. According to U.S. EPA:

• more of the 100 million tons of building-related construction and demolition debris are sent to landfills in the United States each year;
• construction and demolition debris comprises about 40 percent of the solid waste stream;
• reusing building components reduces the energy and greenhouse gases emissions associated with producing and transporting building materials;
• between the years 2000 and 2030, an estimated 27 percent of existing buildings will be replaced, and 50 percent of the total building stock will be constructed.

Lifecycle building approach implies easier building material recovery and reuse, thus reducing energy and resource consumption.

Efficient use of energy is one of the key targets of high performance buildings. There are two main strategies pursued: (i) conservation of energy through more efficient building design and (ii) on-site power generation through energy-conversion technologies. The options for the power generation include renewable and no-emission resources, such as solar, wind, and geothermal energy, depending on the building setting preferences. A sustainable building can be still connected to the grid, but should be much less reliant on it and, in some cases, can even feed some of the extra energy produced on site back to the grid (net-zero energy building concept).

Let us start with the following chapter reading. This reading will introduce you to the main systems and energy interactions inside a building. It also contains useful terminology.

One of the ideas we can get from this reading is the importance of flexibility and tunability of design. Designing and building for variable conditions allows for significant energy savings and more efficient use of resources when it is needed. For example, one of the cornerstones of green building designs is proper ventilation. Sensitive ventilation, such as adjusting ventilation requirements based on human occupancy, is one of the sources of energy saving.

Such tunable designs require special technologies for monitoring and control. For example, Air monitoring technologies, such as sensors, "smart controls" can be of great benefit in the regulation of high occupancy spaces (conference rooms, auditoriums) in terms of total required energy. Technology is currently available that monitors the CO2 levels in the space. Occupancy sensors can be used to turn off light in occupied spaces.

Net Zero Energy Building

One of the very attractive concepts in building design is net zero energy building (NZEB). In brief, it means that energy generated by the building offsets the consumed energy by the building operation. In that case, ideally, the building does not require grid and can sustain itself. This concept is currently under development, but some successful examples of its implementation already exist. Read the following web article to get a deeper insight into this topic.

Optimizing use of the sun

Many existing homes and buildings heavily rely on oil, coal, and natural gas as fuels to heat and cool our homes. If not burning those fuels directly, we consume electricity from the grid, anyway, much of that electricity coming from the fossil fuel power plants. Those fuel resources are expensive, create pollution, and they are also being depleted rapidly. This makes attractive the strategy to adapt buildings for using the solar energy, which is an unlimited resource.

There are active and passive strategies for sun use:

Active strategies

Active strategies use solar photovoltaic (PV) panels or solar collectors to turn the solar radiation into electric energy or thermal energy. The technical principles of operation of PV and solar thermal technologies will be considered in more detail in another lesson, specially devoted to energy. Currently, many residential and commercial buildings are being evaluated for installation of active solar systems. While some are very well positioned to accommodate such on-site energy converters, others may be less suitable. Decision may be driven by such factors as: building design, shading structures, solar resource at the location of interest, building energy need compared to the system capacity, available roof or ground area for installation, and building aesthetics.

Passive strategies

Passive strategies include features and adaptations in the building envelope and smart use of the natural solar activity. The passive approach does not imply installation of a separate solar energy conversion system, but rather utilizes features of building design. For example, a house can be oriented to minimize summer afternoon solar heat gain and to maximize winter solar heat gain. If the building is located in the Northern Hemisphere, the long sides of the house are made facing south and north while roof overhangs and landscaping are built to shade the east, south, and west sides. Alternatively, house design can take advantage of prevailing breezes during the spring, summer, and fall. Natural air movement is valuable for cross-ventilation of the house. In addition, foliage of trees and shrubs that create shade around your house helps keep the house cool, while bare branches in winter let the sunlight through to warm the house.

In passive system design, many physical parameters are manipulated to achieve the balance of heat distribution. There is a lot to learn in terms of how the light transmitting and absorbing surfaces are geometrically positioned, and what materials are used. You would have to turn to an architectural design course to become better educated on this topic, should you have interest. A couple of links below would give you some examples of passive solar strategies, if you are interested to learn more.

Land use by buildings is a significant aspect in sustainable development. We can recognize direct use (because buildings and their related infrastructure occupy a certain land area for their entire lifetime) and indirect use due to impact on land via extraction of raw materials for construction, waste disposal, etc. Both types of land use impact should be considered in environmental assessment.

Here are some key land use impacts [Hakkinen et al., 2013]:

• Soil sealing
• Soil compaction
• Change of land use
• Fragmentation
• Extraction of raw materials
• Reduction of biodiversity

Read the explanations to these impacts on pages 24-26 of the following article:

To propose strategies to improve the building design with respect to land use, those impacts need to be assessed and possibly quantified. Introduction of metrics helps compare buildings and refer them to certain standards of advanced or poor practice. Land use indicators can be either included in the LCA for buildings or be used independently.

Examine the land use metrics proposed in some European countries in Tables 2 and 3 of the above reading [Hakkinen et al., 2013].

What are strategies to create avenues for more sustainable land use by buildings? Some of those strategies are:

• urban densification;
• complexity and mixed use;
• green zoning;
• accessibility to public services and transport.

Read about them on pages 34-35 of the Hakkinen’s paper.

Indoor pollution consistently ranks among the top five environmental risks to public health. Because, by statistics, Americans spend up to 90% of their time indoors, the impact of building environment is increased compared to outdoor environment. Many air quality technologies need to be planned at the design stage of the building, since accumulation and removal of contaminants is largely dependent on air flow, moisture condensation patterns, and other physical properties. Physics and flow dynamics of the building need to be understood thoroughly in order to be used to the occupant benefit.

What are the main factors that can potentially make the indoor air a health problem?

Refer to the following reading source to study this question.

All buildings must use water for daily operation, but statistics indicate that currently employed buildings (residential or business) use too much of it. Centralized water supply and treatment creates an impression of abundance of water resource, but is virtually inefficient in showing how much water is actually used rather than wasted. Sustainable building designs target to improve that efficiency, implementing reuse systems within them and promoting water conservation through a number of technologies and strategies.

Here are some of the features of resource-efficient building hydrology systems:

In resource-efficient buildings, plumbing fixtures that use minimum amounts or zero water represent important water conservation technologies. These technologies include:

• composting toilets, low-flow toilet (0.8 gal/flush), waterless urinals;
• low-flow shower heads (less than 2.5 gal/min);
• low-flow faucets (less than 2.5 gal/min), metered faucets.

Gray water systems allow reuse of the water coming from sinks and washing machines for toilet flushing and irrigation. Gray water can be reused directly or after cleaning with on-site sand filters.

Waste heat recovery systems can capture heat from the used gray water going down the drain and use it for heating the clean water. Heat recovery can be especially efficient in facilities with extensive hot water use (e.g., laundries, locker rooms).

Instead of trying to list all possible technologies and tactics related to sustainable water management in buildings and characterize them generally, it would be more useful to study a good example of practical implementation. Here is a report that describes a few case studies of sustainable buildings, which includes quite detailed characterization of their water management features.

This lesson overviews the key aspects of high performance buildings. The bottom line here is that different systems inside the building require specific technical knowledge, so creating a sustainable building is a collaborative, multi-expert task. All of the design and technology efforts typically target two main directions: resource use efficiency and human health. Because of the complexity of building design, assessment of buildings requires a comprehensive framework, such as LEED, which was adopted as a universal metric set in the U.S. It is not the only certification system for buildings, but is probably the most well known and widely used in assessment of public facilities and large common use buildings. While we do not go through every step of the LEED system here, we explore a few common metrics and study several examples. The design + technology collaborative thinking made a Net Zero Energy Building a reality, so this lesson also took a brief tour of that concept.

In Lesson 8, we will overview several renewable energy technologies that are currently considered the main players of the future sustainable energy economy. It would not be realistic to cover all technical details of these technologies within one lesson, and this is not our goal here. Your main focus in this lesson should be to grasp the basic idea of how these technologies operate, how their performance is compared to conventional energy options and to each other, and what is the promise. In the end of this lesson, you will be asked to perform an activity on the comparison of some energy technologies by several metrics that are relevant in sustainability analysis. Some examples of metric calculations and some technology applications are also included in this lesson.

Learning Objectives

By the end of this lesson, you should be able to:

• articulate the fundamentals of the key alternative energy technologies;
• understand standard metrics for analyzing and comparing alternative energy technologies.

Readings

You will be asked to read the following sources throughout the lesson. Please excuse the large number of readings – renewable energy is an extremely versatile area to cover. Some of these sources are concise and contain introductory information that will not require too much time to work through.

Website: Christiana Honsberg and Stuart Bowden, PV-Education.org

Web article: "Solar Thermal Power Plants. Technology Fundamentals," Renewable Energy World, 06/2003, pp. 109-113.

Web article: How Geothermal Energy Works”, UCS, 4/1/2014

Book chapter: F.M. Vanek and L.D. Albright, Energy Systems Engineering. Evaluation and Implementation, McGraw Hill, 2008 – Chapter 12 Wind Energy Systems, pp. 331-366. 

NREL Report: R. Thresher, M. Robinson, P. Veers, Wind Energy Technology: Current Status and R&D Future, NREL, 2008.

EPA Report: Biomass Combined Heat and Power Catalog of Technologies, U. S. Environmental Protection Agency, Combined Heat and Power Partnership, September 2007. Chapter 5: Biomass Conversion Technologies, pp. 30-61.

Web article: "Environmental Impacts of Renewable Energy Technologies," Union of Concerned Scientists, 4/26/2014

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

Renewable energy has been a catchphrase of recent decades. It has been both the subject of government policies and extensive research. We are searching for efficient ways to move from the easily accessible but finite fossil fuel energy to other types of energy available on earth that are either unlimited or can be replenished within a much shorter timescale.

We have one lesson to review this topic. This does not allow us to go anywhere in depth while discussing specific technologies, but we will take some time to consider a few examples of how the renewable energy technologies are chosen, implemented, and assessed from the sustainability standpoint.

The term renewable essentially means that the energy source is not exhaustible on a human timescale. This, however, does not always mean that it has infinite capacity or constancy. We will see that different sources of renewable energy have different limitations, which must be taken into account when tuning the technologies to a particular application and locale.

The main types of renewable energy resources are schematically summarized below:

Figure 8.1. The main kinds of renewable energy sources.

Credit: Microsoft Clip Art

The technologies that are designed to convert the above kinds of available natural energy to usable power or heat are expected to play significant roles in future energy economy. However, markets involving those technologies are still developing, and at the moment it is not so easy to predict which of them will become most prominent.

I am sure you are somewhat familiar with the operating principles of these technological systems. You may be still curious to look through the Renewable Energy Wikipedia article to refresh your basic knowledge on those types of energy conversion. Consider this as an optional resource unless you feel you have serious background gaps to fill.

Because we will be going through some numerical examples involving energy, it would be also useful to have a refresher on terms and units.

Quick refresher on energy terms and units

Energy is the capacity of a system to perform work. Energy is also an extensive quantity, measured by amount. Thus, you need a certain amount of energy to perform a certain work. Energy can be added, subtracted, converted from one form to another, but it cannot be created or destroyed according to energy conservation law.

Units to measure energy:

• Joule (J) - International SI system. Convention: 1 J is the amount of energy necessary to move an object over 1 meter against the force of 1 newton.
  Joule = Newton x meter = Pascal x meter³ = Watt x second
• British Thermal Units (btu) - used in fuel and thermal applications. Convention: 1 btu is the amount of energy necessary to heat 1 pound of water by 1 degree Fahrenheit. 1 btu = 1055 J
• Kilowatt-hours (kWh) - used in electricity. Convention: 1 kWh is the amount of energy being transmitted with the power of 1 kW over 1 hour
  1 kWh = 3600 kJ

Power is the amount of work performed per unit of time. Power can be understood as the rate of energy conversion.

Units to measure power:

Watt (W) = Joule / second

Often, the energy converting systems are rated by power.

Role of energy technologies in sustainability

Since energy is the main commodity ensuring well-being and sustainability of human society, the role of energy technologies is critical. The efficiency with which we can convert and distribute energy essentially determines our standard of living. Speaking the systems language, sustainability would require maintaining the stock of usable energy at the demand level. Consider the system diagram in Figure 8.2.

Figure 8.2. System diagram for renewable energy conversion. The system's main goal is to maintain the constant availability of services and products for society, production of which requires constancy of usable energy flow. Development and optimization of the efficient energy conversion systems is a necessary condition for making this system resilient and capable of eventually meeting energy demands. Please see further explanation in the text.

Credit: Mark Fedkin

The main goal of the sustainability system shown above is to keep up the usable energy stock, as it is closely connected to the amount of demanded services and products for society. These two stocks are related through the energy utilization rate.

To make sure the society demand is met, the energy supply rate (left-hand valve) should match the energy utilization rate (right-hand valve). It is this supply valve where energy conversion technologies play the major role. The energy is supplied from a source (which we can assume to be unlimited, e.g., sun energy); however, the conversion rate of the available energy from the source to the usable energy will be the main limiting factor. Conversion rate will depend on technology efficiency, system size, and will be affected by environmental conditions at a particular locale.

So, what can be done to maximize the energy conversion rate at the supply valve?

1. Maximize efficiency. This depends on the stage of the technology development, physics of the process, materials, design, and other things that may be improved through research and development efforts.
2. Scale-up the conversion system. Feasibility of this measure may be limited by technology cost and available space or land area (to accommodate the equipment, etc.)
3. Tune technology to local source and conditions. Local conditions will dictate the adequate choice of technology to employ (obviously, solar energy is great where there is a lot of sun, and wind energy option would be suitable to the places that are windy). Also, system design should be adapted to the geometry and timing of the natural resource – such supplemental technologies as tracking and energy storage help increase the overall conversion.

All the above factors shown on the diagram will affect the energy conversion rate.

While we can identify the factors that maximize the conversion and enhance the system’s function, the system may be not resilient until there is a return balancing loop. One of such loops (shown by dashed line on the system diagram in Figure 8.2) shows the investment of the energy generation revenue into creation of new energy conversion systems. This feedback has been more strongly established over the past decade, but it can be also driven to one side or the other by government incentives and social factors. Furthermore, wider implementation of the renewable energy conversion systems will result in an increase of renewable energy supply and higher energy stock for consumers.

Establishment of this system will eventually ensure renewable energy economy; however, this process is still hampered by strong economic competition from the non-renewable energy worldwide, which is currently in a dominating position by scale, profit, and infrastructure development in a number of major players - e.g. China, United States, Russia.

This is only one slice of the quite complex “tug-of-war” issue of commercialization of the renewable energy. It is anticipated that recent advances in research and development will be able to increase the energy conversion efficiency and thereby further upgrade its market value. The technical status of several prospective energy technologies is reviewed in the following sections.

Solar energy conversion is a large topic. The key technologies to mention here include:

• Photovoltaics (PV, optoelectronic systems) - convert solar visible radiation into electricity;
• Concentrating Solar Power (CSP, solar thermal, or optocaloric systems) - convert solar thermal radiation into electricity;
• Solar heating systems - utilize solar heat (concentrated or not) without conversion.

You can learn these technologies in depth, taking some of the courses in the Solar Energy Option of RESS. Here in this lesson, we will turn to one of the application examples of PV technology to study the factors that affect the practical implementation of solar panels in buildings. But before doing that, let us review the basic principles by which photovoltaic systems operate.

PV Basics

Photovoltaic (PV) technology is one of the ways to convert solar resource into usable energy - specifically sunlight to electricity. Photovoltaic conversion is enabled by certain semiconductor materials, which have a property to generate electric current when they absorb incident photons. The physics of the photovoltaic effect can be schematically envisioned as three step process [Brownson, 2014]:

1. absorption of light;
2. generation of charge carriers (electrons and holes);
3. separation of charge carriers (so that they can perform work).

This effect is physically realized in certain semiconductor materials  - for example, monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide and some others, all of which can be potentially used for making the PV cells. 

Watch This Video as an introduction to PV cell technology and the photovoltaic effect.

This first short video (2 min) provides an animated illustration of the photovoltaic effect:

Video: Energy 101: Solar PV (2:00)

Next, let us gather some more details on the structure, functions, parameters of the photovoltaic materials.

PV Application in Buildings

Current applications of solar photovoltaics are adapted to the following scales:

• portable (small electronics - e.g., calculators, computers, etc.);
• distributed power generation (homes, isolated equipment);
• utility scale power (solar farms).

In the scale-up process, the single PV cells are combined to modules, and modules can be arranged into arrays:

Figure 8.3. Different scales of PV technology.

Credit: OregonDOT / Jon Callas / USFWS Mountain-Prairie via Flickr

In this lesson, we choose one of the applications – the building integrated photovoltaics (BIPV) – for more detailed consideration as an interesting example of sustainable technology implementation.

The building-integrated photovoltaics (BIPV) are multifunctional materials that are both structure-supporting and power-generating at the same time. There are some advantages and challenges associated with this technology, which are summarized in table below:

Building façade with integrated photovoltaic panels.

Credit: Payton Chung via Flickr

While the main function of a conventional PV system is efficient power generation, the building integrated PV systems, which become the components of the building envelope must satisfy a number of additional requirements, such as:

• appearance: color, image, size;
• weather-tightness;
• wind loading;
• durability and maintenance;
• safety during construction and in use (fire, electrical, structure stability);
• cost.

In order to address all the necessary factors, the PV integration should be discussed early in the beginning of the design process. There are following PV integration options [Robert and Guariento, 2009]:

(a) Shading systems

These include louvers, either horizontal or vertical, which may be mounted outside the building over windows or balconies. Their function is to shade the windows from excessive light. The main issue with these structures is to make them resistant to wind load and easily accessible for maintenance. These subscreens can be made adjustable to maximize the sunlight gain.

(b) Rainscreen systems

Cladding panels can be used to protect the load-bearing external walls from rain water (especially masonry and concrete). PV panels can perform the function of such cladding and tiles. These structures are usually vertical. The ventilated cavity between the exterior cladding and the main wall help keep down the operating temperature of PV cells, enhancing their performance and provide space for cables. PV rain screens have moderate power output due to vertical orientation.

(c) Stick-system curtain walls

Curtain walls are used in those buildings that have internal columns or structural steel to support the main loads. Curtain walls are not weight-bearing and their main function is to resist air and moisture infiltration; also, building insulation is often attached to them (warm facade). A popular solution is to build the curtain walls from aluminum and steel framing filled with glass panels. PV panels can be sealed into curtain wall structures in both vision area or opaque area of the facade instead of regular glass.

(d) Unitized curtain walls

The unitized wall segments are pre-assembled at a factory and then are delivered to the building site. The controlled industrial environment provides more precision and quality for sealing the PV panels into the wall framework and making cable connections.

(e) Double-skin facades

Glass facades are often designed as "double-skin", i.e., when there is significant air space between the internal and external glass walls. This helps to reduce heat transfer losses through the walls. PV modules can be readily integrated into the external facade. Ventilation through the double-skin structure provides valuable cooling on the back of the panels.

(f) Atria and canopies

For the highest performance, PV are best integrated into horizontal or tilted elements, such as atria and canopies. These structures are usually free from overshadowing and are easy to ventilate. However, these structures may be more prone to heat transfer losses compared to plain opaque or insulated.

Lifecycle Considerations

One of the main reasons why solar PV systems are being developed is their potential to replace fossil fuel combustion in power generation. While economically, fossil fuels are proved to be profitable, there is a sustainability concern (coal, oil, and gas will run out eventually) and there is an environmental concern (combustion pollutes and contributes to the greenhouse effect on earth). The solar PV can potentially address both of these concerns.

Because, unlike fossil fuels, solar energy is virtually unlimited, PV seems to be a perfect solution from the standpoint of energy sustainability. (Sunlight will not run out any time soon).

From the standpoint of environmental protection, the main question is whether or not the environmental benefit of reducing CO₂ emissions achieved through the use of the solar systems will offset the impact of possible toxic emissions from the manufacturing of the solar modules and potential land pollution from the disposal of those systems at the end of their lifetime.

Let us make some rough estimations of the environmental benefit of PV technology. Consider the following example.

The above example demonstrates the scale of the benefit. Now, let us look at the other side of the medal. The accelerated growth of PV system manufacturing and use will have to become a major market and also should have infrastructure for maintenance and disposal of vast amount of PV-related components. While PV panels are considered are relatively durable with a long projected service life, high volume annual turnover of such systems can be expected. Here, we can do another estimation exercise.

The above-illustrated issue of waste disposal associated with the proliferation of the current PV technology calls for further development of solar cell design. The following improvements will be needed:

• development of thin, low volume solar elements;
• increasing efficiency of energy conversion to minimize the size of systems;
• designing cells for recyclable turn-over and conservation of valuable materials;
• using low-toxicity chemicals and materials in manufacturing;
• creating infrastructure for lifecycle management.

Solar tower farm for harnessing the natural thermal energy

Credit: Afloresm via Flickr

Solar thermal technologies are designed to convert the incident solar radiation into usable heat. The process of solar heat conversion implies using energy collectors - the specially designed mirrors, lenses, heat exchangers, which would concentrate the radiant energy from the sun and transfer it to a carrier fluid. The fluid passes through the sunlight collector and becomes very hot. Typical heat carrier fluids are water/steam, oil, or molten salt. Then the fluid is transferred to the heat engine, which converts the heat to electricity.

Please watch the following video, which provides an illustration of this technology.

Video: Energy 101: Concentrating Solar Power (2:16)

There are several different kinds of solar collectors, which are described below. These collectors are only functional with the direct beam of sunlight and would also benefit from sun tracking - the technology that keeps the reflectors at an optimal angle to the sun.

Flat plate collectors

Flat plate collector is the simplest technology of this kind, which is typically used for reaching temperatures usually no more than 100 degrees above ambient.

Figure 8.4. Schematic of a flat plate solar collector. The solar radiation is absorbed by the black plate and transfers heat to the fluid in the tubes. The thermal insulation prevents heat loss during fluid transfer; the screens reduce the heat loss due to convection and radiation to the atmosphere.

Credit: Mark Fedkin, modified after Duffie and Beckman, 2013

Concentrating collectors

Figure 8.5. Types of concentrating sunlight collectors: (a) tubular absorbers with diffuse back reflector, (b) tubular absorbers with specular cusp reflectors, (c) plane receiver with plain reflectors, (d) parabolic concentrator, (e) array reflectors (heliostats) with central receiver. Concentration of light on the receiver is achieved by shaping the reflectors (mirrors) around the receiver.

Credit: Mark Fedkin - modified after Duffie and Beckman, 2013

The above collectors are combined to a bigger energy conversion system. The larger scale solar thermal systems have higher efficiency than small systems.

The utility scale solar thermal systems include the following designs:

• linear reflectors (heating temperatures ~280 ^oC);
• parabolic trough (heating temperatures ~400 ^oC);
• dish / engine systems (heating temperatures ~650 ^oC);
• solar tower (heating temperatures ~>1000 ^oC).

Please refer to the following reading to learn more details about the solar thermal technologies.

Blue Lagoon, Iceland: geothermal resource is the major part of the energy economy and tourism in Iceland.

Credit: Laurent Gauthier via Flickr

There is a vast amount of heat contained by the earth interior. This internal heat is mainly comprised of the residual heat of planetary accretion and radioactive heat (from radioactive element decay). The hottest part of the earth is the core, a big part of which is in molten state. Heat radiates and gets transferred from the core to the outer layers of the planet by interior fluids and melts. The general geothermal profile of the earth (Figure 8.6) provides an idea of the scale of the thermal resource and the gradual change of the earth temperature at different depths. Because the earth structure is not uniform, heat is more readily transferred in some zones than in others. High heat transfer is usually associated with fracture zones and major faults, which are often located at the boundaries of tectonic plates.

Figure 8.6. Geothermal gradient. Temperature inside the earth gradually increases with depth due to the interior heat flux. The average gradient in the earth crust (reachable by drilling) is approximately 25^oC per km.

Credit: Mark Fedkin (data from Alfi et al., 2003)

The temperature change rate with depth depends on the density and thermal conductivity of rocks. Subdivision of the earth structure into layers is made according to the rock composition and rheological properties, so we see that the thermal profile within each layer can be quite different. The drastic change in temperature pattern around the boundary between the lower mantle and outer core is apparently related to the transition of the molten state.

The heat flux within the crust (the thin top layer) is highly variable due to the existence of large unified fragments of the crust (plates) divided by plate boundaries, the more mobile zones, where plates collide, spread out, or move relative to one another. Increased mobility of the plate boundary zones may cause creation of faults of various depth, which favor heat transfer to the surface. If you want more background about plate tectonic theory, you will be able to find a lot of resource on the web. For example, An Introduction to Plate Tectonics provides a nice and concise illustrated introduction to this whole idea.

There are a number of technologies that help convert the thermal flux and hydrothermal waters to usable energy. Next, we will refer to the following reading to learn how these technologies work.

The following short video (5 min) provides an additional illustration of a utility scale geothermal plant.

Video: How a Geothermal Plant Works (4:45)

While geothermal energy seems to be another unlimited and “free” energy resource, effective conversion of that energy and power distribution incur substantial costs. From economic evaluations, utility scale geothermal and natural gas power plants are comparable in overall cost, but only in the long term. Significant up-front expenditures for construction of the energy facility are much higher for the geothermal plant.

Wind energy is primarily used for power generation. Wind power conversion systems have been increasingly employed in the U.S., Europe, India, and more sparingly in some other locations over the last decade, due to the development of technology that allows relatively high efficiency of the wind resource conversion. The key process is the conversion of the kinetic energy of moving air into the mechanical kinetic energy of the rotating shaft of the turbine. Similar to solar energy resource, one of the main challenges with wind power is its intermittence and high variability, which requires systematic adjustments in operation as well as strategies to integrate the wind power into the grid.

Video: Energy 101: Wind Turbines (2:16)

Please refer to the following reading source for learning about wind energy systems below.

Energy return on investment (EROI)

EROI is a common metric applied to the energy conversion systems. It is defined as the ratio of the lifetime usable energy generated by the system to the energy spent for the system manufacturing, operation, maintenance, and disposal. Obviously, EROI = 1 would mean that over its lifetime a system produces as much energy as has been consumed for its creation and operation. Such a situation would indicate very low feasibility.

For wind turbines, the typical estimate of the EROI is in the range from 5 to 35, depending on the type of system. This indicator significantly increases with the size of the turbine rotor. The latest generation large-scale turbines yield EROI values about 35 and higher (Kubiszewski et al., 2010).

Status of technology

The wind power generation systems have been commercialized for several decades now. The efficiency and durability of the systems was improved over time. So, recent developments explain the growing interest in wind energy and observed growth of wind energy market. Read more on the status of this technology in the NREL report:

Economic aspects

Economic analysis of renewable energy systems mainly focuses on the ability of the system to pay back the initial investment and operation costs within a reasonable period of time.

The lifetime cost of the wind energy system can be split into the (i) initial cost for system manufacturing and installation, (ii) operating and maintenance cost, and (iii) decommission cost.

The initial upfront cost of wind energy system is usually the highest (~75%) and typically includes turbine (including rotor, tower, drivetrain), foundation, land rent, electrical equipment, connection to the grid, road construction and other infrastructure, transportation, installation labor and expertise, and associated soft costs (Figure 8.5).

Operating and maintenance costs are relatively low, especially that there is no fuel cost involved.

Figure 8.7. Example breakdown of capital costs for an on-shore wind energy system.

Click for a text description

The breakdown of the wind energy system cost: Turbine itself 68%, balance of station 23%, and soft costs 9%. The turbine cost includes 15% for rotor, 37% for drivetrain, and 16% for tower. The balance of station cost includes: foundations 4%, turbine transportation 3%, roads and civil work 3%, assembly and installation 3%, electrical interface 8%, development 2%, and project management 1%. Soft costs include contingency 6% and construction finance 3%.

Source: National Renewable Energy Laboratory

Taking into account the typical costs listed in Table 8.2, one can perform a standard cost analysis to find out how long would it take for the wind system to pay back investments. Feasibility would depend on the lifetime of the system itself and how it compares to the payback period. Please refer to the example below, which tries to examine this question

As a rule, the small-scale residential wind energy system have longer payback period, because they typically operate at less favorable wind conditions; so the capacity factors are usually lower (~10%) than that for the commercial utility scale wind systems (~30%)

More information on wind energy economics and costs can be found in the following reading (which is optional for this lesson):

Examples of biomass alternatives - wood chips and corn.

Credit: firewood and corn field by Liz West via Flickr is licensed under CC BY 2.0

Biomass as a source of fuel has been part of the global energy economy throughout human history. Using biomass as fuel (via combustion) may help solve the fuel supply issue, since biomass is renewable, but does not help solve the global carbon emission and pollution problem: burning biomass produces CO, CO₂, NO_x, and other gases at the levels exceeding those from traditional fossil fuels (e.g., oil, gas).

Indirect utilization of biomass implies the production of various biofuels (for example, ethanol), which can be converted to energy in a cleaner way. Types of biomass currently on market and ways to produce them are well described in the Biomass Wikipedia article

Biomass combined heat and power (CHP)

Biomass-fueled CHP or cogeneration is one of the applied technologies developed as a cost-effective method of energy recovery. Because the by-product heat generated in electricity generation is not wasted, but rather utilized as thermal energy, the total efficiency of such systems reaches 60-80%.

There are three main stages in the biomass-fueled CHP process:

1. biomass collection and preparation
2. biomass conversion: (i) to steam or (ii) to biogas
3. power and heat generation

These three stages are integrated in one installation.

The following bio resources are considered for energy recovery:

• energy crops and crop residues
• forest residues and wood waste
• manure biogas and wastewater treatment biogas
• food processing residue
• municipal solid waste (MSW)
• landfill gas

Wood products currently make up the dominating stock in U.S. (Figure 8.8).

Figure 8.8. National energy recovery from biomass by source.

Credit: US EPA, 2007

These different biomass resources require somewhat different approaches to the collection, storage, and conversion. In brief, there are two main categories of biomass conversion systems, as outlined in the table below:

Chapter 5 of the EPA report on CHP biomass technology provides a good amount of technical details as for how these conversion methods work.

Commercialization status

Biomass is used in the original solid form or can be gasified or converted to liquid fuels. There are a number of commercialized and emerging technologies to foster that conversion (Tables 8.4 and 8.5).

Credit: USA EPA, 2007

Credit: USA EPA, 2007

Social considerations

While the biomass energy offers benefits in terms of sustainable fuel supply, it can potentially aggravate the air pollution problem. Except for a very narrow range of applications of biofuels in no-combustion devices, such as fuel cells (which can generate electricity electrochemically with bio-hydrogen and syngas), most of the biomass energy technologies involve burning the fuel and result in greenhouse gas emissions. This drives public opinion away from biomass options towards such alternatives as solar and wind energy. The second issue debated is the potential competition for land use between the energy and food crops.

Biomass protests documented

Credit: John Quarterman via Flickr s licensed under CC BY 2.0

More information on the environmental issues associated with renewable energy technologies is included in the next page of the lesson.

Sustainability assessment of renewable energy technologies should certainly include analysis of environmental impact. By substituting notoriously harmful fossil fuel combustion, the renewable energy options help to mitigate such problems as air and water pollution, excessive water and land use, wildlife and habitat loss, damage to public health, and global warming.

At the same time, we must understand the non-zero impact of those alternatives when assessing their use at a particular locale. The intensity of environmental impact would vary depending on geographic location, climate, and other factors. For example, biomass energy generation may produce stronger environmental and economic impact in the areas where the land resources are limited, and energy crops would compete with food production. Also, technologies that are associated with significant water withdrawal for cooling and other operational needs can potentially strain the region where water shortages are an issue. So, careful decisions need to be made about deployment of particular technologies so that the most abundant local resources can be used most effectively, and overall impacts are minimized.

Evidently, some of the renewable energy technologies, such as wind or solar, do not emit any greenhouse gases during operation. However, manufacturing, transportation, installation, maintenance, and decommission phases of the system lifecycle would involve some energy use, part of which may come from fossil fuel combustion. A number of lifecycle studies were performed to estimate the overall impact of the renewables.

This lesson browsed through a number of renewable energy technologies and applications and provided you with some reading sources to understand how those technologies work and what is their current status of development. While we touched on the technical specs of different energy systems, mastering all the science that is behind those technologies would probably require you to take a separate course on each of those. Our goal here is to understand the role of these technologies in sustainable energy development and their potential pros and cons as decision-making factors. This lesson also contained some examples of metric calculations in order to illustrate the scale of technology impact.

References for Lesson 8:

Electricity is a heavily relied upon commodity, availability of which is critical in every part of modern world operation. In any sustainability model, power systems and management are of primary importance, and the current trends in energy management are highly technological. Innovations and introduction of smart metering and response demand technologies should make it possible to match the versatility of the energy conversion systems with the growing and "spiky" electricity demand. The evident goals of new technological developments are to survive, avoid crisis, and finally build an energy distribution system that is flexible and highly efficient in all circumstances. This lesson touches upon different sides of this complex task.

Learning Objectives

By the end of this lesson, you should be able to:

• describe how the power grid works and what the current challenges are;
• explain the "Smart Grid" strategy and list the key technologies involved in it;
• discuss the role of distributed power generation systems in energy sustainability;
• articulate the benefits of specific demand-response technologies.

Readings

You will be asked to read the following items throughout your lesson. Look for these readings in the required reading boxes throughout the lesson pages.

1. Web article: Solar Power and Electric Grid /NREL. Energy Analysis
2. Web article: Can Renewables Provide Baseload Power? / Skeptical Science. 2011
3. Web article: Sunday Train: The Myth of Baseload Power / Daily Kos, 2013
4. Journal article: Taqqali, W.M. and Abdulaziz, N., Smart Grid and Demand Response Technology, 2010 IEEE International Energy Conference, p. 710-715.
5. Journal article: Bushby, S.T. and Holmberg, D.G., Advancing Automated Demand Response Technology, ASHRAE Transactions, 2009, Volume 115, Issue 1, pp. 333-337.
6. US DOE Report: The potential benefits of distributed generation and rate-related issues that may impede their expansion, US Department of Energy 2007

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

Base load power sources are the plants that operate continuously to meet the minimum level of power demand 24/7. Base load plants are usually large-scale and are key components of an efficient electric grid. Base load plants produce power at a constant rate and are not designed to respond to peak demands or emergencies. The base load power generation can rely on both renewable or non-renewable resources.

Non-renewable resources (fossil fuels) include: coal, nuclear fuels. Renewable resources include: hydropower, geothermal heat, biomass, biogas, and also a solar thermal resource with associated energy storage.

Typically, the power demand varies cyclically from day to day, reaching maximum during day business hours and dropping to minimum during late night and early morning, but never dropping below a certain base. (Figure 9.1) This base load is typically at 30-40% of the maximum load, so the amount of load assigned to base load plants is tuned to that level. The above-base power demand (above the base) is handled by intermediate and peak power plants, which are also included to the grid. The main advantages of the base load power plants are cost efficiency and reliability at the optimal power levels. The main disadvantages are slow response time, lack of fuel flexibility, and low efficiency when operated below full capacity.

Figure 9.1. Typical daily variation in power demand.

Credit: Mark Fedkin

Base load plants (as well as other energy converting facilities) are characterized by a nominal capacity rating. For example, if a plant rated at 1000 MW, it means it can generate 1000 MWh of electricity per hour when working at full capacity. The actual generation can be less, depending on the demand or operating conditions, and can be characterized by the capacity factor (CF):

CF = [actual generated output] / [maximum possible output]

There are the number of reasons why a plant can have lower than 100% capacity factor. Some of them are:

• lower demand for electricity over certain periods of time;
• under-capacity operation due to maintenance;
• equipment failures / interruptions;
• resource/fuel shortage;
• equipment upgrade (resulting in high nominal capacity).

The base load power plants typically are coal-fueled or nuclear plants due to low-cost fuel and steady state power they can produce. Hydropower and geothermal power can also be used for base load electricity generation if those resources are regionally available.

The renewable energy systems, such as solar and wind, are most suitable for intermediate load plants. These are intermittent energy sources, with their output and capacity factor depending on weather conditions, daily, and seasonal variations. So, unless there is an effective energy storage system in place, they cannot be relied upon to meet constant electricity supply needs, nor can they be immediately employed to respond to peak demands. However, as intermediate sources, solar and wind systems can be efficient and can help reduce dependence on fossil fuels.

The peak power generation is usually attributed to the systems that can be easily stopped and started. Possibilities are natural gas and oil plants, hydro-facilities.

From the situation as it is right now, we can see that the niche of base load power is currently occupied by mainly non-renewable energy systems and therefore non-sustainable. But here is a probing question:

Can the base load power be entirely provided by renewable energy sources? Or we cannot avoid coal altogether?

Apparently, the difficulty with renewables is their intermittence in time and location bias. Comparison of typical capacity factors of various energy systems reflects this difficulty (see Table 9.1 below)

In the table above, the lower the capacity factor, the more susceptible the system to potential interruptions or drops in performance. We can see that solar and wind technologies, which are notoriously weather-dependent have the lowest CF numbers. At the same time, nuclear power and coal systems are most advantageous when operated continuously and at full load.

To explore this question further, refer to the following readings:

At this point, we can see at least two major issues that make contemporary grid management more complicated: first is the efficient management of the baseload-peak variations and second is the incorporation of renewable energy systems. An array of new technologies and strategies that enable an information-based sensitive approach to electricity mass-market is summarized by the term smart grid, which is introduced in more detail in the next section.

National electric power infrastructure, also called “the grid”, has been developing over more than a century and plays an important role in the nation’s energy security (Figure 9.2). Electricity production traditionally relies on a steady fuel supply (primarily fossil fuels), which would keep the power plants operating on the permanent basis. Eventual switching from the traditional fuel-burning plants to cleaner alternatives requires redesigning the grid in such a way that it properly responds to the sharp variations in demand, adequately compensates for the intermittent operation of the renewable energy systems, and can interact with distributed power generation systems.

Figure 9.2. USA transmission grid: colored lines denote different transmission voltage.

Credit: FEMA via Wikimedia Commons

The transmission grid shown in the figure above shows the interconnection of power generating facilities with distribution sub-stations. The local distribution grid is designed to supply power to end users and usually has a radial structure. While some of the components of the grid are subject to renovation, it is not the physical structure of the grid that is the focus of current redesign efforts; it is the informatics component that is supposed to bring the grid to a new level of intelligence. Hence, the interactive combination of information technologies and transmission systems creates the smart grid system.

Introduction of the demand response technologies is especially relevant to the power supply for buildings. According to US DOE (DOE 2007), buildings in the US consume around 72% of total electricity, and sensitive regulation of building energy demand is considered a major factor in sustainable development. Transitioning buildings to the smart grid is a complex task, which requires efforts in three areas:

1. legislation to mandate the government and business actions;
2. standard and technologies enabling building-utility communications;
3. business model to balance the demand-response interactions. The following article describes how these three factors can be synergistically combined to radically change the way building electricity use is managed.

Based on what you learned from these readings, please answer the following self-check questions:

The demand response business models are currently being developed by many companies. Those models require all-system analysis, since successful feedback between the different actors is key to effective operation. Behavioral aspects are seriously considered because they eventually control the decision-making on both sides of the utility-customer chain.

Below are links to some recent studies and pilot programs that seek to promote a demand response approach in power management. Please look through those examples and take a note which parties actually benefit from implementation of those approaches. Are there economic drivers behind them?

• Jeff St. John, Innovari Wants to Make Demand Response the Same As an Independent Power Plant, June 9, 2014
• Stephen Lacey, Opower Expands Behavioral Demand Response to 1 Million Customers, May 20, 2014.
• Severin Borenstein, Peak-Time Rebates (PTR): Money for Nothing?, May 12, 2014
• Jeff St. John, Tendril Is Back: Could Nest and SolarCity Benefit From Its Microtargeting Model?, May 7, 2014.

The activity in the end of this lesson will involve assessment of demand response technologies, so the above-listed reports may be useful illustrations for that assignment.

When we talk about our energy future and contemplate the idea of eliminating fossil fuel combustion entirely and replacing it with cleaner renewable energy technologies, the key question everyone wants to know the answer to is:

Will renewables be enough?

The renewable resources - solar energy, wind, geothermal, biomass, hydro resources - are truly enormous. However, conversion of those resources to accessible, usable energy has a big "overhead". Creation, installation, and support of those technologies takes time, manpower, materials, and (you guessed it) more energy. The net consumable energy is what we hope to match with the existing global energy demand.

This question is very carefully addressed in the documentary "SWITCH" created by documentary director and writer Harry Lynch and Geology Professor Scott Tinker (University of Texas). The authors travel around the globe to visit the best state-of-the-art renewable and non-renewable energy facilities to understand the pros and cons of each and to put some numbers together.

One good thing about this film is that it does not push a certain political agenda and avoids polarized discussion about what types of energy should or should not be pushed forward. It attempts to take an objective look at the reality of the present-day energy situation, with its opportunities and challenges. Finally, and most importantly, it includes all pillars of sustainability in the discussion.

In this lesson, I ask you to watch this complete documentary (98 min) as part of your learning and provide your reflection on the discussion forum.

Please refer to the Summary and Activities page for further instruction on the Lesson 9 Discussion Forum.

In this lesson, we have learned about different elements of power grid system, current issues with maintaining stable power supply, and options for better flexibility and "smart" management of electricity generation and distribution. The demand response technologies are considered game-changing in the Smart Grid models, so we looked at some recent trends and innovations reported in that area. This lesson also touched on the subjects of base load power and energy storage, since both of those topics present key questions for the sustainability of electric power.

References for Lesson 9:

Sustainable transportation refers to not only vehicles, but also includes fuels, infrastructure to deliver distribute these fuels (pipelines, stations), road networks and railways. Assessment of the transportation system needs to address the system effectiveness to meet society needs and environmental load associated with employed vehicles and infrastructures. This lesson overviews three important topics: alternative fuels and their associated impacts, zero-emission vehicles and status of electric vehicle technologies, and perspectives of the mass transit in sustainable community.

Learning Objectives

By the end of this lesson, you should be able to:

• understand the choices of alternative fuels and list their pros and cons;
• explain the principles of technologies employed in zero-emission vehicles;
• compare performance of different transportation technologies by environmental and economic metrics.

Readings

Report: Boutwell, M., Hackett, D.J., Soares, M.L., Petroleum and Renewable Fuel Supply Chain, Stillwater Associates, 2014.

Book: National Research Council. Transitions to Alternative Vehicles and Fuels. Washington, DC: The National Academies Press, 2013. Sections 2.5 and 2.6.

Web article: Penalosa, E., Role of Transport in Urban Development Policy, Federal Ministry for Economic Cooperation and Development, 2005.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

Electric vehicle charging stations become more common across the US

Credit: White and orange gasoline nozzle by Mike B from Pexels is license under Legal Simplicity

Let us start with some facts (Source: Sierra Club, 2014):

• Every day, the U.S. uses ~400 million gallons of oil to move people, goods, and vehicles.
• There are ~230 million gasoline-fueled vehicles in the U.S. that travel average 12,000 miles per year.
• About 70% of all oil used in the U.S. is used for transportation.
• About 70% of all oil used in the U.S. is imported from the countries at "high risk" of instability.
• Every day, the U.S. sends about $1 billion abroad for oil expenses.

While the demand for transportation fuels is increasing, the continuing dependency of the U.S. economy on the foreign oil has put the country in an extremely vulnerable position with respect to meeting its transportation energy needs. This vulnerability is the critical motivator in searching for alternative fuels for vehicles and looking for alternative types of transportation as well. Sustainability of transportation basically means the flexibility and ability to provide for your own needs using the resources that are local, widely available, or renewable. What are the options there?

A number of alternatives (including both liquid and gaseous transportation fuels) have been a subject of research and implementation for the last few decades. Let us review the background behind those options. Click on the following links to read about the various classes of alternative fuels considered for transportation purposes:

1. Biofuels (biodiesel, ethanol)
2. Natural gas (NGV)
3. Hydrogen
4. Electricity

Any alternative fuels have advantages and disadvantages, which are briefly summarized in US DOE Data Table (U.S. DOE, 2024).

In this table, the fifth row shows an important metric used to characterize the fuel efficiency (not only transportation fuels) - energy content or energy density. It is measured in energy units per unit volume or unit mass of the fuel. For example, from the data in the table, we can see that diesel and renewable diesel fuels provide the highest amount of energy per gallon compared to other liquid fuels. At the same time, gaseous fuels typically have lower energy density. This metric is important to take into account in vehicle design: more energy-dense fuels will require less space and will weigh less while allowing higher range and better fuel mileage.

Alternative fuel supply chain and distribution

Viability of certain types of transportation fuels is closely related to the processing, supply, and distribution infrastructure. This is especially critical in the U.S. society and economy, which are heavily reliant on the usage of road vehicles for personal and industrial needs.

Over the last few years, the alternative fuel supply chain for road transportation was undergoing significant development, driven by various factors such as public environmental concerns, government regulations, and advancements in technology. In brief, these are the trends:

Electric Vehicles (EVs): EV adoption has been on a rise, with major automakers investing heavily in electric vehicle production. The charging infrastructure has been expanding, although it still faces challenges such as range anxiety and the need for further infrastructure development, particularly in rural areas.

Hybrid Vehicles: Hybrid vehicles, which combine traditional internal combustion engines with electric propulsion, continue to be popular, offering improved fuel efficiency and reduced emissions compared to conventional vehicles.

Hydrogen Fuel Cell Vehicles: Hydrogen fuel cell vehicles have gained attention as another zero-emission alternative. However, the infrastructure for hydrogen refueling stations is still limited, which has hindered widespread adoption. There are reasons to consider hydrogen fuel as a preferred option for large scale freight and marine transportation.

Biofuels: Biofuels, such as ethanol and biodiesel, have been in use for some time. They are mainly produced from renewable sources such as corn, sugarcane, or algae. While biofuels can help reduce greenhouse gas emissions, concerns have been raised about their impact on food prices and land use.

Natural Gas: Compressed natural gas (CNG) and liquefied natural gas (LNG) are used as alternative fuels for some vehicles, particularly in fleets like buses and trucks. However, the infrastructure for natural gas refueling is not as widespread as for traditional gasoline and diesel.

Synthetic Fuels: Synthetic fuels, produced from renewable sources or from the feedstock linked to carbon capture and utilization, have the potential to replace conventional fossil fuels. However, production costs and scalability remain significant challenges.

Transportation Emissions

Strong motivators for developing alternative vehicle technologies and fuels are growing emissions and alarming urban air pollution levels. According to US EPA, in 2017, CO₂ emissions from transportation sector surpassed the long-time leader – electric power sector – in the total national emissions budget. This change in “leadership” in part happened due to increasing addition of natural gas and renewable sources to the power generation mix while retiring older coal power plants in a number of states. Here is how the last half-decade of CO₂ data looks like:

Figure: CO2 emissions from fossil fuel combustion by sector .

(Data Source: EPA)

It is also estimated by EPA that nearly 60% of those transportations emissions in the United States come from passenger vehicles – cars, SUVs, and pickup trucks. There are economic reasons for that growth. In the late 2000s, the automobile emissions were moderated by the policies adopted by the Obama administration, which limited the amounts of gasoline the vehicles were supposed to use per mile. The Trump administration initially aimed at elimination of those fuel efficiency standards, which would most likely push future transportation emissions up. However, the proposal was recently revised, and after receiving comments from industry and public, the government did not eliminate the Obama standards, but adjusted them, to enforce only 1.5% annual MPG increase for passenger vehicles (as opposed to 5% under Obama regulation). The main argument for this change was that less stringent standards would make new cars more affordable, and thus increase driving safety for the families who would be otherwise be forced to drive older cars (USA Today).

Low gas prices have also been contributing to the trend, tempting Americans to drive more miles and purchase larger personal vehicles (SUVs and such), which typically have lower gas mileage.

From these data, we see two drivers behind increasing emissions: population growth in metropolitan areas and increasing time behind the wheel. Some areas do better than others in terms of limiting driving through encouraging alternative mobility options. One example is DC Metro area, which shows the drop in emissions per person. In spite of increasing total population and total emissions, people appear to drive less than in other urban regions with high reliance on suburban commute.

Curbing vehicle emissions will require several factors working in synch: more efficient cars, developing alternative engine technologies (e.g., electric, hydrogen, natural gas), and changing in human lifestyle. Cities and states look for expanding transit options, such as rail, bus, and subway services, as well as encouraging carpooling and vehicle sharing programs. It is also anticipated that in 2021, New York will become the first city in the US to adopt a congestion pricing plan to discourage drivers from entering the busiest areas of the city.

The concept of zero-emission vehicles is typically attributed to the transportation options that do not result in any harmful emissions during vehicle operation. Harmful emissions are defined as those known to have a negative impact on the environment or human health. They can include carbon dioxide, carbon monoxide, nitrogen and sulfur oxides, ozone, various hydrocarbons, volatile organic compounds (VOC), heavy metals in volatile forms (e.g., lead, mercury, etc.), and particulate matter.

Typical examples of zero-emission vehicles are electric (battery-powered) cars, electric trains, hydrogen-fueled vehicles, and human / animal powered transportation (e.g., bicycles, velomobiles, carriages, etc.). The battery technology for electric vehicles is based on charge/discharge cycles, meaning that the battery is charged beforehand using an electricity source and is discharged during vehicle operation. Because electricity production may involve some emissions, there is also a concept of well-to-wheel emissions, which includes not only operating emissions, but also those associated with the fuel source and other stages of the vehicle operating cycle. So, the "zero-emission" term is conditional in that sense.

A demo plug-in battery hybrid vehicle by the stationary charger

Credit: Ryu Hayano via Flickr

The hydrogen-fueled vehicles are typically based on fuel cell technology, which imply electrochemical conversion of the fuel energy into electricity (as opposed to combustion). As a result, the only emissions of fuel cell operation are water and heat, which are not classified as harmful and therefore allow placing the fuel cell transport vehicles in the zero-emission category. The same as electric vehicles, fuel cell vehicles shift the emissions to the stage of fuel production. Thus, manufacturing of hydrogen gas via reforming of natural gas results in CO₂ emissions, which must be taken into account in the life cycle assessment.

A military car with a fuel cell stack in the rear compartment.

Credit: Office of Naval Research via Flickr

However, there is a possibility of designing a sustainable zero-emission lifecycle for electric and hydrogen vehicles, if electricity for recharging the batteries is supplied from renewable sources such as wind, solar, hydro-power converters, and the hydrogen to power fuel cells is produced via electrolysis or other emission-free technologies.

The energy conversion technologies that support the electric vehicles rely heavily on special chemistry and materials necessary to facilitate the efficient charge transfer processes. Understanding the components and principle of those technologies is important to foresee potential barriers on the way to their wide implementation and commercialization. The following learning materials will provide you with the basic knowledge on how the battery and fuel cell systems work.

Li-ion battery technology for cars

A schematic representation of a generic Li-ion battery is given in Figure 10.1. Roughly, Li-ion cell consists of three layers: electrode 1 (cathode) plate (usually lithium cobalt oxide), electrode 2 (anode) plate (usually carbon), and a separator. The electrodes inside the battery are submerged in an electrolyte, which provides for Li+ ion transfer between the anode and cathode. The electrolyte is typically a lithium salt in an organic solvent.

Figure 10.1. Li-ion battery system and charge transfer processes.

Credit: Cepheiden via Wikimedia Commons / Mark Fedkin

During the charging process, a DC current is used to withdraw Li⁺ ions from the cathode and to partially oxidize the cathode compound:

LiCoO2 → Li_1-xCoO2 + xLi⁺ + xe^-

The released Li+ ions migrate through electrolyte towards the anode, where they become absorbed in the porous carbon structure:

xLi⁺ + xe^- + C₆ → xLiC₆

At the same time, electrons travel through the external circuit (electrolyte is not electron conductive).

During the battery discharge, the reverse process takes place. Li⁺ ions spontaneously return to the cathode, where electrochemical reduction occurs.

Please watch this short video for an animated illustration of the Li-ion battery principle:

If we compare the energy densities of the typical rechargeable Li-ion battery (~ 0.875 MJ/kg weight) and regular gasoline fuel (~46 MJ/kg), we can see that the gasoline beat battery electricity in potential to deliver power at least by a factor of 50. Thinking that typical engine is normally used at ~50% capacity, to match the capabilities of the internal combustion engine, the Li-ion battery has to be made at least 20 times more efficient, or the size of the on-board battery should be increased 20 times, which is a prohibitive option.

Limitations of the Li-ion batteries are rooted in the material properties.

For example, the LiCoO₂ ⇔ Li_1-xCoO₂ conversion is only reversible with x<0.5, which limits the depth of the charge-discharge cycle. But, with a wider variety of materials available, research is underway to develop new generations of Li-ion batteries.

For example, take a look at Sigma Aldrich website, which lists multiple alternatives for cathode, anode, electrolyte, and solvents.

Fuel Cell Technology for Cars

Fuel cell is similar to a battery in the electrochemical principle of energy conversion, but different in operational design. Instead of storing the reagents and products of chemical reactions inside, like batteries do, fuel cells operate on continuous inflows/outflows of reagents and products. In that sense, they are not limited by discharge time and can generate electricity non-stop as long as fuel is supplied. Hydrogen is the best-proven fuel for fuel cells, although its storage and supply imposes some constraints on this technology.

A schematic representation of a hydrogen/oxygen fuel cell is given in Figure 10.2. The main components of the fuel cell include: membrane electrode assembly, which consists of a proton-exchange membrane and electrodes (anode and cathode) attached to the membrane on each side, gas diffusion layers, bipolar plates, and supporting structure. The fuel cell electrodes contain dispersed catalyst particles (usually platinum), which are necessary to promote electrochemical reaction.

Figure 10.2. Polymer electrolyte membrane fuel cell structure and transport processes.

Click for a text description.

Parts from left to right: Hydrogen import and output tubes, silver coated terminal plate, bipolar carbon plate, carbon gas diffusion later, anode Pt(C) Proton-Exchange Membrane (PEM), cathode Pt(C), carbon gas diffusion later, carbon bipolar plate, silver coated terminal plate, oxygen intake and output tubes. Electrons flow from the terminal plate on the anode side to the terminal plate on the cathode side.

Credit: Mark Fedkin

A hydrogen-powered fuel cell combines hydrogen with oxygen in the electrochemical reaction to produce water and electricity. In case of direct contact of these gases, the reaction H₂ + ½ O₂ = H₂O is very active and generate significant amount energy (under certain conditions – explosion). In a fuel cell, hydrogen is separated from oxygen by a proton conductive membrane, so, in order to react, it is forced to transform into ionic form by losing electrons:

H₂ -> 2H⁺ + 2e^- - this reaction occurs on the cell anode.

Further, the formed hydrogen ions (protons) are transferred through the proton-exchange membrane, while electrons are transferred through the external circuit, where they can be harvested as electric current. Once reaching the cathode, protons (H⁺) react with oxygen molecules, consuming electrons from circuit and producing water:

2H⁺ + ½O₂ + 2e^- -> H₂O - this reaction occurs on the cell cathode.

As long as the supply of reagents, hydrogen and oxygen gases is maintained, the process continuously generates electric energy and water.

Please watch the animated illustration of this process in the following video:

The productivity of this simple process, i.e., how much electricity a single fuel cell can produce, is limited by a few factors. First is the proton conductivity of the membrane. The membrane consists of a special polymer (for example, sulfonated tetrafluoroethylene, Nafion®) which performs as an ionic conductor only under specially controlled temperature and humidity regime. This and other polymers produced for such applications are quite expensive. Second, the platinum (Pt) catalyst is necessary to provide sufficiently fast kinetics of the electrochemical reactions. Platinum is a noble metal, which has high cost and limited availability.

When it works, the fuel cell process is very efficient (80-90% efficiency) and can generate electricity pollution free and with no mechanical degradation to the cell components.

For quite a while, battery- and fuel-cell-operated cars were parallel track for future implementation of electric automotive engines, and the advancement of one or the other depended on breakthroughs in materials and device efficiency.

To overview the current status and trends in these technologies, please refer to the following reading.

Sustainable community is a term usually applied to a certain inhabited entity, a neighborhood, a town, or a city that is economically, socially, and environmentally healthy and resilient. The typical feature of a sustainably developing community is a holistic approach to meeting the local society needs, as opposed to fragmented efforts, which focus on one specific need and ignore others. Ideally, a sustainable community should have a better quality of life, which is built upon responsible and organized citizenship of its members (not on businesses compromising well-being of other communities. A sustainable community also provides economic security through reinvestments in the local economy, diverse and financially viable economic base, sustainable business (PCSD, 1997). The National Partnership for Sustainable Communities defined six principles of livability that make a community sustainable (PSC, 2014):

1. Provide more transportation choices.
2. Promote equitable, affordable housing.
3. Enhance economic competitiveness.
4. Support existing communities.
5. Coordinate policies and leverage investment.
6. Value communities and neighborhoods.

Availability of transportation choices is the number one factor mentioned on this list. It is interesting that transportation is one thing that becomes worse with economic growth. Other important parts of society development, like information, sanitation, manufacturing, and energy efficiency typically improve with economic development, but not transport. And now, especially, development of new mass transit options become a significant part of plans of orienting communities towards sustainable development.

Urban communities are essentially shaped by their transportation systems. Mainstream city planning in the U.S. has been based on the networks of motor roadways and personal car use, with public transit as second priority. In the second half of the 20th century, the car use and automotive fuel consumption steeply increased, as did greenhouse gas emissions from the transportation sector (~20-25% of world energy consumption). The sustainability of the current communities that are heavily reliant on car transportation becomes questionable for at least two reasons:

1. environmental impact - greenhouse gas emissions, air pollution, depletion of petroleum resource, increased land and water use demands; and
2. social impact - overdependence on cars for basic needs and commuting, limited infrastructure to support growing car culture, decreased quality and aesthetics of urban life.

Development trends were slightly different in Asia and Europe, where planning was influenced by lower availability of resources or land required for automotive culture. Traditionally, European culture is more reliant on mass transit and has invested more into it. Thus, the International Association of Public Transport (UITP) based in Brussels, Belgium, supports a holistic approach to urban transportation and advocates public transportation development in 92 countries worldwide [Source: Wikipedia / International Association of Public Transport]. On the average, transport emissions of a U.S. city are about 4 times higher than that in Europe and about 24 times higher than that in Asia (UITP, 2014).

Recent trends, however, show that public transit may be re-establishing its role in American metropolitan areas, as several factors suggest that transit may be a more sustainable transportation option (Rutsch, 2008). Incentives that may affect people's choice of public transit versus private cars may include economic benefits, convenience, and speed. Strategies to enhance these factors via new technologies, policies, and business models raise competitiveness of the mass transit.

Please refer to the following reading to learn about possible measures and strategies to make the public transportation more attractive in urban settings.

According to experts, modification of public transit systems through introducing new technologies would be a critical step in meeting the world's future mobility needs. The future urban transportation networks should help cities lower their per capita carbon footprint, make cities more livable by easing commute, and increase accessibility and safety. The Sustainable Cities Institute names “holistic transportation” one of the key principles for urban sustainability. Holistic transportation planning with environment in mind means that besides vehicles themselves, planning should include such elements as streets, sidewalks, pedestrian spaces, bicycle routes, and enabling technologies for private and public fleets.

The following video features a few innovations related to long-distance and short-distance transit, which are discussed in the context of sustainable city planning. Although some technologies and ideas sound and look somewhat futuristic, others started their way up the TRL scale and get much closer to commercialization.

A couple of points / questions to focus on while watching the video:

• See how the new ideas for transport technologies are evaluated. What criteria and metrics make the top of the list?
• Try to watch critically and recognize both GO and NO-GO factors for these technologies in the future.
• What role is played by policy and city planning in the implementation of new transportation ideas?

As 95% of transportation energy currently comes from petroleum, significant restructuring of the transportation sector would be required to reach sustainable operation in the future society. This is one of the areas where breakthrough in technologies are in the highest need, and success in research and implementation of those technologies in the nearest ten to fifteen years would dictate what vehicles the next generations will be driving. Strong reliance of vehicles on infrastructure of fuel supply makes the problem of transition to new transportation technologies even more complex. The activity in the end of this lesson touches upon some key technologies employed in zero-emission vehicles, which may or may not become a significant part of the future transportation system. You get a chance to explore this question on your own and make your prediction.

References for Lesson 10:

Analysis of sustainability systems requires broad knowledge of technologies that provide for the urgent needs of society. But, even more so, it requires well-balanced thinking that encompasses causal connections and factors both within and outside the apparent system boundary. How do we appropriately account for various environmental, economical, and social concerns? What strategy should we choose to promote sustainability ideas to society? Which technologies would be optimal for addressing local needs and building a sustainable market? All these and other questions are subject to decisions at the levels of policymaking, business development, and community development. In this lesson, we will study factors that influence human decision with respect to innovations and technology. In the end, we get to see that the human factor is a key leverage point that can control the dynamics of the whole sustainability system.

Learning Objectives

By the end of this lesson, you should be able to:

• identify the factors that affect human decisions with respect to innovation and technology;
• set up a framework for collaborative decision-making on a specific problem;
• articulate the fundamentals of the Diffusion of Innovation theory;
• analyze the role of the technologies in the dynamic feedback within the global sustainability context.

Readings

Business report: Network for Business Sustainability, Making Sustainable Choices. A Guide for Managers, 2012.

Website: Structural Decision Making, Compass Resource Management Ltd., 2014.

Journal article: Simpson, L., Community Informatics and Sustainability: Why Social Capital Matters, J. Community informatics, 1(2) (2005).

Book Chapter: Sterman, J.D., Sustaining Sustainability: Creating a Systems Science in a Fragmented Academy and Polarized World, in Sustainability Science: The Emerging Paradigm, Weinstein, M.P. and Turner, R.E. (Eds.), Springer Science+Business Media, LLC 2012.

Questions?

If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.

The process of collaborative decision making is aimed at combining the input from all stakeholders and therefore at making the best choice from the standpoint of the objectivity. It is typical that decisions made by groups differ from those made by individuals. However, there is no clear indication that the group decisions are consistently better (or worse) than individual decisions. Also, collaborative decisions are apparently linked to group behaviors, interactions between members, role distribution, and psychological factors that can affect people's thinking.

The decisions regarding policies, economic actions, and assessments of alternatives for sustainable development especially require collaborative thinking due to the complexity and polarity of factors and interests involved. Design of the decision making process is therefore an important issue to learn for managers, policymakers, and experts involved in evaluation of business alternatives.

Study the following reading material based on the research of the Network for Business Sustainability (nbs.net), which examines the factors that steer people towards or away from sustainable choices.

The discussion forum in the end of this lesson will involve you in a self-evaluative exercise where you can try to recognize your own bias towards any theme in sustainability or related technology.

Structured Decision Making (SDM) methodology

Structured Decision Making (SDM) is a specially developed organized approach to making complex decisions. For example, when we face a choice of developing and implementing a new technology (versus an older status-quo technology), that is certainly considered a complex decision. Assuming that reaching high sustainability level is the focus of our decisions, technical feasibility, economic viability, environmental impact, and social impact are the main cornerstones of such an assessment, as we learned before. The SDM method is designed to organize information and direct the process of collaborative decision making towards the optimal solution, and helps to eliminate bias and find win-win scenarios if those exist. SDM was proved to be especially beneficial for the organizations that require transparency and efficient response to diverse public needs.

Please study the materials on the SDM website, referenced below, starting with SDM Overview, which explains in more details the purpose and structure of this method. Then proceed to the pages describing Steps and Tools used in the SDM analysis. Make sure to open the "Read More" links on those pages to study details.

In the end of this lesson, you will be asked to perform an activity related to the SDM framework. 

Social networks, both inter-personal and virtual, are known to have a strong influence on people's life, behavior, and choices. This influence can take any direction, negative or positive, conservative or destructive, depending on the network dynamics and trends. Lately, significant attention has been paid to the opportunities related to the promotion of sustainable behaviors through social networks.

As was shown by some community models (Xu et al., 2012), physical and social networks within which residents are connected and influence one another via certain relationships tend to foster notable savings in community energy consumption. Interestingly, the interpersonal closeness between members in the community, identified as a place-affiliated network, was found to create leverage for encouraging energy conservation behavior. Based on this study, the primary spheres of the community network include integrated buildings, occupant social networks, and surrounding neighborhood facilities. The integrated energy efficient building infrastructure is shown to have the potential for 2.3-22.3% energy savings; however, a social network is noted as an even more powerful factor, resulting in additional 11.7-31.1% of energy savings, when energy awareness is promoted through the interpersonal relationships (Xu et al., 2012). Social encouragement is seen as a more cost-effective way to energy conservation than physical upgrades and renovations. The residents are seen to be motivated to conserve energy when they are aware if their neighbors and friends are changing in similar ways. The third sphere of the community network - surrounding neighborhood facilities - are shown to promote social networking and its benefits. These facilities provide additional channels for people to communicate, and also provide physical grounds for shared monitoring systems and shared appliances and services.

Similarly, the social networks may play an important role in the diffusion of innovative technologies. Diffusion of Innovation is a theory describing patterns of technology adoption to society and predicting whether a particular innovation can be successful or not (Rogers, 2003; Kautz, 1999). The theory emphasizes the process of communicating an innovation through various channels in a social system. The four key elements that influence the spread of a new technology or idea are (i) innovation, (ii) communication channels, (iii) time, and (iv) social system (Rogers, 2003). Rogers also identifies five main steps in the innovation adoption process; those steps are: awareness, interest, evaluation, trial, and adoption. Theoretical timeline of technology adoption is illustrated in Figure 11.1.

Figure 11.1. Dynamics of technology adoption according to the Diffusion of Innovation theory. The blue curve shows the gradual adoption of a new technology in % shares by different groups of people. Yellow curve shows the technology market share, which is eventually saturated.

Credit: Based on Rogers, E. (1962) Diffusion of innovations. Free Press, London, NY, USA. Licensed under Public domain via Wikimedia Commons

The Diffusion of Innovation theory puts the importance of the social networks and interpersonal channels above the mass media when it comes to adoption decisions, emphasizing several key agents - opinion leaders, electronic communications, social and organizational hierarchies - as triggers for change. There is an observation that people often evaluate a new idea based on the subjective recommendation by someone like themselves, who has evaluated and adopted that idea previously (Simpson, 2005).

The following article is a case study exploring the role of social involvement in the adoption of ideas of technology and sustainability. It provides an example of an application of the Diffusion of Innovation theory to rural communities in Australia.