Considering that this course is called “Energy and Sustainability in Contemporary Culture,” let’s start by answering two fundamental questions:

• What is energy?
• What is sustainability?

Energy

Let’s tackle the second question first, since the answer is a little more straightforward, even if it’s not always easy to grasp: What, exactly, is energy?

Energy is most commonly defined as "the ability to do work." This is a useful technical definition, but from a practical perspective, the NEED Project's indication that energy is also "the ability to produce change" is helpful. A similar way to think of energy is that it "makes things happen." Energy is required to make a TV turn on, a furnace to generate heat, a teenager to roll their eyes at you (Wait, is that only me?), the sun to generate light and heat, water to vaporize, plants to add biomass, a power plant to generate electricity, and for you to think about this course content as you read it. And even if these things are not actually happening, energy provides the ability to make them happen.

As indicated in the reading, the two categories of energy are potential (stored energy) and kinetic (energy in motion), each of which have several forms. (Note that the categories are listed in parentheses below because they can either be included or not, e.g., chemical energy can be referred to as "chemical" or "chemical potential" energy. Generally, "kinetic" or "potential" is not included.):

• Chemical (potential) energy is stored in the bonds between atoms and molecules. Common examples include the energy stored in food, fossil fuels, and batteries, but anything that is made of more than one atom has chemical energy. Practically speaking, basically everything made of matter has chemical energy.
• Mechanical (potential) energy is "stored in objects by the application of a force." Common examples include a wound spring, a stretched-out rubber band, and compressed air.
• Nuclear (potential) energy is "stored in the nucleus of atoms," and is what holds the nucleus together. Anything made of matter has nuclear energy, but most of the nuclear energy converted by humans comes from the fission (splitting) of uranium atoms and is used to generate electricity. Most of the energy used by humans, however, comes from nuclear fusion (fusing of atoms) in the sun.
• Gravitational (potential) energy is "energy of position or place." Common examples include water (e.g., in a river) at a high(er) elevation, a ball sitting on top of a hill, and you sitting on your chair right now. If you see naturally flowing water, it is moving down hill (tides and waves notwithstanding), so hydroelectric energy (electrical energy generated from flowing water) starts out as gravitational potential energy.
• Electrical (kinetic) energy is "the movement of electrons." The most common example of this is electricity moving through a wire, but discharging static electricity and lightning are also electrical energy.
• Radiant (kinetic) energy is also called "electromagnetic energy." It travels in transverse waves and is produced by anything with a temperature above absolute zero. Common examples include light, sunlight, microwaves, radio waves, and radiant heat emanating in all directions from a fire.
• Thermal (kinetic) energy is the vibration of the molecules of a substance. As an object or substance gets heated up, the molecules vibrate more rapidly, and they slow down as it cools down. Humans cannot see this vibration because it happens at a molecular level, but we can feel it, or at least the results of it. Have you ever accidentally touched a hot stove and gotten burned? That unpleasant sensation is the result of the quickly vibrating molecules of the stove imparting their thermal energy into your skin. Anything above absolute zero has thermal energy, so it is all around us all the time, including everything you see right now.
• Motion (kinetic) energy is the energy in moving objects. Anything with mass that is moving has motion energy. Moving cars, flowing water, a falling object, and even wind (air is made of matter, after all!) are common examples.
• Sound (kinetic) energy moves in waves and is produced by vibrating objects. When you hear something, it is the result of the bones in your ear absorbing and converting these waves into motion energy, which your brain then interprets as sound. Despite what you may have heard, if a tree falls in the woods and there is no one there to hear it, it does generate a sound! Well, it generates sound energy, at least.

Energy efficiency and conservation of energy will be addressed later in this lesson.

The gentleman in this video also provides useful information regarding energy and illustrates many of the concepts from the reading above. (In case you are wondering, yes, he is this excited all the time. He also has a number of really good videos regarding many topics. His YouTube channel has over 8,000,000 subscribers, so he must be doing something right!). Please note that you can open this video in YouTube by clicking on the title of the video in the window below.

Video- What Is Energy? (4:35 minutes)

Okay, so if you ask a physicist or energy expert what energy is, she will likely tell you that energy is the ability to do work. This sounds straightforward enough, but you may be thinking, “what is work?” Ask the same (or another) expert, and you will likely hear: “Work is the transfer of energy.” The video below from Kahn Academy (3:16) is optional but does a good job of explaining what this means. If you are still a little confused after watching it, you may want to read through the rest of the energy lesson, then go back to it. The formulas are not important for this course, but the concept of how work is related to energy is important. One thing to note: the narrator uses the term "Joule" a lot in this video. A Joule (J) is the international unit of energy and is simply a way to quantify energy. (More on quantifying energy shortly!)

In order for an object to gain or lose energy, work must happen. If you pick up a book from the ground and put it on a table, the book gained gravitational (potential) energy. You performed work on the book, and the amount of work is equal to the amount of potential energy gained. When you pull your car or bike out from a parking spot, the car/bike has motion energy, but when it was parked had none. That energy gain is the result of work done by the car engine (then drivetrain and wheels) or your legs (then pedals, chain, and wheels), and you can figure out the work done by considering the velocity and mass of the moving object. When the vehicle stops, the bike/car performs work on the road and tires, resulting in them heating up.

The sun is constantly generating massive amounts of radiant energy. That energy is provided by hydrogen atoms fusing together into helium and releasing nuclear energy. The amount of radiant energy generated in this process is equal to the amount of work done by the hydrogen atoms on the sun. When this sunlight hits your skin (or any object), it performs work on it, resulting in a gain in thermal energy. This gain in thermal energy is equal to the amount of work done.

I could go on and on, but the key thing to remember is that energy transfer requires work. Any time energy is transferred from place to place or from one form to another, work must be done, and the amount of work is equal to the amount of energy gained or lost.

Forms of Energy

It can be easy to get bogged down by the formulas used to calculate how much work is done, when, by whom, and to whom. Since this is not a physics class, let’s not dwell on those. As described on the previous page, a somewhat simplified, but very useful way to think of energy is that “energy makes things happen.”

We could go on and on. But as you probably know, these are all examples of kinetic energy, or “energy of motion.” As stated in the reading and video, there are also a number of types of potential energy. Think of some examples of potential energy around (and in) you right now. You are able to move and think because of chemical (potential) energy inside of your body. In fact, everything around you has chemical potential energy. Any object on the wall, on a table, attached to the ceiling, or just above the ground has gravitational (potential) energy because it is above the ground. There is also nuclear (potential) energy in all matter because all matter has at least one nucleus. Again, we could go on and on, but the point is that everything around you has potential energy - nuclear if nothing else - and thus has the ability to do work, i.e., “to make things happen.”

Conservation of Energy

One of the foundational concepts in the understanding of energy – and something that is very important in the context of this course – is the First Law of Thermodynamics. The simplest way to put the First Law of Thermodynamics is that “energy cannot be created or destroyed – it can only change forms.” This is often referred to as the “Law of Conservation of Energy,” for obvious reasons. Practically speaking, this means that all energy came from somewhere else, and that it does not disappear when it is “used.”

All of the examples of energy that were noted above came from somewhere else. The light coming from a light bulb is converted from electrical energy running through a wire. The heat radiating from non-living things around you was absorbed from another source such as sunlight or the heating system of the building. The motion and electrical energy your body has right now comes from the chemical energy inside of your body. The gravitational energy of things around you came from motion energy required to lift the objects. And so on. And recall that each time energy was transferred, work was done.

Of course, this also means that all of the previous forms of energy also came from somewhere else. Where do you think the electricity used to generate the light coming from the screen came from? It almost certainly came from a power plant somewhere. But where does the power plant get its energy from? If you live in the U.S., chances are it came from either coal, natural gas, or nuclear material (about an 80% chance nationally, but it depends on where you live).

Let’s assume the electricity in question is from a natural gas-fired power plant. If so, the electricity used to generate the light on the screen you are looking at right now was originally chemical (potential) energy stored in the molecules of natural gas. Note that before it was converted to electricity, it went through a number of conversions, including being burned (thermal and radiant energy), and spinning a turbine (motion energy). But let’s not stop there. Where did the natural gas get its energy? Before we answer this, please read the short readings below.

Natural gas is formed from the remains of living organisms over millions of years, as are coal and oil. Most of this is from photosynthetic organisms, such as plants and phytoplankton (e.g., diatoms). If so, then the energy came from the sun. If it was an animal that formed the gas, then the energy came from what the animal ate to gain that energy, i.e., a plant or another animal. If it ate a plant, then that energy originally came from the sun, but what if it ate another animal? That animal either got its energy from a plant or another animal.

Figure 1.1. Electron microscope image of diatom (right) and pollen (spikey thing next to the diatom). Note the scale provided, which indicates that the diatom is about 50 micrometers long and 10 micrometers wide. Incredibly, oil is largely made up of innumerable dead diatom (and other micro algae) carcasses!

Credit: Berezovska, CC BY-SA 4.0 International

What this boils down to is that no matter how you slice it, all of the energy in natural gas came from the sun. The implications are kind of mind-boggling (and let’s face it, awesome): The light energy coming from the screen you are looking at right now probably started out as sunlight that hit the earth millions of years ago!

Figure 1.2: The Lakeside Power Plant in Linden, Utah, burning ancient sunlight. It converts natural gas into electricity.

Credit: Mscalora, CC BY-SA 4.0

Again, we could go through innumerable examples of energy, and most of them would require tracing multiple steps to find their original source. Almost all sources (aside from some nuclear energy and some geothermal energy) can be traced back to the sun, whether it’s recent or ancient sunlight. But more importantly in the context of this course is that:

• all energy comes from somewhere else, and
• energy is a quantity of “something” that takes many forms and can be converted from one form to another.

As the saying goes, “there ain’t no such thing as a free lunch.” In other words, when we “use” energy, that energy must come from somewhere else, and it does not disappear, it is converted to another form.

Good to Know

Almost all of the energy used on earth came from the sun, but where does the sun get its energy? Sunlight is nuclear energy released when atoms of hydrogen fuse to form helium, in a process called fusion. This reaction releases a HUGE amount of energy - the surface of the sun is nearly 6000 °C (more than 10,000 °F), and the core is more than 20 million degrees C (36,000,000 °F)!

Figure 1.2: Solar Corona

Credit: U.S. National Aeronautics and Space Administration

It should be clear by now that energy can take many different forms and is often converted from one form to another. Though different forms of energy cannot always be used the same way (ever tried to watch TV by plugging into a lump of coal?), you can always express the amount of energy present in different forms using the same units by using unit conversions. There are many energy units, but the most common unit you’ll see in the U.S. is the British Thermal Unit or Btu. Joules are considered the international unit of energy (you may see these from time to time in the U.S.), but since we like to make things difficult for scientists in the U.S. by using English units instead of metric, we’ll stick mostly to Btus in this course.

A Btu is defined as the amount of heat required to heat up one pound of pure water one degree Fahrenheit. To give you some perspective, a single match releases about one Btu if it is allowed to burn entirely.

The following are examples of commonly used energy equivalencies, i.e., unit conversions:

• One kilowatt-hour (kWh) of electrical energy is equivalent to exactly 3412 Btus of energy.
• Each time you burn a gallon of gasoline in a car, you convert approximately 120,000 Btus to other forms of energy (mostly as waste heat, it should be noted).
• Every 100 cubic feet (ccf) of natural gas that is burned releases approximately103,700 Btus of energy. (Note that 1 ccf = 100 cubic feet, so there are approximately1,037 Btus in 1 cubic foot, or cf).
• You know the calorie labels on the side of packaged food? Those are actually kilocalories, and each one is equivalent to just under 4 Btus of energy.
• There are about 1,055 Joules (J) in 1 Btu.

These are but a few examples - you can pick any amount and any form of energy, and it can be converted to Btus or any other energy unit. The US EIA has a useful unit converter.

This is useful in many ways, one of them being that it is possible to tally up all of the energy “used” by a given person or group of people – including a city, state, country, continent, or even planet – and convert that number to a single quantity to see how much energy is being used. Further, it is often possible to separate total energy use into categories to compare uses. This can provide a nice snapshot of energy use and can tell you a lot about the energy regime in an area, including how much is being wasted.

Visualizing Energy Use

The U.S. Department of Energy (DOE) is part of the Executive Branch of the U.S. government. According to whitehouse.gov: "The mission of the Department of Energy (DOE) is to advance the national, economic, and energy security of the United States." The DOE is another excellent source of information (the US EIA is run by the DOE). In addition to providing information, the DOE funds a lot of research, much of which is performed by people in the national labs. There are 17 national labs in the U.S., each with a different research focus. The national labs host some of the top researchers in the U.S., and because they are funded by taxpayers, all of the non-sensitive information is published for free. These are great sources of reliable and cutting-edge information. (Feel free to browse the national labs' website.)

Apropos to our discussion of energy use, Lawrence Livermore National Lab (LLNL) in California publishes annual energy use data for the U.S. and often for U.S. states. The image below (click on it to see a larger version) shows the most recent estimate of energy use in the U.S., divided by source. IMPORTANT: LLNL uses quads as their fundamental unit. As mentioned in a previous reading, a quad is a quadrillion Btus, which is 1,000,000,000,000,000 BTUs, or 1 x 10¹⁵ Btus. (Side note: This is one of my favorite charts! I appreciate the amount of information it provides and the ease with which it can be interpreted. It tells a robust - and important - story about energy use in the U.S. I can't be the only one that has favorite charts, can I? Anyway, moving on...) This is 2023 data, but the 2024 data have not yet been published.

Figure 1.4: Estimated U.S. Energy Use in 2023: ~100.3 Quads

Click for a text description of Figure 1.4.

The "blocks" on the left are energy sources (2022 quads in parentheses):

• Solar: 0.89 quads (1.87 quads)
• Nuclear: 8.1 quads (8.05 quads)
• Hydro: 0.82 quads (2.31 quads)
• Wind: 1.5 quads (3.84 quads)
• Geothermal: 0.12 quads (0.21 quads)
• Natural Gas: 33.4 quads (33.4 quads)
• Coal: 8.17 quads (9.91 quads)
• Biomass: 5 quads (4.88 quads)
• Petroleum: 35.4 quads (35.8 quads)

The pink blocks on the right are end-use sectors (note that electricity is NOT an end-use sector) 2022 use is in parentheses:

• Residential: 11.3 quad (12.3 quads)
• Commercial: 9.3 quads (9.67 quads)
• Industrial: 26.1 quads (26.7 quads)
• Transportation: 28 quads (28 quads)

The grey blocks to the far right indicate whether or not the energy was successfully used ("Energy Services") or wasted ("Rejected Energy"). 2022 use is in parentheses:

• Rejected Energy: 61.5 quads (67.3 quads)
• Energy Services: 32.1 quads (33 quads)
• All of the numbers in the chart indicate total energy flows or uses.

Credit: Lawrence Livermore National Laboratory

You can click on the chart to open a larger version in a new window.

The "blocks" on the left are energy sources (also called primary energy), the pink blocks on the right are end-use sectors (note that electricity is NOT an end-use sector), and the grey blocks to the far right indicate whether or not the energy was successfully used ("Energy Services") or wasted ("Rejected Energy"). All of the numbers in the chart indicate total energy flows or uses. Think of this as a flow chart - follow the lines from left to right to see how energy is used in the U.S.

Let's look at coal as an example. (Find coal on the left side of the chart, then follow the lines coming from coal on the chart and observing the numbers associated with those lines.):

• The U.S. used about 8.17 quads of coal in 2023 (this is up from 9.91 quads in 2022, 10.5 quads in 2021, and down from 17.9 quads in 2014, by the way).
• Of that, 7.24 quads (88.6%!) were burned to generate electricity, and
• 0.91 quads were used in the industrial sector (mostly to create heat for things like making steel), and
• 0.01 quads were used in the commercial sector

You can see where each energy source was "used" by following the chart. Oil is mainly used in the transportation sector but is used in all others as well. Natural gas is used in many sectors too. Nuclear is only used for electricity generation. All of this can be seen by following the energy sources on the left to the end uses on the right of the chart. This type of diagram is called a Sankey diagram and can be used for any number of purposes. Lawrence Livermore creates Sankey diagrams for each state, and many countries have diagrams as well. There are even some used to describe water and carbon flows in the U.S. At any rate, it is a useful tool for analyzing energy and other resource flows.

Other Resource Flows

If you are interested, LLNL publishes charts for other resource flows, including water and carbon dioxide. Click here for additional charts.

Though many forms of energy can be converted to many others, it is important to consider how efficient the conversion process is. Energy efficiency is the percentage of "useful" energy that is converted from another form.

For example, have you ever thought about what it means to have an "efficient" light bulb, like a light emitting diode (LED)? Think about it - the purpose of using a light bulb is to provide light. Seems obvious enough, but did you know that about 90% of the energy used by an incandescent light bulb is actually converted to heat? Only about 10% is converted to light, which means that incandescents are about 10% efficient. If you are still using these old-style light bulbs, you are wasting about 90% of the money you spend on the electricity used, unless you are purposefully using them to heat your house (this is a very expensive way to heat your house, by the way). This is one reason why CFLs have become so common, and now LEDs ("light emitting diodes") - both of them are around 40% - 45% efficient, which is 4 - 4.5 times as efficient as an incandescent.

Good to Know

Figure 1.5: Four common types of light bulbs. Note that the "energy-saving" part of the "energy-saving incandescent" is a relative term. They are more efficient than the old incandescents, but much less efficient than LEDs and CFLs.

Credit: U.S. Environmental Protection Agency

Consumers have a wide array of energy efficient lamps available to them. In addition to using electricity more efficiently, CFLs last about 10 times longer than incandescents, and LEDs around 25 times longer.

Efficiency considerations can be made for anything that uses energy. An efficient car is one that gets a lot of miles (useful "output") per gallon (energy input). An efficient home heating system, such as an electric heat pump, releases a lot of heat energy (output) for each kilowatt-hour of electric input. TVs, cell phones, airplanes, refrigerators, you name it - all have a certain efficiency. It can be used in other contexts as well. If you are efficient at work, you get a lot done (output) in a short period of time (input). In an efficient outing by a baseball or softball pitcher, not many pitches (input) were required to retire the batters (getting outs is the useful output).

This leads us to one aspect of the Second Law of Thermodynamics. A full explanation of the 2nd Law goes beyond the scope of this course, but you are welcome to watch the video below (9:29) from the Kahn Academy for a short explanation. One application of this law is that it is impossible to convert energy into a more dense, useful state without adding energy to the system. As Dr. Eric Zencey of the University of Vermont describes it, "the capacity of the energy to useful work is diminished" whenever it is transformed from one form to another (source: Is Sustainability Still Possible? p. 73). In other words, when energy is converted from one form to another, it is impossible to convert all of it. Some is "wasted" in another form, usually heat.

Let's continue with the lighting example to illustrate this. When using a light, electrical energy is converted almost entirely to light and heat (there may be a little sound energy thrown in there, but not much). Electrical energy is relatively dense, useful, and easy to control. You can store electrical energy in a battery. It is relatively easy to transport across distances without losing much. It can be used for many different things. But what about light and heat? Both of them are relatively diffuse and difficult to control. Neither is particularly useful for converting to other forms. It is very difficult to convert heat or light into another form with any kind of efficiency. Sure, you can convert heat back into electricity. In fact, this is exactly what happens in a typical power plant. But this process is very inefficient. Going further back, it is impossible to convert light, heat, or electricity back into coal (or oil, natural gas, or nuclear energy). Fossil fuels are very energy dense, and the molecules and atoms are neatly organized. Once the bonds are broken and the energy is released, there is no way to put it back together. That's the 2nd Law in action.

Here is another optional link regarding the 2nd Law.

Clearly, a lot of engineering goes into building a power plant. Despite the technical prowess required to convert coal into electricity, the process is extremely inefficient, as are all of the major forms of electricity generation in the U.S. and the world. Take a look at the chart below to see just how inefficient this process is for different fuels.

Figure 1.6: Industry-Wide Average Efficiency of Power Plants in the U.S. Click for a long description

Natural gas-fired power plants: Increased from 36% to over 43%. Coal-fired power plants: Stayed relatively flat at about 33%. Nuclear power plants: Stayed relatively flat at about 33%. Petroleum power plants: Stayed relatively flat at about 32%.

Credit: Copyright © Dan Kasper, 2024 Data Source: U.S. EIA

Link to Figure 1.5 data

As you can see, as the most efficient fuel, natural gas-fired power plants are just above 40% efficient on average. Coal is closer to 30%. This, of course, means that around 70% is wasted as heat. 70%! And this does not take into consideration the losses associated with transporting the electricity across long power lines, which in the U.S. averages around 5%.

Power plants are not alone in their inefficiency. The typical internal combustion engine of a car only provides around 20% - 25% of the energy from gas to move the car. New natural gas furnaces are very efficient (95%+), but many older ones operate at lower than 80% or even 70% efficiency. This is all poor energy management in principle - it's just plain wasteful - but it is also important for a couple of other reasons, one in particular. Specifically, there is a limited amount of all of these sources, and yet they are essential for modern society. In other words, coal, oil, natural gas, and nuclear are non-renewable energy sources. (To be fair, all indications are that the world will not run out of coal, natural gas, oil, or nuclear energy terribly soon, but no one knows when it will become too expensive to use. More on that later.)

The "Fifth Fuel" (Or Perhaps the "First Fuel")

One last note before moving on to renewable and non-renewable sources. Energy efficiency is sometimes referred to as the "fifth fuel." Why do you think that is? (Hint: coal, oil, natural gas, and nuclear are the four primary fuels used globally, though that is changing as renewables are used to a greater extent.)

Increasing efficiency reduces the use of other sources of energy. Efficiency is on the demand side of energy use because it affects energy demand (think of this as how much energy is "demanded" for use.) Energy sources are the supply side of energy use because they supply the energy. By reducing demand through energy efficiency, you reduce the need for supply, which is almost like having more supply, to begin with. Hence, it is sometimes referred to as the "fifth fuel." There are tremendous opportunities for energy efficiency improvements worldwide.

Some energy efficiency advocates refer to efficiency as the "first fuel," because they feel that it should be the top priority in terms of energy management. There is some strong validity to this. Consider that a report from the American Council for an Energy Efficient Economy found that it is cheaper to reduce energy use through efficiency than it is to supply energy by any other source. Very interesting reading, if you are so inclined (and only a few pages long).

Knowing whether a source of energy is renewable or non-renewable is important when considering energy and/or sustainability. Renewable energy is defined by the U.S. Environmental Protection Agency thus: “Renewable energy includes resources that rely on fuel sources that restore themselves over short periods of time and do not diminish” (Source: U.S. EPA). Non-renewable energy is energy that cannot restore itself over a short period of time and does diminish. It is usually easy to distinguish between renewable and non-renewable, but there are some exceptions (more on that in a minute).

Renewable Energy

It should be clear how most of these sources fit the definition of renewable energy ("resources that rely on fuel sources that restore themselves over short periods of time and do not diminish") and have various benefits and drawbacks. Please note that this does not provide a comprehensive list of pros and cons, but will give you a solid idea of many of them:

• Solar energy comes directly from the sun, which comes every day in most locations and does not diminish appreciably over time. Yes, the intensity does ebb and flow on short and long timescales, but it is hopefully not going away anytime soon. If the sun burns out and stops shining, we have bigger problems than solar panels not working!
  • Pros: A few benefits of solar energy are that it is relatively predictable and reliable, it is effectively limitless, and that it does not create any emissions/pollution when generating energy.
  • Cons: The main drawback is that it is intermittent, both in terms of the sun only being in the sky 50% of the time, and that weather can impact it significantly. Solar is also very diffuse, meaning that it is not very concentrated, and so, usually a large area is required to provide a lot of useful energy. Solar PV used to be very expensive but is now cost-competitive. Battery storage has become more affordable in recent years, which can help eliminate the intermittency problem.
• The wind gets its energy from the sun - it is caused mostly by differential heating across the surface of the earth - so cannot be "used up" either.
  • Pros: More good news is that the wind will never disappear as long as the sun shines and the earth is spherical, and like solar, wind does not generate emissions. Well-sited onshore wind is actually the least expensive form of electricity.
  • Cons: However, the wind is also variable - more in some locations than others - and is less predictable than solar energy in most locations. Again, battery storage is starting to mitigate this problem.
• Hydropower is the power in moving water and gets its energy from the sun as well and is even more consistent in most locations than the wind.
  • I want you to think for a moment how the energy in moving water started out as solar energy. (This is a good thought experiment in energy conversion.) Answer: Remember that water flows downhill, and so the motion energy in flowing water started out as gravitational potential energy. How does water get this potential energy, i.e., how does it get uphill? Mostly from evaporation caused by the sun!
  • Pros: In terms of other benefits, like solar and wind, hydropower does not generate emissions, and is very consistent and reliable in most locations, which makes it a good source of baseload power. Though it should be noted that some methane emissions result when organic material behind dams decomposes. Hydropower can also be ramped up or down relatively easily, which makes it useful for variable load demands.
  • Cons: There are some drawbacks associated with large hydropower installations (see the EIA's Hydropower and the Environment website for some examples), and in some cases, very big environmental and social drawbacks (e.g., in the Three Gorges Dam in China). All of these factors are important to keep in mind. Hydroelectricity is the single biggest source of renewable electricity in the world.
• One additional drawback of all of the above sources is that they are each location-specific. In other words, some locations may have a lot of sun, wind, and/or hydro, while others may have very little. (This will be addressed in more detail in a future lesson.) This problem can be at least partially solved by transporting electricity, but that is not always easy, and often expensive.

Figure 1.7: Cattle grazing next to a wind turbine. One underappreciated benefit of wind is that livestock such as cattle and sheep can safely use the land immediately surrounding the turbine. Many farmers across the world rent or own their own turbines.

Credit: Dirk Ingo Franke, CC-BY 2.0 Germany

All of these sources renew themselves over short periods of time and do not diminish. And though intermittent, none of these sources are going to disappear in the foreseeable future. They are textbook renewable energy sources.

Good to Know: Agrivoltaics

Agrivoltaics are a burgeoning systems-thinking application. Agrivotaics combines - you guessed it - agriculture and photovoltaics. Ground-mounted solar arrays are a great application of solar PV technology, but they do take up a lot of space relative to their energy output. So why not find a way to use all of this space? Enter agrivoltaics! With some careful design considerations (e.g. knowing which plants are shade-tolerant or even prefer some shade), crops can not only be successful but in some cases more successful in terms of production than when planted in an open field. This is particularly helpful in hot, dry climates, such as the eastern part of Colorado, which is pictured below. But it can be successful in more humid and cooler climates as well.

Agrivoltaics are becoming increasingly recognized and researched throughout the U.S. and internationally. Feel free to browse through the National Renewable Energy Laboratory's (NREL) article about agrivoltaics for more information.

Figure 1.8: Agrivoltaics operation in Colorado.

Credit: D. Kasper

Video: NREL’s Agrivoltaics Research: Combining Solar Energy With Agriculture

Combining Solar Energy With Agriculture

Click here for a transcript of the Combining Solar Energy With Agriculture video.

NARRATOR: Everyone likes growing things. Everyone likes to see a garden. I've been blown away by how much interest there's been by staff and researchers across the entire lab. Here we're exploring agrivoltaics, which is combining solar energy with agriculture. And agriculture can be vegetable production, it can be pollinator habitat, it can also be pasture grasses that can support animal grazing. We are able to look at eight different types of crops as well as two different types of pollinator mixes and two different types of pasture grasses. And what we're trying to do is compare how different types of vegetation perform under the open sun and open air as well as how they perform under the partial shade of the solar panels.

So we have fruiting plants like tomatoes and peppers. We also have root crops like carrots. And then we have leafy greens as well as herbs like basil. In many cases, solar projects are built on agricultural lands, and you could have a lot of push back from landowners or their surrounding communities who don't want to see prime agricultural land getting taken out of production. Agrivoltaics really offers us the opportunity to continue agriculture production while also producing clean electricity.

There's so much capability that the lab has and can contribute to this. And so being able to showcase this on campus, really, I think, will improve the science and improve the output that we can have. Some of the produce will be going into the NREL Cafeteria, especially the leafy greens like the kale and the chard. Much of the other produce will be donated throughout the communities for areas that lack adequate food access in the Denver Metro area.

Credit: National Renewable Energy Laboratory - NREL. NREL’s Agrivoltaics Research: Combining Solar Energy With Agriculture. YouTube. August 16, 2022.

Okay, so what about biomass and biofuels? They are both derived from living or recently living things (trees, corn, algae, sugarcane, etc.) They also get their energy from the sun (anyone sensing a pattern here?), and plants are usually pretty good at regenerating themselves. But I want you to take a minute to try to think about examples of biomass and/or biofuels that might not be "renewable," in the sense of the definition above. Can you think of any examples of non-renewable biomass?

Nearly all forms of biomass and biofuels are renewable. Corn-based ethanol is the most-used source of bio-based energy in the U.S. Corn can be grown in the same field year after year, so it is renewable. Whether or not it is sustainable is another question, which will be addressed later. The primary source of bioenergy in Brazil is sugarcane. Nearly all of Brazil's vehicles are able to use 100% sugarcane ethanol for fuel. (Contrast this with the U.S., where most automobile engines are only required to be able to handle up to 10% ethanol.) Sugarcane grows year-round in Brazil, so is definitely renewable.

There are many other biomass sources that fit our definition of renewable, including animal dung, algae (for biodiesel), jatropha nut, soybean, switchgrass, and more. Wood is used around the world as a source of heat, particularly for cooking. Most trees and shrubs regrow relatively quickly, so they are generally considered renewable. But even a fast-growing tree like an oak (up to two feet per year, according to the National Arbor Day Foundation) has limits. Though most biomass sources are considered renewable, keep this in mind: if you harvest a renewable resource faster than it regenerates, it will not be able to renew itself over time. We will revisit this point in a later lesson, but it is important to remember.

Not all Renewables Are Created Equal

Most renewable energy sources are carbon-free. This means that they do not emit any carbon dioxide when they generate energy. Solar, wind, and hydroelectric are carbon-free. Nuclear, though not renewable, is also considered a carbon-free energy source, because unlike coal and natural gas, it does not burn. As noted in a previous reading, nuclear energy generates heat through fission, not combustion. Biomass and biofuels are often considered carbon-neutral because they emit carbon dioxide when they are burned. So, why are they carbon neutral?

Figure 1.9: Carbon neutral wood pellets. This is printed on a bag of wood pellets, which are used for heating in a pellet stove. These emit CO₂ when burned, but effectively do not impact the level of carbon dioxide in the atmosphere. The pellets are made of leftover sawdust from timber operations. Note that CO₂ was emitted in processing, packaging, and shipping, so "carbon neutral" is a bit misleading.

Credit: D. Kasper.

There are a few interesting things to point out from the chart above.

• First of all, Total Primary Energy Supply (TPES) refers to all original or primary energy consumed. For example, if your electricity is supplied by a power plant, the energy your electronic device is using right now is not primary energy because the electricity was converted from an original source (e.g., coal, oil, natural gas, nuclear). Given that electricity generation is always less than 100% efficient (sometimes much less, per the previous section), the primary energy used by your device is greater than what shows up on your electric bill. Incidentally, the "energy sources" on the left-hand side of the sankey diagram that you looked at earlier this lesson are primary energy.
• Another interesting thing to point out is that "waste" (burning trash to generate electricity) is generally considered as renewable energy. In many parts of the world, including many states in the U.S., if you burn garbage to produce heat and/or electricity, it is considered a biofuel, and thus renewable. I'll leave it to you to think about whether or not that is reasonable. But note that biofuels (and biomass) constitute the majority of that "slice" of the global energy pie.
• Hydro is at only 5.83%. But where are wind and solar? We hear about them all the time in the U.S., and in other parts of the world. Wind and solar's contribution, while increasing many-fold in the past 25 years, contributes only about 3.3% and 2.8%, respectively. They have both been growing at an all-time high rate, but there is still a long way to go before wind and solar make a major dent in the global energy regime.

Figure 1.8: Sugarcane field in Brazil. Brazil is the world's leading producer of sugarcane and sugar-based ethanol. Even the waste material from the sugarcane extraction process can be used for energy generation, or to make secondary products like compostable plates and silverware.

Credit: José Reynaldo de Fonseco, CC-BY 2.5

Non-Renewable Energy

Non-renewable energy sources diminish over time and are not able to replenish themselves. In other words, they are finite, and once they are used, they are effectively gone because they take so long to reform.

You have already read about the four non-renewable energy sources: coal, oil, natural gas, and nuclear. Let's start with coal, oil, and natural gas, which (as you read earlier) are referred to as fossil fuels. Fossil fuels were created from the remains of dead plants and animals. The source material is renewable (it's biomass!), but since they take millions of years to form, they are not replenished over a "short" period of time, so are non-renewable. Fossil fuels are forming somewhere under your feet right now, but don't hold your breath waiting for them to finish.

The nuclear energy we use comes from an isotope of uranium called U-235. Unlike fossil fuels, U-235 has cosmic origins: it was formed by one or more supernovae around 6 billion years ago, about 1.5 billion years before the Earth was formed (a supernova is a collapsing star, "supernovae" is the plural form of supernova) (source: World Nuclear Association). Again, this is not renewable on a human timescale.

All fossil fuels emit carbon dioxide (CO₂) and other emissions when they are used to generate energy. Recall that they are made mostly of hydrogen and carbon, and the carbon mostly ends up as CO₂. Nuclear is considered carbon-free, because it is not burned, and it is not made of carbon. Remember that energy is extracted through fission or splitting of atoms. This generates heat, but no emissions. (It is important to note that it does result in very dangerous and long-lasting radioactive waste, but that will be addressed in a future lesson.)

To summarize:

Non-renewables

• Coal, oil, and natural gas are fossil fuels. Even though they all get their energy from the sun, none of them are renewable. They all emit CO₂ and other emissions when burned.
• Nuclear is also non-renewable, but not a fossil fuel. It is carbon-free but causes radioactive waste.
• Most importantly, for all intents and purposes, whatever coal, oil, natural gas, and nuclear exists today is all that we will ever have.

Renewables

• Solar, wind, and hydro are renewable and carbon-free, and effectively inexhaustible.
• Bioenergy is renewable and carbon-neutral. It emits CO₂, but no more CO₂ than was originally pulled from the atmosphere. Even though it is considered renewable, it is possible to use bioenergy unsustainably by harvesting it more quickly than it can be replenished.

Good to Know

We hear a lot about renewables and natural gas in the U.S., as their use has been growing rapidly for some time now. But as you can see in this chart from the EIA, coal and nuclear still constitute over 40% of all electricity generation in the U.S. Wind is an encouraging 10.2%. Solar, despite its massive growth and growth potential, is only 3.9%! We have a long way to go, people!

Figure 1.11: U.S. Electricity Generation 2023, by Source.

Click for a text description of Figure 1.11.

Natural gas: 43.1%; Coal: 16.2%; Nuclear: 18.6%; Petroleum: 0.8%; Renewables: 21.4% (Hydro: 5.7%; Wind: 10.2%; Biomass: 1.1%; Solar: 3.9%; Geothermal: 0.4%)

Credit: U.S. EIA

Hopefully, you now have a reasonably good grasp of what energy is, how it is used, where we get it from, whether or not it is renewable, as well as some good resources for finding energy information. I do not expect you to be energy experts, but it is important that you possess a good baseline knowledge of energy basics if you are going to critically analyze material that has energy information in it. There are many free information sources available, some of which I listed in the previous pages. If you have suggestions for other sources, feel free to share them.

Sustainability and Sustainable Development

Okay, time to shift gears and address sustainability. Unlike energy, sustainability (and “sustainable”) does not have a universally accepted definition. The phrase “sustainable development” is usually used to describe the goal of sustainability planning, and is often used interchangeably with the term “sustainability.” For the purposes of this course, the terms are effectively the same. Before we start really digging into the term, it’s good to start with the root word “sustain.” Dictionary.com's most relevant definition of sustain is:

“to keep up or keep going, as an action or process”

This lies at the core of the term, and is a good place to start. If something is being done that cannot continue to be done for the foreseeable future, then it is not sustainable. The devil is in the details, though, as we will see.

We could spend weeks analyzing the content of Engelman's chapter, but I would like to focus on a few key points.

1. The Overuse of the Term "Sustainability" and "Green"

First of all, what it means to be sustainable (and it's even fuzzier substitute "green") is open to interpretation at best, and misuse at worst. (Greenwashing is an example of such misuse, and will be addressed in more detail later in the course.) Since there is no single definition of sustainability, anyone is free to use the term to describe whatever they want, regardless of whether or not it is truly sustainable. Sustainable travel, sustainable consumption, sustainable underwear, sustainable food, green growth, green cars, greenhouses, green energy - as Engelman puts it, "frequent and inappropriate use lulls us into dreamy belief that all of us - and everything we do, everything we buy, everything we are - are now able to go on forever, world without end, amen" (p. 4).

How often do people stop and think about what it really means to be sustainable or green? Engelman points out, and I must say I agree, that too often it means "better than the alternative." But simply doing "better" is almost certainly not going to be enough to achieve a sustainable world. Hopefully, the content in this course will help you find out why!

2. The Brundtland Commission and Intergenerational Equity

Engelman also mentions the Brundtland Commission's definition of sustainable development:

This is the most commonly cited definition of sustainability/sustainable development, in part because it appeared in a book - Our Common Future, published in 1987 - that was the first organized international attempt (in this case, by the United Nations) to address what was widely seen as a global problem. Namely, the commission was tasked with analyzing and proposing solutions for the unsustainable course on which the world's societies were on. But it is also a good, concise way to sum up some primary goals of sustainability. Perhaps most importantly, it acknowledges the need to focus on the world that we leave to future generations. As Engelman puts it, we need to ask ourselves "whether or not civilization can continue on its current path without undermining prospects for future well-being" (p. 4). It is important to point out that not only does society need to simply "last" or "continue" for sustainability to happen, but that we need to consider the quality of life of people living in future societies. This concern is often referred to as intergenerational equity. We will investigate the quality of life in more depth in future lessons.

On paper, the goals indicated by this definition may seem pretty straightforward:

1. allow the current generations to continue to thrive,
2. improve the lots of those that are currently suffering, and
3. make sure future generations are able to meet their "needs."

But what is a "need," exactly? Is it meeting the bare essentials of survival, e.g., food, shelter, and clothing? Do I need to have a car? Do you need to have 3+ solid meals a day? Does your neighbor's family need that guest bedroom for when family visits? Do working Germans need to have four weeks of paid vacation each year? Does the mother or father in rural Kenya need a cell phone if there are no landlines? Does India need to update its outdated electricity infrastructure? It's hard to argue that any of these things are true needs, but if you asked each person in this situation, they would all probably say that they are, or at least that they are an important aspect of their lives.

Further, as Engelman brings up, to what degree do we sacrifice the needs and wants of the current generation in order to maximize the chances of future generations to live a good quality of life? Are you willing to impact your quality of life by buying fewer things, not traveling by airplane, not eating meat, living in a smaller house, not owning a car, and growing your own food, just so people in the future can live a better life? I would argue that some of these things actually improve the quality of life for you right now, but who has the right to decide what quality of life means? And how can we guarantee that any of this will work? None of these questions have easy, obvious, or even objectively correct answers, but they are all important to ask if we are to address sustainability.

3. Environmental Concern

There is something explicitly missing from the Brundtland Commission's definition (though it is implied) and from any part of the discussion so far, though it is mentioned in the book chapter. What about the natural environment? There are a few ways to approach this question - nature-centric (ecocentric) and human-centric (anthropocentric) - but for now, let's focus on the anthropocentric approach.

The anthropocentric sustainability implications of human concern for nature are concisely summarized by the US EPA when they note that "everything that we need for our survival and well-being depends, either directly or indirectly, on our natural environment" (Source: US EPA). We will investigate this further through ecosystem services in a future lesson, but the logic is impossible to argue against: If we destroy nature, we destroy ourselves. At the very least, the oxygen we breathe is generated by plants and other organisms like phytoplankton, and the food we eat is reliant upon soil and water, though there are many more things we currently depend on nature for. Many would argue that nature has value in and of itself (this is generally referred to as deep ecology or ecocentrism), but that goes beyond the scope of this course.

4. The Importance of Metrics

As Engelman stresses throughout his chapter, if we are to know whether or not we are living sustainably, we must measure it. In his words, sustainability "must be tied to clear and rigorous definitions, metrics, and mileage markers." If we do not define and measure it, how can we know whether or not we are closer or farther away from achieving it? These are often called metrics or indicators, and there are many of them, including levels of biodiversity, pollution levels, quality of life metrics, economic indicators, percentage access to clean water and energy, and more. Engelman mentions concentrations of carbon dioxide (CO₂) in the atmosphere, which the best science indicates is very likely the major cause of global warming trends, as a very important metric. This will be addressed in more detail later in the course, but suffice to say the trend is pointing in the wrong direction, and possibly already at dangerous levels. There are many other indicators that are at a varying level of (non-)concern, some of which will be addressed later. Unfortunately, Engelman is mostly right when he writes that "the basic trends themselves remain clearly, measurably unsustainable."

Figure 1.12: Global average temperature and atmospheric carbon dioxide concentrations since 1880. Atmospheric carbon dioxide concentration is one of the most prominent sustainability metrics we have available to us, with most climate scientists agreeing that we are at or approaching dangerous levels. (This chart will be addressed in more detail in a future lesson.)

Click for a text description of the Global Temperature and Carbon Dioxide graph.

The x-axis represents the years from 1880 to 2000. The left y-axis shows global temperature in degrees Fahrenheit (°F), ranging from 56.5°F to 58.5°F. The right y-axis displays CO₂ concentration in parts per million (ppm), ranging from 260 ppm to 400 ppm.

The graph includes two main data sets:

• A blue histogram representing global temperature anomalies, fluctuating around a baseline of approximately 57.5°F, with noticeable dips and rises, particularly more pronounced dips before 1950 and some increases toward 2000.
• A red histogram overlaid with a black trend line representing CO₂ concentration, showing a steady increase from around 280 ppm in 1880 to over 380 ppm by 2000, with a sharp rise starting around 1950.

An arrow labeled "CO₂ Concentration" points to the red histogram, indicating its association with the CO₂ data. The graph suggests a correlation between rising CO₂ levels and increasing global temperatures over the 120-year period.

Credit: NOAA

5. Economics and Systems Thinking

Finally, Engelman addresses the fraught relationship between economic prosperity and sustainability, and the difficulty in satisfying both present and future needs. Ridding the world of abject poverty is at the forefront of sustainability goals, and is addressed in future lessons. But unfortunately economic growth and sustainability - particularly environmental sustainability - are often at odds. For example, increasing access to fossil fuels generally helps facilitate improving economic conditions, but causes unsustainable emissions. Even current and future sustainability can be at odds, e.g., when Engelman notes that: "Safe water may be reaching more people, but potentially at the expense of maintaining stable supplies of renewable freshwater in rivers or underground aquifers for future generations."

This all indicates the importance of systems thinking. There is a lot of literature about systems thinking, and it does not have a single definition. (If only the world of sustainability were so simple!) It can be thought of as analyzing the world around us as a collection of interrelated systems, and considering phenomena as related to other phenomena. In other words, systems thinking requires consideration of connections. There is an old saying that "the biggest cause of problems is solutions," which is important to keep in mind when analyzing sustainability issues. Examples of unintended (sustainability) consequences abound. For example:

• The so-called Green Revolution instituted in Pakistan and India in the 1960's and 1970's probably saved millions, or even hundreds of millions of lives, but has also contributed to soil loss, debt, and farmer suicides due to the unsustainable farming practices it uses.
• Forest fire prevention and suppression in the U.S. has led to more severe forest fires (an example of a Penn State led study can be found on Penn State News, December 17, 2019).) As it turns out, low-grade forest fires naturally reduce understory fuel sources (shrubs, fallen branches, etc.), which help prevent more intense fires from occurring.
• Many invasive species were purposefully introduced by humans, only to inflict lasting damage on native plant and/or animal populations. Kudzu is a vining plant that has proved to be a major menace wherever it grows in the U.S., yet was promoted first as an ornamental plant, then a tool for preventing soil erosion. Cane toads were released into Australia in the 1930's in an effort to control the beetle population. Not only have they not controlled beetles, but they are now major nuisances to humans and native species and habitats.

From a sustainability perspective, systems thinking means that you should at least always a) consider the short- and long-term impacts of actions, both in space and time, and b) consider the possible causes of issues. It is unwise to address a problem or situation without thinking about the possible causes and consequences. More on this below.

Figure 1.13: A kudzu-covered forest in Mississippi, U.S.A. Kudzu is notoriously difficult to get rid of and has spread across much of the Southern and Eastern U.S., yet its deliberate planting was encouraged by the government as recently as the 1940s.

Credit: Gsmith, C.C. BY-SA 3.0

The Three E's of Sustainability

The EPA offers a definition of sustainability that encompasses a lot of the concepts described above: "To pursue sustainability is to create and maintain the conditions under which humans and nature can exist in productive harmony to support present and future generations" (source: US EPA). Note that this definition changed slightly in early 2017. It used to be: "Sustainability creates and maintains the conditions under which humans and nature can exist in productive harmony, that permit fulfilling the social, economic and other requirements of present and future generations." Read into that change what you will. This is a more thorough definition than the Brundtland Commission's and provides a more actionable list of goals. (Though it should be noted that there is still a lot of room for debate on how to achieve them or what they really mean.) It also brings to mind what is commonly referred to as the "three E's of sustainability."

Sustainability and sustainable development are often thought of as having three core components: environment, economy, and equity. These are commonly referred to as the "3 E's" of sustainability. The 3 E's are a useful way to provide an analytical framework for sustainability. This 3E framework is useful because it provides questions that can be asked when investigating whether or not something is sustainable. While even these terms can be defined in various ways, we will use the following definitions from the reading when analyzing the sustainability implications of something:

• Is it "environmentally sustainable, or viable over the very long term"? (environment)
• Is it "economically sustainable, maintaining [and/or improving] living standards over the long term"? (economy)
• Is it "socially sustainable [and just], now and in the future"? I would add "Are the benefits and burdens shared be everyone equally?" (social equity)

As Dillard and Dujan note, if a business is attempting to address these criteria, it is often called the triple bottom line. If it meets all three criteria, and will likely continue to do so into the foreseeable future, then that is a pretty strong case for sustainability.

Figure 1.14: Sustainability can be visualized as the intersection of all 3 E's.

Credit: D. Kasper

The details of how to maintain environmental sustainability are not without controversy, but at some point, we will have to maintain a steady-state of natural resources if we are to survive (this will be addressed later). As Engelman and others say, this may come at the expense of quality of life for some/many people now. No one said it will be easy.

But through my own personal experience and the experience of others, it is clear that social equity is the most confusing of these concepts. Dillard, Dujon, and King do a good job of outlining what it means. Contrary to what some believe, equity does not mean equal distribution of resources. There will always be inequality, whether we want it or not. What it does refer to is the fairness of opportunity and access to resources like education, health care, a clean environment, political participation, social standing, food, shelter, and others. In a socially equitable society, everyone has reasonable access to things that provide a good quality of life. Social equity is about equality of opportunity. Whether or not they take advantage of this opportunity is another story. There is an important difference between being uneducated because of laziness and because of a lack of access to good schools. Making this happen is easier said than done, but the distinction is important to make.

One reason that addressing equity can be controversial is illustrated in the image below. What do you think it is?

Figure 1.15: Equality requires everyone to have the same resources, while equity often requires providing additional resources to those in need of them.

Credit: Community Eye Health, CC BY-NC 2.0

As indicated in the caption, equity often requires providing more resources to those that are at some disadvantage. Why they are disadvantaged, who decides they deserve help, the amount of help they are given, and more aspects can be controversial. Which is understandable, given that individual and group circumstances are rarely black and white and oftentimes public resources such as tax dollars are involved. Generally, those that advocate for equity err on the side of "too much" equity rather than "too little."

Economy can also be a point of confusion. It is very important to keep in mind that "economy" from a 3E perspective does not refer to just having and/or making money. It refers both to engaging in actions that are economically sustainable (if businesses do not make enough money to continue, they will not be in business for long) and having enough money to provide and maintain a reasonably high quality of life over the long term. Yes, money is often an important - if not the most important - factor in achieving a high quality of life, particularly at lower income levels. But please keep in mind as we move forward that, from a sustainability perspective, the true "economic" goal is quality of life, not high income. Money often does contribute to a high(er) quality of life, but not always, as we will see later. Money is a means to an end. For sustainability purposes, that economic "end" is providing adequate living standards for people now and in the future. (After all, if you are incredibly happy, healthy, safe, and have everything you need, does it matter if you do not have a lot of money? More on this later.)

It may be helpful to summarize some of the key points from the previous page (though more will be addressed in this week's homework questions):

• Sustainability/sustainable development has no single definition, but the most commonly cited one is by the Brundtland Commission ("meeting the needs of the current generation without compromising the ability of future generations to meet their needs").
• We must consider quality of life when addressing sustainability and may need to make some sacrifices to achieve abroad-based quality of life.
• We must utilize systems thinking when addressing sustainability problems, recognizing that actions taken will likely have far-reaching consequences.
• If we are to achieve sustainability, we must at least consider the environmental, economic, and social equity impacts on current and future generations.
• In order to know how well we are achieving sustainability, we must find a way to measure it or at least find ways to know if things are (not) going well.

Sustainability is some heavy, complex stuff! Most would argue that the future of civilization depends on how we address sustainability, starting yesterday <raising hand>. As Asher Miller phrases it in his introduction to The Post Carbon Reader, "The success or failure of the human experiment may well be judged by how we manage the next ten to twenty years" (p. xv). (For better or worse, and unfortunately I'd say "worse," that was written about 10 years ago.) Sustainability is a very important topic, but it is an even more complex and broad topic than energy. I don't expect you to be an expert (yet), but I hope that this course helps you think critically about sustainability-related and other claims.

Energy, Sustainability, and Society

I have a challenge for you: think of something that you did in the past week that did not involve energy.

Okay, so that's not really a fair challenge. Everything we do, even thinking about things that we might do, require energy. Here's a more reasonable challenge: think of something that you did in the past week that did not involve the use of non-renewable energy.

Any food you eat almost certainly required non-renewable energy. There are obvious connections like farm machinery, artificial fertilizers, and herbicides, transporting food, refrigerating food, cooking food, and packaging food. But even if you grow your own, you likely used a tool or fencing that was manufactured using non-renewables, seeds that were processed and shipped with fossil fuel-using machines, packaging that was made using non-renewable energy, or maybe even plastic row markers made with petroleum-based plastics. Almost all transportation uses non-renewables, most businesses run on non-renewable energy sources (either directly or indirectly through electricity generation), almost all of the products you buy contain materials either made of or that are processed with fossil fuels. The electronic device you are looking at right now is partially made of and manufactured using fossil fuels. In short, modern society is very dependent upon access to non-renewable energy, particularly fossil fuels. As Asher Miller notes in The Post Carbon Reader:

Look around and you'll see that the very fabric of our lives - where we live, what we eat, how we move, what we buy, what we do, and what we value - was woven with cheap, abundant energy. (p. xiv)

Watch the video below for an interesting 5-minute journey through the last 300 years of fossil fuels in society. It is from over a decade ago, but the issues brought up are more relevant than ever. He also brings up some issues that we will go over in more depth later in the course.

The Dominance of Non-Renewable Energy

The charts below provide rather dramatic evidence of how important non-renewable energy is to the U.S. All charts are from the EIA's Annual Energy Outlook (AEO) series, which are published on a yearly basis. I have provided a series of charts to provide some indication of how difficult it is to predict future trends. But, these serve as official (and generally pretty accurate) guides to future energy use.

The first chart is from the 2015 version of the AEO. Though a bit outdated, I put it here because the chart style makes it very easy to see the dominance of non-renewable energy sources. The second chart is from a more recent report (2019) that has total energy consumption, and the third from the most recent (2022) report. The second and third charts are obviously more recent, but is not quite as easy to interpret. Another nice feature of these charts is that they include both historical use and projected future use.

Any way you slice it, the charts make clear that non-renewable energy - particularly fossil fuels - have played and will continue to play a dominant role in society. At this point, our society simply cannot function at its current capacity without them.

Another aspect worth noting is that aside from recessions (e.g., early 1980's and 2007-8), energy use continues to increase over time. Despite consistent increases in energy efficiency, the U.S. can't seem to level off, never mind reduce overall consumption. This is also something that will have to be addressed if we are going to have a sustainable energy future.

Finally, Figure 1.17 shows which energy sources are most responsible for carbon dioxide emissions in the U.S. Oil is the current leader, but as more and more natural gas is used (particularly to generate electricity), it will likely come close to catching up to oil-based emissions by 2050, according to the EIA.

Figure 1.16: As you can see, over 90% of the total energy supply in the U.S. was from non-renewable energy in 2013, and about 83% of the total is fossil fuels. The EIA clearly does not think this will change much by 2040, with the exception of a little more total renewable and natural gas use.

Click here for a text description of Figure 1.16.

The image is a stacked area chart titled “Figure 18. Primary Energy Consumption by Fuel in the Reference Case, 1980–2040.” It displays the historical and projected energy consumption in the United States, measured in quadrillion British thermal units (Btu), from 1980 to 2040. The x-axis is divided into two segments: “History” (1980–2013) and “Projections” (2013–2040), while the y-axis ranges from 0 to 120 quadrillion Btu. The chart uses different colors to represent various fuel types: petroleum and other liquids (red), coal (brown), nuclear (orange), liquid biofuels (yellow), renewables (green), and natural gas (blue).

In 1990, petroleum and other liquids accounted for 40% of energy consumption, followed by coal and natural gas at 23% each, and nuclear and renewables at 7% each. By 2013, natural gas had increased to 27%, while petroleum and other liquids declined slightly to 36%. The chart projects a continued shift in the energy mix, with natural gas and renewables increasing in share, while coal declines. Nuclear remains relatively stable, and liquid biofuels show modest growth. The visualization highlights a long-term trend toward cleaner energy sources, though fossil fuels still dominate the overall energy landscape throughout the projection period.

Credit: US EIA, Annual Energy Outlook 2015

Can We Keep Doing This?

Non-renewable energy is extremely useful - it has played an essential role in human society developing to the point that it has. It is energy dense, generally easy to transport and control, and is used for a variety of purposes. Non-renewable energy will continue to play a starring role, for at least the short term future. I enjoy the freedom of the open road in my car. I like to have a house in which I have some control over the temperature and humidity. I like to buy new things from time to time. I enjoy the occasional air travel. I eat food that was shipped from countries on the other side of the world. If we are all to enjoy such things (and more) in the way society and our economy is currently structured, we need access at least to fossil fuels. But given our understanding of the nature of sustainability and non-renewable energy, this cannot go on forever. In fact, it will probably need to change dramatically within the next 10-15 years.

If nothing else, since non-renewable energy is finite, we will reach limits at some point in the future - exactly when is open to debate. But even before that eventuality, it is becoming apparent that the results of unsustainable energy (and resource) use is making it difficult for current generations to meet their needs, never mind future generations. The topics in the next lessons illustrate some of the reasons that scientists and others are worried about the sustainability of our society, some of which are directly related to energy, others not.

We are going to run into limits at some point. The tricky part is figuring out how to transition away from fossil fuels in a (relatively) smooth manner with the least amount of chaos. Throughout this semester, we will consider some of the potential solutions - primary among them is internalizing externalities so that we pay the true cost of fossil fuels. More on that in the next lesson! (I bet you can't wait!)

All right, that does it for the content for this week. Before you relax, make sure you complete the assignments listed at the beginning of this lesson.

This week, we went over some of the core considerations for energy and sustainability.

You should be able to do the following. The Lesson 1 quiz will help you solidify these skills:

• define energy, energy efficiency, and the First Law of Thermodynamics;
• identify and describe types of energy and energy conversions:
• identify and define fossil fuels, non-renewable energy sources, and renewable energy sources, and their origins and characteristics;
• analyze the energy data provided in charts and graphs;
• identify reliable sources of energy data;
• evaluate the implications of sustainability definitions; and
• define the "3 E's" of sustainability and use the 3E framework to evaluate the sustainability of given actions.

The Language of Energy and Sustainability

At the end of each lesson, I will provide a list of all of the key terms from the lesson. These terms are easy to find because most of them are in bold throughout the lesson, or appear in headings. This is designed to help you review the content, both before you take the quiz, and later. Many of these terms will be used in other parts of the course, in future courses in the Energy and Sustainability Policy curriculum, and in the sustainability and energy literature. They are mostly listed in the order they appear in the text.

• Energy, work
• Kinetic energy, potential energy, electromagnetic energy, sound energy, radiant energy, mechanical energy, electrical energy, chemical energy, gravitational energy, nuclear energy, thermal energy, First Law of Thermodynamics
• Coal, oil, natural gas, nuclear, fossil fuels, hydrocarbons
• British Thermal Unit, Btu, Joule, kilowatt hour (kWh), 100 cubic feet (ccf), quads, national labs, energy sources, end-use sectors, Sankey diagram
• Energy efficiency, Second Law of Thermodynamics, the "fifth fuel"
• Renewable energy, non-renewable energy, solar photovoltaics, wind turbines, hydropower, biomass, biofuels, primary energy, carbon free, carbon neutral
• Energy Information Administration (EIA), International Energy Agency (IEA)
• Sustainability, sustainable development, Brundtland Commission, ecocentric, anthropocentric, 3 E's, environment, intergenerational equity, equity, economy, triple bottom line, sustainability indicators/metrics

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