Part of the purpose of the course is to help you to understand why biofuels are needed and how to make them, at the current state-of-the-art.

Why biofuels? To look at the situation a little more broadly, the question then becomes: why alternative fuels?

As climate change becomes an issue of ever-stronger concern in the world, stronger efforts are being devoted to tackling this issue. The International Energy Agency (IEA) has recently proposed the 2°C scenario (2DS) as a way to handle the climate change issue. The 2DS has become a largely used quote by many policymakers and scientists. The 2DS scenario requires that carbon dioxide (CO₂) emissions in 2060 should be reduced by 70% in comparison to the 2014 level. The transport sector plays an important role to achieve this goal, considering that the transportation sector is responsible for about 23% of total CO₂ emissions. Although electricity has been considered a promising option for reducing CO₂ emissions in transportation (Yabe, Shinoda, Seki, Tanaka, & Akisawa, 2012), transport biofuel is estimated to be the key alternative energy in the transport sector (Ahlgren, Börjesson Hagberg, & Grahn, 2017). The share of biofuels in total transportation-fuel consumption by 2060 is predicted to be 31%, followed by electricity at 27% based on the mobility model results of IEA for the 2DS. Biofuel production must be increased by a factor of 10 to achieve this goal (Oh, Hwang, Kim, Kim, & Lee, 2018). In addition to the need for climate change adaptation, the increasing concerns over energy security is another main driver for the policy-makers belonging to the Organisation for Economic Co-operation and Development (OECD) to promote the production of renewable energy (Ho, Ngo, & Guo, 2014). Last but not least, world energy demand will continue increasing. The world energy demand was 5.5 x 10²⁰ J in 2010. The studies predict an increase of a factor of 1.6 to reach a value of 8.6 x 10²⁰J in 2040. The bioenergy delivery potential of the world's total land area excluding cropland, infrastructure, wilderness, and denser forests is estimated at 190 x 10¹⁸ J yr^-1, 35% of the current global energy demand (Guo, Song, & Buhain, 2015).

Energy Demand, Climate Change, Energy Security: Three main reasons to promote sustainable biofuel production and usage.

Credit: Dr. Hilal Ezgi Toraman © Penn State, is licensed under CC BY-NC-SA 4.0.

In short, there are three main reasons to develop biofuels:

1. to meet the needs of increasing energy demand;
2. to reduce greenhouse gas (GHG) emissions; and
3. to improve energy security by reducing dependence on foreign fuel sources because it can be problematic, depending on US domestic fuel production.

We will explore each of these reasons in more depth in the following sections.

The energy needs of most advanced economies in the Western world are increasing at a modest level. However, in some developing economies, where the economy is booming, energy demands are increasing dramatically, e.g., in India and several African countries. The figure below shows the latest gross domestic product (GDP) growth rate of the countries of the world in 2025. While advanced economies had a 1.7% annual percent change in real GDP growth, emerging and developing Asia had a 4.5% annual percent change in real GDP growth, with India having a 6.2% annual percent change in real GDP growth. Emerging and developing economies accounted for over 80% of global energy demand growth. According to the IEA's Global Energy Review 2025, global electricity consumption increased by approximately 1,100 terawatt-hours (TWh) in 2024, more than double the annual average increase over the past decade. Currently, global energy consumption is growing at around 1-2% per year.  This rate is faster than the average rate over the past decade. If many third-world countries were to dramatically increase their standard of living, there are estimates that worldwide energy consumption would double. But where would that energy come from, particularly since there aren't huge stockpiles of crude oil sitting around? Petroleum cannot supply it all, and neither can natural gas or coal.

World Map of Real GDP Growth

Click here for a text description of the World Map of Real GDP Growth.

The image is a world map visualization titled "IMF DataMapper", which displays Real GDP growth (Annual percent change) for the year 2024 across various countries. It uses a color-coded legend to represent different ranges of GDP growth rates:

• Dark green: Countries with 6% or more GDP growth.
• Medium green: Countries with 3% to 6% GDP growth.
• Light green: Countries with 0% to 3% GDP growth.
• Yellow: Countries with 0% to -3% GDP growth (i.e., slight economic contraction).
• Orange: Countries with less than -3% GDP growth (i.e., significant economic contraction).
• Grey: Countries with no available data.

6% or more (Dark Green)

These countries are projected to have robust growth:

• Several countries in Sub-Saharan Africa

• Parts of Southeast Asia and Central Asia

3% – 6% (Medium Green)

These countries are projected to have moderate to high growth:

• Most of North America and South America
• Large parts of Africa
• Eastern Europe
• Most of Asia, including India

0% – 3% (Light Green)

These countries are expected to see modest economic growth:

• United States
• Canada
• Western Europe
• Japan
• Australia
• Some parts of Latin America
• Some parts of the Middle East

0% – (-3%) (Yellow)

These countries are projected to experience a slight economic contraction:

• Mexico
• Venezuela

Less than -3% (Orange)

These countries are expected to face significant economic decline:

• Haiti

No Data (Grey)

No economic data available for:

• Greenland

Credit: IMF DataMapper, World Economic Outlook

The US is highly dependent on crude oil to produce fuels for transportation. The figure below shows how the transportation sector is almost all oil-based, and the other sources barely make a dent in the hold petroleum has. Up until the last few years, the US has been highly dependent on foreign sources of oil. In 2023, petroleum accounted for approximately 89% of the primary energy consumption in the transportation sector, but it contributed less than 1% to the primary energy consumption in the electric power sector. The chart below illustrates the various types and quantities of primary energy sources used in the United States, the primary energy consumption by the electric power sector and end-use sectors, and the sales of electricity from the electric power sector to these end-use sectors. Growth across different parts of the global energy system varied widely in 2024, shaped by both short-term influences and longer-term structural shifts. Worldwide energy demand rose by 2.2%—well above the 1.3% annual average recorded from 2013 to 2023. Around 0.3 percentage points of this increase can be attributed to the effects of extreme weather. Even so, energy use expanded at a slower pace than the global economy, which grew by 3.2% in 2024, roughly in line with its long-term trend. Electricity demand grew faster than both overall energy use and GDP in 2024, rising by 4.3%. In absolute terms, this was the largest increase ever observed outside of post-recession rebounds. The surge was driven by structural factors, including wider use of electricity-intensive appliances such as air conditioning, shifts toward electricity-heavy manufacturing, growing needs from digitalisation, data centres, and AI, and the continued electrification of end uses. Altogether, the power sector accounted for around 60% of the global increase in energy demand.

On the supply side, renewables contributed the largest share of growth (38%), followed by natural gas (28%), coal (15%), oil (11%), and nuclear (8%). However, energy intensity improved by only 1%, extending the recent trend of slower efficiency gains. Energy-related CO₂ emissions rose by 0.8%—a deceleration compared with the 1.2% increase in 2023. (IEA, 2025).”

The US was the world's largest petroleum consumer (EIA, 2012), but was third in crude oil production. Over half of the material that was imported into the US comes from the Western hemisphere (North, South, and Central America, and the Caribbean), but we also imported 29% from Persian Gulf countries (Bahrain, Iraq, Kuwait, Saudi Arabia, and the United Arab Emirates).

The top 5 sources of net crude oil and petroleum imports included 1) Canada, 28%, 2) Saudi Arabia, 13%, 3) Mexico, 10%, 4) Venezuela, 9%, and 5) Russia, 5%. According to CNN Money, the US was behind Russia and Saudi Arabia in oil production for the first three months of 2016. See the World's Top Oil Producers for additional information. However, this situation recently changed, and the US became the world's largest oil producer in 2018 for the first time since 1973 and held the lead position through 2022. U.S. oil refineries obtain crude oil produced in the United States and other countries. Based on EIA, crude oil is extracted in 32 U.S. states as well as in coastal waters. In 2022, five states together made up roughly 72% of the total crude oil production in the United States. In 2022, 98 countries collectively produced around 80.75 million barrels of crude oil, with five of these nations contributing approximately 52% of the global total. The top five crude oil-producing countries and their respective shares of world crude oil production in 2022 were: The United States 14.7%, Saudi Arabia 13.2%, Russia 12.7%, Canada 5.6%, and Iraq, 5.5%. See the following link for further information see America is now the world's largest oil producer.

So, while oil is fairly available currently, there is extensive potentially explosive turmoil in many petroleum-producing regions of the world, and, in several places, the US's relationship with some oil-producing countries is strained. China and India are now aggressive and voracious players in world petroleum markets because of high economic growth (as pointed out in the previous section). Saudi Arabia's production is likely "maxed out," and domestic oil production peaked in 1970. While the US dependence on imported oil has declined after peaking in 2005, it is clear that if any one of the large producers decides to withhold oil, it could cause a shortage of fuel in the US and would cause the prices to skyrocket from an already high price (depending on the type of crude oil, the price of oil is currently $100-$106/bbl) (see U.S. Energy Information Administration). The figure below is a graphic showing the price level of oil from 1950 to the present. As you can see, there has been significant volatility in the price of oil in the last ~50 years. One of the first spikes came in 1974 when the Organization of the Petroleum Exporting Countries (OPEC) became more organized and withheld selling oil to the US. It was a true crisis at that point, with gasoline shortages causing long lines and fights at gas stations, with people filling up only on certain days depending on their license plates. It had a high spike in 1980, but a significant low in 1986. When the price of oil hit a significant low in 1998, the government took steps to lower the tax burden on oil companies. But when the prices went back up, the law remained in place, and currently, oil companies do not have to pay taxes on produced oil. When the reduced tax burden went into place in the late 90s, it made sense, but oil companies have continued to convince Congress with lobbyists that it should stay that way. What do you think?

As seen in the figure below, there were major fluctuations in gasoline prices in the last few years. As we will discuss in a later lesson, several aspects contribute to the price of gasoline, including but not limited to the recent COVID-19 Pandemic. This is a graphic that shows the price volatility for gasoline from 1990 - 2024 (the most recent data available), and the other figure below shows a breakdown of what goes into the price of gasoline.

In recent years, petroleum became less available and more expensive, and replacement-alternative fuels emerged because the economics were beginning to become more favorable. However, due to lower demand and high petroleum supply, prices drastically dropped, which may affect the development of alternative fuels. There is one factor that will most likely reverse this trend, and that is that energy demands will continue to increase worldwide. For future transportation fuel needs, most likely a liquid fuel will be necessary, and no one source will be able to replace petroleum. In the International Energy Outlook 2021 (IEO2021) Reference case, it is anticipated that, without major policy or technological advancements, global energy consumption will rise by nearly 50% over the next 30 years. While petroleum and other liquid fuels are expected to remain the world's primary energy source by 2050, renewable energy sources like solar and wind are projected to expand to almost the same level. It is important to note that Petroleum and other liquids include biofuels.

There is a scientific consensus that greenhouse gas (GHG) production is increasing, which has led to climate change and several other environmental concerns. Despite efforts to make us believe otherwise, much of the severe weather occurring worldwide is indeed due to climate change. There is a significant amount of evidence to substantiate the existence of climate change and the overall warming of the earth. Climate change is due to the Greenhouse Effect; it is a natural effect, caused by CO₂ and water vapor naturally present in the atmosphere. The focus of debate (scientific and political) has been on whether there is also an anthropogenic greenhouse effect, causing further climate change. Carbon dioxide (CO₂) is not the only greenhouse gas (methane, CH₄ is another potent GHG; this will be discussed further in upcoming sections), but most of the debate focuses on it. It is thought that the dramatic increase in CO₂ in the atmosphere is due to the burning of fossil fuels.

The world is highly dependent on fossil fuels; the US is also highly dependent on fossil fuels. As we saw in the charts in Lesson 1.3, global energy consumption will continue to increase over the next 30 years. Fossil-based sources such as coal, natural gas, and petroleum are expected to be the dominant energy source in 2050.

There is a mountain of evidence indicating that the planet is warming. The figure below shows global average surface temperature levels plotted from 1880-2020. The change has been most dramatic in the last 30 years. Yearly global temperatures from 1880 to 2023 relative to the 20th-century average show that Earth's surface temperature has increased by 0.14 degrees Fahrenheit per decade since 1880. The pace of warming has more than doubled since 1981.

The 2023 Global Climate Report from NOAA's National Centers for Environmental Information reveals that every month in 2023 was among the seven warmest on record for that particular month. Additionally, each month from June to December marked the hottest ever recorded for those months. In July, August, and September, global temperatures exceeded the long-term average by more than 1.0°C (1.8°F)—the first time any month in NOAA's records has surpassed this threshold.

The impacts of climate change on our planet can be observed from pole to pole. NOAA tracks global climate data, and here are some notable changes they've recorded, with more details available on the Global Climate Dashboard.

• Global temperatures have increased by about 1.8°F (1°C) from 1901 to 2020.
• Sea level rise has accelerated from 1.7 mm/year during most of the 20th century to 3.2 mm/year since 1993.
• Glaciers are retreating: the average thickness of 30 well-studied glaciers has reduced by over 60 feet since 1980.
• The summer sea ice coverage in the Arctic has diminished by approximately 40% since 1979.
• Atmospheric carbon dioxide levels have risen by 25% since 1958 and by about 40% since the Industrial Revolution.
• Snow is melting earlier than long-term averages indicate.

In the Arctic and Antarctic regions, the ice pack and glaciers are melting, and at an even faster rate than originally anticipated. Scientists have found that increasing atmospheric temperatures are not the only cause of this; the melting is causing water currents to shift and move warmer water around the poles, so melting is happening underneath the ice pack. The figure below shows that the total area of the Arctic Ocean with at least 15% ice coverage each September from 1979 to 2023 shows that, since 1980, the extent of ice surviving the summer has decreased by 13.1% per decade. The figure related to Sea Ice Concentration demonstrates that the sea ice concentration on September 19, 2023, compared to the 1981-2010 average extent for that date (indicated by the gold line), marked the sixth smallest summer minimum ever recorded. The sea levels have also risen by 8-9 inches since 1880, with the rate of increase accelerating during the satellite era.

Another problem could stem from the increased production of natural gas. Natural gas consists primarily of methane. Sources include petroleum and natural gas production systems, landfills, coal mining, animal manure, and fermentation of natural systems. Methane has 25 times the global warming potential of CO₂. The figure below shows the total GHG percentages from various economic sectors. The transportation sector is the largest contributor of greenhouse gas emissions. Greenhouse gas emissions from transportation mainly result from burning fossil fuels in cars, trucks, ships, trains, and planes. Over 94% of transportation fuel is petroleum-based, including primarily gasoline and diesel, which leads to direct emissions. The transportation sector is the largest source of direct greenhouse gas emissions and ranks second when considering indirect emissions from electricity use across all sectors. Although transportation is an end-use sector for electricity, it currently accounts for a relatively small portion of total electricity consumption. Indirect emissions from electricity make up less than 1% of direct emissions in this sector. The next figure shows the emissions of various GHG emissions from 1990-2021. The EPA points out that overall emissions of CH₄ have been reduced by 11% from 1990-2021. However, an article published in Nature (Yvon-Durocher, March 2014) suggests that there may be an unexpected consequence of warming temperatures; global warming can increase the amount of methane evolved from natural ecosystems. So, it remains to be seen what impacts can happen that have not been included in climate change models.

There are several possible responses to abate CO₂ and CH₄: 1) do nothing; 2) reduce CO₂ and CH₄ prudently; 3) drastically reduce energy use; and 4) move to a carbon-free society. The easiest, but quite possibly the most damaging in the long run, is to do nothing - currently, some nations are pushing to at least increase conservation. The use of hybrids has decreased our use of gasoline, as the increase in Corporate Average Fuel Economy (CAFE) standards has had an impact. However, prudent measures to reduce GHG will most likely not be enough to make a huge impact. Therefore, the use of biofuels could have great potential for reducing the impact of CO₂ and CH₄, if done well. However, some actions in South America have shown that if switching to biofuel growth is not handled well, a greater problem can be created. Some rainforest areas were removed from South America to clear land for producing biofuels, but the rainforests that were removed were burned, putting an excessive amount of CO₂ in the atmosphere. Rainforests have grown over long periods, so there was a lot of carbon stored in them - they were also places where exotic animals, plants, and insects lived, so the burning endangered the wildlife species in the rainforests. One thing to always keep in mind: whenever an action is taken in our atmosphere, there is the possibility of a negative consequence that one cannot foresee.

Summary

This lesson was about how using biofuels can benefit society. We looked at increasing energy demands around the world, how economically dependent we are on foreign sources of fuel, and how we don't have much control over what the prices of our fuels will be. We also explored how the growth in GHG emissions is a vital environmental concern and discussed how, without the use of biofuels, we cannot achieve significant reductions in GHG.

Lesson Objectives Review

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

• explain why biofuels are a necessary part of our energy portfolio.

References

"U.S. Energy Information Administration - EIA - Independent Statistics and Analysis. EIA's Energy in Brief: How Dependent Are We on Foreign Oil?

Greenhouse Gas Emissions: Greenhouse Gases Overview. EPA. Environmental Protection Agency.

Yvon-Durocher, G., Allen, A.P., Bastviken, D., Conrad, R., Gudasz, C., St-Pierre, A., Thanh-Duc, N., del Giorgio, P.A., "Methane fluxes show consistent temperature dependence across microbial to ecosystem scales," Nature, 507, 488-491.