Regan Brown
Ethanol is a renewable fuel made from plant materials known as biomass, such as corn or sugarcane. It is commonly blended with gasoline (petrol) to create a biofuel additive. The amount of ethanol in gasoline varies, but in the United States, most finished motor gasoline sold contains about 10% ethanol by volume, known as E10. Other blends include E15 (15% ethanol) and E85 (up to 85% ethanol). The use of ethanol in gasoline has benefits, such as reducing air pollution and supporting U.S. agriculture, but there are also concerns about its sustainability, environmental impact, and effect on fuel economy.
| Characteristics | Values |
|---|---|
| Percentage of ethanol in gasoline | About 10% by volume (E10) |
| Percentage of ethanol in gasoline with higher ethanol content | 15% (E15) or up to 85% (E85) |
| Ethanol production in the US in 2019 | 15.8 billion US liquid gallons |
| Ethanol consumption in the US in 2022 | 14 billion gallons |
| Ethanol as a percentage of global gasoline type fuel use in 2008 | 5.4% |
| Ethanol fuel production worldwide in 2011 | 8.46 billion imperial gallons |
| Ethanol's energy content compared to gasoline | About 33% less |
| Ethanol's impact on vehicle fuel economy | Decrease of about 3% when using E10 |
| Ethanol's impact on engine knocking | Helps prevent it |
| Ethanol's impact on fuel prices | Exerts downward pressure on petroleum prices |
| Ethanol's impact on water supply | Much safer than MTBE |
| Ethanol's sustainability and environmental impact | Debated due to large amount of arable land required for crops and ethanol production's impact on grain supply |
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What You'll Learn
Ethanol fuel content in the US
The United States is the world's largest producer of ethanol fuel. In 2019, the US produced 15.8 billion US liquid gallons of ethanol fuel, up from 13.9 billion gallons in 2011 and 1.62 billion gallons in 2000.
In the US, ethanol fuel is primarily used as an additive in gasoline in the form of low-level blends up to 10%, and, increasingly, as E85 fuel for flex-fuel vehicles. E10 is a blend of 10% ethanol and 90% gasoline (by volume) and is the primary source of US ethanol consumption. E15 is gasoline with 15% ethanol content, and E85 may contain up to 85% ethanol. Most motor gasoline with more than 10% ethanol content is sold in the Midwest, where most ethanol production capacity and infrastructure are located.
The use of ethanol as a gasoline additive has increased since the 1970s due to various factors. Firstly, the oil embargo against the US by Middle Eastern producers in 1973 and rising oil prices in the late 1970s and early 1980s spurred interest in ethanol as a way to reduce US oil imports. Secondly, the Clean Air Act amendments of 1990 mandated the use of oxygenated fuels in areas with high levels of carbon monoxide, and ethanol was used to meet these requirements. Thirdly, the phase-out of the gasoline oxygenate methyl tertiary butyl ether (MTBE) in the early 2000s due to groundwater contamination concerns created a new market for ethanol as a substitute.
The US government has also provided incentives and regulations that have boosted ethanol production and consumption. The Energy Tax Act of 1978 established an excise tax exemption for gasoline blended with alcohol fuels, and the American Jobs Creation Act of 2004 offered a tax credit for ethanol blending. The Renewable Fuel Standard (RFS), introduced in 2005 and expanded in 2007, requires a minimum volume of renewable fuels, primarily ethanol, to be blended into transportation fuel.
However, the use of ethanol as a fuel has also faced criticism. Environmentalists argue that the environmental impacts of corn production, soil erosion, water pollution, and the clearing of land for corn cultivation outweigh the benefits of ethanol as a renewable fuel. Additionally, the mature state of the ethanol industry, market distortions, and the distribution of subsidy benefits have been cited as concerns.
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Ethanol blends and their labels
Ethanol is available in several blends for use in conventional and flexible fuel vehicles. The blends are labelled according to their maximum ethanol content. For example, E10 contains 10% ethanol and 90% gasoline. Most finished motor gasoline sold in the United States is E10. E15 contains up to 15% ethanol, and E85 contains up to 85% ethanol.
E10 is approved by the U.S. Environmental Protection Agency (EPA) for use in any conventional, gasoline-powered vehicle. All models of vehicles sold in the United States can use E10. E10 is the primary source of ethanol consumption in the United States. The use of E10 was spurred by the Clean Air Act Amendments of 1990, which mandated the sale of oxygenated fuels in areas with unhealthy levels of carbon monoxide. E10 is sold in every state.
E15 is a low-level blend composed of 10.5% to 15% ethanol and gasoline. It is approved for use in model year 2001 and newer light-duty conventional vehicles. Stations must adhere to several EPA requirements and regulations when selling E15, including the implementation of a misfuelling mitigation plan to reduce the risk of vehicles older than model year 2001 refuelling with E15. The EPA also approved a new E15 label for gasoline pumps so consumers know what fuel they are buying.
E85 is an ethanol-gasoline blend containing 51% to 83% ethanol, depending on geography and season. It is defined as an alternative fuel. E85 can be used in flexible fuel vehicles (FFVs), which have an internal combustion engine and are designed to run on E85, gasoline, or any blend of gasoline and ethanol up to 83%. Flex-fuel vehicles can run on any mixture of ethanol and gasoline up to E85. They may be identified by a badge or plaque on the body of the vehicle with E85, Flex Fuel, or FFV.
In some regions, the ethanol content of E85 is reduced during the winter to avoid cold-starting problems at low temperatures. In the US, this seasonal reduction to an E85 winter blend is mandated in cold regions, where temperatures fall below 32 °F (0 °C) during the winter. This winter blend is typically E70, containing 70% ethanol and 30% gasoline. In Sweden, the winter blend is typically E75, containing 75% ethanol.
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Ethanol's impact on vehicle fuel economy
Ethanol is a renewable fuel made from various plant materials, including corn grain, sugar cane, and cellulosic feedstocks like wood chips and crop residues. It has a higher octane number than gasoline, providing premium blending properties and reducing air pollution. However, ethanol contains less energy per gallon than gasoline, and its impact on vehicle fuel economy is dependent on several factors.
Firstly, ethanol's impact on fuel economy depends on the ethanol content in the fuel. In the United States, most finished motor gasoline contains about 10% ethanol by volume, known as E10. E10 gasoline typically reduces vehicle fuel economy by about 3% compared to gasoline without ethanol. Higher ethanol blends, such as E15 (15% ethanol) and E85 (up to 85% ethanol), are also available but are generally used in flex-fuel vehicles designed to operate on ethanol-gasoline blends. The higher the ethanol content, the lower the energy content of the fuel, which can result in decreased fuel economy or miles travelled per gallon.
Secondly, ethanol's impact on fuel economy is influenced by the amount of denaturant added to the ethanol to make it unfit for human consumption. Federal law requires a minimum of 2% denaturant in fuel ethanol, but the actual amount may be higher. The energy content of denaturant is similar to that of pure gasoline, so the impact on fuel economy varies depending on the denaturant level.
Additionally, ethanol's impact on vehicle fuel economy is related to the type of engine in the vehicle. Engines optimized for gasoline may experience a more significant decrease in fuel economy when using ethanol blends compared to engines designed to run on ethanol or flex-fuel vehicles. Flex-fuel vehicles can use ethanol-gasoline blends up to E85 and are typically labelled as such.
While ethanol blends can reduce vehicle fuel economy, it is important to consider the benefits and trade-offs. Ethanol has a positive energy balance, meaning its production requires less energy than the amount contained in the fuel itself. Cellulosic ethanol, produced from waste or dedicated crops with lower water and fertilizer requirements, further improves the energy balance and reduces fossil fuel energy use in production. Ethanol also reduces greenhouse gas emissions and lessens dependence on imported oil. However, there are concerns about the impact of ethanol on food prices, as corn, a common feedstock, has seen price increases due to demand from ethanol plants.
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Ethanol's sustainability and environmental impact
Ethanol is a renewable fuel made from various plant materials, or "biomass", such as corn grain, sugar cane, wood chips, and crop residues. In the United States, 94% of ethanol is produced from the starch in corn grain. The use of ethanol in fuel has been increasing since the 1970s due to its potential to reduce US oil imports, and most gasoline sold in the US contains some ethanol.
Sustainability
Ethanol is a renewable fuel, and its production does not require more energy than the amount of energy contained in the fuel itself. In fact, ethanol produced from corn demonstrates a positive energy balance. Cellulosic ethanol, which is made from waste, coproducts of another industry (e.g. wood, crop residues), or dedicated crops with lower water and fertilizer requirements, further improves the energy balance of ethanol by reducing the amount of fossil fuel energy used in production.
Environmental Impact
The environmental impact of ethanol depends on the feedstocks used and the methods of production. Ethanol made from corn kernel fiber and other cellulosic feedstocks can deliver reductions of 80% or more in greenhouse gas (GHG) emissions compared to gasoline. According to the Department of Energy's Argonne National Laboratory, grain-based ethanol cuts GHG emissions by 44 to 52% compared to gasoline. Researchers from Harvard, MIT, and Tufts concluded that today's corn ethanol offers an average GHG reduction of 46% versus gasoline.
However, there are concerns about the environmental impact of increasing corn production for ethanol, particularly the impact on the US heartland. Growing corn requires the use of chemicals and fertilizers, and expanding corn crops can lead to indirect land-use effects, such as deforestation to meet biofuel demand. Additionally, moving from E10 to E30 blends would result in more carbon emissions, more toxic pollutants in drinking water, and higher water bills for Midwestern residents.
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Ethanol production and energy balance
Ethanol is a renewable fuel made from various plant materials known as biomass. The most common sources of biomass for ethanol production are starch- or sugar-based feedstocks, such as corn grain, sugar cane, or cellulosic feedstocks like wood chips or crop residues. In the United States, 94% of ethanol is produced from corn grain.
The production of ethanol involves several steps, including growing, collecting, and transporting biomass feedstocks to an ethanol production facility. At the facility, the feedstocks are converted into ethanol, which is then transported to a fuel terminal or end-user. The energy required to turn raw feedstock into ethanol depends on the type of feedstock used. For example, cellulosic ethanol, which is produced from waste or coproducts of another industry, has a better energy balance than corn-grain ethanol because it requires less energy for production and has lower water and fertilizer requirements.
The energy balance of ethanol production has been a subject of debate. Some studies show that ethanol has a positive energy balance, meaning more energy is derived from ethanol than is used to produce it. For example, a 2008 study by the University of Nebraska found a 5.4 energy balance for ethanol derived from switchgrass. On the other hand, critics of ethanol production, such as retired entomologist David Pimentel, argue that ethanol is "energy negative," claiming that it takes more energy to produce than is contained in the final product.
The energy balance of ethanol also depends on the efficiency of the production process. Over time, corn growers have become more efficient, producing more corn per acre while using less energy. Additionally, ethanol plants have improved their processes, producing more ethanol from a bushel of corn while reducing energy consumption. These improvements in production efficiency contribute to a more favorable energy balance for ethanol.
In conclusion, the energy balance of ethanol production depends on various factors, including the type of feedstock used, the efficiency of the production process, and the energy content of the final product. While there are differing opinions on the net energy returns of ethanol, it remains a significant component of the fuel supply, particularly in the United States, where it is blended into gasoline to reduce air pollution and decrease dependence on imported oil.
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Frequently asked questions
Most finished motor gasoline sold in the United States contains about 10% ethanol by volume. However, the ethanol content of motor gasoline does not exceed 10% by volume.
Ethanol is a renewable fuel made from various plant materials collectively known as biomass. It is also known as ethyl alcohol, grain alcohol, and EtOH.
Ethanol’s impact on fuel economy depends on the ethanol content in the fuel and whether an engine is optimized to run on gasoline or ethanol. The energy content of ethanol is about 33% less than pure gasoline.
Ethanol is blended with gasoline to meet a federal government mandate known as the Renewable Fuel Standard (RFS). The reasons for this standard include supporting U.S. agriculture, improving fuel security, and reducing the imbalance between exports and imports. Ethanol also oxygenates the fuel, making it safer for the water supply.
