General · EdgepediaSeptember 17, 20268 min read

Ethanol fuel

Ethanol fuel is a renewable motor fuel made by fermenting sugars from plant materials, collectively called biomass, and blended with gasoline for use in conventional and flexible fuel vehicles. More than 98% of gasoline sold in the United States contains ethanol, typically as E10, to oxygenate the fuel and reduce air pollution¹. Fuel ethanol is chemically identical regardless of feedstock: ethanol (CH₃CH₂OH, also called ethyl alcohol or grain alcohol) is a clear, colorless liquid whether produced from corn grain, as it primarily is in the United States, from sugar cane, as it primarily is in Brazil, or from cellulosic materials such as wood chips and crop residues¹.

Key fact	Detail
Common blends	E10 (10% ethanol) in nearly all U.S. gasoline; E15 (10.5%–15%) approved for model year 2001 and newer light-duty vehicles; E85 (51%–83%) requires a flexible fuel vehicle¹^•²
Energy content	Denatured ethanol contains about 35% less energy per gallon than gasoline; lower heating value 76,300 Btu/gal versus 116,900 for gasoline¹^•³
Octane	Ethanol's octane rating (R+M)/2 is 113, versus 86–94 for gasoline; 10% ethanol lifts lower-octane gasoline to the standard 87 octane¹^•³
U.S. feedstock	94% of U.S. ethanol is produced from the starch in corn grain¹
Yield	1 bushel of corn yields 2.7 gallons of ethanol and 17.5 pounds of distillers' dried grains⁴
U.S. capacity	191 plants with 18,477 million gallons per year of capacity as of January 1, 2025, concentrated in Midwest corn states⁵
Global scale	World fuel ethanol production reached 115 billion liters in 2019; about 80% is produced in the United States and Brazil⁶^•⁷

Blends and vehicle compatibility

Ethanol is sold in blends named for the percentage of ethanol they contain. Nearly all fuel-grade ethanol is sold as E10, a 10% blend approved for use in all conventional light-duty vehicles². E15, containing 10.5% to 15% ethanol, is approved for model year 2001 and newer light-duty conventional vehicles, and can be dispensed from fuel terminals or through a blender pump that draws from E10 and E85 tanks at a station²^•¹. E85 is a high-level ethanol blend that contains 51% to 83% ethanol depending on geography and season, and can only be used in flexible fuel vehicles (FFVs), which are designed to run on any gasoline-ethanol blend from E0 up to E85²^•⁸^•²². E15 cannot be used in on-highway motorcycles, heavy-duty engines such as school and transit buses, nonroad vehicles such as boats and snowmobiles, or model year 2000 and older cars and light trucks⁹.

Fuel properties and performance

Ethanol's chemistry changes how it behaves in an engine compared with hydrocarbon-only gasoline. Its oxygen content (35% oxygen by weight, against none in gasoline's C₄ to C₁₂ hydrocarbons) raises the octane rating to 113, which is why refiners use it as an octane enhancer: lower-octane gasoline blended with 10% ethanol reaches the standard 87 octane³^•¹^•².

The trade-off is energy content. Ethanol's lower heating value is 76,300 Btu per gallon against 116,900 for gasoline, and its fuel economy relative to gasoline is about 67% on a per-gallon basis; E85 delivers roughly 73% of gasoline's mileage, depending on the vehicle and the ethanol percentage³. Ethanol also has a much lower Reid vapor pressure (2.3 psi versus 7–16 for gasoline), a lower ignition temperature of about 850 °F versus 495 °F, and a stoichiometric air-fuel ratio of 9 by weight versus 14.7 for gasoline, which is why engines must be calibrated differently for high-ethanol blends³.

Production

In the United States, ethanol is made mainly in dry mills, which grind dry corn, ferment and distill the starch into ethanol, and leave a residual coproduct called distillers' grains consisting of the protein, minerals, fat, and fiber left after the starch is removed¹⁰. A typical plant built in recent decades has grown from about 15 million gallons per year to 40–100 million gallons per year, and a May 2015 cost estimate put total production cost at $1.30 per gallon for a baseline plant using natural gas for distillation and drying¹⁰.

Distillers' grains. These coproducts are commodities in their own right and the most significant coproduct of grain ethanol production in both size and value¹¹. Wet distillers grains, with moisture above 50 percent, serve local markets near the processing facility because of their water weight, while dried distillers grains can move by truck, rail, barge, or ship to international markets¹²^•¹⁰. They are used chiefly as feed supplements for ruminants such as beef and dairy cattle, and increasingly in rations for monogastric animals such as hogs and poultry, which digest them less readily¹².

Cellulosic ethanol. Ethanol can also be made from cellulose, the structural polysaccharide of plant cell walls, through pretreatment, hydrolysis to release sugars, fermentation, and distillation¹³. Cellulosic feedstocks such as wood chips, crop residues, and dedicated crops like switchgrass and miscanthus have lower water and fertilizer requirements than corn, and using biomass to power the conversion process reduces the fossil energy input further¹.

Because ethanol cannot be transported in petroleum product pipelines, it moves from production facilities by rail, tanker and barge, and truck to blending terminals, and then by truck to fueling stations¹⁴.

Global market

Fuel ethanol production reached 115 billion liters globally in 2019, then contracted 14.5% to 98 billion liters in 2020 as the Covid-19 crisis cut gasoline demand, with about 80% of the year-over-year fall occurring in Brazil and the United States; output was anticipated to return to near 2019 levels by 2022⁶. Production is concentrated: roughly 80% of the global market comes from just two countries, the United States and Brazil⁷.

Brazil. Brazil's dual-fuel program, launched in 1975, created a fleet of tens of millions of vehicles that can run on any combination of ethanol and gasoline; drivers there can choose between hydrous ethanol (E100) and a gasoline blend containing 30% biofuel²³. Ethanol comprises approximately 40% of the fuel used in light vehicles in Brazil⁷^•¹⁵. Brazilian sugarcane and ethanol yields rose steadily for 40 years at compound annual growth rates of 1.37% and 2.00% respectively, before declining around 2012 when government policies that lowered fossil fuel prices to control inflation depressed ethanol prices and investment⁷.

United States trade. The United States has been an annual net exporter of fuel ethanol since 2010, though it still imports some, mostly from Brazil¹⁴. Exports set records in 2024 and again in 2025: through the first seven months of 2025 they averaged 138,000 barrels per day, 9% above 2024's annual record, with 13% of domestic production exported versus a record 12% in 2024 and a pre-pandemic high of 11% in 2018. Most of the recent export growth went to the Netherlands, likely reflecting demand in Europe¹⁶. U.S. production capacity reached almost 18.5 billion gallons per year in 2025, 73% of all U.S. biofuels capacity, and grew more in 2024 than in previous years even as domestic consumption stayed flat¹⁷.

Energy balance and greenhouse gas emissions

Turning any raw feedstock into ethanol requires energy, but corn ethanol produced in the United States shows a positive energy balance, meaning production does not consume more energy than the fuel contains¹. U.S. policy support came through the Renewable Fuel Standard, established by Congress in 2005 and expanded in 2007; from the 2005 corn marketing year to 2017/18, ethanol production rose 288 percent, from roughly 4.5 billion gallons to over 17 billion, and now represents over 37 percent of U.S. corn usage¹¹.

Lifecycle greenhouse gas accounting for corn ethanol includes agriculture, biorefining, transport, land use change, and credit for coproducts. The California Air Resources Board's illustrative life cycle for corn ethanol totals about 70 gCO₂e/MJ, with agriculture contributing 29 g/MJ (11 from fertilizer and soil amendment production, 14 from soil emissions, and the remainder from on-farm energy use), biorefining 27 g/MJ, land use change 20 g/MJ, and coproducts crediting −12 g/MJ¹⁸. EPA's 2010 analysis concluded that by 2022, corn ethanol from a new natural-gas-powered refinery would have greenhouse gas emissions about 21 percent lower than gasoline, though it projected indirect land use change as the single largest source category, about 40 percent of net emissions¹⁹. A 2018 USDA-commissioned life-cycle analysis found that post-2010 research indicates those projected land-use-change emissions were much higher than what actually occurred¹⁹. A 2018 study in the journal Global Change Biology Bioenergy, conducted independently, showed that corn growers who boost soil organic carbon—through measures like applying manure and planting cover crops—cut the lifecycle greenhouse gas emissions of their ethanol to roughly 40 percent below those of gasoline.²⁰

The climate case for corn ethanol remains debated. A modeling study published in 2022 states that corn ethanol does not substantially reduce greenhouse gas emissions compared with petroleum-based fuels, and that corn production imposes externalities including nitrogen leaching, higher food prices, water scarcity, and indirect land use change²¹.

References

Topic: Encyclopedia › Technology and the built world › Energy technology › Renewable energy and biofuels

Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026; Oct 25, 2026 · Last review: Oct 15, 2026

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