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Biofuels explained Ethanol

Ethanol is made from biomass

Ethanol is a renewable biofuel because it is made from biomass. Ethanol is a clear, colorless alcohol made from a variety of biomass materials called feedstocks (the raw materials used to make a product). U.S. fuel ethanol producers mostly use food grains and crops with high starch and sugar content as feedstocks for making ethanol such as corn, sorghum, barley, sugar cane, and sugar beets. Ethanol can also be made from grasses, trees, and agricultural and forestry residues such as corn cobs and stocks, rice straw, sawdust, and wood chips. Ethanol is made from these feedstocks in several ways.

Fermentation is the most common method for producing fuel ethanol

The most common ethanol production processes today use yeast to ferment the starch and sugars in corn, sugar cane, and sugar beets. Corn is the main feedstock for fuel ethanol in the United States because of its abundance and relatively low price historically. The starch in corn kernels is fermented into sugar, which is then fermented into alcohol.

Sugar cane and sugar beets are the most common feedstocks used to make fuel ethanol in other parts of the world. Because alcohol is made by fermenting sugar, sugar crops are the easiest ingredients to convert into alcohol. Brazil, the world's second-largest fuel ethanol producer after the United States, makes most of its fuel ethanol from sugar cane. Most of the cars in Brazil can run on pure ethanol or on a blend of gasoline and ethanol.

Microbiologist Nancy Nichols and biochemical engineer Bruce Dien add yeast to a bioreactor to begin ethanol fermentation. Bt and non-Bt corn hybrids were compared for ethanol yields. Photo by Scott Bauer.

USDA researchers adding yeast to begin ethanol fermentation

Photo Credit: Scott Bauer, USDA Agricultural Research Service (public domain)

Cellulosic ethanol is a large potential source of fuel ethanol

Ethanol can also be produced by breaking down cellulose in plant fibers. This cellulosic ethanol is considered an advanced biofuel and involves a more complicated and costly production process than fermentation. However, there are large potential non-food crop sources of cellulosic feedstocks. Trees, grasses, and agricultural residues are potential feedstocks for cellulosic ethanol production. Trees and grasses require less energy, fertilizers, and water to grow than grains do, and they can also be grown on lands that are not suitable for growing food crops. Scientists have developed fast-growing trees that grow to full size in 10 years. Many grasses can produce two harvests a year for many years without annual replanting. Despite the technical potential for cellulosic ethanol production, economical production has been difficult to achieve and only relatively small amounts of cellulosic fuel ethanol have been produced United States.

History of ethanol

In the 1850s, ethanol was a major lighting fuel. During the Civil War, a liquor tax was placed on ethanol to raise money for the war. The tax increased the price of ethanol so much that it could no longer compete with other fuels such as kerosene. Ethanol production declined sharply because of this tax, and production levels did not begin to recover until the tax was repealed in 1906.

Model T vehicle

Model T car

Source: Stock photography (copyrighted)

The Model T ran on ethanol

In 1908, Henry Ford designed his Model T, a very early automobile, to run on a mixture of gasoline and alcohol. Ford called this mixture the fuel of the future. In 1919, when Prohibition began, ethanol was banned because it was considered an alcoholic beverage. It could only be sold when mixed with petroleum. Ethanol was used as a fuel again after Prohibition ended in 1933.

Most motor gasoline now contains fuel ethanol

Ethanol use increased temporarily during World War II when oil and other resources were scarce. In the 1970s, interest in ethanol as a transportation fuel was revived as oil embargoes, rising oil prices, and growing dependence on imported oil increased interest in alternative fuels. Since that time, ethanol use and production has been encouraged by tax benefits and by environmental regulations that require cleaner-burning fuels.

In 2005, Congress enacted a Renewable Fuel Standard that set minimum requirements for the use of renewable fuels, including ethanol. In 2007, the RFS renewable fuel use targets were set to rise steadily to a level of 36 billion gallons by 2022. In 2020, about 12.6 billion gallons of fuel ethanol were consumed in the United States. Most motor gasoline now sold in the United States is about 10% fuel ethanol by volume.

Last updated: June 21, 2021