Ethanol made from corn and other crops

Ethanol is a clear, colorless alcohol made from the sugars found in grains, such as corn, sorghum, and barley, as well as potato skins, rice, sugar cane, sugar beets, and yard clippings. Ethanol is a renewable fuel because it is made from plants. There are several ways to make ethanol using these sources.

USDA researchers adding yeast to begin ethanol fermentation
 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.

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

The most common ethanol production processes today use yeast to ferment the sugars and starch in corn. Corn is the main ingredient for fuel ethanol in the United States because of its abundance and low price. Most ethanol is produced in corn-growing states in the Midwest. The starch in the corn is fermented into sugar, which is then fermented into alcohol.

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

Cellulosic ethanol

Ethanol can also be produced by breaking down cellulose in woody fibers. Cellulosic ethanol is considered an advanced biofuel and involves a more complicated production process than the process used to make conventional ethanol.

Trees and grasses are potential feedstocks (the raw material needed to make a product) for cellulosic ethanol production. Trees and grasses require less energy, fertilizers, and water than grains and can also be grown on lands that are not suitable for growing food. 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.

History of ethanol

Model T car
Model T vehicle

Source: Stock photography (copyrighted)

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 like kerosene. Ethanol production declined sharply because of this tax, and production levels did not begin to recover until the tax was repealed in 1906.

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.

Ethanol is once again used to fuel automobiles

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 requirements for cleaner-burning fuels.

In 2005, Congress enacted a Renewable Fuel Standard (RFS) 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 2014, about 13 billion gallons of ethanol were added to the gasoline consumed in the United States.