Corn supplies most of the feedstock for fuel ethanol produced in the United States.
American ethanol is mainly made by fermenting starch from field corn. Milling breaks the kernels down, enzymes convert starch into sugars, and yeast ferments those sugars into ethanol. The fuel is commonly blended with gasoline, especially as E10, which contains 10 percent ethanol.
This differs from Brazil, where sugarcane is the dominant ethanol crop. Corn ethanol production also creates distillers grains, a protein-rich coproduct widely used as animal feed, along with carbon dioxide and corn oil. These coproducts affect the economics and overall resource balance of the industry.
Corn is not the only possible biofuel crop. Cellulosic ethanol can use grasses, straw, wood residues, and other fibrous plant material, but commercial-scale cellulosic production has remained more difficult because cellulose is harder to break into fermentable sugars. The United States is the world's leading fuel-ethanol producer, with the Midwest containing many major plants.