But unlike gasoline, which is made by distilling crude oil, ethanol is made from the starchy parts of plants. Most ethanol in this country is created through fermentation of corn. Microscopic yeast cells break down the starch and water, creating ethanol and carbon dioxide gas. In addition to being a renewable fuel, ethanol helps to reduce air pollution. When anything burns in air, molecules of that substance combine with oxygen.
Gasoline is a substance made of carbon and hydrogen.
There isn't enough oxygen left to combine with the remaining carbon atoms. Like gasoline, ethanol is made of carbon and hydrogen, but in addition it contains its own supply of oxygen. In some parts of the U.S., ethanol is mixed with gasoline at 1 part ethanol to 9 parts gasoline to help reduce air pollution. No adjustment is needed for a car's engine to burn this mixture. Some new cars are designed to burn fuel blends of up to 80 percent ethanol.