Ethanol << ETH uh nohl or ETH uh nol >> is a type of alcohol found in alcoholic beverages and used as an automobile fuel. It is a clear, colorless liquid that mixes readily with water. Ethanol dissolves a number of chemicals, making it valuable to chemical manufacturers as a solvent (substance that dissolves other substances). It is sometimes called ethyl alcohol or grain alcohol.
Ethanol’s chemical formula is CH3CH2OH. It has a relative molecular mass of 46.07. A molecule’s relative molecular mass, sometimes called its molecular weight, is the amount of matter in the molecule. Ethanol boils at 172 °F (78 °C) and freezes at –173 °F (–114 °C). At 20 °C, its density is 0.7893 grams per cubic centimeter.
There are two ways to manufacture ethanol. In one method, ethylene (a gas made from petroleum) is combined with water. The other method uses fermentation, a biological process in which tiny organisms called yeast convert sugars into ethanol. The sugars used typically come from crops also grown for food. Ethanol fermentation was one of the first chemical processes developed by people. Today, it ranks as the most common method for making ethanol.
People use most ethanol for fuel. The United States and Brazil produce about three-fourths of the world’s ethanol supply. The United States makes most of its ethanol by fermenting corn. Brazil uses sugar cane instead.
In the late 1970’s, the U.S. fuel industry introduced ethanol to reduce dependence on foreign oil. Fuel producers developed a mixture of 90 percent gasoline and 10 percent ethanol. This mixture, then called gasohol, is now known as E10. At the same time, Brazil introduced a 100 percent ethanol replacement for gasoline, E100. Traditional automobiles can use E10 without any modification, but E100 requires specially designed vehicle fuel systems. In the 1990’s, U.S. automakers introduced flexible fuel vehicles (FFV’s), which use any mixture of ethanol and gasoline containing up to 85 percent ethanol or E85. People in the United States drive millions of FFV’s, but E85 fuel is not yet widely available. Brazil’s automobiles are now mostly FFV’s. They run on gasoline with up to 25 percent ethanol, or E25.
Ethanol, unlike gasoline, comes from renewable resources that can be regrown again and again. However, many people have questioned how farmers should balance demand for ethanol fuel with the need to grow crops for food. In the United States, some byproducts of corn used in ethanol production are fed to livestock. Scientists are also developing technologies to produce ethanol from plant wastes, rather than food crops. For example, cellulosic ethanol is produced from woody plant wastes.
See also Alcohol (Ethanol) ; Alcoholic beverage ; Renewable energy ; Switchgrass .
