May 2, 2013

Gasohol

Gasohol, a mixture of 90% unleaded gasoline and 10% ethyl alcohol (ethanol), has gained acceptance as a fuel for motor vehicles. It is comparable in performance to 100% unleaded gasoline with the added benefit of superior antiknock properties (no premature fuel ignition). No engine modifications are needed for the use of gasohol.

Since corn is the most abundant United States grain crop, it is predominately used in producing ethanol. However, the fuel can be made from other organic raw materials, such as oats, barley, wheat, milo, sugar beets, or sugar cane. Potatoes, and cassava (a starchy plant) and cellulose (if broken up into fermentable sugars) are possible other sources. The corn starch is processed through grinding and cooking. The process requires the conversion of a starch into a sugar, which in turn is converted into alcohol by reaction with yeast. The alcohol is distilled and any water is removed until it is 200 proof (100% alcohol).

One acre of corn yields 250 gallons (946 liters) of ethanol; an acre of sugar beets yields 350 gallons (1,325 liters), while an acre of sugar can produce 630 gallons (2,385 liters). In the future, motor fuel could be produced almost exclusively from garbage, but currently its conversion remains an expensive process. (The Handy Science Answer Book, compiled by the Science and Technology department of the Carnegie Library of Pittsburgh)