As their names imply, sugar beets and sugar cane contain natural sugar. Crops such as corn, wheat and barley contain starch that can be easily converted to sugar. Most trees and grasses are made of cellulose, which can also be converted into sugar, although not as easily as starch.
Most ethanol is produced using a four-step process:
- The ethanol feedstock (crops or plants) are ground up for easier processing;
- Sugar is dissolved from the ground material, or the starch or cellulose is converted into sugar;
- Microbes feed on the sugar, producing ethanol and carbon dioxide as byproducts; and
- The ethanol is purified to achieve the correct concentration.
Ethanol: Frequently Asked Questions