Ethanol is the most widely used biofuel today. It is used to increase octane and improve the emissions quality of gasoline. Even the bagasse generated by the process is not wasted and it is utilized in power plants. The U.S. consumes a little more than 20 million barrels of oil a day and growing. The largest end uses are gasoline and diesel in motor vechicles.
Currently the main feedstock of ethanol biofuel production is corn. Corn is an energy intensive crop that requires petroleum derived fertilizers. Using corn to produce alcohol could save farmers additional petroleum if the farmers are feeding the byproduct to livestock and if the excrement from the animals is then used as fertilizer for the corn. Most of the fermentation plants have been built in corn-producing regions.
The production of ethanol involves the use of yeast to convert sugar into alcohol. That fermentation process has been used for thousands of years, but on a much larger scale.
Production of dry-mill results in known solid byproducts such as distillers grains and solubles (DGS), that can be dried and used to provide feed for livestock. In some plants adjacent to cattle feed lots, the grains can be fed in a high moisture state to livestock, bypassing the requirement for drying which can and save both energy and costs. The wet-mill process, which begins by immersing the grain in water and acid, generally resulting in corn oil, corn gluten meal to feed chicken, and sweeteners in addition to ethanol. Wet mills tend to be much larger than dry mills.