In North America, most ethanol is produced from grain (mostly corn and some wheat and barley). Some operations integrate existing industrial processes and ethanol production by making use of "waste" feedstocks such as potato, waste cheese whey, brewery waste, sugar cane, bagasse, and rice hulls. There are also a variety of cellulose-based feedstocks that can be used to produce ethanol.
Ethanol is currently produced primarily through the fermentation of sugars. The process uses enzymes to convert starches to simple sugars, and yeasts to ferment the sugars into ethanol.
There are two processes used to produce ethanol from grain. Dry-milling is used for grains such as wheat, barley and corn. Wet-milling is used exclusively for corn. For more information on these production processes,follow these links:
The renewable biological feedstocks used to produce ethanol are collectively referred to as biomass. High starch agricultural crops are typically used to produce ethanol. Advances are also being made to improve the more difficult conversion of cellulosic biomass such as forestry products, agricultural residues (straw, grasses), and even municipal waste.