Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 209

Fermentation is an anaerobic process that breaks down the glucose within organic materials, and the process is a series of chemical reactions that convert sugars to alcohol or acid. Yeast or bacteria are added to the biomass material, which feed on the sugars to produce ethanol and carbon dioxide. The process is used commercially on a large scale in various countries to produce ethanol from sugar crops (sugar cane, beet) and starch crops (maize, wheat).

The biomass is ground down, and the starch is converted by enzymes to sugars. Yeast then converts the sugars to ethanol. Pure ethanol is produced by distillation which is a relatively energy intensive step. Approximately 450 L of ethanol can be produced per tonne of dry corn. The remaining solids can be used as cattle feed. In the case of sugar cane, the remaining bagasse can also be used as fuel for boilers or gasification processes.

Conversion of lignocellulosic biomass (such as wood and grasses) requires acid or enzymatic hydrolysis before the resulting sugars can be fermented to ethanol. Such hydrolysis techniques are currently at the pre-pilot stage.

See also: Fermentation, Fermentation Chemistry.