The anaerobic digestor is reactor in which fermentation process is carried out in absence of oxygen. There are various microbes such as different species of anaerobic bacteria are involved in this process. The anaerobic digestion or sewage takes place in an anaerobic digestor. The wastes from plants and animals are introduced in this reactors. The decomposition of this organic matter is carried out by fermentation performed by bacteria.

The various energy crops include Sugarcane, Sugar beet, Potato, Tapioca and Maize. Energy crops can be used to produce alcohol and or energy fuels.

Baker?s yeast produces 3 enzymes namely-amylase, maltase and zymase. Amylase changes a small amount of starch into maltose. Maltase changes maltose to glucose and zymase acts on glucose to form bubbles of ethyl alcohol and carbon dioxide.