Anaerobic Digestion is a biochemical process during which complex organic matter is decomposed in absence of oxygen, by various types of anaerobic microorganisms. The process is similar to that found in nature as in the stomach of ruminants such as cows. Anaerobic digestion is a purely bacterial process. In a biogas installation, the outcome of the Anaerobic Digestion process is the biogas and the digestate. If the feedstock for Anaerobic Digestion is a homogenous mixture of more than one feedstock types such as animal slurries and organic wastes from food processing factories, it is known as "co-digestion" and is the most common biogas applications today.