Biodegradation of organic material occurs in nature through the action of both aerobic and anaerobic microorganisms. In aerobic systems, partial oxidation of the ingested organic material is the result yielding carbon dioxide and water and undigested residue. Anaerobic bacteria will also degrade organic matter, including some abiogenic forms, in the absence of oxygen with ultimate products being non-reactive residues, carbon dioxide, and methane. These bacteria naturally occur in the environment in anaerobic“niches” such as marshes, sediments, wetlands, and the digestive tracts of ruminants and certain species of insects.
Facultative organisms are capable of persisting in either environment.
Anaerobic digestion (AD) is a bacterial fermentation process that operates without free oxygen and results in a biogas containing mostly methane and carbon dioxide. It occurs naturally in anaerobic niches such as marshes, sediments, wetlands, and the digestive tracts of ruminants and certain species of insects. AD is also the principal decomposition process occurring in landfills.