Thermophilic aerobic digestion process for producing animal nutrients

Abstract

Biochemically degradable organic material, for example, animal waste matter, such as manure produced by hogs, sheep, cattle, chickens and humans is aerobically digested at thermophilic digestion temperatures to produce various digested products, including single cell proteinaceous material suitable for feeding to animals as part of the animals' nutritive diet. Biodegradable material is introduced into a digesting zone that is sufficiently insulated to prevent any substantial heat loss from the digesting material during the digestion process. An oxygenating gas such as air is introduced into the digesting material during all phases of the digestion. The digesting material is simultaneously vigorously agitated. The waste material is placed into the digester at ambient temperatures and is contacted with the oxygenating gas at a rate and is agitated at a level effective to cause thermogenic microbial digestion of the materials present in the waste matter. Since the microbial digestion is thermogenic and because the digester is insulated, the temperature of the digestion waste material will rise from ambient to thermophilic digestion temperatures. Thereafter, the digesting mixture is continuously contacted with the oxygenating gas at a rate and is agitated at a level effective to maintain the thermophilic digestion temperatures for a period of at least four days.