Composting and Solid State Fermentation

Abstract

Large amounts of organic materials are produced annually in nature that are degraded by microbial action. The decomposition of organic materials takes place slowly on the surface of ground at ambient temperatures. The natural process of degradation can be speeded up by gathering organic material into heaps to conserve part of the heat of fermentation so that the temperature of the mass rises and faster reaction rates are attained. This accelerated process of the decomposition of organic matter by a mixed population of microorganisms in a warm, moist, aerobic environment is known as composting. The process of composting involves an interaction between the organic waste, microorganisms, moisture and oxygen. When the moisture content of the organic waste is brought to a suitable level, and the mass aerated, microbial action speeds up. While attacking organic matter, mixed population of microbes harbouring it multiply and liberate CO2, water, other organic products and energy. A part of the energy is used in metabolism, and the remainder is given off as heat. The end product, compost, is made up of the more resistant residues of the organic matter, breakdown products and dead and living microorganisms, along with products formed from further chemical reactions between these materials. The overall process of composting has been illustrated, as in Fig.1, by Biddlestone and Gray (10).