Chemical Alteration of Substrates during Initial Thermophilic Phase of Composting

摘要

Composting technologies has been used successfully for treatment of organic waste from agriculture, industrial process and urban activities. Some examples of organic waste are food waste, orange juice process, swine and cattle manure, poultry, sugar cane mill waste, bio- solids (sludge). These represent a valuable reservoir of plant nutrients in organic forms, particularly nitrogen (N), phosphorus (P) and sulphur (S). However, before the use of such materials as fertilizers, they must be converted into a stable product free of odours and pathogens, and in a physical form that is suitable for soil application. Aerobic-thermophilic (35-65 oC) composting is a proven technology that can achieve these objectives. Composting as a process involves the biological decomposition of organic matter under controlled, aerobic conditions into a humus-like stable product [1]. The value of a compost as a soil ameliorant can be due to several factors: (i) to improve the chemical composition of soil through the supply of plant nutrients; (ii) to improve the physical condition of soil through lower bulk density, resulting in improved aeration and water holding capacity. Biochemical manifestations occurring during composting process include an increase in humic substances over time, specifically, humic acids. Carbohydrates are the primary source of energy for microorganisms in the process, following by cellulose and hemicellulose. Lignin is degraded through microbial action to smaller polyphenolic compounds and intermediate phenols. The enzymatic action turns these compounds in quinines and later condensed humic acids [1].