COMPOSTING OF SEPARATED SOLID SWINE WASTES

The effects of various bulking agents were examined on the efficiency of composting the fibrous solids obtained from swine manure after a liquid/solids separation process. The effects on the quality of the resulting composts were also examined. The separated solids were either composted without bulking agents, or mixed with different portions of peat moss and/or sawdust. Aeration rates were also varied in different experimental sets. A self-heating mode of operation was adopted. The results indicated that the fibrous solids from a liquid/solids separation process could be composted in small reactors with or without the addition of bulking agents. The composting masses reached thermophilic temperatures (45-70·C) and met regulatory requirements with or without aeration. Aeration rates of 0·04 to 0·08 l/min per kg volatile matter and an intermittent mode of aeration are recommended for the composting of separated swine manure. Based on measured compost characteristics and composition, the finished composts made from a manure/peat moss mixture had the best quality in terms of moisture content, nitrogen content, carbon-to-nitrogen ratio and colour of the product. © 1993 Silsoe Research Institute.