Innovative Two-Stage Process for the Recovery of Energy and Compost from the Organic Fraction of Municipal Solid Waste (MSW)

Abstract

An innovative system for stabilizing the organic fraction of municipal solid waste (OFMSW) has been documented on a pilot scale at the Civil Engineering Department of the University of California at Davis. The system involves the combined methods of high-solids anaerobic digestion and aerobic composting for the recovery of energy and the production of compost from the OFMSW. The performance of the high-solids anaerobic reactor was monitored for three mass retention times. The anaerobic digester was operated under extreme as well as normal conditions. The performance of the aerobic compost unit was monitored based on the physical and chemical characteristics of the final humus by-product. In general, the combined process was very stable at a 30 d retention time and is capable of removing essentially all of the biodegradable fraction of the organic fraction of MSW. A biogas production level of up to 6 liters per liter of active volume of reactor was achieved. The process stability and gas production decreased slightly when the retention time was reduced to 15 d. The output from the second stage is a fine humus-like material with a thermal content of about 14.80 MJ/kg.