A novel bioreactor simulating composting of municipal solid waste

Abstract

A bioreactor (19L) was developed to simulate municipal solid waste composting. The purpose of the reactor was to provide a test system for evaluating physical changes in newly developed materials that may enter the portion of the waste stream being composted. To minimize variation in feed stock, the bioreactor utilized a defined waste mixture consisting of rabbit chow with alfalfa and shredded newspaper inoculated with a 1:1:1 mixture of leaf compost, garden soil, and cow manure. During the first 24 h, the mixture self-heated from 37°C. Scanning electron micrographs showed that populations of Bacillus-like bacteria dominated the composting mass. Enzyme activity, total bacterial CFU per gram dry weight, acridine orange direct microscopic counts of bacteria, and cellulose mineralization rates increased initially and remained high throughout a 28 day incubation period. After 28 days, volatile solids had decreased from 88 to 77% of the dry weight, and carbon nitrogen ratios had decreased from 35 to 14. It was concluded that under moist, aerobic conditions, simulated solid waste can undergo changes comparable to those reported for municipal solid waste in full-scale composting systems. Thus, the reactor is appropriate for testing the fate of potentially compostable materials.