Laboratory Composter for Simulation Studies

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Abstract
A self‐heating laboratory composter comprised of a covered, double‐walled, insulated tank containing water, an air‐tight cylinder submerged in the tank, an inner screen mesh cylinder that held the organic material, a heater‐circulator, and a differential temperature control system was built and tested for use in studies simulating the biochemical changes that occur during composting. A mixture of raw, limed sewage sludge and woodchips was composted, and the weight‐loss data obtained were similar to that from the pilot plant composting facility at Beltsville, Md. The mixture lost 33% of its wet weight, and 9% of its dry weight during 28–50 d of composting. Six to ten percent of the total N was lost. There were two major temperature peaks, which correlated with CO2 increases. Peak NH3 evolution occurred when CO2 evolution decreased. All preliminary data indicate that the laboratory composter provides a comparable simulation of a large composting facility.