Evaluation of In-vessel Composting of University Postconsumer Food Wastes

A prototype in-vessel composting unit, which includes air circulation and misting systems, was designed and built as a senior capstone project at the Bio-Resource Engineering Department at the University of Maine. The university Office of Resource Conservation and Recovery initiated a recycling program for postconsumer food waste generated by the residence hall commons areas in 1991. This food waste is composted using the traditional methods of windrow composting and experiences vermin and odor problems. The prototype in-vessel system was evaluated to determine if it reduced the environmental challenges presented by vermin and odor control. Various mixtures of food waste and bulking agents were tried ranging from 1:4 (food waste:bulking agent) to 1:l. Results show that if the food waste is composted in the in-vessel system for at least 14 days, before being windrowed, the vermin and odor problems are reduced. Computer controlled temperature, humidity, oxygen, and carbon dioxide monitoring equipment were evaluated in order to test certain management strategies. Manage ment schemes of air circulation, based on intemal property measurement by computer monitoring, were also evaluated. Results show that more accurate control of the air circulation system is required with food waste composting systems. Temperatures in excess of 55°C were obtained during experimentation. A food waste to bulking agent ratio of 1:2 was determined to be best under these experimental conditions.