Energy recovery from commercial-scale composting as a novel waste management strategy

This study reports operational information from a commercial-scale Aerated Static Pile (ASP) composting system with energy recovery, one of the few currently in operation globally. A description of this innovative system is followed by operational data on energy capture efficiency for 17 experimental trials with variable compost vapor and heat sink temperatures. Energy capture was directly and predictably related to the differential between compost vapor and heat sink temperatures, with energy capture ranging from 17,700 to 32,940 kJ/h with a compost vapor temperature range of 51-66 degrees C. A 5-day temperature lag time existed between compost pile formation, and when compost vapor temperatures were sufficiently high for energy recovery >= 50 degrees C). The energy recovery system also exhibited a time lag between the initiation of aeration and when the vapor reaching the heat exchanger reached pile vapor temperature. Consequently, future ASP composting sites employing an energy recovery system may have to alter aeration system design and schedules to compensate for any type of heating-up phase that reduces energy recovery.