Performance of a prefabricated concrete tower composter

The study looked at the performance of a three-level composting tower, each level of which could take around 200 t of shredded mixed municipal solid waste. The composting material moved sequentially down through the three floors, taking 8–10 days to complete the cycle, targeting an Animal By-Products Regulations (ABPR) compliance regime of 70°C for 1 h. Using a 16 mm trommel screen, the yield of compost-like output (CLO) was typically 25–30% of the input by weight. The post-composting separation plant was found to be very effective in giving a range of other products for recycling. An energy usage estimate for the tower alone (not including shredding or post-compost separation) showed consumption between 25 and 31 kWh per tonne of input. Detailed temperature measurements using 40 dataloggers in a batch of 200 t of material showed that the towers were not achieving ABPR compliance standards. Modifications to the towers, which included recirculating warm air from the top of the composting mass and auxiliary...