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Tunnel composting

Tunnel composting is an accelerated composting technology which uses forced aeration to process food, garden waste and other types of waste into compost. After organic waste is trucked into the facility, a shredder tears opens bags to access organics. This waste is then combined with inoculants, pre-composted material collected from previous composting cycles to begin process. The Surrey Biofuel facility also mixes fresh waste with digestate, the material remaining after the anaerobic process used to create biogas as well as inoculants to begin process. The mix is spread across air-tight composting tunnels for 7 to 10 days where forced air kick-starts the biological process and compost reaches temperatures of 55°C or higher, killing harmful bacteria. Next, the mix is removed from tunnels and processed through a screening line, to remove contaminants and heavy solids; separating out waste, mid-fraction and compost. The compost is stored and inspected in accordance with provincial regulations: a sample is taken and analyzed by external laboratory that is an affiliate of the Compost Council of Canada and tested under Compost Quality Alliance guidelines.