Biocycle anaerobic digester: performance and benefits

The Biocycle digester in South Shropshire, UK was monitored over a period of 14 months. During this time, the type, source and quantity of input biowastes were analysed and their physical and chemical properties were determined, including quantification of heavy metals content. The source-segregated waste was found to be a rich source of energy and was readily biodegradable, producing a biogas with ~60% methane. The process had a very favourable energy balance with around 400 kWh of energy recoverable from each tonne of waste processed. Although the available heat energy was not utilised, over 620 MWh of the electricity produced was exported to the grid during the study period. An energy balance for the process included the transport and application of the digestate to farmland. 3936 t wet weight of wastes were processed during the study period and over 90% of this mass could be accounted for in the gaseous and digestion products. The environmental benefits and risks of the process are considered in terms of the carbon savings and losses that may result through adoption of this technology.