COMBINED HEAT AND POWER GENERATION FROM BIOGAS USING FARM BASED BIOMASS

This paper reports on the performance of a 23 kW electrical combined heat and power (CHP) unit fuelled on biogas over a period of 50 months. Biogas produced by the farm scale anaerobic digester operated firstly on cattle slurry only and then on series of co-digestion trials with grass silage at increasing quantities. In the first trial period dairy cattle slurry was fed exclusively to the digester for a period of 27 months. The 23kW electrical CHP was operated for 26,283 engine hours. During this period average daily productions of electricity and heat were 450 and 873 kWh respectively at an overall efficiency for biogas energy use of 76% (26% for electricity production). The ratio of revenue from Renewable Obligation Certificates and electricity savings to running costs of the CHP over the period was approximately 5.0 to 1.0. These data are presented in detail along with preliminary data from a 95 kW electrical CHP which replaced the 23kW electrical unit.