Energy analysis of farm-based biogas plants in Sweden

Abstract: It is projected that energy demand worldwide will double from 2009 until 2050. There is a demand for additional clean renewable energy, which can be supplied by biogas. Farm-based biogas plants exist in small numbers in Sweden; for the benefit of society it important to increase their numbers throughout the country. The aim of this report is to create the tools to allow for a competent evaluation of newly built farm-based biogas plants from an energy efficiency and environmental perspective. In this thesis data from newly built plants has been analyzed to determine mistakes that could be avoided in future expansion. Research has been performed within the bounds of a SLF financed project focusing on the role of cooperation in achieving profitability and environmental benefits in farm based biogas plants. The thesis has found that the investment cost during the technical lifetime of the plant is 11-16 kWh/MWh and 2.65 – 3.65 kg CO2-eq. per MWh. The initial investment is repaid by a factor of at least 50 during the technical lifetime of the plant. Energy ratios have been calculated for two of the plants that express the usable energy produced from each. It has been found that 29 % of Högryd’s 2 GWh in energy production becomes usable electricity and heat; at Lövsta 62 % of its 10 GWh became usable electricity and heat. A larger biogas plant benefits from a higher electrical efficiency, however, the impact of the heat utilization is significant. Replacement of 120 MWh of oil and electricity reduces the import of fossil-fuels more than 1.5 GWh of wood chips.