Biogas till kraftvärme på Wapnö : en projektanalys utifrån ett företagsekonomiskt perspektiv

Abstract: Biogas is a gaseous fuel, rich in methane, produced through a biological route in an anaerobic digester. A gas engine generates combined heat and power, which can be used at the farm to reduce energy cost. The process also generates a digestate, with better utilization of nutrient compared to cattle manure. The aim of this study is to analyze the profitability of a farm-scale biogas plant for combined heat and power (CHP) at Wapnö. Wapnö is an agriculture company located in the southern part of Sweden. Today there are about 1000 dairy cows, 1600 hectare of farmland and a dairy plant. Nearly half of the farmland is organicly cultivated. The substrates for the digester are produced at Wapnö and are calculated to 30 000 ton of liquid manure, 300 ton of ley crops and 70 ton of milk. The method in this study is based on the Net Present Value model. An investment calculation has been made over 20 years. Three different areas have been analyzed; energy, cash crop farming, cost of labor and maintenance. The discounted sum from all areas has been compared with the total investment cost. The total investment cost for a turnkey biogas plant is calculated to 11, 6 '10 6 SEK. The internal rate of return is 2,7 percent when the heat is excluded. There are great opportunities to use the heat from the CHP for pasteurization of milk in the dairy plant. This would reduce the electricity costs and get a positive net present value. Including a 30 percent subsidy the investment generates a higher net present value and the modified pay-off period will be 10,3 years. The analysis also shows that the efficiency from the gas engine is important for the internal rate of return. If the efficiency of electricity production increases from 34 to 38 percent, the gas engine generates more electricity per year. This improvement in efficiency doubles the internal rate of return.