Biogas in Sweden - Opportunities and challenges from a systems perspective

Addressing today’s challenges of reducing our dependence on fossil fuels and related emissions of greenhouse gases requires measures such as increased energy efficiency and replacement of fossil energy carriers with renewable ones. Biogas is one of the fastest growing renewable energy sources in the world and the overarching purpose of the research presented in this doctoral thesis is to explore the prospects of an increased production and utilization of biogas in a Swedish context. Biogas can be produced from various kinds of organic material such as municipal and industrial waste, which dominate the current production. This is driven by existing policy incentives, which also promote the use of biogas as vehicle fuel. However, the lion’s share of the Swedish biogas potential remains essentially untapped within the agricultural sector, including feedstock such as manure, crop residues and dedicated biogas crops. If fully utilized, biogas from wastes and residues only could replace 10% of the vehicle fuels or 50% of the natural gas used in Sweden today. This implies that existing incentives must be strengthened to overcome today’s barriers, especially regarding the limited profitability in biogas production based on agricultural feedstock as identified in this thesis. In addition, the techno-economic performance needs to be improved, for example by reduced feedstock costs and increased methane yields. For low-cost feedstock, such as manure, measures to reduce the cost of capital and the related cost of operation and maintenance are especially important. In the environmental assessment presented in this thesis, it was found that biogas produced in an existing, representative co-digestion plant, reduced emissions of greenhouse gases by approximately 90% when replacing fossil vehicle fuels. Based on the current structure of the Swedish energy system, the replacement of fossil vehicle fuels with biogas would normally render the highest reduction of greenhouse gas emissions, followed by the replacement of natural gas and other fossil energy carriers, indicating that these utilization options should be prioritized. However, given the additional greenhouse gas benefits of biogas produced from manure, regardless of how the biogas is utilized, such production should also be promoted. In conclusion, the overall findings in this thesis show that there are substantial opportunities to increase the production and utilization of biogas in Sweden, which would reduce greenhouse gas emissions significantly. However, current challenges, including the limited profitability in biogas production based on agricultural feedstock, should be met by further technology development combined with adequate and focused policy instruments