Development of a decision support model for an investment in biogas-based plants in France and Germany

In Europe, the importance of the energetic independence, particularly in the gas sector, has been highlighted by the Russian invasion of Ukraine. National biomethane production offers a compelling option for substituting of natural gas, and France and Germany have been identified as having among the highest sustainable potential for producing biomethane via anaerobic digestion on their territory in Europe. To help a potential investor taking first investment decisions, an in-depth investigation of the energy context of both countries has reveal divergent approaches to biomethane production potential resources: Germany focuses on electricity generation from biogas and provides subsidies for power plants using biomass, whereas France provides subsidies for biomethane-producing plants. According to these findings, three key processes have been explored: biogas production in anaerobic biodigesters, biogas combustion for electricity generation through Combined Heat and Power engines, and finally, biogas upgrade through the Pressure Swing Adsorption technology. Production costs for these three processes have been modelled separately across a wide range of biogas flowrates to enable comparable production costs between biomethane producing plants and biogas power plants, from the same biogas quantities. Two approaches have been used to estimate the biodigester costs using data values from biomethane, and heat and power generation plant, respectively. The built costs models for biomethane and electricity production align with the values of subsidies offered by each country, helping to choose an optimal plant size accordingly. The optimal production costs for biomethane range according to biogas flowrates (540 and 915 Nm3/h) between 75.28 €/MWh and 83.28 €/MWh. For electricity production costs in Germany, both cost models show a decrease with increasing installed capacities, not providing an optimal size. Therefore, two lower bounds have been identified according to the subsidies provided in Germany, i.e. at 2.5 MW and 4.8 MW for 176.7 €/MWh and 198.3 €/MWh, respectively.