Synergy between feedstock gate fee and power-to-gas: An energy and economic analysis of renewable methane production in a biogas plant

Abstract Biogas is an instrument of synergy between responsible waste management and renewable energy production in the overall transition to sustainability. The aim of this research is to assess the integration of the power-to-gas concept into a food waste-based biogas plant with the goal to produce renewable methane. A robust optimisation was studied, using linear programming with the objective of minimising total costs, while considering the market price of electricity. The mathematical model was tested at an existing biogas power plant with the installed capacity of 1 MWel. It was determined that the integration of power-to-gas in this biogas plant requires the installation of ca. 18 MWel of wind and 9 MWel of photovoltaics, while importing an additional ca. 16 GWhel from the grid to produce 36 GWh of renewable methane. The economic analysis showed that the feedstock gate fee contributes significantly to the economic viability of renewable methane: a change in the feedstock gate fee by 100 €/tonne results in a decrease of production costs by ca. 20-60%. The robust nature of the model showed that uncertainties related to electricity production from wind and photovoltaics at the location increased the cost of gas production by ca. 10-30%.