Assessing the Power-to-Gas potential: GIS-based suitability analysis of biogas plant sites in Lower Saxony, Germany

Abstract Background To decarbonise the energy system, offsetting fluctuations in renewable energy (RE) sources is crucial, for which biogas plants are well-suited. In Lower Saxony, Germany, the impending expiration of the 20-year Renewable Energy Sources Act subsidy for numerous biogas plants creates an opportunity to transition them to biomethane production within a Power-to-Gas (P2G) framework. However, detailed data on the suitability of these sites for conversion is lacking due to diverse site-specific conditions. Therefore, mapping the P2G potential of these sites is essential, paying particular attention to agricultural and environmental compatibility. Methods A multi-parametric Geographic Information System-based spatial analysis was conducted to assess the suitability of individual biogas plant sites in Lower Saxony for implementing methanisation with green hydrogen. Biogas plant sites were evaluated based on five criteria. The regional RE potential for wind turbines and ground-mounted photovoltaic systems and the installed electrical power of biogas plants criteria had to be met for the suitability of a biogas plant site. Additionally, water withdrawal conditions , biogas substrate use , and distance to the gas grid were evaluated as further sustainability criteria, considering the environmental impact. Results The spatial analysis showed that about 60% were suitable as environmentally friendly P2G sites since they met all the criteria. Concentrations of suitable biogas plant sites were found in western Lower Saxony, from the Emsland to the Diepholz district, and the Rotenburg (Wümme) district, as well as in the northern part of the Heidekreis in north-central Lower Saxony and the southern part of the Celle district near Hanover. Approximately 12% of biogas plant sites were considered conditionally suitable because they only met the essential criteria. Conclusions The criteria-based spatial suitability analysis enables comprehensive mapping of the potential for P2G at existing biogas plant sites in Lower Saxony. We identified 1,014 suitable sites for environmentally friendly implementation of methanisation with green hydrogen as an end-of-subsidy strategy. Considering agricultural and nature conservation compatibility can reduce land-use conflicts, promoting broader acceptance of the RE transition. These findings provide an advisory resource for stakeholders, highlighting the urgent need for action as the Renewable Energy Sources Act subsidy period comes to an end.