A consolidated potential analysis of bio-methane and e-methane using two different methods for a medium-term renewable gas supply in Germany

Background: The German energy transition has entered a new phase and one important aspect is the question, to what degree the gas sector could be supplied with so-called “green” gases, i.e., gases from renewable sources. This paper focuses on the potential of domestic methane from biological origin (bio-CH₄) until 2030 that is estimated with two different methods. The comparison of the results provides a consolidated estimate. Methods: In a bottom-up approach, a GIS-based cluster analysis was undertaken to estimate the potential on bio-CH₄ from the existing cogeneration biogas plant (BP) stock. In a top-down approach a meta-analysis of GHG-reduction scenarios with respect to bio-CH₄ was performed. The meta-analysis was also extended to methane from renewable electricity (e-CH₄) since the BP stock may play a role in the provision of CO₂. Further, it included the year 2050 (the target year for most scenario studies) as well as issues like energy imports. Results: The bottom-up approach yields a potential of 24.9 TWh of bio-CH₄ for 2030. This is well within the range of the top-down analysis of 11–54 TWh (average: 32.5 TWh) for that year. In some scenarios values for e-CH₄ where considerably higher, especially with respect to 2050, but in these studies the sources—including the CO₂ sources—are either not explained at all or they are due to imports of e-CH₄ in combination with direct air capture (DAC) rather than biogenic sources. Concerning the regional dispersion, the bottom-up analysis shows that the largest potentials (53% or 905 of the biogas plants) are located in the northern part of Germany, more particular in Lower-Saxony, Schleswig-Holstein, Mecklenburg-Western Pomerania. These represent 54% or 602 MW of the installed capacity of the clusters. Conclusion: The consistency of the outcomes of the two methodologically very different approaches may be called the main result of this research. Therefore, it provides a consolidated analysis of the potential for domestic supply of bio-CH₄ in 2030. Furthermore, the amount corresponds to 2.7–3.5% of the German natural gas consumption in 2018. Taken bio-CH₄ and e-CH₄ together it corresponds to 7.2–8.0%.