Abstract A successful transition towards a cleaner and more sustainable energy management in 2050 requires the implementation of renewable energy sources on a large scale. Therefore, it is expected that the share of renewable energy will further increase. Due to the introduction of these intermittent energy sources, the need for flexibility in our energy system increases significantly. Power-to-gas (P2G) is one promising option for providing long term energy storage and for providing flexibility to the electricity system. An interesting, recent technological development is biological methanation. The latter utilizes microorganisms to catalyze the Sabatier reaction. This biological reaction can be achieved at lower temperatures and pressures than when a chemical catalyst is used and has a higher tolerance to contaminations from the CO2 source, process upset or contamination by foreign organisms. We investigate the techno-economic potential of biological methanation (i.e. microbial power-to-gas concept) using a case study that revolves around anaerobic digestion using mainly municipal organic waste in Belgium. The most important parameters that influence the economic feasibility are the electricity consumption (44%), operating hours of the electrolyser (14%), and the investment cost of the electrolyser (14%). Based on our findings we offer further routes of research that serve to strengthen the business case.