The daily and seasonal fluctuations in renewable energies, especially in the use of wind and solar energy, pose a particular challenge for the future of energy supply in Germany. This results in the need to develop intelligent solutions for the conversion and storage of energy. This is where the present research project comes in, by creating opportunities to combine the surpluses from wind and solar power plants with the CO2 production of biogas plants in order to produce storable energy in the form of methane. With the help of the well-developed natural gas network in Germany, this can be stored in the long term and used as required.

The aim of this research project is to develop a high-performance methane reactor for the biosynthesis of methane from CO2 and hydrogen. In contrast to current research and demonstration projects, which carry out technical methane synthesis, production takes place using special methane-forming microorganisms in a bioreactor. Particularly efficient mesophilic, thermophilic and hyperthermophilic methanogenic archaea are used, which are characterized by high conversion rates and short generation times. The CO2 source for methanogenesis is initially the CO2 waste gas stream from biomethane plants and later also CO2 from industrial plants. Since methanogenic bacteria have no end product inhibition, unpurified biogas can also be used as a CO2 source. Compared to the process of technical methane synthesis, microbial biosynthesis offers various advantages. For example, biological methane formation from CO2 and H2 has a high energy efficiency of over 80 %. Taking into account the efficiency of electrolysis (≥ 80 %), an overall efficiency of around 65 % can be achieved. In contrast, today’s technical processes achieve a maximum overall efficiency of 60 %. Another key advantage of biological methane synthesis is its insensitivity to impurities in the source gases. For example, methanogenic archaebacteria have a high tolerance to hydrogen sulphide, carbon monoxide, nitrogen oxides and other trace and secondary components. Catalyst-dependent (usually nickel catalysts) technical methane synthesis, on the other hand, requires a high degree of purity of the starting gases and correspondingly complex upstream gas purification.