Development of a CO₂-biomethanation reactor for producing methane from green H₂

"Power-to-Methane" approaches allow the storage and transport of green methane, produced from renewable energy and any CO2 source. In nature, some microorganisms, namely methanogens, can grow on CO2 and H-2 and produce pure methane via an ancestral process, the methanogenesis, under mild conditions (temperature, pressure, aqueous solvents. . .). These microorganisms are able to perform efficiently the Sabatier reaction (4H(2) + CO2 -> CH4 + 2H(2)O), using H-2 and CO2 as sole energy and carbon sources. Here, we developed a biomethanation reactor to culitvate a pure culture of Methanococcus maripaludis, a mesophilic methanogen growing rapidly at ambient temperature. A modular scalable and frugal 2 L-bubble column bioreactor was constructed to operate efficiently and autonomously for several weeks under a wide range of conditions. High H-2 conversion and methane yield higher than 90% could be reached. This high-performance, modular and robust bioreactor shows its potential for integration in outdoor systems coupling the conversion of alternative sources of green H-2 to fossil-free methane.