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

Abstract

“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 H₂ 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 (4H₂ + CO₂ → CH₄ + 2H₂O), using H₂ 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 H₂ 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 H₂ to fossil-free methane.