Flexible application of biogas upgrading membranes for hydrogen recycle in power-to-methane processes

Direct methanation of biogas converts the CO2 in raw-biogas to methane, enabling higher methane yield and an elelctricity storage option via Power-to-Gas. As the thermodynamic equilibrium limits the methane yield, unreacted hydrogen has to be removed and recycled to reach grid injection quality. We tested a commercial biogas upgrading membrane for hydrogen recycling at TRL 5. Based on the experi-ments, we developed a concept, which flexibly combines biogas upgrading and methanation post upgrading in a single unit. This allows switching between the two operation modes, which can improve the economic benefit of the system. The hollow fibre membrane module was tested simulating the methanation product gas (biomethane, 12% H-2 in CH4) and biogas (40% CO2 in CH4) in pressure ranges of 3-9 bar. In both cases, grid injection limitations (