Research progress of biogas upgrading with external resource of hydrogen gas

Biogas fermentation has two general problems, low production rate and low methane concentration. From the reaction mechanism for methane formation, if external H₂ is supplied, CO₂ in the biogas can be converted into CH₄, leading to increased yield and concentration of methane. Recently published experimental studies reported that biogas could be purified and upgraded to a quality as biomethane with the addition of hydrogen gas. However, to make this technology practical, two key problems should be resolved. One is to intensify H₂ transfer from gas phase to aqueous phase at low mixing speeds. The other is to obtain hydrogen gas with economical methods. A scheme is suggested for biogas upgrading through the integration of H₂ generation by photoelectrocatalysis and CH₄ production by anaerobic fermentation.