Pilot-scale biomethanation of cattle manure using dense membranes

This study aimed at studying the biomethanation process using a 100 L pilot-scale digester equipped with a dense membrane for hydrogen injection. Hydrogen mass transfer was characterized and the impact of hydrogen flowrate, agitation rate and of the co-injection of CO₂, on biogas production and composition, was precisely studied. A linear relationship between H₂ flowrate and the CO₂ and CH₄ rates in biogas was found but no impact on biogas flowrate was shown. It was also noticed that, without exogenous CO₂ injection, and for high H₂ injection flowrates, residual H₂ could be found at the digester outlet due to local CO₂ limitation. Thus, this study suggested that biogas production in biomethanation process at the pilot scale was probably rather limited by the dissolved CO₂ transport within the liquid phase than by the hydrogen mass transfer itself.