Fig. 3From: Conversion of H2 and CO2 to CH4 and acetate in fed-batch biogas reactors by mixed biogas community: a novel route for the power-to-gas conceptLevels of volatile organic acids in the reactors at the beginning (0 weeks = inoculum and after week 1 and week 4), respectively. The reactors received daily injections of H2 gas: 0.0 (green), 0.79 (red), 1.57 (black), and 2.36 (blue)Back to article page