The influence of mixing H2/CO2 gas recirculation on the performance of hydrogenotrophic methanogens activity in continuous culture was studied at 37 and 20°C. Chemostat fermentation was used at laboratory scale to determine the bioconversion rate of H2/CO2 mixture gas to methane under different mixing rates. On comparison with continuous mixing, intermittent mixing at 45 min/h provided a better methane production, 1.94 ± 0.06 versus 1.83 ± 0.05 L for continuous mixing. When the temperature was progressively decreased to 20°C, the same configuration was observed. The methane production was lowered from 76.2, 80.8, 67.5, 61.2 to 27.9, 35.8, 29.6 and 26.7% for 60, 45, 30 and 15 min/h, respectively. The mixing at 45 min/h showed a stable methane production as compared to all proposed mixing duration especially at psychrophilic temperature. The results would facilitate an empiric model that could help to establish more economical biogas reactor model.
Key words: Hydrogenotrophic methanogens, mixing, H2/CO2 gas, bioconversion, temperature fluctuation.