Kinetic study on fermentation from CO 2 and H 2 using the acclimated-methanogen in batch culture

Abstract

Methane was produced from H 2 and CO 2 using the acclimated-mixed methanogens in a 3.71 fermentor in batch culture at pH 7.2 and 37°C. The Fermentation kinetics parameter for the growth of methanogens, overall mass transfer coefficient of the reactor, and the conversion rate of H 2 and CO 2 to CH 4 by the acclimated-mixed culture were determined using the technique of Vega et al. The maximum specific growth rate ( μ max) and H 2 specific consumption rate ( q max) were found to be 0.064(h −1) and 104.8 (mmol h −1 g −1) respectively. Monod saturation constants for growth ( Kp) and for inhibition ( K′ p) were found to be 3.54 (kPa) and 0.57 (kPa), respectively. These findings indicate that without very low dissolved H 2 levels, the fermentations are carried out under μ max, and the specific uptake rate ( q) was almost not affected at any dissolved H 2 level in the range studied. The yield of CH 4 (Yp/s) was calculated to be 0.245 (mol CH 4 mol −1 H 2), which is near the stoichiometric value of 0.25. DH 2 was also measured using the Teflon tubing method and was in good agreement with those estimated by kinetic calculations.