Continuous biohydrogen and biomethane production from whey permeate in a two-stage fermentation process



This study focuses on the exploitation of the two-stage continuous fermentation process for biohydrogen and biomethane production from whey permeate. Mesophilic fermentative biohydrogen production was investigated at a constant hydraulic retention time (HRT) of 24 h and organic loading rates (OLRs) of 20, 25, 30, and 35 kg COD/m3·d. The hydrogenogenic reactor was successfully operated at OLR of 30 kg COD/m3·d when the proportion of hydrogen in biogas, volumetric productionrsquo rate of hydrogen, and hydrogen yield reached the maximum values of 44.6 ± 0.8%, 5.26 ± 0.15 L H2/d, and 4.19 mol H2/kg CODremoved, respectively. The effluent from hydrogenogenic reactor was further digested to biogas in the second reactor operated at a HRT of 3 d and variable OLR in the range of 0.9–1.9 kg COD/m3·d. Maximum biogas production rate, volumetric production rate of methane and methane yield were 16.90 ± 0.6 L/d, 11.95 ± 0.6 L CH4/d, and 0.12 m3 CH4/kg CODadded. The total chemical oxygen demand elimination from whey permeate reached 98% in a two-stage process. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1411–1418, 2014