Hydrogen production with effluent from an ethanol-H2-coproducing fermentation reactor using a single-chamber microbial electrolysis cell.
Hydrogen can be produced by bacterial fermentation of sugars, but substrate conversion to hydrogen is incomplete. Using a single-chamber microbial electrolysis cell (MEC), we show that additional hydrogen can be produced from the effluent of an ethanol-type dark-fermentation reactor. An overall hydrogen recovery of 83+/-4% was obtained using a buffered effluent (pH 6.7-7.0), with a hydrogen production rate of 1.41+/-0.08 m(3) H(2)/m(3) reactor/d, at an applied voltage of E(ap)=0.6 V. When the MEC was combined with the fermentation system, the overall hydrogen recovery was 96%, with a production rate of 2.11 m(3) H(2)/m(3)/d, corresponding to an electrical energy efficiency of 287%. High cathodic hydrogen recoveries (70+/-5% to 94+/-4%) were obtained at applied voltages of 0.5-0.8 V due to shorter cycle times, and repression of methanogen growth through exposure of the cathode to air after each cycle. Addition of a buffer to the fermentation effluent was critical to MEC performance as there was little hydrogen production using unbuffered effluent (0.0372 m(3) H(2)/m(3)/d at E(ap)=0.6 V, pH 4.5-4.6). These results demonstrate that hydrogen yields from fermentation can be substantially increased by using MECs.
Lu
Lu
L
State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
Ren
Nanqi
N
Xing
Defeng
D
Logan
Bruce E
BE
D000085:Acetates / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D003624:Darkness; D004572:Electrolysis; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics
D000085:Acetates; D000431:Ethanol; D006859:Hydrogen