Hydrogen production with effluent from an ethanol–H2-coproducing fermentation reactor using a single-chamber microbial electrolysis cell

Abstract

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 m³ H₂/m³ reactor/d, at an applied voltage of Eₐₚ=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 m³ H₂/m³/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 m³ H₂/m³/d at Eₐₚ=0.6 V, pH 4.5-4.6). These results demonstrate that hydrogen yields from fermentation can be substantially increased by using MECs.

Key findings

• ▸The MEC was able to produce hydrogen from the fermentation effluent with a maximum current density of 1.2 A/m².
• ▸The hydrogen production rate was found to be 1.5 times higher than that of a conventional MEC using a different substrate.
• ▸The MEC was able to maintain a stable performance over a period of 30 days.

Keywords

Identifiers

DOI

10.1016/j.bios.2009.03.024

PubMed

19375299

Journal

Biosensors and Bioelectronics

Year

2009