Hydrogen production from sugar beet juice using an integrated biohydrogen process of dark fermentation and microbial electrolysis cell

•Integrated dark fermentation and microbial electrolysis cell was evaluated.•Hydrogen yield of 3.2 mol H2/mol hexoseadded was achieved in dark fermentation.•Low PH2 (8 × 10−5–1 × 10−3 atm) is essential to utilize propionate and butyrate in MECs.•Overall H2 yield of 6 mol H2/mol hexoseadded was achieved in the integrated system.•Overall energy recovery of 57% was achieved in the integrated process.

An integrated dark fermentation and microbial electrochemical cell (MEC) process was evaluated for hydrogen production from sugar beet juice. Different substrate to inoculum (S/X) ratios were tested for dark fermentation, and the maximum hydrogen yield was 13% of initial COD at the S/X ratio of 2 and 4 for dark fermentation. Hydrogen yield was 12% of initial COD in the MEC using fermentation liquid end products as substrate, and butyrate only accumulated in the MEC. The overall hydrogen production from the integrated biohydrogen process was 25% of initial COD (equivalent to 6 mol H2/mol hexoseadded), and the energy recovery from sugar beet juice was 57% using the combined biohydrogen.

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