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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