Revealing the impact of hydrogen production-consumption loop against efficient hydrogen recovery in single chamber microbial electrolysis cells (MECs)

Microbial electrolysis for hydrogen production exhibited great advantages over many other biohydrogen production techniques in terms of hydrogen yield (HY) and energy efficiency (EE). With the elimination of methanogens, homoacetogens could thrive as the major hydrogen sink to impair HY and EE. However, the determination of hydrogen loss in microbial electrolysis cells (MECs) was rather controversial. In this study, we quantitatively investigated the negative impact of homoacetogens on hydrogen recovery in single chamber MECs. Hydrogen partial pressure (HPP) ranging from 0 to 40 kPa greatly affected the hydrogen consumption rate while acetate concentration ranging from 0 to 100 mM had little impact. HY base on consumed substrate was not significantly affected with less than 20 kPa HPP but decreased from 87% to 66% with 20-34 kPa HPP. And the EE based on input electricity was decreased from 160% to 48% accompanied with the increase of HPP from 7 to 34 kPa. Microbial community analysis revealed that Acetobacterium was the dominant homoacetogenic hydrogen scavenger in cathodic biofilm and planktonic cells in the single chamber MECs.