Enhanced biohydrogen production from palm oil mill effluent using single-stage process of dark fermentation and microbial electrolysis cell at various initial pHs

One of the potential organic wastes to be utilized as biohydrogen feedstock is palm oil mill effluent (POME). The current research aimed to investigate the impact of initial pH levels on biohydrogen generation from POME using a single-stage process of dark fermentation (DF) and microbial electrolysis cell (MEC), called sDFMEC. Initial pH values of 3.9, 6.0, and 7.0 yielded 2.40, 39.84, and 27.32 mL-H2/g-SCOD through DF alone, and 6.91, 83.39, and 31.47 mL-H2/g-SCOD through sDFMEC, respectively. Hence, the optimal initial pH was 6.0. The incorporation of MEC into DF enhanced the volatile fatty acids (VFAs) production rate 1.9 times compared to DF alone. Based on the microbial community analysis, the family of Clostridiaceae and Enterobacteriaceae were primarily responsible for biohydrogen production in the sDFMEC process. The number of the amplicon sequence variants of those bacteria families enhanced in the sDFMEC (18.76 % and 9.59 %), compared to DF alone (12.13 % and 5.31 %). It is expected that the findings of the current study can be utilized as a basis for studying the sDFMEC process on a larger scale at other affecting factors.