Optimizing biohydrogen production for dark fermentation of food waste in an anaerobic sequencing batch reactor (ASBR): Effects of hydraulic retention time

The investigation into the continuous biohydrogen production from food waste was conducted through the application of an anaerobic sequencing batch reactor (ASBR). The ASBR was operated under an operational pH of 5.5 and mesophilic temperature range. The feasibility of continuous hydrogen fermentation within the ASBR was assessed by employing various hydraulic retention times (HRT) of 72, 48, 36, and 24 h. An HRT of 36 h emerged as the optimal condition for ASBR operation, evidenced by the maximum hydrogen yield of 14.9 mL g CODadded-1. Biohydrogen effectiveness corresponded to an increased butyrate concentration and a reduced level of propionate. The concentration of propionate demonstrated a significant reduction when the HRT was adjusted from 72 h to 48 h and subsequently to 36 h. In contrast, a significant increase was noted at reduced HRT of 24 h, which subsequently led to a decreased hydrogen yield. The butyrate to propionate ratio (HBu/HPr) attained a value of 54.0 at the 36-h HRT, which is considerably higher in comparison to the others. The hydrogen gas content within the biogas produced ranged from 32.2% to 42.1%, exhibiting an increase as the HRTs decreased from 72 h to 36 h.