Enhancing bio-hydrogen production from food waste in single-stage hybrid dark-photo fermentation by addition of two waste materials (exhausted resin and biochar)

Bio-hydrogen production from organic wastes is considered as one of the most promising alternatives for sustainable, green energy production. In this study, the effect of addition of Ca- and Mg-saturated resin and phosphate-laden biochar on single-stage hybrid dark-photo hydrogen fermentation from food waste was investigated. In the first step, fermentation was performed using different amounts of Ca- and Mg-saturated resin ranging from 2.5 to 20 g l-1 to analyze the effect of released calcium and magnesium on both the H2 production rate and the system pH. The addition of 5 g l-1 saturated resin resulted in an increase of hydrogen yield from 101.60 ± 2.4 to 164.4 ± 2.6 ml H2g−1 VS, and at the same time it prevented pH drop and improved bacterial function. In the second step, 5 g l-1 saturated resin combined with various amounts of phosphate-laden biochar were added to the reactor. The maximum accumulated hydrogen production (3130 ± 16.8 ml) and hydrogen yield (197.15 ± 2.9 mlg−1VS) was observed when 5 g l-1 resin and 0.5 g l-1 biochar was used. This corresponds to 94% increase in the yield compared with the control. The analysis of the fermentation products indicated that butyrate and acetate were the major by-products during hydrogen production. Moreover, the optimum concentrations of resin and biochar served to facilitate substrate degradation and shorten the lag phase from 8.19 ± 0.4 to 4.79 ± 0.5 h. Thus, the application of Ca- and Mg-saturated resin and phosphate-laden biochar in a single-stage hybrid dark-photo fermentation process enhanced the efficiency of the conversion of organic waste to hydrogen while maintaining the stability of the process. •Synergic application of resin and biochar increased H2 yield by 94%.•Synergic application of resin and biochar shorten the lag phase by 41.5%.•Phosphate-laden biochar played a buffering role due to having buffering compounds.•Biochar promoted bacterial adhesive growth due to its high porous structure.•Exhausted resin provided nutrients for bacteria via gradual release of Ca and Mg.