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

Abstract

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.