Hydrogen gas production from waste paper by dark fermentation: Effects of initial substrate and biomass concentrations

In this study, waste paper was used as the raw material for hydrogen gas production by dark fermentation at different initial substrate and cell concentrations. Glucose obtained from acid hydrolyzed waste paper was used at six different concentrations between 3.84 and 45.5 gL−1 to determine the effects of sugar concentration on bio-hydrogen production. The highest cumulative hydrogen gas was obtained at 18.9 gL−1 initial sugar concentration. Sugar concentrations above 18.9 gL−1 resulted in product inhibition. Similarly, the initial biomass concentration was varied between 0.25 and 2 gL−1 while sugar concentration was kept constant at 18.58 ± 2.45 gL−1 to determine the effects of initial biomass concentration. The highest cumulative hydrogen gas production was obtained with the initial biomass concentration of 0.5 gL−1. The highest hydrogen yield (140 ml H2 g−1 total sugar) was observed at 3.84 gL−1 total sugar concentration. Hydrogen yield decreased with increasing initial sugar concentration due to inhibition by volatile fatty acids (VFAs) produced by dark fermentation and furan derivatives produced from acid hydrolysis of waste paper.