Hydrogen Gas Production from Waste Peach Pulp by Natural Microflora

Dark fermentative hydrogen gas production from waste peach pulp was studied without external microbial culture inoculation. First, most suitable pulp concentration for hydrogen production was determined in bench scale serum bottles then a 140 L pilot scale reactor was operated at most convenient pulp concentration. During the bench scale experiments the pulp concentration was varied between 3.42 and 170.80 g TS/L and the highest cumulative hydrogen volumes were obtained at 102.5 and 170.8 g TS/L, respectively. The initial pulp concentration of 34.16 g TS/L showed the best performance in terms of hydrogen formation yield (180 mL H₂/g COD) and rate (6.44 mL H₂/h). Hydrogen yield and rate increased up to 34.16 g TS/L due to substrate limitation. However, higher pulp concentrations resulted in substrate inhibition. This result was in accordance with the kinetic analysis where the substrate inhibition constant was determined as 43.86 g TS/L. The pilot scale reactor operated at optimum 34.16 g TS/L pulp concentration resulted in 323.67 mL H₂/g COD and 3900 mL H₂/h hydrogen formation, respectively. Our results demonstrated that waste peach pulp could be used both as substrate and inoculum source for hydrogen gas production when the initial substrate concentration is adjusted properly. Graphical Abstract: .