Potato waste as feedstock to produce biohydrogen and organic acids: A comparison of acid and alkaline pretreatments using response surface methodology

Abstract

The effects of physicochemical pre-treatment were evaluated on hydrogen (H2) production and organic acids from hydrolyzed potato peel. Central composite design (CCD) and response surface methodology (RSM) were used to evaluate the effects of different substrate concentrations on a wet basis (38.8–81.2 g.L−1) and hydrolyser ratios (6M NaOH and 30% HCl: 1.6–4.4% v.v−1; and H2SO4: 2.2–7.8% v.v−1). The experiments were conducted in batch reactors at 37 °C, using a heat-treated microbial consortium. The maximum H2 production potential (P), lag phase (λ), and maximum H2 production rate (Rm) were evaluated for untreated and pre-treated potato peel waste. H2 production was positively influenced under hydrolyzed substrate concentrations ≥75 g.L−1 in the three CCDs performed. Only the increase in the H2SO4 proportions (≥5% v.v−1) had a negative influence on H2 production. Increasing the 30% HCl and 6M NaOH proportions did not significantly influence the cumulative H2 production. The highest hydrogen production was obtained after alkaline pre-treatment by dark fermentation (P: 762.09 mL H2.L−1; λ: 14.56 h; Rm: 38.39 mL H2.L−1.h−1). Based on the CCD and RSM, the highest H2 production (1060.10 mL H2.L−1) was observed with 81.2 g.L−1 hydrolyzed potato peel with 3.0% v.v−1 of 6M NaOH. The highest yield liquid metabolites were acetic (513.70 mg. g−1 COD) and butyric acids (491.90 mg. g−1 COD).