Effect of Biochar Addition and Initial pH on Hydrogen Production from the First Phase of Two-Phase Anaerobic Digestion of Carbohydrates Food Waste

This paper reports the effect of biochar addition and initial pH on hydrogen production in the first phase of the two-phase anaerobic digestion (TPAD) of carbohydrates food waste. Bench-scale experiments were conducted in 100 ml serum bottles with initial pH set at 4, 6, 8, respectively, and biochar addition ratios of 0, 1.2, 5, 10, 15 and 18.6 g.l^-1. The cultures were incubated at 35°C for eight days. Gas composition and volumetric production were measured daily using a gas chromatograph and a water displacement method, respectively. Daily hydrogen production rate (HPR) and cumulative hydrogen yields (HY) were calculated. The results show that in cultures without biochar, both the maximum HPR and HY achieved the highest at pH 6, being 651±7 ml.l^-1.day^-1 and 1044±19 ml.l^-1, respectively The addition of biochar significantly improved HPR by up to 26% and HY by up to 41%. The addition of 10 g.l^-1 biochar at initial pH 6 achieved the highest HPR (820.6±81 ml.l^-1.per day) and HY (1475±53 ml.l^-1). Biochar addition was experimentally proven to be beneficial in hydrogen production of carbohydrates food waste in the first phase of TPAD.