Effect of biochar addition and temperature on hydrogen production from the first phase of two-phase anaerobic digestion of carbohydrates food waste

This paper reports an experimental study of the effect of biochar addition and temperature on hydrogen production in the first phase of the two-phase anaerobic digestion (TPAD) of carbohydrates food waste. Anaerobic digestion (AD) experiments using white bread representing carbohydrate food wastes were conducted in bench scale 100 ml reactors. The cultures with biochar addition were placed in the reactors and incubated at different temperatures (18, 35, and 52 °C) over a period of 8 days. The biochar addition ratio was varied from 0 to 18.6 g l^-1. The daily volumetric hydrogen production was measured, and the cumulative yield (Y_H) and daily production rate (R_H) of hydrogen were calculated. Both biochar addition and temperature affected hydrogen production significantly. Y_H and maximum R_H increased as the biochar addition ratio increased from 0 to 10 g l^-1 then decreased as the biochar addition ratio further increased up to 18.6 g l^-1. At different temperatures, Y_H varied significantly, increasing from 846618 ml l^-1 at 18 °C to 1475 ± 653 ml l^-1 at 35 °C and dropped to 1149 ± 626 ml l^-1 at 52 °C. The maximum R_H also peaked at 35 °C, reaching 858 ± 657.1 ml l^-1 day^-1. The effect of biochar addition was more profound under mesophilic conditions. The results of this study confirmed the beneficial effect of biochar addition in hydrogen production of carbohydrate food waste in the TPAD process.