Effect of biochar addition on biogas production using konjac waste through mesophilic two-phase anaerobic digestion

Purpose: This study aimed to investigate the influence of biochar supplementation in the mesophilic two-phase anaerobic digestion process for konjac waste. Methods: Reactors with a working volume of 60 mL were utilised to incubate cultures containing biochar. In the first phase, the cultures were maintained at 32 °C and a pH of 5 to facilitate the production of hydrogen. In the second phase, the cultures were adjusted to 37 °C and a pH of 7 to promote methane production. The concentration of konjac flour waste varied between 0 and 500 g/L, while the ratio of biochar addition ranged from 0 to 25 g/L. Biogas production was measured daily using the volume displacement method, and the pH of the cultures was monitored both before and after the experiment. Results: The findings show that using biochar has a beneficial effect on biogas production from konjac flour waste. During the initial phase of the experiment, incorporating biochar with a concentration of 15 g/L led to substantial improvements, elevating the maximum H2 production rates by 9.6%. Furthermore, the addition of biochar led to an 84% increase in H2 yield during the initial phase. Similarly, in the second phase, introducing biochar with a concentration of 15 g/L resulted in a 22.2% increase in the maximum CH4 production rates and a 2.5 times increase in CH4 yield. Conclusions: Overall, this work confirms the beneficial effects of biochar on the H2 and CH4 production from konjac flour waste using the mesophilic two-phase anaerobic digestion method for sustainable energy.