Study of effects of biochar particle sizes on anaerobic co digestion of fecal sludge and food waste

Abstract

The biochar addition to enhance anaerobic co-digestion (AD) of fecal sludge and food waste for methane production was investigated with a focus on biochar dosage and particle size of biochar. Optimal dosage range of biochar was determined as 5 - 20 g/l working volume based on lab-scale batch AD. Effects of biochar with different particle sizes at optimal dosage of 15 g/l were evaluated in a semi-continuous AD experiment, results of which showed that all the examined biochar’s with different particle sizes 0.075mm, 0.15mm and 0.45mm substantially enhanced the average methane yields (270ml/gVS, 241 ml/gVS and 222ml/gVS) compared to control digesters less than 200ml/gVS. The core reason for this phenomenon was that the biochar’s with different particle sizes had different properties i.e density, surface area and pore size and that the floating of large particle size of biochar was not conducive to microbial growth. Methane (CH4) in the biochar and control treatments were significantly different in all experiments. The results show that biochar added to digesters can significantly reduce H2S production with rising CH4 production.