Application of biochar for enhancing methane production and alleviating sulfide toxicity in skim latex wastewater with minimized roles of biochar as a carbon source

BACKGROUND: The conversion of organic matter in sulfate-rich wastewater to methane presents a significant challenge due to the competition between methanogenesis and sulfidogenesis. In this study, we investigated the potential of Earleaf acaciabased biochar (EA-biochar) to enhance methane production and alleviate sulfide toxicity in skim latex wastewater (SLW). The role of biochar as an extra carbon source was minimized by washing it three times before use. Anaerobic digestion of SLW was investigated under both batch and fed-batch operational modes.
RESULTS: The methane yield of the batch with EA-biochar addition was 252.85 ± 5.37 mL g−1 COD, significantly higher than that of the batch without EA-biochar (192.93 ± 5.52 mL g−1 COD). In addition, the methane production rate of the batch with EA-biochar was 25% higher than that of the batch without EA-biochar addition. The increased methane yield was correlated with lower levels of volatile fatty acids and total organic carbon in the media, highlighting the role of EA-biochar in mediating electron transfer for methanogenesis rather than providing additional carbon sources.
CONCLUSION: The results from the fed-batch operation were consistent with those from the batch operation, indicating that the biochar effectively promoted methanogenesis for at least 80 days.