Enhancement of water hyacinth juice treatment in an anaerobic sequential batch reactor with coffee husk–derived biochar

Abstract

Abstract Anaerobic digestion of compressed water hyacinth juice (WHJ) is one of the appropriate ways to enhance excessively grown water hyacinths. The addition of biofilm carriers is effective in enhancing digestibility as they can retain microorganisms at a high density in the digester. This study evaluated the anaerobic digestion performance in a sequential batch reactor in the presence of a natural carrier, biochar from coffee husks which are representative agricultural waste in areas where water hyacinths are thriving, compared to those with a commonly used carrier (polyurethane sponge) and without a carrier. In the biochar-filled condition, the CH4 production was 471 mL g-VS− 1 and the total organic carbon (TOC) removal efficiency was 88.6%. In contrast, in the no-carrier condition, the CH4 production decreased and the TOC removal efficiency dropped to 54.5%. The porosity of the biochar promoted microbial attachment and biofilm formation. Candidatus Diapherotrites archaeon ADurb.Bin253, which belongs to the symbiotic archaeon Nanoarchaeaeota, was detected in all reactors, suggesting that it contributed to the organic decomposition. The performance of the biochar was comparable to that of the sponge carrier, indicating that the coffee husk–derived biochar can be considered a sustainable and useful carrier for enhancing the anaerobic digestion of WHJ.