Anaerobic Digestion of Food Waste with the Addition of Biochar Derived from Microwave Catalytic Pyrolysis of Solid Digestate

This study explores the potential of biochar derived from microwave-assisted catalytic pyrolysis of solid digestate as an additive to enhance the stability and performance of the anaerobic digestion process. The focus was placed on the effects of biochar dosage, pyrolysis temperature, and pyrolysis catalyst on methane production. Biochemical methane potential (BMP) tests using synthetic food waste as the substrate revealed a dosage-dependent relationship with specific methane yield (SMY). At a low biochar dosage of 0.1 g/g total solids (TS), improvement in methane (CH4) production was marginal, whereas a high dosage of 0.6 g/g TS increased CH4 content by at least 10% and improved yield by 35–52%. ANOVA analysis indicated that biochar dosage level significantly influenced CH4 yield, while pyrolysis temperature (400 °C vs. 500 °C) and catalyst (20 wt% K3PO4 vs. 10 wt% K3PO4/10 wt% clinoptilolite) did not lead to significant differences in CH4 yield between the treatments. Correlation analysis results suggested that biochar’s most impactful properties on methane yield would be dosage-adjusted specific surface area (or total surface area per unit volume of substrate) and aromaticity index. The findings underscore the potential of solid-digestate-derived biochar as a beneficial additive for anaerobic digestion and hence the sustainability of food waste management system.