Circular utilization of food waste to biochar enhances thermophilic co-digestion performance

Codigestion is an emerging approach to improve wastewater sludge biogas production and valorize food waste (FW). This study explores FW-derived biochar as a codigestion amendment for the first time and reports a matrix experiment using four diverse biochar amendments (mixed food waste, pinewood, bonechar, unamended control) across four FW types (vegetable, rice, chicken, mixed). It demonstrated that biochar derived from mixed FW can greatly improve the performance of biogas production and yield relative to unamended control and other biochars. The mixed food waste (MFW) biochar amendment led to 34.5%, 35.6%, and 47.5% increase in methane production from mixed FW compared to biochars made of wood, bone and non-amendment control, and the maximum methane production rate of MFW biochar reactors could be up to 6.7–9.9 times of the control. These results suggest that a more circular utilization of FW by integrating biochar production with codigestion can bring great benefits to FW management.