Succession of biochar in integrated pyrolysis, anaerobic digestion, and solid–state fermentation towards closed loop valorization of food waste

Multifunctional biochar (BC) promotes the advancement of microbial fermentation techniques in bioenergy and environmental remediation applications. This study explored the effects of shell waste BC on a closed loop of food waste via an integrated process involving Pleurotus ostreatus and biogas production and the improved mechanisms. Functional groups of BC adsorb harmful components, such as NH4+-N and Na+ in the anaerobic digestate residue (ADR) substrate, leading to a 51.3 % increase in mycelium growth rate. The addition of BC in the ADR substrate enhances the ability of the mycelium to degrade the substrate, and its porous structure helps retain moisture and reduce nutrient loss in the substrate. These factors could be significant contributors to the 16.46 % improvement in mushroom yield. Density functional theory provide insights into the potential mechanisms through which BC prevents the accumulation of heavy metals in fruiting bodies. BC improved methane yield in the anaerobic digestion of spent mushroom substrate by 47.53 %. The profit was SG$1.18/kg ADR due to low investment and high payback. These results provide new insights into nutrient and energy recovery from ADR via integrated processes (pyrolysis, anaerobic digestion, and solid–state fermentation) with BC.