Biochar-amended food waste compost: A review of properties

The attention towards managing food waste (FW) and transforming it into compost has significantly increased in recent years, driven by the potential advantages it offers for sustainable agriculture and waste reduction. Biochar, a carbon-rich amendment derived from biomass through pyrolysis, has gained significant attention due to its potential benefits to enhance compost quality. This systematic review analyzed 11 studies to assess the role of biochar in optimizing FW composting. Studies revealed several benefits of biochar addition, including shortening of the time to reach the thermophilic stage and an increase in composting temperature. Biochar also improved compost quality by maintaining nitrogen content, reducing ammonia emissions, and promoting a favorable pH for microbial activities. Its porous structure created a suitable habitat for microbes, potentially accelerating organic matter degradation. Additionally, biochar's high cation exchange capacity (CEC) helped immobilize potentially toxic metals, reducing their availability in the final compost. However, our knowledge of biochar's benefits in improving compost quality remains incomplete. The reviewed studies neglected to evaluate the microbial quality of the resulting compost and the cost-effectiveness of biochar application. Future research should prioritize long-term studies to assess plant uptake from soils amended with biochar. Additionally, investigations into the optimal biochar-to-compost ratio, as well as the most effective timing and methods for land application, should be undertaken. Addressing these knowledge gaps is crucial for optimizing the utilization of biochar in FW composting, thereby leading to sustainable waste management practices and enhanced soil fertility. • Biochar speeds up composting and enhances final compost quality • Biochar addition significantly increased composting temperature • Biochar immobilizes heavy metals, reducing their presence in the final compost