Food waste derived biochar via pyrolysis: Properties, contaminant sequestration mechanisms, and environmental applications

The novel technique of biochar production from food waste (FW) through pyrolysis is a proactive step towards materialising the circular economy. This review provide a detail insights on the successful utilisation of FW for biochar production and its subsequent environmental applications, along with efficiencies and mechanisms in the removal of various pollutants from wastewater. The chemical transformation during FW pyrolysis assists the resultant biochar with unique physiochemical characteristics, including structure formation, porosity, alkalinity, functional groups, polarity, cation exchange capacity and carbon structure that contribute to the efficient removal of pollutants. Based on the organic-rich nature, detailed discussions have been made on how FW could be an ideal feedstock for pyrolysis as compared to other bio-waste. Moreover, the impacts of pyrolysis temperatures on the characteristics, variations in the removal efficiencies and interactions of biochar with pollutants have been discussed. The suitability of FW biochar for environmental applications is its stability for subsequent usage without losing activity and production of secondary pollutants or by-products, as compared to other technologies. However, despite the promising benefits, FW to biochar technology is still in infancy and prone to several challenges, including scalability due to intrinsic heterogeneity, high moisture that sometimes requires an additional step of drying and grinding and variations in the physicochemical characteristics that impact the economic feasibility, scalability and end-use marketability. Hence, detailed studies on techno-economic analysis in integration with advances in FW to biochar production, applications as adsorbent, stability, and reusability after treatment to fully explore the comparison with other available similar materials.