Sustainable valorisation of food waste into engineered biochars for CO₂ capture towards a circular economy

The large amount of food waste generated worldwidely has significant adverse environmental impacts to our entire ecosystem, highlighting the urgent need for a historic resolution to achieve sustainable managment of food waste as well as its circular economy. In this regard, preparation of engineered biochars from food waste has garnered significant attention for CO2 capture, as this upcycling potential could play a significant role in advancing the concept of a negative carbon circular economy. Hence, this review holistically explores the potential of food waste-derived engineered biochars as CO2 adsorbents, not only from sample-level to process-level CO2 adsorption, but also from a life-cycle perspective. Sample-level CO2 adsorption is examined in terms of synthetic methods and procedures, focusing on application and optimisation of carbonisation, activation, and surface modification processes. The application of machine learning for guiding syntheses of high-performance CO2 adsorbents derived from food waste is also dicussed. Process-level CO2 adsorption is examined in terms of two primary cycling configurations, namely pressure swing adsorption and temperature swing adsorption, whose efficiency is critical for commercialisation. In addition, a comprehensive life-cycle assessment is performed to provide a novel and timely overview of the environmental impacts of CO2 adsorption using food waste-derived engineered biochars. This review demonstrates the viability and potential of integrating food waste-derived engineered biochars with carbon capture technologies to afford an environmentally friendly innovation for sustainable food waste management and climate change mitigation, which is benefical to achieving UN Sustainable Development Goals including Goals 11-13.