Valorization of fruit waste by biochar production via thermochemical conversion: A mini-review

As people's living standards gradually improved, the demand for fruits increases every year. At the same time, the fruit waste yield also increases, resulting in environmental pollution pressure. Currently, how to dispose the waste is highly concerned to scientists. Producing biochar by thermal conversion is a promising method for the disposal and the valorization of fruit waste. The biochar can be used in various fields, including electrode materials for capacitors, catalyst carriers for electrocatalysis, anaerobic fermentation media for microorganisms, soil improvement, and biosensing carbon dots. Fruit waste, as a typical biomass, primarily consists of proteins, fats, starch, sugars, and cellulose. Compared to other biomasses, for examples, straw and wood residues, fruit waste has a higher moisture content , resulting in different methods used to produce biochar. Currently, pyrolysis, hydrothermal carbonization, and physical chemical activation have been studied on biochar production. However, the industrialization of biochar production from fruit waste is still limited due to the lack of relevant research supports, such as understanding the comprehensive and extensive evaluations. This study provides a comprehensive review of the current methods for preparing biochar from fruit waste, examining the impacts of temperature, residence time, and raw materials. Additionally, it outlines optimal preparation methods and application scenarios for fruit biochar by comparing with straw biochar, offering both experimental and theoretical insights to highlight the valuable fruit biochar.