Biochar from coconut residues: An overview of production, properties, and applications

The world's growing population and industrial activities have led to increased energy demand and the depletion of fossil fuels, causing environmental pollution and global warming. A paradigm shift from fossil fuel resources to sustainable energy sources is therefore inevitable. The production of biofuel, such as biochar, from biomass has been receiving increased research attention due to its benefits, which address several environmental issues while advancing the circular economy and sustainable development. This manuscript presents a comprehensive overview of the conversion of coconut biomass residue into biochar, focusing on production methods, physicochemical properties, and versatile applications. Various techniques that have been used for coconut biochar production, including pyrolysis, gasification, torrefaction, and hydrothermal carbonization, are examined in detail, considering their potential for sustainable resource utilization. The interplay between production parameters and resultant biochar characteristics is underscored, elucidating the influence of feedstock composition, pyrolysis conditions, and activation procedures. The findings revealed that the produced biochar has been employed in wastewater treatment, soil amendment, and carbon sequestration, among others. This vast application is a result of the biochar's distinct physicochemical properties, including high porosity, substantial surface area, the presence of several surface functional groups, and thermal stability. Notwithstanding, biochar production from coconut residues faces several challenges. These challenges were addressed in this review, and relevant recommendations were proposed.