From coconut shell to functional carbon: A review of thermochemical production, activation, and sustainability assessment of biochar

The coconut industry generates large amounts of shell biomass that can be upgraded into value-added carbon materials for environmental and industrial use. This review summarizes coconut shell-derived biochar across the full chain from production to sustainable applications, with emphasis on how processing controls material properties and performance. It first reviews thermochemical conversion routes (mainly pyrolysis and gasification) and the key feedstock/biochar characteristics (e.g., elemental composition, lignin content, moisture, and ash). It then compares major activation strategies, such as physical and chemical activation, alongside emerging approaches (plasma, ultrasound, and electrochemical treatments), highlighting how they tune specific surface area, pore structure, and surface functional groups. Building on these property changes, the review links structure–property relationships to performance in representative applications, including wastewater treatment, CO 2 capture, biodiesel-related catalytic/support roles, and soil amendment/remediation. To support sustainable deployment, it also summarizes regeneration and reuse options for spent biochar and discusses how life cycle assessment can be used to evaluate environmental impacts and identify process hotspots. Finally, the review outlines current challenges and provides practical recommendations for optimizing production and activation conditions, improving comparability through more consistent characterization, and guiding the design of coconut shell–derived biochar for scalable, sustainable applications.