Optimisation of hydrochar production using native African Elemi shell

Abstract African Elemi shell (AES), derived from Canarium schweinfurthii, is a widely available agricultural byproduct in Nigeria with significant potential for value addition. AES is notable for its high energy content (approximately 20 kWh/kg), low ash (5–10%), and minimal moisture (1–5%), making it a promising and sustainable alternative to conventional biomass fuels. The abundance of AES in Nigeria positions it as an attractive feedstock for the development of efficient, cost-effective adsorbents and other value-added materials. In this study, AES particles (300 μm) underwent hydrothermal carbonisation (HTC) in a temperature-controlled, oxygen-free batch reactor using deionised water. The process parameters—including temperature (180–220 °C), residence time (30–900 min), and biomass-to-water ratios (1:8 to 1:12)—were systematically varied. Response Surface Methodology (RSM) was applied to optimise the HTC conditions, focusing on temperatures of 180, 200, and 220 °C and residence times of 0.5, 1, and 1.5 h, with the objective of maximising the hydrochar’s surface area, pore volume, and pore size. Hydrochar produced under optimal conditions exhibited a fixed carbon content of 82% and a volatile organic compound content of 8.26%, highlighting its suitability as an adsorbent. The enhanced surface area and porosity of the hydrochar are particularly advantageous for applications involving the removal of contaminants from gaseous or liquid media. Future work should focus on scaling up the HTC process and assessing the long-term stability and regeneration capacity of AES-derived hydrochar in practical separation and purification systems.