Biochar production from palm kernel shell as alternative catalyst for thermochemical hydrogen production

Abstract

Palm kernel shell (PKS), an abundant agro-industrial residue, represents a largely underutilized biomass resource in West Africa despite its high fixed carbon content and structural properties that make it suitable for energy applications. While PKS has been studied for adsorbents, biofuels, and composites, its potential as a renewable catalyst in thermochemical hydrogen production remains underexplored. This study aimed to develop PKS-derived biochar and activated carbon as sustainable and cost-effective catalytic precursors for biomass gasification. The methodology adopted a two-stage approach: first, Box–Behnken Design (BBD) under Response Surface Methodology (RSM) was employed to optimize pyrolysis parameters (temperature, heating rate, and residence time) for biochar production. Then, the optimum biochar underwent steam activation under controlled conditions to enhance microporosity and catalytic properties. Proximate, elemental, physicochemical, and structural analyses were performed, including determination of fixed carbon, volatile matter, density, ash content, and iodine number. Results revealed that pyrolysis at 500 °C and 15 °C/min with a residence time of 60 min produced the optimum biochar (PKS-OP1) with high fixed carbon (77.1 wt%) and moderate porosity (iodine number: 155 mg/g). Subsequent steam activation transformed this biochar into a highly microporous activated carbon (PKS-Akt 280) with enhanced properties: iodine number of 885 mg/g, low volatile matter (~4 wt%), high fixed carbon (90 wt%), and pH ~10, demonstrating superior porosity, surface area, and thermal stability. Comparative analysis showed PKSAkt 280 matches or outperforms some conventional catalysts, positioning it as a viable catalyst precursor. The study concludes that PKS-derived activated carbon offers an efficient, low-cost, and sustainable alternative to traditional metal-based catalysts for hydrogen production via gasification. It is recommended that further pilot-scale testing and industrial-scale process development be investigated to integrate PKS-biochar as a renewable catalyst pathway, contributing to waste valorization, cleaner hydrogen production, and the circular bioeconomy in palmgrowing regions.