Valorization of cocoa bean shell residue from supercritical fluid extraction through hydrothermal carbonization for porous material production

This study investigated the potential for high-value utilization of cocoa shell (CS) residues derived from supercritical fluid extraction (SFE) by converting them into hydrochar through hydrothermal carbonization (HTC) and activation (A-HTC). Hydrochar produced from residues extracted with water as a co-solvent exhibited the highest carbon content (78.7 %) after HTC and activation, highlighting the critical role of the co-solvent in optimizing dehydrogenation and dehydration reactions. Structural analysis revealed that residues rich in water-soluble components formed smaller pores, whereas lipid-rich residues formed larger pores. Activated hydrochar obtained from water-extracted residues demonstrated the largest surface area (315 m²/g) and pore diameter (7.10 nm), indicating mesoporous properties suitable for adsorption applications. The Van Krevelen diagram confirmed that HTC hydrochar stability improved through condensation and aromatization processes. By integrating SFE with HTC, this study presents a systematic approach for converting by-products into high-value hydrochar, offering a sustainable solution for resource recycling and utilization.