Waste-to-catalyst strategy: KOH-impregnated activated carbon derived from charcoal factory waste for biodiesel production using waste cooking oil

Valorization of low-carbon feedstock and development of waste-based heterogeneous catalysts are key strategies in sustainable biodiesel production. This study utilized charcoal factory waste as a carbon-based catalyst support in biodiesel production from waste cooking oil (WCO). The catalysts preparation including charcoal activation, KOH impregnation, and catalyst calcination. A series of instruments, including SEM-EDX, FTIR, XRD, and BET-BJH, were employed to obtain an understanding of the catalyst characteristics. The results showed that 40% KOH-impregnated activated carbon (IM40) contained the highest K 2 O, up to 38.25%, with the presence of K-O, Fe-O, and -CO 3 , confirming its potential as a heterogeneous base catalyst. The surface area, pore volume, and pore size of the IM40 catalyst were 8.08 m 2 /g, 0.022 cc/g, and 1.912 nm, respectively. The best biodiesel yield (93.67%) was obtained at the use of 2%-catalyst loading, reaction temperature of 60°C, and reaction time of 120 min. The resulting biodiesel has met several biodiesel quality parameters based on ASTM D 6751/09, EN 14214/09, and SNI 7182:2024. Overall, this study confirms the potential of KOH-impregnated activated carbon from charcoal factory waste as a promising heterogeneous catalyst for sustainable biodiesel production.