Eco-Friendly Synthesis of Solid Base Catalysts from Locally Available Agricultural, Food, and Marine Wastes for Sustainable Biodiesel Production

Abstract

This study proposes an eco-friendly and cost-effective approach for the preparation of solid basic catalysts from locally available agricultural, food, animal, and marine wastes for sustainable biodiesel production. Eight waste-derived feedstocks were investigated as potential catalyst precursors and processed through drying, carbonization, and calcination to obtain solid catalysts. Among the prepared catalysts, peanut shells, eggshells, seashells, seawater, and tea waste were selected for detailed characterization. X-ray diffraction (XRD) analysis confirmed the presence of catalytically active CaO and MgO phases in the obtained materials. The eggshell-derived catalyst demonstrated promising catalytic activity, achieving a biodiesel yield of 85% under optimized transesterification conditions using an 8:1 methanol-to-oil molar ratio, 3 wt% catalyst loading, 64 °C, and 3 h reaction time. Further comparative experiments showed that the walnut/CaO and seawater/CaO catalysts provided the highest yield among the investigated methanol- and ethanol-based systems, reaching 85.4% and 72%, respectively, while CaO(commercial) alone achieved 75%. The effect of alcohol type was also investigated by comparing methanol- and ethanol-based transesterification. FTIR analysis confirmed the formation of biodiesel through the characteristic functional groups of the produced fuel, while XRD was used to evaluate the crystalline phases of the catalysts. The measured physicochemical properties of the produced biodiesel were within the specified limits of ASTM D6751. Overall, the findings demonstrate the potential of locally available waste-derived materials as low-cost solid basic catalysts for biodiesel production while promoting waste valorization and sustainable energy generation.

Keywords: Biogenic catalysts; waste valorization; biodiesel