PRODUCTION OF BIODIESEL FROM WASTE ANIMAL FATS USING CAO CATALYST SYNTHESIZED FROM EGGSHELLS

The rapid depletion of fossil fuel reserves and the adverse environmental consequences associated with their utilization have necessitated the exploration of renewable and sustainable energy alternatives. Biodiesel has emerged as a viable substitute owing to its biodegradability, renewability, and comparatively lower emissions relative to petroleum diesel. This study investigates the production of biodiesel from bovine tallow employing calcium oxide (CaO) synthesized from waste eggshells as a heterogeneous catalyst. The eggshells, predominantly composed of calcium carbonate, were subjected to calcination at 870 °C to yield CaO, which was subsequently characterized by X-ray diffraction (XRD) to ascertain its crystalline structure and catalytic efficacy. The tallow feedstock, initially exhibiting a free fatty acid (FFA) content of 4.06%, was pretreated via esterification to an acceptable level prior to transesterification with methanol. Process optimization was undertaken using response surface methodology (RSM) within a central composite design framework, considering methanol-to-oil molar ratio, catalyst loading, and reaction time as variables. The resulting cubic model (R² = 0.9998) demonstrated excellent predictive accuracy. Optimal conditions (methanol-to-oil ratio of 5.3:1, catalyst loading of 1 wt%, and reaction time of 60 minutes) afforded a biodiesel yield of 95.6%. Physicochemical characterization of the biodiesel revealed a density of 0.8684 g/cm³, specific gravity of 0.8916, a pour point of 10 °C, and a cloud point of 17 °C. These properties are consistent with values reported in literature, although the elevated pour and cloud points indicate limitations in cold-climate applications. The findings underscore the suitability of eggshell-derived CaO as an efficient and low-cost catalyst, demonstrating the dual benefit of valorizing waste resources while advancing sustainable biodiesel production.