Synthesis and characterization of CaO/zeolite for homogenizer-intensified room temperature biodiesel production of high free fatty acid feedstock

This study reports the synthesis and application of a CaO/zeolite composite derived from waste chicken eggshells for biodiesel production from high free fatty acid (FFA) feedstocks under room temperature conditions. The catalyst was characterized using XRD, XRF, SEM-EDX, and FTIR, confirming successful CaO incorporation within the zeolite framework. Homogenizer-assisted esterification of oleic acid with methanol achieved a maximum biodiesel conversion of 97.7 % and yield of 93.1 % under reaction conditions of 18 wt% of catalyst, 1:15 M ratio, 45 min and 4000 rpm. The catalyst maintained conversions above 95 % for four cycles before declining to 89.8 % in the fifth, demonstrating promising short-term reusability. Energy efficiency analysis revealed that while conversion was highest at 4000 rpm, productivity and energy use were optimally balanced at 3000 rpm, highlighting the trade-off between performance and sustainability. Compared to conventional methods requiring elevated temperatures, this approach offers significant energy savings and reduced environmental footprint. These findings demonstrate the potential of waste-derived CaO/zeolite catalysts combined with homogenizer intensification for scalable, low-energy biodiesel production. • Waste chicken eggshells were valorized into a CaO/zeolite composite catalyst. • Homogenizer-assisted esterification enabled room-temperature biodiesel production. • High biodiesel conversion (97.7 %) and yield (93.1 %) achieved under mild conditions. • Process offers substantial energy savings compared to conventional heating methods.