Optimization of biodiesel production from Cucurbita pepo (pumpkin) seed oil using snail shell-derived CaO heterogeneous catalyst

Abstract

The commercialization of biodiesel is often constrained by the high cost of feedstocks and catalysts. This study presents a sustainable and cost-effective solution by valorizing two abundant waste resources: cucurbita pepo (pumpkin) seed oil and snail shells. The shells were calcined at 850 °C to synthesize a heterogeneous calcium oxide (cao) catalyst, which was comprehensively characterized (XRD, FTIR, SEM, EDX) and confirmed to be high-purity, mesoporous cao. Due to the oil's high free fatty acid (FFA) content (2.1 %), biodiesel production employed a two-step process: acid-catalyzed esterification followed by base-catalyzed transesterification. Optimization via Response Surface Methodology (RSM) established optimal conditions: a 6:1 methanol to oil molar ratio, 65 °C, 1.5 wt% catalyst, and a 60-minute reaction time, yielding 88.4 % biodiesel. The fuel properties including kinematic viscosity (4.39 mm^²/s), cetane number (51.20), and flash point (166.5 °C) conformed fully with the ASTM standards. This work successfully demonstrates a viable waste to energy pathway, transforming agricultural and molluscan waste into a high quality, standards-compliant biodiesel.