Waste-to-fuel: Biodiesel Production from Watermelon Seed Oil Using Sustainable CaO Nano Catalyst
J. Environ. Nanotechnol., Volume 15, No 2 (June 2026) pp. 649-655
Abstract
The increasing demand for sustainable energy and the depletion of fossil fuel reserves have intensified the search for viable alternative fuels. Biodiesel has gained significant attention due to its renewable nature and compatibility with existing diesel engines. In this study, watermelon seed oil, a non-edible and underutilized feedstock, was investigated for biodiesel production via transesterification using a low-cost CaO-based nano-catalyst derived from waste eggshells. The catalyst, rich in calcium oxide, was synthesized and characterized using FTIR, SEM, and XRD techniques to evaluate its structural and morphological properties. The transesterification process parameters, including catalyst loading, methanol-to-oil molar ratio, and reaction time, were systematically optimized. Under optimal conditions (3 wt% catalyst, 6:1 methanol-to-oil ratio, 4 hours), a maximum biodiesel yield of 99,4% was achieved. The produced biodiesel was evaluated for key fuel properties, including flash point (132 °C) and fire point (142 °C), confirming its suitability as a diesel substitute. The predominant fatty acid composition, mainly linoleic acid along with oleic, palmitic, and stearic acids, contributes to favorable fuel characteristics. This study demonstrates a sustainable approach by integrating waste-derived nano-catalysts with non-edible oil feedstock, thereby reducing production cost and environmental impact. The use of watermelon seed oil combined with eggshell-derived CaO nano-catalyst highlights a novel and economically viable pathway for biodiesel production.
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