فهرست نشریات علمی دسترسی آزاد ایران

The global reliance on fossil fuels harms the environment, creating an urgent need for renewable energy. Biodiesel offers a low-emission, eco-friendly alternative. This paper presents the novel biodiesel production from waste vegetable oils using calcium oxide synthesized from waste eggshells calcined at 900°C as an economical, eco-friendly, heterogeneous catalyst. The novelty of this study lies in its focus on optimizing biodiesel production under milder reaction conditions (50 °C, 6:1 methanol-to-oil ratio), significantly reducing energy consumption compared to existing methodologies. Waste valorization in this research is accomplished using biowaste-derived CaO, which promotes circular economy practices by converting waste into valuable resources. In the present case, biodiesel that passed all ASTM D6751 diesel engine specifications demonstrated some encouraging physical properties, including density, viscosity, flash point, pour point, acid value, and cetane number. Gas Chromatography-Mass Spectrometry (GC-MS) analysis showed a high conversion of Free Fatty Acids (FFA) to Fatty Acid Methyl Esters (FAME). The significant components are oleic acid methyl ester at 66.48% and palmitic acid methyl ester at 22.23%. The optimum transesterification conditions (5.5 wt.% catalyst concentration, a 6:1 methanol-to-oil molar ratio, and a reaction temperature of 50°C) were determined using Box-Behnken Design and Response Surface Methodology, yielding a maximum FAME conversion of 90.4%. Reusability was elevated, with the CaO catalyst yielding 82% over five cycles, enabling cost-effective biodiesel synthesis. The quadratic regression model demonstrated substantial predictive accuracy, achieving an R² value of 96.02% and an adjusted R² of 88.86%. The present study has revealed RSM's efficiency in optimizing biodiesel production, underlining the enormous potentialities of waste-derived CaO catalysts toward advanced economic and ecological sustainability in renewable energy production.