Valorization of waste cooking oil, plantain peel and snail shell for the optimization of biodiesel production

Biodiesel is a viable alternative to non-renewable fossil fuels. However, its commercialization faces challenges due to the high costs of conventional feedstocks. This study investigated the influence of reaction parameters—catalyst concentration, reaction temperature, and reaction time—on the yield of synthesized biodiesel from waste cooking oil using snail shell and plantain peel wastes as catalysts. Snail shells were calcined at 800 °C to produce CaO and characterized by X-ray fluorescence. Organic KOH, extracted from plantain peel ash burned at 750 °C, impregnated the CaO to form a composite KOH/CaO catalyst. Using low-quality feedstock (acid value of 8.8 mg KOH/g oil), the oil underwent acid-esterification followed by transesterification under varied conditions. The optimal parameters, determined via response surface methodology (RSM), were 7% wt/wt catalyst concentration, 60.51 °C reaction temperature, and 1.93 h reaction time, achieving a maximum biodiesel yield of 92.23%. The best experimental yield, 92.10%, was obtained using a 2:1 green KOH/CaO ratio. Physicochemical properties and biodiesel composition conformed to ASTM D6751 standards. The highest fatty acid to methyl ester conversion rate, 93.86%, was achieved using the optimized snail shell catalyst. This research demonstrates that converting waste into biodiesel is not only feasible but also adds value to waste materials.