Curry Leaf–Derived CaO Catalyst for Sustainable Biodiesel Production from Waste Cooking Oil: RSM‐BBD Optimization

Abstract The primary objective of the study was to develop a green and cost‐effective catalyst from an agricultural bio resource and to optimize the transesterification process for enhanced biodiesel yield. To achieve this, calcium oxide (CaO) was synthesized from curry leaf (Murraya koenigii) extract and employed as a heterogeneous catalyst in the transesterification of waste cooking oil (WCO). X‐ray diffraction confirmed the crystalline nature of the synthesized catalyst and the average crystalline size is 48 nm. Optimization of the transesterification process was carried out using Box–Behnken design–response surface methodology (BBD–RSM). Key process parameters, including catalyst dosage (wt%), temperature (°C), oil‐to‐methanol molar ratio, and reaction time (minutes), were optimized to achieve maximum biodiesel yield. A maximum yield of 91.22% was obtained under the optimized conditions: 4 wt% catalyst, 60 °C, a 1:6 oil‐to‐methanol molar ratio, and 120 min of reaction time. FTIR (Fourier‐transform infrared spectroscopy) analysis of the biodiesel showed characteristic peaks indicative of biodiesel, while GC–MS (gas chromatography–mass spectrometry) analysis confirmed the presence of monounsaturated fatty acids (MUFAs). These results confirm that CaO synthesized via a green synthesis route using curry leaves can serve as a viable catalyst for the sustainable production of biodiesel.