Deciphering methanolysis of modified waste coconut scum oil into biodiesel using green NaOH/SnO2 nanocatalyst: Optimization, thermo-kinetics, cost-evaluation and diesel engine studies

High-quality biodiesel production mainly depends on the quality of the feedstock utilized. Improving the feedstock quality is greatly desired and can be applied to any feedstock to increase biodiesel production. Waste coconut scum oil (WCSO) is treated with cyclo-pentyl-methyl ether (CPME) to improve the miscibility and mass transfer for biodiesel generation. The sodium hydroxide integrated with tin oxide nanoparticles (NaOH/SnO 2 NPs) is used as an effective catalyst for treated-feedstock biodiesel production. Initially, SnO 2 NP S are synthesized using A. polystachya leaves extract and synthesized SnO 2 is characterized through various techniques. A maximum yield of 99. 7 % is achieved under the conditions of 10 % v/v CPME co-solvent, a 3 wt%SnO 2 /0. 15 wt%NaOH catalyst concentration, reaction temperature of 60 °C, molar ratio of 11: 1, reaction time of 40 min, and an agitation speed of 600 rpm. Notably, NaOH/SnO 2 showed excellent reusability up to the 6th cycle, and the fuel properties treated with CPME showed good properties compared to bare feedstock. The calculated activation energy for conversion of oil to methyl esters was found to be 38. 19 kJ/mol, and the frequency factor was 2. 2 × 10 4 min −1. The thermodynamic analysis shows that the enthalpy and entropy of the activation process are found to be 35. 47 kJ/mol and −0. 17 kJ/mol. K, respectively. The economic analysis demonstrated that, the cost of biodiesel using NaOH/SnO 2 nanocatalyst is 78. 74 (0. 90). Further, addition of CPME in the biodiesel/diesel blend improved various performance parameters. At 3. 48 kW, 1. 33 % of BTE increases using B20-15CPME, whereas B20-5CPME decreases, at 0. 87 kW, 3. 4 % decreases and at 3. 49 kW, BSFC increases using B20-15CPME. At 3. 48 kW, carbon monoxide (CO) and hydrocarbon (HC) decrease to 48 % and 5. 65 %, respectively, carbon dioxide (CO 2) and nitrogen oxides (NOx) increase to 9. 37 % and 16. 53 %, compared to diesel fuel.