Optimization of Biodiesel Yield from Neem Seed Oil Using Calcined Eggshell Catalyst: Characterization and Performance Analysis

Abstract

This study examines the optimization of biodiesel yield production from Neem seed oil (Azadirachta indica A. Juss), a non-edible and renewable feedstock. The aim is to develop a sustainable, environmentally friendly fuel alternative using calcined eggshell as a low-cost heterogeneous catalyst in a base-catalyzed transesterification process. Catalyst concentrations of 0.5%, 1%, and 1.5% (wt.% of oil) were tested at reaction times of 70, 110, and 150 minutes, yielding nine biodiesel samples. The optimum biodiesel was analyzed for physico-chemical properties, while GC-MS and FTIR were used to determine its chemical composition and functional groups. The optimum sample was blended with diesel to form B10, B20, and B30. These fuels were tested on a single-cylinder CI engine at a constant load of 4.5 kN and 1500 rpm to evaluate performance and emissions. A maximum yield of 100% was obtained at 1% catalyst concentration and 70-minute reaction time. B30 and B100 demonstrated the highest brake thermal efficiency, while B10 recorded the lowest exhaust gas temperature. Brake power increased with higher biodiesel content, with B30 and B100 giving the best results. Emission analysis showed lowest UHC, NOx, and CO₂ emissions at B20 and B30, while CO emissions were zero for all blends. Neem-based biodiesel produced with calcined eggshell catalyst is a viable and cleaner alternative to petro-diesel, offering strong performance and reduced emissions. Further research should examine catalyst reusability, scale-up feasibility, multi-load engine testing, long-term engine durability, and ethanol-based transesterification.