Nickel-doped chicken eggshell-derived catalyst for cottonseed oil-based fatty acid methyl ester: Synthesis, characterization, and engine performance and emission assessment

The present research focused on the synthesis and characterization of fatty acid methyl ester (FAME) derived from cottonseed oil using a nickel-doped chicken eggshell (Ni-CaO) catalyst, and evaluated the biodiesel’s engine performance and emission characteristics. The Ni-CaO catalyst was prepared via calcination and characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), showing improved catalytic activity and higher FAME yields compared to un-doped CaO. The maximum oil yield obtained from cottonseeds was 44.75 wt%, achieved using 100 g of seeds under extraction conditions of 65ºC, 5 h, a 6:1 solvent-to-solid ratio, and atmospheric pressure using solvent extraction method. Similarly, the maximum FAME yield reached 96 wt% at 60ºC, 120 min reaction time, 5 wt% catalyst loading, and a 12:1 methanol-to-oil ratio via transesterification reaction. The produced cottonseed methyl ester (COME) complied with ASTM D6751 and EN 14214 standards, satisfying critical fuel quality parameters such as cetane number, viscosity, acid value, flash point, and moisture content. Engine performance tests demonstrated that COME exhibited a slight decrease in brake thermal efficiency (2–4 %) and a 6–10 % increase in brake specific fuel consumption compared to diesel, while significantly reducing CO, hydrocarbons (HC), and particulate emissions, indicating improved combustion characteristics and environmental performance.