Performance and emission analysis of cotton seed biodiesel enhanced with nano-MgO as a sustainable fuel in a compression ignition engine

• Nano MgO improves BTE by 2.2 % and reduces BSFC by 6.8 % in CI engine tests. • Emissions drop: CO by 12 %, HC by 10 %, NOx by 14 %, and smoke by 28 % at 70 ppm. • FTIR confirms enhanced molecular structure in MgO-blended cotton seed biodiesel. • LCA shows lower GHG emissions and reduced environmental impact vs. diesel. • Circular economy boosts sustainability using waste-derived MgO and biodiesel. Biofuels present a sustainable alternative to fossil fuels, offering comparable engine performance while significantly reducing emissions. This study examines cottonseed oil, a renewable biomass feedstock, as a source for converting biodiesel and testing it in a single-cylinder diesel engine operating at 1500 rpm under five load conditions, ranging from 0 to 100 percent. Five different fuel blends were evaluated, with a particular focus on the B30 blend. Additionally, nano-magnesium oxide was added at concentrations of 10, 40, and 70 ppm to enhance engine performance and reduce emissions. Among all the fuels tested, B30 exhibited the best engine characteristics. The addition of 70 ppm of nano-magnesium oxide led to a 4.5 % increase in brake thermal efficiency (BTE) and an 11 % reduction in brake-specific fuel consumption (BSFC) compared to the standard B30. Emission measurements revealed significant reductions in carbon monoxide (30 %), hydrocarbons (26 %), nitrogen oxides (23 %), and smoke (40 %) compared to regular diesel. These improvements stem from nano-magnesium oxide’s catalytic activity, which enhances combustion and oxidation processes. A life cycle analysis (LCA), in conjunction with economic and environmental evaluations based on circular economy principles, confirmed the long-term sustainability and practicality of nano-magnesium oxide enhanced cottonseed biodiesel. Although production costs are higher due to the nano-additives, the gains in engine efficiency and reduced emissions justify the expense. This study highlights nano-magnesium oxide-doped cottonseed biodiesel as a promising, eco-friendly fuel for internal combustion engines, aligning with future policies aimed at sustainable energy transitions.