With the world's growing energy demand and increasing environmental concerns, adopting sustainable and eco-friendly energy sources has become a pressing necessity. This project explores an innovative solution that tackles two major problems simultaneously waste management and clean energy production. India produces about 3 million metric tons of used cooking oil (UCO) annually, with 60% reused in food, risking health issues like heart disease and cancer. Much of the rest discarded or underused for biodiesel. Repeated frying raises free fatty acid levels, increasing health risks. This project converts UCO into renewable, biodegradable biodiesel, providing a cleaner diesel alternative while reducing environmental and health hazards.

Biodiesel synthesized from used cooking oil via transesterification using methanol and NaOH. The final product met ASTM D6751 standards, with a viscosity of 4.56 mm²/s, density of 925 kg/m³, flash point of 182 °C, and calorific value of 39,216 kJ/kg slightly lower than diesel but with improved combustion stability. Engine tests was conducted on diesel, B20, and B20 blends enhanced with ZnO nanoparticles synthesized from cow dung (B20-25 NP and B20-50 NP). The B20-50 NP blend showed the best performance, achieving a brake thermal efficiency of 35.55% and the lowest specific fuel consumption (0.26 kg/kWh). Emissions of HC (3ppm), CO (0.02%), and NOₓ (602 ppm) significantly reduced, with a slight increase in CO₂ indicating more complete combustion. The results highlight the potential of nanoparticle-enhanced biodiesel as a cleaner and more efficient alternative fuel.

Our findings reveal that the biodiesel derived from waste cooking oil meets quality benchmarks such as less emission compared to normal diesel, also offers a cost- effective and environmentally responsible alternative to non-renewable fuel. This project opens an opportunity to supports circular economy by converting waste into a valuable product. It serves as a small but meaningful step toward a cleaner, more sustainable future