An experimental investigation was carried out to study the performance, emissions and combustion characteristics of a compression ignition (CI) engine fuelled with waste chicken fat biodiesel with alumina nanoparticles as an additive. The disposal of waste chicken creates environmental pollution, hence it is decided to extract oil from the waste chicken fat and produce biodiesel through transesterification process. As the chicken fat contains 13.6 % free fatty acid (FFA), a pre-treatment process was carried out using Ferric sulphate as a catalyst in order to reduce the FFA content less than 1 % to prevent soap formation during the process. Potassium hydroxide was used as catalysts for the effective conversion of triglycerides of waste chicken fat into methyl ester. Various diesel-biodiesel-alumina blends were prepared by varying the biodiesel proportions of 20 and 40 % by volume and 25 and 50 ppm of alumina nanoparticles to study its operating characteristics on a computerized single cylinder, constant speed CI engine. Aluminium oxide (Al 2 O 3 ) nanoparticles were used as fuel born catalyst in order to enhance the combustion characteristics and reduce the harmful emissions. The engine test results showed less improvement in brake thermal efficiency and significant reduction on the hydrocarbons and carbon monoxide emissions. However, higher nitrogen oxide emissions were recorded due to the increase in combustion temperature as the nanoparticles enhanced the surface area to volume ratio which improves the thermal conductivity of the fuel blend resulted in improved combustion. Smoke reduction of 52.8 % was observed in B40 fuel blend with 50 ppm alumina nanoparticles under full load conditions. Keywords Alumina nanoparticles Á Waste chicken fat biodiesel Á Performance Á Combustion Á Engine exhaust emissions Abbreviations Al 2 O 3 Aluminium oxide B20Al25 Diesel 80 % ? Biodiesel 20 % ? Alumina nanoparticles 25 ppm B20Al50 Diesel 80 % ? Biodiesel 20 % ? Alumina nanoparticles 50 ppm B40Al25 Diesel 60 % ? Biodiesel 40 % ? Alumina nanoparticles 25 ppm B40Al50 Diesel 60 % ? Biodiesel 40 % ? Alumina nanoparticles 50 ppm bmep Brake mean effective pressure BSFC Brake specific fuel consumption BTE Brake thermal efficiency CI Compression ignition CNT Carbon nanotubes CO Carbon monoxide FFA Free fatty acid HC Hydrocarbon HRR Heat release rate ID Ignition delay NO x Nitrogen oxides PM Particulate matter ppm particles per million RoPR Rate of pressure raise TDC Top dead center WCF Waste chicken fat WCFME Waste chicken fat methyl ester

Ever increasing demand and consequent rise in prices of petroleum products, stringent emission standards, the exponential depletion rate of fossil fuel reserves and escalation in the number of vehicles on the road have forced us to look for alternatives to meet the present and future demands of the energy requirements. Biodiesel production from waste oils and fats are cost effective methods which prevent the environmental pollution by proper disposal techniques. In this study, biodiesel was prepared from the waste effect chicken fat using the two stage esterification process. The present investigation deals with the cold exhaust gas recirculation (EGR) with the flow rates of 10, 20, 30% on a four stroke, single cylinder, direct injection (DI) diesel engine fueled with waste chicken fat biodiesel blends to reduce the NOxemissions of the engine. Experimental results showed higher oxides of nitrogen emissions when fueled with waste chicken fat biodiesel without EGR and found reduced NOxemissions about 25% when operating with B20 fuel blend with 30% EGR. The EGR level was optimized as 20% based on the significant reduction in NOx emissions, minimum possible smoke, CO, HC emissions and comparable brake thermal efficiency.