Production and application of biodiesel from waste cooking oil

Biodiesel has been identified as an alternative and promising fuel source to reduce the dependency on conventional fossil fuel in particular diesel. In this work, waste cooking oil (WCO) of restaurants is considered to produce biodiesel. A well-established transesterification reaction by sodium hydroxide (NaOH) catalytic and supercritical methanol (CH₃OH) methods are applied to obtain biodiesel. In the catalytic transesterification process, biodiesel and glycerine are simultaneously produced. The impact of temperature, methanol/WCO molar ratio and sodium hydroxide concentration on the biodiesel formation were analysed and presented. It was found that the optimum 95% of biodiesel was obtained when methanol/WCO molar ratio was 1:6 under 873 K temperature with the presence of 0.2% NaOH as a catalyst. The waste cooking oil blend proportions were 10%, 15%, 20% and 25% and named as bio-diesel blends B-10, B-15, B-20, and B-25, respectively. Quality of biodiesel was examined according to ASTM 6751: biodiesel standards and testing methods. Important fuel properties of biodiesel, such as heating value, cetane index, viscosity, and others were also investigated. A four-stroke single cylinder naturally aspirated DI diesel engine was operated using in both pure form and as a diesel blend to evaluate the combustion and emission characteristics of biodiesel. Engine performance is examined by measuring brake specific fuel consumption and fuel conversion efficiency. The emission of carbon monoxide (CO), carbon dioxide (CO₂), nitrogen oxides (NO_x), and others were measured. It was measured that the amount of CO₂ increases and CO decreases both for pure diesel and biodiesel blends with increasing engine load. However, for same load, a higher emission of CO₂ from biodiesel blends was recorded than pure diesel.