Utilization of waste-derived biodiesel in a compression ignition engine

Abstract

Air pollution has been broadly concerned as a global issue in all regions. Particulate matter (PM) emission mainly originated from the combustion of diesel engine in transport sector is progressively solved for mitigation. The purpose of this study is to preliminary utilize biodiesel from different feedstock as an alternative fuel in a diesel engine. Waste-derived biodiesel was prepared from waste cooking oil (WCOME) and waste chicken oil (CKOME) by transesterification process. Palm oil-derived biodiesel (POME) was also prepared and used as a reference. Fatty acid profiles of the prepared biodiesel were characterized by a gas chromatography–mass​ spectrometer. The biodiesel was analyzed for fuel characteristics under ASTM standards. The engine test was carried out on a single-cylinder diesel engine at the engine speed of 1500 rpm with full engine load. The engine combustion and performance as well as exhaust emissions of waste-derived biodiesel were compared with palm oil biodiesel and diesel fuel. The PM oxidation temperature was indicated by a simultaneous thermal analyzer. The obtained results disclosed that main fatty acids of POME and CKOME were palmitic acid (C16:0) and oleic acid (C18:1) while that of WCOME were oleic acid (C18:1) and linoleic acid (C18:2). It was evident that kinematic viscosity, specific gravity and flash point of biodiesels were above the limit prescribed by the diesel fuel standard. Lubricity of all biodiesels was bounded by the limitation of diesel specification. CKOME possessed excellent lubricating properties among biodiesels tested. The combustion of WCOME lowered CO, HC and smoke emissions compared to POME while the combustion of CKOME produced similar CO, HC and smoke emissions with more benefit in NOx emissions compared to POME. PM emissions caused by the combustion of biodiesel derived from WCOME and CKOME tended to oxidize easier than those of diesel fuel because the lower temperature for maximum soot oxidation by thermo-gravimetric analysis was obtained. Consequently, biodiesel derived from waste cooking oil and waste chicken oil can be considered as potential candidates to replace the biodiesel derived from palm oil as main feedstock of biodiesel production in Thailand without any penalty in exhaust emissions.