Advances in emission characteristics of diesel engines using different biodiesel fuels

Biodiesel fuels derived from a variety of plant and animal feedstocks are promising renewable alternative diesel fuels in view of energy security, environmental protection and the great potential of carbon dioxide (CO₂) reduction from the whole cycle of biodiesel production. This review only focused on the characteristics of oxides of nitrogen (NO_x), particulate matter (PM) and polyaromatic hydrocarbon (PAH) emissions found in recent years when various biodiesel fuels with different physicochemical properties were used in diesel engines. The effect of ethanol addition, exhaust gas recirculation (EGR) and various catalytic converters on the emissions above and particle size distributions of diesel engines was presented. To meet stringent exhaust emission regulations when biodiesel is used, efforts on engine electronic control systems, the improvement in conversion efficiency of catalysts, particulate trapping efficiency and biodiesel preparation require to be made.