Effect of biodiesel origin on regulated and particle-bound PAH (polycyclic aromatic hydrocarbon) emissions from a Euro 4 passenger car

This study investigates the impact of low concentration biodiesel blends on the regulated and particle-bound polycyclic aromatic hydrocarbon (PAH) emissions from a modern passenger car. Emissions measurements were performed on a chassis dynamometer using constant volume sampling technique, following the European regulations. All measurements were conducted over the New European Driving Cycle (NEDC) and the Artemis driving cycles. Aiming to evaluate the fuel impact on emissions, a soy-based, a palm-based, and a rapeseed oil based biodiesel were blended with diesel fuel at proportions of 10, 20, and 30% by volume. The emissions of PM, HC, and CO decreased with biodiesel over most driving conditions. Some increases were observed over the NEDC, which may be attributed to the cold-start effect and to certain fuel characteristics. NOx emissions increased with biodiesel and strongly were dependent to the degree of unsaturation of the fuel. CO2 emissions and fuel consumption followed similar patterns and increased with biodiesel. PAH emissions presented discordant results, leading to the hypothesis that the influence of biodiesel source material was particularly strong on the formation of these pollutants. Both increases and decreases were observed in PAH, nitrated PAH and oxygenated PAH compounds with the use of biodiesel blends.

► The use of biodiesel exhibited reductions in PM, CO, and HC emissions, independent its raw material. ► Emissions of NOx tend to increase with increasing levels of unsaturation in the methyl ester hydrocarbon chain. ► Some increases in light PAHs with biodiesel were observed, which were the dominant compounds in the exhaust. ► Emissions of nitro-PAHs and oxy-PAHs were reduced with biodiesel blends. ► The unsaturated biodiesel blends resulted in higher PAH emissions than the saturated blends.