Effect of Biodiesel Origin on the Regulated and PAH Emissions from a Modern Passenger Car

This study investigates the impact of low concentration biodiesel blends on the regulated and polycyclic aromatic hydrocarbon (PAH) emissions from a modern passenger vehicle. The vehicle was Euro 4 compliant fitted with a direct injection common-rail diesel engine and a diesel oxidation catalyst. Emission and fuel consumption measurements were performed on a chassis dynamometer using constant volume sampling (CVS) technique, following the European regulations. All measurements were conducted over the type approval New European Driving Cycle (NEDC) and the real-traffic-based 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 an ultra-low sulfur diesel at proportions of 10, 20, and 30% by volume. The experimental results revealed that 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. NO_x emissions were found higher with biodiesel especially during Artemis operation. 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. Overall, biodiesel at low blending ratios may adversely impact toxic emissions and ultimately alter urban air quality.