Light vehicle regulated and unregulated emissions from different biodiesels

In this study, the regulated and unregulated emissions profile and fuel consumption of an automotive diesel and biodiesel blends, prepared from two different biodiesels, were investigated. The biodiesels were a rapeseed methyl ester (RME) and a palm-based methyl ester (PME). The tests were performed on a chassis dynamometer with constant volume sampling (CVS) over the New European Driving Cycle (NEDC) and the non-legislated Athens Driving Cycle (ADC), using a Euro 2 compliant passenger vehicle. The objectives were to evaluate the impact of biodiesel chemical structure on the emissions, as well as the influence of the applied driving cycle on the formation of exhaust emissions and fuel consumption. The results showed that NOx emissions were influenced by certain biodiesel properties, such as those of cetane number and iodine number. NOx emissions followed a decreasing trend over both cycles, where the most beneficial reduction was obtained with the application of the more saturated biodiesel. PM emissions were decreased with the palm-based biodiesel blends over both cycles, with the exception of the 20% blend which was higher compared to diesel fuel. PME blends led to increases in PM emissions over the ADC. The majority of the biodiesel blends showed a tendency for lower CO and HC emissions. The differences in CO2 emissions were not statistically significant. Fuel consumption presented an increase with both biodiesels. Total PAH and nitro-PAH emission levels were decreased with the use of biodiesel independently of the source material. Lower molecular weight PAHs were predominant in both gaseous and particulate phases. Both biodiesels had a negative impact on certain carbonyl emissions. Formaldehyde and acetaldehyde were the dominant aldehydes emitted from both fuels.