Chemical characterization of biofuel exhaust emissions.

Use of biodiesel is increasing following implementation of various policy instruments and a surge in demand due to growing urbanized populations. A series of experiments to characterize the chemical composition of emissions generated during combustion of petro-diesel (B0), biodiesel blends (B5, B10, B20), biodiesel (B100) and pure plant oil were performed in a standard EURO III truck engine. In total 108 separate components of emissions from the various fuels were quantitatively assessed. Further, the size dependence of PAH emissions was investigated. It was found that biodiesel was associated with significantly lower levels of PM and CO emissions and reduced levels of components such as aldehydes, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAH) and their derivatives, hopanes/steranes and elemental carbon/organic carbon (EC/OC). The majority of particle bound PAH were associated with the ultra-fine fraction (diameter range of 0.01–0.14 μm). The use of a diesel particulate filter reduced B0 emissions to levels of B100. While our study was conducted under ideal controlled conditions, our data support the widely held view that biodiesel emissions have a different chemical composition than emissions from petro-diesel. The consequences of this in terms of health and environmental impact should be assessed in wider studies.