A number of investigations have examined the impact of the use of biodiesel on the emissions of carbon dioxide and regulated emissions, but limited information exists on the chemical composition of particulate matter from diesel engines burning biodiesel blends. This study examines the composition of diesel particulate matter (DPM) emissions from a commercial agriculture tractor burning a range of biodiesel blends operating under a load that is controlled by a power take off (PTO) dynamometer. Ultra-low sulfur diesel (ULSD) fuel was blended with soybean and beef tallow based biodiesel to examine fuels containing 0% (B0), 25% (B25), 50% (B50), 75% (B75), and 100% (B100) biodiesel. Samples were then collected using a dilution source sampler to simulate atmospheric dilution. Diluted and aged exhaust was analyzed for particle mass and size distribution, PM 2.5 particle mass, PM 2.5 organic and elemental carbon, and speciated organic compounds. PM 2.5 mass emissions rates for the B25, B50, and B75 soybean oil biodiesel mixtures had 20%-30% lower emissions than the petroleum diesel, but B100 emissions were about 40% higher than the petroleum diesel. The trends in mass emission rates with the increasing biodiesel content can be explained by a significant decrease in elemental carbon (EC) emissions across all blending ranges and increasing organic carbon (OC) emissions with pure biodiesel. Beef tallow biodiesel blends showed similar trends. Nevertheless, it is important to note that the study measurements are based on low dilution rates and the OC emissions changes may be affected by ambient temperature and different dilution conditions spanning microenvironments and atmospheric conditions. The results show that the use of biodiesel fuel for economic or climate change mitigation

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To better understand the impact of ambient temperature and fuel on the emissions of ultrafine particles from spark ignition light-duty vehicles, experiments were conducted to examine the impact of ethanol-gasoline mixtures, compressed natural gas (CNG), and ambient temperature, on the size distribution and number emissions of particles. Vehicles were tested on a chassis dynamometer under controlled conditions of ambient temperature spanning from 60 to 85°F. A dual fuel vehicle operating with CNG and 6% ethanol-gasoline blends (E6); and a flex fuel vehicle operating with four different ethanol-gasoline blends E6, 35% ethanol (E35), 65% ethanol (E65) and 85% ethanol (E85) was evaluated to understand fuel effects. Changes in vehicle operating temperature, which included the combustion air temperature, over the ranges of 60 to 85°F showed no clear impact on fine particle emissions. Likewise, no significant changes in particle number or particle size distributions were observed between CNG and E6 fuels. However, tests with the flex fuel vehicle, which were able to examine higher ethanol concentrations in the fuel showed large decreases in particle number emissions as ethanol levels increased to E65 and E85.