Biodiesel produced from soybean oil, canola oil, yellow grease, and beef tallow was tested in two heavy-duty engines. The biodiesels were tested neat and as 20% by volume blends with a 15 ppm sulfur petroleumderived diesel fuel. The test engines were the following: Reduction in PM emissions and increase in NO x emissions were observed for all biodiesels in all engines, confirming observations made in older engines. On average PM was reduced by 25% and NO x increased by 3% for the two engines tested for a variety of B20 blends. These changes are slightly larger in magnitude, but in the same range as observed in older engines. The cetane improver 2-ethyl hexyl nitrate was shown to have no measurable effect on NO x emissions from B20 in these engines, in contrast to observations reported for older engines. The effect of intake air humidity on NO x emissions from the Cummins ISB was quantified. The CFR NO x /humidity correction factor was shown to be valid for an engine equipped with EGR, operating at 1700 m above sea level, and operating on conventional or biodiesel.

online ordering: http://www.ntis.gov/ordering.htm Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste Executive SummaryBiodiesel is a fuel-blending component produced from vegetable oils, animal fats, or waste grease by reaction with methanol or ethanol to produce methyl or ethyl esters. Pure biodiesel contains approximately 10 weight percent oxygen. It is typically blended with petroleum diesel at levels up to 20% (B20). The presence of oxygen in the fuel leads to a reduction in emissions of hydrocarbons (HC) and toxic compounds, carbon monoxide (CO), and particulate matter (PM) when biodiesel blends are burned in diesel engines. These reductions are robust and have been observed in numerous engine and vehicle testing studies. Engine dynamometer studies reviewed in a 2002 report from EPA show a 2% increase in oxides of nitrogen (NO x ) emissions for B20. This perceived small increase in NO x is leading some state regulatory agencies to consider banning the use of biodiesel. Therefore, the issue of NO x emissions is potentially a significant barrier to expansion of biodiesel markets.The objective of this study was to determine if testing entire vehicles, vs. just the engines, on a heavyduty chassis dynamometer provides a better, more realistic measurement of the impact of B20 on regulated pollutant emissions. This report also documents completion of the National Renewable Energy Laboratory We reviewed more recently published engine testing studies (Table 3) and found an average change in NO x for all recent B20 studies of -0.6%±2.0% (95% confidence intervals are used throughout this report). Restricting the average to recent studies of B20 with soy biodiesel yields an average NO x impact of 0.1%±2.7%. The EPA review also includes summary of a smaller vehicle testing dataset that shows no significant impact of biodiesel on NO x . We reviewed several recently published vehicle (chassis) testing studies (Tables 4 and 5) and found an average change in NO x of 1.2%±2.9% for B20 from soy-derived biodiesel. In addition, we reviewed three portable emissions measurement system (PEMS) studies that do not find NO x to increase.Eight heavy-duty diesel vehicles were tested, including three transit buses, two school buses, two Class 8 trucks, and one motor coach. Four met the 1998 heavy-duty emissions requirement of 4 g/bhp-h NO x and four met the 2004 limit of 2.5 g/bhp-h NO x +HC. Driving cycles that simulate both urban and freeway driving were employed. Each vehicle was tested on a petroleum-derived diesel fuel and on a 20 volume percent blend of that fuel with soy-derived biodiesel. On average B20 caused PM and CO emissions to be reduced by 16% to 17% and HC emissions to be reduced by 12% relative to petroleum diesel. Emissions of these three pollutants nearly always went down, the exception being a vehicle equipped with a diesel particle filter that showed very low emissions of PM, CO, and HC; and there was no significant change in emissions for blending of B20. The NO x impact of B20 va...

Tests of ultra-low sulfur diesel blended with soy-biodiesel at 5% and 20% were conducted using a 2002 model year Cummins ISB engine (with exhaust gas recirculation) that had been retrofitted with a passively regenerated catalyzed diesel particulate filter (DPF). Results show that on average, the DPF balance point temperature (BPT) is 45°C and 112°C lower for B20 blends and neat biodiesel, respectively, than for 2007 certification diesel fuel.Biodiesel causes a measurable increase in regeneration rate at a fixed steady-state condition, even at the 5% blending level. The data show no significant differences in NO x emissions for these fuels at the steady-state regeneration conditions, suggesting that differences in soot reactivity are responsible for the observed differences in BPT and regeneration rate. Soot from the various fuels was characterized by determining the fuel and lubricant fractions of the soluble organic fraction, elemental and organic carbon content, amorphous carbon/graphitic carbon ratio by Raman spectroscopy, carbon/oxygen ratio by energy dispersive x-ray analysis, and reactivity in oxygen by TGA. Results indicate a much more disordered soot structure, containing higher levels of oxygen as biodiesel is blended into the diesel fuel. The soot produced from biodiesel and blends is much more reactive in oxygen than diesel soot. It is concluded that the lower balance point temperature and higher DPF regeneration rates for biodiesel containing fuels are observed because the soot generated from these blends is more reactive.

Nine identical 40-ft. transit buses were operated on B20 and diesel for a period of two years -five of the buses operated exclusively on B20 (20% biodiesel blend) and the other four on petroleum diesel. The buses were model year 2000 Orion V equipped with Cummins ISM engines, and all operated on the same bus route. Each bus accumulated about 100,000 miles over the course of the study. B20 buses were compared to the petroleum diesel buses in terms of fuel economy, vehicle maintenance cost, road calls, and emissions. There was no difference between the on-road average fuel economy of the two groups (4.41 mpg) based on the inuse data, however laboratory testing revealed a nearly 2% reduction in fuel economy for the B20 vehicles. Engine and fuel system related maintenance costs were nearly identical for the two groups until the final month of the study. Component replacements near the end of the study on one B20 bus caused average maintenance costs to be higher for the B20 group ($0.07 vs. $0.05 per mile). However, engine and fuel system maintenance costs varied widely from bus-to-bus so the $0.02 per mile average difference between the two groups is not statistically significant. There was no significant difference in miles between road calls. Analysis of B20 samples during the study period revealed early problems with fuel blending. There also were occasional fuel filter plugging events for the B20-fueled buses that were likely caused by out of specification biodiesel, however the exact cause could not be conclusively determined. Oil analysis results indicate no additional wear metals from the use of B20, with similar rates of TBN and ZDDP decay. Soot levels in the lubricant were significantly lower for the B20 vehicles. Laboratory chassis emissions tests comparing the in-use B20 and petroleum diesel on the CSHVC cycle showed reductions in all measured pollutants, including a reduction in nitrogen oxides.

The presence of nitro-polycyclic aromatic hydrocarbons (NPAHs) in diesel fuel emissions has been studied for a number of years predominantly because of their contribution to the overall health and environmental risks associated with these emissions. Electron monochromator-mass spectrometry (EM-MS) is a highly selective and sensitive method for detection of NPAHs in complex matrixes, such as diesel emissions. Here, EM-MS was used to compare the levels of NPAHs in fuel emissions from conventional (petroleum) diesel, ultra-low sulfur/low-aromatic content diesel, Fischer-Tropsch synthetic diesel, and conventional diesel/synthetic diesel blend. The largest quantities of NPAHs were detected in the conventional diesel fuel emissions, while the ultra-low sulfur diesel and synthetic diesel fuel demonstrated a more than 50% reduction of NPAH quantities when compared to the conventional diesel fuel emissions. The emissions from the blend of conventional diesel with 30% synthetic diesel fuel also demonstrated a more than 30% reduction of the NPAH content when compared to the conventional diesel fuel emissions. In addition, a correlation was made between the aromatic content of the different fuel types and NPAH quantities and between the nitrogen oxides emissions from the different fuel types and NPAH quantities. The EM-MS system demonstrated high selectivity and sensitivity for detection of the NPAHs in the emissions with minimal sample cleanup required.