Regulated Emissions from Biodiesel Tested in Heavy-Duty Engines Meeting 2004 Emission Standards

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 petroleum-derived diesel fuel. The test engines were a 2002 Cummins ISB and 2003 DDC Series 60. Both engines met the 2004 U.S. emission standard of 2.5 g/bhp-h NO_x+HC (3.35 g/kW-h) and utilized exhaust gas recirculation (EGR). All emission tests employed the heavy-duty transient procedure as specified in the U.S. Code of Federal Regulations. 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.