NERL Research Abstracts KPA's Niilioiiiil Kxposiirc Kosonrch Lsihomlorv (il'UA (ioiil I - Clean Air A I'M #529 Significant Research Findings Emission Studies From Vehicles Using New Fuels Scientific Problem and Policy Issues The Clean Air Act of 1990 mandates the use of oxygenated fuels for areas of the United States in violation of carbon monoxide (CO) and ozone ambient air standards. The oxygenate requirement is achieved in most affected areas by mixing methyl tertiary-butyl ether (MTBE) with gasoline at levels needed to attain either the 2.0 or 2.7 percent oxygen requirements for ozone or CO non- compliant areas, respectively. This study characterizes emissions from vehicles operating on MTBE and ethanol blends at lower temperatures (e.g., 20 °F to -20 °F). The low temperature study is relevant because CO, which is largely a winter-time problem, is caused by high emissions from gasoline cars operating at low temperatures. The fact that MTBE is being phased out of gasoline diminishes the important of this portion of the study. However, data from the study can be used to determine the impact of replacement fuels on ambient air toxic levels. Research The study's primary objective is to determine low-temperature emission factors Approach for pollutants emitted from cars using MTBE- and ethanol-gasoline blends. The emission factors are inputs to models used to predict resultant ambient air concentrations or exposure levels. The tests are carried out at temperatures ranging from 75 °F to -20 °F using a chassis dynamometer located inside a large temperature-controlled enclosure. Emissions are measured with the engines running normally, and with two common engine malfunctions imposed, a faulty oxygen sensor and faulty exhaust gas recycle (EGR) valve. Each malfunction is examined separately. The effect of driving cycle is also examined by employing a high speed, high acceleration cycle in addition to the standard emission test cycle. The higher speed driving cycle is more representative of the way vehicles are driven in many urban areas. The emissions measured included regulated pollutants (hydrocarbons [HCs], carbon monoxide [CO], nitrogen oxides [NOx]), carbon dioxide (C02), particulate matter (PM2 5 and PM10), and gaseous air toxic compounds (benzene, 1,3-butadiene, formaldehyde, and acetaldehyde). National Exposure Research Laboratory - September 2000 ------- Results and Results indicate that emissions, with the exceptions of nitrogen oxides and Implications aldehydes, increase as test temperature is reduced. This is true with both oxygenated and non-oxygenated gasoline. In many cases, these increases are large (multi-fold), including increases in emissions of two air toxic compounds, benzene and 1,3-butadiene. Even larger increases in these emissions (except for NOx and aldehyde) occurred when the oxygen sensor was disabled. Five- fold increases of both benzene and 1,3-butadiene emission rates at the lower test temperatures are typical. Generally, the MTBE blend has lower emissions, compared to the baseline gasoline. Benzene emissions are often reduced more than 50 percent because the MTBE blend has about one-half the benzene content of the baseline fuel. The effect on aldehyde emissions was less clear, with an MTBE benefit appearing to exist with one car but not another. Vehicle test data indicates that fuels with 10% ethanol (E-10) reduces emissions of HCs and CO at winter test temperatures when compared with base fuel emissions. The use E-10 fuel has the adverse effect of increasing acetaldehyde emissions by as much as 8 times under some test conditions. Benzene, formaldehyde, and 1,3-butadiene has shown both increases and decreases in emissions when using E-10 fuels. It was also noted that emissions of PM25 approximately equaled those of PM10. This suggests that particulate matter emissions from gasoline engines consists mainly of particles having a diameters less than 2.5 micrometers. Research Collaboration and Publications This research was conducted in-house by the National Exposure Research Laboratory. Stump, F., Knapp, K., Ray, W. Influence of oxygenated fuels on the emissions from three pre- 1985 light-duty passenger vehicles. Journal of the Air & Waste Management Association 44: 781-786, 1994. Stump, F., Knapp, K., Ray, W., Influence of ethanol-blended fuels on the emissions from three pre-1985 light-duty passenger vehicles. Journal of the Air & Waste Management Association 46: 1149-1161, 1996. Stump, F., Tejada, S., Black, F., Ray, W., USEPA, Crews, William, Davis, Radford, ManTech Environmental. Compound Injection to Assure the Performance of Motor Vehicle Emissions Sampling Systems. Society of Automotive Engineers, 961118, May 1996. Stump, F., Tejada, S., Dropkin, D., USEPA, Loomis, C. CAVTC: Characterization of Emissions from Malfunctioning Vehicles Fueled with Reformulated Gasoline-MTBE Fuel—Part I. Project report submitted for NERL clearance. Future Research A study currently in progress examines emissions from an ethanol blend in a manner similar to the MTBE study. This study and a report will be completed in FY01. Preliminary results are not available. National Exposure Research Laboratory - September 2000 ------- Questions concerning NERL's mobile source emission studies of new fuels and fuel additives should be directed to: Fred Stump U.S. Environmental Protection Agency National Exposure Research Laboratory (MD-47) Research Triangle Park, NC 27711 Phone: (919)541-1457 E-mail: stump.fired@epa.gov National Exposure Research Laboratory - September 2000 ------- |