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Temperature and driving cycle significantly affect semivolatile organic compound emissions from diesel trucks
Citation:
Hays, M., BJ George, I. George, R. Snow, J. Faircloth, T. Long, R. Baldauf, AND W. Preston. Temperature and driving cycle significantly affect semivolatile organic compound emissions from diesel trucks. Presented at International Emissions Inventory Conference, Baltimore, MD, August 14 - 18, 2017.
Impact/Purpose:
Replacement of petroleum diesel with biodiesel in vehicles generally reduces pollutant emissions, including particulate matter (PM), CO, elemental carbon (EC), polycyclic aromatic hydrocarbons (PAH), volatile organic compounds (VOC), and total hydrocarbons (THC). However, reductions are not always realized and their extent varies by pollutant and is strongly influenced by vehicle design and age, engine technology and operating conditions, and biodiesel fuel type among other variables. The objective of this study is to examine the impacts of biodiesel on these emissions. These data will be applied to dispersion and air quality models that inform policy makers about the risks associated with backsliding due to the replacement of diesel with biodiesel.
Description:
The U.S. produces roughly 5 billion liters of biodiesel per year currently. Use of biodiesel is projected to increase owing to the potential economic, energy, and environmental benefits. Despite these benefits, there is public health concern about the possible direct and indirect environmental and air quality impacts due to biofuel use. In fact, national biofuel policy includes an anti-backsliding provision concerning the risk of negative or adverse air quality impacts following implementation of the Renewable Fuel Standard (RFS). The present study examines the effects of fuel (an ultra-low sulfur diesel [ULSD] versus a 20% v/v soy-based biodiesel—80% v/v petroleum blend [B20]), temperature, load, vehicle, driving cycle, and regeneration technology on semivolatile organic compound (SVOC) emissions from diesel trucks. The study is performed using chassis dynamometer facilities that support low temperature operation (-7 °C versus 22 °C) and heavy loads up to 12,000 kg. Gas- and particle-phase SVOC emissions collected using traditional filter and polyurethane foam sampling media are analyzed using advanced gas chromatograpy-mass spectroscopy methods. Carbon analysis is performed using a thermal-optical technique. Interestingly, replacing ultra-low sulfur diesel with B20 did not significantly influence SVOC emissions. However, both low temperature and vehicle cold-starts significantly increase SVOCs in the truck exhaust. Vehicle regeneration technology did influence emissions in real-time; although, regeneration effects went unresolved in bulk samples using chromatography techniques. Finally, our emission rates will be compared with national inventory data, which currently show that individual SVOC emissions from diesel trucks can vary over several orders of magnitude.