There is evidence that the degree of hydrocarbon unsaturation in gasoline, including the contribution from aromatic compounds, is proportional to particulate matter (PM) emissions. The use of ethanol blends would be expected to dilute unsaturated hydrocarbons in fuels in proportion to blending levels, and thereby reduce PM formation. However, recent data from the U.S. EPA’s Office of Transportation and Air Quality suggest that ethanol’s effects on PM emissions are complex and that, at least for certain vehicles, ethanol augments the effect of unsaturation in terms of production of PM. Given that the Energy Policy Act of 2005 mandates the use of increasing amounts of renewable fuels in the coming years, the most recent data on unsaturation and PM emissions raise a potentially significant issue. Additionally, very little is known about the potential impact of such emissions — including primary PM — on secondary organic aerosol formation, which is an important, though not well characterized, issue regarding population-wide PM exposure.
In view of the importance of the above-mentioned issues, and given the many uncertainties, HEI held a workshop on December 8, 2016, with the goal of providing an overview of research on the effects of fuel composition on PM (including both primary emissions and secondary PM formation). Introductory presentations included overviews of regulatory issues in the US and Europe, of engine/vehicle parameters, and of fuel formulation. Other speakers discussed results of studies on the effects of aromatics and other high molecular weight hydrocarbons as well as ethanol blending, along with the effects of other fuel parameters, on emissions from both traditional gasoline engines as well gasoline direct injection engines. Results of laboratory studies (including the EPAct) and real world studies were presented and discussed. The workshop ended with a discussion of research approaches and research needs, within the policy context. The workshop was attended by approximately 45 researchers and government and industry representatives.
An Executive Summary of the workshop is now availble (see Program Downloads in the sidebar).
Planning Committee: Allen Robinson, Robert Harley, Maria Costantini, and Rashid Shaikh