WHITE PAPER MARCH 2021 AIR QUALITY IMPACTS OF BIODIESEL IN THE UNITED STATES Jane O’Malley, Stephanie Searle www.theicct.org
[email protected] twitter @theicct BEIJING | BERLIN | SAN FRANCISCO | SÃO PAULO | WASHINGTON ACKNOWLEDGMENTS This study was generously funded by the David and Lucile Packard Foundation and the Norwegian Agency for Development Cooperation. International Council on Clean Transportation 1500 K Street NW, Suite 650, Washington, DC 20005
[email protected] | www.theicct.org | @TheICCT © 2021 International Council on Clean Transportation EXECUTIVE SUMMARY Since the passage of the Clean Air Act in 1970, the U.S. Environmental Protection Agency (EPA) has enacted standards to reduce vehicle exhaust emissions. These standards set emission limits for pollutants that contribute to poor air quality and associated health risks, including nitrous oxide (NOx), hydrocarbons (HC), carbon monoxide (CO), and particulate matter (PM). Although the majority of the on-road vehicle fleet in the United States is fueled by gasoline, diesel combustion makes up an overwhelming share of vehicle air pollution emissions. Air pollution emissions can be affected by blending biodiesel, composed of fatty acid methyl ester (FAME), into diesel fuel. Biodiesel increases the efficiency of fuel combustion due to its high oxygen content and high cetane number. Studies have found that biodiesel combustion results in lower emissions of PM, CO, and HC, likely for this reason. However, studies have consistently found that biodiesel blending increases NOx formation. Industry analysts, academic researchers, and government regulators have conducted extensive study on the emissions impacts of biodiesel blending over the last thirty years. The EPA concluded in a 2002 report that, on the whole, biodiesel combustion does not worsen air quality compared to conventional diesel and reaffirmed that conclusion in a 2020 proposal and subsequent rulemaking.