Clearing the Air on E15 and Smog

by Geoff Cooper (Renewable Fuels Association/Ethanol Producer Magazine) ... In 2017 congressional testimony, Dr. Janet Yanowitz of EcoEngineering Inc., an environmental consulting firm, reviewed the existing scientific literature on E15’s emissions, concluding that “the available emissions test data indicates that replacing E10 with an E15 of the same vapor pressure will cause a slight decrease in emissions of ozone-forming organic compounds and carbon monoxide, and no change in NOx.” Smog is created when ozone combines with particle pollution and other gases.

More recently, researchers at the University of California-Riverside tested 20 vehicles and found that E15 reduced particle pollution, toxic gases and ground-level ozone. In fact, they report, E15 cut the potential for ground-level ozone formation by 10 to 15 percent compared to regular gasoline (i.e., E10) in most vehicles.

Why are reporters confused on this issue? Because even though E15 has a vapor pressure that is 1-2 percent lower than today’s regular E10 gasoline, EPA regulations (both prior to 2019, and again after the oil industry won a lawsuit against EPA last year) require E15 to meet a vapor pressure limitation that is 10 percent lower than the limit applied to E10. This more restrictive standard for E15 is the product of antiquated regulations that predated E15’s introduction by about 25 years. At that time, policymakers and regulators couldn’t fathom that gasoline would ever contain more than 10 percent ethanol.

The recent misreporting on E15 and smog also belies ethanol’s long history as a solution to pollution, especially in urban settings. In response to worsening air quality problems in large urban areas, the Clean Air Act Amendments of 1990 directed EPA to develop a “reformulated gasoline” (RFG) program to reduce smog. Ethanol was a key ingredient in RFG because its high oxygen content helped gasoline burn more cleanly, and it displaced certain gasoline components that caused smog-forming emissions.

The RFG program has been a clear and resounding success: Many of the urban areas with major smog problems in the 1990s and early 2000s today have cleaner air that meets or exceeds federal air quality standards. In fact, EPA data show ground-level ozone concentrations are down nearly 30 percent since RFG began entering the market in the mid-1990s.

Of course, ethanol also provides an additional, related benefit: lowering greenhouse gas emissions. According to the Department of Energy’s Argonne National Laboratory, typical corn ethanol provides a 44 percent GHG savings compared to gasoline. Similarly, researchers from Harvard, MIT and Tufts concluded that today’s corn ethanol offers an average GHG reduction of 46 percent versus gasoline. And E15 cuts GHG emissions by about 2.5 percent compared to regular E10 gasoline and nearly 7.5 percent compared to gasoline without any ethanol added.

It is important to note that these GHG estimates account for all emissions related to the entire ethanol production lifecycle process, including fertilizer, energy use and emissions for corn farming, as well as possible soil and vegetation carbon losses from hypothetical cropland expansion. READ MORE