Pressure builds on EPA to back down on ethanol emissions, as Society of Automotive Engineers issues stunning rebuke

November 5, 2014 |

epaIn Washington, what has been described within the industry as “The growing movement to call out the U.S. Environmental Protection Agency for its ethanol emissions testing procedures” picked up support today as a new study from the Society of Automotive Engineers (SAE) called the agency’s approach flawed.

In the paper “Issues with T50 and T90 as Match Criteria for Ethanol-Gasoline Blends,” authors James E. Anderson, Timothy J. Wallington (both of Ford Motor Company), Robert A. Stein (AVL Powertrain Engineering), and William M. Studzinski (General Motors) write that: “The purpose of this paper is to illustrate that exclusive use of a match blending approach has fundamental flaws.”

The authors add:

“For ethanol-gasoline blends, higher boiling-point hydrocarbons must be added to match T50 and T90 with fuels having less ethanol. The degradation of emissions which can result is primarily due to the added hydrocarbons, but has often been incorrectly attributed to the ethanol. Studies to evaluate the effects of ethanol should be conducted by adjusting the blendstock only as necessary to satisfy ASTM D4814 requirements. Blending ethanol at up to 30%v with an E10 blendstock should generally require only minimal changes in composition to meet ASTM D4814.”

Splash vs match-blending

In “splash” blending the blendstock is fixed, ethanol-gasoline blend compositions are clearly defined, and effects on emissions are relatively straightforward to interpret. In “match” blending the blendstock composition is modified for each ethanol-gasoline blend to match one or more fuel properties. The effects on emissions depend on which fuel properties are matched and what modifications are made, making trends difficult to interpret.

For typical gasolines without ethanol, the distillation profile is a smooth, roughly linear relationship of temperature vs. percent fuel distilled. Hence the use of three points on the curve (T10, T50, and T90, defined as the 10%v, 50%v, and 90%v evaporated temperatures) has been sufficient to define their volatility-related behavior in engines. These parameters are commonly “matched” in studies intended to evaluate fuel composition effects on emissions.

Why does it matter?

Higher ethanol blends are not technically feasible if the resulting fuels do not meet emission standards — and also the current model contributes towards painting a picture that ethanol blending can lead to higher emissions.

Industry reaction

Steven VanderGriend, Director of the Urban Air Initiative Technical Committee, observed: “SAE Papers are technical in nature and are highly regarded and peer reviewed. According to this is critical to the argument UAI has made that splash blending higher volumes of ethanol on to finished E10 not only fails to raise any emissions but serves to improve emissions by diluting sulfur and aromatics, along with the current non-regulated ultrafine particulates. Also, by using ethanol’s octane potential, the greatest CO2 and mileage benefits can be achieved by the auto industry.

“This paper can serve as an important tool to correct the MOVES (Motor Vehicle Emissions Simulator) model that EPA requires states to use when estimating air quality impacts of fuels,” said VanderGriend. “As an independent source, the auto industry experts who were involved in this study are validating the concerns we have had for quite some time now.”

“In fact we are very excited with regard to the conclusion they reached that studies to evaluate the effects of ethanol should be conducted by adjusting the blendstock only as necessary to satisfy ASTM requirements. Blending ethanol at up to 30% volume with an E10 blendstock should generally require no change in composition to meet ASTM D4814.”

The Urban Air Initiative and the Energy Future Coalition have provided data to EPA supporting the use of E30 as a low carbon, high octane substitute for toxic aromatics in gasoline.

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