blends. And since exhaust VOCs are believed to have a greater propensity to form Ozone than evaporative VOCs, the greater reduction in exhaust VOCs achieved by certain ethanol RFG blends may counterbalance their greater mass of evaporative VOCs. Furthermore, because of the additional oxygen, these blends may contain less carbon monoxide than non-ethanol blends, further reducing their tendency to form ozone since carbon monoxide is a recognized precursor of ozone.

I have proposed that EPA establish a procedure to certify ethanol blends as equivalent to non-ethanol blends under section 211 (k) (4) (B) of the Clean Air Act, but EPA has so far refused to do so bemuse it is unsure clot there is an appropriate methodology for making the comparison.

I hope that the NAS Study will have a practical aim; that is, it will help to determine, in light of the best available information, the procedures (i.e., the data and analysis) by which the equivalency of two blends could be determined with a reasonable degree of certainty. To the extent that additional information or studies are necessary before such procedures can be developed or implemented, I also hope that NAS will identify the additional information and analyses which would be needed and Chat it would work with the EPA and with ocher concerned parties to ensure that it is provided.

The NAS study is critical to the implementation of the Clean Air Act in a manner that allows renewable fuels to play an important role in the reformulated gasoline program. I therefore Join EPA in urging the National Academy of Sciences to undertake this effort and I urge that it be completed at the earliest possible date. If you have any questions, please contact me or Jeff Burnam of my staff at 202-224-7443.

RGL/jbj



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement