Prior to the RFS rule, industry has used an equation for standardization of ethanol volumes that carries the correction factor out to 5 digits rather than 7 digits as in the formula given in the RFS rule at 80.1126(d)(7)(i). Will use of the equation curre

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Because the difference between the five-digit and seven-digit factors is extremely small, regulated parties may find that it makes no practical difference whether they use the shorter factor for batches of a certain size . If it makes no difference in compliance calculations, you may wish to use the shorter factor for convenience.

In any enforcement proceedings, however, EPA will use the specified seven-digit factor to verify compliance. We believe that using the 5 digit factor (0.00063) rather than the 7 digit factor in the regulations (0.0006301) will not result in an substantial difference it the number of whole gallons assigned to a batch of renewable fuel, and, therefore, may be used to determine the volume of a batch under section 80.1126(d)(7).

This Question and Answer was originally posted at: Questions and Answers on the Renewable Fuel Standard Program (PDF) (59 pp, 228 K, EPA420-F-08-006, April 2008, About PDF)