A report demonstrates that in the absence of oxygenates, the use of aromatics in gasoline will increase, resulting in increased ambient ozone and particulate matter. "The extent to which aromatics are used as a replacement for oxygenates is critical because aromatics have decidedly negative air quality impacts compared to oxygenates, and will result in increased ozone and particulate levels," the report states, noting Congress included the oxygen requirement in the Clean Air Act Amendments of 1990 specifically to assure reductions in the use of aromatics.

The study concludes refiners will not use ethanol in any significant volume in either Petroleum Administration for Defense District I or Petroleum Administration for Defense District III if the oxygen requirement is removed.  "The study teaches that refiners will increase aromatics use by reforming to the maximum allowable level to satisfy octane requirements and only then purchase octane blendstocks," the report states.

"The PACE  analysis demonstrates that if the oxygen requirement is lifted, refiners will most likely respond by replacing the lost octane and volume of MTBE with increased aromatics.  Such a conclusion would have deleterious impacts on both ozone air quality and fine particulate formation," says the letter.  "Forfeiting the exhaust hydrocarbon, carbon monoxide and fine particulate benefits of oxygenates is clearly counterproductive if reducing urban ozone and fine particulate formation is the goal.  The California Air Resources Board reformulated gasoline oxygen content waiver request must be denied."
 
The report, Analysis and Refinery Implications of Gasoline Aromatic Limits in 2005 and the Impact on Ethanol Demand, was completed by PACE Consultants for the Renewable Fuels Association and the National Corn Growers Association.