TESTS SHOW LIMITS ON OXYGEN CONTENT TO BE UNWARRANTED

Results from recent testing by the Oxygenated R Fuels Association (OFA) indicate that oxygen content ceilings on gasoline for the purpose of controlling NOx emissions appear to be unwarranted. OFA Executive Director Jack Murray reported the study findings to the U.S. Environmental Protection Agency in November 1992.

Jan. 19, 1993

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Results from recent testing by the Oxygenated R Fuels Association (OFA) indicate that oxygen content ceilings on gasoline for the purpose of controlling NOx emissions appear to be unwarranted.

OFA Executive Director Jack Murray reported the study findings to the U.S. Environmental Protection Agency in November 1992.

The forum for Murray's comments was the EPA's public hearing on the administrator's proposed finding that no control or prohibition on maximum oxygen content of a winter oxygenated gasoline program is necessary under section 211(c)(4)(A) of the Clean Air Act, as amended by the Clean Air Act Amendments of 1990.

HIGH-02 FUELS TESTING

The Oxygenated Fuels Association is a broad-based technical organization of oxygenate producers, users, and technical licensors. OFA sponsored a high-oxygen test fuel as part of the EPA's Phase II reformulated gasoline testing program, designed to expand the knowledge base for fuels blended with ethers at greater than 2.7 wt % oxygen.

The result; from this testing support the position suggested by engine combustion theory-that increasing oxygen levels to greater than 2.0% does not lead to higher NO, emissions. Based on this analysis, OFA agrees with EPA that capping oxygen levels to prevent increased NO, emissions is unnecessary.

Capping oxygen also prevents the higher reduction in -volatile organic compounds and carbon monoxide (CO) emissions realized with the higher oxygen levels, sails Murray.

OFA TEST PROGRAM

Little emissions data have been available on gasolines blended with ethers to oxygen levels greater than 2.7 wt %. The OFA program has expanded the data base for gasolines containing higher oxygen levels by studying the emissions effects of using methyl tertiary butyl ether (MTBE) to increase oxygen content to approximate]N, 3.6 wt %.

OFA used 17 vehicles that were part of the EPA's 40-vehicle test program at the Automotive Testing Laboratories. The high-oxygen test fuel was blended to approximate 1995 reformulated gasoline, but at an oxygen level nearer to 3.6% (Table 1).

TEST RESULTS

The high-oxygen fuel showed decreased emissions of hydrocarbons, CO, and NOx, when compared to both industry average gasoline and EPA's MTBE-blended reformulated gasoline (Fig. 1). These reduced emissions levels were seen for both normal and high-emitter vehicle classes.

OFA's test results specifically showed that, when compared to a 1995 reformulated gasoline blended with MTBE, the higher-oxygen fuel reduced hydrocarbons by 6.3%, CO by 4.7%, and NOx by 2.4%. And perhaps more importantly, NO, emissions decreased as oxygen levels were increased from 1.8% to 3.5%.

OFA believes that these data support the EPA's findings that no state-level oxygen controls are necessary for an oxygenated gasoline program. The association has offered its study data to the EPA to be included in the development of EPA's complex model.