MODEL SHOWS FUTURE CUT IN U.S. OZONE LEVELS

A joint U.S. auto-oil industry research program says modeling shows that changing gasoline composition can reduce ozone levels for Los Angeles in 2010 and for New York City and Dallas-Fort Worth in 2005. The air quality modeling was based on vehicle emissions research data released late last year (OGJ, Dec. 24, 1990, p. 20). The effort is sponsored by the big three auto manufacturers and 14 oil companies. Sponsors said cars and small trucks account for about one third of ozone generated in the

June 24, 1991

3 min read

The air quality modeling was based on vehicle emissions research data released late last year (OGJ, Dec. 24, 1990, p. 20).

The effort is sponsored by the big three auto manufacturers and 14 oil companies.

Sponsors said cars and small trucks account for about one third of ozone generated in the three cities studied but by 2005-10 will account for only 5-9%.

"This will be due mainly to fleet turnover where newer, cleaner vehicles replace older ones and to regulations now in place which call for lower vehicle emissions, reduced gasoline volatility, and improved vehicle maintenance inspection programs.

"With the most promising fuel composition changes evaluated to date, the contribution from light duty vehicles to peak hourly ozone would be reduced by 1526%, or 1-2.5% of the estimated peak hourly ozone."

MODELING BASE

The latest modeling results are based on emissions test results from 1989 vehicles and four basic gasoline composition changes: reducing aromatic content, reducing olefin content, adding oxy-genates, and limiting the boiling range. The first phase of the auto/oil program involved vehicle emissions testing of many gasoline formulations.

The group said reducing gasoline olefin content to 5% from 20%-now averaging about 12%-reduced ozone in all three cities studied, mainly by reducing the ozone forming potential of evaporative emissions.

It said limiting the boiling range to 280 F.-now about 330 F.-also reduced ozone in all three cities. Studies are under way to identify the gasoline characteristics responsible.

And it said reducing aromatics and adding methyl tertiary butyl ether, as required by the Clean Air Act, has no clear effect on ozone formation. Tests were run using gasolines with 45% and 20% aromatics-industry average is about 32%-and with 0% and 15% (2.7 wt % oxygen) MTBE.

The group released data in February on the effects of vehicle exhaust mass emissions of reducing gasoline sulfur content to 49 ppm from 466 ppm. The industry average is 330 ppm.

Sponsors said, "These data, which were not used in the air quality modeling, show that reducing gasoline sulfur content reduces exhaust mass emissions of hydrocarbons by 16%, carbon monoxide by 13%, and nitrogen oxides by 9%. Sulfur reduction is the only gasoline property change evaluated to date that consistently reduced all three emissions."

MORE STUDIES

The auto/oil group is continuing studies on gasoline volatility oxygenates, methanol, and the cost effectiveness of changing gasoline consumption.

The $25 million second phase of the research program has begun, and will bring the cost of the program to $40 million when it is com-plete in 1993.

The second phase will develop further data on vehicle emissions, use 1993 production prototype vehicles to see if they can be recalibrated to reduce emissions with reformulated gasolines, and de-velop data on alternative fuel vehicles.