Research Note 89-2: Topic = Quantitative Estimate of the Air Quality Impacts of Methonol Fuel Use

 California Environmental Protection Agency

Air Resources Board

 No. 89-2

May 1989


Brief Reports to the Scientific and Technical Community

 Research Division, John R. Holmes, Ph.D., Chief

P.O. Box 2815, Sacramento CA 98512

Quantitative Estimate of the Air Quality Impacts of Methanol Fuel Use

Methanol is being proposed as a clean, alternative vehicle fuel for areas having difficulty attaining air quality standards.  This study estimated air quality changes that would result from varying levels of use of methanol fuel in mobile sources in the South Coast Air Basin.  The study found that use of methanol fuel in light and heavy-duty vehicles would produce significant reductions in ambient ozone, particulate matter, nitrogen dioxide, nitric acid and peroxyacetyl nitrate.  An air quality simulation model was used to provide these estimates for the years 2000 and 2010.



Significance and Application:

Related Projects:

Since the early 1960's, the California Air Resources Board (ARB) has developed and implemented regulations to reduce emissions from motor vehicles. Despite continually adopting and updating technology forcing standards, the National Ambient Air Quality Standards will not be attained in the most polluted areas of the State in the near future, and projected increases in population and travel will further aggravate this problem. The Board and the South Coast Air Quality Management District are examining a variety of alternative fuels which show potential for significant reductions in air pollution levels. These fuels include methanol, ethanol, compressed natural gas, liquid petroleum gas, hydrogen, and electricity.

The ARB's interest in methanol as a promising alternative fuel is based upon its potentially widespread application and its low reactivity (air polluting) characteristics. Past modeling efforts to assess air quality impacts of methanol fuel use showed significant reductions in first-day maximum one-hour ozone levels in the South Coast Air Basin (SoCAB). While these results were promising, the modeling studies were criticized by reviewers concerned about the validity of some major assumptions and the emissions data used.

A three-tiered approach was used to assess the impact of methanol fuel use in the SoCAB; chemical kinetic modeling, trajectory modeling and Eulerian airshed modeling of ozone, nitrogen dioxide, nitric acid, formaldehyde, and peroxyacetyl nitrate (PAN) concentrations. In addition, particulate matter responses to methanol fuel use were estimated by using photochemical and non-photochemical modeling. Ambient concentrations of formaldehyde, methanol and benzene, under stagnation conditions, were determined by the use of linear modeling. Major findings of the study include:

  • Up to a 17 percent reduction in ozone levels could be realized by using M100 (100 percent methanol) fuel in motor vehicles. This is 77 percent of the reduction that could be achieved by eliminating vehicular source emissions completely. This result reflects, in part, the relatively small fraction of reactive organic gas emissions attributable to motor vehicles in year 2000.
  • Formaldehyde emissions and emissions from the gasoline fraction of M85 (85 percent methanol, 15 percent gasoline) would contribute significantly to ozone formation. The use of M85 would increase formaldehyde emissions (55 mg/mile vs. 15-18 mg/mile) and would provide only one-half of the reductions in ozone concentrations that could be achieved by using 100 percent methanol.
  • Overall atmosphere formaldehyde levels would not change. Reductions in formaldehyde level as a result of the lower reactivity of methanol would be offset by increased formaldehyde emissions from methanol-fueled vehicles.
  • Methanol fuel use would also reduce other pollutant concentrations. Particulate matter concentrations would decrease because methanol-fueled vehicles especially diesels. Emissions of precursors to aerosol formation and atmospheric production of particulate matter would be reduced. Concentrations of nitric acid, NO2 and PAN would also be reduced. Nitric acid and NO2 concentrations were predicted to decrease by about 28 percent. PAN concentrations were predicted to be reduced by 22 percent.

Airshed modeling for ozone concentrations in the SoCAB show that eliminating all vehicular source air polluting emissions would reduce ozone concentrations by 21 percent in the year 2000. Since achieving the National Ambient Air Quality Standards for ozone will require reductions of 80 to 90 percent additional and significant emission reductions are needed if the standards are to be attained.  Substitution of methanol or other clean burning fuels for the currently used gasoline and diesel fuel is probably the most significant step which can be taken to achieve improved air quality in the Basin.

The Air Resources Board is sponsoring a related project to estimate the air quality changes that would take place in the SoCAB, with the increased use of alternative fuels other than methanol, including natural gas, propane, hydrogen, ethanol and ethanol/gasoline blends. The same air quality model used to study methanol will be expanded to include the chemistry of compounds emitted from these alternative fuels. Results will be directly comparable to the results of the methanol-fuel study. In addition, two other related studies are currently under way. One study is investigating durable emission control systems capable of reducing formaldehyde emissions from methanol-fueled vehicles. The second study is investigating additives to improve cold-start driveability, flame luminosity, lubricity and lower flammability limits and to provide a taste deterrent for methanol used as motor vehicle fuel.

This research was conducted under contract with Carnegie Mellon University (ARB Contract No: A6-048-32). Comments or questions can be directed to the contract manager, Manjit Ahuja, by mail, FAX (916) 322-4357, e-mail, or phone (916) 323-1535.

Copies of the research report upon which this Note is based can be ordered from:

National Technical Information Service
5285 Port Royal Rd
Springfield VA 22161
Request NTIS No. PB 90115890

Title: Quantitative Estimate of the Air Quality Impacts of Methanol Fuel Use.

Authors: Armistead Russell