SACRAMENTO – Tens of thousands of high-emitting, 15 year old cars could be a source of air pollution credits -- through efforts such as car-scrapping programs that would retire them from the road twice as fast as normal -- to help industrial facilities comply with future anti-smog requirements, according to guidelines being developed by the state Air Resources Board (ARB).

Pollution credit also could be generated by accelerating the replacement of high-polluting, diesel-powered buses with models that run on cleaner-burning fuels such as methanol, compressed natural gas, or electricity.

The ARB is developing the guidelines for so-called "mobile credits" in response to industrial companies, utilities, environmental groups and local air pollution agencies that are looking to trade the extra cleanup of automotive emissions for credit toward meeting future rules or speeding up compliance with air quality standards.

Under the ARB's guidelines, credit can be given only for emissions that would not otherwise be regulated by existing anti-smog standards, especially difficult in California which already requires the world's cleanest running cars and fuels. Also, because of the increased number of cleaner-running cars every year due to "fleet turnover", available credits may decline over time, making them most useful for temporary industrial projects, such as major construction or drilling operations, or to make up for delayed compliance with a new rule.

With credits good for three to 12 years, however, they could offer some flexibility in planning compliance with future air quality rules. "Great care must be taken in designing these credits so that true gains are made toward cleaner air," said Jananne Sharpless, ARB chairwoman.

 "If they are properly designed, however, they can advance our progress toward meeting health standards for air quality, get some older, high-polluting cars off the road, and offer flexibility to industrial companies and others who must plan how they will meet future air pollution rules.

"As our economy faces uncertain times, these mobile credits can give sources of air pollution an added tool to work with to reduce some emissions at a cost that's competitive with the most up to date technology," she added.

 The procedures for calculating the amount of automotive emission credit that is available or the procedures for approving mobile offset proposals are to be developed by the end of the year through ARB workshops and other public forums. The ARB, however, has laid out the basic principle that will be the foundation for the credits, which are the same as those that govern offsets used in other types of air quality rules.

Besides being outside the scope of existing rules, the ARB will require these credits to be legally enforceable, measurable and their lifespan matched to the time that the credit is assigned to a project.

 In developing its guidelines, the ARB noted that the number of vehicles needed to generate a given amount of credit will vary with time, as high-polluting older models are retired from use and the emissions from the entire automotive fleet are reduced as a result of ARB emission standards.

The guidelines do, however, include the ARB's evaluation of some potential projects. The Board estimates that scrapping 540 15-year old cars, for instance, could generate 25 tons per year of hydrocarbon credit by effectively cutting short the remaining six years of their estimated road life, at a cost of $400,000. In similar fashion; the same amount of nitrogen oxide credit could be generated by added an extra 50 clean-fuel transit buses a year to replace older, higher polluting diesel models, at a cost ranging from $500,000 - $3.0 million.

In unveiling the guidelines, ARB Executive Officer, James D. Boyd, invited widespread participation in the six-month project to develop specific procedures to govern mobile offset projects. "We are offering this program to help people who have expressed an interest in added reduction of automotive emissions, and need their cooperation in designing a program that meets their needs and still protects air quality," he said.

Sharpless noted that credit or offset systems have benefitted other clean air programs, ranging from New Source Review rules that govern major industrial expansion or modernization to credits provided to car makers for early introduction of cleaner cars under the ARB's emission standards.

"Mobile credits can offer the same clean air advantages and flexibility to industrialists," she noted, "but only if they are properly designed to prevent paper promises and double-counting that would give credit for pollution that is already being cleaned up by someone else, which is why we are setting the rules now."