Oregon's program to reduce carbon emissions from cars, trucks and buses could soon provide a financial boost to light rail, street cars and even electric bus programs in two of the state's largest cities.

Officials are considering allowing fuel producers to meet the state's low-carbon fuel mandate by pumping money into electricity-driven transit systems -- even if those systems don't add lines or expand service.

The Department of Environmental Quality plans to consider new rules this fall that could award carbon reduction credits to new -- and perhaps existing -- light rail, street car and electric bus programs. The Portland metro area and Eugene are the only communities with existing transit systems that could qualify for the potential perk.

California, which already allows electric transit systems to earn credits in its low-carbon fuels program, awards the carbon offsets to both new and existing systems, California Air Resources Board spokesman Dave Clegern said Friday.

The Oregon transit districts could turn around and sell those credits to the companies that import gas and diesel into Oregon. Those firms are required by the state's low-carbon fuels law to lower the carbon intensity of fuels by 10 percent over a decade by blending in biofuels or purchasing the carbon offset credits. Carbon intensity refers to all emissions associated with a fuel, from extraction or generation and transport, through consumption.

Money from the sales of carbon credits could help the transit districts replace some of the millions of dollars they raised during the last decade through state energy tax credit programs that ended in the 2015 tax year, although it's not clear how much money the carbon credits might generate. The tax credits issued by the Oregon Department of Energy were available to transit agencies to cover ongoing operations costs, not just service expansions or new investments.

The Department of Energy issued $7.3 million in various energy tax credits to TriMet since 2009, according to state data obtained by The Oregonian/OregonLive. Since TriMet is a government agency and does not owe taxes, it sold the credits for a reported total of $5.4 million to businesses and individuals who wanted to lower their tax bills. During the same time period, the state issued $1.9 million worth of energy tax credits to Lane Transit District, which sold the credits for $1.4 million.

If the Department of Environmental Quality allows owners of existing light rail and other electric-powered transit and equipment to rack up carbon credits, it could further transform Oregon's low-carbon fuels standard from an effort to achieve new carbon emissions reductions to a program that subsidizes existing alternative fuels infrastructure and transit operations. The program already allows owners of existing alternative fueling systems such as electric car charging stations to generate credits as if they are creating new reductions in the state's carbon emissions.

Mary Fetsch, a spokeswoman for TriMet, said the agency would be interested in participating if the Department of Environmental Quality allows light rail, street cars and electric buses to generate credits in the low-carbon fuels program. TriMet just received a $3.4 million federal grant to purchase four battery-powered electric buses this summer.

Fetsch said the state should allow transit districts to earn carbon reduction credits for their existing electric trains and buses, but she was unable to explain how that would meet goal of the low-carbon fuels program to reduce carbon intensity in fuels by 10 percent over a decade.

"If you count current transit service which delivers on reducing carbon generation and emissions, that would recognize that we are already contributing," Fetsch said.

Cory-Ann Wind, an air quality manager for the Department of Environmental Quality who works on implementation of the low-carbon fuels program, said it's possible for existing electric street cars, light rail and car charging stations to count towards the 10 percent reduction in carbon emissions because that goal was based on the assumption that none of those alternative transportation options existed at the start of the program.

Instead, the Department of Environmental Quality calculated the 2015 baseline for the program based on the idea that Oregon's transportation systems -- from cars to buses -- were all running on gasoline or diesel.

Wind said she hopes to hold the first meeting to consider the program expansion, which could also open up credit generation to truck stop electrification, electric forklifts and refrigeration units, in September or October. That rulemaking process will also cover additional measures to contain the cost of the low-carbon fuel standard, such as following California's lead to create a carbon credit clearance market.

Under a credit clearance system, fuel importers who are unable to purchase the carbon credits they need to comply with state law at the end of the year could ask the Department of Environmental Quality to help them find and purchase credits. If the state located entities holding credits, they would be required to sell the credits at a maximum price set in state law. This would allow the state to cap the cost of the program to consumers, Wind said.

As the state's largest transit district, TriMet likely has the most to gain from a potential expansion of which entities can generate low-carbon fuels credits. It is also the transit agency most closely involved in the concept.

Although Wind said the idea to include electric transit systems stemmed from California's 2015 decision to make a similar change in its program, TriMet was also in talks with the Department of Environmental Quality about the idea since at least last year, said Dan Bower, executive director of Portland Streetcar, Inc. Bower learned of the concept when a TriMet employee suggested he contact the Department of Environmental Quality for more information.

Bower did not know enough about the carbon credit concept to say whether it would make sense for Portland Streetcar Inc. to participate, but he said the system already provides environmental benefits.

"Our electrified system is proving a much cleaner solution for 15,000 trips a day than the automobile," Bower said.

Meanwhile, Lane Transit District's government relations manager Edward McGlone said the agency hadn't been informed the Department of Environmental Quality was considering the idea. "We haven't been in touch with DEQ about it," McGlone said. "We would be interested in the opportunity, but we haven't looked at it yet." The district already purchased five electric buses it expects to arrive this fall and plans to order an additional five buses soon, with most of the cost for both purchases covered by federal grants.

-- Hillary Borrud

@hillaryborrud