Four months before Oregon lawmakers return to Salem, it's already clear one Democratic priority will likely dominate the session: passing a bill to cap greenhouse gas emissions and charge some of the state's largest companies for their carbon output.

This summer, at a screening of Al Gore's latest climate change documentary, Gov. Kate Brown announced her support for passing the so-called "cap and invest" bill. She has several work groups hammering out details, from carbon pricing to potential impacts on agriculture. They are striving to have bill language ready by November.

The amount of cash it could raise would be huge by Oregon's standards. Although lawmakers, the governor's staff and interest groups are still writing the plan, a group pushing for the program estimated it would raise $1.4 billion per biennium.

They haven't specified how that huge pot of money would be spent. But lobbying to shape the bill and future rules for how to distribute it is sure to be intense.

The carbon payments would raise roughly as much as the corporate tax plan Democrats unsuccessfully pitched earlier this year to patch the state budget hole and boost K-12 education. It would have yielded an estimated $1.4 billion in 2021-23.

Yet unlike the corporate tax, Democrats could pass the climate bill without a single Republican vote. Supporters say the goal of the bill is to penalize polluters and reduce greenhouse gas emissions, not to raise revenue. They have the sign-off of the Legislature's nonpartisan legal office, where lawyers determined "cap and invest" would not require the three-fifths supermajority vote required under the state Constitution to raise taxes.

Supporters say the climate bill is already long overdue.

"This isn't about me, this is about my grandkids and their kids," said Sen. Lee Beyer, a Democrat from Springfield who sponsored several versions of a carbon cap bill in recent years. "There does become a point where the scientists tell us there'd be a point of no return. I don't think we're there, but we're going up the hill pretty fast."

Many lawmakers remain skeptical of the push to pass the bill next year, including some Democrats concerned the policy is too complex and far-reaching for a six-week legislative session. Those so-called "short sessions," held in even-numbered years since 2008, were designed for lawmakers to make technical fixes to laws and rebalance budgets. When even-numbered sessions were added, Senate President Peter Courtney and others made it clear the Legislature was supposed to reserve major policy bills for five-month sessions held in odd years.

"I'm not sure we have all the answers on a giant policy like that to act in 30 days," said Sen. Mark Hass, a Democrat from Beaverton who has led efforts to overhaul and increase corporate taxes in recent legislative sessions.

Some lawmakers are also concerned it could take energy away from work to address other problems, such as school funding, the state's long-term budget woes and public pension crisis.

"When you talk about $1.4 billion coming out of our little economy, you remove options that are necessary to other discussions and challenges we face," said Rep. Cliff Bentz, a Republican from Ontario who is working with a bipartisan group of lawmakers on solutions to precisely those problems.

In a meeting with reporters earlier this month, Brown largely avoided answering why lawmakers should pass the carbon cap before corporate tax or other revenue reforms. The governor had said after the Legislature adjourned that for a variety of reasons, she would not try to pass corporate tax changes until 2019.

Still, one of the governor's advisors acknowledged the complexity of the concept in an internal document. A memo from the governor's energy advisor Ruchi Sadhir, released in response to a public records request from The Oregonian/OregonLive, show how much work must be done to get a cap and trade package ready before the session dawns. It listed 18 broad questions that needed to be answered, including which state agency should run the program.

Although the plan is still being written, it will likely have two main components, said Brad Reed, communications director for the politically active nonprofit Renew Oregon Action Fund: a statewide mandate to lower greenhouse gas emissions 80 percent below 1990 levels by 2050 and a requirement for some of the largest polluters in the state to begin paying for their emissions. Both provisions would take effect in 2021.

Utilities and other companies that emit at least 25,000 metric tons of carbon dioxide a year would generally have to pay a penalty for every ton of emissions, according to Brad Reed, communications director for the politically active nonprofit Renew Oregon Action Fund. The group, founded in 2015 by the Oregon Environmental Council, has advocated for the carbon cap and pricing law since its inception.

In Oregon, roughly 100 businesses currently meet this emissions threshold, Reed said. The plan might include an exception for companies such as Intel that produce a high amount of emissions but could move out of state to avoid Oregon's carbon regulations. "We don't want those factories to pack up and move out of the state, because they'll just take their emissions with them," Reed said.

The state would receive the money paid by the polluters, but so far it's unclear exactly how it would be spent. Ideas include "clean transportation projects, clean energy workforce training and clean energy projects to 'de-carbonize' Oregon's economy, as well as investing in projects that prepare communities for the effects of a changing climate," according to Sadhir's memo.

It's not clear if specific requirements for the amount of carbon reduction would be placed on projects funded with the proceeds. Sadhir did not respond to an interview request. A key supporter in the Legislature, Sen. Michael Dembrow, D-Portland, wrote in an email that the plan will include requirements that projects reduce greenhouse gas emissions, train low-income Oregonians for "clean energy jobs," or serve other beneficial purposes. Helm could not be reached for comment.

If the program were to raise $700 million a year as estimated by Renew Oregon Action Fund, it would likely be a bigger bonanza for renewable energy and efficiency industries than the state's controversial business energy tax credit. The renewables industry and local governments such as TriMet and the city of Portland increasingly relied on those tax credits as they exploded in size over the last decade, so the promise of a program that would replace the now-dead tax credits would be politically popular with those sectors.

Getting the carbon cap passed is the third and final goal of the Renew Oregon Action Fund, Reed said. So far, it succeeded in getting the Legislature to make the state's low-carbon fuels law permanent in 2015 and to pass a law in 2016 to eliminate coal from the Oregon's power mix and double the state's renewable energy mandate. Reed suggested that Renew Oregon could dissolve after lawmakers and the governor get the carbon cap into law.

It has a connection to the governor's office in chief of staff Nik Blosser, who formerly served as the group's board president on a volunteer basis. Blosser declined to comment on what role he had in the governor's decision to work to pass the bill in 2018.

When Brown made her announcement that she'd support the bill at the screening of Gore's "An Inconvenient Sequel," The New Yorker reported, the event was hosted by Renew Oregon.

-- Hillary Borrud

503-294-4034; @hborrud