WASHINGTON - When scientists with the National Academy of Sciences went to figure out how to reduce the dangerously high levels of carbon dioxide in the earth’s atmosphere, potential solutions ranged from the simple (plant more forests) to the difficult (develop fuels from grass clippings) to the politically unfeasible (replace beach towns and shipping ports with mangrove swamps).

But it was the most fantastical they found themselves coming back to again and again: Build tens of thousands of what are essentially giant vacuum cleaners and locate them around the world to filter out the carbon dioxide in the earth’s atmosphere and pump it underground.

Two months after the National Academy released a report on their findings, it’s an idea that is gaining increasing traction in Washington, where the issue of climate change and what to do about it has been a source of endless debate since the problem first gained worldwide attention in the 1980s.

Four bipartisan bills are moving through Congress, bringing together powerful figures such as Sen. Sheldon Whitehouse, D-R.I., and Sen. John Barrasso, R-Wyo., and directing the Department of Energy to research and develop a technology scientists refer to as direct air capture. And while the costs of that technology are currently prohibitive, scientists believe that with time and government support they could come down to a level nations worldwide could afford.

“People said [direct air capture] was the absolute last resort, and the fact is it's one of the few options that’s infinitely scalable,” said said Mark Barteau, vice president for research at Texas A&M University, one of the authors of the National Academies report. “With everything there’s a learning curve. Look at how the price of solar [energy] has come down.”

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The concept of pulling carbon out of the atmosphere has captured both the imagination and the investment of oil and gas companies seeking ways to protect their business as efforts to slow climate change aim to dramatically reduce, if not eliminate, fossil fuels. The burning of oil, natural gas and coal produces vast amounts of carbon dioxide, which traps heat in the atmosphere and raises global temperatures.

Last month, the Houston oil company Occidental Petroleum and the Canadian firm Carbon Engineering said they would move ahead on developing a direct air capture facility in West Texas with a capacity of extracting 500 kilotons of carbon dioxide per year from the atmosphere - more than 125 times the size of the largest existing direct air capture system.

No silver bullet

To be sure, scientists said, direct air capture won’t solve the climate crisis by itself and forgo the need to reduce greenhouse gas emissions, as many in the Texas oil and gas industry and other fossil fuel producers might like to see. Rather, the degree to which emissions need to be reduced is so great that scientists are saying humanity will need a technological boost, likely through a variety of carbon removal methods.

Those methods include everything from fuel made from carbon-consuming grass to specialized equipment to plant seeds, negating farmers’ need to till fields, a practice that releases huge volumes of carbon dioxide into the atmosphere.

Time is running out, however. At the current emissions rate, the earth’s atmosphere will reach a carbon concentration of 450 parts per million in 16 years time, resulting in temperature levels 1.5 degrees Celsius above those in the early 1800s, a point at which scientists say we can expect to see severe side effects like increased flooding, widespread crop failures and the mass dying off of wildlife.

The concentration of carbon dioxide in the earth’s atmosphere already has reached 411 parts per million, said Klaus Lackner, director of the Center for Negative Carbon Emissions at Arizona State University.

“The world has to reduce CO2 emissions every year by 6 percent, and there’s no practical way we do that,” Lackner said.

For energy-state Republicans who have struggled with climate change solutions that require reducing consumption of oil and coal, direct air capture provides an opportunity to take action without a potential shock to their local economies. Houston Republican Rep. Dan Crenshaw, a co-sponsor on one of the bills supporting direct air capture, said he could foresee a day when the Department of Energy operates a carbon removal program the same way it cleans up radioactive contamination from Cold War-era nuclear weapons facilities.

“The Department of Energy subsidizes a lot of things, and there’s no reason these items couldn’t be a part of that,” he said. “There is pretty broad agreement on these methods to achieving a cleaner air, lower emission environment.”

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But support is not universal. For now, House and Senate leaders have not immediate plans to bring the legislation to the floor for a vote.

Some Republicans, still skeptical of the perils of climate change, remain reluctant to spend money on carbon capture. At the same time, some environmentalists are still considering their positions, concerned support for direct air capture would limit resources dedicated to promoting clean energy and cutting emissions.

Just the beginning

“There is a worry the government will take their eye off the ball on mitigation because there’s a technological solution on the horizon,” said John Coequyt, director of federal and international climate campaigns at the Sierra Club, the national environmental advocacy group.. “There’s a bit of growing consensus we need to look at doing all these things the same time.”

In their report, scientists at the National Academy recommended the U.S. government spend between $181 million and $240 million a year researching and developing direct air capture systems, with the goal of bringing the cost of carbon capture down to $100 per ton of carbon dioxide - a recent estimate put the cost as high as $600 a ton.

Considering the Department of Energy manages a budget of $35.5 billion, that might not sound like much. But that’s just the initial costs.

Building out out direct air capture on the scale scientists say is necessary could require tens of billions of dollars a year, depending on how quickly the United States can reduce emissions, said John Larsen, a Washington-based director with the consulting firm Rhodium Group. And while experts say the best way to pay for such an undertaking would be charge a fee or tax for greenhouse gas emissions, there is limited support for such a move among both parties in Congress.

“Climate change is one of those classic collective action problems,” Larsen said. “Right now, we have a hard time just getting started, getting the ball rolling.”

But Occidental’s announcement has spurred enthusiam that direct air capture could be a viable option. one day.

End of magical thinking

The costs of direct air capture are not where they need to be yet, scientists say. For instance, Occidental’s facility would supply its oil and gas operations, using carbon dioxide to speed up oil production - reducing its climate benefit and skewing the economic picture. But capture costs are coming down, said Barteau, the A&M professor.

“We have to stop looking for magical answers,” he said. “We have some things it’s possible to do now. They’re not free, but we need to get started.”

james.osborne@chron.com