Capturing carbon dioxide in the Earth's atmosphere makes little sense compared to dealing with greenhouse gas sources such as coal and natural gas power plants, according to a new report. But direct air capture might prove more cost-effective down the road.

Scrubbing CO2 from the smokestack of a coal power plant costs about $80 per metric ton, whereas removing a metric ton of CO2 from the atmosphere might cost an estimated $600 under optimistic scenarios. That's because the CO2 emissions from power plants have 300 times greater concentration than the CO2 in the atmosphere.

"That's the stuff to capture before we talk about capturing CO2 from the air," said Robert Socolow, co-director of The Carbon Mitigation Initiative at Princeton University and co-chairman of the new study.

Direct air capture might become more economically attractive when dealing with less centralized CO2 sources such as cars and home furnaces, Socolow explained. But tackling emissions from fossil fuel-burning power plants is a much cheaper way to remove CO2 that might otherwise help drive climate change.

"It's hard to separate technological feasibility from cost," Socolow told InnovationNewsDaily. "We remove CO2 from submarines and the space station, but it's expensive."

A direct air capture system that could offset the emissions of a 1,000-megawatt coal power plant would require close to 19 miles (30 km) of equipment that stood 33 feet tall (10 m). That does not even include the added challenge of CO2 storage following air capture, according to the report by the American Physical Society.

But Socolow said that the report did not rule out research on direct air capture, even if deployment still looks several decades away. Besides, the geoengineering tactic might end up using less land than, say, relying on mass reforestation by CO2-absorbing trees.

Socolow suggested that more such reports are needed for the different geoengineering methods that have been proposed to combat climate change. For now, he pointed to better energy efficiency, boosting renewable energy sources and cleaning fossil fuel power plants as the more hopeful tactics in the short term.

"All in all, the U.S. [economy] is growing faster than the carbon dioxide is going up," Socolow said. "We are being more [energy and carbon] efficient as we get richer."