Direct removal of CO2 from air impractical: Scientists

Removing CO2 from the air may not be a practicable way to reverse human-driven climate change.

Washington: Removing carbon dioxide (CO2) from the air physically may not be a very practicable way to reverse human-driven climate change and it would be cheaper to curb emissions, say scientists.

"We humans should not kid ourselves that we can pour all the carbon dioxide we wish into the atmosphere right now and pull it out later at little cost," said Robert Socolow, professor of mechanical and aerospace engineering at Princeton University.

Socolow co-chaired with chemist Michael Desmond a committee of 13 experts that issued this report on carbon dioxide, according to a statement of the American Physical Society.

The Socolow committee looked at technologies known as "direct air capture (DAC)", which would involve using chemicals to absorb the gas from the open air, concentrating it, and then storing it safely underground. It found that such a strategy would be far more expensive than simply preventing the emission of carbon dioxide in the first place.

Making optimistic assumptions about initial DAC technologies, the committee concluded that, from the evidence it had seen, building and operating a system would cost at least $600 per metric ton of carbon dioxide removed from the atmosphere, for a system that could work today.

Building a system big enough to compensate for the emissions of a 1,000-megawatt coal power plant would require equipment stretching 30 km. In comparison, removing CO2 from the flue gas of a coal-fired power plant would cost about $80 per tonne.

"We ought to be developing plans to bring to an end the carbon dioxide emissions at every coal and natural gas power plant on the planet," Socolow said.

Beyond using electricity more efficiently, options are to modify plants so their emissions are kept from the atmosphere or to shut them down entirely and replace them with low-carbon alternatives, he said.

Socolow noted that while the contents of the report serve as a warning against complacency, the experience of developing the report offers grounds for optimism.

"The message of hope is that smart scientists and engineers are getting more and more interested in energy and climate problems," he said.

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