International News
SCRUBBING GREENHOUSE GASES
USING DIRECT AIR CAPTURE TECHNOLOGY
By Klaus Lackner
Climeworks
Climeworks , a Swiss company , has 15 plants removing carbon dioxide from the air .
Two centuries of burning fossil fuels has put more carbon dioxide into the atmosphere than nature can remove . As CO₂ builds up , it traps excess heat near Earth ’ s surface , causing global warming . There is so much CO₂ in the atmosphere today that most scenarios show that ending emissions alone won ’ t be enough to stabilise the climate – humanity will also have to remove CO₂ from the air .
The US Department of Energy has a new goal to scale up direct air capture , a technology that uses chemical reactions to capture CO₂ from air . While federal funding for carbon capture often draws criticism because some people see it as an excuse for fossil fuel use to continue , carbon removal in some form will likely still be necessary , IPCC reports show .
Technology to remove carbon mechanically is in development and operating at a very small scale , in part because current methods are prohibitively expensive and energy intensive . But new techniques are being tested that could help lower the energy demand and cost .
In this article we consider direct air capture and carbon storage , the state of the technology and where it ’ s headed in future .
WHAT IS DIRECT CARBON REMOVAL AND WHY IS IT CONSIDERED NECESSARY ? When I got interested in carbon management in the early 1990s , what drove me was the observation that carbon piles up in the environment . It takes nature thousands of years to remove that CO₂ , and we ’ re on a trajectory toward much higher CO₂ concentrations , well beyond anything humans have experienced .
Arizona State University
Humanity can ’ t afford to have increasing amounts of excess carbon floating around in the environment , so we have to get it back out . Not all emissions are from large sources , like power plants or factories , where we can capture CO₂ as it comes out . So , we need to deal with the other half of emissions – from cars , planes , taking a hot shower while your gas furnace is putting out CO₂ . That means pulling CO₂ out of the air .
HOW DIRECT AIR CAPTURE WORKS Since CO₂ mixes quickly in the air , it doesn ’ t matter where in the world the CO₂ is removed – the removal has the same impact . So , we can place direct air capture technology right where we plan to use or store the CO₂ .
The method of storage is also important . Storing CO₂ for just 60 years or 100 years isn ’ t good enough . If 100 years from now all that carbon is back in the environment , all we did was take care of ourselves , and our grandkids have to figure it out again . In the meantime , the world ’ s energy consumption is growing at about 2 % per year .
Klaus Lackner tests direct air capture technologies in his lab .
One of the complaints about direct air capture , in addition to the cost , is that it ’ s energy intensive . Can that energy use be reduced ? Two large energy uses in direct air capture are running fans to draw in air and then heating to extract the CO₂ . There are ways to reduce energy demand for both .
For example , we stumbled into a material that attracts CO₂ when it ’ s dry and releases it when wet . We realised we could expose that material to wind and it would load up with CO₂ . Then we could make it wet and it would release the CO₂ in a way
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