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Explained: How does carbon capture reduce greenhouse gases?

Capturing and storing carbon dioxide released into the Earth’s biosphere is a complex and expensive process, but one that’s increasingly seen as essential to meeting global targets for reducing greenhouse gas emissions.

In humanity’s urgent quest to arrest global heating, achieving zero emissions of carbon dioxide may no longer, on its own, be enough. According to the Intergovernmental Panel on Climate Change (IPCC), the temperature targets set in the Paris climate accord of 2015 are unlikely to be reached without the widespread application of carbon capture and storage (CCS) as well.

While carbon removal (and offsetting) is already a familiar idea through afforestation, with newly planted trees storing carbon, there has also been research into filtering carbon directly out of the air through chemical processes. So far, these processes have proved prohibitively expensive, though recently, in the U.S., United Airlines announced a multimillion-dollar investment in 1PointFive, a company that is licensing direct air capture technology from the startup Carbon Engineering. A single air capture facility could potentially suck in as much carbon as 40 million trees. The carbon would then be stored underground by oil giant Occidental Petroleum, the major partner behind 1PointFive.

A more widespread and fully developed method than direct air capture is to retrieve carbon from power stations as soon as it is burned, followed either by storage underground or by using the carbon to enhance oil and gas recovery. It is far easier (and about 10 times cheaper) to filter out carbon at a power source than it is to capture it directly from the air.

Nevertheless, some environmentalists oppose carbon capture precisely because, they believe, it assists the heavy-emission industries it is designed to make less dangerous.

Carbon capture that pays

One country strongly advocating carbon capture is Norway, which established the CLIMIT national program to develop expertise and technology to reduce the cost of CCS. One of its support schemes, CLIMIT Demo, run by state enterprise Gassnova, has co-financed about 370 CCS projects.

The technology for carbon removal exists and could reduce greenhouse gases significantly, but it will not be adopted if it remains too expensive. If captured carbon can be put to commercial use, however, it could become more financially viable. Possible applications for captured carbon that have the potential both to reduce emissions and generate revenue include fuel production, concrete enrichment and power generation. 

Of these, the first is certainly technically achievable (though, as yet, less so economically) as carbon can be converted into most types of fuel otherwise derived from petroleum. 

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Percentage of global carbon dioxide emissions attributable to the manufacture of cement

Meanwhile, using captured carbon in the manufacture of cement (the binding element in concrete), which accounts for roughly 8% of global carbon emissions, would sequester it in our buildings, bridges and sidewalks.

As to power generation, its emissions could be reduced by using carbon to run turbines more efficiently. 

CCS technologies are not yet being developed at the required speed and are still too expensive, but emissions reductions and carbon capture need not be treated as contradictory objectives. The way forward will almost certainly be to utilize both. — GP Newington


Published: June 2021


Image: Adobe Stock