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Could we count on air capture?

smokestack.jpgAmong the many proposed techno-fixes for climate change, ‘air capture’ seems like one of simplest solutions – what could be more straightforward than sucking greenhouse gases out of air and storing them somewhere else?

But various proposals for the direct removal of carbon dioxide from the atmosphere have largely been sidelined from serious discussions on climate control. Noteworthy scientists and engineers – including those of the Intergovernmental Panel on Climate Change – have regarded the technology as a non-starter owing to the large amounts of energy involved. After all, energy costs money and unless we find ourselves in ‘climate crisis’ mode, solutions to climate change will be considered on economic grounds as well as on efficacy.

But a new study by Roger Pielke, Jr. (of the University of Colorado and Prometheus blog) shows that air capture could be a cost-competitive mitigation option. His analysis, soon to be published in Environmental Science and Policy [uncorrected proofs available from Pielke], compares the average costs of air capture over the 21st century to other mitigation options (namely international greenhouse gas regulation under the UN framework convention) assuming that technologies available today are used to fully offset net human emissions of carbon dioxide. He runs the analysis for 3 different (and citable) estimates of the cost of air capture – $500, $360 and $100 per ton of carbon. The IPCC estimate falls near the middle of this range.

For the two upper values, the cost of air capture would be comparable to the estimated cost of stabilizing atmospheric carbon dioxide at 450 ppm or 550 ppm given by Nick Stern in 2007 and by the IPCC in its last report. But if the costs of air capture decrease to $100 per ton of carbon, then it would prove much more cost-effective than stabilizing at 450 ppm or 550 ppm. We must therefore give air capture the same attention as other approaches to mitigation, argues Pielke, Jr.

How this would compare price-wise to carbon traded on a future international market is hard to say, it seems, given that CO2 permits are currently being traded for €11.80 ($15.12, £10.42) in Europe.

But as he points out in an accompanying FAQ on the paper over on Prometheus, cost isn’t the only obstacle to deploying air capture. For a start, the technology itself is still embryonic. Though there are several prototypes under development, small companies trying to commercialize their products are now feeling the pinch of the lack of venture capital.

And if air capture is fully developed and scaled up, there remains the issue of where to store the captured gas. Here, there are some innovative options, from enriching the air in greenhouses to flushing out aging oil fields. But even if both capture and storage technologies turn up trumps, will society see this as an acceptable solution? Over on Prometheus, Pielke, Jr. says:

If air capture is a possible contribution to mitigation some believe that it will lessen the ability to use climate policies to get at other agendas. So for some there is a reflexive almost irrational opposition to air capture simply because it is a technological fix.

Robert Kunzig and Wally Broecker wrote in New Scientist recently that overcoming these obstacles could be worth the effort, because air capture has such great potential advantages:

For one thing, air scrubbers would capture CO2 from any source, big or small, including cars, planes and heating systems. These produce more than a third of global CO2 emissions but it is impractical to capture the gas at source from tailpipes or flues. What’s more, because CO2 emissions mix into the atmosphere quickly and levels are the same pretty much everywhere, air scrubbers could be placed directly over sequestration sites. In contrast, CO2 captured at power plants will often have to be sent through hundreds of kilometres of pipeline. As David Keith of the University of Calgary puts it, air capture is “decoupled from the rest of the energy economy”.

Is it feasible and worth the effort? Let us know what you think.

Olive Heffernan

Image: iStockphoto


  1. Report this comment

    Alan said:

    Burning coal does much more than emit CO2, the aerosols have a lage cooling effect and are the primary cause of acid rain, it’s obvious it needs to be phased out.

    Since I know Roger frequents this blog I would like to know if he thinks this idea is better than phasing out coal or if he sees it as an adjunct to phasing out coal.

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    Doug Heiken said:

    “Air capture” — that’s what trees do. How can an engineered solution remove trace gasses any more efficiently than solar powered trees that cover a large fraction of the land surface? I am a skeptic. Pielke has questionable credentials. Isn’t he one of those semi-skeptical apologists?

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