Air capture 101

Potentially a long-term option for putting waste heat to use

Posted by Joseph Romm (Guest Contributor) at 11:09 AM on 01 Apr 2008

RealClimate has a good introductory post on air capture, which they explain as:

The idea would be to let people emit the carbon dioxide at the source but then capture it directly from the atmosphere at a separate facility.

This is going to be a relatively expensive and complicated strategy for decades -- and, of course, you need a place to put the carbon dioxide. That said, a lot of work is going on to see if one can do air capture driven by heat.

Why does that matter? The world has a lot of zero carbon waste heat not currently being used for anything. Indeed, U.S. thermal power plants alone throw away as much energy in waste heat as Japan uses for every purpose! That's more than 20 quads. And that doesn't even count the heat thrown away in industrial processes. Now, the smartest thing to do with that heat, for the next few decades, is obviously either generate electricity with it or use it for heating buildings or industrial processes.

But we should surely do a fair amount of research on air capture, since, by no later than the 2020s, we're going to get desperate for emissions reductions, and by the 2030s, we're going to be very desperate and willing to pursue expensive options we that aren't yet politically realistic.

Indeed, it seems rather likely to me that something like air capture will be needed by the second half of this century. Assuming we actually seriously try to keep emissions below 450 ppm (currently, a doubtful proposition), we'll probably need to go back to below 400 by 2100 and 350 by 2150, in my optimistic spin on Hansen's latest paper.

In summary, air capture is not a near-term or medium-term solution, but it is possibly a long-term strategy.

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.

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2 Comments | Post a Comment

This seems like a bad idea

Yes, it could work out positively if you have enough free heat. But in that case why not generate energy with that "zero carbon" (ha!) heat? Think of the entropy involved with CO2 well mixed with O2 and N2 (and others), and how much energy would be involved in seperating it out. This would only be a reasonable solution in a world where we have too much energy (not our world). A better idea would be to use nature - for instance, grow plants that extract CO2 from the air. Then bury these plants (or extract out the carbon first). Yes, this still takes a lot of energy - but all of the energy required to seperate out the carbon from other gases is provided by the sun.

by Matt G at 5:59 PM on 01 Apr 2008

I second that, Matt

There are a number of more efficient ways to capture CO2 and use waste heat, as noted by the author. Heating buildings or greenhouses or even just plain old water makes more sense than trying to drive a carbon capture process. Why not focus our efforts on capturing the concentrated sources of CO2? Better yet, lets focus our efforts on eliminating those concentrated point sources, and letting nature do the scrubbing.

I suppose that's where the author was heading, envisioning a world with high atmospheric CO2 and no more emitting sources. If that scenario ever plays out, however, I'd bet the game will be won. If there's still a problem, we can then direct our resources toward such a proposal. In the meantime, we are missing the even the low-hanging fruit. Funding of this sort becomes a zero sum game, with all the money for CCS (and now atmospheric collection?!) diverted from research for carbon "neutral" energy production.

by thadadkins at 6:26 AM on 02 Apr 2008

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