The Prometheus science policy blog has an interesting discussion on the economics of carbon dioxide "air capture". From a bit of reading around the topic (eg, this PDF), the idea seems to be that you build big carbon dioxide scrubbing towers near a site appropriate for geosequestration. You pump air through the towers and chemicals remove the carbon dioxide from it. The CO2 is then pumped away and stored underground. This is an extension of the geosequestration (carbon capture and storage) concept, but instead of capturing carbon dioxide as it's released from power stations, you capture it directly from the air. The advantage is that you don't have to compress the carbon dioxide and transport it from a power station to an appropriate geosequestration site.
Apparently the likely costs of this technology are in the range of US$200-$500 per tonne of CO2. This is a lot: the cost of replacing a coal power station with a wind or solar one are in the range of $50 - $100 per tonne of CO2 avoided (and coming down) and even this cost seems to be far too high to be politically palatable. (Let's also remember that renewables have other benefits such as reducing air pollution and reducing reliance on exhaustible forms of energy).
Have you heard of this technology? Do you have any thoughts? Is this sci fi kind of stuff?
My thoughts are that this kind of technology - mainly because of its price - has a very limited role to play. One possible role is that if it becomes clear that the damage of global warming is likely to exceed $500 / tonne and other methods haven't been effective or fast enough, then maybe - maybe - we can erect these towers to avoid a climate catastrophe. In that sense, this technology could represent a sort of last resort.
In the meantime, there's a whole lot of relatively low-cost solutions we can be implementing now.
What do you think?