Friday, April 21, 2006

Can we strip carbon directly from the atmosphere?

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?


Chris Davis said...

I'm not really that excited about storing CO2 underground. I think it's a bit of a failure of imagination that doesn't view CO2 as a resource; we're still throwing things "away" and not trying to close any cycles. To back up my point, the two links below show interesting work that is being done to sequester CO2 in the soil as a means to also increase fertility (carbon is stored as a stable form of charcoal that is combined with nutrients). I think we need more solutions such as this which are capable of generating additional revenue streams. Dumping CO2 into underground caverns is a financial burden.

I look forward to hearing other's ideas and opinions about this topic...

pedaller said...

I must agree with Chris above as regards to thinking of captured carbon dioxide as a resource rather than as a waste product.

And I agree with David in his post that the cost is prohibitive when about $15 worth of coal produces about a tonne of carbon dioxide. (although this may only be a reflection that the cost of coal is too low).

However, about $420 worth of petrol produces about a tonne of carbon dioxide, so the cost of removing the carbon dioxide from the atmosphere would only double the cost of the petrol consumed which seems to me a quite reasonable cost to be borne by the consumer. Why couldn't these scrubbers be used in major cities?

David Jeffery said...

Absolutely agree Chris. That technology looks interesting too.