Sunday, December 13, 2009

No Such Thing As Free Sequestration?

The major thing now that a lot of big corporations are talking about to make themselves sound like they've got environmental credibility is carbon capture and storage. On paper, what it means is that where power plants, factories, and other large carbon dioxide producers would previously emit the gas into the atmosphere, with CCS they would capture much of the carbon dioxide before it can be emitted and then sequester it, either deep underground or in the soil cycle, where it wouldn't contribute to climate change.

So the theory goes, anyway. Big businesses are beating this drum for all it's worth, even though there hasn't been so much as a pilot project to tell us whether or not it actually works - and not only if it works, but if it can work economically. It's one of the environmental hot potatoes right now, and personally, I hope that it works: I think we'll need all the avenues of mitigation we can find in the years ahead, and that's not even taking geoengineering into account.

What worries me, though, is the potential nature of these subterranean carbon dioxide reservoirs, and what happens if they're breached - either inadvertently by human activities, or as part of natural processes. The first is simple enough to avoid. I would imagine that carbon dioxide reservoirs would be sufficiently deep underground that some guy with a shovel wouldn't need to worry about breaching one, but nevertheless, I can see governments creating no-dig zones in and around these reservoirs to eliminate, or at least seriously reduce, the chance of a breach.

What I find more concerning is the prospect of these reservoirs in earthquake zones. The planned CCS schemes I've seen are rather local to the point source of the emissions, and so unless actual CCS programs end up taking a rather different shape, planners and engineers will have to reckon with the local geography and geology.

This could be an issue in earthquake zones. In California it's not too much of an issue, as there are only a handful of small coal-fired power plants within the state itself, but elsewhere it's a different story. The necessity - if it does turn out to be a necessity, depending on how CCS takes shape - of insulating these reservours against seismic shocks might well make CCS far less of a deal than it seems at the moment. The Los Angeles subway system cost considerably more to build per kilometer than comparable subway systems due to the need to reinforce the tunnels against earthquake damage, and governments or concerned citizens' organizations might demand that carbon reservoirs be similarly reinforced. Los Angeles spent billions building the 28-kilometer Red Line and Purple Line subways, but I don't imagine it would take very long for a coal plant running at full tilt to fill them up with gas.

It's probably for the best that there aren't yet any active CCS demonstrations. I think there are a lot of biting questions that remain to be asked.

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