I’m a fan of Wired magazine – its a pretty amusing read, and every once in a while I see something that really makes me think or go do a bit more reading.  However, I was a little chapped when reading the feature article in their most recent issue – a review of technologies we thought we would have by now, but don’t.  On that list was clean coal (link here, scroll down to find the clean coal piece).  While I appreciated the fact that Wired was willing to run a story that called clean coal an oxymoron, they got the barriers to its implementation wrong:

The good news is that we already have the technology to use [coal] without melting the polar ice caps. It’s called carbon capture and storage — sucking up the CO₂ that results from burning fossil fuels, compressing it into liquid form, and pumping it into the ground.

Here’s my problem – we haven’t actually worked out how to keep it in the ground, which is an immense technical challenge.  Liquefying CO2 isn’t all that hard – pressure or very low temperatures will get you CO2 in liquid form.  But once we inject it deep underground, it gets a lot warmer and the pressure levels are likely to drop . . . meaning it returns to a gaseous state.  It’s hard to trap gases underground (geology is tricky – lots of faults and cracks to worry about, not to mention earthquakes!) and even when we do, the CO2 might interact with water, creating carbonic acid which can dissolve (very slowly and inexorably) the stone that makes up the storage reservoir, potentially creating holes through which the CO2 might return to the atmosphere.  We don’t have great fixes for these issues right now, though there are some technologies that might be promising down the road.  So, to summarize, right now we can extract (scrub) a lot of the CO2 from the process of burning coal, liquefy that CO2 and pump it underground.  But if we can’t keep it there, we have just created a very long, expensive and indirect route for those emissions to reach the atmosphere.
This is not to say that carbon capture will never happen.  A lot of money is being poured into this idea (see a recent posting at the NYTimes).  And this is certainly not to say that I don’t want to see it happen – finding a way to produce cheap electricity with minimal environmental impact is a dream that will work in everyone’s favor, both now and into the future.  But the clean coal crowd needs to be honest, as do the wind and solar people – there are still barriers to the successful implementation of all of these technologies.