Planet Earth - Carbon Capture and Storage

20 March 2011

Interview with

Mike Stephenson, National Centre for Carbon Capture and Storage

Ben -   One of the most promising technologies for tackling rising carbon dioxide levels in the atmosphere is known as 'Carbon Capture and Storage'.  The idea here is that you pump carbon dioxide from power stations into a rock, rather than into the atmosphere.  But you do need to have the right kind of rock.  To find out more, Planet Earth Podcast presenter, Richard Hollingham, visited the pub...

Richard -   It's the curiously named, Ye Olde Trip to Jerusalem.  In the centre of Nottingham, it lays claim to being the oldest inn in England.  The pub is built into a sandstone cliff and inside, it feels more like being in a cave than in a pub.  A cave with beer.  I'm here to meet Mike Stephenson, the Director of the National Centre for Carbon Capture and Storage.  Mike, why have we come to the pub?

Ye Old Trip to Jerusalem pub, Nottingham, EnglandMike -   It's a great place to show you how we can use these rocks to actually absorb carbon dioxide.  We can take carbon dioxide out of the atmosphere and push it or force it into these rocks.  And we think it will probably stay there for a very, very long time.

Richard -   Now I had this idea in my mind of carbon capture and storage.  It was using reservoirs underground, vacant spaces in the rock like tanks that you could inject the carbon dioxide into, but that's not the case?

Mike -   No, it's not like that at all.  There are very few open spaces if you go down deep into the rock.  The pressure is too big to get open space, but what these rocks illustrate quite well is that there are a lot of very small spaces between the particles that make up the rock.  So for example if I just show you very quickly, just a demonstration.  If you pour a little bit of beer there, be careful not to pour too much on, but if you pour a little bit of beer on the sandstone which is the wall of the pub, what you see is it's all wet and shiny at first, and what you slowly begin to see is the beer is soaking into the rock there.

Richard -   It's disappearing very, very quickly, isn't it?  And now, it's almost dry, isn't it?

Mike -   It's almost dry, yeah.

Richard -   I suppose it's like a beach, isn't it?  When you step on it, you get the water there then it goes dry very quickly.

Mike -   That's right.  What you've really got here is that the sandstone itself is made of particles, more or less spherical particles.  They're all packed together.  They're not packed together perfectly because there are spaces in between and when I'm pouring the beer in, then what's really happening is the water, the beer, is leaking into the wall or soaking into these spaces in between the particles.  You can't see them, but there is a huge amount of space inside this sandstone, and that's what we proposed to do, fill it up with carbon dioxide.

Richard -   How would you do that?  It's very easy to drip a beer or a little bit of wall, it's quite different to inject carbon dioxide.

Mike -   If you do it right, you should be able to push it into this rock quite effectively.  This has been done for a long, long time.  For example in United States, they've been injecting CO2 into rocks for 30 or 40 years.  Actually for enhanced oil recovery, that means, squeezing the last bit of oil out of an old oil reservoir.  So we know how to do this and we think we could probably store quite a lot of CO2 in this particular rock.  This is another reason why this pub is interesting.  This Bunter sandstone underlies a lot of the North Sea and the Irish Sea and these are the places where you might put the CO2.  So, you're actually looking at the rock that, underneath the North Sea, would be our storage space.

Richard -   Now you dribbled the beer on a couple of minutes ago.  It's almost disappeared, but some of it has come out.  How do you ensure that your carbon dioxide stays there?

Mike -   The main thing is to have the right kind of structure that will keep the CO2 in place.  CO2 is a buoyant fluid when it gets injected at that depth and it will tend to rise up above the water that's also in the rock.  So it'll tend to float up and the key really is to making sure that the rocks above the reservoir or above the sandstone are completely impermeable.  So a bit like a damp course in a house.  We're talking about a rock layer that stops the CO2 going up any further.

Richard -   So when is this going to happen?  Are we on the cusp of this technology being available so we start injecting carbon dioxide into these areas?

Mike -   The key thing is that although all the three types of technology - this capture which is really a chemical engineering activity, the transport which is putting it through pipes, and the storage or the injection into rocks - All those three things are known about and we've been able to do them for a long, long time separately.

Richard -   I guess to clarify this, the capture would be from say, a power station or something like that.

Mike -   Yeah, generally, we capture from power stations, but there's no reason why you couldn't capture from a cement work or from an ammonia factory.  All of them produce a lot of CO2.

Richard -   Okay, so you got all those in place, but...

Mike -   But the problem is, that the sheer scale at which we have to do this is something that's daunting and also, putting it together into a system that works where one thing feeds another, not too fast, not too slow, that's a big challenge.

Ben -   That was Mike Stephenson, the Director of the National Centre for Carbon Capture and Storage, and he was talking to Planet Earth Podcast Presenter, Richard Hollingham over a pint. 

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