Coal for Carbon Capture

Helen - Now, we've heard about the biological techniques of capturing carbon. Now it's time to move onto the geological methods: starting with the use of disused coalmines. Something that we have plenty of here in the UK. We sent Meera down to London to find out more.

Meera - While we're all worried about the increase in carbon dioxide in our atmosphere another worry is our source of energy for the future. The burning of fossil fuels which aren't renewable sources of energy means that as well as increasing the carbon dioxide in our atmosphere our energy sources are running out. In order try and kill two birds with one stone, Professor Peter Styles from the University of Keele has been looking into using un-mine-able coal seams to not only sequester CO₂but also enhance the release of methane from these seams. As coal absorbs CO₂twice as readily as methane, when CO₂is piped in the coal absorbs it readily and the methane is released. Therefore providing us with energy as well as preventing CO₂from entering our atmosphere. I spoke to Peter recently at a carbon capture event put on by the Institute of Physics at the Royal Society in London. I asked him about what his team had been looking into to capture carbon from our atmosphere and how they plan on going about it.

Peter - We're particularly interested in coal as a repository. In a slightly different context in that we were looking at catastrophic failures in mines which emitted methane. That got me interested how much gas could be stored in coal. With CO₂it's the case that coal actually likes CO₂. If you actually place CO₂close to coal it will start to absorb it and give you more methane. You can get a virtuous cycle of producing an energy source and then storing the by-products. That combination will deal with an energy issue and also deal with the CO₂sequestration issue which really attracts me. 30% of the UK is underlined by coal of one kind or another and even with our very long history of mining we've only removed a fraction of the coal. There is a tremendous amount of coal there which is accessible. If you go to China their main source is coal. If we can produce technology which will enable them to work more environmentally friendly then that would be a great contribution.

Meera - How would you actually get the CO₂down there in the first place in order to be absorbed by the coal?

Peter - You would usually do this in conjunction with processed coal bed methane. Coal bed methane you actually drill a hole - in the old days it would be a vertical bore-hole. Now it would be a vertical bore-hole with horizontal wells off it. It can cover from one single vertical hole a very large area underground. You will then pump water off initially and eventually reduce the pressure and the methane will come off. You can either have a separate bore hole in which you pump CO₂or you can do that for a while and then reverse it instead of extracting methane you start to pump CO₂back in. That will release more methane so I imagine some kind of cycling process where you actually alternate extraction of methane and injection of CO₂.

Meera - If we were to do that and take it out of our atmosphere how long would that be able to help up for?

彼得-关于煤炭的一件事是,你将商店it permanently. If you've permanently locked it out because coal actually absorbs the CO₂into its structure. Most of the other sequestration methods are not intrinsically permanent. You're actually just putting the CO₂into the porosity of the rock. It is possible for it to escape. In most oil and gas which is ever produced we don't see it. It escapes into the environment. Coal is still there. It doesn't move very far. There's that permanence which is part of it as well as the volume.

Meera - Has this actually been tested anywhere yet?

Peter - Yes, there have been several experiments. The biggest one, potentially, was a collaboration between Canada and Western China where they increased the output of gas by 5-6 times than by what they did without the injection of CO₂.

Meera - Of all the different processes available, what looks like the most promising one to reduce carbon dioxide in the atmosphere by the greatest percentage?

Peter - I'm trying to look at this as a combined cycle. I'm not just looking at sequestration. I'm trying to look at energy too. If you just look at sequestration then probably I would guess that enhanced oil recovery - pumping it in to old abandoned oil fields or depleted oil fields would be a very, very useful process. That would have been my guess because the technology for that is very mature. Fuel for the future will be coal and so we actually need to deal with that. Not just in the UK but globally because if we just continue burning coal and do nothing with the CO₂then we're going to all be in trouble.

Meera - So there you have it. Whilst we can't purely rely on hiding CO₂from our atmosphere these capture methods are buying us some time to come up with a new, clean source of energy for the future whilst trying to reduce our impact on the environment in the mean time.