Carbon Capture and Utilisation - Planet Earth Online

Emma -   One of the most promising technologies for tackling rising carbon dioxide levels in the atmosphere is known as carbon capture and storage.  The idea is to trap carbon dioxide from power stations inside rocks rather than release it into the atmosphere.  But what if, instead of just storing the carbon, you could turn it into something useful - like bricks?  Planet Earth podcast presenter Richard Hollingham reports from the University of Nottingham for us this week on a new technique dubbed:  Carbon Capture and Utilisation.

Richard -   They look like large boiled sweets or perhaps something you'd use to make gravy, but when you bang them together, they're as hard as bricks.  Anthony Benham is Business Development Manager at the National Centre for Carbon Capture and Storage.

Anthony -   One of the experiments that we're trying to do here is to react carbon dioxide with naturally occurring minerals.  In this reaction process you actually produce a new type of mineral that can effectively be used in the construction industry, for example, producing aggregates, and things like that.

Richard -   This process of combining carbon dioxide with rock turns out to be nothing new.

Anthony -   What we're trying to do is accelerate the natural process of weathering that occurs in the environment. So certain types of rocks react with the carbon dioxide that naturally occurs in the air and produce new minerals.  This occurring in the normal every day environment is a very, very slow process. So what we're trying to do is accelerate that process; and in doing so, you produce these effectively OXO cubes of different sort of minerals if you like. So this one's quite a brown colour and we've got this one here which is almost pure white, it looks a bit like chalk.

Richard -   If you bump them together, the white one's quite soft, this brownish tan-coloured one, both of which fit in the palm of your hand, that one's quite hard so you can make different things out of them.

Anthony -   Yeah, that's right and the products that you get will essentially depend on the materials that you use at the start of the reaction.  For example, we use a lot of silicate minerals here - magnesium silicates and calcium silicate minerals - and depending on the quantities that you use will partly determine the end products and therefore the colour that you get at the end of the reaction.

Marco -   So we close the cylinder over there.

Richard -   The reaction itself takes place in a sealed metal flask with a mixing paddle.  It looks a bit like an industrial kitchen mixer.

Marco -   We tighten the screws....

Richard -   In the lab, researcher, Marco Drea talked me through the process which even sounds like it could be a recipe.

Marco -   We just mix our feed stock with the CO₂, so we mix them together and we produce our final product which is the mineral carbonate.

Richard -   But at the moment that final product isn't very big, even though each domino-sized tablet contains three litres of carbon dioxide, you'd still need a lot of these tablets to make even a single house brick, let alone a house.  Mercedes Maroto-Valer is the Chief Scientific Officer for the National Centre.

Mercedes -   Yes, you are absolutely right.  We need quite a few of these to actually build a house.  These are just demo pieces that we build because they're easy for us to take around and it is easy for people to think about these as something that the CO₂ has been solidified into and now they can walk out the room with this on their hands or in their pockets.  But you are right, we need to scale up the process and we are currently involved in a series of projects looking at scaling up, so actually we can see the potential and feasibility of the technology in the UK.

Richard -   How would this work in practice?  Would you have a brick plant next to a power station?  How would this work in practice, if it did work?

Mercedes -   That's one of the things that we are now involved in in a project together with the Energy Technology Institute, Caterpillar, and also Shell; and what we're looking at is the feasibility of this technology in the UK. So we will be able to see in which locations it makes sense to build plants that will actually take the CO₂ and mineralise it.

Richard -   One of the other considerations is that the process itself uses energy which rather defeats the object if making the bricks involves generating more carbon dioxide.  Anthony Benham...

Anthony -   We're looking at ways of accelerating the reaction using typical atmospheric pressures and temperatures and varying the conditions, and the concentration of carbon dioxide that you use, and the quantity of material that you use in the reaction because ultimately, if we are to produce this at a large scale then you want this to be using the lowest amount of energy that you can.

Richard -   So if they succeed in scaling up this technology, future power stations could be built with bricks using emissions from power stations...