Q&A: carbon capture and storage

What is carbon capture and storage?

It's a process by which carbon dioxide (CO2) is separated out - via a chemical process - and injected into either the ocean or certain kinds of rock formations. These include depleted and disused oil and gas fields, deep saline aquifers and deep unminable coal seams.

Injecting the captured CO2 into rocks employs the same technology used by the oil and gas industry to squeeze the last drops of oil from near-exhausted wells. This is done by pumping it in at high pressure.

Because such rocks have stored oil or gas for millions of years without any escaping, it is believed our CO2 emissions could be stored in the same way - provided they are stored undisturbed.

How do we know it is safe?

Apart from what geologists know about the natural storage properties of porous rock, there are a few examples of capture and storage plants today.

Norwegian company Statoil has been piping the gas down into a reservoir under the sea floor for almost a decade. But this is as yet an unproven technology over the long term.

Aren't we trying to reduce emissions, though?

According to the Office of Science and Innovation, we need to do both if we are to meet carbon targets.

Carbon storage is necessary because even if we significantly reduce our carbon footprint, the change will be rendered irrelevant on a global scale once developing countries like China and India begin to burn their vast stocks of cheap coal.

Will we be seeing more carbon capture from now on?

In 2005 the Department of Trade and Industry announced a £25m funding package to establish demonstration projects and, in a report last February, the Commons science and technology committee issued a report saying all new coal power stations should be suitable for carbon capture.

As part of the government's latest energy review, Alistair Darling announced that it would launch a grant for developing carbon capture and storage technology - first mooted in March - in November.

Darling said this would save up to 33 million tonnes of carbon by 2020, equivalent to the emissions from every road vehicle in the country.

But oil company BP described the delay in the subsidy award as "an extension too far" and, as a result, has abandoned plans to build a carbon capture and storage plant in Scotland. The plant would have burned natural gas extracted from the North Sea between Britain and Norway, and then pumped the resulting carbon dioxide back into a depleted oil field.

Can we relax a bit about carbon emissions, then?

Not really. CO2 capture and storage technology would have to be used in tandem with other emission savings - fuel switching, energy efficiency and renewable energy. And our own individual carbon footprints - due to their relatively small size - cannot be captured and stored.

It's not just large scale power plants that should be thinking about capture and storage either. According to the IEA Greenhouse Gas R&D Programme, an international collaboration which aims to evaluate technologies for reducing emissions of greenhouse gases, other industrial processes heavy on emissions could benefit from capturing and storing "without major changes to the basic process".

What are the main obstacles to its introduction?

The main priority for the development of CO2 capture technology is to reduce its cost.

It's an undoubtedly pricey business: capturing the gas in the first place is problematic as current technology reduces a power station's efficiency by anything up to 25 per cent. That means that at the moment more stations would need to be built to produce the same amount of electricity.

New efficient technology needs to be developed - also costly - to create purpose-built capture facilities that would not interfere with overall efficiency.

At the moment some oil and gas plants capture CO2 from power station flue gases. But, according to the IEA Greenhouse Gas R&D Programme, only a fraction of the CO2 is captured here; to reduce emissions from a typical power plant by 75 per cent the equipment would need to be 10 times larger.

There may also be legal obstacles: for example the Ospar Convention is an international treaty that is likely to rule that burying CO2 under certain areas of the ocean floor is illegal.

Share this article

Send this article to a friend »

• Del.icio.us
• Digg
• Reddit
• Facebook
• StumbleUpon

What are these?