The case for carbon capture

Published 15 May 2006

Whether we like it or not, the world is going to burn a lot of coal and gas. UK industry can lead the way in carbon capture and storage, but government must be prepared to act quickly, too. Simon Shackley and Jon Gibbins report

China, India and other rapidly growing economies will be based on fossil fuels, not least coal, for the foreseeable future. China is currently building one coal-fired power plant every week - adding the equivalent of the whole UK generating capacity each year. Rapid deployment of carbon capture and storage (CCS) in the UK's power sector is important, not only to cut our own emissions but also to demonstrate its viability, improve practice and encourage new plants elsewhere to be built "capture-ready" now, so that capture can be added cheaply later, and increasingly, as more international funding becomes available, from the outset.

The first CCS projects in the UK could be operational by around 2010, providing action is taken now. Industry is ready to go, but can only finance the projects if the government acts quickly to introduce ways to recover the extra costs for these fast-deployment plants - at between one and three pence per kilowatt hour (kWh), this is about the same as incentives currently provided for renewables.

Several power companies in the UK are already actively pursuing projects. BP and Scottish and Southern Electricity want to convert natural gas to hydrogen and carbon dioxide (CO2), burn the hydrogen in Peterhead power station to give low- CO2 electricity and inject the CO2 into the Miller Field in the North Sea where it will also help to recover more of the remaining oil. E.ON has announced that it is investigating CCS for a new coal-power plant in the east of England. This is expected to use a similar "pre-combustion" technology to that used in the Peterhead scheme, with coal gasified and converted to hydrogen and CO2.

Hatfield Colliery, now under Russian ownership, would also like to build a gasifier power plant with CO2 capture to use its coal on site. RWE is considering rebuilding an old coal combustion power plant at Tilbury to bring it up to state-of-the-art coal-plant efficiencies, with CO2 capture added as soon as it becomes commercially viable. This would probably use "post-combustion" capture equipment, which washes the carbon dioxide out of the flue gases before they go to the chimney, a flexible technology that can also be applied to natural-gas power plants and industrial processes, such as cement kilns. E.ON and Mitsui Babcock are also researching oxyfuel combustion: fossil fuels are burnt in oxygen instead of air to give pure CO2 with minimal further processing.

As for storage, the UK has many suitable geological reservoirs, mostly off-shore in the North and Irish Seas. Depleted oil-and-gas reservoirs could store about 40 years, or 6bn tonnes, of current UK power sector CO2 emissions (with a corresponding extension in earnings from the UK Continental Shelf). More storage is available in saline aquifers - porous rock formations that contain salt water with sealing layers above them.

Natural gas and CO2have remained trapped in geological formations for millions of years, so there are good reasons for believing that storage sites can be chosen to hold CO2 for at least the 10,000 years required for climate-change mitigation. Monitoring during and immediately after injection will be used to make sure the CO2 is being retained as expected. In the longer term, most CO2 can be "trapped" permanently, by dissolving it in the water in reservoirs and by slow reactions with the rock. Minor leakage could be tolerated - small natural CO2 leaks to the surface are quite common and are the basis of lucrative mineral-water sales, for example - but is very unlikely to occur. Unexpected leaks, most likely from old wells, would either be plugged or, in extreme cases, the CO2 would be removed and placed in another storage site.

Provided some fast-deployment CCS projects are approved in the current energy review, to give industry and the City the confidence for the next stage of large-scale investment in new CCS power plants, around ten gigawatts (GW) of CCS capacity could be operating in the UK by 2020. This would help to cut UK power-sector emissions by about 50 per cent.

But the real impact would be global, not local. CCS is the only really new low-emission technology available to help break the current deadlock and get the global agreement needed for there to be a serious prospect of tackling climate change. If the UK, which has set itself up as a global leader on climate change, doesn't follow through now on CCS, then don't expect others to show much enthusiasm.

Simon Shackley and Jon Gibbins are with the UK Carbon Capture and Storage Consortium (www.ukccsc.co.uk)

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