The technology is seductive. Coal is the most abundant fossil energy source on earth, reserves are reasonably well distributed throughout the world, and carbon has already been successfully buried at three locations worldwide.
The most well known is the Sleipner gas rig in the North Sea, operated by oil giant Statoil. The natural gas which the rig was built to extract was found to have a CO2 level which is too high to pump into people’s homes. Statoil used to strip out this excess CO2 and pump it straight into the atmosphere, but then found that it could save hundreds of thousands of euros in carbon taxes by capturing the CO2 and pumping it down into a saltwater aquifer deep under the North Sea.
Another project in the US takes CO2 produced by a coal gasification plant in North Dakota (built to produce synthetic natural gas from coal) and pipes it up to Weyburn in Canada, where it is used to force extra oil out of an ailing well. A third site, Salah in Algeria, uses the same principles as the Sleipner project for natural gas refining.
These three projects have one thing in common: none of them are generating electricity. The technology which is needed to either strip CO2 from the toxic, complex fumes of a coal power plant, or to extract the CO2 before the coal is burnt, is still untested on a commercial scale. Moreover, finding geologically suitable strata in which to inject the liquefied, highly pressurised CO2 is difficult. Although the UK has a number of spent oil and gas fields in the North Sea which could serve for purpose, a recent study which examined China’s potential storage sites concluded that further work is needed to see whether carbon capture and storage is viable. A lack of suitable sites means longer pipelines to transport the carbon to where it can be buried (and hence, more energy), or the transporting of liquefied CO2 by ship to a suitable repository.
Jon Gibbins, Senior Lecturer in Engineering at Imperial College London and an expert on CCS, estimates that a ‘clean coal’ plant would require between 25 and 30 per cent more fuel than a conventional one in order to capture and store 90 per cent of its CO2.
This means that if Drax power station in Yorkshire were to be made capable of carbon capture and storage, it would require an extra 9.5 million tonnes of coal every year simply to provide the energy for the process of cleaning up emissions.
Although the UK has little need of coal, being so rich in renewable resources, the responsibility to pioneer carbon capture technology may fall to us as a huge historical emitter of carbon dioxide.
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This article first appeared in the Ecologist November 2007