CCS alternative

CCS should not be seen as a panacea with no serious adverse effects

The research work at Imperial College London into carbon capture and storage may be ground breaking, but CCS should not be seen as a panacea with no serious adverse effects (News, PE May).

The energy sector, where CCS may prove workable, produces 40% of CO₂ emissions, with the other 60% arising largely from domestic, business and transport sources. A few calculations in one of these sectors will illustrate the scale of the problem.

Domestic sources account for 15-20% of carbon emissions, about 80 million tonnes per year. Gas consumption in this sector is 400TWh per year. To meet the 80% objective would therefore require 320TWh to be supplied as electricity. Currently coal and gas power stations release 200 million tonnes CO₂ per year generating 285TWh of electricity.

To produce 320TWh as extra electricity would increase emissions by at least 234 million tonnes a year, allowing for the CO₂ capture efficiency of 90% to replace 80 currently. The CCS equipment and investment would therefore produce a net CO₂ reduction of only 64 million tonnes in the domestic output, but add 234 million tonnes of CO₂ for CCS treatment.

The additional electricity has also to be generated. The instantaneous peak in domestic gas consumption on the day of highest usage is about 100GW, producing 85,000MW useful heat. Since electricity, unlike gas, cannot be stored, the 85,000MW of heat would have to be met by equivalent electricity produced instantaneously by power stations. That would have to be in addition to the existing electricity generation plant output peak of 60,000MW. This policy would therefore require a doubling of the grid-connected thermal power stations – and that is only one of the three sectors.

CCS is not a prudent alternative to a new fleet of pressurised water reactors to generate low-carbon electricity.

Paul Spare, Davenham

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