Concrete worries

Cement kilns are the third largest contributors of carbon dioxide

Published: Monday 15 September 1997

the cement industry has a larger share in global emissions of carbon dioxide ( co 2 ) than that of aircraft worldwide, estimates an industry scientist. It contributes about seven per cent of the global co 2 output. This puts it in the third place in the list of contributors of the greenhouse gas behind the power generation industry and vehicle exhausts. Previous estimates had held the industry responsible for a much smaller share in co 2 emissions. The United Nations' Intergovernmental Panel on Climate Change had put the industry's global contribution of co 2 at 2.4 per cent; whereas the Carbon Dioxide Information Analysis Center at the Oak Ridge National Laboratory, Tennessee, usa , had put the figure at 2.6 per cent.

This brings to light the lack of attention of environmental organisations and governments to one of the major threats to the ozone layer. The aircraft industry has been the butt of a lot of criticism for its share in global emissions of co 2 . At the Earth Summit in New York in mid-June, the European Union proposed a global tax on aircraft fuel.
But aircraft rank behind the cement industry in the estimates of co 2 emissions compiled by Joseph Davidovits of the Geopolymer Institute at the University of Picardy, France.

"Cement is well known as the biggest manufacturing source of co 2 , but I certainly had no idea the total was as high as is being suggested," said John Lanchbery, director of environmental projects at the Verification Technology Information Centre, London. As the global production of cement is rising by about five per cent a year, the industry would be responsible for about 10 per cent of global co 2 emissions by the years 2000, he indicates. He has called for worldwide efforts to develop new forms of cement that produce less co 2 .
The cement industry produces co 2 in two ways. First, by burning large quantities of fossil fuels to heat the kilns to a temperature of about 1,450 c that is required for roasting limestone; and second, by the conversion of calcium carbonate to calcium oxide inside the kilns.

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