The cement sector is responsible for some 5-10% of global CO2 emissions, and growing demand - principally from developing countries - is likely to see its emissions quadruple by 2050.
Traditional Portland cement clinker is made by mixing limestone with clay and heating it in a kiln at 1,450°C. The process produces large amounts of CO2 - 60% coming from the calcination process and 40% from the fuel used to heat the kiln.
A report on the sustainability challenges facing the sector, issued by the World Business Council for Sustainable Development two years ago, called on producers to reduce CO2 emissions through a range of measures, including the use of alternative materials, such as fly ash from coal-fired power stations or blast furnace slag, to reduce the clinker content of cement (ENDS Report 328, pp 19-22 ).
Because the binding potential of Portland cement clinker is only 50% efficient, only some 15-20% of alternative materials can be added for most applications.
However, Swedish firm EMC has patented a technology which allows a greater proportion of materials such as fly ash or sand to be used, thus reducing CO2 emissions significantly. The technology reduces the need for conventional Portland cement clinker by using an intensive grinding process to improve binding performance.
The company claims that its technology could reduce the amount of Portland clinker used to make cement by 50%, reducing emissions of CO2 by some 40%. If applied to the cement industry worldwide, this would produce a 3% cut in global CO2 emissions.
EMC claims that building projects in Sweden - where it has a pilot plant - have shown that its cement matches the performance of conventional cement and exceeds it in terms of durability. Several international cement companies including Lafarge and Heidelberg have tested the product.
Although EMC's technology was first developed seven years ago, the company claims that commercialisation has been blocked by the composition criteria included in the European standard for cement, EN 197-1:2000.
"The European standard effectively guarantees the dominance of Portland cement and keeps the competition out," claimed EMC chief executive Atle Lygren.
The standard appears to go against the spirit of the EU Directive on construction products, which says that product standards should be based on performance criteria "as far as practicable".
A second option being pursued by EMC is to seek "European technical approval" for its product - a process outlined in the Directive for products for which there is no European standard. However, Mr Lygren said little progress had been made since it applied 18 months ago.
Mr Lygren accused Cembureau, the European cement industry association, of using its influence to ensure the standard specified high levels of conventional clinker in order to maintain the major manufacturers' dominance. He also claimed that the major players ensured that EU guidance on the "best available techniques" to control pollution from cement kilns ignored alternative technologies.
Dr Willem Van Loo, Cembureau's technical director, "completely denied" Mr Lygren's claims. Alternative types of cement could seek approval through the technical approval process, he said. Lafarge declined to discuss the merits of EMC's product.
In contrast, EMC says it has been able to commercialise its technology in the USA because product standards there are solely performance-based. In April, Texas EMC Products, a joint venture between US cement producer Few Ready Mix Concrete and EMC, will bring a commercial-scale fly ash processing plant on stream.
The cement industry wants a generous cap on its CO2 emissions to reflect its view that little can be done to reduce process emissions from the calcination process. However, if technologies such as EMC's were commercialised, the sector could significantly reduce its emissions - giving manufacturers a surplus of allowances to sell on the market.