Posted by: JohnnyRook | January 1, 2009

New Form of Cement May Be a Carbon Sink

According to the Guardian, the London company Novacem has developed a new type of cement that is carbon negative (absorbs more carbon than it emits). If true, this would be a major breakthrough as cement currently accounts for 5% of the world’s CO2 emissions.

CO2 is released during cement production in two ways. First, generating the high heat needed to make the cement releases CO2. Second, the burning of the limestone releases even more. The new cement can be produced at lower temperatures, reducing energy consumption and CO2 emissions, plus as it hardens it absorbs more CO2 than conventional cement.

The Guardian explains:

Standard cement, also known as Portland cement, is made by heating limestone or clay to around 1,500C. The processing of the ingredients releases 0.8 tonnes of CO2 per tonne of cement. When it is eventually mixed with water for use in a building, each tonne of cement can absorb up to 0.4 tonnes of CO2, but that still leaves an overall carbon footprint per tonne of 0.4 tonnes.

Novacem’s cement, which has a patent pending on it, uses magnesium silicates which emit no CO2 when hearted. Its production process also runs at much lower temperatures – around 650C. This leads to total CO2 emissions of up to 0.5 tonnes of CO2 per tonne of cement produced. But the Novacem cement formula absorb far more CO2 as it hardens – about 1.1 tonnes. So the overall carbon footprint is negative – ie the cement removes 0.6 tonnes of CO2 per tonne used.

If the energy to make the cement comes from sustainable sources the amount of CO2 removed from the atmosphere could be even greater.

The project is being supported by the British government whose Technology Strategy Board has invested £272,000 in it.

Supposing that the claims made for Novacem’s cement hold up, it could play an important role in cutting greenhouse gas emissions given that demand for cement (like that of nearly every other industrial material as governments do not seem to be able to imagine an end to economic growth) is forecast to increase. In any case, it will take several years to get the new cement to market as first it must be tested for strength and licensed.

The new cement, which uses a different raw material, certainly has a vast potential market. Making the 2bn tonnes of cement used globally every year pumps out 5% of the world’s CO2 emissions – more than the entire aviation industry. And the long-term trends are upwards: a recent report by the French bank Credit Agricole estimated that, by 2020, demand for cement will increase by 50% compared to today.


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