GREEN
02/02/2009 05:12 am ET | Updated May 25, 2011

New Cement Absorbs More CO2 Than Production Emits

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 heated. 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 absorbs 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.

Read more on guardian.co.uk