The UK Guardian reports on Novacem, a company that is making cement from magnesium silicates that absorbs more CO2 as it hardens. Normally cement adds a net 0.4 tons of CO2 per ton of cement, but this new cement would remove 0.6 tons of CO2 from the air. This is competitive with the claims of Calera cement.
Novacem’s cement, based on magnesium silicates, not only requires much less heating, it also absorbs large amounts of CO2 as it hardens, making it carbon negative. Set up by Vlasopoulos and his colleagues at Imperial College London, Novacem has already attracted the attention of major construction companies such as Rio Tinto Minerals, WSP Group and Laing O’Rourke, and investors including the Carbon Trust.
The company has just started a £1.5m project funded by the government-backed Technology Strategy Board to build a pilot plant. If all goes well, Vlasopoulos expects to have Novacem products on the market within five years.
Vlasopoulos responded that magnesium silicates are abundant worldwide, with 10,000 billion tonnes available, according to some estimates. “In addition, the production process of our cement is of a chemical nature, which means it can also utilise various industrial byproducts containing magnesium in its composition.” He is confident the material will be strong enough for use in buildings but acknowledged that getting licenses to use it will take several years of testing.
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 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.
0.6 tonnes times 10 trillion tons is 6 trillion tons. The amount of CO2 generated by people is 27 billion tons worldwide and this could increase to 45 billion tons. So 6 trillion tons is about 200 years worth of CO2 storage.