Cement: From Carbon Source to Carbon Sink?
Lloyd has written before about cement as "the unheralded polluter" - in fact some estimates suggest that cement manufacture may be responsible for more global greenhouse emissions than the entire aviation industry. It's no wonder then that we were excited when we heard about Eco-Cement, a greener cement that actually absorbs more CO2 than it produces. Now it appears that another company is also producing carbon negative cement. The Guardian reports that UK company Novacem has developed a cement with an overall negative carbon footprint of 0.6 tonnes per tonne of cement. This compares to an overall positive footprint of 0.4 tonnes per tonne of standard cement. So how do they do it? The Guardian explains a little more:
Making traditional cement results in greenhouse gas emissions from two sources: it requires intense heat, and so a lot of energy to heat up the ovens that cook the raw material, such as limestone. That then releases further CO2 as it burns. But, until now, noone has found a large-scale way to tackle this fundamental problem.
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.
And the good news is that Novacem's technology has attracted considerable attention from major players in the industry like Rio Tinto Minerals, WSP Group and Laing O'Rourke, and investors including the Carbon Trust. If Eco-Cement, Novacem's product, or other cement could be turned into an overall carbon sink, rather than a significant carbon source, as it currently is, the implications for climate change could be profound indeed.