Carbon emissions from cement production could be almost 50 per cent less than previously thought, according to new research published in Nature Geoscience.
According to the research 43 per cent of the carbon emissions released from the production of cement between 1930 and 2013 has been offset by the process of “carbonation”, where cement products absorb carbon dioxide from the atmosphere.
The researchers say it is an important discovery as cement production accounts for approximately five per cent of all emissions from fossil fuel combustion and industrial processes, mainly through the process of calcination, which releases carbon dioxide into the atmosphere during cement production.
Harvard University physicist Dr Zhu Liu and colleagues used new and existing data on cement characteristics to mathematically model the amount of CO2 sequestered globally by four different cement materials during service life, demolition and secondary use.
They estimated that 4.5 gigatons of carbon were sequestered between 1930 and 2013, equivalent to 43 per cent of the CO2 emitted from calcination during that period. This makes cement a “substantial carbon sink”, according to the researchers. Fossil fuels used in the production of cement were not included, however.
The paper said that while civil engineers were well aware of carbonation reactions, due to the effects on strength and safety, the carbon sequestering properties had not been taken into account.
The researchers suggest that “future emissions inventories and carbon budgets may be improved by including this cement sink”.
While cement doesn’t have the carbon sequestering benefits of wood (and the carbon in wood also doesn’t affect structural properties), it’s still reassuring news that our buildings may not be as environmentally unfriendly as previously thought.