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Substantial global carbon uptake by cement carbonation

Fengming Xi, Steven J. Davis, Philippe Ciais, Douglas Crawford-Brown, Dabo Guan, Claus Pade, Tiemao Shi, Mark Syddall, Jie Lv, Lanzhu Ji, Longfei Bing, Jiaoyue Wang, WeiWei, Keun-Hyeok Yang, Björn Lagerblad, Isabel Galan, Carmen Andrade, Ying Zhang and Zhu Liu

Nature Geoscience. Published online 21 December 2016.

Paper Abstract

Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions fromall industrial process and fossil-fuel combustion in 2013. Considerable attention has been paid to quantifying these industrial process emissions from cement production, but the natural reversal of the process—carbonation—has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr-1 in 1998 to 0.25 GtC yr-1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories