Global and national CO₂ uptake by cement carbonation from 1928 to 2024

<p>The hydration products of cement materials can absorb atmospheric <span class="inline-formula">CO₂</span>, and this carbonation process provides an important decarbonization pathway for the cement industry. Global carbon sequestration by cement materials has been reported, but carbon uptake in different countries remains unquantified. Here, we quantify the national cement carbon uptake from 1928 to 2023 based on 58 517 activity data from 163 cement-producing countries and regions worldwide and 6186 carbonation parameters from detailed data records of 42 countries, and we project the trend in carbon uptake by countries in 2024. The global <span class="inline-formula">CO₂</span> uptake by cement materials has increased from 7.74 <span class="inline-formula">Mt yr⁻¹</span> (95 % confidence interval, CI: 5.84–9.85 <span class="inline-formula">Mt CO₂ yr⁻¹</span>) in 1928 to 0.84 <span class="inline-formula">Gt yr⁻¹</span> (95 % CI: 0.71–1.00 <span class="inline-formula">Gt yr⁻¹</span>) in 2023, and it was projected to rise to 0.86 <span class="inline-formula">Gt yr⁻¹</span> (95 % CI: 0.73–1.02 <span class="inline-formula">CO₂ yr⁻¹</span>) in 2024. The accumulated <span class="inline-formula">CO₂</span> uptake from 1928 to 2023 is 21.26 <span class="inline-formula">Gt CO₂</span> (95 % CI: 17.93–25.17 <span class="inline-formula">Gt CO₂</span>), which offsets about 46 % of the cement process emissions (46.06 <span class="inline-formula">Gt CO₂</span>) in the past 96 years. Simultaneously, the dominance in cement carbon uptake has shifted from the USA, Japan, and some European countries to emerging economies such as China and India, which account for 38.0 % and 9.1 % of total <span class="inline-formula">CO₂</span> uptake, respectively, in the last decade (2014–2023). By analysing the long time series of carbon emissions and uptake of the 42 countries with detailed data, we find that they contributed 82.1 % of global cement <span class="inline-formula">CO₂</span> uptake from 1928 to 2023, including 21 countries for which cement emissions have peaked and 21 countries for which they have not yet peaked. The annual carbon offset level (the ratio of uptake to process emissions in a given year) shows a remarkable decrease due to the temporal lag in cement carbon uptake. This is significant for countries with higher cement imports; for example, the cement industries in Australia and Japan have achieved net-zero emissions when considering the cement carbonation sink. This study provides an accurate bottom-up quantification of cement carbonation sinks at national and global levels. All of the data described in this study are accessible at <a href="https://doi.org/10.5281/zenodo.14583866">https://doi.org/10.5281/zenodo.14583866</a> (Wu et al., 2024).</p>