In this study, national cement clinker production data and emission factors were used to calculate carbon emissions from cement production processes. The cement clinker production data for 163 countries and regions were obtained from two sources. The first source comprised direct cement clinker production data submitted to the United Nations Framework Convention on Climate Change (UNFCCC) by 43 countries. The second source comprised estimated cement clinker production data derived by multiplying the clinker-to-cement ratio (the ratio of cement clinker production to cement production) by cement production. Cement production data for 163 countries and regions from 1928 to 2022 were accessed from the United States Geological Survey (USGS: Cement statistics and information, 2025). For the year 2023, the cement production data were updated from the CCF2Up database website (https://ccf2up.com/, last access: 4 August 2024). For countries lacking updated data for 2023 and all countries in 2024, projections were made based on historical data (see Sect.  for forecasting methods). The cement-to-clinker ratio data for China and India aligned with our prior research (Xi et al., 2016; Guo et al., 2021; Huang et al., 2023). For other countries, the ratios were estimated using the methods outlined by Andrew (2020): utilizing a 95 % clinker-to-cement ratio for the years before 1970 and employing linear interpolation to estimate the ratio for the period after 1970, based on the assumption of steady increases in clinker substitution over time. Country-specific cement emission factors are obtained from the UNFCCC for 43 countries. For those not listed in the database, the default value of 0.507 kgCO2 per tonne of clinker provided by the Intergovernmental Panel on Climate Change (IPCC, 2006) was used.

To provide a more accurate national-level database of carbon uptake by cement, data updates have been made in this study, based on previous work (Huang et al., 2023), and the following modifications have been incorporated:

Cement consumption for 163 countries and regions has been updated. Cement consumption in different countries was adjusted using import and export data (accessed on the UN Comtrade Database at https://comtradeplus.un.org/, last access: 2 June 2024) for cement clinker, based on the cement production data collected and estimated for each country.

The methodology recommended by the IPCC is widely used for estimating CO2 emissions from industrial processes. In this study, we used the Tier-2 method to estimate country-specific emissions (Eq. ): 4Eprocess,i=Pcement,i×fclinker,i×EFCO2,i, where Eprocess,i represents process CO2 emissions from the cement industry in country i, Pcement,i refers to the weight (mass) of cement produced, fclinker,i is the clinker-to-cement ratio, and EFCO2,i is the country-specific emission factor for clinker.

We employ the national geographic boundary as the accounting boundary for cement carbon uptake, aligning with the accounting methods for carbon emissions from cement production. The accounting model for cement CO2 uptake (Table ) in this study adheres to the model constructed in our prior research, which can be summarized as follows: 5C=W×f×γ×F×M,6W=Pclinker-Ex+Im,7F=d/D,8d=k×t,9k=βcsec×βad×βCO2×βcc.

In the expressions above, C is the carbon uptake by cement materials; W is the clinker consumption, which is adjusted by clinker production (Pclinker) with its exports (Ex) and imports (Im) (Eq. ); f is the proportion of CaO in cement clinker; γ is the fraction of CaO converted to CaCO3 of cement material; and F is the annual carbonation proportion, which is the percentage of the carbonation depth (d) in the accounting year compared to the theoretical maximum carbonation depth (D) (Eq. ). Based on Fick's diffusion law (Eq. ; You et al., 2022), the carbonation depth of cement is the product of the carbonation rate (k) and the square root of time. The carbonation rate in the model is calculated by considering the impact of exposure conditions (βcsec), cement additives (βad), the CO2 concentration (βCO2), and coating and cover (βcc) (Eq. ). M is the molar mass ratio of CO2 to CaO (44/56≈0.786).

Considering the carbon uptake mechanism of cement in different life cycles, cement carbon uptake has been categorized into four types: (1) concrete use, (2) mortar use, (3) construction loss, and (4) cement kiln dust (CKD) landfills. For concrete, the whole life cycle of concrete services, demolition, and secondary-use (including both disposal in a landfill and recycling) is considered when calculating the carbon uptake. For cement mortar, there are three kinds of use: rendering and plastering mortar, maintenance and repairing mortar, and masonry mortar. Concrete and mortar loss are both carbon sinks for construction-loss cement. The carbon uptake of CKD occurs during landfill disposal. Table  lists the carbon sequestration accounting equations for different cement materials.

We provide a projection of cement process carbon emissions and uptake for 163 countries and regions for the year 2024. We use the autoregressive integrated moving average model, or “ARIMA(p,d,q)”, which is a time-series analysis method commonly used for yield forecasting. This regression-based model forecasts values by regressing the variable's past values using various lag lengths, along with the current and past values of the error term (Cox and Vladescu, 2023). Based on extensive long-term cement production data spanning from 1928 to 2023 for 163 countries and regions, we use the ARIMA model to forecast cement production for the year 2024 and then cross-validate the model (see “SI data 1” in Table S1 for details). Our forecasts are further validated by industry economic reports from major cement-producing nations. For example, the “2023 Cement Industry Economic Operation Report” published by the China Cement Association (CCA, 2024) considered upstream raw materials prices and the downstream real estate market and projected a 2 %–3 % decline in cement production by 2024. This prediction aligns with our model's 2.1 % decline. Similarly, for the USA, the USGS provided monthly data on cement production, showing a 4 % year-over-year decline in the first half of 2024, which is consistent with our model's trend prediction. The 2024 cement clinker consumption data are adjusted based on import and export data in recent years and used to forecast cement carbon uptake in 2024.

We employed the Monte Carlo method suggested by the IPCC to simulate cement carbon emissions and uptake 10 000 times in order to assess the uncertainty in cement production process emissions and carbon sequestration in cement materials. The results of the uncertainty accounting are given in Table S4 in the Supplement (available from 10.5281/zenodo.14583866, Wu et al., 2024). We identified 24 variables that contribute to uncertainty in cement carbon uptake. This count is two less than previous version due to the revised cement clinker production and clinker-to-cement ratio. The 24 variables include the following: 3 variables related to cement clinker, namely the CaO content, MgO content, and proportion of CaO converted to CaCO3; 10 variables for concrete, including the strength class, proportion of cement for concrete, carbonation rate, building lifespan, particle size distribution, demolition exposure time, and correction factor; 6 variables for mortar, including the proportion of cement for mortar, type of utilization, mortar thickness, and carbonation rate; 2 variables for building loss, including the utilization ratio and carbonation period; and 3 variables for CKD, including the production rate, landfill ratio, and CaO content.

Compared to our previous study, this study reduces the uncertainty in global cement carbon uptake estimations. The improvements in accuracy are reflected in three aspects:

The activity data used in this study are based on the annual apparent consumption of cement clinker in each country, which is adjusted by the international trade (import–export) of clinker. These updated national-level activity data reduce the uncertainty range of [-30.0 %, 30.6 %] in previous estimations, which arose due to the approximated substitution of cement production data for consumption data.

In this study, we gathered carbonation parameters from 42 countries to enrich the cement uptake accounting model. Figure  shows the share of cement CO2 uptake for 42 countries and the rest of the world (ROW) during the period from 1928 to 2023. The accumulated carbon uptake by cement in these 42 countries was 16.60 GtCO2 over the past 96 years, accounting for 78.1 % of the global total. Their contributions peaked in 1928 (95.6 %) and were minimal in 1984 (72.9 %). It is evident that cement CO2 uptake by China and other emerging economies, including South Africa, Indonesia, Vietnam, Korea, India, Türkiye, Mexico, and Brazil, has gradually replaced the leading roles played by the USA, Japan, and Canada as well as European countries like the United Kingdom, Spain, Italy, Germany, France, and Belgium after 1982. Specifically, the USA was the largest contributor to cement carbon uptake, with an average contribution of 23.6 %, between 1928 and 1991. From 1928 to 1966, Germany and the United Kingdom were major contributors alongside the USA, with respective contributions of 8.7 % and 6.9 %. From 1967 to 1982, Japan became the second-largest contributor, with an average contribution of 8.2 %. Subsequently, between 1983 and 1991, China replaced Japan with an average contribution of 11.9 %. Since 1992, China has been the country with largest cement carbonation sink, reaching a maximum contribution of 43.5 % in 2020. Additionally, since 2008, India has been the second-largest contributor, replacing Japan's position during 1992–2006. In 2023, the cement carbon uptake values in China and India were 0.33 GtCO2yr-1 (38.0 % of global, CI: 0.25–0.41 Gtyr-1) and 0.07 GtCO2yr-1 (9.1 %, 0.06–0.09 Gtyr-1), respectively.

Based on the clinker production data for 163 countries and regions worldwide and the carbonation parameters for 42 countries, we estimated and projected the carbon uptake across these 163 entities. From the spatial distribution of the cement CO2 uptake in 2024 (Fig. ), we found that the dominant countries with respect to carbon uptake by cement are still distributed in Asia, particularly due to the region's high demand for infrastructure development. China leads the global carbon uptake charge, with 326.84 MtCO2 (44.0 % of the total), followed by India and Saudi Arabia, with 78.25 and 43.76 MtCO2, respectively. Japan and South Korea are ranked 7th and 10th, with sequestration values of 25.99 and 19.33 MtCO2, respectively. Southeast Asian countries like Vietnam, Indonesia, Thailand, the Philippines, and Laos also contribute significantly, sequestering 19.91, 17.54, 9.34, 7.68, and 5.68 MtCO2, respectively. For the Americas, the main countries with respect to CO2 uptake are the USA, Brazil, Mexico, and Canada, with 37.91, 11.03, 10.53, and 5.20 Mt, respectively; these countries are ranked 4th, 12th, 14th, and 28th in the world with respect to uptake. In Africa, cement carbon uptake is concentrated in Egypt, Nigeria, Algeria, and South Africa, which sequester 7.49, 4.30, 4.17, and 2.53 MtCO2, respectively. In Europe, key countries for CO2 sequestration via cement are Germany, Italy, France, Spain, the United Kingdom, and Poland, with values of 11.00, 6.82, 6.35, 5.97, 5.11, and 4.46 Mt, respectively.

In this study, we enriched the national cement process carbon emission and uptake database. We categorized the countries into two sets according to the trends in their cement process carbon emission curves (Table ). Group 1 comprises 21 countries in which the process carbon emissions have shown a peak in their emission trend during 1928–2024. These countries can be further divided into two categories based on their net emission trends: 9 countries with a neutral trend (category a1) and another 12 countries that have peaked but do not exhibit a neutral trend (category a2). Meanwhile, Group 2 includes 21 countries in which the process carbon emissions are still increasing and have not yet peaked, but their net emission trends encompass both countries that have reached a peak (“peaked”, category-b1 countries) and countries that have not yet reached a peak (“non-peaked”, category-b2 countries), comprising 4 and 17 countries, respectively.

Figure  shows cement process carbon emissions and uptake for 42 countries from 1928 to 2024. Group 1 (Fig. a) predominantly comprises European countries, which were early producers and consumers of cement. In category-a1 countries, carbon emissions from cement production have peaked and followed a steady decline, but carbon sinks from cement consumption in these countries have not decreased, resulting in net-zero or even negative emissions with increasing uptake. For instance, cement process emissions in Australia peaked at 2.91 Mt in 1974 and then decreased at an average rate of 0.8 %. In contrast, Australia's cement carbon uptake was 1.17 Mt in 1974 (offset level 40.3 %) and then continued to rise, especially from 2000 to 2024, with an average rate of increase of 3.3 %. By 2009, net cement emissions had become negative (-0.02 MtCO2yr-1), and they reached -2.7 MtCO2yr-1 in 2024. This is due to the fact that, despite Australia producing less clinker than it used to, the country's cement consumption has not decreased owing to substantial clinker imports, with an import penetration ratio of 52.8 % in 2023. Countries like the Netherlands, Japan, the United Kingdom, Hungary, Italy, France, Czechia, and Germany have exhibited similar trends. In category-a2 countries, the net emissions are not yet neutral, but offsets from cement carbon sequestration effectively reduce actual cement emissions. For instance, in most category-a2 countries, like Sweden, Luxembourg, Finland, Norway, and Belgium, the increase in cement carbon uptake outpaces the growth of process carbon emissions, leading to a rapid decline in net emissions after the peak year.

In Group-2 countries (Fig. b), the cement process emissions have not peaked. However, net emissions have peaked in category-b1 countries, such as the USA, South Korea, Austria, and Denmark, due to carbon sequestration by cement consumption. For instance, due to a constant demand for cement in the USA, process carbon emissions are expected to have reached 39.57 MtCO2 in 2024. However, as the leading importer of cement, the USA has shown a peak in the trend in net emissions when considering the carbon uptake of cement. Specifically, from 2009 to 2024, the average carbon offset level in the USA has been 89.0 %. The non-peaked (category-b2) countries are primarily developing countries, and their cement production and consumption have expanded significantly, albeit later than Group-1 countries. China, India, Vietnam, Iran, and Indonesia are notable examples, having experienced rapid growth in cement demand after the 1980s. The accumulated carbon uptake from cement in these countries between 1980 and 2023 accounts for more than 95 % of their totals from 1928 to 2023. Notably, Saudi Arabia has recently witnessed a sharp increase, with 39.21 Mt of cement CO2 uptake in 2023, an 1.7-fold increase compared to 2020, likely due to its recent economic diversification policies. Due to the higher production and lower imports in category-b2 countries, the trends in process emissions and uptake from cement in these countries are similar, with net emissions increasing in line with the process emissions. It is worth mentioning that some countries in category b2 have shown decreasing trends in recent years. For instance, the cement process emissions in China, Brazil, and Ireland have decreased for 3 consecutive years (2022–2024). However, these decreases primarily stem from the decline in cement production, rather than from offsets in the cement carbonation sink, as their carbon uptake values also show a decreasing trend, with projections of -1.1 %, -1.1 %, and -5.0 % for 2024, respectively. In summary, the carbon offset by cement CO2 uptake is more significant in peaked countries than in non-peaked countries. Nowadays, many studies have indicated carbon leakage due to outsourcing from these peaked countries (Allevi et al., 2017; Grubb et al., 2022), and our results show that the gap in cement process carbon emissions between countries will further widen if the carbon uptake is taken into account.

A time lag in cement process carbon emissions and uptake exists among different countries. The majority of Group-2 countries are in the initial phases of cement production compared to Group-1 countries. As shown in Fig. , the trends for four countries are comparable with respect to cement production levels but vary with respect to their peak years. Germany and France, which began using cement before 1930, experienced a rapid increase in cement process carbon emissions and uptake during 1950s–1970s, peaking in the 1970s. Korea and Ireland has similar trends, although with about a 20-year time lag.

This study uses the Monte Carlo method to simulate carbon uptake from cement 10 000 times in order to evaluate the uncertainty. The results reveal that the 95 % confidence interval for accumulated carbon uptake spanning from 1928 to 2024 ranges from 17.93 to 25.17 Gt CO2. The uncertainties associated with carbon sequestration from cement for each country are detailed in Table S4 in the Supplement. Our accounting is based on the accounting model of Xi et al. (2016), and the variable entries and sensitivity values are basically consistent with this prior work (Fig. ). A key difference in our approach is that we have removed the two variables of “Proportion of clinker in cement” and “Ratio of cement consumption to production”, as we use a more accurate cement clinker consumption in this study. For specific parameters, “CaO content in clinker” (92.0 %) has the greatest impact on the scale of carbon absorption, as it widely affects the carbon absorption in all stages of cement consumption; moreover, “Proportion of cement used for concrete or mortar” and “Proportion of CaO converted to CaCO3 in concrete or mortar” are also important, with sensitivity values of 66.4 %, and 67.09 %, respectively, due to the fact that these two parameters each affect all stages of carbon absorption by concrete and mortar, and concrete and mortar account for the largest proportion of the total carbon absorption of cement materials. Other parameters have lower sensitivity values, mostly below 10 %, because they only have a slight impact on the local accounting results of the model. Therefore, it is essential to prioritize the more sensitive parameters and ensure their accurate collection and measurement across different countries in order to further minimize the uncertainty in the model's accounting results.