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A Correction to this paper has been published: https://doi.org/10.1038/s41467-020-20254-5.

The COVID-19 pandemic is impacting human activities, and in turn energy use and carbon dioxide (CO2) emissions. Here we present daily estimates of country-level CO2 emissions for different sectors based on near-real-time activity data. The key result is an abrupt 8.8% decrease in global CO2 emissions (-1551 Mt CO2) in the first half of 2020 compared to the same period in 2019. The magnitude of this decrease is larger than during previous economic downturns or World War II. The timing of emissions decreases corresponds to lockdown measures in each country. By July 1st, the pandemic's effects on global emissions diminished as lockdown restrictions relaxed and some economic activities restarted, especially in China and several European countries, but substantial differences persist between countries, with continuing emission declines in the U.S. where coronavirus cases are still increasing substantially.

The majority of the carbon footprint of the cement industry originates from the decomposition of alkaline carbonates during clinker production. Recent studies have demonstrated that calcium oxides and other alkaline oxides in cement materials can sequester CO2 through the carbonation process and partially offset the carbon emissions generated during cement production. This study employs a comprehensive analytical model to estimate the CO2 uptake via hydrated cement carbonation, including concrete, mortar, construction waste, and cement kiln dust (CKD), covering major cement production and consumption regions worldwide from 1930 to 2023. In 2023, the global annual cement CO2 uptake reached 0.93 Gt/yr (95% CI: 0.80–1.13Gt/yr). From 1930 to 2023, the global cumulative cement CO2 absorption reached 23.89 Gt (95% CI: 20.47–28.74 Gt), equivalent to 52.32% of the CO2 process emissions from cement production during the same period. Our system for estimating cement emissions and uptake is updated annually, providing consistent and accurate data for the cement industry and carbon cycle studies. This data supports improved adaptation to future challenges. [ABSTRACT FROM AUTHOR]

The hydration products of cement materials can absorb atmospheric CO2, 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 58517 activity level data from 163 cement-producing countries and regions worldwide and 6186 carbonation parameters from detailed data records of 42 countries, and project their trend to 2024. The global CO2 uptake by cement materials increases from 7.74 Mt yr-1 (95 % confidence interval, CI: 5.84–9.85 Mt CO2 yr-1) in 1928 to 0.84 Gt yr-1 (95 % CI: 0.71–1.00 Gt yr-1) in 2023, and projected to rise to 0.86 Gt yr-1 (95 % CI: 0.73–1.02 CO2 yr-1) in 2024. The accumulated CO2 uptake from 1928 to 2023 is 21.26 Gt CO2 (95 % CI: 17.93–25.17 Gt CO2), which offsets about 46 % of the cement process emission (46.06 Gt CO2) in 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 CO2 uptake, respectively, in the last decade (2014–2023). By analyzing the long time-series carbon emission and uptake of the 42 countries with detailed data, we find they contributed 82.1 % of global cement CO2 uptake from 1928 to 2023, including 21 peaked countries and 21 non-peaked countries in cement emissions The annual carbon offset level (the ratio of uptake to process emission in a given year) shows a remarkable decrease due to the temporal lag of cement carbon uptake. This is significant for countries with higher cement imports, for example, the cement industry in Australia and Japan have achieved net-zero when considering the cement carbonation sink. This study provides a precise bottom-up quantification to cement carbonation sinks at national and global levels. All the data described in this study are accessible at https://doi.org/10.5281/zenodo.13827861 (Wu et al., 2024). [ABSTRACT FROM AUTHOR]

With the vigorous promotion in China of efforts to reduce pollution and carbon emissions, examining their synergies becomes increasingly crucial. This study used the multi-regional input–output (MRIO) table to build the consumption-based industrial emissions inventories of CO2 and three major air pollutants (PM2.5, NOx, and SO2) and constructed synergistic emission indices of the intensity and magnitude to identify and evaluate the synergy between carbon emissions and air pollutants in inter-industrial trade among 30 provinces in mainland China. The results show that more than 85% and 40% of inter-provincial and inter-industrial trades have synergistic emissions between CO2 and air pollutants, respectively. We identified 77 inter-provincial trades and 84 inter-industrial trades among provinces with strong synergistic emissions. They are mainly reflected in the demand of the construction industry in Zhejiang and Guangdong for the nonmetal mineral products manufacturing industry in Henan, and the metal smelting and processing industry in Hebei, along with the demand of the service industry in Beijing for the electric power, steam, and hot water production and supply industry in Inner Mongolia. Our study provides new insights into the synergistic reduction of CO2 and air pollutants within the supply chain, thereby enriching the discourse on regional and industrial synergies in achieving sustainable development goals. [ABSTRACT FROM AUTHOR]

Nearly three-quarters of the growth in global carbon emissions from the burning of fossil fuels and cement production between 2010 and 2012 occurred in China. Yet estimates of Chinese emissions remain subject to large uncertainty; inventories of China's total fossil fuel carbon emissions in 2008 differ by 0.3 gigatonnes of carbon, or 15 per cent. The primary sources of this uncertainty are conflicting estimates of energy consumption and emission factors, the latter being uncertain because of very few actual measurements representative of the mix of Chinese fuels. Here we re-evaluate China's carbon emissions using updated and harmonized energy consumption and clinker production data and two new and comprehensive sets of measured emission factors for Chinese coal. We find that total energy consumption in China was 10 per cent higher in 2000-2012 than the value reported by China's national statistics, that emission factors for Chinese coal are on average 40 per cent lower than the default values recommended by the Intergovernmental Panel on Climate Change, and that emissions from China's cement production are 45 per cent less than recent estimates. Altogether, our revised estimate of China's CO2 emissions from fossil fuel combustion and cement production is 2.49 gigatonnes of carbon (2 standard deviations = ±7.3 per cent) in 2013, which is 14 per cent lower than the emissions reported by other prominent inventories. Over the full period 2000 to 2013, our revised estimates are 2.9 gigatonnes of carbon less than previous estimates of China's cumulative carbon emissions. Our findings suggest that overestimation of China's emissions in 2000-2013 may be larger than China's estimated total forest sink in 1990-2007 (2.66 gigatonnes of carbon) or China's land carbon sink in 2000-2009 (2.6 gigatonnes of carbon).

Because of the alkaline nature and high calcium content of cements in general, they serve as a CO2 absorbing agent through carbonation processes, resembling silicate weathering in nature. This carbon uptake capacity of cements could abate some of the CO2 emitted during their production. Given the scale of cement production worldwide (4.10 Gt in 2019), a life-cycle assessment is necessary in determining the actual net carbon impacts of this industry. We adopted a comprehensive analytical model to estimate the amount of CO2 that had been absorbed from 1930 to 2019 in four types of cement materials including concrete, mortar, construction waste and cement kiln dust (CKD). Besides, the process CO2 emission during the same period based on the same datasets was also estimated. The results show that 21.12 Gt CO2 (18.12-24.54 Gt CO2, 95% CI) had been absorbed in the cements produced from 1930 to 2019, with the 2019 annual figure mounting up to 0.90 Gt CO2 yr-1 (0.76-1.07 Gt CO2, 95% CI). The cumulative uptake is equivalent to approx. 52% of the process emission, based on our estimation. In particular, China's dominant position in cement production/consumption in recent decades also gives rise to its uptake being the greatest with a cumulative sink of 6.21 Gt CO2 (4.59-8.32 Gt CO2, 95% CI) since 1930. Among the four types of cement materials, mortar is estimated to be the greatest contributor (approx. 58%) to the total uptake. Potentially, our cement emission and uptake estimation system can be updated annually and modified when necessary for future low-carbon transitions in the cement industry. All the data described in this study, including the Monte Carlo uncertainty analysis results, are accessible at https://doi.org/10.5281/zenodo.4064803. [ABSTRACT FROM AUTHOR]