# Carbon Dioxide Uptake by Cement-Based Materials: A Spanish Case Study
## 3 Carbon Dioxide Emissions by the Cement Sector  
Currently, cement production is considered as responsible for approximately 7.4% of the global carbon dioxide emission (2.9 Gtons in 2016). Thus, the cement industry will play a key role in reducing carbon dioxide emissions to minimize climate change. The cement industry has hugely reduced the carbon dioxide emissions per ton of cement from the last century (Figure 5) [4; 5], but the cement production is growing worldwide due to the economic growth, notably in developing countries. Figure 4: World carbon cycle: concentrations of carbon dioxide in the atmosphere [3]. In 2016, the worldwide cement production was about 4.65 Gt (Figure 5) [4], where China produced 52% and the rest of Asia produced 28.5% of the world's production. Europe (The European Cement Association (CEMBUREAU) members) only manufactures 5.3% of the world's cement. Several CO\({}_{2}\) management approaches have been used in the last years in order to lower the climatic change impact and according to the project developed by the World Business Council for Sustainable Development and the Cement Sustainability Initiative (WBCSD-CSI) named \"Getting the Numbers Right\" (GNR). The European Union (EU28) cement industry has significantly decreased the environmental impact [5]. Table 1 shows such sharp decline from 2005 to 2015. Carbon dioxide emissions per ton of clinker are approximately about 825-890 kg CO\({}_{2}\) (Figure 6) [5], when a modern clinker kiln technology is considered. The worldwide average is about 840 kg CO\({}_{2}\). Nevertheless, the medium-term target on carbon dioxide emission levels should be lower than 400 kg per ton of cement. Emission levels of around 350-410 kg per ton of cement have been suggested [6]. The cement industry is working hard to achieve this target by increasing clinker substitution (production of blended cements), the use of alternative fuels and raw materials, and thermal energy efficiency measures. Based on the use of the same technologies of clinker fabrication, these measures will lead to lowering the global average carbon dioxide emissions from 630 kg CO\({}_{2}\)/t cement in 2015 to around 550 kg CO\({}_{2}\)/t cement in 2050, which is far away from the target threshold level of 400 kg per ton of cement. In particular, [PERSON] et al. [7] suggested that the Spanish cement industry is able to lower the carbon dioxide emissions between 2010 and 2050 without carbon capture and storage (CCS) by only 21%. Nevertheless, for this account, carbon dioxide uptake by the mortar and concrete should be taken into account. The use of low CO\({}_{2}\)-intensity cements combined with the consideration of the carbon dioxide uptake by mortars and concretes will allow the sector to meet 550 kg CO\({}_{2}\)/ton of cement target in 2050. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Carbon Dioxide Emissions Reduction (Per** & **Grey Clinker** & **Cmentitious** \\
**Ton of Clinker or Cementtious**) & & \\ \hline Gross carbon dioxide emissions & \(-9\%\) & Data \(-13\%\) \\ Net carbon dioxide emissions & \(-17\%\) & \(-21\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Objectives to decrease the carbon dioxide emissions in the European cement industry [5]. Figure 5: World cement production in 2016 by region and main countries (4.65 Gt) [4]. Figure 6 shows the gross carbon dioxide emissions for grey clinker from 2005 to 2015. The gross carbon dioxide emissions are the direct carbon dioxide emissions, excluding on-site electricity production, minus emissions from biomass fuel sources. Figure 7 shows the CO\({}_{2}\) emissions due to the process and the combustion per ton of cement in several countries from 1990 to 2003 [8]. The weighted average of the carbon dioxide emissions is only decreasing at a slow pace. On one hand, the European countries are proposing new cements including a higher amount of additions, but on the other hand, the USA, among other countries, continues using mainly OPC with a very high clinker/cement ratio.