# Carbon Dioxide Uptake by Brazilian Cement-Based Materials
## 3 Method to Estimate the Carbon Dioxide Removals Due to Carbonation  
Within the Intergovernmental Panel on Climate Change (IPCC) reporting, a Tier represents the level of methodological complexity utilized to estimate greenhouse gas emissions for a specific source. Accordingly, Tier 1 is the basic methodology designed for all categories and ready to be used. Consequently, it is feasible for all countries. The 2006 IPCC Guidelines for National Greenhouse Gas (GHG) Inventories to report the GHG emissions give guidance on the choice of the most suitable method to estimate calcination emissions during the clinkerization process, based on national circumstances, and on how to estimate calcination carbon dioxide emissions at each Tier [37]. The Tier 1 methodology followed in the present study utilizes a generalized carbon dioxide uptake factor as shown in Equations (1) and (2). These equations consider the carbon dioxide uptake by mortars and concrete during their whole service life cycles. Tier 1 is a basic adjustment method to obtain a removal estimate as described in the 1996 IPCC Guidelines [37]. This method is applicable if activity data are available from national sources. The Intergovernmental Panel on Climate Change (IPCC) Tier 1 approach, in which default values are used, is a simple procedure and can be considered as a first step to estimate the carbon dioxide uptake by cement-based materials (mortars and concretes). There is no country in South America where Tier 1 is currently used. It is therefore of great importance to begin the expeditious implementation of this basic method in the zone. Based on the studies found in the literature [38; 39], we have considered the carbon dioxide uptake in the use stage (20%), during the end-of-life (2%), and for the secondary use (1%). \[\text{Carbon dioxide uptake}=(0.20+0.02+0.01)\times\text{CO}_{2}\text{ emissions from calcination} \tag{1}\]  
\[\text{Carbon dioxide uptake}=0.23\times\text{national CO}_{2}\text{ emissions from calcination} \tag{2}\]  
It is well-known that mortars used for rendering applications will carbonate more rapidly than concretes, i.e., rendering mortars will remove carbon dioxide in a short period of time. Accordingly, when a high proportion of the cement consumption is used as mortar, i.e., more than 10% but less than 30% (10%-30%), for the carbon dioxide uptake a correction factor should be applied as follows (Equation (3)). The source of the coefficients given in this Equation is the study entitled \"CO\({}_{2}\) Uptake in Cement-Containing Products. In Background and Calculation Models for IPCC Implementation\" [39]. \[\text{Carbon dioxide uptake}=((0.20+0.02+0.01)+(0.0115\text{ (mortar factor}-10)))\times\text{CO}_{2}\text{ emissions from calcination} \tag{3}\] \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Indicator** & **2014** & **2030** & **2050** \\ \hline Clinker factor (clinker/cement ratio) & 0.67 & 0.59 & 0.52 \\ Thermal consumption (GJ/t clinker) & 3.50 & 3.47 & 3.20 \\ Electrical consumption (kWh/t cement) & 113 & 106 & 91 \\ Alternative fuels (\% of thermal substitution) & 14.8\% & 35\% & 55 \\ Global carbon dioxide emissions (Mt CO\({}_{2}\)/year) & 40 & 42 & 44 \\ Carbon dioxide emissions intensity (kg CO\({}_{2}\)/t cement) & 564 & 485 & 375 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Key indicators for the Brazilian cement industry by 2030 and 2050 within the 2 \({}^{\circ}\)C scenario. where the mortar factor is the percentage for rendering the mortar of the total clinker usage. This value will be 10 when the rendering mortar factor is below 10% and 30 when this value is above 30%. Summing up, in the last Equation, carbon dioxide uptake can be assessed as a four-terms equation, corresponding to the service life period (20%), end-of-life (2%), secondary use (1%), and then is broadened with an additional term for the mortar. The reason for this is because of the great difference between mortar and concrete regarding the carbonation rate as explained below. According to [PERSON] et al.