## 5 Case Study: LCA Results and Discussion
### Environmental Assessment
Although it represents a small percentage of waste incorporation (4%) replacing limestone, differences appear in the impact of limestone powder and its transport, meaning that the incorporation and transport of waste still allows a reduction in the impacts in all categories, varying between 18% and 93%, compared to the linear solution of limestone and its transport, respectively. This reduction in transport impacts is due to the reduction in the transport distance between the limestone powder and waste cases (78 km down to 30 km). However, if we consider just the pretreatment stage of wastes in the circular solution (Tables 10 and 11), it produces more impacts than just sending them to landfill (linear solution) (Table 5), except in the eutrophication category. The variation in the remaining categories is higher than the linear case by about 48% to 87% and 41% to 54% for dregs and grits, respectively. This difference in variation is explained by the consumption of resources in drying the dregs to eliminate initial moisture (50% for dregs and 16% for grits). Furthermore, it is necessary to use sieving to produce an aggregate like the traditional raw material. Tables 13 and 14 show the impacts associated with pretreatment, as well as the impacts of the production and application of the bituminous mixture with dregs and grits, respectively. The difference in impacts of the linear and circular solution of the top road layer is achieved by the partial elimination of impacts associated with the use of limestone, since the impact with the alternative raw material transport (dregs and grits) relative to limestone balances the impacts produced in the waste pretreatment stage. Even with the waste being subjected to pretreatment operations (transport, drying, sieving), the impacts show a clear tendency to decrease in all parameters. Bitumen impacts are of course still high compared to other raw materials (crushed stone, limestone, granite, and filler). The use of other wastes as alternative raw materials for other components should be explored to further minimize overall impacts without degrading performance characteristics. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Category**} & \multirow{2}{*}{**Unit**} & \multirow{2}{*}{\begin{tabular}{c} **Dregs Pre-** \\ **treatment** \\ \end{tabular} } & \begin{tabular}{c} **Bituminous** \\ **Mixture** \\ **(Dregs)** \\ \end{tabular} & \multirow{2}{*}{\begin{tabular}{c} **Asphalt** \\ **Pavement** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Total** \\ **Linear** \\ **Model** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Impact** \\ **Reduction** \\ **with Circular** \\ **Model** \\ \end{tabular} } \\ \hline GWP & kg CO\({}_{2}\) eq & \(1.23\times 10^{-1}\) & 4.24 & \(8.16\times 10^{-1}\) & 5.18 & 1.5\% \\ ODP & kg CFC\({}^{-11}\) eq & \(1.92\times 10^{-8}\) & \(4.20\times 10^{-6}\) & \(1.54\times 10^{-7}\) & \(4.37\times 10^{-6}\) & 0.4\% \\ AP & kg SO\({}_{2}\) eq & \(8.87\times 10^{-4}\) & \(3.57\times 10^{-2}\) & \(6.36\times 10^{-3}\) & \(4.29\times 10^{-2}\) & 0.3\% \\ EP & kg PO\({}_{4}\) eq & \(1.84\times 10^{-4}\) & \(5.66\times 10^{-3}\) & \(1.41\times 10^{-3}\) & \(7.25\times 10^{-3}\) & 99.5\% \\ POFP & kg NMVOC & \(1.33\times 10^{-3}\) & \(3.40\times 10^{-2}\) & \(1.18\times 10^{-2}\) & \(4.71\times 10^{-2}\) & 0.5\% \\ ADP & kg Sb eq & \(2.80\times 10^{-9}\) & \(3.29\times 10^{-7}\) & \(2.52\times 10^{-8}\) & \(3.57\times 10^{-7}\) & 0.1\% \\ ADP (fossil & MJ & 1.66 & \(3.33\times 10^{2}\) & \(1.20\times 10^{1}\) & \(3.46\times 10^{2}\) & 0.3\% \\ WU & m\({}^{3}\) & \(2.06\times 10^{-2}\) & \(2.28\) & \(4.82\times 10^{-2}\) & 2.35 & 0.2\% \\ CED & MJ & 2.01 & \(3.64\times 10^{2}\) & \(1.28\times 10^{1}\) & \(3.79\times 10^{2}\) & 0.3\% \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Environmental impacts for dregs pretreatment plus dregs bituminous mixing and total impacts of circular model for asphalt pavement. Figure 5: Environmental improvements achieved by the circular model.