## 2 Materials and Methods
### Life Cycle Inventory (LCI) Analysis
#### 2.4.5 Module A3 Flows Balance
Electricity provides the energy required to operate the asphalt plant and heat the tank storing the bitumen. In the company's asphalt plant, natural gas is used to heat and dry the aggregates. Diesel and oils are also required for on-site mobile equipment, such as front-end loaders, which feed the aggregates into the asphalt plant. The thermal energy consumption of the asphalt plant is an essential parameter for calculating the environmental impacts of the asphalt mixtures in the study. Two methods were used to calculate this parameter. Method A was chosen to determine the energy consumption of natural gas for heating the aggregates and the bitumen. Much energy is required to turn water into steam or dry the aggregate [69]. The thermal energy (\(TE\)) used to produce the various asphalt mixtures is determined through an energy balance represented by Equation (1). It represents the energy consumed by drying aggregate moisture, heating aggregate, heating stack gases, and casing losses. Thus, this equation considers variations in mixture composition, mixing temperature, aggregates' moisture content, raw materials' initial temperature, aggregates thermal properties, and ambient temperature. \[TE=\left[ \begin{matrix}\sum\limits_{i=1}^{M}m_{aggi}\times C_{agg\ i}\times(t_{ mix}-t_{0})+\sum\limits_{i=1}^{M}m_{aggi}\times W_{agg\ i}\times C_{w}\times(100-t_{0})+\\ +L_{w}\sum\limits_{i=1}^{M}m_{aggi}\times W_{agg\ i}+\sum\limits_{i=1}^{M}m_{aggi }\times W_{agg\ i}\times C_{wap}\times(t_{mix}-100)\end{matrix} \right]\times(1 +CL) \tag{1}\]  
where,  
* \(TE\)--thermal energy (MJ/ton mixture) used to produce 1 ton of asphalt mixture;
* \(M\)--total number of aggregate fractions;
* \(m_{agg\ i}\)--mass of aggregates of fraction \(i\);
* \(C_{agg\ i}\)--specific heat capacity coefficient of aggregate fraction \(i\);
* \(t_{mix}\)--mixing temperature of the asphalt mixture;
* \(t_{0}\)--ambient temperature;
* \(W_{agg}\)--water content of aggregates fraction \(i\);
* \(C_{w}\)--specific heat capacity coefficient of water;
* \(L_{v}\)--latent heat required to evaporate water;
* \(C_{wap}\)--specific heat capacity coefficient of water vapor;
* \(CL\)--casing losses factor. Table 7 shows the values of the parameters used to calculate the thermal energy (\(TE\)) used to produce one ton of asphalt mix. Method B was considered to estimate the electricity consumption per ton of asphalt mixture. The electricity consumption was calculated by dividing the energy consumption (in kWh) by the production of asphalt mixtures (in tons) during 2022. \begin{table}
\begin{tabular}{l l c c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & \multicolumn{1}{c}{**Definition**} & \multicolumn{1}{c}{**Unit**} & \multicolumn{2}{c}{**Quantity**} \\  & & **AC14-NA** & **AC14-RCA** \\ \hline \(t_{0}\) & Ambient temperature & \({}^{\circ}\)C & 14 & 14 \\ \(t_{mix}\) & Mixture temperature & \({}^{\circ}\)C & 175 & 175 \\ \(C_{agg}\) & Specific heat of NA & kJ/kg/\({}^{\circ}\)C & 0.74 & 0.74 \\ \(C_{RCA}\) & Specific heat of RCA & kJ/kg/\({}^{\circ}\)C & - & 1.12 \\ \(W_{agg}\) & Water content of NA & \%/magg & 3 & 3 \\ \(W_{RCA}\) & Water content of RCA & \%/magg & - & 3 \\ \(C_{W}\) & Specific heat of water at 15 \({}^{\circ}\)C & kJ/kg/\({}^{\circ}\)C & 4.1855 & 4.1855 \\ \(L_{v}\) & Latent heat of vaporization of water & kJ/kg & 2256 & 2256 \\ \(C_{cup}\) & Specific heat of water vapor & kJ/kg/\({}^{\circ}\)C & 1.83 & 1.83 \\ \(CL\) & General casing losses factor & \% & 27 & 27 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Parameter values considered in Equation (1). The diesel/oils consumption of the front-end loaders' movements was calculated as a function of these machines' time operation (seconds) to feed one ton of each aggregate to the asphalt plant. The input flow associated with the energy consumption in module A3 of mixture AC14-NA and mixture AC14-RCA is presented in Table 8.