# Comparative \"from Cradle to Gate\" Life Cycle Assessments of Hot Mix Asphalt (HMA) Materials
## 2 Data and Methods
### Inventory Analysis Phase: Secondary Data  
After reviewing several LCI databases available in the literature for LCIA, the following information was selected for the analyses:  
* For aggregates, the Environmental Impact Categories of \"from cradle to gate\" analysis defined by the Union Nationale des Producteurs de Granulats [46; 47] were used. * For bitumen and fuels, the Life Cycle Inventory of Bitumen published by Eurobitume [48] was selected. * For transport, the data of exhaust gas emission standards were obtained from the current Italian and European regulations [50; 51; 52]. Specifically, the data included information of the European and Italian standards and limits for the emissions of carbon dioxide, carbon oxide, hydrocarbon, and mono-nitrogen oxides. * For earth-moving machines, data published by [PERSON] [53] were considered. In this phase, the LCI does not provide CO\({}_{2}\) emissions from the manufacturing process. However, the annual consumption of methane gas allows calculating the emissions of carbon dioxide that results from burning methane gas for Company 1. The stoichiometric combustion reaction of methane is (Equation (1)). \[\mathrm{CH_{4}+2O_{2}\to CO_{2}+2H_{2}O} \tag{1}\]  
Considering the following molecular mass of the substances, it is then possible to calculate the corresponding CO\({}_{2}\) emissions, as follow (Equation (2)). \[1\;\mathrm{kg}\;\mathrm{CH_{4}+4\;kg\;O_{2}\to 2.75\;kg\;CO_{2}+2.25\;kg\;H_{2}O} \tag{2}\]  
Similarly, the annual consumption of low-sulfur oil and gasoil for Company 2 allows calculating the emissions of carbon dioxide resulting from the burning processes. According to the Italian Ministry of the Environment [54], the CO\({}_{2}\) emissions for each ton of asphalt mix produced are (Equation (3)). \[C_{e}=Q\cdot EF\cdot NCV\cdot O_{f} \tag{3}\]  
where \(C_{e}\) is the quantity of CO\({}_{2}\) emission due to fuel combustion, \(Q\) is the quantity of fuel consumed, \(EF\) is the emission factor, \(NCV\) is the net calorific value of fuel and \(O_{f}\) is the oxidation factor, representing the fraction of carbon oxidized during combustion. Table 6 lists the values used for this calculation. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Substance** & **Concentration** & **Mass Flow** \\  & **(mg/Nm\({}^{3}\))** & **(g/h)** \\ \hline \hline Particulates & 2.6 & 95.66 \\ \hline Volatile Organic Compounds & \textless{}1 & \textless{}36.79 \\ \hline Nitrogen oxides (NO\({}_{\mathrm{x}}\)) & 75 & 2759.33 \\ \hline Sulfur oxides (SO\({}_{\mathrm{x}}\)) & 48 & 1765.97 \\ \hline Hydrogen chloride (HCl) & \textless{}1 & \textless{}36.79 \\ \hline Hydrogen fluoride (HF) & \textless{}0.1 & \textless{}3.68 \\ \hline Cadmium (Cd) + Thallium (TI) & \textless{}0.01 & \textless{}0.37 \\ \hline Mercury (Hg) & \textless{}0.01 & \textless{}0.37 \\ \hline Antimony (Sb) + Arsenic (As) + Lead (Pb) + Chrome (Cr) + Cobalt (Co) + Copper (Cu) + Manganese (Mn) + Nickel (Ni) + Vanadium (V) + Tin (Sn) & \textless{}0.002 & \textless{}0.07 \\ \hline Polycyclic aromatic hydrocarbons & \textless{}0.002 & \textless{}0.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Emissions generated by Company 2. The obtained values of CO2, which do not contain biogenic CO2 emissions, refer to the declared unit of asphalt concrete. The environmental analysis also requires using available data for the construction of homogeneous environmental profiles for the considered materials, machines and processes. According to the defined system boundaries, the authors collected six types of environmental profiles for the different elements considered in the analysis, as follows:  
* limestone [46];
* recycled aggregate [47];
* bitumen [48];
* asphalt plant (smokestacks emissions);
* articulated lorry [51]; and
* earth-moving machine [53]. As an example of these profiles, Table 7 presents the air emissions of \(1\) Mg of limestone material.