# Comparative \"from Cradle to Gate\" Life Cycle Assessments of Hot Mix Asphalt (HMA) Materials
## 4 Discussion
The results of _POCP_ are the same for both mixes, suggesting that the use of different fuel sources in the manufacturing process does not influence this environmental impact. The results highlight that more than 90% of the total emissions in both companies are related to raw materials and fuel processes (A1 stage). The item related to internal transport processes included in the A2 stage represents 6% of the total _POCP_ results, while the A3 stage contributes to 1%. In terms of the Abiotic Depletion Potential (_ADP_) for fossil resources, the results for both companies were found to be the same. The contribution of the consumption of fossil resources is about half of the total environmental impact and it is correctly attributed to the A1 phase, according to the EN 15804 [42]. Finally, for the distribution of Human Toxicity Potential (_HTP_) emissions, it was found that the contribution of the A2 phase is negligible, whereas the incidence of raw materials (A1 phase) strongly influences the results. In fact, the analysis showed that the average result for the aggregates-related emissions is 70%, and for the bitumen is 6%. In this case, it is also important to observe that the contribution of the A1 stage to the total _HTP_ emissions where 15% lower for Company 1, while the contribution of the A3 stage to the total _HTP_ in Company 1 was 1.6 larger than for Company 2. These results could be explained by the chemical composition of fuels: pollutants contained in gasoil and low-sulfur crude oil have higher impact on the _HTP_ emissions than the ones contained in natural gas. As can be observed from the previous analysis, the LCAs herein conducted permitted to identify the contribution of the different stages related to the production of both asphalt mixtures (i.e., from the acquisition of the raw materials and fuel supplies to the final production of the mixes themselves), to a diverse set of environmental impact factors. The results demonstrate that there are important differences in the environmental performance of the two HMA materials, and that these differences go beyond the specific results obtained for the CO\({}_{2}\) emissions. This is an important observation since several documents available in the literature have quantified the environmental impact of asphalt mixes using the computation of greenhouse gas emissions and, particularly, CO\({}_{2}\) emissions (e.g., [34; 61]). However, as demonstrated in this work, the Global Warming Potential (_GWP_) is only one--though the most famous--of the environmental categories to be considered when evaluating the environmental impact of a product. Indeed, the experience gained in this area suggests that the exclusive consideration of CO\({}_{2}\) emissions limits the possibility of conducting an integral LCA, and promotes the chances of selecting of a low CO\({}_{2}\) material that could present unacceptable environmental burdens. The Italian Ministry of the Environment is taking measures in this regard, since it is currently discussing the MEC for road construction and maintenance. The implementation of NAP GPP would probably consider the type III label as a rewarding parameter in public bids. This, in turn, will be useful not only for protecting the environment, but also for improving and updating the technology used and boost competitiveness.