## 3 Results
### A Hotspot Analysis on PV Wastes' EoL  
Figure 3 offers a comparison between the environmental impacts associated with EoL phase of c-Si, CdTe, and CIGS. For each technology, we analyzed the impact of recycling process, transportation, and landfilling (waste sludge, or contaminated glass etc.) of materials. Figure 3 indicates that transportation associated CO2 emissions are important in considering the entire EoL phase of different PV technologies. The results show that the CIGS PV module has the highest CO2-eq emissions per m\({}^{2}\) of module. This is because the transportation associated emissions are linearly proportional with the mass of the PV panel and PV panels with higher mass per m\({}^{2}\) area (given in Table 2) have the highest impacts. For example, about 47% of the PV EoL management impacts of c-Si technology is contributed by the transportation of PV panels for a total of 1000 km at their EoL phase,  
Figure 3: Carbon footprint of PV end-of-life (EoL) management. e.g., between installation locations and recycling center, and recycling center and landfill. Such a distance can be considered somewhat above of the average transportation distance where the adequate infrastructure and the policies that mandate the recycling exist (e.g., for European countries), it is, on the contrary, far below of realistic transportation distance averages in many countries. For example, the only full-fledged PV recycling center of the US is in Perrysburg, Ohio (northeast of the US) while most of the PV is deployed in Arizona, New Mexico, and California (southwest of the US). The average transportation between these deployment locations to Ohio is >3000 km. Altering the transportation component analysis performed in Figure 3 using 3000 km instead of 1000 km will triple the CO\({}_{2}\) emissions and resulted in transportation associated impacts as the dominant GWP source from PV EoL management in the US. In that scenario, disposal of the materials after recycling PV panels contributes ~32% of the c-Si PV's EoL GWP impacts. After PV materials from panels are recycled, some sludges including heavy metals, liquid wastes that could be considered as inert material, plastic materials that can be incinerated, and contaminated glass particles are generated. All these materials are sent to disposal sites at which they can be treated and/or incinated and stored. Sludges with a heavy metal content dominate the impacts from disposal (80%). The remaining ~20% is contributed from incineration of waste plastic materials from wires, cables, etc., used mainly in the balance of system component of PV panels. Furthermore, we found out that ~30% of the CO\({}_{2}\) emissions associated with the recycling scenario of c-Si PVs can be attributed to the recycling process, mainly from chemical treatment methods. The most impactful contributions to CO\({}_{2}\) emissions of the recycling process are from the material separation and extraction processes such as sieving, acid leaching, electrolysis, and neutralization [9]. The total CO\({}_{\text{2-eq}}\) emissions associated with EoL management of thin-film PVs were found to be higher compared to c-Si PV modules. It is mainly due to the higher amount of energy and material consumptions in the recycling process of these thin-film PVs during their EoL management. The recycling related impacts of CIGS are higher than CdTe because of the upstream emissions of the materials required for the recycling process (see the material content in Table 1). The main difference between thin-film recycling and c-Si PV recycling is the extraction of glass from PV panels. In the FRELP method, the glass component of PV modules is separated in the beginning of the recycling process, right after the balance of system (cables, frames, etc.) are taken out, and this separation process is handled by a mixed system involved infra-red heating and high-frequency knives [9].