## 2 Materials and Methods
### Process Descriptions and Inventory Data  
Figure 2 shows a process flow diagram for c-Si possible EoL scenarios and the description of each process. The process steps represented in Figure 2 are a compilation of the best results found by the authors and are explained in this session. Figure 2: Simplified process flow diagram for c-Si module manufacturing and possible EoL scenarios. ethylene vinyl acetate (EVA), ethylene-vinyl-acetate; Al, aluminium; Ag, silver; Si, silicon; ARC (anti-reflection coating). Life Cycle Inventories (LCI) are essential for LCA studies, and the availability of such data is frequently the greatest obstacle to conduct an LCA. However, since several authors published the environmental impacts from the production process of c-Si solar cells and modules, the inventory for these processes is well known. The International Energy Agency (IEA), through Task 12 of the Photovoltaic Power Systems Programme, published a report in 2015 containing a complete inventory for mono- and multi-crystalline silicon solar cells and modules production, including (limited) data for the BOS, as well as environmental impacts from these technologies [5]. As Figure 2 shows, the c-Si solar module production process starts with the raw materials (quartz sand), for which we included mining, processing and purification stages. The encapsulation materials (e.g., silica for glass) were also considered in this step. The cell production includes mono- or multi-crystalline silicon ingots sliced into wafers, p-n junction formation and application and firing of metallization pastes. In the module manufacturing stage, cells are connected physically and electrically and, after that, encapsulated by glass and plastics, which, together with the BOS components, create a PV system. The use phase includes the PV system installation, operation and maintenance. The BOS components and use phase impacts were not considered in this study. The BOS impacts calculated by other authors demonstrate that these materials have significant impacts [22; 23], but the inventory is still very limited. The use phase has not demonstrated significant impacts [35], so it can be neglected. When the modules reach their EoL, different pathways can be taken, as discussed above. The impacts from the landfill, incineration and reuse scenarios are not completely studied yet, but the Ecoinvent database [36] has a comprehensive database for plastic and some specific metals, shown in the Supplementary Material. For the recycling scenario, the considered processes were thermal [28; 29] and chemical [6; 20; 30; 31] methods, compared with the mechanical approach, which is already published [7] but excluding the transportation impacts from all processes. These recycling processes start with the mechanical separation of the junction box and aluminium frame, which can be recycled and reused. We did not consider the aluminium frame, the cables and the plastic parts in our recycling processes because they are normally sent to separate plants for further treatment [7]. The thermal process inventory is based on the controlled burning of EVA (400-500 \({}^{\circ}\)C), assuming the glass can be recovered without breaking and could be directly used again as the module component [28; 29]. In this process, it is expected that most of the cells end up breaking due to the excessive pressure from the gasses released during the burning process [28], but it can be reused as raw material for ingot growing (we assumed that 100% of the raw silicon is from this recycling process). There is also a 100% recovery of silver from the solar cells [28]. Tests with thermal treatment under air resulted in significant temperature increase and the carbonisation of the EVA. The absence of oxygen during this process avoids the oxidation of some materials, so a nitrogen atmosphere, which prevents chemical oxidation of the EVA layer [19; 37], was assumed. The chemical route assumed in this study starts with melting the EVA layer by a thermal process as already explained [28].