## 2 Methods
### PV End of Life Management  
#### 2.2.1 Life Cycle Inventories  
Table 1 summarizes the life cycle inventories of EoL management of c-Si, CdTe, and CIGS PV modules. The EoL management of PV modules consists of transportation, recycling, and disposal phases. We selected trucks fueled by diesel to create a baseline scenario for the transportation of PV wastes. In addition, we modeled the transportation for trucks fueled by gasoline, trains fueled by diesel and by fossil-sourced electricity, and ships. The baseline scenario of the transportation involved 1000 km of travel distance which is the assumed total distance from the deployment location to the collection point and to the recycling center. \begin{table}
\begin{tabular}{l l l l l} \hline  & \multicolumn{1}{c}{**c-Si**} & \multicolumn{2}{c}{**CdTe**} & \multicolumn{2}{c}{**CIGS**} \\ \hline  & Process steps for c-Si: & & Process steps for CdTe: & Process steps for CIGS: \\  & (1) & Glass separation & (1) & Shredding & (1) & Crushing \\  & (2) & Glass refinement & (2) & Hammermill & (2) & Acid leaching \\  & (3) & Cutting & (3) & Material dissolution & (3) & Skimming and filtration \\  & (4) & Pyrolysis & (4) & Solid-liquid separation & (4) & Precipitation and filtration \\  & (5) & Sieving & (5) & EVA/Glass separation & (5) & pH adjustment \\  & (6) & Acid leaching & (6) & Precipitation & (6) & Indium extraction \\  & (7) & Filtration & (a) & Size reduction & (7) & Stripping \\  & (8) & Electrolysis & (b) & Pulping & (8) & Electrodeposition \\  & (9) & Neutralization & (c) & Leaching & (9) & pH adjustment \\  & (10) & Filter Press & (d) & Copper treatment & (10) & Gallium extraction \\
**Recycling Process** & & & & (e) & Tellurium reduction & (11) & Stripping \\  & & & & (f) & Cadmium precipitation & (12) & Electrodeposition \\ \hline \multicolumn{4}{l}{Material consumption per process step (c-Si):} & \multicolumn{2}{c}{Material consumption per process step (CdTe):} & \multicolumn{2}{c}{step (CdTe):} \\
66 96 s/HNO, water 2.40 kg & 43) s & 83 sulfuric acid & 42) H\({}_{2}\)S\({}_{0}\)(750 g) H\({}_{4}\)O\({}_{2}\) (3 g), \\
88 & 1.39 kg water & 84) S.4 kg deionized water & surfactant (23) g) \\
89 & 507 g water, 507 g g & Cd(OH)\({}_{2}\) & #5) 570 g hydrogen peroxide & 43) NaOH (330 g) \#40) S\({}_{0}\)(75 g) \\  & (50\% water) & & #6) DEPHTA (30 g), Toluene (120 g) \\  & & & #6) 100 g NaOH (50\% water) & & #7) HCl (750 g) (98) NaOH (105 g) \\  & & & & & \\  & & & & & \\  & & & & & \\ \hline \multicolumn{4}{l}{Energy consumption} & Energy consumption & Energy consumption \\ Processes: \#1, 2, 3 and 5 (c-Si) & Processes: \#1, 2, 4 (CdTe) & Processes: \#1 and 2 (ClGS) \\ Total electricity = 1.52 kWh & Total electricity = 4.4 kWh & Total electricity = 4.4 kWh & Total electricity = 4.4 kWh \\ \hline \end{tabular}
\end{table} 
Table 1: The comparison of the inventories for recycling of different photovoltaic (PV) modules (1 m\({}^{2}\) of PV panel). c-Si and CdTe recycling incorporate mechanical and chemical based methods while CIGS mostly involves chemical based methods. Transportation is consistent for the technologies, equal to 1000 km. In modeling the environmental impacts c-Si PV modules, we assumed the FRELP [9] method, which combines mechanical and chemical methods required to disseminate, separate, and extract materials from c-Si PVs. The material recovery rates of this method are as follow: 98% glass, 100% aluminum, 95% silicon absorber, 94% copper, and 94% silver [9]. In assessing the environmental impacts of thin-film CdTe PVs, we modeled the recycling procedure established and used by First Solar for frameless PV modules. Note that more recent First Solar CdTe modules are manufactured with a frame but an updated inventory for the frame removal is not available at this point. First Solar's industrial recycling technology also incorporates mechanical and acid-based chemical methods. The material recovery rates for the glass and semiconductor in the module are 90% and 95%, respectively [25; 40; 41; 42].