**2. Method**

#### *2.1. Data Collection*

There are several methods that have been proposed or are in use for the recycling of solar panels [21,22,25,26]. Of these, we followed the FRELP method, proposed by Latunussa et al., because, unlike other studies, FRELP was developed for industrial-scale recycling and all the details of life cycle inventories, including emissions from the facility and the efficiency of recycling, achieved yields data that were provided clearly, making the method easy to understand and utilize to expand for further cost analysis [20]. The FRELP method aims to test new methods and technologies with the goal of 100% recycling of PV panels in an economically responsible manner. Data on process costs and investment costs of the PV recycling process were developed using literature and industry data which can be found throughout the Supplementary Information tables (Tables S1 and S2).

The method of recycling we modeled by Latunussa et al., 2016, is acid leaching and electrolysis (Figure 1). In this process, after the PV panels are unloaded into the recycling facility, they are disassembled, the glass is separated and refined, and the PV sandwiches are cut and incinerated. The bottom ash from the incinerator is shipped to a different facility to be sent through several processes including sieving, acid leaching, filtration, electrolysis, neutralization, and a filter press. These processes for treating the bottom ash make up all the material inputs in the process cost of PV recycling and more than half of the electricity input. From these recycling steps, the recovery materials of aluminum scrap, silicon scrap, silver scrap, copper scrap, and glass scrap are recovered. Liquid wastes, sludge, hazardous fly ash, and contaminated glass produced during the entire recycling process (all waste boxes in Figure 1) are sent to landfills.

**Figure 1.** Simplified PV recycling process modeled from Latunussa et al., 2016 [20].

Figure 2 shows the costs and benefits considered in the analysis. The data were broken down into several different components: process costs, investment costs, environmental externality costs, recovered material costs, transportation costs, policy benefit costs, and landfilling tipping costs. The functional unit used in this work is 1 m<sup>2</sup> of PV. The private costs (defined as the market cost for a technology or production), external costs, and benefit costs are all broken down in terms of this unit.

**Figure 2.** Our framework in analyzing the cost of FRELP recycling method.

To quantify the different values shown in Figure 2, the below equations were used:

$$\text{Total cost of PV Recydding} = \sum \text{Private Cost} + \sum \text{External Cost} - \sum \text{Benefits} \tag{1}$$

$$\text{Private cost of PV recycling} = \text{PC}\_{\text{Inv}} + \text{PC}\_{\text{P,m}} + \text{PC}\_{\text{P,e}} + \text{PC}\_{\text{F}} + \text{PC}\_{\text{F}\text{e}} \tag{2}$$

$$\text{External cost of PV recyccling} = \text{E.C}\_{\text{P}} + \text{E.C}\_{\text{T}} + \text{E.C}\_{\text{L}} \tag{3}$$

$$\text{Berefits of PV recycling} = \text{B}\_{\text{R,e}} + \text{B}\_{\text{r,m.}} \tag{4}$$

In calculating the private cost (P.C) values, we consider all the private transactions that a PV recycler would have to pay during the end of life management of PV waste. For example, throughout the recycling process of PV waste (STEP I in Figure 2), the PV recycler must invest in purchasing the instruments (See Supplementary Information Table S2 required for operating the process (P.CInv) (see Table S2). In addition, the cost of materials (P.CM) (see Table S1) and electricity (P.CE) (Table S1) utilized in operating these instruments are considered. Similarly, during the transportation (STEP II in Figure 1) of PV waste (from installation location to recycling center and from recycling center to landfills), private cash flows are associated with the cost of fuel consumption of the trucks (P.CF) (Table S3) that carries the PV waste. Finally, during the landfilling of unrecovered materials (STEP III in Figure 1), a tipping fee is paid for dumping non-hazardous materials, P.CFee (Table S4).

The external cost in Equantion 1 refers to the cost of environmental damage resulting from the pollutants released during the end-of-life management of PVs, expressed as the dollar value. The external cost of the emissions from recycling process (E.CP) (Table S5), transportation (E.CT) (Table S6), and incineration during the landfilling (E.CL) (see Table S7) are considered in this analysis.

Equations (2)–(4) show all the components of our cost calculation framework. Note that we normalized all these values in terms of 1 m<sup>2</sup> c-Si PV module, since a unit surface area is the functional unit of this study.

Finally, the economic value of benefits of end-of-life management associated with the recycling and landfilling of PV waste were assessed. The private benefit value of recovered materials (BR,m e.g., from scrap metals) (Table S8) and energy (BR,e e.g., as electricity) (Table S7) are analyzed as positive private cash flows in the framework.
