In June 2020, Siberia experienced abnormally high temperatures with a recordbreaking 38℃ in the Arctic Circle. Carbon dioxide (CO2) is well-known to be a major greenhouse gas (GHG) responsible for global warming. Among several CO2 emission sources, the contribution of the energy sector accounts for 58.8% of all GHG emissions worldwide. Recently, efforts were undertaken to encourage using renewable energy sources to minimize environmental impacts. Renewable energy sources such as solar energy, wind energy, biomass energy, and geothermal energy provide a promising opportunity for mitigating GHG emission and global warming as substitutes for fossil fuels and could supply 20%–40% of the primary energy demand in 2050.

Among those renewable energy sources, solar energy is the most abundant and accessible, in both direct and indirect pathways. By using photovoltaic (PV) cells, solar energy may be directly converted to electricity without emissions, noise, and vibration. In the last decade, the worldwide PV market has increased rapidly. At the end of 2017, the cumulative global installed PV capacity reached 397.4 GW. The typical lifespan of PV panels is 25–30 years, and PV panel waste would thus become a main environmental issue within the next few years. Countries with high cumulative installation capacity would encounter the largest burden of PV waste in ii the future. At the end of 2050, the cumulative global PV waste amounts could reach 60–78 million tons.

Life cycle assessment (LCA) is an effective tool for systematically evaluating the environmental impact of products and/or processes during their life cycle, including manufacturing, operation, and end-of-life (EoL) disposal. Although the environmental impact of PV systems focusing the production and operation phases has been extensively investigated over the past few years, limited studies have focused on the management of EoL PV panels.

Considering the dramatic increase in EoL PV panels as an emerging waste problem in the field of solid waste management, a proper PV waste management protocol has to be established to support a circular economy. Therefore, recovering materials from EoL PV panels is proposed as a primary strategy to reduce the negative environmental impacts, aiding sustainability. The EoL treatment process starts by transporting EoL panels to the recycling facility.

The LCA results of the EoL PV treatment without considering the avoided impacts related to the material recovery demonstrated that the environmental impacts of highlevel treatment were higher than those of low-level treatment because of higher environmental burdens associated with additional processes requiring chemicals, electricity, and thermal treatment. When considering environmental disburden associated with material recovery, the net environmental benefits from the high-level treatment were almost two times higher than those of low-level scenarios.

The main empirical findings derived from this study can be summarized as follows. The environmental impacts associated with the material recovery process were assessed for three leaching agents: HNO3, I2–KI, and thiourea, to choose the most environmentally friendly alternative. The LCA results for using thiourea showed that the environmental burdens during chemical treatment process were lower than those for the other two leaching agents. However, the net benefit considering material recovery was higher when using HNO3 as a leaching agent than that of the two other iii leaching methods, based on the level of endpoint analysis. Comparing the environmental impacts related to the transportation of PV wastes, the scenario that included transporting the wastes to the recycling facility via the collection center had 14.2% to 26.2% less adverse environmental impact than the scenario that involved directly transporting the wastes to the recycling facility. This reduction in adverse environmental impact was due mainly to weight reduction after pre-treatment and transport efficacy provided by a large-sized vehicle even though the traveling distance via the collection center increased.

When the secondary production of material was considered, some indicators could not exceed the environmental burdens of the recycling processes. Consequently, the findings associated with the treatment of EoL PV panels suggest that resource recovery and transportation should be considered to reduce the economic and environmental burdens.