In 2023, photovoltaic (PV) solar modules provided over 170 GW of green energy to the U.S. Currently, there is no mandatory recycling of PV waste in the U.S. and most PV modules are landfilled rather than recycled. Previous work on PV toxicity focused on metal and considered the full module. To plan for large volumes of PV waste that require management, we evaluated the potential ecotoxicity of various module components. The project was separated into two tasks: 1) acute toxicity of solar components under batch leaching conditions and 2) the design of a column landfill study. We tested three crystalline silicon modules by separating them into three components of waste: the powdered cell and glass area, encapsulation and back sheet polymers, and junction box and cables. Bioassays classified the aquatic acute ecotoxicity of each component with the half-maximal effective concentration (EC50) to crustacea, Daphnia magna, in which leachates were considered acutely toxic at concentrations of less than 10%.Two of the tested module’s powder and encapsulation and back sheet leachates showed little hazard to the environment with either no impact on daphnids or projected EC50s over 120%. The third module did have significant ecotoxicity with EC50s less than 5%. Each module’s junction box and cable leachates had observable effects on daphnids, but only one had a significant EC50 of less than 10%. The metal and microplastic content of each leachate was evaluated to characterize potential sources of toxicity. Of the 22 elements tested, few were of concern. Silver and aluminum leached at high concentrations exceeding literature EC50 values, so toxicity was primarily contributed to these metals. Spectroscopy analysis only showed a presence of plastics in junction box and cable leachates, with peaks characteristic of polypropylene and polyethylene. Therefore, only metals were of potential concern for powder, encapsulation, and back sheet components, while the junction box and cables may release small metal concentrations and some plastics. Overall, two modules showed little to no risk to the aquatic environment, but the significant toxicity of the third emphasized the need for careful classification and disposal of all module materials. This work verified previous claims that semiconductor metals were of primary concern in PV waste, allowing for proper classification of disposal needs. The ecotoxicity of select leachates showed the increasing need for PV recycling. Future work should expand on microplastic degradation in long-term studies for greater understanding of potential release.
Read
