Aquatic toxicity of leachates from crystalline silicon photovoltaic components

Abstract

Previous ecotoxicological assessments of solar photovoltaic (PV) technologies vary considerably and focus solely on the active cell layer. A comprehensive evaluation of all possible sources of toxicity is required for proper disposal classification of waste materials. We evaluated the aquatic ecotoxicity of separated PV components from three crystalline silicon modules to crustacea, Daphnia magna. Modules were separated into three categories for testing: 1) powdered glass and cell, 2) encapsulation and back sheet polymers, and 3) junction box and cables. Batch leachates were used in bioassays and assessed for metal and microplastic leaching. The powder and polymers from two tested modules had little observed impact on daphnids, while the third showed significant toxicity with EC50s at 5% or less leachate. One junction box and cable mixture had significant toxicity with an EC50 of less than 10%. Upon metal analysis, Al and Ag leached in high concentrations upon metal analysis and were the primary suspects for ecotoxicological effects. Microplastics were not detected in powder or encapsulation and back sheet leachates, while there was evidence of hydrocarbon polymers in junction box and cable leachates. This work confirmed that metals in the active layer of solar modules are a primary source of concern, and potential microplastic leaching from junction boxes and cables should not be overlooked. Overall, the acute toxicity of silicon solar photovoltaics depends on the module type, components considered, and leachate exposure concentrations.