Characterization of mechanically recovered photovoltaic encapsulants and backsheets as potential feedstocks for pyrolysis chemical recycling

Recovery and closed-loop recycling of materials from manufacturing or end-of-life photovoltaic modules is attracting increasing interest to access critical raw materials and limit waste and is supported by policies and funded innovation projects, in the European Union in particular. To complement circularity assessments of inorganic components from modules, this work focuses on mechanical separation of encapsulant and polymer backsheet layers for polymer recovery and initial analysis of the recovered materials to assess their suitability as feedstock for chemical recycling via a pyrolysis process, with the target of achieving closed-loop recycling of polymer materials within solar panels. Two polymer backsheet and three encapsulant samples mechanically separated from three modules or recovered from production scrap were studied for their chemical make-up, including content of oxygen heteroatom, and contamination levels from inorganic components. The samples contained 60 wt.% to 98 wt.% of polymers, which were identified to include polyethylene terephthalate, polyvinyl butyral, ethylene-vinyl acetate, and ethylene-rich polymers. The carbon content, which is a key parameter for the yield of a pyrolysis process, was estimated at 40–60 wt.% for the two backsheet samples, around 60 wt.% for the polyvinyl butyral and ethylene-vinyl acetate encapsulant sample, and around 80 wt.% for the ethylene-rich encapsulant samples. The inorganic content ranged from below 0.1 wt.% to 22 wt.% depending on the sample. These combined results demonstrate that polymer-rich fractions may be recovered from mechanical separation of modules and that only certain recovered polymer-rich materials have the potential to be used as feedstock for a pyrolysis recycling process, although further characterization under pyrolysis conditions remains necessary.