Researchers in Italy have found that removing the backsheet from crystalline silicon PV modules before thermal recycling produces cleaner recovered materials and lowers particulate emissions, without reducing recovery yields.

The team tested a selective backsheet-removal step, patented by Italy’s National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) and Beta-Tech, upstream of the pilot-scale thermomechanical recycling process developed by Venice-based startup 9-Tech.

The scientists compared modules processed with and without their backsheets on material recovery, energy demand, the composition of recovered fractions and flue-gas emissions.

They said that removing the backsheet did not adversely affect recovery yields for the main materials. It also kept titanium dioxide, a white pigment used in PET-based backsheets, out of the recovered glass, silicon-rich, metallic and fine fractions. The researchers noted that titanium dioxide transferred into recycled fractions can reduce their quality, particularly in silicon recovery.

Particulate emissions fell from 69.0 mg/Nm³ to 44.1 mg/Nm³. The process also allows the polymer backsheet to be recovered separately rather than burned.

The scientists said that the trade-off was a roughly 20% increase in external propane demand, because the feed contained less combustible polymer once the backsheet was removed. Electricity consumption was unchanged.

The tested modules, Trina Solar TSM-230PC05 panels, had a non-fluorinated PET-based backsheet, so hydrogen fluoride stayed below detection limits in both configurations. The researchers said removing fluorinated backsheets before thermal treatment would be expected to prevent their contribution to hydrogen fluoride formation, but they did not test this.

The researchers said that 9-Tech’s process thermally removes organic components and then mechanically separates glass, copper ribbons and silicon-rich fractions.

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