Managing challenging waste fractions: Mechanical recycling of GFRP of wind turbine rotor blades and environmental assessment

The rising decommissioning of wind turbines generates significant quantities of end-of-life glass fiber reinforced plastic (GFRP) rotor blades. While mechanical recycling offers an energy-efficient disposal alternative, the resulting recyclate's suitability as a reinforcement in thermoplastic matrices remains underexplored. This study evaluates the use of mechanically recycled GFRP powder (rGFRP) from shredded and fractionated waste (0.063 mm, 0.045 mm, and <0.045 mm) as a filler in Polyamide 6 (PA6) via twin-screw compounding and injection molding. The mechanical performance of the rGFRP composites at 13 wt% and 23 wt% nominal loadings was compared against neat PA6 and virgin glass fiber composites through tensile testing, room-temperature (23 °C) Charpy impact testing, and scanning electron microscopy (SEM). The addition of rGFRP markedly increased the tensile modulus of PA6, reaching values of up to 4268 MPa. Most notably, the finest rGFRP fraction (< 0.045 mm) at 23 wt% yielded a mean room-temperature impact strength of 22.33 ± 3.02 kJ/m², which was comparable to or even higher than that of virgin glass-fiber references (19.64 ± 1.68 kJ/m²), despite the lower actual inorganic fiber content. This enhancement is hypothesized to result from the residual epoxy matrix adhering to the recycled glass fibers, which may improve mechanical interlocking with the PA6 matrix. Fiber length analysis of the ashed specimens confirmed that all recyclate fractions retain median fiber lengths (D50) between 44.5 and 89.9 μm after processing. A comparative life cycle assessment (LCA) indicates that the mechanical recycling approach can achieve net-negative environmental impacts when the reclaimed fibers substitute virgin glass fiber production. The results indicate that mechanically recycled wind turbine blades can effectively reinforce PA6, offering a promising circular economy approach for upcycling complex thermoset composite waste into valuable secondary materials.