Microwave-Assisted Thermochemical Recycling of Wind Turbine Blade Composite Waste: Experimental Pyrolysis and Solvolysis Assessment and Reclaimed Chemicals Characterization

Wind turbines are key for achieving global sustainability and carbon-neutral goals, but their end-of-life (EoL) poses significant recycling challenges relative to the complex materials used in their blades. The end-of-life disposal of fiber-reinforced polymer (FRP) wastes currently primarily involves landfilling or incineration, with recycling routes being limited due to high costs and inefficient processing technologies. This study evaluates microwave-assisted pyrolysis (MW-Pyr) and microwave-assisted subcritical solvolysis (MW-Solv) as chemical recycling strategies for end-of-life wind turbine blade (WTB) wastes composed of epoxy- and polyester-based glass and carbon fiber-reinforced polymers (FRPs). MW-Solv tests, performed with organic acid solvent (acetic acid) and a Lewis catalyst (ZnCl2 or AlCl3), achieved complete resin degradation at 250 °C in less than 2 h, with >95% fiber recovery and preservation of mechanical integrity. MW-Pyr reached nearly full resin conversion at 350–400 °C, typically producing 60–73 wt % pyrolysis oil. The oil fraction comprised 20–40 wt % monomeric phthalic derivatives from polyester resins and 70–95 wt % phenolic compounds from epoxy resins, significantly exceeding yields reported under conventional heating. Glass and carbon fibers recovered from MW-Pyr retained >90% of their original textural properties. Overall, MW-assisted processes enabled complete resin degradation (100%), high oil yields (60–73 wt %), and fiber retention efficiencies above 90%. These quantitative results highlight MW-Pyr and MW-Solv as effective routes for the circular valorization of FRP wastes from wind turbine blades, supporting their integration into polymer and chemical value chains.