RE SORT: Pyrolysis of thick-walled fiber composites as a key innovation in the recycling process for wind turbine rotor blades

At a glance

• To date, recycling processes for fiber-reinforced composites from rotor blades are yet to achieve genuine advanced recycling. Instead, the scrapped blades are thermally recycled in the cement industry. In light of the enormous quantity of rotor blades, better recycling processes are urgently required.
• In the RE SORT project, the project partners are investigating the potential of batch and microwave pyrolysis and developing a process allowing feasible advanced recycling of the fibers.
• Fraunhofer IWES is responsible in a subproject for the analysis and evaluation of the mechanical properties of the newly recovered fibers.

The challenge

Experts estimate that around 90,000 rotor blades from onshore and offshore wind turbines will need to be recycled in the next 20 years in Germany alone. These blades are made of fiber composites, which are relatively complicated to recycle due to the strong bond between various materials such as the resin and reinforcing fibers. As landfill disposal of fiber-reinforced plastic (FRP) waste has been banned in Europe since 2005, the majority of blades are now broken into small pieces, shredded, and thermally recycled in cement plants. The thick laminates in the blade root and in the spar caps pose particular issues, as they are almost impossible to shred. It is also not possible to recycle the carbon fibers produced in an energy-intensive process via this recycling method. At the same time, the thick laminate areas offer high potential for economically and ecologically sustainable recycling due to their large mass and valuable carbon fibers. 

The solution

The RE SORT joint project aims to develop pyrolysis technologies allowing the cost-efficient recycling of thick-walled fiber-reinforced composite structures. Two processes are being considered: the batch pyrolysis to be developed in the project, in which the matrix resin of thick fiber-reinforced composite components is broken down into oily and, above all, gaseous hydrocarbon compounds by heating, and microwave pyrolysis, in which the energy is supplied by the absorption of microwave radiation.

Fraunhofer IWES is responsible in the “Microwave pyrolysis, coating of recycled fibers, and FRP testing – MikroFaser” subproject for producing new FRP samples from the recovered fibers and then analyzing and evaluating their mechanical properties. 

The added value

The project should result in a recycling process for rotor blades that enables the preservation and reuse of the fibers in their entire length as well as the separation of pyrolysis gases and oils. It will then be possible to speak of genuine advanced recycling, which contributes to reducing costs and resource requirements in wind energy.