Wind turbine rotor blades are designed to be lightweight, strong and durable, but those same characteristics make them difficult to recycle at the end of their operating lives. As the first generations of wind turbines approach decommissioning, understanding what blades contain, and when those materials will enter the waste stream, is becoming increasingly important.
Lisa-Marie Brand and Niels Ludwig of Fraunhofer IWES argue that effective recycling requires both suitable recovery processes and reliable forecasts of future material volumes.
Understanding what is inside a blade
Rotor blades combine several materials, each selected for a particular structural purpose. These typically include:
The spar-web system carries much of the blade load, while sandwich structures combine low weight with resistance to buckling.
This mixture creates a recycling challenge because the materials cannot simply be processed together. They first need to be identified, separated and directed towards appropriate recovery routes.
Resin can be separated from fibres using processes such as pyrolysis or solvolysis. Glass fibres can potentially be returned to the material cycle by remelting, while PET foam can be broken down into its constituent parts. Separated balsa wood can also be processed for reuse, including as insulation material.
Carbon fibre requires different treatment because it cannot be remelted like glass fibre and its dust must be carefully controlled during shredding.
Identifying materials in older blades
Recycling becomes more difficult when dealing with turbines installed 20 or more years ago because detailed blade construction records may be unavailable.
Fraunhofer IWES is therefore investigating methods including thermography and near-infrared spectroscopy to identify the position and composition of materials before dismantling.
Thermography can help visualise boundaries between balsa, foam and spar caps without dismantling the blade first.
A planned pilot disassembly centre will explore how these incoming inspection techniques can be combined with subsequent material recovery.
Knowing when the material will arrive
Recycling technology alone is not enough. The industry also needs to know when blades will reach end of life (EoL) and what quantities of each material will require processing.
Fraunhofer IWES maintains a German wind turbine database originally developed through the RecycleWind 2.0 project. It includes a forecasting tool that estimates future blade masses and separates them into materials such as glass fibre, carbon fibre, resin and core materials.
Onshore forecasts indicate a substantial increase in annual EoL rotor blade masses over the coming years. Glass fibre represents the largest proportion, followed by resin and core materials.
Forecasting remains uncertain because actual turbine lifetimes vary. Around 20 years was historically assumed, but operational experience shows many turbines can operate for 25 years or longer with appropriate maintenance. Modern turbines are commonly designed for 25 to 30 years.
Repowering, maintenance and early decommissioning can all change when blades enter the recycling stream.
Offshore brings a different pattern
Germany’s offshore fleet creates another challenge. Because its first offshore turbines were installed in 2010, Fraunhofer IWES does not expect a significant increase in decommissioning before 2030.
The offshore forecast suggests material volumes could become concentrated in particular years rather than increasing steadily.
This reflects the way offshore sites may be reorganised. Smaller existing wind farms could continue operating for different periods before being replaced by larger consolidated developments linked to future 1,000 or 2,000 MW areas.
The DolWin example shows how existing layouts could be replaced by fewer, higher-capacity turbines within the same broad area.
Building recycling capacity before it is needed
Future decommissioning will involve more than blade recycling. Vessel availability, port capacity and the handling of nacelles, towers and foundations will also need consideration.
For rotor blades, however, the immediate priority is developing recovery routes and sufficient processing capacity before large volumes begin arriving.
Better information about blade composition can improve material separation. Better forecasting can help recyclers plan facilities and capacity. Together, these measures could help return valuable materials to productive use rather than creating a future disposal bottleneck.
As the first substantial volumes of onshore blades approach end of life, the circular economy challenge for wind is moving from a future concern to a practical industrial requirement.
For the complete Industrial Insight feature from Fraunhofer IWES on rotor blade materials, recycling processes and future end-of-life volumes, visit PES Wind: https://pes.eu.com/exclusive-articles/rotor-blade-recycling-the-hidden-challenge-facing-wind-energy