Cascading composites

Can cascading extend the material lifetime of large composite products, for example wind turbine blades?

Wind turbines are designed for a service life of 20 to 25 years after which they are decommissioned. At end of life wind turbines can be largely recycled. However, the blades,  which are typically made of a complicated laminated structure of glass fiber reinforced plastics (GFRP), are usually land-filled or incinerated. For a typical wind turbine this adds up to 12 tons of waste material. Considering market growth, annual decommissioning of wind turbine blades in Europe is expected to reach 50,000 tons by 2022. From the perspective of a circular economy and the EU waste directive, both landfilling and incineration are undesired, as the product value and functionality are lost.

Opportunities for recovery of wind turbine blades or their materials can be seen at different levels, ranging from reuse of the blade as such to recycling of the blade materials by repurposing large elements, using blade segments (through smart partitioning) or blade fragments (obtained by shredding).

Schematic representation of a wind turbine blade’s value in successive lifecycles (Joustra, 2019).

This resembles a cascading system, as found in the Circular Economy diagram. Which has potential to prolong the life of the composite material. However, little is known about reuse, repurposing or structural recycling of composite products. Through design studies where blades or parts thereof are reused, factors are found that hamper recovery. These provide valuable insights into how new wind turbine blades could be designed to facilitate recovery.