What happens to old wind turbines once they’re decommissioned? This question has presented a major headache for the industry. There are 30,000 operational wind power generators in Germany and many of them are approaching end-of-life. Last year alone, 2,000 rotor blades had to be disposed of; by 2024 this figure will have leapt to 15,000, with a further estimated 72,000 defunct blades up to 2027, according to a study by the Fraunhofer Institute for Chemical Technology.
While the steel and concrete elements of the giant turbines can be recycled in an eco-friendly way, the rotor blades are problematic because the composite material is almost impossible to separate into its constituent parts. Thanks to researchers from the Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut (WKI), however, a solution has been found.
Peter Meinlschmidt, the project manager at WKI in Braunschweig, explained in a : “[The blades] are mostly made of glass fibre reinforced plastic and balsa wood, bonded with epoxy or polyester resin.” Each blade contains around 15 cubic meters of balsa wood, which is ultra-light and extremely pressure-resistant, but the powerful glue makes it impossible to recover the wood, which ends up being burned as industrial fuel.
First his team reviewed how the blades are dismantled: instead of cutting them up on site, they tried separation using a water jet lance, which proved to be “much faster and better”. The shards (which are still 10 to 20 meters long) were then put into a mobile crusher and broken into pieces bowling ball sized pieces. Using an impact mill, the pieces were then further reduced into their individual components. "The composite material then breaks apart because the wood is viscoplastic, while glass fibre and resin are very hard,” .
The reclaimed balsa wood can then be processed into ultra-light, insulating mats for buildings, amongst other things, or mixed with a foaming agent to produce a new kind of “elastic foam wood”, which is eco-friendly, and could either be used for insulation or for packaging.