“Currently around 10% of building insulation materials are made from renewable resources – there’s room for improvement here.”
Researchers from Germany-based Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut, WKI, have used a new recycling technique to recover and process balsa wood contained in wind turbine rotor blades to turn them into products like insulation mats for buildings.
Old wind power generators have to be disposed of – whether due to material fatigue or simply because they are being replaced by larger and more efficient systems.
A study by the Fraunhofer Institute for Chemical Technology ICT predicts that around 15,000 rotor blades will have to be discarded in 2024 and around another 72,000 more in 2027.
According to Fraunhofer (@fraunhofer), there are traditional methods for disposing of the steel and concrete in wind power generators, but recycling the rotor blades remains problematic because they are not made of steel but largely made of glass-fibre-reinforced plastic and balsa wood bonded with epoxy or polyester resin. They are made from balsa wood because it tends to be a lightweight material.
Fraunhofer ICT colleagues and industry partners have developed a new recycling technology to recycle this balsa wood. To recover and recycle the balsa from the rotor blades, the detached blades are disassembled on the spot, Fraunhofer said in a statement.
“The conventional approach is to use a band saw to cut the rotor blades into thirds or quarters, but this is a relatively complex process. That’s why we came up with the idea to try it with a water jet lance instead. And what do you know: it was much faster and better,” said Peter Meinlschmidt, project manager at the Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut, WKI in Braunschweig. The lance can be mounted on a special vehicle and controlled from there.
“The tremendous thrust would make it extremely difficult to guide the lance by hand,” Meinlschmidt added. Then, while still on site, the 10- to 20-meter-long rotor blade segments are fed into a mobile shredder that breaks them into pieces about the size of the palm of a hand.
Finally, the research team uses an impact mill to separate these pieces into their individual components. To this end, they are set in rotation and hurled against metal at high speed.
Meinlschmidt explained: “The composite material then breaks apart because the wood is viscoplastic, while glass fibres and resin are very hard.”
At Fraunhofer WKI, the balsa pieces are processed to make, for instance, ultra-light-weight wood-fiber insulation mats. “Currently around 10% of building insulation materials are made from renewable resources – there’s room for improvement here.”
According to Fraunhofer, with a density of less than 20 kilograms per cubic meter, these mats provide insulation like common polystyrene-based materials.
In conclusion, Fraunhofer said the recycled balsa wood can also be used to produce elastic wood foam and insulating material.
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