Rotor Blade Recycling
Materials | From balsa wood to wood foam
Recycling instead of incineration
In 2024, however, 15,000 rotor blades are to be taken out of operation in this country, and this number will multiply in the following years. A new strategy is therefore unavoidable, not least because large quantities of balsa wood are used in the high-tech composite components. For example, around 15 tonnes of the valuable light wood is contained in the blades, which are up to 90 metres long. Balsa wood has only about one third of the density of spruce wood, but is nevertheless very pressure-resistant and has a thermal conductivity of about 0.05 W/(m-K) perpendicular to the grain direction. This not only makes the lightweight material a favourite of model makers, it can also be used as an insulating material - as an alternative to rigid polystyrene foam, for example.
The Fraunhofer Institute for Wood Research (WKI) is working on a process that splits rotor blades by material - and separates the balsa wood. At first glance, the process looks brute: Directly on site, the rotor blades are cut into ten to twenty meter segments using a vehicle-mounted water jet lance. A mobile shredder breaks these up into palm-sized fragments, which are then sent to an impact mill. Set in rapid rotation, the fragments collide with metal elements, the hard, fibre-reinforced plastic breaks up and separates from the more elastic balsa wood.
Thermal insulation material for buildings
The balsa wood recovered in this way is processed by the WKI into lightweight wood fibre insulation mats. With a density of less than 20 kilograms per cubic meter, the material can be used for building insulation.
Another option: The balsa wood is finely ground and provided with a foaming additive. The resulting balsa foam requires no further binding additives and is also suitable as packaging material that can be disposed as waste paper .