A patented process uses recycled balsa wood from disused wind turbine blades to create a lightweight wood foam that mimics the polystyrene found in the core of surfboards and paddle boards. First, the wood is separated from the glass-fibre reinforced plastic (GFRP) outer shell of the rotor blade in an impact mill, with a wind sifter then used to split out the wood fragments from the composite material.
“We need this very fine starting material to produce wood foam,” said research lead Christoph Pöhler, a civil engineer from Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut (WKI).
“In standard boards, a polystyrene core, which we know as styrofoam, is reinforced with fibreglass and sealed with an epoxy resin. We, instead, use bio-based lightweight material.”
The finely ground wood is processed into a batter-like mix which is then converted to foam, without the need for any additional adhesives. According to the researchers, the density and strength of the foam can also be tuned, which is vital to create boards that both float and are light enough to carry.
The biomaterial is being used to create a stand up paddle (SUP) board as part of a project known as ecoSUP. Pöhler, an avid paddler himself, was inspired by the growing problem of plastic pollution in the oceans as well as the issue of recovered balsa wood being burnt instead of reused as a structural material in some countries.
“This was exactly our thinking,” he said. “The valuable wood is too good to burn.”
For the outer shell of the board, the team will use a bio-based polymer that is reinforced with flax fibres, instead of the GFRP that is widely used to cover both paddle boards and rotor blades.
“In the interests of environmental protection and resource conservation, we want to use natural fibres and bio-based polymers wherever it is technically possible,” said Pöhler. “In many places, GFRP is used even though a bio-based counterpart could do the same.”