Scientists Found a Clever Second Life for Dead Wind Turbine Blades

Durability is key to wind turbine engineering. The giant blades are highly exposed to the elements and need to withstand everything nature throws at them for decades, but when they reach the end of their operational lifespan, that durability becomes a problem. Tossing the blades into landfills takes up huge amounts of space and wastes materials that could be useful if extracted and given new life. The thing is, wind turbine blades are so durable that breaking them down and recycling them presents significant challenges. In a study published today in the Cell Press journal Chem Circularity, researchers present a new approach that could overcome those challenges. By rapidly heating turbine blade waste using brief bursts of energy, the authors broke it down into silicon carbide and graphene, two valuable manufacturing materials that can be used to improve the mechanical and thermal properties of new blades. And compared to current recycling techniques such as chemical dissolution and heat recovery, this new approach cuts greenhouse gas emissions by 92% and 83%, respectively. “It can be used to upcycle low-value waste into high-value waste,” lead author Hao Bi, an environmental engineer at Tsinghua University in Beijing, told Gizmodo. Blades keep on turning Wind turbine blades are usually made of fiberglass, which contains silica, and a carbon-rich polymer resin. When these materials reach super-hot temperatures, carbon can react with silica to form silicon carbide, an extremely hard, heat-resistant compound. Carbon atoms can also reorganize into a flat, honeycomb-like lattice called graphene, coveted for its strength and ability to conduct heat and electricity. To extract these materials from turbine blade waste, Bi and his colleagues used a technique called flash Joule heating. He explained it as a “high-current electrical pulse applied to conductive raw materials to raise their temperature to 2,000 degrees Celsius [3,632 degrees Fahrenheit] or even higher in milliseconds.” Flash Joule heating has already been used to convert plastic wastes and biomass wastes into graphene and other nanostructured carbons, and it proved successful at extracting useful materials from turbine blade waste too. The researchers first created a mixture of pulverized blade waste and nearly pure elemental carbon, then subjected the mixture to flash Joule heating across several experiments. A typical experiment converted about 56% of the mixture into a silicon carbide and graphene composite made up of 34% silicon carbide and 66% graphene. Adding a small amount of these products—just 0.3% by weight—to resin made it stiffer and stronger, improving its resistance to deformation by 27% under tension and 9% when bent. At 0.1% by weight, the resin’s thermal diffusivity—a measure of how quickly heat disperses throughout a material—increased by 41%. Thus, silicon carbide and graphene extracted from retired wind turbine blades could be used to make new blades even more durable, but scaling this process presents a whole new challenge. Next step: scaling Bi and his colleagues were only able to test tiny batches of the blade waste and carbon mixture. The largest was just 10 grams—well below a practically relevant processing scale. His team has already designed and built a larger-scale reactor to process a 200-gram batch, but it still requires some optimization. In particular, Bi highlighted a need to make sure that this new reactor can heat the material uniformly and produce consistent product quality. “I would describe this work as a promising proof of concept with initial scale-up results, but it is difficult to predict when it could serve a real wind farm,” he said. At a commercial scale, the researchers estimate that their blade recycling approach could turn a profit of about $80 per ton of blade material, due to the high value of the recovered silicon carbide and graphene. Conventional recycling methods require wind farm operators to pay for waste processing. Pyrolysis costs roughly $460 per ton, while chemical dissolution costs about $1,800 per ton, according to Bi. This would help incentivize a closed-loop turbine blade manufacturing system, making this critical renewable energy source more sustainable. But again, the path to scaling remains long.