How chemists could give new life to old wind turbine blades
Wind turbines are crucial for addressing climate change, but when they've reached the end of their lives, turbine blades could add up to a lot of waste. Now new research, published in Nature, could represent a first step toward building renewable-energy infrastructure that doesn't end up in a landfill.
Wind turbine blades need to be tough to be useful. These workhorses of renewable energy last for decades, frequently spinning around up to 30 times each minute.
But when it's time to decommission one, a wind turbine's strength can become a weakness. Because the blades are designed to be so durable, the materials used to build them can't currently be recycled. And about 43 million tons of these blades will be decommissioned by 2050.
The new work describes a way to recover the main components of wind turbine blades, breaking down the plastic that holds them together without destroying the material's primary building blocks.
We need sustainable energy, but we also have to consider the waste, and we have to find solutions for that," says Alexander Ahrens, a postdoctoral researcher at Aarhus University in Denmark and the lead author of the new study.
Wind turbine blades are made with strong plastic called epoxy resin. Because of the chemical bonds created when epoxy resin solidifies, it can't be melted and squished into a new shape to be reused, like the plastic that makes up water bottles or milk jugs. In this case, fibers are also mixed into the resin for extra strength. This kind of reinforced material-called fiberglass when the supporting fibers are made using glass-is often used for high-intensity applications like airplane wings and boats.
Because these materials are so durable, there's not really right now a technology that is fit for recycling them," Ahrens says.
Some methods do exist for breaking down fiberglass, but these approaches usually render the epoxy portion unusable and often damage the glass fibers as well. The researchers at Aarhus set out to develop a method gentle enough to let the main components be used again.
The resulting approach takes aim at chemical bonds that lock the plastic into place and chews them up like Pac-Man-just chews up the epoxy and liberates those glass fibers," says Troels Skrydstrup, a professor of chemistry at Aarhus and another author of the new study.
To break down the epoxy materials, researchers submerged them in a mixture of solvents and added a catalyst, which helped accelerate the chemical reaction. They heated everything up to 160 C (320 F) for between 16 hours and several days, until the target material was fully broken down.
After some initial tests, the researchers used their method to chew up a one-inch-square chunk of a wind turbine blade. After six days, the result was nearly spotless glass fibers (and a supporting metal sheet that runs through most turbine blades) and vials of ingredients that could be used again in new materials.
This is the first time that researchers have been able to break down a reinforced epoxy material to recover both the plastic's building blocks and the glass fibers inside without damaging either, Skrydstrup says.
While this process was able to chew up materials in the lab, it could be difficult to pull off at large enough scale to make a dent in the millions of tons of wind turbines coming out of service in the next few decades. I think what's important is that it shows a proof of concept that may inspire others to start looking in this direction," Skrydstrup says.
Proof-of-concept research is key in chemical recycling, and this approach is really exciting," especially because the researchers demonstrated that it works on real waste, says Julie Rorrer, a professor at the University of Washington who studies chemical recycling.
The next stage, Rorrer says, would be figuring out how this could work on an industrial scale, or determining what would need to be adjusted so the process could be quick and efficient enough to be economical.
One of the possible roadblocks to commercial operation is that the catalyst used in the researchers' recycling method relies on an expensive metal called ruthenium. The researchers were using a lot of this metal, and though it doesn't get used up during the reaction, it could be difficult to recover and use again.
There may be other methods better suited to recycling turbine blades in industry. Skrydstrup's lab has developed another process that also breaks down turbine blades, which was referenced in a press release earlier this year by the wind turbine maker Vestas.
Skrydstrup says that approach is a two-part process and might be more feasible to run at commercial scale, though the researchers declined to give specific details because they're working to submit the results to scientific journals.
These are just two of the many approaches being developed in advanced recycling. There's been a huge boom in research on ways to clean up all sorts of materials, from single-use plastics to wind turbines, Rorrer says, and for good reason: There's valuable things in trash."