Researchers have discovered how to use chemistry to recycle epoxy composites, such as those used in wind turbine blades and boat hulls. A researcher says that finding a recycling solution would prevent millions of tonnes of epoxy composites from being landfilled in the future.
Green energy is in, and wind turbines that can supply electricity to billions of people are being erected all over the world.
In the midst of the green transition, however, wind turbine manufacturers and owners face the problem that wind turbines cannot last forever, and after about 20–30 years, the blades must be removed and replaced.
The turbine blades are made from a material that cannot be recycled. The blades are therefore often landfilled or occasionally converted into playgrounds.
Researchers estimate that more than 40 million tonnes of decommissioned turbine blades must be scrapped by 2050, and since not all can be used to make playgrounds, they will be landfilled if the recycling challenge is not solved.
Luckily, researchers have nearly found a solution.
“Wind turbine blades comprise an epoxy composite, an enormously strong material that can withstand a lot and is very light. That is why it is used not only in wind turbines but also for cars, boats and aircrafts. But because epoxy composites are very durable, they are very difficult to recycle, and sustainable recycling technologies are almost nonexistent. This study presents a proof-of-concept on how to use chemistry to recycle epoxy composites so that wind turbine blades can enter the circular economy,” explains a researcher behind the study, Troels Skrydstrup, Professor at the Interdisciplinary Nanoscience Center and Department of Chemistry, Aarhus University.
The research has been published in Nature.
Ruthenium can deconstruct epoxy
An epoxy composite in a wind turbine blade combines glass fibres hardened with epoxy resins. Once these components are put together, they do not come apart again.
The researchers from Aarhus University collaborated with the Danish Technological Institute, Vestas and Olin Corporation, one of the world’s largest manufacturers of epoxy, to develop a method to deconstruct epoxy composites into their individual components.
The partners found that a catalyst based on ruthenium is very good at deconstructing epoxy under the right conditions based on Ru-TMM as the precatalyst and three equivalents of isopropanol in toluene at 160°C.
When a section of a turbine blade is placed in this solution with ruthenium present, the epoxy is deconstructed in just under a week, leaving the various components to be recycled.
“This protocol is the first to solve the major problem of how to recycle decommissioned wind turbine blades. It is basic science and an academic exercise, and we call it deconstructing a turbine blade in a test tube, but it is promising because it works,” says Troels Skrydstrup.
Wind turbine blades enter the circular economy
At the chemical level in the test tube, ruthenium cleaves a very specific bond between carbon and oxygen in epoxy while leaving the other components in the epoxy composite.
This means that the epoxy is deconstructed but the glass fibres are not, and the same applies to the metal matrixes often present in wind turbine blades as lightning conductors.
These components can be extracted from the mixture and recycled.
“This is one way of making the manufacturing of wind turbine blades part of the circular economy, where materials can be reused,” explains Troels Skrydstrup.
Ruthenium is too expensive
Although the researchers from Aarhus University have shown how epoxy composites can be deconstructed and wind turbine blades recycled in principle, Troels Skrydstrup doubts that the method will be used in its current form.
Ruthenium is not cheap, and the catalyst must therefore be replaced by something else before the method can be used. Deconstructing a small section of a wind turbine blade is one thing. Obtaining enough ruthenium to deconstruct a whole wind turbine blade or the blades from an entire wind farm is quite another.
“That is why we need to find or develop new catalysts that can replace ruthenium, and we do not know if this is even possible. In addition, we are chemists and not engineers. Scaling up the process and applying it in industry is a task for others,” says Troels Skrydstrup.
However, he also adds that deconstructing epoxy with ruthenium is not the only possible way to get rid of decommissioned wind turbine blades.
The researchers are also working on another project that does not require a catalyst, with epoxy composites being deconstructed by more common chemicals, which can do something similar to ruthenium but in two chemical steps.
“I cannot yet reveal anything about the second chemical process, but Vestas has so much faith in the idea that they have entered into an agreement with two companies to scale up the process to investigate whether it can become viable for the industry,” concludes Troels Skrydstrup.