Modern wind turbines are behemoths, reaching well over twice the height of the Statue of Liberty. Recycling them when they reach the end of their lives is paramount if wind power is to be sustainable. Turbine blades however, are made of materials that cannot currently be recycled.
In a new study, chemists from Aarhus University in Denmark describe a way to break apart the strong glue that holds blades together, making their main building blocks available for reuse. This could keep millions of tons of blades out of landfills in the coming decades.
Wind power is picking up speed around the world. It is one of the fastest-growing energy sources in the world. Over 100 gigawatts of wind capacity is expected to be added each year of this decade.
Turbines are mostly made of steel, and about 90 percent of their structure can be recycled. That leaves the blades, each of which can be longer than a Boeing 747 wing, to contend with. Wind turbine blades need to be lightweight yet durable and ultra-strong. They are made of fiberglass, a composite material in which glass fibers or meshes are held together by an epoxy resin. These composites cannot simply be melted and repurposed like recyclable plastics.
Tens of thousands of wind turbines have already reached the ends of their lives. The blades of these decommissioned turbines end up in landfills. By 2050, about 43 million metric tons of turbine blades will be collected as waste.
Some researchers and companies are trying to make turbine blades recyclable. Last year, one company revealed a fully recyclable wind turbine blade based on a new resin that can be broken down to separate the glass fibers, giving both materials for reuse. A team at the University of Michigan reported a dissolvable resin that allows the recycling of turbine blades, but could also be combined with other materials to make things like countertops and gummy bears.
The latest work published in Nature does not require new resins. Alexander Ahrens, Troels Skrydstrup and colleagues at Aarhus have come up with a chemical technique that works on resins found in existing turbine blades. The process completely degrades the resin and frees glass fibers for reuse.
To break down turbine blade material, the team soaks chunks of the material in a mixture of the solvents isopropanol and toluene. Then they add a catalyst that speeds up the chemical reaction and heat the mixture. After a few days, what’s left behind is intact glass fibers and the chemical bisphenol A, which is the building block of the epoxy resin. The materials
“This is the first publication of a chemical process that can selectively disassemble an epoxy composite and isolate one of the most important building blocks of the epoxy polymer as well as the glass or carbon fibers without damaging the latter in the process,” Skrydstrup said in a press release.
Torkstrup’s group is a partner with Danish wind turbine maker Vestas, the Danish Technological Institute and materials manufacturer Olin on a consortium called the Circular Economy for Thermosets Epoxy Composites (CETEC), which supported this new research. Launched in 2017, CETEC aims to recycle blades that are currently sitting in or headed to landfills, and keep the industry from having to redesign blades for recyclability.
The researchers have filed a patent application for the process, and are now working on improving the method further. Right now, they use a catalyst made of ruthenium, a rare and expensive metal. The team wants to find an alternative that is more scalable and cost-effective.
Source: Ahrens, A., Bonde, A., Sun, H. et al. Catalytic disconnection of C–O bonds in epoxy resins and composites. Nature, 2023.
Image: Flickr Creative Commons
