The recyclability of wind turbine blades has in recent years become a sticking point in discussions about the sustainability of the industry. Today, between 85% to 95% of a wind turbine is recyclable, according to Ørsted, because they are made mostly out of steel, which is easily recycled.

However, recycling wind turbine blades in particular has remained a challenge because of the type of ultra-strong resin used inside them. For decades it was thought that thermoset epoxy resin, the type often used inside turbine blades to make them both lightweight and durable, is impossible to break down into reusable materials. As a result, blades have traditionally been dumped and left in landfill sites as a method of disposal.

As wind farms expand globally in size and number in line with the energy transition, turbines are being decommissioned at higher and higher rates when they reach the end of their serviceable lives. This has meant that blades are burdening landfill at an increasing rate. Bloomberg reported in 2020 that in the US and Europe combined, nearly 12,000 turbines will come down annually until 2024, with most having nowhere to go but landfill.

“The wind turbine blade will be there, ultimately, forever… most landfills are considered a dry tomb,” said Bob Cappadona, chief operating officer for the North American unit of environmental services company Veolia Environment SA.

Here lays, literally, the contradiction of the wind turbine as a producer of renewable energy; while wind as a source of electricity generation is itself entirely renewable, the turbine used to produce electricity has historically not been part of a sustainable cycle. Recent innovations in the sector, however, seek to change that.

Reinventing resins for wind turbine recycling

In the last few years, several companies and research centres have been developing new types of resin that can be easily and readily recycled.

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Speciality materials manufacturer Arkema launched project ZEBRA (Zero wastE Blade ReseArch) in September 2020, with the aim to create a fully recyclable wind turbine blade using alternative thermoplastic resin. In March last year, the company announced the completion of its first entirely recyclable prototype wind turbine blade.

Measuring 62m in length, the blade is made from Arkema’s own thermoplastic resin that promises to deliver similar performances in strength and damage resistance as epoxy resin, with the added benefit of recyclability.

Researchers at Michigan State University in the US have developed a different composite resin that has the potential to be recycled into an array of materials and items at the end of a turbine’s blade life. It is made by combining glass fibres with a plant-derived polymer as well as a synthetic one. Researchers found that prototype resin panels made from the new composite material were both strong and durable enough to be used in turbines or vehicles and were fully dissolvable in a fresh monomer.

“The beauty of our resin system is that at the end of its use cycle, we can dissolve it, and that releases it from whatever matrix it’s in so that it can be used over and over again in an infinite loop,” said John Dorgan, chair in chemical engineering at the university. “That’s the goal of the circular economy.”

As well as being recycled into new wind turbine blades, the broken-down resin could also be combined with other minerals to make a variety of different products.

“We’ve recently made a bathroom sink with the cultured stone, so we know it works,” says Dorgan, adding that “we recovered food-grade potassium lactate and used it to make gummy bear candies, which I ate.”

What these attempts at resin and blade redesign have in common is their shared goal: to make wind turbine blades 100% recyclable in a way that creates a genuinely circular economy. Until recently, this route seemed like the only viable approach to turbine circularity.

A new solution to an old problem

Taking an entirely different approach, wind turbine manufacturer Vestas announced in February the completion of a new solution to end the landfill disposal of turbine blades that does notrequire resin redesign. The company, along with Aarhus University, the Danish Technological Institute and materials manufacturer Olin, has spearheaded the development of a new chemical process that allows for the complete break-down of thermoset epoxy resins.

Vestas’ wind turbines off the coast of Denmark. (Photo by Vestas)

Through a joint initiative called the Circular Economy for Thermosets Epoxy Composites (CETEC) project, a new chemical solution has been developed and successfully tested, allowing traditional turbine blades to be broken down into virgin-grade materials and reused, rendering epoxy-based blades as circular.

Andreas Sommerfeldt, materials specialist and lead technician on the project at the Danish Technological Institute explains that the project has been running  since 2017, and set out initially with the same goal as those other companies – to create a new type of resin that was designed specifically with recyclability in mind – but that challenges remain .

 “It is always difficult to predict how fast things will mature. There are still some limitations that we’re trying to figure out to make it [scalable]”, says Sommerfeldt. “How much [material] can you recover? How does this lifecycle look throughout our recycling process? If it’s relevant or not, that’s really difficult to say from an experiment. You need to have some sort of real life [scenario].

“But the first stepping stone is that there is now a partner that is willing to take on this challenge,” he ads. Before, there was only Vestas and Odin, but now “there is actually someone who is responsible for handling waste.”

The technology “would also be an economic solution for the waste handler; it’s also business” notes Søren Haack, project lead at the Danish Technological Institute. “There’s a lot that needs to be optimised before it is a really well upscaled industrial case that also makes sense businesswise … It’s a far way to carrying materials around in the lab to driving around globally.”

“We need to look back, and we need to look forward”

Yet the question remains: what does this new chemical process mean for the future of wind turbine recycling? A significant amount of time, money and resources have already been put into researching and developing alternative composite resins for turbine blades. Once CETEC’s new technology is ready for commercialisation and old turbines are turned recyclable, might these new developments be rendered obsolete?

“I think it’s always nice that you have competitive or parallel supporting solutions for recyclability. One solution might fit one case, and another might fit another case”, Haack explains, adding that if a material is “designed forrecyclability, that’s of course the most elegant solution”.

“From a material specialist perspective, I think what it will come down to is that this [epoxy] is a very, very robust material. It’s always been designed towards doing some of the more extreme things that a material should be able to do, which always makes recycling difficult”, Sommerfeldt says. “In comparison, those things [alternative resins] they are making now, it’s a very elegant solution, to make a design for recycling.”

He used an analogy comparing the chemical process used to break down epoxy resin to a hammer, explaining that the more robust a material is, the bigger the hammer needs to be, and the harder it needs to be hit. “So in all cases, once you design for recycling, you also make life easier on yourself in the end. So that you don’t need so specialised [a solution] or so big a hammer”.

In other words, “we need to look back, and we need to look forward”, says Haack. “I think we will also see a ban for landfilling decommissioned blades, not 25 years from now, in the very near future”, he added, making the requirement for an immediate solution to current blade recyclability a potential legal issue as well as an economic and environmental one.

But for everything it solves now, as Haack and Sommerfeldt explain, it might be best, for future ease, to continue to design and commercialise blades made with recyclability in mind from the outset. “Of course, we still need to design for future products, and how to achieve circularity with those products”, Haack concludes.