Keeping the carbon in the loop: A new circular solution for wind turbine blades

Allan Korsgaard Poulsen is the Head of Advanced Structures and Sustainability at Vestas Innovation and Concepts where he leads a diverse team of engineers, material scientists, physicists and mechatronics specialists. With a workshop to make full scale prototypes, they have capability to develop technologies and design and construct wind turbines from scratch. This makes Poulsen uniquely positioned to consider the full circularity of a wind turbine, considering sustainability implications from the start of design to the end of life. He is also a co-author of the Vestas Sustainability Strategy.

Sustainable design
“When you start to look into sustainability in design, a big part of it is to carve out materials that are in excess, to reduce the mass,” says Poulsen. ”That’s the first step to sustainability. We have the option not to select materials that are tough to recycle, but it’s difficult to look into more sustainable materials, for example new materials with recycled content, from the start, because there are not many circular solutions on the market yet.” A challenge is that new materials will not be industrially relevant until they are available at scale, tens or hundreds of thousands of tonnes. Vestas uses many tonnes a day of polymers and coatings, so keeping those carbon atoms in the loop is a priority.

What are the recent activities Vestas has been involved in to improve circularity of wind turbine blades?
In the CETEC project Vestas, together with the Danish Technological Institute, Aarhus University and Olin Epoxy, has figured out a way to dissolve epoxy infused blades at end of life. “It’s a two step process,” Poulsen explains, “First the blades are disassembled, the different materials in the blade are separated. Then we can convert the epoxy back to the basic chemical constituents that can be used in the polymerization reaction for epoxy once again.”

For the disassembly, the process uses commoditised chemicals which are not harmful, and works at ambient temperature and pressure, making it as cheap as possible. Having separated out the fibres, the dissolved epoxy is converted to useful chemicals at Olin Epoxy’s chemical facility. The process has been designed for low cost and easy handling.        

“We don’t let any of the carbon escape as carbon dioxide. It’s kept in the loop and we can use it in the polymerization reaction again, and since it’s the basic molecules, we don’t lose any chemical or physical properties.” Poulsen continues, “The fibres have some micro damage, but we are not using elevated temperatures so we are not reducing the strength to the same extent as you do in processes like, for instance, pyrolysis.”

Which are the most important regulations and standards driving recycling? Are there ways they need to change?
Poulsen believes the main blocker is that you are still allowed to put these epoxy components in landfill, “It’s still so cheap, so we cannot get the scale. Landfill is still the first choice for companies that do not have sustainability that high on the agenda. It’s still much better to use a blade in a cement kiln than it is to put it in landfill. Then you get some value out of the materials, you substitute sand with the glass fibre and you substitute some of the fuel with the resin.”

Another challenge Poulsen mentions is segregation of waste, which would benefit all the composite recycling technologies. “It is the volume that’s going to drive this recycling industry – it needs a reliable supply chain.” This supports the comments from Volker Mathes at AVK in relation to the need for a composite waste code. (See article).

The wind industry in Europe has committed to a landfill ban from 2025, so they will recycle the blades one way or another. Poulsen adds, “ It would be great if there is legislation and the other industries (producing composites) do the same, because that would drive up masses and provide a reliable supply chain.”

Scaling up
The CETEC process has been tested on several epoxy systems and they know it works. It does not depend on using a special hardener or other resin constituents; it can start on epoxy composite waste that exists today, including waste from other sectors. Stena Recycling has been invited to collaborate with Vestas and Olin Epoxy for the next phase to industrialise the process.

This new solution and the commitment of the wind industry to a landfill ban provide hope for a more circular solution for wind turbine blades in the years to come.

More information:
Vestas unveils circularity solution to end landfill for turbine blades, Vestas, 8/2/2023
Wind industry calls for Europe-wide ban on landfilling turbine blades, WindEurope 16/6/2021
The CETEC project is partly financed by the Innovation Fund Denmark.