We can start recycling wind turbine blades tomorrow: "There's nothing stopping us"
Currently, worn-out wind turbine blades are typically buried in landfills. In her PhD thesis, Kristine Wilhelm Lund from SDU has investigated whether recycling the blades is practically, logistically, and economically feasible. And it is.
If we are to recycle used wind turbine blades on a large scale, there are four technological options. Two of them still need further development, but the other two are well-established and can, in principle, be implemented immediately.
This is according to Kristine Wilhelm Lund, who has just defended her PhD project on the recycling of wind turbine blades at SDU's Engineering Operations Management.
- It may sound bold, but this is my conclusion, and I stand by it: there's nothing stopping us from doing something right now, says Kristine Wilhelm Lund.
Wind turbine blades in Denmark have an average lifespan of about 29 years, and currently, they are disposed of in landfills afterward. This is not a particularly sustainable solution, and in recent years, there have been more proposals on how to recycle the blades.
Until now, the focus has mostly been on individual technologies. Before Kristine Wilhelm Lund's PhD project, almost no one had examined the supply chains for the various methods and mapped out how it can be done practically, logistically, and economically.
- What I have looked into is everything that comes before and after the technologies. No matter which method you're dealing with, there are broadly eight main processes you need to go through, and I have mapped those out, says Kristine Wilhelm Lund.
- I have been focused on how we can design a functional industrial system that can be scaled up.
The four methods
Now, let's move on to the four methods of recycling wind turbine blades. Actually, there are five, because the ideal solution would be to reuse the blades more or less directly, for example, in bus shelters or furniture. But given the large number of blades to be decommissioned, this isn't realistic, says the researcher.
The most straightforward method is what's called cement co-processing. This is already being used in places like Germany, where the cut-up wind turbine blades are burned in cement production ovens, replacing other fuel sources. The leftover fiberglass is then used as filler in the cement.
- Burning something will never be a circular solution, but at least you're using the materials for something, and so it's a step above landfilling, says Kristine Wilhelm Lund.
Even better is if you can mechanically break down the blades in a large grinder and reuse the crushed material in, for example, building materials like plastic panels. This is the second technology, and it can also be implemented immediately, says the researcher.
- But in both cases, you could argue that you're just depositing the material in another product instead of in the ground. When the building materials or cement filled with fiberglass are eventually discarded, it will still require a recycling method for those as well, she says.
The two remaining methods avoid this issue and are therefore truly circular. However, they still require some work before they are fully ready for rollout.
One of these is pyrolysis, where materials are separated through heating in the absence of oxygen. The fiberglass can then be further processed and remelted for use in new wind turbine blades or other composite products.
The other method is solvolysis, where the principle is the same, but the glass fibers are chemically separated from the epoxy or polyester.
All solutions at once
According to Kristine Wilhelm Lund, as a society, we shouldn't choose just one method and stick with it. We should pursue all of them, she says, because the amount of decommissioned wind turbine blades will increase drastically in the next decade.
- One of the conclusions in my study is that we need to use all four routes, she says.
- We can't point to one single solution as the best because they are at different stages of development, and we need both the more established technologies and the ones still under development to handle the large amounts of waste effectively.
At the same time, the research shows that the many practical and logistical processes involved in the four different solutions are almost identical across the board.
- This shows that investment and standardization are prerequisites for all solutions.
Why are wind turbine blades so hard to recycle?
Wind turbine blades are typically made of composite material, which is a combined material. It often consists of glass fibers and liquid thermosetting plastic—either epoxy or polyester—which harden together into a mixed mass that is very difficult to separate again. Kristine Wilhelm Lund's PhD project is the first major study to focus on the supply chains around wind turbine blade recycling and how it is practically and logistically feasible. The project is part of the DecomBlades research project, supported by the Innovation Fund.
Meet the researcher
Kristine Wilhelm Lund is a PhD Fellow at the Institute for Technology and Innovation. She researches circularity and supply chain management and has previously worked in the wind energy industry.