Windmill recycling: What happens to blades, steel and concrete 

Wind turbine recycling refers to the dismantling and recycling of all components of a wind turbine at the end of its service life: from highly recyclable concrete and steel to hard-to-recycle composite blades.

Wind energy is the backbone of the German energy transition. But what actually happens to wind turbines when they reach the end of their service life? Many wind turbines have also reached the end of their service life in Germany in the coming years. This raises important questions for the wind energy industry: How can materials such as concrete, steel and, above all, the problematic rotor blades be recycled sustainably? Which standards should be applied? And how can the individual components be usefully reused? For asset managers investing in renewable energies, this is not an abstract question of the future. Instead, it is a topic that already influences the value of portfolios today.

There are no binding standards yet, but innovative solutions are developing on the market that revolutionise recycling and further exploit the potential of wind power.

How many wind turbines are being dismantled?

With around 28,800 wind turbines, wind energy in Germany now accounts for more than a quarter of total electricity generation - a trend that is increasing.⁴ This is also because wind turbines are becoming ever larger and more efficient and can thus produce more electricity: In 2024, the average generator output of newly installed plants exceeded the five-megawatt threshold for the first time - an increase of around 7 percent compared to the previous year. At the same time, the average size of the wind turbine blades, i.e. the so-called rotor blades, has continued to increase over the same period.⁴

But as the number of modern wind turbines increases, so does the need for sustainable solutions for dismantling old wind turbines. After all: Wind turbines have an estimated service life of 20 to 30 years, after which they must be dismantled again by the respective operator and replaced with new turbines if necessary.

In Germany, around half of the wind turbines are now over 15 years old; about a third of these older turbines have even been in operation for more than 20 years.¹ Germany is therefore facing a major dismantling wave in the coming years, which brings its own challenges.
 

Repowering: Why modern wind turbines are getting bigger and bigger 

Modern wind turbines are becoming ever larger in the course of so-called repowering: Older wind turbines will be replaced after their service life by more powerful models with significantly larger dimensions. While the average rotor diameter of new onshore turbines in Germany was still 95 metres in 2012, it has grown to 146 metres by 2024.⁵ Hub heights also increased over the same period, reaching an average of 143 metres in 2024.⁵

Today, this quickly results in a total height (hub height plus rotor radius) of around 220 metres in assembled condition. Some projects go even further: A wind turbine development company in Lusatia is planning a wind turbine with a hub height of 300 metres and rotor blades that are over 100 metres long - a globally unique project that aims to reach new heights in the wind power industry.⁶

The background to this growth dynamic: While older turbines often only produced 1 to 2 MW of power, modern wind turbines generate up to 7 MW - a multiple of the previous value.⁷ This is how many wind farms are to be significantly reduced in size while increasing their overall output. This development improves energy yield, but also increases material requirements and makes dismantling more difficult once the wind turbine has exceeded its service life.
 

What can be recycled on a wind turbine and what can't?

If a wind turbine needs to be dismantled, there is above all a question: What happens to the old windmill? This issue is currently playing a major role, as more and more wind turbines will soon reach the end of their subsidised service life.

Most of this question is quite easy to answer: about 90 percent¹to be precise. This is the proportion of materials in a wind turbine that can be easily recycled and reused, whether for further wind power projects or in other industries. These 90 percent are primarily wind turbine towers: It consists primarily of a concrete base fitted with a steel cap. Both materials can be easily recycled, for example, the concrete is often used in split, i.e. crumbled form for road construction. And if the mild steel does not show any signs of wear or rust, it can also be used for further construction projects without problems.

It only becomes a real problem for the remaining around 10 percent of the entire wind turbine: the rotor blades. They consist of a complex material mix of balsa wood and plastics, which are reinforced with glass or carbon fibres. These materials ensure stability and weather resistance during operation, so that the blades can withstand all weather conditions even at speeds of up to 400 km/h.

The stability this material mix brings ultimately creates difficulties in the recycling process: For recycling the rotor blades, the glass and carbon fibres would have to be separated from the plastic again. So far, however, there are only a few and very elaborate and expensive methods for this. For many operators, such procedures are therefore often not the first choice.

This is why the recycling problem has often been ignored so far: Dismantled blades in some cases remained unused on fields for years.⁸ In many other cases, the glass fibre-reinforced rotor blades in particular are often used as replacement fuel or deposited abroad. Solutions with which Peter Kurth, President of the BDE Waste Management Association, is not at all satisfied. He considers these forms of recycling an annoying waste of resources: “The recyclables have to be returned to the cycle instead of simply burning them,” says Kurth.²

An overview study by the German Federal Environment Agency forecasts a rotor blade waste volume of up to 50,000 tonnes per year for the 2030s.⁹ Accordingly, the rotor blades of wind turbines generate a large amount of waste, which should not actually be any.

Organisations such as the Waste Management Association or the German Wind Energy Association are therefore actively working to build wind turbines that can be better recycled and returned to the recyclable material cycle, not least against the backdrop of an ever-increasing awareness of sustainability. After all, sustainable wind energy production also contributes to this.
 

Wind turbine recycling standards: What applies, what is missing, what is coming

The recycling problem is also supported by the absence of clear standards that provide clear and, above all, mandatory guidelines at federal level. Much more so, it is the individual municipalities that decide which standards operators must follow when constructing and dismantling wind turbines. On this basis, the authorities ultimately also issue the respective authorisations. The only obligation for operators is to guarantee disposal in accordance with the German Circular Economy Act.¹

The provisional standard DIN SPEC 4866 came closest to such an industry standard: It was developed in collaboration with the Industrial Association for Repowering, Dismantling and Recycling of Wind Turbines e. V. (RDRWind), the Federal Environmental Office and the German Institute for Standardisation and published in 2020. This standard provides guidelines for dismantling, dismantling and recycling and has contributed significantly to standardising and professionalising the dismantling process. However, it has also been implemented as standard by only a few federal states and municipalities so far - but not by all.

However, this preliminary standard is not the end when it comes to standardisation in the wind energy industry: Projects such as the DIN working group “Demolition Work” are currently developing a DIN standard and, equally promising, a quality mark based on DIN SPEC 4866. Both projects are intended to ensure greater transparency and comparability on the market.¹⁰ For operators as well as authorities, municipalities and neighbours, the quality mark could serve as a transparent starting point in the future to obtain information on compliance with safety requirements and the environmental compatibility of the respective dismantling processes, among other things. 
 

Blade recycling: How startups solve the problem

And the market has also been changing on the technological side for some years now: Among other things, innovative companies are working on sustainable solutionsto simplify recycling processes and recycle blade waste. An example of this is Novo-Tech: The German company, based in Saxony-Anhalt, processes old rotor blades into terrace decking and other elements for outdoor use. The wings are combined with material residues from the wood industry for this purpose. For example, Novo-Tech recycles around 1,000 tonnes of rotor blades annually, using 100 percent green electricity.¹¹

In addition to recycling, other companies on the market also produce wind turbines or individual wind turbine elements from more environmentally friendly materials. The Swedish startup Modvion stands out here in particular: The company designs and manufactures wind turbine towers made from pure wood. Up to 144 layers of plywood are pressed and assembled into a tower in individual modules.¹² Following a prototype that Modvion built on the Swedish island of Björkö in 2020, the first commercial wooden wind turbine construction for the Swedish energy company Varberg Energie followed in 2023. With a total height of 105 metres, the tower is probably the largest wooden wind turbine in the world, according to the company.

However, there is a problem here: For the most difficult part to recycle, the blades, models made of glass- and carbon-fibre-reinforced plastics continue to be used. The sustainable added value of wooden wind turbines thus ends here at a current altitude of just over 100 metres.

A solution to this problem has been developed by the German start-up Voodin Blade Technology, which manufactures the traditionally difficult-to-recycle rotor blades entirely from wood. This will not only reduce the CO₂ emissions associated with production by 78 percent, but also the costs by as much as 20 percent.¹³ The rotor blades are made from veneered laminated wood. By using computer-controlled CNC milling machines, the manufacturing process can also be more specifically automated, which contributes to lower manufacturing costs. Production can therefore also take place closer to the wind farms themselves. This ensures shorter transport distances and thus more effective CO₂ savings.

In mid-2024, the first wooden Voodin rotor blades were installed at a German wind farm in Breuna. The next step is to produce and install larger blades with a length of 60 to 80 metres. Jorge Castillo, co-founder of Voodin, is very optimistic: "Over the last two years, we have carried out hundreds of laboratory tests to perfect the blade material. According to all our tests, our blades are even more durable than the existing fibreglass blades, as they show less fatigue and are proven to withstand all types of onshore weather conditions extremely well," Castillo explains.

Repowering as an investment opportunity: What investors need to know now

The upcoming dismantling wave is not only a technical and ecological challenge: It is also an investment issue. According to the German Wind Energy Association and Deutsche WindGuard, there is a repowering potential of up to 54 GW in the German wind power portfolio.³ Anyone investing in renewable energies must anticipate this generational change in the portfolio. 

Wind power industry: An overview of the entire life cycle

Wind power is a central and indispensable part of the German energy transition, but its sustainability potential must be considered beyond energy production in the future. Innovative and promising solutions are developing on the market to make future recycling of the plants and thus the entire life cycle of wind turbines more environmentally friendly.

Binding standards and greater transparency can also help to overcome the growing challenges of the wind energy industry in the future - and to further expand its contribution to an all-round sustainable energy economy. klimaVest, the renewable energy fund of Commerz Real, consistently pursues this approach: with a broad spread across currently assets in 6 European countries and an investment approach that takes into account repowering, circular economy and life cycle from the outset.