Recyclability of Wind Turbines: Overview of Current Situation and Challenges

Abstract

The European energy system is increasingly incorporating renewable energies as a result of the wind power market's exponential rise. However, from a life cycle standpoint, there still exists certain issues with wind turbines, especially in end-of-life management. In this study, an overview of the current state of a wind turbine's end-of-life management is provided. Turbines’ end-of-life management practices are a difficult endeavor for completing materials loops. The current state of play demonstrates that some materials used in wind turbines are still diverted towards energy recovery or landfills rather than more virtuous management such as recycling, remanufacturing or reuse, which hinder the recyclability and thus circularity of wind turbines. Blades, rare earth elements used in permanent magnets, and critical raw materials used in alloyed components are preventing wind turbines from achieving high recyclability. The remaining difficulties to improve recycling and close the material loop for wind turbines are then highlighted.

1 Introduction

The main cumulative renewable energy sources in Europe (EU) are provided by wind and water (Eurostat 2022), yet both the shift to clean energy technologies and the EU energy carbon neutrality depend heavily on wind energy. With a cumulative installed capacity of more than 200 GW, the EU is paving the way for the use of renewable energy sources and the transition away from fossil fuels (Euro Commission 2022). Onshore and offshore locations in Europe have installed wind turbines (WT), both of which help the EU achieving its energy roadmap targets (Euro Commission 2012). WT is a heterogeneous system that couples numerous parts and components comprised of various materials. These components aid in the creation of clean and renewable energy. Nevertheless, a thorough life-cycle analysis reveals that some materials have the potential to harm the environment and require intensive energy to source and manufacture (Majewski et al. 2022). Additionally, their End-of-Life (EoL) management does not allow the deployment of virtuous R-strategies that support higher circularity goals, such as reusing or remanufacturing (EMF 2013; Morseletto 2020).

Specifically, this is the case for blades made of composite materials (Liu and Barlow 2050), or Rare Earth Elements (REEs) used in permanent magnets. Still, flows for WT’s EoL management routes diverge to energy recovery, incineration, and landfill. Thus, WT recyclability is hindered. The ability to be decommissioned, gathered, separated, and recycled is all that recycling of WT materials entails. Hence, it is crucial to evaluate WT’s recyclability.

Afterwards, the initial goal of this paper is to give a general review of the current state of wind turbine and WT material EoL management. The main obstacles to improve WT's recyclability are then listed.

2 Wind Turbine Bill of Materials

For both onshore and offshore sites, there exists two primary technical designs of wind turbines on the market: gearbox technology (geared) and direct drive (gearless) one. Although geared WT still hold the majority of the market, direct-drive WT share is rapidly rising. Less maintenance is needed for the latter, which also results in a smaller nacelle and less weight for the turbine. Although hybrid models do exist, their market adoption is quite modest. Permanent magnets and rare earth materials are mainly used in direct drive WT. In onshore and offshore applications, synchronous generators (DDSG) are one of the most used direct drive WTs. Figure 32.1 displays the typical material bill for such an onshore WT model. More than 76% of the weight of WT in foundations is made of concrete, making it the most common material used in WT foundations. Steel (and its alloys) is the second most frequently utilized material. WT nacelle and rotor also use various materials such alloys, iron, copper, and aluminum. The blades of wind generators are generally made of Glass Fiber Reinforced Plastics (GFRP). WT permanent magnets and tower magnets employ rare earth elements (REEs) and boron (B).

Fig. 32.1

Bill of materials used for DDSG WT. Average estimations from Schreiber et al. (2019). Units in tonnes. Figure made with SankeyMatic

Despite supply constraints in the EU and the rising criticality of these materials designated as strategic or critical raw materials (CRM), their use in the wind energy sector rose significantly over the last decade (WTO 2015; Euro Commission 2021). Figure 32.2 lists the most common REEs utilized in WT permanent magnets. In principle, 150–200 kg are used on average for every MW of capacity. And while Dysprosium (Dy) and Terbium (Tb) are the most frequently used heavy REEs in WT magnets, Neodymium (Nd) and Praseodymium (Pr) are the most commonly employed light REEs (light REEs are lanthanides with the lowest atomic numbers, and heavy REEs are classified considering their higher atomic weights relative to light REEs). Gadolinium is also another heavy rare earth used in WT. Even so, current and upcoming WT generations would gradually decrease their use of light REEs and phase out heavy REEs as a step towards less REEs use in wind energy technologies (Vestas 2021).

Fig. 32.2

Data from Alves Dias et al. (2020). Units in t/GW. Figure made with SankeyMatic

Bill of REEEs used for onshore and offshore WT. Average estimations for 1 GW of installed WT. Gadolinium was not captured in this sankey.

Still, current stocks and flows of REEs in the EU wind sector can be toughly estimated from the 210 GW installed capacity. Other components, such as lubricants and sulfur hexafluoride (SF6), also are utilized in WT, although at lower rates than those shown in Fig. 32.1. While more than 80% of the materials used in wind turbines can be recycled, some are lost in the recycling process or diverted to landfill and energy recovery. The management of WT materials’ current EoL is then described in general.

3 Current Situation of EoL Management: Reuse, Recycle, Recover and Landfill

Wind turbine decommissioning is not regulated in Europe. However, its management is guaranteed to either rehabilitate the wind farm site or to repower the wind farm and increase its. Resources that can be reintroduced into the economy are gathered by WT. All materials are not, however, recycled (Tazi 2018; Jani et al. 2020).

In wind farms, concrete is the most used material. The potential for recycling this material is very significant. However, it is frequently not completely removed from the soil (Tazi 2018), and it is neither cost effective nor ecologically sustainable to carry it from remote wind farm locations to recycling facilities. Its employment in repowered wind farms is particularly problematic because it requires on-site recycling, and its ability to be included into new concretes as a substitute of natural aggregates and sands is restricted subject to regulatory, standards or performance restrictions. Concrete foundations are usually either left in place or landfilled after being excavated.

In general, metals are recovered and treated according to the waste framework directive.¹ They may be reused and recycled readily, and they can be reinjected into secondary markets. A separate waste flow for recycling is possible due to the massive size of the WT system and its components. Even yet, certain partial metal flows (such those that were combined with concrete) may end up in landfills. The materials used in alloyed components, such as manganese (Mn), molybdenum (Mo), chromium (Cr), cobalt (Co), and nickel (Ni), are still included in these flows but are typically recycled together with ferrous and non-ferrous metal flows and therefore are not usually targeted for recycling.

Regarding REEs, they are typically not retrieved from magnets. The procedures currently in use are to disassemble and separate these materials, which require significant time and energy. Some approaches, such as disintegration (degradation and demagnetization carried out in a hydrogen atmosphere), permit recovering NdFeB magnet waste or powder for use in new magnets (Chowdhury et al. 2021; Coelho et al. 2021). However, such approaches are currently targeting only small magnets.

The majority of blades are made of composites, GFRP, and carbon fiber reinforced polymers, coupled with adhesives and balsa wood. The current deployed recycling methods do not recover blade materials (Jani et al. 2020). Typically, they are either delivered to landfills or cement co-processing facilities for energy recovery.

The WEEE directive² generally manages other Electronics and Electrics components from the wind turbine. In terms of WT's overall weight, electronics and electrics components make up about 1%. Fluids, lubricants, and SF6 have distinctive EoL management approaches as well and are often treated prior to the decommissioning of WT. Recyclability potential of wind turbines can be reduced if these waste flows are inadequately managed due to their comparatively high risk of contamination.

The market for second-hand replacement parts in the wind energy industry is still under development. On a global basis, initiatives are being made to offer used goods for the industry.³

Finally, repurposed solutions are prompt and mostly focus on tower and blade fragments that are converted into bike shelters, urban furniture, or included in bridge structures (Stone 2022).

As a result, not all material loops in WT could be sustained and closed.

4 Challenges in Recyclability of Wind Turbines

To help achieve a closed material loop and supply flows to secondary markets, a significant portion of wind turbine materials can be adequately recyclable. To assure greater WT recycling, there are still challenges in the wind energy value chain. The main difficulties are shown in Fig. 32.3 and are explained below.

Fig. 32.3

Main challenges for better recyclability of WT

WT are generally located in remote areas, which render recycling and proper EoL management of some WT materials not environmental nor economically effective. This is true for concrete, which has a range of ecological profitability distance of less than 100 km (Ben Fraj and Idir 2017). On-site excavation, recycling, and utilization activities are all fairly scarce on-site. Besides, no specific provision or measure exist in order to legally bind the wind farm to completely recycle WT foundations.

When it comes to recycling, the collection phase may seem routine, but this activity ensures proper management of CRM and REEs in WT. Such a concern was associated to industry incentives for high-quality recycling (Reck and Graedel 2012). Design is also recognized as a major step in enhancing recyclability and move towards design for circularity. When the service lifespan is reached, the majority of raw materials, including metals, diverge to waste management and follow the life cycle of a single use product. Such a situation necessitates sectoral and policy measures in order to close material loops on the one hand and transition to higher R-strategy on the other (Morseletto 2020). The recyclability of WT blades and less recyclable materials such components containing REEs would both be improved by design provisions like design for recycling or design for circularity.

WT recyclability currently faces significant challenges related to recycling methods and costs. One way to look at it is that the recycling technologies used for WT material recycling are somewhat constrained and overtaken by all the new design and manufacturing procedures. On the other hand, to close material loops, the cost of recycling is still a frontier that needs incentives and legislative support. The absence of eco-design and design for circularity principles further emphasizes this phase shift. To achieve improved circularity of products, it is vital to distribute the burdens along the value chain in order to shut material loops. Additionally, there should be incentives for using cutting-edge technologies for recycling and sorting. If EoL initiatives are successful, contamination of WT wastes can also be controlled.

The wind energy sector has already highlighted the first measures to reduce the usage of REEs from the design phase. Such procedures ought to be made standard, and they ought to be supported by enforceable legal measures that address this problem. CRM management need to be covered by a cross-sectoral EU regulation to guarantee proper handling and recycling of these materials. The recyclability of WT can also be improved by using alternative materials. Blades, alloyed parts, and REEs are examples of them. The wind energy industry needs stronger and more appropriate regulatory measures from the perspective of execution in order to fully realize WT’s potential for recycling and/or circularity. These actions can be taken anywhere throughout the value chain and can be made stronger by standards.

To assure the use of recyclable materials in WT, policy measures can be used at the design phase. They can also be used as tools to extend the lifespan of wind turbines.

In order to monitor and guarantee effective EoL management (including WT recycling), policy tools can also be used. Legal tools can also promote secondary markets that improve recycling operations. These measures ought to lower supply-related risks and due diligence.

According to Fig. 32.4, when compared to the existing supply, Dy and Tb will continue to be in high demand in 2030 and 2050. The rising demand for such minerals for clean technology would also increase the supply risk. However, it is anticipated that with current practices, the yearly EU REEs requirement for wind turbine use may not be met. Overcoming these obstacles might reduce this risk.

Fig. 32.4

Figure adapted from Carrara et al. (2020)

Maximum EU annual WT REEs demand in 2030 and 2050; compared with current material availability. Gadolinium was not captured in this figure.

5 Conclusion

In summary, this paper illustrates the current state of play around a wind turbine's end-of-life management and highlights the difficulties and main gaps that need to be addressed to improve recyclability of wind turbines and circularity performances in the wind energy industry. This paper discusses various end-of-life activities, such as inter-alia decommissioning, recycling, reusing, and repurposing. The use of non-recyclable materials for wind turbine blades, such as composites and glass fibers, is the main factor impeding their capacity to be recycled.

Additionally, wind turbines do not fully recover rare earth elements, essential raw materials, and other strategic and critical materials for alloyed components. These materials continue to present considerable challenges for a wind turbine to achieve high levels of recyclability. The lack of sustainable design principles and the advancement of collection, sorting, and recycling technologies are the remaining difficulties.

Finally, appropriate policy instruments that encourage investments and actions towards higher recyclability of wind turbines have to be woven into the plan to attain higher recyclability of wind turbines.

Everything is a work in progress to tackle these issues from a circular economy perspective.