Wind energy is one of the greenest renewable energy sources during its operational stage. However, this is not the case during the manufacturing and end-of-life (EoL) stages. The manufacturing stage is energy intensive, and waste generated at the EoL stage is often neglected (Bonou et al., 2016; Morini et al., 2021; Ortegon et al., 2013; Savino et al., 2017; Song et al., 2009). More than 34,000 wind turbines in Europe are over 15 years old, which means they will reach the EoL stage within the next 10 years (Wind Europe, 2020). Thus, wind farm owners will be increasingly facing EoL decisions, such as product lifetime extension, decommissioning, and recycling (Walzberg et al., 2022). Furthermore, by 2050 the wind turbine sector in Europe is expected to grow by more than 400 %, exacerbating this issue with many more new wind turbines entering the market in support of the renewable energy transition (Frayle and O’Sullivan, 2021; Wind Europe and IRENA, 2018).
When looking at the manufacturing and EoL stages, the following materials used in wind turbines have the biggest impact on the environment; steel, composite materials and rare earth elements (REEs) (Jensen, 2019; Jensen et al., 2020; Liu and Barlow, 2017; Velenturf et al., 2021; Wind Europe, 2020). These materials can be divided into two groups: (1) materials for which there is an established industrial recycling route and (2) materials for which such a recycling route is not yet available. Approximately 90 % of a wind turbine consists of steel, a material with an established recycling route. Consequently, in theory between 80-95 % of a wind turbine can be recycled (Jensen, 2019; Jensen and Skelton, 2018; Tota-Maharaj and McMahon, 2021; Woo and Whale, 2022). However, in practice this percentage is much lower, namely around 44 % (Wilts et al., 2015). Because of the energy intensity of producing steel, recycling the steel of a wind farm can save thousands of tons of CO2 emissions, and it is thus extremely important to close the material loop for this metal (Jensen, 2019).
For other materials such as REEs and composite materials, there are no established recycling processes yet (Balaram, 2019; Becci et al., 2021; Job, 2013; Liu and Barlow, 2017; Pimenta and Pinho, 2011; Velenturf et al., 2021). Recycling REEs is currently not economically viable due to low available quantities and high recycling costs (Balaram, 2019). The increasing adoption of low-carbon infrastructures will lead to a rise in the demand for REEs (Balaram, 2019). It is unsure if the future demand for REEs can be met, due to environmental, geopolitical and technical constraints (Li et al., 2020). For composite materials there is also no established recycling process. These materials have a high mechanical strength, and as a result they are very difficult to recycle (Karuppannan Gopalraj and Kärki, 2020; Krauklis et al., 2021; Pickering, 2006). However, composite materials do have a high recycling potential, at least in theory. The recycling of these materials is economically viable due to their high value, and environmentally beneficial due to the high energy requirements of the production process (Shuaib and Mativenga, 2016). However, currently there is no recycling method available at a commercial scale that is both economically viable and environmentally beneficial (Liu et al., 2022; Upadhyayula et al., 2022).
Thus, several waste management issues related to the EoL stage of wind turbines can be identified. Circular strategies can offer a resolution to these issues. Circular strategies are strategies that aim to minimize waste production and maximize resource efficiency, by slowing, closing, and narrowing resource loops (Bocken et al., 2016; Hislop, 2011). Within the wind turbine industry, resource loops can be narrowed by reducing the amount of material used in the production process. Furthermore, resource loops can be slowed by prolonging the use of wind turbines, through designing for durability, maintenance and repair, remanufacturing, refurbishment, reuse, and repurposing. Moreover, resource loops can be closed through disassembly and recycling at the EoL stage (Bocken et al., 2016; Velenturf et al., 2019). However, circularity is not yet an established concept within the wind turbine industry. Attention needs to be paid to recycling and thus closing the resource loop. Furthermore, for the industry to become more circular and thus ensure future material supply and the preservation of the environment, it is important that other circular strategies that enable the slowing and narrowing of resource loops are also implemented.
Within the literature, several articles discuss circular strategies within the wind turbine industry. Mendoza et al. (2022) identifies fourteen circular strategies through a literature review. Similarly, Velenturf (2021) developed a framework consisting of eighteen circular strategies for the offshore wind industry. Woo and Whale (2022) combine a literature review with some clarifying qualitative interviews to investigate current EoL practices and their effectiveness. They recognize ten different circular strategies. In his paper, Jensen (2019) recognizes four different circular strategies, but his paper focusses on recycling. He combines a literature review with clarifying qualitative interviews to assess the net positive effect of the recycling of wind turbines. Jensen et al. (2020) describe the use of critical materials within the wind turbine industry and the role circularity can play in the EoL stage. They recognize eight different circular strategies in total. Moreover, Cooperman et al. (2021), Mishnaevsky Jr (2021) and Beauson et al. (2021) respectively discuss six, eight and five different circular strategies within the wind turbine industry.
From the existing base of literature, it can be concluded that there is no consensus on how many circular strategies there are, and how these strategies should be defined. The creation of an initial circular strategy framework for the wind turbine industry aims to bring this consensus and create a comprehensive overview of circular strategies within the wind turbine industry. Furthermore, the aforementioned papers primarily conduct literature reviews, in some cases combined with clarifying qualitative interviews. Hence, there is a need for in-depth empirical research on this topic. Therefore, this study investigates which circular strategies are currently in place within the wind turbine industry and which circular strategies, based on current challenges and opportunities, will be implemented in the future. To this end, in-depth semi-structured interviews are conducted with wind energy experts and representatives from companies within the wind turbine industry in Europe. This study focuses on the European context, since European countries have on average the oldest wind turbines, and here the wind turbines thus need to be replaced first (Majewski et al., 2022). Furthermore, companies across the entire supply chain are included, such as raw material suppliers, wind turbine manufacturers, wind farms managers, and companies involved in the EoL stage of wind turbines. Each participant is purposefully chosen, and each interview will be transcribed and analyzed afterwards using qualitative software.
Our contributions are threefold. First, this study contributes to research on circularity within the wind turbine industry. Second, this study contributes to literature on the circular economy, by providing a method to identify circular supply chain configurations. Third, this study contributes to the research on business model experimentation by providing starting points for the experimentation process. In addition, this study provides recommendations, pathways and circular supply chain configurations for companies within the wind turbine industry within Europe.
Circular economy, wind turbine industry, low-carbon infrastructure, supply chain configurations, waste management
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