## 1 Introduction  
Wider use of clean and renewable energy resources, which ensure near-zero green-house gas emissions, as opposed to burning fossil fuels, is a way to ensure future sustainability worldwide. The European Union (EU) has approved policies that aim to raise the total energy generation from renewables across the EU by 2030 to 27%, and many governments and corporations have pledged to use only clean energy by 2050 [1, 2, 3, 4]. Recently, wind energy has been identified as one of the most sustainable, mature, environmentally friendly, cheapest, and commercially developed renewable energy sources. Based on the technical, economic, social, and environmental criteria, the evaluation index system of a wind farm was established [5, 6]. As a result, a large number of wind farms are being installed, and their number is constantly growing [7, 8, 9]. The wind farms in Europe have generated 458 TWh of electricity and covered 16% of the electricity demand in 2020. Approximately 220 GW of wind power capacity are installed in Europe, but it is expectedthat Europe will be able to use 105 GW of the new wind power capacity installed over the next five years [10]. In addition, the rapid development of technology is changing the geometry and capacity of wind turbines. Combining a bigger rotor, longer blades, and higher capacity factor allows generating more power. Thus, the blade length has been prolonged from 18 m in a 0.1 MW turbine in the year 1985 to around 107 m in a 12 MW offshore turbine in the year 2017 [11; 12]. However, this development means that the world faces an environmental challenge due to the increasing number of WTBs being replaced and the mass of decommissioned WTB composite material. In recent decades, since 1958, when the WTB was first made of glass fibre-reinforced plastic (GFRP), composite materials have become widely used in the manufacture of WTB [13; 14]. Glass fibre plastics (GFRPs) and carbon fibre-reinforced plastics (CFRPs) are commonly used in the manufacture of WTBs and constitute the majority of the blade material [15]. Due to the specific stiffness and strength, superior fatigue and corrosion resistance, and flexibility in design and manufacturing, the utilisation of these materials has increased significantly and keeps constantly increasing [13; 14; 15]. Such properties were achieved by curing composites. Then the polymers became cross-linked; however, this process is irreversible and complicates recycling such material [13]. Typically, the service life of the WTBs is approximately 20-25 years; after this term passes, they should be renewed, or their service life expires [16]. Various factors influence the expiration of the service life of WTB, for instance, defects occurring during the manufacture of WTBs and their operating service life. About 85% of turbine components such as steel, copper wire, electronics, and gearing can be recycled or reused [3]. However, the WTBs consist of different materials and elements: the complex fibre composites with multilayer structures bonded by an adhesive. Separating such materials is an extremely difficult task [17; 18]. The study conducted in Sweden shows that significant waste amounts of WTBs will arise in the future [19]. The waste of blade material is expected to grow, with \(\sim\)12% increase per year until around 2026, and then 41% per year until 2034, reaching 28,100 tons [19]. With the number of WTBs disposal increasing, most of them are left to accumulate in landfills or some blades are burned [3; 17]. According to the 'Waste Framework Directive' of the European Union, waste prevention is a preferred option, and sending waste to landfills should be the last resort [20]. The waste hierarchy according to the 'Waste Framework Directive' of the European Union [7] is presented in Figure 1.  
For this reason, inspection and maintenance activities should be applied to extend the service life of turbines. [9]. During the production, it is necessary to carry out tests, inspections, and monitoring, as well as to install the service phase [21].