METHOD FOR PREPARING A WIND TURBINE BLADE FOR RECYCLING

The present disclosure relates to a method of preparing a wind turbine blade for recycling. In particular the present disclosure relates to a method for preparing a wind turbine blade for recycling by sectioning the wind turbine blade into several parts based on the type of material and/or the material composition in the individual parts. More specifically, the present disclosure pertains to a method for preparing a wind turbine blade for recycling by sectioning the wind turbine blade into several parts such as a bow panel, an aft panel, a spar cap, a shear web, etc.

BACKGROUND

The use of wind turbines to generate electricity is a growing market and an important contributor to combat climate changes caused by the use of fossil fuels as an energy source. The Global Wind Energy Council estimated in 2016 that there were more than 341,000 wind turbines running worldwide and that this figure will continue to increase significantly over the next few decades with the accelerated development of wind energy. A number of companies are producing blades for the growing number of turbines worldwide and these blades need to be periodically replaced when they wear out, become damaged or as part of upgrades to enhance energy yield (may be known as "repowering"). In addition, older generations of wind turbines are being decommissioned as they exceed their expected 20-30 years lifespan. Thus, there is a huge potential in recycling the materials in decommissioned wind turbines.

The dismantling of a wind turbine is not an easy task, and this is traditionally done by splitting the turbine into four large sections: the concrete base, the mast, the rotor blades (usually three), and the nacelle. Each section is either very heavy or very long and may therefore be sectioned into smaller parts before transport to recycling plants or landfills.

Although the prospect of recycling wind turbine blades may be attractive and consistent with the notion of wind energy as a "green" power source, it has not previously been proven technically or economically feasible. As wind turbines have increased in size wind turbine blades have increased too, resulting in increasing costs for disposal or recycling of the wind turbines blades once decommissioned. However, thousands of rotor blades fitted worldwide are coming to the end of their service. Thus, new innovative recycling solutions are needed to exploit the recycled material in the most optimal way, save costs and lower the environmental impact of recycling wind turbines. In particular, new solutions are needed such that high value materials in the wind turbine blades may be recovered and reused again. Modern wind turbine blades are made from composite materials and are usually assembled from two half-shells (i.e. an upper half-shell and lower half-shell) although wind turbine blade manufacturing technologies also exist, wherein the wind turbine shell is manufactured as a single structure. In cases where the blade is made by assembly of two half-shells, the two half-shells are glued together in a laminate joint at the leading edge and trailing edge of the blade. Each half-shell (or each shell-side in case of a single-structure blade shell) comprises a spar cap (i.e. a thick fiber reinforced portion of the shell) flanked by a bow panel towards the leading edge and an aft panel towards the trailing edge of the blade. The spar caps are normally made of a laminate comprising unidirectional fibers such as glass or carbon fibers embedded in a resin polymer matrix (i.e. fiber- reinforced polymers) with outer layers of bi-axial fiber-reinforced polymers. The spar caps provide the wind turbine blade with its bending strength and stiffness along the blade span due to the thickness and the presence of a large amount of reinforcement fibers. The bow panels and aft panels are usually made in a sandwich construction comprising a core of light material such as balsa wood, PET or PVC foam, to lower the total weight of the blade without compromising the strength. The light core is embedded in an outer and inner laminate shell typically of bi-axial fiber-reinforced polymers. The spar caps in the upper and lower shell are typically bonded together by shear webs, which are normally also made in a sandwich construction comprising a core of light material embedded between a laminate shell made from bi-axial fiber-reinforced polymers. Thus, a wind turbine blade may comprise a number of different materials, which may differ between different blade parts.

Today recycling of wind turbine blades typically involve sectioning the wind turbine blade into smaller blades parts and crushing and grinding the blade parts to obtain a granulate comprising the materials present in the wind turbine blade. The granulates may be used, e.g., as solid fuel for the cement industry to replace traditional fossil fuels or in construction as part of a cement matrix in concrete. Alternatively, the granulates may be recycled to a further extent typically by chemical and/or thermal recycling such as solvolysis and/or pyrolysis for recovery of energy rich organic fractions and/or isolation of higher value components, such as carbon fiber fractions.

However, the currently known recycling methods are very limited commercially attractive. Thus, there is a need in the art for new recycling methods of wind turbine blades that aim at improving methods for recycling of composite structures, such as wind turbine blades. Among other objectives, the current disclosure set out to provide a more valuable, predictable and environmentally sustainable recycling of composite structures, in particular wind turbine blades. SUMMARY

It is an object of the present disclosure to provide an improved method for preparing a wind turbine blade for recycling. Accordingly, the present disclosure provides a method for preparing a wind turbine blade comprising sectioning the wind turbine into multiple parts comprising different types of materials and/or material compositions. For example, the wind turbine blade may be cut such that some blade parts comprise mainly fiber rich fractions (e.g. reinforcement fibers), other blade parts comprise mainly core rich fractions (e.g. balsa or foam) and yet other blade parts comprise mainly glue rich fractions (e.g. vinylester, epoxy, polyurethan), etc.

The disclosed method provides for a more intelligent sectioning of the wind turbine blade facilitating more homogenous wind turbine blade parts and in turn more homogenous granulates in terms of material content by partial or complete separation of the individual materials in the wind turbine blade. Thus, the method provides a more tailored and efficient recycling and more valuable recycled products compared to today's recycling of wind turbine blades. In the present context "recycling" should be understood in broad terms including also recovery, co-processing, repurpose and/or reuse. Recycling may include breaking down used items (e.g. wind turbine blades) to make raw materials for the manufacture of new products. Recycling in the present context may also include coprocessing, which may refer to the use of waste (e.g. granulates from a wind turbine blade) as a raw material and/or as a source of energy to replace natural mineral resources and fossil fuels such as coal, petroleum and gas in industrial processes, mainly in energy intensive industries such as cement, lime, steel, glass, and power generation. Recycling in the present context may also include recovery, which may refer to using waste (e.g. fibers obtained from a composite material) as an input material to create valuable products as new outputs or recovering energy from waste. Recycling in the present context may also include reuse, which may refer to the action or practice of using an item (e.g. fibers isolated from a composite material, for its original purpose (i.e. as reinforcement fibers). Alternatively, reuse may refer to using an item (e.g. beams from a spar cap) to fulfil a different function (e.g. reinforcement beams in construction), which may be also referred to as repurpose.

Thus, a first aspect the present disclosure relates to a method for preparing a wind turbine blade for recycling according to claim 1. The present disclosure further relates to a system for preparing a wind turbine blade for recycling, according to claim 20.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a schematic diagram illustrating an exemplary wind turbine, Fig. 2 is a schematic diagram illustrating an exemplary wind turbine blade for processing according to the method disclosed herein,

Fig. 3 is a schematic diagram illustrating an exemplary wind turbine blade separated into different layers,

Fig. 4 is a schematic diagram illustrating a cross-section of an exemplary wind turbine blade composed of different wind turbine blade parts.

Fig. 5 is a schematic diagram illustrating the crushing and grinding of individual wind turbine blade parts.

DETAILED DESCRIPTION

The disclosure and particular embodiments of the disclosure will be described in the following. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

Wind turbine blades exist in numerous designs and are complex to manufacture. A wind turbine blade is normally manufactured from composite materials and assembled from two half-shells that are glued together to form the blade. Each half-shell consists of several parts such as a bow panel, a spar cap and an aft panel. The spar caps in each shell are connected by shear webs provided between the half-shells. Each of the parts in the blade may comprise materials not present in other parts or may comprise the same materials but in different relative content. For example, the bow panel, aft panel and shear webs are typically manufactured in a sandwich construction comprising a core of a light material such as balsa wood, PVC or PET foam to lower the weight of the blade which is not present in other parts of the blade such as the spar cap. The core in the sandwich construction is encapsulated in a laminate comprising a polymer matrix reinforced with a suitable fiber such as glass or carbon fibers. The inventors of the present invention has found that a more optimal recycling of the wind turbine blade may be obtained by recycling these parts separately to obtain more homogenous end products in terms of material content (i.e. less complex end products).

Thus, in a first aspect the present disclosure relates to a method for preparing a wind turbine blade for recycling, wherein the wind turbine blade comprises a plurality of materials including a primary material and a secondary material, wherein the secondary material is different than the primary material, the method comprising: providing the wind turbine blade,

• sectioning the wind turbine blade into a plurality of wind turbine blade parts comprising a first wind turbine blade part and a second wind turbine blade part, wherein the second wind turbine blade part is different than the first wind turbine blade part, and wherein the first wind turbine blade part comprises a first relative amount of the primary material and a first relative amount of the secondary material, and the second wind turbine blade part comprises a second relative amount of the primary material and a second relative amount of the secondary material.

The first relative amount of the primary material may be different, such as larger, than the second relative amount of the primary material. The second relative amount of the secondary material may be different, such as larger, than the first relative amount of the secondary material. For example, the first relative amount of the primary material may be at least two times the second relative amount of the primary material. The second relative amount of the secondary material may be at least two times the first relative amount of the secondary material.

The wind turbine blade is sectioned into at least two parts (i.e. a first and a second wind turbine blade part) in the method disclosed herein. In some embodiments the wind turbine blade may be sectioned into more parts (e.g. including a third, fourth and/or fifth blade part etc.). The number of parts may be dependent on the structural design of the wind turbine blade, the material composition in the wind turbine blade parts, the intended further recycling steps of the wind turbine blade parts, and/or the intended use of the recycled product. For example, the type of reinforcement fiber used or the fiber direction, e.g. unidirectional or biaxial, may differ from one part of the blade to another part. Also the length of the reinforcement fibers may differ from one part of the blade to another, e.g. in one part of the blade chopped fibers may be used, in another part of the blade continuous fibers may be used. Likewise, the type of polymer matrix or the relative composition of a reinforcement fiber compared to the polymer matrix may vary between different parts of the blade such as between a spar cap and a shear web or bow panel.

For example, the plurality of wind turbine blade parts may comprise two or more of a spar cap, a bow panel, an aft panel, a shear web, a trailing edge part, a leading edge part, a root section, a shell portion of the bow panel, the aft panel or the shear web, core portion of the bow panel, the aft panel or the shear web. For example, the plurality of wind turbine blade parts may comprise one or more spar caps, one or more bow panels, one or more aft panels, one or more a shear webs, a trailing edge part, a leading edge part and a root section. Alternatively, the plurality of wind turbine blade parts may comprise one or more a shell portions of one or more bow panels, one or more aft panels and/or one or more shear webs and core portion of the bow panels, aft panels and/or shear webs. For example, the first wind turbine blade part may be a shell portion of one or more bow panels, one or more aft panels and/or one or more shear webs, and the second wind turbine blade part may be a core portion of the one or more bow panels, one or more aft panels and/or one or more shear webs.

As a non-limiting example, if a part of the recycled wind turbine blade is intended to be used as a fuel source any part(s), such as an aft or bow panel, comprising materials that pose an environmental hazard upon burning such as PVC, may be sectioned from the remaining parts of the wind turbine blade in order to e.g. lower the environmental impact of the fuel source. As another non-limiting example, if the wind turbine blade is intended to be recycled using e.g. chemical or thermal recycling the wind turbine blade may be sectioned into a blade part having a relative high fiber content (i.e. high weight percent of reinforcement fibers) such as a spar cap compared to blade parts having a lower fiber content such as an aft or bow panel. Such sectioning of the wind turbine blade into specific parts allow for more homogenous blade parts in terms of material compositions and in turn results in less complex and more valuable end products. Furthermore, the sectioning and recycling of more homogenous blade parts allow for a more optimal selection of process parameters during e.g. thermal and/or chemical recycling.

In an embodiment, the wind turbine blade is sectioned into a first wind turbine blade part and a second wind turbine blade part. In another embodiment, the wind turbine blade is sectioned into a first wind turbine blade part, a second wind turbine blade part and a third wind turbine blade part. In yet another embodiment, the wind turbine blade is sectioned into a first wind turbine blade part, a second wind turbine blade part, a third wind turbine blade part and a fourth wind turbine blade part. In yet an embodiment, the wind turbine blade is sectioned into a first wind turbine blade part, a second wind turbine blade part, a third wind turbine blade part, a fourth wind turbine blade part and a fifth wind turbine blade part. In an embodiment each of the first, second, third, fourth or fifth blade part may be selected from the group consisting of a bow panel, an aft panel, a spar cap, a shear web, a trailing edge part of the blade, a leading edge part of the blade, a root section of the blade, a shell portion of the bow panel, the aft panel or the shear web, and a core portion of the bow panel, the aft panel or the shear web. For example, the first wind turbine blade part may be a spar cap, the second wind turbine blade part may be a bow panel, the third wind turbine blade part may be an aft panel, the fourth wind turbine blade part may be a shear web, and/or the fifth wind turbine blade part may be an edge part, such as a trailing edge part or a leading edge part. In another example, the first wind turbine blade part may be a shell portion of one or more bow panels, one or more aft panels and/or one or more shear webs, and the second wind turbine blade part may be a core portion of the one or more bow panels, one or more aft panels and/or one or more shear webs. Furthermore, the third wind turbine blade part may be a spar cap. The wind turbine blade may be sectioned in as many and any blade parts as desired depending on the design of the wind turbine blade and material composition in the individual parts of the wind turbine blade.

The plurality of wind turbine blade parts may comprise a primary and a secondary material. The plurality of wind turbine blade parts may comprise further materials such as a tertiary, quaternary, quinary and/or senary material. The primary, secondary, tertiary, quaternary, quinary and/or senary material may be different materials, e.g. the secondary material may be different than the primary material, the tertiary material may be different than the primary material and the secondary material, the quaternary material may be different than the tertiary material, the primary material and the secondary material, the quinary material may be different than the quaternary material, the tertiary material, the primary material and the secondary material, and the senary material may be different than the quinary material, the quaternary material, the tertiary material, the primary material and the secondary material. The primary, secondary, tertiary, quaternary, quinary and/or senary material may each be selected from the group consisting of a reinforcement fiber (e.g. glass fiber and/or carbon fiber), a polymer matrix (e.g. epoxy, vinylester or polyester), a sandwich core material (e.g. balsa wood, polyethylene (PET) foam, or polyvinylchloride (PVC) foam), metal or a hardened glue (e.g. polyurethane glue or epoxy glue). For example, the primary material may be a first reinforcement fiber, e.g. glass fiber. The secondary material may be polymer matrix, e.g. epoxy, vinyl ester and/or polyester. The tertiary material may be a second reinforcement fiber, e.g. carbon fiber. The quaternary material may be a sandwich core material, e.g. balsa word, polyethylene (PET) foam and/or polyvinylchloride (PVC) foam. The quinary material may be a metal, e.g. steel. The senary material may be hardened glue, e.g. polyurethane glue and/or epoxy glue. The reinforcement fiber, such as the first reinforcement fiber and/or the second reinforcement fiber, may be selected from the group consisting of a carbon fiber, a graphite fiber, a glass fiber, a boron fiber, a ceramic fiber, an aramid fiber, a polyolefin fiber, a polyethylene fiber and a hybrid fiber. The polymer matrix may be made from a resin material comprising thermoplastic resins such as polyamides, polyesters (e.g. thermoplastic polyesters, such polyesters based on polybutylene terephthalate (PBT) and polyethylene terephthalate (PET)), polyolefins and fluoropolymers, thermosetting resins such as polyisocyanates, epoxides, bismaelimides, polyimides, bezoxazines, cyanate esters, and polyesters (e.g. thermosetting polyester, e.g. polyester resin) or hybrid polymer resins with properties of both thermosetting resins and thermoplastic resins or other suitable resin materials. The sandwich core material may be selected from the group consisting of a wood core, such as balsa or cedar wood; a polymer foam core, such as a polyurethane (PU) foam, polyetherimide (PEI) foam, a polyisocyan urate (PIR) foam, a polymethacrylimide (PMI) foam, a polystyrene (PS) foam, a polyethylene terephthalate (PET) foam or polyvinyl chloride (PVC) foam; a honeycomb core such as a glass cloth honeycomb core or mixtures of any thereof. The present disclosure provides for an improved method for recycling a wind turbine blade to recover especially more valuable materials, such as fibers, in a more optimal way. For example, the spar caps of the wind turbine blade have a high content of reinforcement fibers (i.e. high weight percent of reinforcement fibers) and therefore possess substantial material value compared to e.g. the aft or bow panels having a lower content of reinforcement fibers (i.e. lower weight percent of reinforcement fibers). Thus, separating these parts early in the recycling process facilitates retrieval of the more valuable materials.

In larger wind turbine blades the aft and bow panels usually comprise the same materials and are typically made in a sandwich construction comprising a sandwich core material, embedded in a fiber reinforced polymer matrix. Therefore, these parts of the wind turbine blade have a relative lower fiber content compared to, e.g., the spar cap. In other wind turbine blades the aft panels and bow panels may comprise different materials e.g. a different core material, or the aft panels and bow panels may comprise the same materials but in a different relative amount (i.e. in different weight percentages). As a non-limiting example, e.g. the fiber to polymer matrix ratio between the aft panels and bow panels may vary and/or the composite material to core material ratio may vary between an aft panel or bow panel. As another non-limiting example in smaller wind turbine blades the bow panels may be manufactured only from a fiber reinforced polymer, and thus may not comprise a light core material at all. The shear webs in a wind turbine blade is normally also manufactured using a sandwich construction. In some examples, the shear webs may comprise different materials than the materials present in the aft or bow panels e.g. a different core material, or the shear webs may comprise the same materials as the aft or bow panels but in a different relative amount (i.e. in different weight percentages). Furthermore, the material composition may vary along the length of the shear webs, e.g. the shear webs near the blade tip may be made from pure laminate, whereas a sandwich construction may be used nearer to the blade root. Thus, separating these parts early in the recycling process may facilitate retrieval of the more valuable materials.

Furthermore, it may be advantageous to separate the shell portion and the core portion of the sandwich constructions, e.g. of the aft or bow panels or shear webs, to obtain a shell portion mainly comprising fiber composite and a core portion mainly comprising sandwich core material.

The leading edge of the wind turbine blade and the trailing edge of the wind turbine blade are normally a laminate joint (i.e. two laminate elements, e.g. two half shell edges comprising the same fiber reinforced polymer matrix that are bonded/glued together), although wind turbine blade manufacturing technologies also exist, wherein the wind turbine shell is manufactured as a single structure. Thus, in some embodiments the wind turbine blade is sectioned into a plurality of blade parts comprising a first wind turbine blade part, e.g. being a spar cap, and a second wind turbine blade part, e.g. being a bow panel or a shell portion or a core portion of the bow panel. In some embodiments, the plurality of wind turbine blade parts comprises a third wind turbine blade part, wherein the third wind turbine blade part may be an aft panel or a shell portion or a core portion of the aft panel. Thus, in some embodiments, the first wind turbine blade part is a spar cap, the second wind turbine blade part is a bow panel or a shell portion or a core portion of the bow panel and the third wind turbine blade part is an aft panel or a shell portion or a core portion of the bow panel. In some embodiments, the plurality of wind turbine blade parts comprises a fourth wind turbine blade part, wherein the fourth wind turbine blade part may be a shear web or a shell portion or a core portion of the shear web. Thus, in some embodiments, the first wind turbine blade part is a spar cap, the second wind turbine blade part is a bow panel or a shell portion or a core portion of the bow panel, the third wind turbine blade part is an aft panel or a shell portion or a core portion of the aft panel and the fourth wind turbine blade part is a shear web or a shell portion or a core portion of the shear web. In some embodiments, the plurality of wind turbine blade parts comprises a fifth wind turbine blade part, wherein the fifth wind turbine blade part may be a trailing edge part of the blade or a leading edge part of the blade. Thus, in some embodiments, the first wind turbine blade part is a spar cap, the second wind turbine blade part is a bow panel or a shell portion or a core portion of the bow panel, the third wind turbine blade part is an aft panel or a shell portion or a core portion of the aft panel, the fourth wind turbine blade part is a shear web or a shell portion or a core portion of the shear web, and the fifth wind turbine blade part is a trailing edge part of the blade or a leading edge part of the blade. In some embodiments, the plurality of wind turbine blade parts comprises a sixth wind turbine blade part, wherein the sixth wind turbine blade part may be a root section of the blade. Thus, in some embodiments, the first wind turbine blade part is a spar cap, the second wind turbine blade part is a bow panel or a shell portion or a core portion of the bow panel, the third wind turbine blade part is an aft panel or a shell portion or a core portion of the aft panel, the fourth wind turbine blade part is a shear web or a shell portion or a core portion of the shear web, the fifth wind turbine blade part is a trailing edge part of the blade or a leading edge part of the blade and the sixth wind turbine blade part is a root section. A root section of the wind turbine blade may be used to attach the blades to the rotor hubs, e.g. the root section may comprise connection elements, such as T-bolt connections. The root section may comprise a majority of a metal in weight percent (w/w%).

The sectioning may be performed to provide wind turbine blade parts of the upper and/or lower half-shell of the wind turbine blade. For example, the wind turbine blade may be sectioned into a plurality of wind turbine blade parts comprising a spar cap from the upper half-shell and/or a spar cap from the lower half-shell, a bow panel from the upper half-shell and/or a bow panel from the lower half-shell, and/or an aft panel from the upper half-shell and/or an aft panel from the lower half-shell.

The sectioning of the wind turbine blade may be performed with conventional means known in art using a cutting tool, e.g. selected from the group consisting of a wire saw, e.g. having an endless/loop abrasive cable or and oscillating/reciprocating cable, a circular saw, an impact blade, a torch and/or a waterjet.

Once the wind turbine blade has been sectioned into the plurality of wind turbine blade parts, the plurality of wind turbine blade parts, e.g. the first, second, third, fourth, fifth and/or sixth wind turbine blade parts, may be subjected to further recycling steps separately. Preferably one or more of the plurality of wind turbine blade part(s) is sectioned into smaller parts (i.e. first wind turbine blade parts and/or second wind turbine blade parts) having a length of 2-3 meters before subjecting them to further recycling steps such as crushing and grinding separately. One or more of the plurality of wind turbine blade parts, such as the first, second, third, fourth, fifth and/or sixth wind turbine blade part(s), may be cut into smaller blade parts, e.g. of substantially the same length. Alternatively, one or more of the plurality of wind turbine blade parts, such as the first, second, third, fourth, fifth and/or sixth wind turbine blade part(s) may be cut to provide blade parts of different sizes and/or shapes.

After sectioning, one or more of the plurality of wind turbine blade parts, such as the first, second, third, fourth, fifth and/or sixth wind turbine blade part(s), may be subjected to crushing and/or grinding separately into a respective plurality of granulate(s), typically having a maximum length dimension in the range between 50 pm - 10 mm. The grinding may be performed in a single grinder or a sequence of continuously finer grinding steps to obtain composite material granulates of a desired size.

In some embodiments the first wind turbine blade part may be subjected to mechanical crushing and/or grinding to obtain a first granulate. By crushing and/or grinding the first wind turbine blade part, the first granulate may comprises the first relative amount of the primary material and the first relative amount of the secondary material.

The second wind turbine blade part may be subjected to mechanical crushing and/or grinding to obtain second granulate. The second wind turbine blade part may be crushed and/or grind separate from the first wind turbine blade part. By crushing and/or grinding the second wind turbine blade part, e.g. separate from the first wind turbine blade part, the second granulate may comprises the second relative amount of the primary material and the second relative amount of the secondary material. If the blade is sectioned into more wind turbine blade parts (e.g. a third, fourth, fifth and/or sixth wind turbine blade part) each blade part may be subjected to mechanical crushing and/or grinding separately to obtain a third, fourth, fifth and/or sixth granulate, respectively, e.g. having different material compositions. For example, the third wind turbine blade part may be mechanically crushed and/or grinded, e.g. separate from the first wind turbine blade part and the second wind turbine blade part, to obtain third granulates separate from the first granulates and second granulates, such that the third granulates comprises the third relative amount of the primary material and the third relative amount of the secondary material.

Usually crushing is needed prior to grinding unless the wind turbine blade is sectioned into blade parts that are small enough for the grinder to handle. Crushing is also often referred to as shredding in the art and the terms may be used interchangeably. Likewise, grinding is also often referred to as milling in the art and the terms may be used interchangeably. The crushing/shredding may be performed in a single crushing/shredding step or a sequence of continuously finer crushing/shredding steps. The crushing step may be performed with conventional crushing means such as by feeding e.g. the wind turbine blade part to a feed bin of a crushing machine and conveying the wind turbine blade part from the feed bin to a rotating crushing drum. The crushing drum may be equipped with e.g. teeth crushing the blade part in the rotating crushing drum to produce a plurality of blade pieces. Alternatively, a cutting or crushing mill may be used instead of a crushing drum. Both have their own benefits: cutting mills give more homogeneous fiber length distribution and longer fibers, whereas hammer mills don't have blades that require sharpening, thus reducing wear and increasing the output. The blade pieces typically have a maximum length dimension in the range between about 20 mm and about 100 mm following the step of crushing, more preferably between about 50 mm and about 75 mm following the step of crushing. Cutting, crushing and grinding are typically associated with generation of airborne particles that may have a negative impact on human health and pollute the environment. Thus, the sectioning, crushing and/or grinding may be performed using dust suppression means to avoid any local pollution threat in terms of air borne resin and/or fiber particles and assure employee safety. Any conventional dust suppression may be used such as liquid or foam spray, vacuum entrapment, filters, or other suitable dust suppression means known in the art. In embodiments using liquid or foam spray an atomized spray may be used to cover the area of cutting, crushing or grinding machine. In an embodiment, the crushing and/or grinding machine may include internal dust suppression measures such as a mounted dust collection rig.

In a preferred embodiment, the plurality of granulates, e.g. the first, second, third, fourth, fifth and/or sixth granulate, is subjected to chemical and/or thermal recycling separately. Thereby, the plurality of granulates may be converted into separate organic fractions and optionally separate fiber fractions. For example, the first granulate may be converted into a first organic fraction and optionally a first fiber fraction, and/or the second granulate may be converted into a second organic fraction and optionally a second fiber fraction. The second granulate may be subjected to chemical and/or thermal recycling separate from the first granulate. In embodiments where the wind turbine blade is sectioned into more wind turbine blade parts (e.g. a third, fourth, fifth and/or sixth wind turbine blade part etc.) to obtain a third, fourth, fifth and/or sixth granulate having different material composition, each granulate may be subjected to chemical and/or thermal recycling separately to obtain a third, fourth, fifth and sixth organic fraction and optionally a third, fourth, fifth and sixth fiber fraction.

In an embodiment only some of the granulates, e.g. the first granulate, is subjected to chemical and/or thermal recycling to liberate the fiber, whereas the remaining granulates, e.g. the second, third fourth, fifth and/or sixth granulate, may be sold separately and used, e.g., in construction or as an energy source. The first granulate may originate from a spar cap or a shell portion of a shear web, aft panel or bow panel, containing the majority of reinforcement fibers in the wind turbine blade, thereby making the first granulate the most suitable for further processing to liberate and recover the reinforcement fibers.

Chemical recycling, such as solvolysis uses chemical depolymerization of the resin matrix by using heated solvents or solvent mixtures. Depending on the solvent, it can be further classified as hydrolysis (using water), glycolysis (using glycols), and acid digestion (using acid). Thus, solvolysis decompose the polymer resin in the composite material granulates in the presence of a solvent, typically water such that the polymer is hydrolyzed into an organic fraction and thereby liberating the fiber fraction in the composite material granulates. Thus, the solvolysis not only allow recovery of a fiber fraction but also allows for recovery of the monomers used in the resin. These monomers may be subjected for further purification steps such as distillation under vacuum that allow them to be used as part of a resin in construction of new wind turbine blades. In the present context it should be understood that the solvolysis may be performed under any suitable solvolysis conditions known in the art by using different solvents, additives, pressures, temperatures and catalysts such as those described in e.g. Oliveux et al., 2015. In one embodiment the solvolysis may be performed under supercritical conditions. A supercritical fluid has the usual meaning in the art and refers to any solvent at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. Without being bound by theory supercritical conditions allow for better penetration of the resin by the solvent and a more effective solvolysis.

Thermal recycling, such as pyrolysis decompose the polymer resin in the granulates at high temperature typically in the absence of oxygen under an inert atmosphere (or in the presence of small amounts of oxygen) to liberate and recover the fibers. The pyrolysis processes typically operate between 450 °C and 700 °C, depending on the type of resin/polymer matrix. Polyester resins decompose fully at a temperature of 400-450 °C, whereas epoxides or thermoplastics such as polyether ether ketone (PEEK) require higher temperatures of 500-550 °C. The high temperature breaks down the resin into compounds of lower molecular weight, such as gases and crude oils (i.e. liquid organic fraction) thereby liberating the fiber fraction. The gases that evolve during pyrolysis may be used as fuel to provide heat for the process. Any conventional types of pyrolysis such as classic conveyor pyrolysis and fluidized-bed pyrolysis or other pyrolysis-based methods such as microwave-assisted pyrolysis, superheated steam pyrolysis, catalytic pyrolysis and gasification may be used.

Today the recycling of wind turbine blades typically involves sectioning the wind turbine blade into smaller blades parts and crushing and grinding the blade parts to obtain a complex granulate mixture comprising the materials present in the wind turbine blade. The use of such a complex granulate mixture comprising different materials and/or having different material compositions is less optimal from a recycling perspective. One reason being that if the granulates are to be further recycled with e.g. thermal or chemical recycling the unknown and varying material composition in the granulates prevents selection of optimal process parameters during the further recycling steps. Another reason being that the chemical and thermal recycling "dissolves" the resin matrix and creates more complex organic fractions that require further purification in order to be used e.g. in the production of fine chemicals. Yet another reason being that, wind turbine blades comprising parts with different fibers such as carbon and glass fibers are recovered as a mixed fiber fraction which substantially lower the value and/or quality of the recycled fibers. Finally, since the properties of the granulates vary between different recycled wind turbine blades they may perform differently and unpredictably if incorporated in other products such as a cement matrix or if used a fuel source. Furthermore, wind turbine blades may also comprise materials that create hazardous chemicals which are harmful to the environment or corrosive to process equipment during e.g. chemical/thermal recycling or upon ignition/burning. One such example is wind turbine blades comprising PVC which generates toxic and corrosive gases such as HCI and toxic compounds such as dioxins.

The present invention allows for recycling of a wind turbine blade into several individual and more homogenous granulates in terms of the material types present therein (i.e. a primary, secondary, tertiary, quaternary, quinary and/or senary material) and/or the material composition (i.e. the relative content of a material in weight percent). For example, a granulate obtained from a first wind turbine blade part, such as a spar cap, may primarily contain first reinforcement fiber, such as carbon fiber, and secondly polymer matrix, whereas another granulate, e.g. obtained from a second wind turbine blade part, such as a bow panel, may primarily contain polymer matrix and secondly a second reinforcement fiber, such as glass fiber. Alternatively or additionally, a first granulate obtained from a first wind turbine blade part and a second granulate obtained from a second wind turbine blade part may contain the same types of material but in different relative amounts (i.e. in different weight percentages). The granulates obtained by the disclosed method therefore allow for less complex end products after, e.g., thermal/chemical recycling and more uniform and predictable properties if incorporated into other products such as part of a cement matrix in construction. Furthermore, if the granulates are to be recycled/processed further the more homogenous granulates in terms of material composition, allow for a more optimal determination of process parameters necessary to achieve the desired recycling/processing result compared to less homogeneous granulates. As a nonlimiting example, the present method allows for production of granulates having different energy content when used as a fuel source. As another example, the present method allows for granulates resulting in more homogenous organic fractions if subjected to chemical and/or thermal recycling and thus more valuable end products. As yet another non-limiting example, the method allows for a more environmentally friendly recycling of wind turbine blades comprising e.g. PVC if the granulates are intended as a fuel source. Furthermore, if the granulate are to be use in a cement kiln process, there is a desire to avoid certain materials e.g. PVC, which may have a negative impact on the cement kiln efficiency and the final quality of the cement clinker. Thus, the present method also allows for production of granulates that are more suitable for use in cement production.

In some embodiments the granulate(s) may be separated based on their contents and particle size using cyclones and sieves. Such separation allows to further divide the granulates, such as the first, second, third, fourth, fifth and/or sixth granulate, into more homogenous fractions being suitable for different purposes. Typically, finer granulates will have a tendency to contain some individual granulates entirely or almost entirely consisting of resin whereas the coarser granulates will have a tendency to individually contain the same resin to fiber ratio as the wind turbine blade parts having been crushed.

In some embodiments, e.g. wherein one or more granulates (e.g. the first and/or second granulate) are subjected to chemical and/or thermal recycling, the method may further comprise mixing the first granulate or part thereof with the second granulate or part thereof, e.g. to obtain a mixed granulate having a tailored and/or predetermined relative amount of the primary and/or secondary material. The method may further comprise subjecting the mixed granulate to chemical and/or thermal recycling. This allows tuning of the material composition in the mixed granulate and thereby the composition of the organic fraction obtained after chemical and/or thermal recycling. In some embodiments, the mixed granulate may be used e.g. as a fuel source or in construction, e.g. as part of a cement matrix. This allows tuning of, e.g., the energy content of the mixed granulate, providing for a more reliable and predictable energy release when used. A wind turbine blade part may comprise a relative amount of the tertiary material. For example, the first wind turbine blade part may comprise a first relative amount of the tertiary material. The second wind turbine blade part may comprise a second relative amount of the tertiary material. The third wind turbine blade part may comprise a third relative amount of the tertiary material. The fourth wind turbine blade part may comprise a fourth relative amount of the tertiary material. The fifth wind turbine blade part may comprise a fifth relative amount of the tertiary material. The sixth wind turbine blade part may comprise a sixth relative amount of the tertiary material.

The first relative amount of the tertiary material may be different, e.g. larger or smaller, than the second, third, fourth, fifth and/or sixth relative amount of the tertiary material. The second relative amount of the tertiary material may be different, e.g. larger or smaller, than the first, third, fourth, fifth and/or sixth relative amount of the tertiary material. The third relative amount of the tertiary material may be different, e.g. larger or smaller, than the first, second, fourth, fifth and/or sixth relative amount of the tertiary material. The fourth relative amount of the tertiary material may be different, e.g. larger or smaller, than the first, second third, fifth and/or sixth relative amount of the tertiary material. The fifth relative amount of the tertiary material may be different, e.g. larger or smaller, than the first, second third, fourth and/or sixth relative amount of the tertiary material. The sixth relative amount of the tertiary material may be different, e.g. larger or smaller, than the first, second third, fourth, and/or fifth relative amount of the tertiary material.

In some embodiments the first wind turbine blade part comprises a first relative amount of the tertiary material, and the second wind turbine blade part comprises a second relative amount of the tertiary material. The first relative amount of the tertiary material may be different, e.g. larger, than the second relative amount of the tertiary material. As a non-limiting example, the first wind turbine blade part may be a spar cap comprising a first relative amount of a primary material e.g. glass fiber, a first relative amount of secondary material, e.g. polyester and a first relative amount of a tertiary material, e.g. carbon fiber, and the second wind turbine blade part may be an aft or bow panel comprising a second relative amount of the primary material, e.g. glass fiber, a second relative amount of the secondary material, e.g. polyester and a second relative amount of the tertiary material, e.g. carbon fiber. In some embodiments the first relative amount of the tertiary material is smaller than the second relative amount of the tertiary material. In other exemplary embodiments, the first relative amount of the tertiary material is larger than the second relative amount of the tertiary material.

A wind turbine blade part may comprise a relative amount of the quaternary material. For example, the first wind turbine blade part may comprise a first relative amount of the quaternary material. The second wind turbine blade part may comprise a second relative amount of the quaternary material. The third wind turbine blade part may comprise a third relative amount of the quaternary material. The fourth wind turbine blade part may comprise a fourth relative amount of the quaternary material. The fifth wind turbine blade part may comprise a fifth relative amount of the quaternary material. The sixth wind turbine blade part may comprise a sixth relative amount of the quaternary material.

The first relative amount of the quaternary material may be different, e.g. larger or smaller, than the second, third, fourth, fifth and/or sixth relative amount of the quaternary material. The second relative amount of the quaternary material may be different, e.g. larger or smaller, than the first, third, fourth, fifth and/or sixth relative amount of the quaternary material. The third relative amount of the quaternary material may be different, e.g. larger or smaller, than the first, second, fourth, fifth and/or sixth relative amount of the quaternary material. The fourth relative amount of the quaternary material may be different, e.g. larger or smaller, than the first, second third, fifth and/or sixth relative amount of the quaternary material. The fifth relative amount of the quaternary material may be different, e.g. larger or smaller, than the first, second third, fourth and/or sixth relative amount of the quaternary material. The sixth relative amount of the quaternary material may be different, e.g. larger or smaller, than the first, second third, fourth, and/or fifth relative amount of the quaternary material.

In some embodiments the second wind turbine blade part, e.g. being a bow panel, comprises a second relative amount of the quaternary material, e.g. being a core material, and the fourth wind turbine blade part, e.g. being a shear web, comprises a fourth relative amount of the quaternary material. The second relative amount of the quaternary material may be larger than the fourth relative amount of the quaternary material. As a non-limiting example, the second wind turbine blade part may be a bow panel comprising a second relative amount of the primary material, e.g. glass fiber, a second relative amount of the secondary material, e.g. polyester, a second relative amount of the tertiary material, e.g. carbon fiber, and a second relative amount of the quaternary material, e.g. PET foam, and the fourth wind turbine blade part may be a shear web comprising a fourth relative amount of the primary material, e.g. glass fiber, a fourth relative amount of the secondary material, e.g. polyester, a fourth relative amount of the tertiary material, e.g. carbon fiber, and a fourth relative amount of the quaternary material, e.g. PET foam. In some embodiments the second relative amount of the quaternary material is smaller than the fourth relative amount of the quaternary material. In other exemplary embodiments, the second relative amount of the tertiary material is larger than the fourth relative amount of the tertiary material.

A wind turbine blade part may comprise a relative amount of the quinary material. For example, the first wind turbine blade part may comprise a first relative amount of the quinary material. The second wind turbine blade part may comprise a second relative amount of the quinary material. The third wind turbine blade part may comprise a third relative amount of the quinary material. The fourth wind turbine blade part may comprise a fourth relative amount of the quinary material. The fifth wind turbine blade part may comprise a fifth relative amount of the quinary material. The sixth wind turbine blade part may comprise a sixth relative amount of the quinary material.

The first relative amount of the quinary material may be different, e.g. larger or smaller, than the second, third, fourth, fifth and/or sixth relative amount of the quinary material. The second relative amount of the quinary material may be different, e.g. larger or smaller, than the first, third, fourth, fifth and/or sixth relative amount of the quinary material. The third relative amount of the quinary material may be different, e.g. larger or smaller, than the first, second, fourth, fifth and/or sixth relative amount of the quinary material. The fourth relative amount of the quinary material may be different, e.g. larger or smaller, than the first, second third, fifth and/or sixth relative amount of the quinary material. The fifth relative amount of the quinary material may be different, e.g. larger or smaller, than the first, second third, fourth and/or sixth relative amount of the quinary material. The sixth relative amount of the quinary material may be different, e.g. larger or smaller, than the first, second third, fourth, and/or fifth relative amount of the quinary material.

A wind turbine blade part may comprise a relative amount of the senary material. For example, the first wind turbine blade part may comprise a first relative amount of the senary material. The second wind turbine blade part may comprise a second relative amount of the senary material. The third wind turbine blade part may comprise a third relative amount of the senary material. The fourth wind turbine blade part may comprise a fourth relative amount of the senary material. The fifth wind turbine blade part may comprise a fifth relative amount of the senary material. The sixth wind turbine blade part may comprise a sixth relative amount of the senary material.

The first relative amount of the senary material may be different, e.g. larger or smaller, than the second, third, fourth, fifth and/or sixth relative amount of the senary material. The second relative amount of the senary material may be different, e.g. larger or smaller, than the first, third, fourth, fifth and/or sixth relative amount of the senary material. The third relative amount of the senary material may be different, e.g. larger or smaller, than the first, second, fourth, fifth and/or sixth relative amount of the senary material. The fourth relative amount of the senary material may be different, e.g. larger or smaller, than the first, second third, fifth and/or sixth relative amount of the senary material. The fifth relative amount of the senary material may be different, e.g. larger or smaller, than the first, second third, fourth and/or sixth relative amount of the senary material. The sixth relative amount of the senary material may be different, e.g. larger or smaller, than the first, second third, fourth, and/or fifth relative amount of the senary material.

In the present context a relative amount of a material, e.g. the primary, secondary, tertiary, quaternary, quinary and/or senary material, in one of the plurality of wind turbine blade parts, e.g. the first, second, third, fourth, fifth and/or sixth wind turbine blade part, should be understood as the weight percent (w/w %) of the respective material compared to the total weight of the respective wind turbine blade part.

In some embodiments, one or more of the wind turbine blade parts, such as the first, second, and/or third wind turbine blade parts may comprise less than a threshold amount, e.g. less than 20%, less than 10%, less than 5%, or less than 1%, by weight, of a sandwich core material, e.g. including balsa wood, polyethylene (PET) foam, or polyvinylchloride (PVC) foam. Another of the one or more of the wind turbine blade parts, such as another of the first, second and/or third wind turbine blade parts may comprise more than a second threshold amount of sandwich core material, such as more than 10%, more than 20%, or more than 30 %, by weight, of the sandwich core material.

In some embodiments, one or more of the wind turbine blade parts, such as the first, second and/or third wind turbine blade parts may comprise less than a threshold amount, e.g. less than 30%, less than 20%, less than 10%, less than 5%, less than 2%, or less than 1%, by weight, of hardened glue, e.g. including a polyurethane glue or epoxy glue. Another of the one or more of the wind turbine blade parts, such as another of the first, second and/or third wind turbine blade parts may comprise more than a second threshold amount of hardened glue, such as more than 10%, more than 20%, or more than 25 %, by weight, of hardened glue.

The exemplified embodiments are not intended to be limiting in anyway and the skilled person will be aware of alternative setups while still being within the spirit of the disclosure. It follows that any feature of one aspect or embodiment of the disclosure apply equally to any other aspect or embodiment of the disclosure.

Embodiments of the disclosure will be described in the following with regard to the accompanying figures. Like reference numerals refer to like elements throughout. Like elements may, thus, not be described in detail with respect to the description of each figure. The figures show one way of implementing the present disclosure and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

Fig. 1 illustrates a conventional modern upwind wind turbine 21 according to the so-called "Danish concept" with a tower 22, a nacelle 23 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8. Typically, such a wind turbine may be operating for 20-25 years, after which the wind turbine 21 may be disassembled into a plurality of individual components, e.g. the tower 22, the nacelle 23, the hub 8, and the blades 10.

Fig. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade with a root end 17 and a tip end 15 and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

The wind turbine blade 10 comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part 24 and a second blade shell part 26, typically made of fiber-reinforced polymer. The wind turbine blade 10 may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part 24 is typically a pressure side or upwind blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together with adhesive, such as glue, along bond lines or glue joints 28 extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 has a semi-circular or semi-oval outer cross-sectional shape.

Fig. 3 is a schematic diagram illustrating an exemplary wind turbine blade illustrating the upper and lower half-shells and their different layers and components. The surface coating 100 is the outer layer of the wind turbine blade and typically consists of a polymer such as polyester or polyurethane. The surface structure 101 below the surface coating 100 is typically a multiaxial fiber laminate comprising reinforcement fibers such as glass, carbon or hybrid fibers embedded in a polymer matrix made from a cured resin such as an epoxy resin, vinylester or polyester resin. A sandwich core 102 in the bow or aft panel is typically made of a light material such as balsa wood or a PET or PVC foam to lower the overall weight of the blade. A spar cap 103 is located between the aft and bow panels and is a thick layer of fiber reinforced laminate providing the wind turbine blade with its bending strength. The spar cap 103 typically comprise unidirectional fibers such as glass, carbon or hybrid fibers embedded in a polymer matrix made from a cured resin such as an epoxy resin, vinylester or polyester resin. Shears webs 104 connects the spar caps of the upper and lower half-shell and provides stiffness to the blade by transferring shear forces between the spar caps of the half shells. Typically, the shear webs 104 are also made in a sandwich construction from the root and along most of the blade length with a sandwich core of a light material and an outer layer of multiaxial fiber laminate comprising reinforcement fibers such as glass, carbon or hybrid fibers embedded in a polymer matrix made from a cured resin such as an epoxy resin, vinylester or polyester resin. A down conductor 105 of a lightning protection system for the wind turbine blade is also illustrated.

Also illustrated are various components of the root section of the blade. More particular, the root section of the illustrated wind turbine blade comprises a root flange 108 and root inserts 107 for connecting the wind turbine blade to the hub of the wind turbine. Furthermore, the root section comprises a bulkhead 106 with a door providing a separating wall to the interior of the blade.

Fig. 4 is a schematic diagram illustrating a cross-section of an exemplary wind turbine blade composed of different wind turbine blade parts and suitable for the method disclosed herein. The cross section shows the leading edge 109, the bow panels 110, the spar caps 111, the aft panels 112, the trailing edge 113 and the shear webs 114. The method disclosed herein involves sectioning the wind turbine blade comprising a plurality of materials into a plurality of wind turbine blade parts comprising a first wind turbine blade part, e.g. the spar cap 111, and a second wind turbine blade part, e.g. the bow panel 110, such that the first wind turbine blade part comprises a first relative amount of a primary material, e.g. glass fiber, and a first relative amount of a secondary material, e.g. polymer matrix, and the second wind turbine blade part comprises a second relative amount of the primary material and a second relative amount of the secondary material. As in the illustrated example, when sectioning the wind turbine blade according to the components of the wind turbine blade, the first relative amount of the primary material may be larger than the second relative amount of the primary material, and/or the second relative amount of the secondary material may be larger than the first relative amount of the secondary material, and more uniform or predictable material compositions may be obtained and provided for further processing.

The blade may be sectioned into even more wind turbine blade parts such as including a third, a fourth, a fifth and/or a sixth wind turbine blade part depending on type of material and/or the material composition in the individual parts. For example, as illustrated in Fig. 4 the wind turbine blade may be sectioned along the span of the blade into a first wind turbine blade part comprising the spar cap(s) 111, a second wind turbine blade part comprising the bow panel(s) 110, a third wind turbine blade part comprising the aft panel(s) 112, a fourth wind turbine blade part comprising the shear web(s) 114, a fifth wind turbine blade part comprising the leading edge 109 and trailing edge 113 of the blade and a sixth wind turbine blade part comprising the root section (see Fig. 3) of the blade. Thus, in a preferred embodiment, the first wind turbine blade part is a spar cap, the second wind turbine blade part is a bow panel, the third wind turbine blade part is an aft panel, the fourth wind turbine blade part is a shear web, the fifth wind turbine blade part is a trailing edge part of the blade or a leading edge part of the blade and the sixth wind turbine blade part is a root section of the blade.

Fig. 5 is a schematic diagram illustrating the crushing and grinding of individual wind turbine blade parts separately to obtain more homogeneous granulates in terms of material type (e.g. primary, secondary, tertiary, quaternary, quinary, senary material) or material composition (i.e. relative content of e.g. the primary material, the secondary material etc.). For example, as schematically illustrated in Fig. 5, a first wind turbine blade part 117, a second wind turbine blade part 118, a third wind turbine blade part 119 and a fourth wind turbine blade part 120 may be subjected separately to crushing/shredding in respective crushers/grinders 116 to obtain a first granulate 121, a second granulate 122, a third granulate 123 and a fourth granulate 124.

The disclosure has been described with reference to a preferred embodiment. Flowever, the scope of the invention is not limited to the illustrated embodiment, and alterations and modifications can be carried out without deviating from the scope of the invention.

Throughout the description, the use of the terms "first", "second", "third", "fourth", "primary", "secondary", "tertiary" etc. does not imply any particular order or importance, but are included to identify individual elements. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa. LIST OF REFERENCES

8 hub

10 blade

12 blade part

14 blade tip

16 blade root

17 root end

18 leading edge

20 trailing edge

21 wind turbine

22 tower

23 nacelle

24 first blade shell part (pressure side)

26 second blade shell part (suction side)

28 bond lines/glue joints

30 root region

32 transition region

34 airfoil region

40 shoulder

100 Surface coating

101 Surface structure

102 Sandwich core

103 Spar cap

104 Shear web

105 Down conductor

106 Bulkhead

107 Root inserts

108 Root flange

109 Leading edge of the blade

110 Bow panel

111 Spar cap

112 Aft panel

113 Trailing edge of the blade

114 Shear web

115 Saw

116 Shredder/Grinder 117 First wind turbine blade part

118 Second wind turbine blade part

119 Third wind turbine blade part

120 Fourth wind turbine blade part 121 First granulate

122 Second granulate

123 Third granulate

124 Fourth granulate