ReusaBlade:
Recyclable wind-turbine rotor blades by means of detachable resin systems and reutilization of the recyclate material segregated by type

Project start / December 01, 2023

There are already more than 30,000 wind turbines in Germany. By 2030, there could be more than twice as many. A wind turbine is usable for around 20 to 30 years and must then be disposed of. The tower made from steel and concrete is already very easy to recycle, but the rotor blades have not been up until now. They consist of complex multi-material composites – firmly bonded by thermoset resins. One promising approach: With the aid of detachable resin systems, rotor blades could be constructed in such a way that the materials can be separated by type at the end of the service life. In collaboration with research and industry partners, we are developing industrially feasible production, separation and processing procedures for this purpose. The focus of the Fraunhofer WKI lies in the processing and reutilization of recovered glass fibers and balsa-wood components. As a result, we are helping to ensure that a high-quality reutilization of 100 percent of the wind-turbine materials is possible at the end of their service life.

The photo shows, lying next to one another: a small piece of white glass-fiber fabric, and balsa-wood blocks that are embedded in a greenish plastic layer. — © Fraunhofer WKI | Manuela Lingnau
Balsa wood and glass-fiber-reinforced plastic: these and other valuable raw materials make wind-turbine rotor blades light and highly stable. In the future, detachable resin systems should enable the recovery of materials segregated by type.

In wind turbines that have already been erected, the rotor blades are made of fiber-reinforced plastics with thermoset, non-detachable resin systems. For these blades, suitable recycling processes must be developed. Numerous research projects are therefore already in progress or are currently being implemented.

The “ReusaBlade” project, in contrast, is focusing on recycling paths for rotor blades that will be built in the coming years. With the aid of new, detachable epoxy resins, material-separation strategies are to be developed and tested in order to enable a multiple reutilization of rotor-blade materials. As a result, the high-quality recycling of rotor blades should become simpler, more energy-efficient and more economical in the future.

The diagram shows a wind turbine, a rotor blade in an acid bath (solvolysis), and the recovered material fractions: balsa wood, glass fibers, CFRP profiles, PET foam, and resin dissolved in acid. — © Fraunhofer WKI
At the Fraunhofer WKI, the recovered fiberglass mats and balsa-wood components are prepared for high-quality subsequent utilization.

Recovery of the material components of the rotor blades

Sample production and combination of various materials for the production of a rotor-blade transition segment
- Laminates made from glass-fiber-reinforced plastic (GRP)
- Molded sandwich panels (surface layer made from GRP laminate, core made from PET foam and balsa wood)
- Integration of a main belt made from prefabricated carbon-fiber-reinforced plastic profiles, produced using the pultrusion process (pultruded CFRP)
Tests regarding the dissolution of the fiber-matrix bond by means of solvolysis at the material level (coupons) and component level
Tests regarding the handling of the recovered materials (recyclates) and quality testing (glass fibers, balsa wood, PET foam, pultruded CFRP)
Tests regarding the optimization of recyclate quality at a simultaneously high material throughput through adaptation of the solvolysis process parameters
Tests regarding the usability of the solvolysis liquid (acid) and the epoxy resin dissolved therein

Reutilization of recovered fiberglass mats and core materials in applications with lower mechanical requirements

Testing and processing of the recovered fiberglass mats and core materials (balsa wood, PET foam)
Sample production, testing and modeling of new laminate and sandwich materials made from the recovered materials and new resin at the coupon level

Fiber-reinforced plastics with glass-fiber recyclates:

The recovered fiberglass mats are potentially suitable for the manufacture of fiber-reinforced plastics for applications with lower strength requirements. Examples include:

Non-load-bearing components in the production of wind-turbine rotor blades, such as lightning-rod mounts, or the partition wall in the hub area of the blade (“bulkhead”) that is necessary for maintenance and occupational-safety reasons on large rotor blades
Constructions in boat-building

Balsa-wood recyclate:

The recyclability of the recovered balsa wood depends, firstly, on whether the resin between the balsa blocks also dissolves during the solvolysis process or whether this bonding of the blocks is retained. The second decisive factor is the extent to which the wood constituents (lignin, hemicellulose, cellulose) are degraded by the solvolysis process. Depending on the balsa-wood recyclates that can be attained, various new products can be manufactured through processing and further refinement steps. The following would, for example, be conceivable:

Reutilization as core material in rotor blades
Lightweight-construction sandwich elements, such as for building elements, vehicle components, surfboards/stand-up paddleboards, etc.
Wood-based materials for lightweight construction
Transparent wood
Highly compacted wood that achieves high strengths without the addition of adhesives

PET-foam recyclate:

The recovered PET-foam elements could be processed both mechanically and chemically and transformed into new products. Both methods are being investigated in the project.

Reutilization of pultruded CFRP profiles as components subject to high structural loads

The CFRP profiles prefabricated using the pultrusion process are detached from the overall material composite (rotor-blade component) by means of the solvolysis process. The fiber-matrix bond within the profiles is, however, thereby retained due to the fact that the CFRP profiles are manufactured using non-detachable resins. Despite the high fatigue loading caused by the operation of the rotor blades, the profiles nevertheless exhibit high residual strengths. This makes them particularly attractive for reutilization.

Processing of the recovered CFRP profiles (in particular surface modification)
Production and testing of double-lap shear-test components for evaluation of the mechanical performance capabilities

In the ideal case, the CFRP profiles can be reused for rotor-blade production. Alternatively, other fields of application can be considered.

Industrial feasibility study | Up-scaling

Within the framework of the project, a comprehensive analysis and evaluation of the developed recycling processes is being conducted.

Cost analysis of treatment processes for the rotor-blade elements with regard to personnel deployment, logistics, energy demand, chemicals disposal, occupational safety, etc.
Process-parameter studies for the dissolution and recovery of the resin
Life cycle analysis (LCA) for the differing treatments of the PET foam
Determination of total process costs

On this basis, recommendations for action regarding the implementation of the recycling process chain on an industrial scale can be proposed.

Last modified: December 01, 2023

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Our contribution

Project contribution provided by the Fraunhofer WKI

Sub-project (collaboration)

Production and testing of rotor-blade components (before and after solvolysis), and processing of the materials

Main tasks

Management of the “Processing of the recycled material fractions” work package
Processing of the recovered glass fibers (fabric configuration and sizing), including microscopic inspections and evaluation of the mechanical properties
Processing of the recovered balsa wood and evaluation of the mechanical properties and emission behavior

In rotor blades, the balsa wood is present in the form of small blocks. This is due to the fact that if a high compressive strength is required of wood, it has to be sawn out of the trunk at right angles to the grain. In order to achieve the shape of a hollow wind-turbine rotor blade, the balsa-wood trunk discs are cut into small blocks and assembled into flat molded parts (shells). The end-grain side thereby faces outwards – as with end-grain parquet. Fiberglass mats are then glued onto both (end-grain) sides of the balsa-wood shells using epoxy resin. Balsa wood is highly absorbent, particularly on the end-grain side. During the gluing of the fiberglass mats, large amounts of resin penetrate into the wood. During the solvolysis, a large proportion of the solvolysis liquid (acid) is absorbed by the wood in order to dissolve the resin. Possible consequences include:

The wood fibers could be damaged. This would result in a mechanical weakening of the wood.
Acids could be stored in the wood. If this leads to health-critical emissions and/or odors (e.g. in the case of acetic acid), the reutilization of the balsa wood for indoor applications could be severely restricted.

Our goal is to optimize the recovery and processing procedures for glass fibers and balsa wood in order to enable subsequent utilization of the highest possible quality.

Potential follow-up developments

Currently, thermosets are rarely used in combination with wood due to the fact that they restrict the recyclability of the wood-based end product. In the “ReusaBlade” project, a process is being developed that allows thermoset-bound wood-hybrid components from rotor blades to be disassembled into individual materials. In an adapted form, this process could be transferred to diverse wood-based components. As a result, the range of applications for thermoset resins in the wood industry could be significantly expanded – for example for the production of recyclable, wood-based components in the construction industry, automotive industry or furniture industry.

We can help you to drive forward innovation!

We develop not only recycling processes for wind-turbine rotor blades, but also complete material and component solutions as well as the associated production and recycling processes for virtually every sector. Our particular expertise lies in solutions based on renewable raw materials, biogenic residues and recycled materials, as well as hybrid multi-material systems. With our materials and component testing, certification services and our involvement in standardization committees, we can assist you in making sustainable material and product innovations marketable.

In the field of wind energy, we are working intensively on the question of how wind turbines can be built more sustainably in the future. Current examples include:

Take advantage of our extensive experience and our wide range of services. As a competent research and development partner, we would be delighted to assist you – from raw materials through to the end product.

Project relevance

Economy and labor market

Wind energy plays a major role in the expansion of renewable energies and the future viability of the German economy:

	Number of wind turbines	Total output
	Status 2023	STATUS 2023	Planned for 2030
Onshore	approx. 30,000	61 gigawatts (GW)	115 gigawatts (GW)
Offshore	approx. 1,600	8.5 gigawatts (GW)	30 gigawatts (GW)

The quantity of wind turbines in 2030 depends on the size (output) of the individual wind turbines. One thing is certain: thousands of additional wind turbines will be erected.
Of the 30,000 onshore turbines currently in operation, around one third are more than 20 years old.
The German Environment Agency predicts that at least 400,000 metric tonnes of fiber-reinforced plastic waste from rotor blades will be generated by 2040.

Through the “ReusaBlade” project, we are helping to ensure that valuable raw materials from wind-turbine rotor blades can be reutilized industrially.

Potential advantages for the wind industry

Fulfilment of increasingly stringent legal requirements regarding the recyclability of wind turbines
Increase in sales prices for disused rotor blades as a high-quality source of raw materials
New construction of wind turbines: Increased independence from finite raw materials, petrochemical products and global supply chains thanks to the use of fiber-reinforced plastics made from rotor-blade recyclates
Cost reductions

Potential advantages for dependent sectors

Through the strengthening of the wind-power industry, companies in dependent sectors could expand their business fields and sales markets. Examples include:

Chemical industry: recyclable resin systems, new materials made from PET-foam recyclate
Plant engineering/energy technology: production and maintenance of solvolysis plants
Materials industry: new wood-based materials and hybrid materials made from recyclates (balsa wood, glass fibers, PET foam, resin)
End-product manufacturers (construction industry, automotive industry, sports-equipment industry, etc.): sustainable products made from recycled wind-turbine rotor blades

Furthermore, the potential cost reductions in the wind industry could have a positive effect on electricity prices. Companies from all sectors could benefit from this.

Potential advantages for end users

A favorable electricity price development could benefit end users in many ways, both directly and indirectly. Examples include:

Less expensive household electricity
Creation of affordable housing with climate-friendly heating systems (e.g. heat pumps)
Affordability of climate-friendly electromobility
General stabilization of consumer prices

Potential advantages for employees

By strengthening the domestic energy industry, the project provides a contribution towards the creation of sustainable and meaningful jobs in Germany. According to a study, more than 387,000 people were working in this sector in 2022. The increase compared to 2021 is almost 15 percent and has resulted in the highest level of employment since 2012.

Protection of indigenous people in balsa-tree cultivation areas

Balsa wood is an excellent lightweight-construction material and is therefore in high demand on the world market. Balsa trees grow in tropical areas – for example in Ecuador. In order to no longer be dependent on wild balsa trees, the indigenous people are increasingly being encouraged to plant balsa wood. According to research carried out by the environmental organization WWF, this endangers the food security of the indigenous people and incites social conflict.

The “ReusaBlade” project provides a contribution towards reducing the demand for new balsa wood.

Energy efficiency and renewable energies

The project provides a contribution towards exploiting the potential for energy savings and increasing the share of renewable energies.

Energy-efficient production of wind turbines

Savings in transportation energy: Reduction of crude-oil demand through material reutilization of rotor blades
Savings in production energy: Potentially more energy-efficient production of rotor blades from recyclates (compared to production from materials that are petrochemically produced from crude oil)

Renewable energies

Increase in the economic efficiency of wind turbines through an efficient recycling solution for rotor-blade materials

Environmental and climate protection

The project provides a contribution towards the preservation of the basis of mankind’s existence and the avoidance of greenhouse-gas emissions.

Climate change: Avoidance of energy-related CO₂ emissions
Reduction in the demand for crude oil and the associated environmental destruction
Reduction in the demand for balsa wood (tropical wood) and the associated deforestation of the rainforest and the creation of monocultures

Health protection

The project provides a contribution towards the protection of human health.

Through the expansion of wind energy, health impacts and deaths resulting from climate change and the destruction of livelihoods will be reduced. Examples include:

Effects of extreme weather events and their consequences (e.g. heat, flooding, storms, crop failures, forest fires)
Effects of pollution in air and environment (e.g. respiratory diseases, poisoning, exposure to microplastics)
Effects of a loss of biodiversity (e.g. threats to food security, increase in zoonoses and pandemics)

Contribution to the Sustainable Development Goals

SDG 7 SDG 8 SDG 9 SDG 11 SDG 12 SDG 13

Project partners

Sub-project	Title	Partner
1	Manufacturing and testing of rotor-blade components, before and after solvolysis, as well as the preparation of the materials	Fraunhofer IWES (coordination), Fraunhofer WKI
2	Matrix dissolution as a practical application	BAC Entsorgungswirtschaft GmbH
3	Chemical recycling of PET-based core materials of rotor blades from wind turbines by means of the revolPET® process.	RITTEC 8.0 Umwelttechnik GmbH

Associated partners

Partner	Tasks
CTP Advanced Materials GmbH	Provision of non-soluble resins, solvolysis experiments, processing of the dissolved resin, advice on the handling of resins
Owens Corning Fiberglas D GmbH	Provision of glass fibers, surface modification of recyclate glass fibers, advice on the handling of recyclate glass fibers
BYK-Chemie GmbH	Provision of chemicals for surface reactivation, advice on the application and handling of the chemicals
Gurit UK Limited	Provision of PET foams, investigation of the recyclability of recyclate PET foams, advice on the handling of PET foams
Siemens Gamesa Renewable Energy A/S	Construction, testing and characterization of fiber-composite samples and rotor-blade components

Funding

Official project title: Recyclingfähige Materialien für Rotorblätter und deren Wiederverwertung

(Recyclable materials for rotor blades and their reutilization)

Funding body: German Federal Ministry for Economic Affairs and Climate Action (BMWK)

Project management: Project Management Jülich (PtJ)

Funding reference (Sub-project 1): 03EE3095A

Duration: 1.12.2023 to 30.11.2026