From rotor blade to material

The expansion of wind energy is a key component of the energy transition. At the same time, as the dismantling of end-of-life turbines increases, a new challenge is coming into focus: what to do with the huge rotor blades made of fibre-reinforced composites? Whilst metals, concrete and electrical components follow established recycling pathways, the recycling of rotor blades presents a particularly demanding task in terms of materials technology. They consist predominantly of glass fibre-reinforced (GFRP) and carbon fibre-reinforced (CFRP) plastics – materials offering high performance in lightweight construction, but with limited material recyclability. The team at the Steinbeis Innovation Center Applied Product and Process Development (IPP) has recognised this challenge and has been working intensively on the utilisation of GFRP-containing waste.

The decommissioning of older wind turbines in Germany is leading to a steadily growing volume of rotor blade waste. Forecasts by the German Environment Agency estimate that the quantities generated will reach up to 20,000 tonnes per year as early as the 2020s; a further significant increase is expected for the 2030s. This trend is driven by many turbines reaching the end of their service life, additional decommissioning volumes resulting from repowering, and the high proportion of fibre-reinforced composites in the rotor blades. At the same time, regulatory frameworks – in particular the ban on landfilling GRP and the limited alternatives for energy recovery – are exacerbating the disposal situation. The management of rotor blade waste is thus increasingly becoming a challenge across the entire wind energy value chain.

Furthermore, the heterogeneity of materials, different construction methods for rotor blades, and varying dismantling and processing procedures complicate the standardisation of recycling pathways. This has so far limited the scalability of potential solutions and underscores the need for reproducible, process-reliable approaches.

Existing recovery processes are reaching their limits

While established recycling processes exist for most wind turbine components, this is not yet the case for rotor blades to the same extent. Processing is limited by high technical complexity, low recycled material values and a lack of economic scalability. Whilst CFRP can primarily be treated via solvolysis, this is only possible at limited capacity. GRP is predominantly co-incinerated in cement plants; high-quality material recycling pathways are currently lacking. Furthermore, mechanical shredding and grinding processes produce wet, sludgy residues which, due to their high moisture content, often have to be disposed of as hazardous waste. Key potential for resource utilisation thus remains untapped.

To make matters worse, reliable criteria for assessing the material quality from recycling processes are currently lacking. Without defined parameters for fibre lengths, matrix properties or contamination levels, reproducible reuse in industrial applications is only possible to a limited extent.

This gives rise to a complex web of material-related, process-related and economic challenges:

• Resource efficiency in industry and the energy sector requires material recycling pathways for fibre-reinforced composites.
• Hazardous waste from processes involving GRP must be reduced.
• Industrial innovation capacity is linked to the development of new, economically viable material systems.
• Sustainable composites require impetus beyond purely thermal recovery.
• A functioning circular economy demands the establishment of new material recycling loops.

A new materials-based approach

This is precisely where the Steinbeis development team from Dresden comes in. The project is pursuing a materials-based approach to the recycling of waste containing GRP. The focus is on grinding dust from industrial GRP processing. These are characterised by a known material composition, high homogeneity and the absence of foreign substances – properties that enable reliable further processing. On this basis, a thermosetting plastic matrix is being developed into which the grinding dust is incorporated as a filler. The aim is to establish a material recycling pathway as an alternative to the energy recovery methods that have dominated to date. Following successful process validation, the transferability to rotor blade waste will be tested.

Methodologically, the development team at the Steinbeis Innovation Center Applied Product and Process Development (IPP) follows a transfer-oriented development approach. Material characterisation, process window definition and component manufacturing are systematically integrated. In this way, robust and industrially scalable process chains are created from laboratory-based findings.

The focus is on translating material-related developments into application-oriented processes and on assessing industrial feasibility. “The aim is not to limit the developed material systems to the laboratory scale, but to make them integrable into existing manufacturing and process chains,” summarises Ronny Wagler, who heads the Steinbeis Innovation Center in Dresden.

Sustainability with prospects

The GRP composites developed are based on sustainable thermosetting binder systems. The grinding dust is processed as a filler into lightweight structural profiles that can be used, for example, in mechanical and plant engineering. The aim is to achieve material properties on a par with conventional GRP materials – particularly in terms of thermal stability, weather and chemical resistance, elasticity and processability.

Looking ahead, this approach opens up the possibility of integrating further fibre composite waste streams – such as those from boat building, construction products or pipe and container manufacturing – into comparable material cycles. The potential thus extends far beyond the specific application of wind energy.