Fibre composite materials or fibre-reinforced plastics are a combination of different materials in a composite material structure. The advantages of a fibre-reinforced structure are so decisive that such structures absolutely dominate in nature.

Fibre composite materials made of carbon fibres (CFRP) and glass fibres (GFRP) are used particularly due to their very high performance, low weight, and resistance to external influences. Consequently, they can significantly contribute to reducing resource consumption and increasing economic strength.

Ultimately, the exact specification of a fibre composite material depends on the material. For example, carbon concrete is a composite material made of concrete and non-metallic carbon reinforcement. The reinforcement, in turn, consists of a carbon-based fibre, sizing, and impregnation. Crucially, the reinforcement is executed in mat, grid, or rod form, while short fibres mixed into the concrete are not considered part of carbon concrete.

Fibre composite materials are finding increasingly new applications in all areas of life, both in the Federal Republic of Germany and worldwide. The spectrum ranges from ultra-light eyeglass frames to household and leisure equipment, to applications in wind power energy, automotive, ship, aerospace, and space industries, as well as mechanical and plant engineering. Additional applications include semi-finished products (reinforcements, etc.) in building construction, civil engineering, and structural engineering.

New fibres – such as carbon fibre – are typically manufactured from petroleum. Additionally, more and more alternative approaches to their production are emerging in the market, such as algal biomass-based, lignin-based, or polyethylene-based carbon fibres and carbon dioxide capture from the air. These are mostly continuous fibres that are cut to length depending on their use.

In contrast, recycled fibres are either reintroduced into the material cycle from production-side carbon fibre-containing waste or application-related waste after the end of the use phase. The reprocessed materials, as staple and short fibres, represent high-quality secondary raw materials. Compared to new fibres, their performance remains so high that recycled fibres can also be used to manufacture new high-quality products (body parts for the automotive industry, mat and rod-shaped reinforcements for concrete construction, etc.), instead of having to be landfilled or subjected to thermal recovery.

If components of fibre composite materials cannot be directly reused, fibre-containing waste is generated. Waste from fibre composite materials is not only generated at the end of their service life but already during the production of fibres and yarns, during the manufacture of semi-finished products, and the fibre composite materials themselves.

A functional circular and resource economy requires widespread establishment of applications using these high-quality fibre-containing secondary raw materials. This requires, on one hand, expanding the technical and organisational processes for comprehensive material recycling of fibre-containing fractions, as is the case for metallic materials. On the other hand, additional marketable products from recycled fibres need to be offered.

For this reason, a circular and resource economy for fibre composite materials is being developed in the “Elbe Valley Saxony” region. This approach strengthens local development opportunities by completing existing processes of circular value chains and initiating new developments, rather than outsourcing them from the “Elbe Valley Saxony” region. This regionally improves (economic) resilience and variability and creates long-term perspectives for growth and employment.

The reintroduction of fibre composite materials in the form of recycled fibres along a circular economy can occur in different ways. All three techniques offer an opportunity to reduce both resource use and fibre-containing waste.

Corresponding processes can lead to restoration (recycling), improvement (upcycling), or reduction (downcycling) of the quality, potential for future applications, and economic value of individual raw materials. In the case of fibre composite materials, it is currently mostly downcycling, which is primarily due to the mechanical, chemical, and/or thermal stress on the individual components.

Given that fibre composite materials are used in different industries and applications, the recycling of fibre-containing waste mostly occurs via an open-loop approach. In this process, the individual components of a product are transferred from one system to another, or the recovered secondary raw materials are used for manufacturing other products. In contrast, with the closed-loop approach, the recovered secondary raw materials are returned to their original application.

Concrete is the most commonly used building material worldwide for constructing housing and infrastructure, with a large portion intended for reinforced concrete construction. However, both in the Federal Republic of Germany and worldwide, non-metallic reinforcements are increasingly being used in concrete construction. For the use of carbon concrete – a composite material made of concrete and carbon reinforcement – recycled fibres could also be considered for manufacturing mat-shaped, grid-shaped, or rod-shaped reinforcement.

Given that currently, the quality of recycled fibres usually does not (yet) match the quality of new fibres, the use of recycled fibres is challenging for market-relevant applications with the highest performance requirements (aerospace, etc.) or optical and tactile requirements (automotive and leisure industry, etc.). In contrast, the requirement profile in construction – while maintaining all safety-relevant parameters – is comparatively low. Through the reintegration of fibre-containing waste in building components and structures, it is already possible today to

• compensate for lower performance by initially providing a larger safety factor. The special feature is that the cross-section of the reinforcement is still so small that this approach will not affect construction and design.
• disregard the lower quality of appearance and feel, as these do not play a role in concrete construction.
• reduce the amount of required resources and fibre-containing waste from different industries.
• maintain the CO₂ previously bound in carbon fibres within reinforcements made from recycled fibres.

In a circular and resource economy, only comprehensive digitalisation can transparently map the entire life cycle of a product, from raw material extraction to end of life. Only when it is known when, where, and how much fibre-containing waste is generated can effective measures be developed to comprehensively collect and sort fibre composite materials and appropriately reuse or repurpose them. Consequently, digitalisation should be understood as a direct tool for building the intended circular material cycle for fibre composite materials.

While traditional waste management deals with materials that no longer serve an immediate purpose after production or consumption, recycling-compatible construction or design for recycling creates the prerequisite for circular economics. Rules and framework conditions should ensure that requirements for later disposal and recycling are considered even before a product’s manufacture and use. Ultimately, a product should be able to be disassembled into its (materially uniform) original components or even converted back into raw materials without significant effort. Against the background of (easily) separable connections and the use of as few different materials as possible, along with high stability, a product should ultimately be durable, easily repairable, and regenerable.

Fibre composite materials made from recycled fibres are already recyclable with today’s conventional facilities.

Three basic approaches are available for material recycling: mechanical, solvent-based, and chemical processes (solvolysis and pyrolysis). The quality of recycled fibres depends not only on the processes used but also on the technical equipment and its technological maturity (Technology Readiness Level; TRL), the effectiveness and efficiency of all processes, the purity of the input or added material, and costs. This includes the fact that repeatedly recycled fibres can affect quality, particularly the length of individual fibres.

Regarding carbon concrete construction, up to 98% of carbon reinforcement from demolished and broken-down materials can also be recovered using today’s conventional facilities. For the material recycling of recovered carbon fibres, if necessary, the plastic matrix of the impregnation is removed from the carbon fibre. For this purpose, the fibre structures to be cleaned are subjected to a pyrolysis or solvolysis process. Carbon concrete that exists in heterogeneous material mixtures and cannot be provided pure and free of foreign materials during collection and sorting must be separated from foreign materials using special procedures.

Fibre composite materials made from recycled fibres are not hazardous to health when complying with currently available guidelines, directives, approvals, and other aids.

In construction, both new and recycled carbon fibres are subject to the registration of the German Institute for Quality Assurance and Certification (RAL) RAL RG 351. This ensures that in construction, only types of carbon fibres are used for mat and rod-shaped reinforcements in concrete construction that, due to their fracture behaviour or fibre morphology, cannot lead to any health-relevant release of fibre dust throughout their lifecycle. It serves as a guide indicating that when using carbon concrete, according to current knowledge and applicable rules, no special occupational safety precautions beyond the usual measures are necessary.

Fibre composite materials made from recycled fibres are economically viable.

Compared to the use of new fibres, fewer products have been established in the market so far. However, the number of market-relevant products is increasing, favoured by social, political, legal, and administrative developments regarding more sustainable resource management and ongoing progress in technological developments. Additionally, the pending scaling effects will create an even more attractive price-performance ratio.

For conclusive proof, the required data and information are currently being completely collected and validated.

Fibre composite materials made from recycled fibres are ecological.

Compared to using new fibres, they particularly reduce the amount of required resources and fibre-containing waste from different industries.

For conclusive proof, the required data and information are currently being completely collected and validated.

Fibre composite materials made from recycled fibres are socially acceptable.

Based on their economic and ecological advantages, the use of recycled fibres enables a wider distribution of resources, as more can be produced and distributed nationally, across Europe, or even globally under the same conditions. Last but not least, a circular value chain offers a promising and attractive job market in the Federal Republic of Germany for both career starters and experienced professionals.

Against the background of continuously increasing demand for fibre composite material applications, the following figures are known for the period 2011 to 2021:

CFRP demand, nationally (Germany): no known statistical survey.

CFRP demand, Europewide: increase from 19,000 t (2011) to over 52,000 t (2021)*.

CFRP demand, worldwide: increase from 39,000 t (2011) to over 92,000 t (2021)**.

GFRP demand, nationally (Germany): increase from 1,164,000 (2011) to over 1,250,000 t (2021)***.

GFRP demand, Europewide: increase from 2,369,000 t (2011) to over 2,910,000 t (2021)*.

GFRP demand, worldwide: increase from 3,990,000 t (2011) to over 5,350,000 (2021)****.

Basalt or natural fibres demand, nationally, Europe-wide, and worldwide: no known statistical survey.

* Institut für Kunststoff- und Kreislauftechnik (IKK), Industrievereinigung Verstärkte Kunststoffe e. V. (AVK): Composites-Recycling-Studie. 2023. p. 7.

** Composite United e. V. (CU e. V.): Marktbericht 2021. Kurzversion. 2021. p. 10.

*** Witten, D. E., & Mathes, V. Der europäische Markt für Faserverstärkte Kunststoffe/Composites 2021: Marktentwicklungen, Trends, Herausforderungen und Ausblicke. 2022. p. 10.

**** Statista, Glass fiber demand worldwide from 2011 to 2022. 2023. URL.

Fibre composite materials have been used in various industries and applications for decades, resulting in fibre-containing waste during production and after actual use. Based on the expected amount of fibre-containing waste, the following figures are known for the period 2011 to 2025 (as reference year for calculations):

CFRP waste, nationally (Germany): no known statistical survey.

CFRP waste, Europewide: 7,000 t (2011) to over 50,000 t (2025)*.

CFRP waste, worldwide: no known statistical survey.

GFRP waste, nationally (Germany): no known statistical survey.

GFRP waste, Europewide: 833,000 t (2011) to over 1,576,000 t (2025)*.

GFRP waste, worldwide: no known statistical survey.

Basalt or natural fibres waste, nationally, Europe-wide, and worldwide: no known statistical survey.

* Institut für Kunststoff- und Kreislauftechnik (IKK), Industrievereinigung Verstärkte Kunststoffe e. V. (AVK): Composites-Recycling-Studie. 2023. p. 68.

With the German Federal Government’s goal to progress towards climate neutrality across all sectors (energy industry, manufacturing, transport, building sector, and agriculture) by 2045, climate-neutral approaches in the use of fibre composite materials are becoming increasingly important. Especially since, according to the Circular Economy Act (KrWG), natural resources must already be conserved and both people and the environment must be protected in the generation and management of waste.

Regarding the construction sector, public tenders will increasingly need to promote climate-neutral construction methods, and eco-balance sheets must be presented for corresponding certifications – for example, for sustainable building certification through BNB or DGNB. Furthermore, it will become increasingly important to make decisions for climate-neutral building materials or constructions at an early stage of planning. The use of fibre composite materials, particularly reinforcement with non-metallic reinforcement from recycled fibres, will thus steadily gain importance.

In addition to the changing legal and regulatory framework, funding and third-party resources for research and development services in circular economy and resource management are increasingly being provided by individual federal states, the Federal Republic of Germany, and the European Union.

Please refer to the project-related website for more information about the “Elbe Valley Saxony” region.

The members of the C³Association and institutions actively participating in the WIRreFa project have direct access to the C³Cloud via the project’s own website, through which all collected and processed results and findings (final reports and fact sheets) as well as further data and information (image and video material, statistics, studies, etc.) are made available.

Via the “Über C³” and “Fachbereich” sections on the C³Association website, you can find all further information about both the C³Association and its departments, such as C³Sustainability.