Composites: why aren’t they circular?

Carbon fibre composite product for motor sport

Emma Arussi, Circularity Innovation Consultant at European innovation consultancy Bax & Company, explores how materials stakeholders across the value chain can make the material of Europe’s low-carbon future circular.

Composites: miraculously light, strong, durable and multifunctional… but why aren’t they circular?

When it comes to sustainability and circularity, (polymer) composite materials aren’t necessarily one of the hottest topics. However, experts from the automotive, aircraft and energy sectors know that they’re quite a big deal.

Improved lightweight performance, reduced fuel consumption, lower costs and increased structural stability are just a few of several advantages that composite materials have over conventional metals, which have led to their huge projected market size (€112 billion by 2027).

However, estimations of the amount of waste generated by the use of polymer composites in the coming years – 683,000 tonnes per year by 2025 to be exact, or the equivalent of 785 composite waste-filled swimming pools (1) – leave a bittersweet taste to the high quality and multifunctional material of the future.

So why don’t we just recycle this composite waste?

Jet engine

While composite materials can make a positive impact on the energy efficiency, durability, and weight reduction of vehicles, aircraft, and wind turbines, their end-of-life (EoL) treatment is challenging and costly.

Most composites in use today are made by reinforcing plastics with glass or carbon fibres, owing to their name, Fibre Reinforced Plastics (RFPs). The plastics of these equations are either thermosets or thermoplastic resins, the difference being that while the former will set when heated to a certain temperature, the latter will melt.

Thermosets are the most used today and have been for decades – more than 60% of composites used in industry are thermosets (2).

The convenience of having a material that is irreversibly set after using a hot mould makes it an obvious choice for the mass production of permanent automotive components and the large, solid shapes needed to manufacture blades of wind turbines or aircraft exterior parts, for example.

If recycling composites doesn’t sound challenging enough already, before the process can even begin, a system for the collection of end-of-life (EoL) materials and sorting and separation of components is yet to be established throughout Europe

However, this irreversible setting of molecular bonds on a nano level is exactly the reason recycling is so challenging and represents an aspect of the production process that manufacturers and designers of structural parts in the energy and transport sectors have not sufficiently considered. Additionally, the use of fillers and additives that provide additional properties or sensor elements enabling multi-functionality further increases the difficulty of separation.

If recycling composites doesn’t sound challenging enough already, before the process can even begin, a system for the collection of end-of-life (EoL) materials and sorting and separation of components is yet to be established throughout Europe.

Furthermore, the responsibility of dealing with the EoL material currently lies with the end user; a stakeholder that commonly lacks adequate knowledge of the composition of the acquired composites.

When the end-user does decide to recycle the EoL parts, they will soon realise that there are many recycling techniques to choose from. However, not all are accessible or cost-effective, and the value obtained from the recyclate varies, as some expensive but high-value techniques may not be profitable for the EoL material.

As the quality of recycled material isn´t always homogeneous in bulk, testing a fraction doesn´t always give accurate results. In combination with the hassle and price of testing in the first place, this makes manufacturers hesitant to use recycled materials for next-generation products, thus giving the impression that the process of recycling EoL material was impractical to begin with.

Solving composite waste through the Circular Economy Hierarchy


waste hierarchy

The European Commission has found that 80% of the results of value retention and circularity are predetermined in the design phase. You might recognise the waste pyramid from your office or university kitchen. The same hierarchy you consider when trying to reduce your carbon footprint also counts for high-end application composite materials.

Why would you go through the trouble of recycling a wind turbine blade, if you can prevent it from degrading in the first place? And why would you send a car bumper to a landfill if you can refurbish it and use it anew?

However, it’s not only recycling that has been made difficult by manufacturers. Circular economy practices such as the refurbishment, reuse and repair of components need to be taken into consideration from the start of the design phase.

Examples of practices that allow for longer value retention include the accessibility of components for repair or the ease of assembly and disassembly of components using standardised methods and materials (3).

Europe signals that the waste can’t go on

The European Commission (EC) recognises the problem of car, aircraft and wind turbine materials ending up in landfill, and has already set new plans to reduce the impact of (composite) materials on the environment, as part of its circular economy action plan.

Certain countries and industries are already setting some good examples: France instated a repairability index in 2021, which helps consumers of digital appliances make a more sustainable choice when purchasing a new device. Also, landfilling bans or restrictions have already been introduced in several EU countries (4).

It is becoming evident that over the next decade, radical changes in the way composite waste is treated can be expected from European stakeholders. Still, it is important to remember that these changes will not occur naturally, and work must be carried out to ensure they are effectively implemented.

Making composites circular is a Medusa-like problem


Creating a circular value chain for composites is challenging on countless fronts, and it reminds us a little of the snake-haired monster from ancient Greek mythology. Tackling the individual snakes will achieve little, and the overwhelming number of problems can easily petrify a stakeholder into inaction.

For example, you can develop a material that is immensely durable due to the use of additives, but when the products do reach their EoL, these additives are inseparable from the valuable carbon fibres you want to retrieve.

Or perhaps you have found a recycling technique that promises 95% recovery of material, but at the same time, this technique is incredibly expensive and energy intensive.

Learning from the Greek hero Perseus, who slew Medusa, we need to face the problem with a mirror. In other words, we need information, data, comparisons and reliable sources.

  1. An Open Data Platform for all stakeholders of the composite industry that offers Life Cycle Analysis (LCA) driven information about manufacturing processes, raw material sourcing and EoL treatment, so that stakeholders can choose the best options for their applications.
  2. Guidelines for the design of circularity practices, and standardised methods that ensure interchangeability.
  3. A material passport that will drive efficient recycling processes.
  4. A legitimate recycling class system that differentiates the value of recycled materials, so that manufacturers know what they are working with.

Every stakeholder in the materials chain has a role to play


Automotive sector

We need heroes such as Perseus that will “hold the mirror” and take the required actions:

  • Policymakers should discourage stakeholders from generating waste, using non-renewable fossil-based materials and overconsuming energy through targeted regulations. Examples include carbon taxes, further banning of landfilling and financial incentives to incorporate renewable materials with a lower carbon footprint.
  • Researchers and market stakeholders must work together with policymakers to remove regulatory barriers that make it difficult to transport waste across borders or implement new rules that support the adoption of recycled materials.
  • Large OEMs and manufacturers should offer their unused or EoL parts and manufacturing waste on a secondary marketplace, allowing EoL material to thrive again, even if it’s in a different application.
  • Countries need to localise recycling facilities based on the need of the region or develop portable recycling facilities to reduce the costs and environmental impact of the transportation of large components over a long distance.
  • Clear responsibility for the EoL has to be assigned to the appropriate stakeholder by policymakers.

European stakeholders will have to step up their game to integrate technology, market and legal practices to end the continuous loss of value from composite materials through outdated solutions such as landfilling and incineration.

Examples that give hope for the future of composites

Reuse of old wind turbine blades

In the Danish town of Aalborg, old wind turbine blades have been transformed into bike shelters for the city’s cyclists. This creates the opportunity for the reuse of materials that would otherwise be dumped in landfills. Shelters protect the bikes from harsh Scandinavian weather conditions, especially during winter.

Recyclable material development

Arkema – a speciality chemicals company – has developed the Elium® thermoplastic liquid resin. Liquid resins are often one of the 2 main components of composite material. Fibres made of carbon, glass, or aramid are typically the other main component.

With a special recycling technology, they have successfully separated the two components without harming the functional integrity of the costly fibres. The resin was demonstrated in a full, 62-metre wind turbine blade. The blade is the first 100% recyclable composite wind turbine product.

The Eco calculator of EuCIA

EuCIA Eco Impact Calculator helps manufacturers determine the environmental impact of composite products from cradle to gate: from the raw materials up to the point of sale. Users can calculate, save and export the environmental impacts of as many different composite products and components as they see fit.


  1. Calculated with the average density of solid waste or municipal solid waste (MSW) (311.73 kg/m3), and the volume of an Olympic swimming pool (2,500 m3).
  3. Joustra, J., & Bessai, R. (n.d.). Circular Composites A design guide for products containing composite materials in a circular economy.
  4. landfill-ban

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