The circularity of polymer composites

To better understand the state-of-the-art of the circularity of fibre reinforced polymer composites (FRPC) in Europe, the European Technology Platform on Sustainable Chemistry (SusChem) asked Bax & Company to explore the field’s present status and future outlook; an assignment which included interviewing more than 20 experts along the entire value chain of FRPC. The resulting insights feature in the white paper Circularity of Polymer Composites, available here, and the most relevant findings are summarised below.

by Laszlo Bax, Marcos Ierides & Violeta Fernández of Bax & Company

Growing demand for lighter and more complex applications

Figure 1. Composites production in Europe by type of application

On the environmental side, lighter materials also represent a major opportunity for the reduction of emissions during the use phase of transportation means, which is why there has been a major push for the use of these materials in several sectors.

For both, the (mechanical) performance and environmental benefits, it is not surprising that the main drivers of composites demand in Europe have been the automotive, aerospace construction and infrastructure sectors. However, the wind energy, electronics, and sports and leisure sectors are evolving into important sectors.

However, a growing concern regarding the use of FRPC is that their intrinsic complexity seems to be at odds with the current European agenda on circularity and sustainability. The same inherent properties that make composite materials so advantageous and attractive for a large number of applications also makes their disassembly and recycling particularly challenging and costly.

Without the proper strategies in place, this inevitably results in large amounts of waste being generated, ending up in landfills or incinerated. In some application areas (e.g. aeronautics), as much as 40% of the raw materials used end up either as production scrap or in off-spec parts, representing a major loss of resources and energy if not recycled. Post-use FRPC waste presents an even bigger challenge in terms of residual value extraction through recycling or re-use. Some 40.000 tonnes of composite waste are currently deposited in Europe’s landfills annually and, by the end of 2015, 304.000 tonnes of composite waste were estimated to have accumulated worldwide.

Current circularity scenario

Figure 2. Waste management hierarchy applied to PC

The analysis highlights the limited availability and adoption of practices extending the lifetime of composite parts (e.g. self-healing polymers, repair and maintenance solutions). The research further underlines the lack of maturity and economic viability of technologies enabling a higher value extraction from composite materials, both for resin and fibre (e.g. chemical and thermal recycling rather than mechanical grinding into low value filler powder).

As a result of the lack of maturity and/or adoption of high value recycling options, most waste handling strategies for FRPC still use low value mechanical grinding or even simply incinerate the waste material as a means of energy recovery. At the bottom of the pyramid, landfill is still a legal option chosen for a considerable share of all FRPC today.

Figure 3. Attractiveness and maturity of each technology

Our main findings with regard to the state-of-the art of recycling technologies suggest solvolysis and pyrolysis are the most promising recycling technologies since they allow for the highest levels of material and value recovery of both fibre and matrix. Especially for the most challenging case of carbon fibre based FRPC recovery, both technologies have proven positive results in recovering valuable carbon fibres that preserve a high degree of their mechanical properties. Between these two options, the present consensus among experts suggests solvolysis delivers slightly better results in terms of quality compared to pyrolysis.

The maturity levels of all the analysed recycling technologies used to recycle FRPC are plotted against their potential to extract value in the figure, providing an indicator of overall desirability.

Adopting FRPC circularity — the challenges and opportunities

  • Technical challenges relate to the limitations of materials, applications and technologies that can enable higher levels of circularity. Some of the technical challenges relate to the complexity and dimensions of parts containing composite materials (e.g. wind turbine blades), while others originate from the large variety of existing composite materials and the resulting endless amount of material combinations, which makes sorting and recycling challenging.
  • Market challenges consider constraints along the value chain, namely financial, social, behavioural or logistical limitations. One example is the associated risk in investing in a recycling market as it is highly sensitive to composite waste supply and heterogeneity. This prevents economies of scale, translating into substantially higher prices of secondary material compared to virgin material prices, an obvious market barrier for recycled FRPC.
  • Policy challenges refer to the inadequacy, or lack, of local, national, or European regulations enabling composites circularity. Some regulations are simply outdated, while others can be too strict and/or do not match the current material properties or technological development. Across Europe, valuable waste is still not considered as a resource but is considered under the very same strict regulations as hazardous wastes, which extremely limits trade, and consequently reuse and treatment. This often results in contradictory agendas and objectives across European countries.

Nevertheless, most experts are confident that Europe possesses the know-how, resources and human and technical capital to develop and deliver the required technological developments to effectively achieve circularity. Industrial organisations, universities and RTOs are doing fundamental and applied research in the field of FRPC recycling, advancing promising waste treatment technologies as well as improving the intrinsic recycling properties of composite materials. Also, the observed market uptake of thermoplastic composites, which can be re-melted to separate polymer material from reinforcement fibres, and the increasing availability of bio-based polymers — and especially the growing developments of gas and organic waste-based polymers — that can be combined with bio-based fibres into non-fossil fuel based FRPC bring optimistic prospects for the future of PC circularity. Additionally, the intrinsic longevity of FRPC, coupled with a shift towards circular product design and with proper maintenance and advanced repair, represents a major advantage towards achieving circularity, compared to less durable materials.

The way forward

Figure 4. Life-cycle strategy

Any strategy for moving forward towards composites circularity must take into account the full life-cycle of composite materials, identify the obstacles that hinder circularity in each of its life-cycle stages, detect the linkages between value chain actors and determine the specific actions necessary to overcome them.

In the material design and production phase, material suppliers and recyclers will need to work together to develop additives and new material formulations such as sensor-readable tracers that allow easier sorting, and reversible thermoset resins that allow resin-fibre separation, and recycling of the matrix. In the product design phase, end-users should ideally define common interface standards to enable the re-use of parts that have a longer lifetime than the application they are used for (e.g. FRPC hydrogen tanks could have a longer lifetime than the vehicle they are used in).

Additionally, the design of parts should be simplified to more easily dismantle the different materials, as well as minimise scrap. At the recycling phase, the development and upscaling of promising technologies that allow higher value retention such as solvolysis and and pyrolysis should be accelerated. Finally, at the market and policy level, regulations should be adapted and harmonised across Europe, to incentivise the trade of FRPC waste, and ideally scale up small recycling plants next to existing manufacturing lines to shorten cycles and reincorporate recycled material back in the production line.

Fundamental change will require a holistic approach to production, consumption and treatment. One that aims at designing out waste of the system, i.e, that has a primary emphasis on material, product and process design. Focusing on design requires considering the next stages: reuse, repurpose and recycling and aims at enhancing and optimising them. All this needs to be done while minimising energy use and material loss.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store