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Cementing a sustainable future with composite recycling

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Composite waste is projected to rise to a staggering 683,000 metric tonnes annually by 2050 in Europe alone which poses a challenge for the industry. With its diverse composition of glass fibres, additives and thermosetting resins, composite waste demands innovative solutions to mitigate its environmental impact.

Here, Kim Sjödahl, senior vice president for technology and sustainability at specialist composites manufacturer Exel Composites, explores the initiatives shaping the future of composites manufacturing.

As the composites industry wrestles with the complexities of sustainability, the importance of adhering to social responsibility standards grows more evident than ever. ISO 26000, developed by the International Organization for Standardization (ISO), provides an in-depth framework for organisations to assess and address their social, environmental, and ethical impacts. While traditionally associated with community involvement and ethical business conduct, ISO 26000 also offers valuable guidance for promoting sustainable practices throughout the product lifecycle.

In composites manufacturing, companies such as Exel Composites integrate ISO 26000 principles into its operations, emphasising transparency in material sourcing, stakeholder engagement, and environmental management. These principles extend beyond production processes to include product end-of-life considerations, including recycling and waste management.

Composite materials present a significant challenge for recycling initiatives due to their complex composition and structure. Composites vary in chemical compositions and physical properties, and consist of fibres, such as glass or carbon, embedded in a matrix, like resin. This heterogeneity makes separation difficult - especially considering the strong bonding between the components - and risks material damage.

Moreover, unlike traditional materials such as metals, plastics, or paper, there is a lack of infrastructure and technology available for large-scale composite recycling. Developing cost-effective and environmentally sustainable recycling methods for composites has remained a major hurdle. That is, however, until December 2020 when the Finnish Plastics Industries Federation, the Ministry of the Environment, Kuusakoski Oy, Finnsementti Oy and seven composite industry companies including Exel Composites, secured funding for an innovative initiative.

The KiMuRa project and cement production

The KiMuRa project spearheads the development of a circular economy model for composite products by implementing open-loop recycling techniques to transform composite waste into cement through co-processing. In collaboration with recycling experts, manufacturers supply glass fibre composite waste for processing. This co-processing method involves the shredding and crushing of the waste to break the composites down into more manageable pieces. Subsequently, the prepared composite waste is introduced into a cement kiln, where each constituent element of the glass contributes to the formation of cement clinker, an essential intermediary in cement production. Additionally, co-processing enables energy recovery, as the organic components in the resins generate heat energy during combustion, reducing the reliance on fossil fuels in cement kiln operations.

Cement clinker formation conventionally relies on two primary materials: limestone (calcium carbonate) and aluminium silicate clays like kaolinite. These materials undergo a chemical reaction to produce alite, the key component of cement clinker. In the co-processing method, glass fibres serve as a replacement for both limestone and kaolinite. Glass fibre’s composition, which is approximately 50% silicon dioxide, up to 15% aluminium oxide, and 20% calcium oxide, makes it an effective alternative for both substrates in cement clinker production.

The incorporation of the resin component of the composite in cement production serves to substitute traditional fossil fuels like coal and coke, alongside other solid recovered fuels (SRF). The carbon and hydrogen composition of these elements gives a high calorific value, making them efficient fuels for industrial processes. During combustion, both the SRF and composite resins undergo exothermic reactions, releasing heat that facilitates the high-temperature processes crucial for clinker formation in cement production.

The co-processing of composite waste offers significant environmental benefits. Firstly, it effectively addresses composite waste production by providing a step in the right direction towards a sustainable waste management solution, diverting it away from energy recovery solutions and/or landfills.

Importantly, unlike traditional waste incineration methods, co-processing generates no ash residue, further minimising environmental impact. Additionally, the mineralised components of the composite waste, such as glass fibre, serve as substitutes for traditional raw materials in cement manufacturing, reducing the need for mining and extraction operations. This conservation of natural resources helps reduce the environmental impact of cement production.

Challenges for the whole industry

Despite the strides made by the KiMuRa project, challenges remain. Currently, the entire Finnish composites industry produces about 2,000 tonnes of scrap annually, a fraction of the cement processing plant’s capacity, which stands at tens of times that amount. The processing plant eagerly accepts as much composite scrap and waste as possible; the limited supply hampers the project’s scale and effectiveness. Despite this, manufacturers still express concerns about the financial implications of participating in the initiative. The costs associated with transporting, crushing, and processing composite waste are increased compared to traditional waste management. To incentivise participation, the companies involved in the project so far have agreed that any company willing to join in this recycling route can do so without having to pay investments or the work done so far. This inclusive approach encompasses not only manufacturers but also any business generating composite waste during its production processes.

To help address this challenge, Business Finland has committed €1.4 million to support the industrial continuation of the project led by recycling company Kuusakoski. This initiative aims to construct an efficient composite crushing and shredding plant. With advanced technology and streamlined processes, this facility promises to alleviate the financial burden associated with preparing composite waste for co-processing. The new plant will consist of several covered conveyors, two shredders, a magnet for removing ferrous materials, and a dust control system. The dust control system also boasts its removal of produced fine dust by composite crushing. Increasing efficiency and reducing costs will enable more composite manufacturers to participate in the consortium, further advancing the goals of the KiMuRa project.

Composite waste in Europe is on a trajectory to reach 683,000 metric tonnes annually by 2050. Exel Composites, alongside industry leaders and partners, leads the charge in innovative recycling solutions. The KiMuRa project exemplifies this commitment, repurposing composite waste into valuable resources while reducing environmental impact. Despite challenges like limited scrap availability and cost concerns, the journey towards a traceless, zero-landfill future persists.

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