Aidan Bell, founder of sustainable company, EnviroBuild provides a guide to recycling composites: where we’re at and where we’re going.
The weight saving and strengthening properties of composites has revolutionised design across a variety of industries, from engineering, manufacturing, automotive and construction. However, due to their inherent nature of heterogeneity, strength and durability, recycling composites is hard.
It’s not that the industry doesn’t have the technological competency, it’s simply because the application and market development of recycling composites is still in its infancy. A report from Composites UK found that the use of composites is set to reach $95 billion globally by 2020, an increase of 40% from 2014, a concerning statistic if we consider informal numbers from CompositeWorld that claim only around 2% of composites-related companies are active recyclers.
Undoubtedly, some composites are harder to recycle than others, in particular for the thermoset-based polymer composite. According to the Recycling of composite materials report form the journal of Chemical Engineering and Processing: Process Intensification, there are currently no commercial operations for economically recycling composite materials.
The recycling challenges
So why are we falling behind? Government legislation to cut emissions and increase fuel efficiency has increased the various industries needs to use composites, yet little attention has been given to addressing the challenges of recycling these materials. Despite this, the current waste management and environmental legislations requires all engineering materials to be properly recycled.
There exists a lack of both information and consistency from government as well as local councils. In fact, the majority of legislation places the responsibility of recycling directly with the producer of the composite, such as the ELV directive stating the automotive industry is responsible for dealing with recycling all of its own composites.
Additionally, the legislation in place just looks to increase recycling rates and reduce availability of landfill, which is simply not useful in relation to composites here. According to a Composite UK report, the EU’s Circular Economy Package and proposed changes to the Waste Framework Directive will look to limit municipal waste to landfill to 10% by 2030.
Where the industry is at
When it comes to reinforcement fibres, various technologies have already been developed, including mechanical recycling, thermal recycling and chemical recycling. However, due to the high costs, lack of adequate markets and lower quality of the recyclates, these methods are yet to be widely commercialised. To tackle this, there needs to be extensive research and development into more efficient separation technologies, as well as creating better recyclable composites right from design.
Despite this, there is demonstrably huge interest and activity in recycling a wide variety of composite materials in the UK, and real applications of recycled fibre are growing. Mechanical, thermal and chemical methods can be applied for material and energy recovery. Germany is the leader in this, with an already well-established commercial glass fibre-reinforced plastic (GFRP) and carbon fibre reinforced-plastic (CFRP) industry several years ahead of other European countries.
When it comes to CFRP, there are in fact already a lot of schemes in place. In the UK, ELG Carbon Fibre is currently leading the way in establishing a CFRP recycling supply chain, by creating intermediate products with recycled carbon fibre for milled and chopped applications in thermoplastic and thermoset compounds and non-woven textiles.
Glass-reinforced polymers (GRP) are one of the more challenging to recycle in terms of economics. According to the Composites UK report, the most fruitful direction for end-of-life applications is to combine the process of recycling alongside waste fuel from cement kilns. This is one of the processes already widely utilised in Germany, and increasingly this collaborative cement kiln process is starting to uptake in the UK too.
Understandably there are many alternative methods being researched at present, including chemical recycling processes which allows recovery of product from the resin chemicals. According to some reports, the energy usage and therefore environmental impact of the chemical recycling process is typically higher than other methods however. Thermoplastic composites can be shredded and recycled by melting. When it comes to dry fibre, an increasing amount of glass fibre waste is used in infrastructure and timber replacement products.
Manufacturing waste can be re-ground and then used in other processes including casting and moulding, which provides reinforcement value from short fibres or flakes composites. Some companies already operate this, but it’s unlikely to become scalable on a broader commercial level as it produces a relatively low value product.
The future of design and build
Although the recycling of composite materials report claims that more research and development is universally required for better recyclable composites and efficient separation technologies, it’s fair to say that processes are evolving in the composite market. Manufacturing companies are looking to shake up the design, build and end-of-life management elements to ensure that they are more recyclable.
When it comes to design, there are several innovations at play. For example, we’ve seen the rise of epoxy resins which are easier to recycle. This composite can be degraded in low temperature chemical processes which releases fibres and resins to be used as thermoplastics.
Wood plastic composite (WPC) can often contain less than 90% recycled material, making it environmentally-friendly and requires less maintenance than the alternative of solid wood. The recycling process requires return of the product back to the manufacturers, who can then reuse it to remake more composite, but the collection is difficult without scale and is not something supported by local authorities’ standard service. However, as the industry gains scale it is hoped that cooperation between manufacturers will result in a take-back scheme.
Furthermore, building manufacturers in the UK are already making advances in recycling composite waste from construction products, such as Hambleside Danelaw’s composite roofing product.
These developments are reflective of the kind of recyclable composite materials we can expect to be developed moving forward. This integration of recycling considerations in the initial design is the change we need to embrace in order to see this. Without these systematic changes at the design stage, we cannot realistically envisage a commercial and scalable recycling process for composite materials in the near future.
