“A huge opportunity” – academics in Australia develop new way of recycling carbon fibre waste

Academics at the University of Sydney have developed a new way of recycling waste from carbon fibre and glass fibre composites, in what has been hailed as “a huge opportunity” to deal with what will be an estimated 840,300 tonnes of waste material every year by 2050 if the problem is not addressed.

Initially developed for use as filaments in light bulbs by Sir Joseph Wilson Swan in 1860 – carbon fibre’s use in industrial applications took off from the 1960s onwards, with the composite material nowadays widely used across a range of industries due to its strength, light weight and resistance to both stress and corrosion.

Besides sectors such as aerospace, automotive, energy and marine, it is also widely used within the sporting goods sector, including of course for bicycle frames and components, as well as accessories such as helmets and bottle cages.

According to world cycling’s governing body, the UCI, in 2021 the sports industry was the third largest user of carbon fibre worldwide, with most sports equipment that uses the material having an average lifespan of three years, and 90 per cent ending up in landfill at the end of its life.

Researchers from the University of Sydney say that by the end of this decade, carbon and glass fibre composites (CFRP) will represent a key source of waste globally, with the total amount of such waste projected to reach 840,300 tonnes a year by 2050.

Dr Ali Hadigheh of the university’s School of Civil Engineering, and Dr Yaning Wei, who recently completed her PhD on the subject of CFRP recycling under his supervision, say that the process they have developed, if fully implemented, could reduce energy use by 70 per cent as well as preventing most such waste from being incinerated or going to landfill, as currently happens.

“Carbon fibre composites are considered a ‘wonder’ material – they are durable, resistant to weathering and highly versatile – so much so that their use is projected to increase by at least 60 percent in the next decade alone,” Dr Hadigheh said.

“But this huge growth also brings a huge increase in waste,” he continued. “For instance, it's been estimated that around 500,000 tonnes of carbon and glass fibre composite waste from the renewable energy sector will exist by 2030.”

> How safe is your carbon frame?

While processes for CFRP recycling already exist, the University of Sydney team – which had previously undertaken a detailed assessment of 10 such systems – claim that their method, outlined in a paper published in the journal Composites Part B: Engineering, results in more material being recovered, as well as retaining a greater percentage of their original strength, and is also more efficient in terms of energy expended.

“Our kinetic analysis revealed that pre-treated CFRP undergoes an additional reaction stage, enabling enhanced breakdown at lower temperatures compared to untreated CFRP,” Dr Hadigheh explained.

“The solvolysis pre-treatment not only facilitates greater breakdown but also preserves the mechanical properties of fibres by reducing heat consumption during recycling.

“To demonstrate the real-world applicability of our method, we successfully recycled part of a bicycle frame and airplane scraps made of CFRP composites using our hybrid approach.

“These results not only validate the effectiveness of chemical pre-treatment but also demonstrate the improved mechanical characteristics of the recycled carbon fibres,” said Dr Hadigheh.

Dr Wei said: “This is a huge opportunity, and not only because various modes of recycling are cost-effective and minimally impactful on the environment.

“In an era of mounting supply chain disruptions, local recycled products can provide a more immediate product when compared to imports and create a burgeoning advanced manufacturing industry.

“While awareness of everyday consumer recycling is increasing and plastic waste is in the spotlight, Australia must urgently consider wide-scale recycling of new generation construction materials before they mount up as another waste problem and are put into the ‘too hard basket’,” she added.

The research papers were funded by the Australian Research Council (ARC) under its Discovery Early Career Researcher Award (DECRA).

> Understanding carbon bike frames: what does unidirectional, woven and high-modulus fibre all mean?