University of Leeds: Revolutionary dyeing process wins Circular Future Fund prize

The prize will allow Leeds researchers to further explore the creation of a circular economy for polyester and the ability to recycle it, as well as assessing the economic and environmental benefits of what has been dubbed the “polyester-infinity loop”.

The Circular Future Fund is an initiative run by John Lewis Partnership in partnership with environmental charity Hubbub. Each year the fund awards £1 million to pioneering projects that are working to create a circular economy – one which eliminates waste and pollution, circulates products and materials, and regenerates nature.

Polyester, which is usually derived from petroleum, is the world’s most consumed textile fibre, yet recycled polyester only contributes to 15% of total production, almost all of which is made from plastic bottles.

A major barrier to recycling polyester fabric is the presence of dyes, which makes fibre-to-fibre recycling almost impossible.

Researchers at Leeds Institute of Textiles and Colour (LITAC), in collaboration with the Wolfson CO2 Laboratory in the School of Chemistry, are developing a solution that uses new technology to deploy carbon dioxide and separate dyes from fibre, enabling easier recycling of the polyester.

Currently, recycled polyester (rPET) is not based on end-of-life-clothing, but on mechanically recycled polyester from plastic bottles. This new CO2 technology will enable fibre-to-fibre recycling, creating a truly circular process.

In order to meet the UN’s Sustainable Development Goal of recycling 90% of PET plastic by 2030, chemical recycling – and specifically fibre-to-fibre recycling – is essential.

Richard Blackburn, Professor of Sustainable Materials
Richard Blackburn, Professor of Sustainable Materials in the School of Design, said: “This award from the Circular Future Fund will allow us to take a significant next step in tackling the global environmental and economic issue of polyester recycling.

“Polyester is the global clothing industry’s most consumed fibre, yet fibre-to-fibre recycling for the material is unfeasible because of the chemicals involved in the dyeing process. In order to meet the UN’s Sustainable Development Goal of recycling 90% of PET plastic by 2030, chemical recycling – and specifically fibre-to-fibre recycling – is essential.”

Polyester is dyed with disperse dyes – a synthetic type of dye – and auxiliary chemicals, both which are essential in the dyeing process. However, 10% of disperse dyes applied are lost in the process.

The dyeing process also involves huge water and energy use and it is impossible to recycle the chemicals.

The new dyeing technology, developed by Leeds researchers, removes the polluting auxiliary chemicals, recycles the water, and uses less energy. Furthermore, removing the dyes from the textile allows for both the dye and fibre to be recycled.

Supercritical fluid CO2 dyeing systems – where high pressure (usually liquid or supercritical) CO2 is used as the solvent for dyeing instead of water – have recently received much interest as they can reduce the negative environmental impact of a dyeing process.

Sustainable dyeing and dyeing removal processes represent a crucial missing link in existing recycling infrastructure. This award from the Circular Future Fund will greatly help us in our mission to create a viable economic route for recycling polyester.

Chris Rayner, Professor of Organic Chemistry
Chris Rayner, Professor of Organic Chemistry in the School of Chemistry, said: “Supercritical fluid CO2 dyeing systems are really interesting, but very expensive and rely on extreme pressures to dye materials. We still use CO2 but our new approach can be used in existing dyeing machinery anywhere, making it much easier to apply in industry.

“Sustainable dyeing and dyeing removal processes represent a crucial missing link in existing recycling infrastructure. This award from the Circular Future Fund will greatly help us in our mission to create a viable economic route for recycling polyester.”

Three other projects have been awarded a share of the £1 million prize, these include: expandable and recyclable children’s shoes, a menstrual cup use, and a “lend and mend” scheme for household goods and clothing in Scottish libraries.

The winners were chosen by an independent panel of industry experts, including senior representatives from John Lewis & Partners and with support from Hubbub. Overall 245 projects applied for the fund. The four winners will be supported by Hubbub over the next year to develop and achieve their ambitions.

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