Scientists have developed a new method for dyeing polyester that significantly reduces the use of water and harmful chemicals, a breakthrough that could address a major source of global water pollution. The technique, created by a University of Leeds spin-out company called SwitchDye, uses carbonated water to help lock dye into the synthetic fabric, tackling a long-standing environmental challenge within the textile industry. This innovation promises to not only clean up the manufacturing process but also to make polyester, the world’s most common clothing fiber, easier and safer to recycle.

The core of the problem lies in polyester’s chemical nature. As a hydrophobic fiber, it repels water, making it difficult for dyes to penetrate and bond with the material without the use of high temperatures, high pressure, and a cocktail of chemical agents. This process is incredibly resource-intensive and generates vast quantities of toxic wastewater. The textile industry is estimated to be responsible for about 20% of the world’s clean water pollution, much of it from dyeing operations. The new method offers a more sustainable alternative by fundamentally changing how dye is applied, potentially disrupting a system that has relied on wasteful practices for decades.

The Heavy Environmental Cost of Color

Polyester production has grown steadily for years and now accounts for more than half of all fiber used globally. While versatile and inexpensive, its environmental footprint is substantial. Beyond its origins as a petroleum product, the dyeing phase of its lifecycle presents the most significant ecological hazard. Traditional dyeing methods require large volumes of water, which becomes contaminated with unused dyes and auxiliary chemicals. This effluent is often discharged into rivers and streams, where it can harm aquatic life and contaminate drinking water sources for nearby communities.

Furthermore, the chemicals used to treat this wastewater before its release can be just as damaging. “Not many people know that even more toxic chemicals are used to turn brightly coloured wastewater into transparent liquid,” said Dr. Nathaniel Crompton, a co-founder of SwitchDye. “When released into freshwater, this is a secret killer that harms people, animals and the environment.” This chemical-intensive process complicates recycling efforts. Contaminated fabrics are difficult to process into new, high-quality garments, often leading them to be downcycled into lower-value products or sent to landfills, where they can take centuries to decompose.

A Carbonated Approach to Dyeing

The SwitchDye technology introduces a novel solution by leveraging a simple and widely available ingredient: carbonated water. The process involves injecting a small amount of this “fizzy water” into the dye bath. The dissolved carbon dioxide alters the chemistry of the bath, triggering a unique “switching behavior” in the specially designed dyes, which allows them to more easily penetrate and bond within the polyester fibers. This approach dramatically reduces the need for the harsh chemicals and excessive water common in conventional dyeing.

The results from this new method are significant. According to the research team, the technique uses 90% fewer chemicals and 40% less water than standard industry practices. By operating under less extreme conditions, it also has the potential to reduce energy consumption. The innovation lies not just in the use of carbonated water but in the interplay between the CO2 and the custom dyes, which were developed to respond to this specific chemical trigger. This allows for precise control over the dyeing process, ensuring colorfastness and quality comparable to traditional methods but with a fraction of the environmental impact.

From University Research to a Commercial Venture

Academic Origins

The foundation for the SwitchDye technology was built on an interdisciplinary collaboration at the University of Leeds between the Schools of Design and Chemistry. The initial concept was invented by Professor Richard Blackburn and Professor Chris Rayner, who recognized the potential for a fundamental shift in dyeing chemistry. Their work laid the theoretical groundwork for a more sustainable process, targeting the specific molecular interactions between dye and fiber.

Doctoral Development

The concept was further developed into a practical application by Dr. Nathaniel Crompton, who took on the project for his Ph.D. He refined the technique, rigorously tested its effectiveness, and established the precise conditions needed to achieve consistent results. Now serving as the CEO of the spin-out company, Dr. Crompton leads the effort to bring the technology to the broader market. The founding team also includes Dr. Harrison Oates, ensuring a blend of scientific expertise and entrepreneurial vision guides the company’s growth.

Paving the Way for a Circular Textile Economy

A key advantage of the SwitchDye method is its potential to improve the recyclability of polyester. Because the process uses fewer and less hazardous chemicals, the resulting dyed fabric is cleaner and less contaminated. This makes it a better candidate for garment-to-garment recycling, a crucial step toward creating a circular economy for fashion. In a circular system, old clothes are not thrown away but are instead used as the raw material for new ones, reducing waste and the demand for virgin resources.

The ability to more easily remove the dye from the fabric—a feature enabled by the same “switching” mechanism used to apply it—could further enhance recycling. If dyes can be stripped from polyester fibers without degrading the polymer, the recycled material will be of a higher quality and can be re-dyed and repurposed into a wider range of new textiles. This would be a significant advancement over current recycling methods, which often yield a grayish, lower-grade material with limited applications.

Scaling Up for Global Impact

While the technology has been proven in a laboratory setting, the next challenge for SwitchDye is to scale up its process for industrial production. Transitioning from small-batch experiments to dyeing massive rolls of fabric in commercial facilities requires significant investment, engineering, and partnership with manufacturers. The textile industry is vast and has long-established supply chains, making the adoption of new technologies a complex undertaking.

The founders are actively seeking support to overcome these hurdles. “We can’t solve this problem without the backing of industry, investors and policymakers, so we’re excited to share SwitchDye publicly as we aim to scale up,” Dr. Crompton stated. The success of this greener dyeing method will depend on its ability to compete on cost, quality, and efficiency with conventional processes. With growing consumer demand for sustainable products and increasing regulatory pressure on polluters, innovations like SwitchDye are positioned to play a critical role in cleaning up one of the world’s most essential—and polluting—industries.