Global Textile Industry Explores Sustainable Dyeing Methods

Numerous Chinese factories that produce synthetic dyes for the textile industry got shut down for environmental inspections starting last summer. In the wake of those closures, new dyeing methods for textiles are emerging that could help save water, reduce pollutants, save energy, and protect human health.

In a recent in-depth article for Chemical & Engineering News, Melody M. Bomgardner details how textile industry suppliers are working to change a process that results in effluent containing high concentrations of dyes and chemicals like chromium, arsenic, copper, and zinc.

The biggest challenge is cost. “Price competition is fierce, and profits are shrinking thanks to volatile raw material costs and rising wages,” Bomgardner wrote. “Despite public commitments by apparel brands to become more sustainable, suppliers contacted by C&EN say their customers will not buy anything that could raise the cost of a finished garment by as little as a penny.”

Given that competitive landscape, here are emerging approaches she highlights:

• New dye lines. Chemical manufacturing company Huntsman created Avitera, a line of dyes for cotton that readily bonds to the fiber. This, the company says, requires one-quarter to one-third less water and one-third less energy than traditional dyes.
• Cotton pretreatment. Startup ColorZen developed a cotton pretreatment step that allows raw cotton fiber to get treated right from the field. The company’s technical director told Bomgardner that this process speeds up the dyeing process while using 90% less water, 75% less energy, and 90% fewer auxiliary chemicals. “It also cuts out almost half the dye compared with processes that call for salts in the dye bath,” she wrote.
• Pre-reducing indigo. “Synthetic indigo, used to make blue jeans blue, is an example of a dye that can release unreacted chemicals downstream of manufacturing,” Bomgardner wrote. In response, color chemical company Archroma developed a technology for pre-reducing indigo to prevent the chemical aniline from getting through as a contaminant.
• Engineered microbes. Several startups are working on engineering microbes to reduce the use of chemicals in textile dyes. UK-based Colorfix, for example, is piloting a process where genetically modified microbes produce stable colors.
• Digital textile printing. “The major portion of water used for textile dyeing comes after dyeing, when fabrics, particularly cotton, have to be washed over and over again to remove unfixed dye,” Bomgardner points out. “Instead, manufacturers can skip dyes and use pigments.” Intech Digital, for instance, makes large-scale printers that use special versions of ink-jet printheads designed to work with textile inks.

Besides these dyeing methods, other solutions are coming to the fore. “Even the best pretreatment process can’t eliminate the health effects of the dyes and the chemicals used to make them,” Bomgardner wrote. “That’s the focus of many of the textile industry’s eco-certification programs.” Oeko-Tex certification for certifying nontoxic textiles now looks at more than 300 chemicals — up from 100 initially, she notes.

Denim makers in particular have long been under pressure to change their processes. Earlier this year, Levi’s detailed a operating model pilot called Project Future-Led Execution that cuts chemicals from the finishing process and shortens the time to market. Dutch denim-maker G-Star Raw also took a hard look at their supply chain and launched what they call “the most sustainable jeans ever.”