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Researchers Develop Chemical-Free One-Coat Indigo Dye Process

As the denim industry shifts to become more sustainable, technicians are making strides in developing safer dyeing solutions. One of the latest innovations comes from researchers at the University of Georgia, who recently discovered a process for dyeing denim that rids it of harmful chemicals while simultaneously boosting efficiency.

The research was published in the Green Chemistry Journal, and is a part of the Ph.D. study of Smriti Rai, a doctoral candidate in the university’s department of textiles, merchandising and interiors.

Though conventional denim dyeing methods involve reducing indigo with toxic chemicals prior to dyeing, the new process completely eliminates the use of harmful chemicals by mixing it with nanocellulose fibrils—wood pulp—and depositing it on the surface of the textile. It essentially “glues” the color in place, making multiple coats and excessive water usage unnecessary.

The study showed that just one coat of the indigo secures over 90 percent of the color, while conventional methods require up to eight dips in dye solution to secure between 70 to 80 percent. Shades of blue are determined by the amount of indigo particles used.

According to the study’s corresponding author Sergiy Minko, the industry’s $90 billion valuation means even seemingly minor strides in sustainability can translate to big environmental improvements.

“Denim and jeans manufacturing are a big market, so even small changes in the industry could have huge impacts,” Minko said. “There are populations that are looking for products that are made in environmentally friendly ways. And as regulations become tougher, the industry will have to adapt.”

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Though indigo gives denim its signature blue hue, it considered to be one of the industry’s biggest sources of pollution. Biotech startup Huue found that indigo manufacturing produces more than 1.4 million metric tons of CO2 and utilizes toxic chemicals like benzene, formaldehyde and sodamide, which can be harmful to the environment and people.

In fact, a report from Water Witness International (WWI), a U.K.-based organization focused on sustainable water resource management, found evidence of water pollution in certain African countries that support the global fashion supply chain. River flow was tainted with pH comparable to household bleach and a blue coloration reflective of nearby production sites.

Rai’s research, however, is one of several examples of ways the indigo supply chain might have a greener future.

Other sustainable dye improvements include using lab-grown bacteria to create an indigo dye void of chemicals—a concept used by Huue. Recently, the company partnered with biotech firm Ginkgo Bioworks, Inc. to scale production of the sustainable indigo dye.

Similar innovations have caught the eye of investors across various industries. Earlier this year, Stony Creek Colors, a U.S.-based natural indigo supplier, secured a $9 million Series B financing round for its BioPreferred-certified plant-based indigo that’s free of hazardous chemicals.