Denim jeans folded up

An eco-friendly method for dyeing jeans

Image credit: Andrew Davis Tucker/UGA

Researchers in the US have developed new indigo dyeing technology that, they say, is an eco-friendly alternative to current methods.

Dyeing denim jeans is one of the top sources of pollution within the fashion industry. That is why researchers from the University of Georgia (UGA) developed a new indigo dyeing technology that’s kinder to our planet.

According to the researchers, the technique reduces water usage and eliminates the toxic chemicals that make the dyeing process so environmentally damaging. The technology also streamlines the process and secures more colour than traditional methods.

“The textile industry is a classic example of an environmental polluter, and one of the major causes of pollution in the industry is colouration,” said Sergiy Minko, a professor of fibre and polymer science at UGA and a corresponding author of the study.

Originally, natural indigo was used to dye textiles. Introduced to the Colonies in the 1700s, indigo was an important cash crop for early America. But the discovery of a way to produce synthetic indigo almost entirely wiped the natural indigo market off the map, according to experts.

Indigo, however, isn’t water-soluble and has to be reduced with toxic chemicals before it can be used to dye clothing. The denim industry uses over 45,000 tons of synthetic indigo a year, along with over 84,000 tons of sodium hydrosulphite as a reducing agent and 53,000 tons of lye.

Experts have said it takes between 50 to 100L of water to dye just one pair of jeans. And that water, chock-full of toxic chemicals, has to go somewhere. Although there are now regulations in place requiring US plants to purify that wastewater, the industry simply released it into the environment for decades, corroding sewage pipes on its way to rivers and the ocean.

According to experts, even now, chemical-contaminated water inevitably winds up in local waterways, particularly in the industrial factories in developing nations where production is frequently outsourced.

Different types of jean samples with dye

(1) A piece of damp cloth after it was dyed using the novel eco-friendly method developed by UGA. (2) After the cotton is dyed, it dries for an hour, resulting in this uniform blue piece of fabric. (3) The fabric then goes into a post-dye bath followed by processing and drying time, resulting in this finish.

Image credit: University of Georgia

The new method of dyeing uses natural indigo (though the streamlined process could also use synthetic) and eliminates the harmful chemicals used in conventional methods. It also requires only one coat of the indigo to secure over 90 per cent of the colour, significantly reducing the amount of water needed to dye the fabric. Conventional methods require up to eight dips in the dye solution and secure only 70-80 per cent.

According to the researchers, the method doesn’t sacrifice comfort either, keeping around the same levels of thickness, weight gain, and flexibility in the fabric. Because of the streamlined process, it saves workers time and energy by eliminating the need for multiple dips and oxidation time between each dip, they added.

“You don’t reduce the indigo in this process; you don’t dissolve it,” Minko explained. “You simply mix it with nanocellulose fibrils and deposit it on the surface of the textile. And you can change the shade of blue by the number of indigo particles added in the mixture.”

Nanocellulose is a recent creation made from wood pulp like that used in the paper industry. The new technology mixes indigo particles with the nanofibres and then deposits them on the surface of the textile, essentially 'glueing' the colour in place.

New dyeing method

The new dyeing method can be used to create a variety of shades by varying the indigo formula.

Image credit: University of Georgia

The textile industry has long been known as one of the world’s most significant sources of pollution. And in the 20th century, when the world’s population skyrocketed, so did the need for mass-produced textiles, making the already bad pollution problem escalate.

Although the technology still needs to be commercialised, the researchers believe that it’s a viable option for making the denim industry more sustainable.

“Denim and jeans manufacturing is a big market, so even minor 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.”

Many well-known brands have already released ranges that showcase sustainability. For example, Swedish-based Nudie Jeans started this some years ago. For every product it makes, the company lists every manufacturer involved in the entire chain on the website, naming the factories, how many employees work there, etc. Buyers can also trace the cotton used in the jeans back to the farm it came from.

American clothing company Levi’s has also recently launched its own similar transparency approach for a special greener range of products. For example, in 2019, the firm introduced its 2025 Water Action Strategy, which aims to reduce water use in manufacturing by 50 per cent in water-stressed areas by 2025. It also aims to reduce greenhouse gases in its owned-and-operated facilities and 40 per cent in its entire supply chain by the same year.

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