An ecological method for dyeing jeans
Researchers in the United States have developed a new indigo dyeing technology that they say is an environmentally friendly alternative to current methods.
The dyeing of denim jeans is one of the main sources of pollution in the fashion industry. This is why researchers at the University of Georgia (UGA) have developed a new indigo dyeing technology that is more respectful of our planet.
According to the researchers, the technique reduces water consumption and removes toxic chemicals that make the dyeing process so damaging to the environment. The technology also streamlines the process and secures more colors than traditional methods.
“The textile industry is a classic example of an environmental polluter, and one of the main causes of pollution in the industry is coloring,” said Sergiy Minko, professor of fiber and polymer science at UGA and author. correspondent 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 finding a way to produce synthetic indigo has almost wiped the natural indigo market off the map, experts say.
Indigo, however, is not water soluble and must be reduced with toxic chemicals before it can be used to dye clothes. The denim industry uses over 45,000 tonnes of synthetic indigo per year, as well as over 84,000 tonnes of sodium hydrosulphite as a reducing agent and 53,000 tonnes of lye.
Experts said it takes between 50 and 100 liters of water to dye a single pair of jeans. And this water, full of toxic chemicals, has to go somewhere. While there are now regulations in place requiring US factories to purify this wastewater, the industry has simply released it into the environment for decades, corroding sewer lines en route to rivers and the ocean. .
Even now, water contaminated with chemicals inevitably ends up in local waterways, especially in industrial factories in developing countries where production is frequently outsourced, experts say.
The new dyeing method uses natural indigo (although the streamlined process can also use synthetic) and removes harmful chemicals used in conventional methods. It also only requires one coat of indigo to get over 90% of the color, which greatly reduces the amount of water needed to dye the fabric. Conventional methods require up to eight dips in the dye solution and provide only 70 to 80 percent.
According to the researchers, the method doesn’t sacrifice comfort either, keeping roughly the same levels of thickness, weight gain, and flexibility in the fabric. Due to the streamlined process, it saves workers time and energy by eliminating the need for multiple dips and the oxidation time between each dips, they added.
“You don’t reduce the indigo in this process; you don’t dissolve it, ”Minko explained. “You just have to 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 to 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 nanofibers, then deposits them on the surface of the textile, essentially to “stick” the color in place.
The textile industry has long been known as one of the most important sources of pollution in the world. And in the 20th century, when the world’s population soared, so did the need for mass-produced textiles, compounding the already serious problem of pollution.
Although the technology has yet to be commercialized, researchers believe it is 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 who are looking for products made with respect for the environment. And as regulations become more stringent, the industry will have to adapt. “
Many well-known brands have already launched ranges that emphasize sustainability. For example, the Swedish company Nudie Jeans started a few years ago. For each product it manufactures, the company lists on the website all the manufacturers involved in the entire chain, naming the factories, the number of employees working there, etc. Buyers can also trace the cotton used in jeans to the farm where it came from.
US clothing company Levi’s also recently launched its own similar transparency approach for a special line of greener products. For example, in 2019, the company presented its Action Strategy for Water 2025, which aims to reduce water consumption in manufacturing in water-stressed areas by 50% by 2025. It aims also reduce greenhouse gases in its owned and operated facilities. and 40% across its entire supply chain by the same year.
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