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Sustainable dyeing innovations: Greener ways to color textiles
Humans have been coloring fabric for millennia. The earliest record is traced back to 3500 BC. Up until 1856, when WH Perkins discovered the use of synthetic dyes, all dyes were made with natural pigments and oils. Now, 90% of our clothes are dyed synthetically.
The Dyeing Industry Has a Problem
There are many problems with current textile dyeing and treatment practices, and almost all of them are related to excess water consumption and pollution. Dyeing cotton is particularly water-intensive, as it is estimated that dyeing and finishing can use around 125 liters of water per kilogram of cotton fibers. Not only does dyeing require huge volumes of water, it also relies on huge amounts of energy to heat up water and steam that is necessary for the desired finish.
About 200,000 tons of dyes (worth 1 billion USD) are lost to effluent due to inefficient dyeing and finishing processes (Chequer et al., 2013). This means that current dyeing practices are not only wasteful of resources and money, but also release toxic chemicals into freshwater sources. 60 to 80 percent of all dyes are AZO dyes, many of which are known to be carcinogenic. Chlorobenzenes are commonly used to dye polyester, and are toxic when inhaled or directly in contact with skin. Perfluorinated chemicals, formaldehydes and chlorinated paraffin are used in finishing processes to create waterproofing effects or flame retardance, or to create easy-care fabrics.
As more consumers become aware of the harmful effects of current dyeing practices, new technologies make way for more cost-effective, resource-efficient and sustainable dyeing alternatives. Innovation in dyeing technologies ranges from pre-treatment of cotton, pressurized CO2 dye application, and even creating natural pigments from microbes. Current dyeing innovations can help reduce water usage, replace wasteful practices with efficient and cost-effective ones and attempt to completely transform the way in which we create the pigments that give our clothing the beautiful colors we love.
Waterless Technologies for Sustainable Dyeing
The dyeing process of textiles varies depending on the type of fabric. Cotton dyeing is a longer and more water and heat-intensive process, due to the negative surface of cotton fibers. This means that usually cotton only takes up about 75% of the dye that is used. In order to make sure color holds, dyed fabric or yarn is washed and heated over and over again, producing huge amounts of wastewater. ColorZen uses a patented technology that pre-treats cotton before it is spun. This pretreatment makes the dyeing process faster, reduces 90% of water usage, 75% less energy and 90% less chemicals that would otherwise be needed for effective dyeing of cotton.
Dyeing synthetic fibers, such as polyester, is a shorter process and 99% or more dye fixation (99% of the dye that is applied is taken up by the fabric). However, this does not mean that current dyeing practices are more sustainable. AirDye uses dispersed dyes that are applied to a paper carrier. With heat alone, AirDye transfers dye from the paper to the textile’s surface. This high heat process colors the dye at a molecular level. The paper that is used can be recycled, and 90% less water is used. Also, 85% less energy is used because the textiles do not need to be soaked in water and heat dried over and over.
Sustainable Dyeing is Changing the Textile Industry
DyeCoo uses CO₂ to dye textiles in a closed-loop process. “When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily. Thanks to the high permeability, the dyes are transported easily and deeply into fibers, creating vibrant colors.” DyeCoo does not require any water, and they use pure dyes with 98% uptake. Their process avoids excess dyes with harsh chemicals and no wastewater is created during the process. They have been able to scale up this technology and have commercial endorsements from both textile mills and end-users.
Pigments from Microbes
Most of the clothing we wear today is colored using synthetic dyes. The problem with these is that valuable raw materials, such as crude oil are needed during production and the chemicals added are toxic to the environment and our bodies. Even though natural dyes are less toxic than synthetic dyes, they still require agricultural land and pesticides for the plants that made up the dyes.
Labs across the world are discovering a new way to create color for our clothing: bacteria. Streptomyces coelicolor is a microbe that naturally changes color based on the pH of the medium it grows inside. By changing its environment, it is possible to control what type of color it becomes. The process of dyeing with bacteria begins by autoclaving a textile to prevent contamination, then pouring a liquid medium filled with bacterial nutrients over the textile in a container. Then, the soaked textile is exposed to bacteria and is left in a climate-controlled chamber for a couple of days. The bacteria is “live dyeing” the material, meaning that as the bacteria grows, it is dyeing the textile. The textile is rinsed and gently laundered to wash out the smell of the bacterial medium, then let to dry. Bacterial dyes use less water than conventional dyes, and can be used to dye many different patterns with a vast range of colors.
Faber Future, a UK-based lab, is using synthetic biology to program the bacteria to create a large range of colors that can be used to color both synthetic and natural fibers (including cotton).
Living Colour is a biodesign project based in the Netherlands that is also exploring the possibilities of using pigment-producing bacteria to color our clothes. In 2020, Living Colour and PUMA teamed up to create the first-ever bacterial dyed sports collection.
Werewool is taking inspiration from nature to produce colorful textiles that come from proteins. One of these proteins is from Discosoma Coral which produces a bright pink color. The DNA of this protein can be copied and placed into bacteria. This bacteria can then be woven into a fiber to make colored fabric.
We aRe SpinDye dyes recycled materials from post-consumer water bottles or wasted clothing before they are spun into yarn. Their technology melts color pigments and recycled polyester together without the use of water, which reduces overall water usage by 75%. In recent news, H&M has used We aRe SpinDye®’s dyeing process in their Conscious Exclusive collection.
huue. makes sustainable, biosynthetic indigo blue meant for the denim industry. Their technology does not use petroleum, cyanide, formaldehyde or reducing agents. This eliminates massive amounts of water pollution. Instead of using toxic chemicals, huue. uses sugar to make dye. They use proprietary bioengineering technology to create microbes that mirror nature’s process and consume sugar to enzymatically produce dye.
Future Challenges
In order for the mentioned startups and technologies to thrive and scale up to a commercial level, it is imperative that we drive investments and partnerships between these smaller companies, and larger existing fashion and chemicals companies.
It is impossible for new technologies to become economically viable options that fashion brands will adopt without investment and partnerships. The collaborations between Living Colour and PUMA, or SpinDye® and H&M are just two of the many necessary alliances that must continue if companies are genuinely committed to shifting towards sustainable dyeing practices that save precious resources and stop polluting the environment.
Source:
https://www.plugandplaytechcenter.com/resources/how-sustainable-dyeing-changing-textile-industry/ By Sofia Willis
