Focused on plant, plant waste and bacterial-based dyestuff, Sodhani Biotech provides textile mills worldwide with a vast selection of commercially available and sustainable dyes. The company uses a biological process to fix pigment onto textiles. The plant-based dyes are suitable for cotton, wool, silk, polyester, nylon and other fibers. Compared to manufacturing synthetic dyes, the company’s carbon footprint is about 60% lower. Photo: Sodhani Biotech Pvt. Ltd.

The amount of water used and polluted in textile production is staggering. According to the United Nations Environment Programme, around 20% of all wastewater worldwide comes from fabric dyeing and treatment. Dyehouses in India and China are notorious for not only exhausting local water supplies but dumping untreated wastewater into local streams and rivers.

But as the planet becomes warmer and drier, water conservation has become a major concern for countries around the globe. This industry’s considerable environmental impact can no longer be ignored, and calls for change all along the supply chain are ringing loudly. In response, various providers of fibers and fabrics are exploring ways to significantly reduce the water used during the dyeing process. Some have managed to eliminate the need for water altogether while others are investigating how to create more earth-friendly dyes. In the following, we explore what some of these companies are doing to not only minimize their environmental footprints but also help drive this industry toward a healthier and more sustainable future.   

Turning to nature

A recognized startup by the government in India, Sodhani Biotech Pvt. Ltd., headquartered in Jaipur, Rajasthan, India, is a research facility and marketing company focused on using herbal extraction and downstream processing to obtain dyestuff from plants, plant waste and microorganisms. The company provides textile dyeing mills worldwide with a vast selection of commercially available, sustainable dyes and works with top textile brands, says Sidhant Sodhani, director/CEO. The company’s natural dyes are exported to more than 20 countries, and it was among the top Fashion for Good Innovators in that organization’s Asia Innovation Program.

“The process of extraction is usually designed to maximize a certain portion of the original chemical compounds found in the plant, whereas downstream processing is used to separate colors from cells produced by bacteria,” Sodhani explains.

Sodhani Biotech’s plant-based dyes seem to work on multiple fiber types, with the company trying them on cotton, wool, silk, polyester, nylon, leather, rayon and viscose. The bacteria-based dyes are more limited in application.

Sodhani says these natural dyes offer several advantages to manufacturers, such as a carbon footprint that is about 60% lower. Additionally, the sludge remaining at the end of the process can be used to produce fully biodegradable vermicompost. And while regularly coming into contact with synthetic dyes can lead to health issues such as skin allergies, most natural dyes are inherently antibacterial and unlikely to cause these reactions.  

All manner of plants, fruits and vegetables serve as the sources of Sodhani Biotech’s natural dye powders. These include madder root, onion skins, Indian rhubarb root, the fruit of the haritaki plant, pomegranate peel and various woods, tree barks, seeds and more. Natural dyes require significantly less water treatment post-production compared to synthetic dyes. Photo: Sodhani Biotech Pvt. Ltd.

Measured against synthetic dyes, the natural-dyeing process doesn’t save much energy, he says, but there are other areas where the differences are significant, such as the post-dyeing discharge of clean water.

“This is a bigger challenge for dyeing companies,” he says. “Natural dyes have around 90% lower COD/BOD [chemical oxygen demand/biochemical oxygen demand] values compared to synthetic dyes, which brings down water treatment post-dyeing by around 80%–85%. We don’t have an absolute number on how much energy is saved during this process, but it should be somewhere between 50%–70% lower compared to synthetic dyes.” 

Sodhani asserts the demand for more sustainable dyes and processes will only increase as sustainability plays an ever-expanding role in the agendas of governments around the globe. Until now and unlike other industries, textiles have slipped under the radar despite their potentially far greater environmental impact. However, he cautions, this could change.

“Once the focus is on textiles, which I am sure it will be soon, companies will be expected to act faster and reduce their carbon footprints at a much higher pace,” Sodhani warns.

A waterless dyeing and printing technology, NTX® Cooltrans® from NTX is designed to directly transfer dosages of color onto precise spots in the fabric and fix it upon that spot. The process uses a proprietary ink chemistry based on nontoxic dyes. Water savings via the Cooltrans technology can reach up to 90% compared to traditional immersion coloration methods. Energy savings can be as high as 65%. Photo: NTX

Coloration and fixation technology

Specializing in developing waterless coloration technology, Singapore-based NTX® partners with major global brand houses helping them attain their sustainability goals, says Jeffrey Hsu, chief innovation and marketing officer. The company’s waterless dyeing and printing technology, NTX Cooltrans®, is able to colorize nearly any fabric accurately and precisely, doing so while reducing water use by 90%, dye use by 40%, and realizing up to 65% in energy savings all without compromising colorfastness, hand feel and functional performance.

The company’s founders originally researched ways to improve sublimination but eventually realized further refinements weren’t possible “without breaking the laws of physics and chemistry,” Hsu says.

“The biggest issue to overcome was how to consistently and efficiently transfer color onto the many types of fabrics that exist in the industry—from woven, nonwoven, knits, to polyester or other synthetic fibers,” he explains. “The next step was to come up with a novel ink chemistry and then develop the machinery to efficiently execute colorization and fixation.”

The proprietary ink-based solution used by the NTX® Cooltrans® waterless dyeing and printing technology works on knit and woven fabrics and on natural, man-made and synthetic fibers, producing an array of colors, patterns and textures. Photo: NTX

The result, years in the making, was NTX Cooltrans, which now serves as a Tier 2 fabric supplier to the global brand houses.

The process, which works on knits and woven fabrics composed of natural or synthetic fibers, is an ink-based solution using the company’s proprietary ink chemistry. The ink is based on nontoxic dyes and is applied via the NTX Cooltrans coloration and fixation machinery.

There is an initial cost to implement the technology, Hsu says, but this can be recouped through energy use reduction, savings on dyes and savings due to the elimination of waste because of NTX Cooltran’s accuracy.

Interest across the industry is high, Hsu says, propelled by growing numbers of consumers focused on sustainability, rising energy costs and new government regulations as well as from those casting a watchful eye on the industry.

“The textile industry, and specifically the fast-fashion industry, has been one of the world’s largest consumers of fresh water and contributors to greenhouse gas emissions,” he says. “Water is becoming increasingly valuable, and water efficiency is going to become an ever more important factor in manufacturing processes.”

DyeCoo’s patented waterless dyeing technology uses reclaimed and pressurized CO2 to create supercritical scCO2, turning it into an highly effective solvent that allows dyes to dissolve naturally. The process creates long-lasting and dazzling colors, as shown on this image of the package dyeing machine spindle. Photo: DyeCoo Textile Systems B.V./DyeCoo North America

Reclaiming CO2

Located in Weesp, Netherlands, DyeCoo Textile Systems B.V. offers a 100% water-free process and chemical-free textile dyeing solution, says Patrick Vinson, owner of Regent Textile Machinery Canada Ltd. in Montreal, Que., Canada, which represents DyeCoo in North America. Customers are composed of fabric suppliers and dyehouses providing yarns and fabrics to various markets like performance apparel, sportswear and more, says Vinson. Currently all of the company’s customers operate out of Vietnam, Taiwan, Thailand, South Korea, Türkiye, Europe and the United States.

Rather than water, DyeCoo’s patented technology is based on using reclaimed CO₂ “as the dyeing medium in a closed-loop process,” he says.

“When pressurized, CO₂ becomes supercritical [scCO₂],”  Vinson explains. “In this state CO₂ becomes an excellent solvent, allowing the dye to dissolve naturally. Thanks to the gas-like low viscosity of scCO₂ and molecular dissolved dye molecules, the dyes are transported easily and deeply into the fibers, creating vibrant colors with outstanding exhaust and superior fastness properties.”

The process uses 100% pure dyes, he continues, and doesn’t require added dispersing agents or process chemicals to dissolve them. Consequently, there’s no wastewater. DyeCoo reclaims the CO₂ from existing industrial processes and is “part of the circular economy,” Vinson says, adding that because of the closed loop system, DyeCoo is able to recycle 95% of the scCO₂. 

The dyes and the materials to be processed are placed into machines, dubbed DyeOx4. Each contains three dyeing vessels and all of the equipment necessary to process the CO₂. Once loaded, the CO₂ is added. The temperature and pressure are increased to create the scCO₂. 

Shown here are DyeOx4 machines from DyeCoo installed in a factory in Ho Chi Minh City, Vietnam. The CleanDye factory is dedicated to 100% waterless dyeing with scCO2. The technology transports dyes easily and deeply into the fibers without requiring added dispersing agents or process chemicals to dissolve them. This process uses 100% pure dyes and recycles 95% of the CO2, resulting in considerable reductions in water usage. Photo: DyeCoo Textile Systems B.V./DyeCoo North America

“Our vessels operate under higher pressure than conventional dyeing machines, but the concept resembles beam dyeing,” Vinson explains. The technology has proven effective for dyeing a variety of polyester yarns and fabrics constructed with a wide range of permeability, he says, adding that DyeCoo works with a dye manufacturer that supplies the dyes for the CO₂ process.

Each vessel operates independently, he continues.

“It’s been designed this way because of the back-end heating and supply. It’s very modular. Installation takes only five to seven days. This process can be integrated into most dyehouses and is compatible with existing machines for preparation and finishing. However, projects we are currently working on are tailored to an existing plant that operates 100% of its production with CO₂.”

The reduced footprint of an scCO₂ dye plant results in significant savings since there’s no need for wastewater treatment or for any process chemicals. The ability to recycle nearly all of the scCO₂ used in the dye cycle further contributes to the savings.

According to Vinson, major brands and retailers sourcing more fabrics dyed by the scCO₂ process are causing volumes to climb—activity he expects will continue.

“The market continues to grow as consumers become more informed about the impacts of water usage in the textile industry,” he says. “The scCO₂ process can reduce water usage in the dye cycle up to 7 gallons per pound (60 l/kg). This is a considerable reduction of water usage when it seems likely that our behavior regarding this precious resource must change and rather quickly.” 

Pamela Mills-Senn is a Seal Beach, Calif.-based freelance writer.

SIDEBAR: Supporting disruptors

One problem facing the textile industry is that so much of the effort directed at sustainability is taking place in isolation, says Jana van den Bergen, innovation associate for Fashion for Good. Headquartered in Amsterdam, Netherlands, the company seeks to remedy this situation by providing a global innovation platform.

“Fashion for Good unites the entire ecosystem, from brands, manufacturers and suppliers, to consumers, to collaborate and drive the change towards a circular industry,” van den Bergen says. “At the core of Fashion for Good is its Global Innovation Program.”

Designed to support “disruptive innovators” in their attempts to devise and scale new sustainable solutions, that program provides hands-on project management and access to funding as well as to mentors and experts. Fashion for Good also brings together consortiums of innovators, brands, manufacturers and funders via its Foundational Projects. 

“We are currently supporting various almost-waterless dyeing technologies with scaling,” says van den Bergen. “We do this through our Innovation Program and D(R)YE Factory of the Future Project. Multiple mostly waterless dyeing technologies, like Alchemie, Imogo, NTX Cooltrans have been part of our innovation program and/or are part of the D(R)YE Factory Project.”

Through Fashion for Good, the project also partners with a variety of brands, such as adidas, Kering and PVH Corp. 

“To achieve greater impact and accelerate the shift to more sustainable practices, this project, initially focused on innovations in pretreatment and coloration, partners several innovations together to test their solutions in combination to validate their impact and potential to scale in the fashion value chain,” van den Bergen says.

These Tier 2 processes—pretreatment, coloration and finishing—typically consume huge amounts of energy, heat and water, sending volumes of toxins into the water and producing “the highest amount of greenhouse gas [GHG]  emissions, 52%,” she says. Moving from wet processes to mostly dry/waterless is key to reducing this impact.

“This shift has the potential to reduce Tier 2 emissions by between 79%–89%  and could slash over a quarter of total GHG emissions in the industry,” van den Bergen says. “An equal opportunity exists to reduce water consumption, including savings of up to 83% in pretreatment and 95% in dyeing.”

Source link