The world's trusted guide to sustainable and ethical fashion

The world's trusted guide to sustainable and ethical fashion


The Most Exciting New Sustainable Dye Technologies

Photo: Pangaia using Officina+39 recycled dye technology

A big part of fashion is expression, and colors and prints play a huge role in conveying the message. The global coloration market employs a fair share of the fashion industry. It closed in on 6 billion USD in gains by the end of 2022 and is expected to grow to 8 billion USD by 2031. But the industry remains relatively quiet about dyeing processes and their impact.

When we talk about dying, we actually mean all the wet processing steps, including pretreatments, coloration (dyeing and printing), and finishing. It’s also known as tier 2, with tier 1 being the cut-and-sew, tier 3 the spinning of fiber into yarn in fabric mills, and tier 4 the extraction or farming of raw materials. 

Despite its huge size, it is difficult to measure how much water the fashion industry really uses, let alone for tier 2 manufacturing specifically. Different machines need different amounts of water to get the same fabric dyed properly, with studies proposing anywhere from 5 to 5,000 liters per kilo of fabric. 

For example, a winch machine uses over three times as much as a jigger, which in turn scores worse at fixing the dyestuff. Polyester requires less water but is more energy intensive to produce, thereby contributing to global warming from harmful greenhouse gases.

Bottom line is that conventional dyeing is a fairly wet process resulting in oddly-colored wastewater that is contaminated with hazardous chemicals such as chloride, sulfate, and nitrate. Without proper cleaning, this water cannot be put back into the loop, and disrupts ecosystems, increasing the need for scarce freshwater. Most innovations aimed at reducing water tackle common washing, dyeing, and printing practices.

But it’s not just water. According to a report from the World Resources Institute (WRI) and Apparel Impact Institute (Aii), tier 2 makes up 52% of all greenhouse gas emissions in the fashion supply chain (excluding footwear), equaling 536M tons of CO2e per year. These numbers make sense if you consider the need to heat the water baths, clean the tanks, and run and cool heavy machinery such as printers.

The third big impact area is chemistry. The chemicals added during processing are almost always derived from petroleum. To make dye for cotton, for example, a substantial amount of salt—needed to help increase the textile’s affinity for the dye—is enriched with a long list of hazardous chemicals such as dyestuffs and softening agents. These pollutants often remain in the water as it flows into the local waterway, where they cause all sorts of harm such as killing fish and other aquatic life. The polluted water streams often leave locals with zero access to clean water, leading to a long list of infections and diseases. The same goes for factory workers that work above toxic steam baths, which have been linked to a variety of human diseases. 

The industry group ZDHC has created a list of banned chemical substances (called a manufacturer restricted substance list, or MRSL) that claims they are undetected in 98% of the wastewater issuing from the pipes of suppliers of its member brands, which includes Inditex, LVMH and Kering. However, this is a voluntary program and doesn’t cover the majority of the fashion industry when it comes to sheer volume. 

The Dyeing Process From Prep to Finish

To understand the most exciting innovations, you first need to understand the process. No dye works on all textiles and no textile works with all dyes. Moreover, the steps are highly dependent on fiber type.

Processing starts with getting the material prepared to make the dye stick. The goal of pretreatments such as de-sizing, scouring, and bleaching is to clean the fibers and get them ready to take up the dyestuff. The fabric gets thrown into water baths that are heated up to a certain temperature and dipped into the mix several times to get the dye fastness brands are looking for. After washing and drying, the final stage finishes the dyed fabric with special treatments—usually applied with rollers— depending on its intended end use. Mercerization, for example, makes cotton stronger, more absorptive, and more lustrous. Other examples are softening, antistatic agents and durable water repellent finishes.  

What are the most promising innovations?

MTIX technology

Innovators are looking at alternatives for the traditional “water bath” approaches. These technologies move coloration from wet to dry processing and are meant to influence steps further down the line. A more efficient pretreatment makes it easier to get the dye to stick, which in turn reduces the need of additional water and chemistry. And waterless dyeing reduces the need for expensive waste treatment systems. 

What they have in common is reduced emissions, water use, and chemistry due to smarter applications, creating win-win saving opportunities for companies and the natural environment.

Plasma

Plasma is something in between liquid and gas and can replace the usual chemistry used to clean the surface of textiles, banishing water from the process and reducing the energy needed. Italy-based GRINP claims to be the only innovation company that offers this machinery on an industrial scale. A similar water and energy reduction is possible with lasers, which precisely apply the dyestuff.  In the spring of 2022, a company from Yorkshire called MTIX licensed their laser equipment for the first time to materials science company and fashion brand PANGAIA in April 2022. They are still testing the technology.

Ultrasonic, Foam, and Nozzle Dyeing

With an eco-punk-sounding name, ultrasonic comprises a big chunk of the next-generation coloration machines. It works with microscopic bubbles that burst and apply the dye onto the fabric. Foam dyeing by companies like Indigo Mill Designs does the same using bursting foam bubbles. There is also digital spray dyeing, whereby fabric rolls through a machine with very accurate sprays and nozzles. This process is once again waterless. It still requires energy to run those machines, but overall, it has significant reductions. H&M has invested in UK-based innovator Alchemie in pursuit of 50% cost savings in the dying process.

Supercritical CO2

Supercritical CO2 works by increasing and decreasing the pressure in the dyeing vessel. When it pressurizes, supercritical CO2 converts from its gas state to liquid, which applies the dye onto the fabric. It creates so much power that chemicals traditionally needed to dissolve the dyes are no longer required. The CO2 only needs to be purchased once, as it can be recycled after each dyeing cycle. Companies like eCO2Dye and DyeCoo work on this, but, “It will be longer before you see a thing like that in the market,” explains Fashion for Good Innovation Platform Director Georgia Parker. DyeCoo, which claims that its technology has a 98% dye uptake and is scalable and commercializable, has been working on its solution for over 15 years now. 

Dope Dyeing/Solution Dyeing

Dope or solution dyeing is an incremental solution that has already entered the market. When you dope-dye polyester, you add the dye simultaneously with the melt spinning of the PET pellets. However, many companies don’t want to decide on their colors that early on, and it requires large minimum orders of fabric, so it only works for classic shades that are never out of style. According to the Higg Materials Sustainability Index, dope dyeing of synthetic fibers results in over 90 percent fewer emissions than batch dyeing.

Digital & Gravure Printing 

For some application processes, printing is more effective than dyeing. This is where digital printing and gravure printing come in. The former is direct on-demand printing, whereas the latter involves ink-filled cells put on a cylinder and then transferred onto the fabric. These digitally controlled processes are very precise, which is perfect for complex prints. NTX, for example, developed a heatless process to apply artworks, while Alchemie digitally sprays the entire fabric. Adidas announced a partnership with Alchemie in March 2022.

Enzymatic

On the chemistry side of things, enzymatic pretreatments are about to replace synthetic chemical treatments. It’s a form of “white biotechnology”, which means that living organisms and enzymes help create products in a way that is affordable and reduces waste. A German study even showed that enzymatic pretreatments can give cotton better properties, such as extra tensile strength. 

Cationic

Cationic treatment innovators such as Nano Dye work on salt-free techniques that give cotton a constant positive (cationic) charge, which leads to a better, faster dyestuff uptake. It can only be used for fibers with a high cellulose content, however—a reminder that most of these solutions are not one-size-fits-all.

Natural Pigments

Biobased dyes are made from organic inputs to replace synthetic dyes. Most denim today, for example, is dyed using synthetic indigo, which requires toxic and dangerous chemical inputs. Stony Creek Colors in Tennessee combines a modern processing technique with specially-bred indigo plants to create a factory-ready indigo dye. They’ve partnered up with Levi’s to sell plant-based-indigo-dyed denim together by the end of this year. Chinese IndiDye uses plants as well to create their colors, and Nature Coatings in LA uses wood waste. 

As great as it sounds, natural pigments are not perfect. Despite significant improvements, their performance is still not equal to synthetic dyes, in terms of color fastness, color availability, reliability, durability, and purity. Furthermore, bio-based dyes may be extracted from animal and vegetable resources, but you still need to bond it to the fabric with so-called mordants. They contain metallic compounds to prevent fading, which prevents biodegradability and can come with their own set of toxicity challenges. Plus, at the scale of fashion production today, it’s possible we could not produce enough natural feedstock to satisfy the fashion industry’s dye needs without severely exploiting the earth’s resources.   

Microbial pigments

Living Ink has printed tees for Nike using black algae ink—a great example of microbial pigments. As Parker of Fashion for Good explains, microbial pigment is not just about growing a plant and getting the dye out. You identify the color for a strain of bacteria (like microalgae), feed them sugars to get them to grow, and finally extract that (black) pigment. It’s more like a bio-fabrication process.

Upcycled carbon

Nike also works with Graviky, an MIT spin-off that creates dyes from upcycled carbon emissions. They claim to capture carbon—as a byproduct—from factories, cars, and more to store and recycle it into usable carbon to produce ink. 

Recycled

Recycled dyes have recently started to enter the commercial market, most notably from the Italian firm Officina+39 with its Recycrom dyestuff, made from discarded textiles that have been ground into a fine powder. It can be applied on many different types of textiles, including nylon and wool. PANGAIA just launched a range of pastel-colored hoodies dyed with transformed textile scraps from its own factory floor.

Why are processing developments within the industry so slow?

Most of the solutions and technologies I’ve described are not off-the-shelf solutions that you can buy and pour into your dyehouse vats as simply as synthetic dyes. Dye houses still need to test each technology to assure themselves that it works and to the satisfaction of budget-conscious and exacting fashion brands. But according to Parker, sustainable dye alternatives have seen their performance improve tremendously. “10 years ago, it was all earthy colors,” she says. “Now, we’re starting to see some of the more commonly used colors, like blue, red, yellow, and black coming through.”

The challenges, in a nutshell, are technology validation, expensive machines, and scaling up the technology. Only a few companies hold the patents. Innovative manufacturers need to know that if they invest in these new machines, brands will buy the end product…even if it costs a few cents more. Initial investments are high, but for some of these technologies, the cost per unit over time can be lower because of water, energy, and chemistry savings. 

The fact that this innovation area is medium-cool when it comes to buzz doesn’t help. “Material design is an integral part of a brand’s DNA,” Parker explains. Up until the last couple of years, Parker says it wasn’t seen as a sexy topic. “There were incremental innovations that were taking place. I think it’s only recently that brands are like, oh actually there’s a market opportunity for us here.”

To reach net zero emissions by 2050, part of those reductions needs to come from incremental, existing solutions like water-saving measures, including reusing water, a shift to renewable energy, and efficient machines that combine processes to save energy and water. The remaining part will need to come from these new innovations.

We have the sustainable technology. The next step is to figure out how to get brands to recognize the value of investing in it. 

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