The Textile Dyeing Process: The Missing Piece in Cleaning Up the Dye Industry

The fashion industry is one of the world’s largest polluters. While much attention has been given to sustainable raw materials, one critical issue remains overlooked: the textile dyeing process. In our previous post, we explored how microbial and plant-based dyes have emerged as promising alternatives to synthetic dyes. However, even these eco-friendly options can’t solve the industry’s pollution problem alone. The real challenge lies in the dyeing process itself – a water-guzzling, energy and chemical intensive system that contributes to ~3% of GHG emissions, and dumps hundreds of toxic chemicals into our waterways. This trifecta of waste harms ecosystems, biodiversity, and human health and is a severe systemic problem desperately in need of a solution.

Why the Dyeing Process Is Fashion’s Hidden Environmental Disaster?

When we think of pollution in fashion, images of landfills overflowing with discarded clothes often come to mind. But the biggest environmental damage happens long before a garment reaches the store - it happens during the treating, dyeing and finishing process, contributing to ~20% of global industrial water pollution.

 The Dirty Truth: By the Numbers

• The pre-treatment, dyeing and finishing stage (Tier 2 of the fashion supply chain) is responsible for >50% of the fashion industry’s total greenhouse gas emissions - more than shipping and in some cases, raw material production combined.

• An estimated 10–50% of all dyes used do not bind to fabric and are washed away, resulting in one million tons of dye pollution entering waterways annually.

• In some mills, especially in regions with limited oversight, facilities either lack proper treatment systems or operate ones that fall short. As a result, contaminated wastewater continues to flow into rivers and oceans, threatening ecosystems and communities.

• Some treatment processes, such as bleaching, can transform dyes into more toxic compounds, including PBTA chemicals and aromatic amines, which are linked to cancer.

• The dyeing process uses enough water to fill 2 million Olympic-sized swimming pools each year.

How Dyeing Process Works and Why It’s So Wasteful?

Dyeing fabric isn’t as simple as dipping it in colored water. It’s a multi-step, resource-heavy process that varies depending on fiber type (cotton, polyester, wool, etc.), but the core steps remain the same.

Beyond aesthetics, consumers demand colorfastness - expecting fabrics to resist fading from washing, sweat, or sunlight. Meeting these expectations requires dyes that bond effectively, endure over time, and remain cost-effective, but this often comes at the cost of using hazardous and toxic chemicals to achieve lasting performance.

 1. Fabric Preparation: The First Wave of Pollution

Before dyes can adhere, fabrics must be thoroughly cleaned to remove natural oils, dirt, and residues. This step alone generates toxic wastewater due to:

• Alkaline washes (using harsh detergents)

• Bleaching (hydrogen peroxide, chlorine)

• Optical brighteners (for white fabrics)

Chemicals can enter wastewater streams with little to no treatment, especially where effluent treatment is inadequate and oversight is weak.

 2. Dye Application: Where Most Waste Happens

The actual dyeing process is where the biggest environmental damage occurs. Fabrics are submerged in massive vats of chemical-laden water, often at hot temperatures,to ensure even colour absorption. However, ~30-40% of the dye never sticks.

• Silk & Wool: Rely on acid dyes, which may be chromium complexed and are often non-biodegradable and require acidic dye baths, creating heavily polluted wastewater that requires intensive treatment to prevent environmental harm.

• Cotton & Linen: Often use reactive dyes, which need high salt and alkaline conditions (using soda ash)to fix the dye to the fiber. The leftover often non-biodegradable dyes and salt make the wastewater burdensome to treat and if improperly disposed of can pollute rivers and harm freshwater ecosystems.

• Polyester: Although water use of polyester dyeing is low, extreme heat and toxic and carcinogenic carriers like volatile organic compounds or halogenated aromatics, make synthetics the worst offenders.

Even with advanced dyeing techniques, up to half of the dye may be wasted, flushed out in rinsing water.

 3. Finishing: Adding More Chemicals to the Mix

After dyeing, fabrics undergo additional treatments to improve performance:

• Waterproofing (PFAS chemicals, which are toxic and persistent)

• Wrinkle resistance (formaldehyde-based resins)

• Antimicrobial coatings (triclosan, now banned in many countries)

• Fixing agents (BPA, BPS often used for enhancing colour fastness of nylon)

Many of these chemicals are not biodegradable and toxic, lingering in the environment and negatively impacting aquatic and soil biodiversity.

The Hidden Dangers of Dye Pollution

1. The Water Contamination Crisis

Textile dyeing is a leading cause of industrial water pollution in countries like Bangladesh, India, and China, where untreated wastewater is often discharged directly into rivers and streams. The consequences are devastating:

• Fish kills (non-biodegradable dyes block sunlight, suffocating aquatic life)

• Soil contamination (toxic chemicals leach into soil making farmland toxic)

• Human health risks (cancer, skin diseases, hormone disruption from harmful chemical exposure)

 2. The Illusion of “Colorless” Wastewater

Some factories bleach wastewater to meet regulatory standards, but this doesn’t remove toxicity - it just makes pollution invisible. Chlorine treatment, for example, can break down azo dyes (cheap, versatile, and durable, representing  60-70% of global organic dye production) into aromatic amines, some of which are known carcinogens, making the treated water potentially more hazardous than before, despite appearing clean.

 3. Energy, The Overlooked Drain

Textile dyeing requires heat (130°C for synthetics) and constant energy, consuming vast amounts of electricity per facility - normally more than the daily electricity use of 50 typical U.S. homes. To meet this demand, most mills rely on coal- or gas-fired boilers, locking the industry into fossil fuel dependence and contributing significantly to global emissions.

 4. CO2, Fashion’s Climate Cost

The Tier 2 stage of the textile supply chain, including pretreatment, dyeing and finishing, alone creates over 50% of fashion’s greenhouse gas emissions - more than shipping and raw materials combined.

 5. The Limits of Current Regulations

Certifications like Bluesign and OEKO-TEX restrict some harmful chemicals, but they don’t eliminate pollution entirely. Many dyes and finishes still slip through legal loopholes, and enforcement in major textile-producing countries remains weak. Also, many synthetic dyes are labelled as “organic” which they technically are but so is plastic.

Is There a Way Forward?

At newera.bio , we are creating an end-to-end solution to transform the dye industry into a bio-based future. We strive to not only provide high-performance, low-carbon microbial-based dyes, but our bio-based auxiliaries can also enable fast, clean, safe, and non-toxic dyeing with bright, and longer lasting colour fixation. They are biodegradable, non-toxic and water-saving, significantly improving the dyeing process’s pain points.

The dyeing process is fashion’s dirtiest hidden secret - but it doesn’t have to stay that way. Brands, governments, and consumers must push for:

• Stricter regulations on chemical discharges

• Investment in sustainable dyeing solutions

• Subsidies to textile manufacturers that ease their ability to adopt cleaner solutions

• Transparency in supply chains

Until the dyeing process is reformed, we will continue to buy clothes that may be cheap but have an unacceptable and unaccounted for environmental cost.