Beyond the dye bath: how textiles could be coloured with far less water

A new BioSusTex-supported review explores how water-saving and waterless dyeing technologies could reduce pollution, conserve freshwater and help make textile production more circular.

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Colour is one of the first things we notice about clothing. Yet behind a brightly coloured shirt, pair of trousers or household textile is an industrial process that can consume large volumes of water, energy and chemicals. A new open-access review, “Non-aqueous textile dyeing,” examines how textiles could instead be coloured using processes that replace some or all of the water with alternative media. The article was written by researchers from VTT Technical Research Centre of Finland and Aalto University and published in Current Opinion in Colloid & Interface Science. Supported by the BioSusTex project, the review brings together established and emerging approaches and explains what must happen before they can be adopted more widely by industry.

Why does textile dyeing use so much water?

Conventional dyeing generally uses water to dissolve or disperse dyes, transport them into fibres and control heat and chemical reactions. This approach is well established and compatible with existing factories, but it comes with a substantial environmental cost. The review reports that conventional aqueous dyeing typically consumes around 50–100 cubic metres of water for every tonne of fabric. The resulting wastewater may contain dyes, salts, surfactants and other chemicals. High salinity and persistent organic compounds can make this wastewater particularly difficult and expensive to treat. These pressures are becoming harder to ignore as freshwater scarcity increases and the textile sector faces stricter environmental requirements.

What does “non-aqueous dyeing” mean?

Non-aqueous dyeing does not refer to one single technology. It covers a family of approaches that partly or completely replace the traditional water bath. Changing the dyeing medium can affect how a dye dissolves, how it reaches the fibre and how securely it becomes fixed. Some systems can also reduce the use of salts, alkalis and repeated washing steps. Many are designed to recover and reuse the processing medium in a closed loop, reducing both freshwater demand and liquid waste. The review assesses several routes, each with different advantages, limitations and suitable textile applications.

Adding colour before the fibre is made

One of the most mature options is dope dyeing, also called spin dyeing. Instead of colouring a finished fibre or fabric, pigments are mixed directly into the polymer before the fibre is produced. Because the colour becomes embedded within the fibre, this approach can provide excellent durability and eliminate the need for a separate wet-dyeing stage. It is already used commercially for several synthetic and regenerated fibres. The trade-off is flexibility. The colour must be selected during fibre production and cannot easily be changed afterwards. This makes dope dyeing highly efficient for large, predictable production runs, but less suitable for rapidly changing colour collections or small customised batches.

Dyeing with carbon dioxide

Another approach uses supercritical carbon dioxide, a form of CO₂ created under controlled temperature and pressure. In this state, CO₂ can move through materials like a gas while carrying dyes more like a liquid. It can penetrate synthetic fibres such as polyester and transport suitable dyes without a conventional water bath. At the end of the process, reducing the pressure allows the CO₂ and unused dye to be recovered, while eliminating wastewater and much of the energy normally needed to dry the textile. However, the equipment must operate at high pressure. This raises investment, engineering and safety requirements, and the method is currently much better suited to some synthetic fibres and dyes than to cotton and other natural materials.

Alternative liquids designed for circular use

The review also examines several types of alternative solvents. Ionic liquids and deep eutectic solvents can be tailored to interact with dyes and fibres. They may improve dye penetration, reduce unwanted dye reactions and support closed-loop recovery. Deep eutectic solvents can also help swell cotton fibres, making it easier for colour to enter and bind while reducing water, salt and auxiliary-chemical use. Other approaches use alcohols, silicone oils, liquid paraffin, polymeric solvents or tiny water-containing droplets dispersed within an organic medium. These systems aim to deliver the dye efficiently without filling an entire machine with water. For example, the review discusses alcohol-assisted cotton dyeing in which certain reactive dyes achieved substantially higher colour strength than in water-based processing. It also stresses that this performance depends strongly on the dye and solvent: an approach that works well for one colour may perform poorly for another. Reverse-micellar systems go a step further by packaging dye and small quantities of water inside microscopic droplets suspended in another liquid. These droplets act as carriers, bringing the dye to the fibre while avoiding a large aqueous bath. Some reported systems recover more than 95% of the solvent, although scale-up, solvent safety and integration into existing factories remain important challenges.

Could these processes really be better for the environment?

Using less water does not automatically make a process sustainable. If an alternative solvent is energy-intensive to manufacture, hazardous to handle or lost after one cycle, its wider environmental footprint may outweigh the water savings. This is why solvent recovery is central to the review’s conclusions. Studies assessed in the paper indicate that some silicone-based non-aqueous systems could reduce freshwater use by 61–80% and greenhouse-gas emissions by around 40–45% compared with conventional dyeing. However, these benefits depend on recovering more than approximately 98% of the solvent. The same principle applies to ionic liquids, deep eutectic solvents and supercritical CO₂. Closed-loop recovery, energy-efficient operation and careful assessment of solvent production are essential. The environmental impact must therefore be evaluated across the whole life cycle, rather than only by measuring water use inside the dyeing machine.

What could this mean for consumers?

For the person buying a shirt or pair of jeans, the dyeing technology is largely invisible. But wider adoption of these processes could eventually mean:

• clothing produced with substantially less freshwater;

• less polluted wastewater released from textile manufacturing;

• lower use of salts and other auxiliary chemicals;

• colours that remain durable over repeated washing and use; and

• manufacturing systems better suited to recovering and reusing resources.

There will not be one universal waterless process for every garment. Polyester, cotton, wool and regenerated cellulose behave differently, and dyes developed for use in water do not always work in alternative solvents. Future solutions will therefore need to match the right dye, fibre and processing medium.

Safety must be designed in from the beginning

Alternative solvents also bring their own safety considerations. Alcohols are flammable. Some ionic liquids may persist in the environment or present toxicity concerns. Supercritical CO₂ requires high-pressure equipment, while other solvents may require protective clothing, ventilation or strict exposure controls. The review therefore emphasises Safe and Sustainable by Design. This means considering worker safety, toxicity, biodegradability, recyclability, energy demand and regulatory compliance while the process is still being developed, not after it has reached the factory. Bio-based solvents made from substances such as glycerol, lactic acid or sugars could offer promising options when combined with efficient recovery systems.

A roadmap towards cleaner textile colouration

The new publication does not present non-aqueous dyeing as a simple replacement for water-based processing. Instead, it provides a roadmap for deciding where each technology can deliver genuine benefits. Some approaches, particularly dope dyeing, are already commercially established. Others still need improvements in dye compatibility, solvent cost, recovery efficiency, process safety and industrial scalability. The review concludes that wider adoption will require the combined development of new solvents, suitable dyes, process engineering, life-cycle assessment and closed-loop manufacturing systems. By bringing this knowledge together, the work supports BioSusTex’s wider goal of enabling safer, more sustainable and increasingly circular ways to produce and colour textiles.

Read the open-access review:

Non-aqueous textile dyeing, Current Opinion in Colloid & Interface Science, 2026, 85:102045.

DOI: 10.1016/j.cocis.2026.102045