Optimized dyeing and finishing

The dyeing and finishing processes involved in producing textile-related products require enormous amounts of water and energy and also emit a huge volume of carbon dioxide. The specific dye and auxiliary substances used in the finishing processes contain numerous hazardous elements affecting those who use them, the immediate vicinity of production and the environment.

The key issue with dyeing and finishing is the vast amount of water required and correspondingly high wastewater emissions. Reportedly, 20% of global industrial wastewater is emitted by the fashion industry.

When it comes to considering textile sustainability, <water>, namely <high water usage> and <wastewater emissions in bulk>, are highlighted as problems which should be scrutinized. Several approaches to improve the situation have already been taken.

● To reduce the vast amounts of wastewater used in refining and dyeing processes, advanced technology for water-free plain dyeing in a high-pressure kiln or replacing printing with an inkjet alternative to reduce waste stencil cleaning and colour paste, has been developed and applied.

● Other approaches to reduce water usage include a dyeing method using CO₂ as a fluid subject to a temperature and pressure exceeding the critical point at which liquid and gas can coexist and/or integral colouring using pigment during the spinning process.

Focusing on ancient and naturally coloured cotton, alongside coloured (brown or green) cotton organically cultivated, with the original natural cotton materials used for yarn-dyeing or knitting applications. The scope of wool also includes coloured wool, namely raw wool. In widespread use for industrial applications to date thanks to its texture, it has recently also become a popular option for clothing after several modifications.

Diverse attempts to regenerate yarns by garneting and separating by fabric type and colour have been observed, after collecting used clothes and reducing what was mainly wool and cotton waste.

Although this system using existing materials can reduce the environmental impact, many problems remain, including excessive cost and the need to build a collection system for recycling.

There are three main categories of natural dyes, namely those of animal, vegetable or mineral origin. Back in ancient Japan, vegetable dyes for shades like indigo or mud or dyes using safflower were widely used in daily life. Although natural dyes have a low environmental impact, issues have included the complexity of processes and uneven or fading colours. Amid recent efforts to improve processing and ultrasonic auxiliary agents, research into further stabilisation and development continues.