A new, eco-friendly cotton bleaching technique
The EU textile industry is worth over EUR 119 billion and is predominantly small- and medium-enterprise (SME)-based. In fact, about 70% of the total textile labour force is employed in these SMEs. However, the industry is suffering under the global economic crisis and is facing strong competition from regions such as the Far East. Moreover, current bleaching methods cause fabric damage and the formation of toxic by-products, and require large amounts of water and energy to remove chemicals. The project 'Improved novel eco-friendly bleaching system for cotton using enzyme and ultrasound processes' (COTTONBLEACH) investigated a new technology for bleaching without such negative effects. In addition, the technology complies with current EU environmental legislation. The consortium comprised research and technological development (RTD) performers and various SMEs with expertise in enzyme production, ultrasound technology and textile machinery manufacture. Laccase, an enzyme from the Myceliophthorathermophile fungus, is very effective when used in an enzymatic pre treatment step. The step accelerates the bleaching speed, achieves greater whiteness than conventional bleaching methods and reduces the amount of hydrogen peroxide (H2O2) needed. Researchers investigated various factors, such as laccase dosage and incubation temperature and time, to optimise the step. Ultrasound applied during the pre treatment step and the actual bleaching step proved to be very effective in enhancing the whiteness. Piezoelectric devices constitute the best ultrasound technique due to their cost effectiveness. H2O2 is a promising bleaching agent: it is non-yellowing, non-toxic and odourless. However, it requires very high temperatures and stabilising additives to work. A main aim of the project was therefore to achieve high in-situ H2O2 production. This was done using a newly developed enzyme called oxyMt-cellobiose dehydrogenase (CDH). COTTONBLEACH constructed a prototype containing preparation tanks, ultrasonic devices, side equipment and control software. Their new technique will lead to savings of up to EUR 140 000 per year for production of 1 500 tonnes of fabric, improve textile quality and significantly reduce energy and water consumption.