A Safe Environment Costs More than a Fossil-Based Economy

Researchers at the University of Georgia (UGA) have developed a new indigo dyeing technology that, they say, is an eco-friendly alternative to current methods. Sergiy Minko, a professor of fibre and polymer science at UGA and a corresponding author of the study, shares some thoughts on denim dyeing.

Long Story, Cut Short
  • Indigo isn’t water-soluble and has to be reduced with toxic chemicals before it can be used to dye clothing.
  • The denim industry uses over 45,000 tons of synthetic indigo a year, along with over 84,000 tons of sodium hydrosulphite as a reducing agent and 53,000 tons of lye.
  • To give denim its blue hue, the researchers added indigo powder to a hydrogel containing a small amount of nanocellulose. Hydrogels are a type of polymer that absorb water.
Dyed fabrics of various shades.
Five Shades of Blue Dyed fabrics of various shades. S Minko / University of Georgia

Dyeing of one pair of blue denim jeans consumes about 50-100 litres of water loaded with toxic reducing agents and alkali that remain as effluents in wastewater. The UGA researchers have introduced an environmentally sound indigo-dyeing technology utilising a high surface-to-volume ratio of nanocellulosic materials, which reduces water consumption up to a factor of 25 and eliminates the use of any reducing agent or alkali. This technology secures over 90% dye fixation compared to the 70–80% of conventional dyeing. Lighter or darker shades are approached in a one-step process compared to traditional vat dyeing with multiple (up to 8) dips in a reducing vat followed by oxidation. The dyeing process is as simple as the deposition of a nanocellulose hydrogel loaded with fine natural indigo particles and chitosan over the cotton denim fabric or yarn. The generated nanofibrillated cellulose mesh-like conformal coating encloses indigo particles, whereas chitosan improves the fixation and adhesion of the coating to fabrics via physical cross-linking.

Research into various aspects of indigo dyeing have been going on for a long time... till your discovery came. What do you think has been wrong with things all this while? Were people looking for solutions in the wrong area?
The currently used technology has been polished and demonstrated success for commercial production. Environmental aspects have been less important for a long period of time until now.

The next question follows. How did you have your eureka moment? In the sense that you wanted to pursue this nanocellulose idea? Were you sure it would work, when the project started?
One of the nanocellulose fabrication methods was studied at the Textile Department at UGA. When I joined the Department in 2014, this material attracted my attention and interest. The Department faculty, students, and I began to explore the properties of nanocellulose for environment-friendly textile dyeing technologies.

How long did the project take? Tell us more about it, and also your team.
We began this research with my colleagues professors Suraj Sharma, Ian Hardin (both in UGA) and Igor Luzinov (Clemson University),  a post-doc Yunsang Kim and graduate students, Alex Zakharchenko, and Raha Saremi. At that time, we developed reactive dyeing of fabric using nanocellulose. This project was supported by Walmart Foundation. Yunsang presented the results at the Green Chemistry Conference in Spring 2016 in Berlin, Germany, and won the First Prize in the Elsevier contest to continue this research. After completing this project, Suraj Sharma and I decided to continue and apply nanocellulose for indigo dyeing technology. A graduate student Smriti Rai made an essential contribution to the developments at this stage.

For anything to have an impact on the world, what works in a lab needs to be scaleable, in this case mass production. Will we be seeing that any time soon?
The same arguments as for the developments of R&D interests. There is a competition between two paradigms: a safe environment for future generations and profit at any costs. A safe environment costs more than a fossil-based economy.  I hope that a reasonable solution will be found and the support of environmentally-sound technologies will receive broad support from society.

Tell us about your personal denim history. As a scientist, where do you think denim tech (including indigo dyeing) is headed in the near future?
Denim fabric has been a successful commercial project for decades. For many nations, the demi garments became a daily “must be”.  However, any forecast in clothes trends is not a productive use of time. We live in a very dynamic world also in terms of new technologies and in terms of consumer preferences as well.   We are never sure what is coming… But, I am sure we will continue to see denim products coloured with indigo in the near future.

Subir Ghosh

SUBIR GHOSH is a Kolkata-based independent journalist-writer-researcher who writes about environment, corruption, crony capitalism, conflict, wildlife, and cinema. He is the author of two books, and has co-authored two more with others. He writes, edits, reports and designs. He is also a professionally trained and qualified photographer.

 
 
 
  • Dated posted: 30 May 2022
  • Last modified: 30 May 2022