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Research and Innovation

NC State Textile Waste Research Paves Way for Greener Textile Future

Sonja Salmon (left) and Siyan Wang (right) stand in the lab with lab coats and protective glasses. Salmon holds fabric samples and Wang holds two bottles of solution with some fabric fragments visible.
Associate Professor Sonja Salmon (left) and Ph.D. student Siyan Wang (right).

“Thinking about our planet and the future, we want to learn and teach more about materials that are already on the planet and how they can be used to help us overcome issues like greenhouse gas emissions and waste accumulation.”

This is how Associate Professor Sonja Salmon describes the mission of her Textile Biocatalysis Research Group at the Wilson College of Textiles. The group explores the interactions of enzymes and microorganisms with polymers, fibers and textile materials. Fiber and Polymer Science Ph.D. student Siyan Wang, a member of the group, recently earned a spot on the front cover of Cellulose journal for her research on cotton fiber fragments.

Characterizing cotton

Wang’s article, titled “Preparation and characterization of cotton fiber fragments from model textile waste via mechanical milling and enzyme degradation,” provides crucial information for researchers working to decrease the 11 million metric tons of textiles waste that go into U.S. landfills every year.

The idea is that clothing and other textiles can be sent into bins or recycling centers to be reused. Some textiles are high enough quality to be repurposed in their current state. However, cotton textile waste that is not high quality enough to be reused can be broken down into small fragments and reused in different ways. Traditionally, this can be done through physical milling or chemical treatment. Physically milled cotton textiles are shredded, then sorted to remove fibers long enough to be respun. Textile waste that is chemically treated is dissolved in various chemicals in order to separate the cellulose that can be spun into yarn. 

Wang’s research moves towards a greener alternative.

“In my previous research, I found that you can use enzymes rather than physical milling or chemical treatments to degrade cotton. Because enzymes are a biomaterial, enzymes are a much more environmentally friendly way to break down cotton,” Wang says.

“Enzymes are natural catalysts; they help facilitate all the chemical reactions that happen in life,” Salmon explains.

Wang’s research aimed to break down cotton samples using these enzymes and characterize the resulting fragments in ways that had never been done before.

Cotton samples that have been degraded with enzymes.

“It’s one thing to make these fragments, but to characterize them and describe how big they are and what their properties are, that’s really important to teach the world what they could be used for,” Salmon says.

Wang was not only able to describe the characteristics of the enzyme-degraded cotton, she was also able to identify potential uses for them such as papermaking, composites and insulation.

“People are now looking at products that were made from plastics for decades to see how they can be made in a different way with wood pulp, cotton or textile waste,” Salmon says. “The very important thing about this publication is that we characterized detailed properties of cotton fragments so that additional researchers can see that and be inspired to use them to make products.” 

Digging into dyes

Another important factor in Wang’s research is the effect dyes have on the properties of the cotton fragments. 

“Sometimes the presence of dyes can limit the applications of the final products,” Wang says. “If we want to overcome that, we need to find how we can decrease the effect of the dyes on the final product or find a way to apply the dyed products to another application such as pigments or printing materials.”

Wang with the cotton sample (right) that she then treats with enzymes to create fragments (left).

By identifying how dyes affect the final cotton fragments, Wang opens the door for textile designers to avoid dyes that hinder recycling, and for dye companies to design new dyes that are more compatible with recycling strategies. This is just one of the ways the Textile Biocatalysis Research Group will continue moving forward with Wang’s research. 

“We’re trying to reteach people about this cellulose polymer, which is the number one polymer on earth,” Salmon says. “There is more cellulose on earth than any other organic polymer. Nature decided this was a really great material to make things from, so we should learn from that and realize that there are a lot of things we can make from it.”

Mentorship in the lab

Wang credits a big part of her research’s success to the community and mentorship she found with Salmon and her lab.

“As a student in a research lab you need to make big and small decisions all the time,” Wang says. “Often I will ask Dr. Salmon what would work better for me, but she won’t direct you to the answer. She makes you think yourself and gives you tips on how you can make your decisions. This way of learning made me grow a lot.”

It was Salmon who encouraged Wang to submit her research to Cellulose journal. Together they found that the results they were observing were underreported. Salmon guided Wang through the writing and submission process, offering constructive suggestions and edits to the manuscript before submission and again after receiving peer review feedback. It is a long and detailed process to get research published in a scientific journal, much less to be chosen for the cover as Wang was. 

“I’m very grateful to Dr. Salmon for her guidance,” Wang says. “We both felt greatly honored that our article was chosen for the cover.”

Wang is carrying the skills and knowledge she has learned in Salmon’s lab with her as she conducts new research within Wilson College studying hemp fiber for textiles.