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Cotton vs Polyester: Which Has the Better Sustainable Profile?

Cotton and polyester–the fibers with the largest share of the apparel market–have been the subject of recent and ongoing questions regarding which holds the better environmental footprint.

Both fibers have come under scrutiny for their environmental downfalls over the years, from cotton’s water usage in farming and manufacturing to polyester’s chemical base and production pitfalls.

In recent years, cotton has made concerted efforts in water stewardship and recycled polyester has helped that fiber’s footprint. Now questions of fiber shedding have created new issues about the profile of each opposing input.

Fiber attributes  

From a broad perspective, Alice Hartley, senior manager for sustainable innovation at Gap Inc., speaking at the Cotton Incorporated Cotton Sustainability Summit in April, said, “In sustainability we spend a lot of time thinking about impact and footprint of materials, and that’s really important and we’re not going to stop doing that. But we do also have to get out of our comfort zone and challenge ourselves to look farther into the future.”

For example, Hartley cited “water stress” across the world, including “hot spots in northern Asia” that could impact the future of arable land.

“For instance, we should be thinking 20 years out about where cotton is going to come from,” Hartley said.

Gap has recently set new goals in the use of sustainable cotton usage across its brands.

Similarly, Ken Lanshe, vice president of general merchandise, technical and quality at Walmart, told Sourcing Journal at the Cotton Inc summit that, “Our vision for textiles is that we want them to be sustainably designed and produced. In cotton, this means working to continuously improve the environmental and social performance of the fields where cotton is grown, sustainable land use methods and soil management.”

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Lanshe also announced at the summit that Walmart will increase the use of recycled polyester fiber, setting a goal of using 50 percent recycled content by 2025. It also has plans to source 100 percent more sustainable cotton for its private brands.

While brands have clearly stepped up their sustainability efforts for both fibers, the answer to which is better isn’t clear cut.

Donna Worley, director of marketing communications and public relations for Textile Exchange, told Sourcing Journal, “Our very general response to the question on [cotton and polyester’s] sustainability profiles would be ‘it depends’” because there are a “portfolio of preferred options” and “context and diversity matter.”

“In each fiber category, there are different ‘preferred options,’ as we call them,” Worley said.

For example, in cotton, there is organic, Fair Trade cotton and Cotton made in Africa, while in polyester there is mechanically or chemically recycled polyester and pre- and post-consumer recycled fiber.

“We don’t believe there is one best fiber for the circular economy,” Worley said. “It depends on the context which fiber may be best.”

She noted that outdoor brands might have to use synthetic fibers for certain purposes but can choose different “preferred options,” while others might choose to optimize the natural cycle and use regenerative organic cotton.

“In general, environmental, social and economic factors are important to look at, as well as looking at it from a lifecycle perspective,” she said.

Dr. Justin Bours, senior technical manager for the Cradle to Cradle Products Innovation Institute, said, “Determining a fiber’s suitability for a circular supply chain and economy depends upon a variety of factors, including the sourcing, manufacturing and ‘cyclability’ of the fibers from one use cycle to the next.”

Bours said in practice, producing fiber suitable for the circular economy requires optimizing that fiber across critical performance categories, including material health–using safe chemicals and avoiding the use of substances that are potentially toxic to humans or the environment–and material reuse.

“Responsible manufacturing processes that include water stewardship and the use of renewable energy and carbon management practices are also key,” he said.

Fiber shedding

While microplastic pollution traced to synthetic fibers like polyester has received much publicity, the verdict may still be out on the impact of natural versus synthetic fibers.

Anna Posacka, research manager of the plastics lab at Ocean Wise, an ocean conservation organization, said at the Cotton Inc  summit that a recently completed study conducted with the cooperation of several apparel brands, including REI and Patagonia, found textiles shed in home laundering were among the largest contributors of microplastics pollution.

While 99 percent of microplastics materials are captured at wastewater treatment facilities, billions of plastic particles are reaching the aquatic environment, Posacka said. However, in analyzing 38 different types of fabrics, Ocean Wise found that “textile design plays a very important role in the process. In general, we found the trend that natural fibers tend to shed more than polyester and nylon.”

Anna Cummings, global strategy director at 5 Gyres, an organization devoted to reducing plastics pollution, noted that in a study in San Francisco Bay, cotton fibers were found in smaller amounts than synthetic fibers, but “at the end of the day, cotton is biodegradable…and won’t have the kind of long-lasting ecosystem harms that synthetic fibers will have.”

Richard Venditti, professor of forest biomaterials at North Carolina State University, said research he conducted in conjunction with Cotton Inc. looking at various fabrics in washing, showed that all shed microfibers.

“We also found that cellulosic-based fibers shed more microfibers that did polyester,” Venditti said.

On the other hand, cotton and rayon, both cellulosics, biodegraded in water at a rapid pace, whereas polyester showed virtually no degradation.

“The thing about polyester is that it is basically inert,” Venditti said. “We are counting on our wastewater treatment plants so heavily. The textile industry has a very important role to play in determining what will happen to these fibers.”

In the area of microfibers, Worley of Textile Exchange said there are two key concerns: that non-biodegradable microfibers are released into systems where they cause harm and that microfibers, whether biodegradable or non-biodegradable, carry chemicals of concerns.

“While the first concern is particularly true for most synthetic fibers, the second concern is relevant for all fibers types,” she added.

Recycle and reuse

From a circularity standpoint, Bours of Cradle to Cradle said the number of times a fiber can be recycled is another consideration.

“Polyester can theoretically be continually cycled via a technical (chemical) recycling process, while cotton cannot typically be recycled more than once or twice,” he said. “By comparison, however, cotton does not pose the same environmental risk in terms of microfibers because cotton fibers are biodegradable (and degrade in a much faster timeline) and because cotton fibers do not have the same ability to attract and transport other environmental pollutants.”

Annie Gullingsrud, founder and chief strategist at Design for All Kind, noted that while natural fiber is intrinsically biodegradable, if it’s put into an environment like a landfill, its ability to biodegrade it basically taken away due to lack of oxygen and other conditions.

“The other thing is that when you have a fiber that’s in a garment, it’s dyed and treated, and that also limits the capabilities to biodegrade,” Gullingsrud said. “The difference, however, is that I would add the term bio-cumulative to polyester because it’s not going away.”

She said the answer is to shift away from virgin resources and focus on the use of recycled materials and apparel–“whether that’s reuse or recycled content from post-consumer textile waste.” She noted one of the biggest shifts has come from companies deciding to use only recycled polyester in their production.

“The entire shift in fiber choice has to be focused on getting more recycled materials into the cycle,” Gullingsrud added. “Using recycled content is about recapturing assets back into the system.”