Are Biodegradable Textiles Really Just a Myth?
Recent research took a deep dive into claims about biodegradable textiles.
Fabric made from natural or wood-based cellulose fiber took four weeks to degrade completely in the ocean, according to a recent study from the USC San Diego Scripps Institution of Oceanography.
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The same study tested them against fabrics made with Polylactic Acid (PLA), considered a biodegradable plastic, and petroleum-based fibers. The result after the same four weeks? No degradation at all. Same after four months, six months and a year, according to the study published May 24 in the journal PLOS One.
The study reinforces the conclusion that petroleum-based textiles do not degrade and consumers should not believe companies that say they do.
“This study shows the need for standardizing tests to see if materials promoted as compostable or biodegradable actually do in a natural environment,” said Sarah-Jeanne Royer who conducted the study run by the Ellen Browning Scripps Institution of Oceanography. “What might biodegrade in an industrial setting does not necessarily biodegrade in the natural environment and can end up as marine and environmental pollutants.”
The study used 10 different types of wood-based cellulose fabrics, including lyocell, modal and viscose, natural cellulose fibers like organic as well as non-organic virgin cotton, plus PLA and petroleum-based plastics such as polyethelene terephthalate and polypropylene.
All are commonly used in textiles. Some, like polyethylene terephthalate, are marketed as recycled. Polypropylene is used in textiles, carpets, geotextiles, packaging materials, and PPE.
In the study, samples were placed in cage-like flow-through vessels at the sea surface and at the seafloor, about 32 feet deep. Samples were photographed and examined every seven days. Small samples were removed and brought to the lab for further examination at high resolution by electron microscope, and by Raman spectrometer to discover chemical composition and molecular structure of the fibers.
The samples were submerged again, at the sea surface for 231 days and at the seafloor for 196 days.
They were then moved to the Experimental Aquarium at Scripps Oceanography from the Scripps Pier, where they were exposed to controlled conditions of flowing seawater. The natural, cellulose-based textiles continued to disintegrate for 30-35 days; the petroleum-based textiles showed no sign of disintegration, even after a total of 428 days. The cellulose-based samples were replenished each time one disintegrated, Royer said.
The natural, cellulose-based samples were replicated five times,” she said. “The other materials remained the same for more than a year.” While they are often promoted as more sustainable, the study proved otherwise.
Further, the same types of fabrics were tested in a closed-system bioreactor by an independent company. The bioreactor, which replicates a marine environment in an enclosed indoor system, measured the percentage of carbon dioxide produced by microbial activity using the fabrics as nutrients. Then used as a proxy for measuring biodegradability, it revealed complete biodegradability of the cellulose products within 28 days, and no biodegradation of the oil-based or bio-based fibers.
“This comparative study highlights how crucial our language is around plastics,” said Scripps marine biologist Dimitri Deheyn, senior author of the study. “Indeed, a bioplastic like PLA, commonly assumed to be biodegradable in the environment because it contains the prefix ‘bio,’ is actually nothing like that.”
