Wool Fibres Readily Biodegrade in Marine Environments, Study Confirms
What happens to textile fibres once they enter freshwater systems and the sea? It’s a question that received scant attention until the recent rise of concern over microfibres. A substantial body of research firmly establishes how wool biodegrades on land, but far less was understood of its behaviour in the aquatic environment – until now.
Findings released by New Zealand research institute AgResearch now reveal the biodegradation rates of various textile fibres in the marine environment. The research, led by Dr Stewart Collie, followed the path of the fibres released by domestic laundry processes, examining how the breakdown process occurs.
• Both untreated wool and machine-washable wool were found to biodegrade readily in the marine environment, as did the cellulose-based viscose rayon. Synthetic fibres showed little or no biodegradation.
• Machine-washable wool – wool with a thin film applied to the surface to prevent felting– biodegraded even more quickly than untreated wool. Researchers believe that this is due to the loss of some of the wool fibre’s cuticle layer during the treatment process, rendering it more susceptible to microbial degradation.
• There was no evidence to support the idea that the polyamide resin used as part of the machine-washable treatment caused microfibre pollution.
Initial research on how wool biodegrades in marine environments was released in 1994, providing evidence for the theory that natural fibres are not harmful to our marine life and that they will naturally biodegrade, becoming part of the aquatic surroundings without causing any harm.
However, the actual process of biodegradation and the fate of textile finishes on the wool fibre remained a mystery, leading to the present research.
To measure the biodegradation, residues were examined using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The samples were comparable lightweight base layer fabrics made from two types of Merino wool, viscose rayon, polyester, nylon (polyamide), and polypropylene which had been shredded to remove interference from fabric structure effects.
The fabrics were washed repeatedly before testing to simulate a partial garment lifetime. Researchers then measured the average biodegradation of three samples for each fibre type relative to a control, namely readily biodegradable paper pulp.