Marine biodegradation behavior of wool and other textile fibers

Microplastic pollution is a growing concern for the earth’s terrestrial and marine environments. Synthetic fibers from textiles are one source of microplastic pollution as fibers may be released from garments during use and especially during laundering, whereby they may enter the aquatic environment via wastewater systems. Wool is a natural fiber, but it is often given treatments to enhance its performance, such as to make it resistant to shrinkage caused by machine washing. Treatments of this type might influence the fiber’s inherent biodegradability. We sought to understand the aquatic biodegradation behavior of wool (in its unmodified form, and chlorine-Hercosett shrink-resist treated) and a range of synthetic fibers that are used in similar clothing applications. The biodegradation test was carried out in a simulated marine environment using a natural seawater inoculant according to the ASTM D6691 method with some modifications. Biodegraded wool residues were characterized by Fourier transform infrared and energy dispersive X-ray spectroscopies. The extent of fiber damage was observed by scanning electron microscopy. Both types of wool biodegraded readily under these conditions and machine-washable wool biodegraded to a greater extent than untreated wool. Regenerated cellulosic fiber (viscose rayon) also degraded readily, but all three synthetic fibers (polyester, nylon and polypropylene) showed virtually no biodegradation. Analysis of solid and liquid residues generated by the biodegraded wool showed no evidence that the chlorine-Hercosett-treated wool generated any non-degraded residues. Based on these findings we believe that, unlike synthetics, wool fibers are very unlikely to lead to microplastic pollution in the aquatic environment.