Light-induced Strength Loss in Jute and Polypropylene Carpet Backing Fabrics

The closed-loop recycling of mechanically shredded post-consumer wool-pile carpets as fertiliser was demonstrated previously, where it increased the yield of grass by up to 82%. When cultivated into the soil, the shredded carpet inevitably left fragments on the surface, which included jute and polypropylene components of the carpet backing. To determine their likely persistence in the environment, jute and polypropylene carpet backing fabrics were subjected to intense light from a 500-Watt lamp, which provided a reasonable approximation to sunlight outdoors. The changes in mechanical properties and microscopic appearance of the fabrics were monitored. Over 500 hours of exposure to light (equivalent to 125 days of strong sunlight), the jute lost 60% of its strength. The polypropylene lost strength more rapidly than the jute, i.e. 88% loss over 250 hours. In an outdoor situation, the jute and polypropylene would be subject to rain and microbial action, as well as sunlight, so degradation will be faster than was measured under laboratory conditions. The results of this study suggest that fragments of jute and polypropylene carpet backing, on the surface of soil, may not constitute an environmental hazard, and that photodegradation of microplastic fibres on land (such as those in waste water sludge applied to land), reduces the risk they pose to aquatic environments.