Fibers & Textiles
Fibers & Textiles Alternative materials for mussel socks By: Bas Krins Technical Manager Senbis Polymer Innovations Emmen, The Netherlands Mussel cultivation involves a number of different steps. In The Netherlands mussel seed is collected on ropes hanging in the Waddenzee. The seed is harvested from these ropes and collected. Subsequently this seed is used for the cultivation of mussels. This can be done on the bottom of the sea. But more than 95 % of all mussels produced worldwide are grown on ropes. In that case, mussel seed is attached to a rope hanging in the sea. While there are various ways to ensure the mussel seed becomes attached to the rope, a common one is by using a so-called mussel sock. This sock is placed around the rope and the space between the rope and the sock is filled with mussel seed. This allows the mussels to grow and adhere to the rope. After about one month, the mussel sock is no longer required to support the mussels and should then start degrading. If the sock does not degrade in time, it will hamper the further growth of the mussels. The mussel sock Usually the mussel sock is produced from cotton by a knitting technique. This material has several disadvantages. The multifilament yarn developed was successfully processed on existing knitting machines for mussel socks. These mussel socks are now being tested in live mussel cultivation conditions at Blackshell Farm in Westport, Ireland. The degradation time is about a month in sea water and can be tuned by the diameter of the filaments and the composition of the compound. In the next months Senbis will optimize the yarn and set-up the requirements for market entry. www.senbis.com The degradation time can be adjusted somewhat by varying the thickness of the yarn. This means that in areas where mussels grow slower because of the low temperature of the water, for example off the coast of Iceland, the sock will degrade too fast. As a consequence, the part of the mussel seed not attached to the rope when the net degrades will be lost. A second issue relates to the environmental consequences of the use of cotton. Cultivating cotton requires larger amounts of water. Pesticides are also used. Hence customers seeking to market mussels under a biologically farmed label will suppliers of mussels not to use cotton. The challenge Senbis (Emmen, The Netherlands) is cooperating with Machinefabriek W. Bakker (Yerseke, The Netherlands), a supplier of equipment for the mussel industry, in order to develop a yarn that can serve as an alternative for cotton in this application. The degradation time in sea water must be similar to that of cotton, i.e. about a month. Very few biopolymers can fulfil this requirement as most do not biodegrade sufficiently quickly in sea water. In addition, the mechanical properties have to be sufficient for this application. This combination, fast degradation and mechanical properties, could not be realized with existing polymers. But by making a compound based on thermoplastic starch and other polymers, Senbis has been able to develop a material that can be converted into a multifilament yarns with sufficient tenacity and elongation. 22 bioplastics MAGAZINE [05/19] Vol. 14
Fibers & Textiles Cellulose based fibers fully biodegradable in water, soil and compost The Lenzing Group (Lenzing, Austria) received confirmation of the full biodegradability of its fibers in fresh water by the independent research laboratory Organic Waste Systems (OWS) (Ghent, Belgium). The new and existing international certifications conducted by OWS and issued by TÜV Austria (Kraainem, Belgium) verify that LENZING Viscose fibers, LENZING Modal fibers and LENZING Lyocell fibers are biodegradable in all natural and industrial environments: in the soil, compost as well as in fresh and in marine water. The biodegradability of cellulosic products and the synthetic fiber polyester was tested in fresh water at OWS according to valid international standards, e.g. ISO 14851. At the end of the trial period, Lenzing wood-based cellulosic fibers, cotton and paper pulp were shown to be fully biodegradable in fresh water in contrast to synthetic polyester fibers. The fact that synthetic materials are not biodegradable leads to major problems in wastewater treatment plants and potentially marine litter. In turn, this not only harms fish and birds living in and close to the oceans but also all marine organisms and us humans. “The Lenzing Group operates a truly circular business model based on the renewable raw material wood to produce biodegradable fibers returning to nature after use. This complete cycle comprises the starting point of the core value of sustainability embedded in our company strategy sCore TEN and is the ‘raison d’etre’ of our company”, says Stefan Doboczky, Chief Executive Officer of the Lenzing Group. “In living up to this positioning, we not only enhance the business of our suppliers, customers and partners along the value chain but also improve the state of the entire textile and nonwovens industries.” Both the textile and nonwovens industries face huge challenges with respect to littering. Therefore, legislative bodies worldwide can no longer ignore the issue and have moved towards plastics legislation aimed at limiting the vast amount of waste. In response, European lawmakers issued the Single-Use Plastics Directive currently being transposed into national legislation in the EU member states. Conventional wet wipes and hygiene products mostly contain plastic and were thus identified as one of the product categories to be singled out. Less polluting alternatives are generally encouraged by NGOs and legislators, e.g. products made of biodegradable wood-based cellulosic fibers. Plastic waste including microplastic can persist in the environment for centuries. In contrast, biodegradable materials are the best alternative to single-use plastics because they fully convert back to nature by definition and thus do not require recycling. MT www.lenzing.com bioplastics MAGAZINE [05/19] Vol. 14 23
