Bioplastics are on the rise: they also offer the textile market ever-more alternatives to man-made fibers produced from fossil raw materials – with forecasts predicting double-digit growth. However, there are also sobering headwinds: their ecological qualities are currently not sufficient to get a handle on the global problem of rising plastic waste both on land and at sea. Here, a differentiated look at the science is well worthwhile.
Even the name of the family of bioplastics requires some explaining. Here, bio is not necessarily bio. On one hand, there are bio-based plastics; these are partially, or completely, manufactured from plant biomass such as maize, sugarcane or cellulose. On the other hand, biodegradable polymers are produced. These, for example, break down into various metabolic products using micro-organisms. Bio-based plastics can be, but are not necessarily, biodegradable. Conversely, there are also polymers made from fossil raw materials that are biodegradable. Therefore, bioplastics are a veritable patchwork family.
A family with very good future prospects, if a current market survey conducted by the European Bioplastics Association, Berlin/ Germany, is to be believed. The researchers predict a global rise in the production capacity of bioplastics from 2.4 to 7.6 million tons between 2021 and 2026 – an average annual increase of more than 10 %. This sounds like very little in view of the 367 million tons of the overall plastics market (source: Statista). To date, the low oil prices, reluctant political support, limited market access and expensive manufacturing processes have hampered the success of bioplastics. According to the study, the market is expected to develop and rising environmental awareness among consumers and brands is anticipated to increase demand. This trend is also supported by innovative materials for bioplastics with improved properties and new functionalities and by the development of ever-new alternative plastic products and applications.
Furthermore, biopolymers are a future market for the textile industry as well. According to the Institute of Bioplastics and Biocomposites (IfBB), Hanover/Germany, 261,000 tons were used in textile applications in 2020, ranking second behind the dominant packaging applications (together making up just under 1.14 million tons). In turn, this figure seems tiny compared to the 68.2 million tons of synthetic fibers produced in the same year. However, the following applies both to the textile market and all other areas of use: bio-based biopolymers do not require fossil resources such as crude oil, whose processing causes environmental disadvantages, and which is becoming ever-scarcer and will therefore become progressively more expensive in the future. For this reason, the textile industry is also increasingly looking at using such alternatives.
The biopolymer polylactide acid (PLA), for instance, has been manufactured on an industrial scale for quite some time now. PLA is manufactured by means of polycondensation of lactic acid, maize or tapioca starch and is therefore completely bio-based and simultaneously biodegradable. In addition to packaging, the material is also used as spunbonds rolled goods as well as in filling fibers or in apparel worn directly on the skin. PLA ensures superior moisture balance, as it is able to relinquish and release more water than PET. It is also attributed antimicrobial qualities. Leading PLA manufacturers produce in the USA (NatureWorks LLC, Minnetonka/MN), the Netherlands, Germany and China, for example. Experts predict that demand for biopolymers will increase, as they can also tap into areas of use beyond that of conventional plastics. It is anticipated that PLA production capacities will double by 2023, while the manufacture of bio-based, non-biodegradable polytrimethylene terephthalic (PTT) – used in the production of fibers for carpets and other textiles – is also expected to rise.
One successful PTT product is Sorona by DuPont, for example. This bio-based polymer fiber has a weight ratio of 37 % of annually renewable plant-based raw materials. It has the properties of polyester (PET) and polyamide (PA), is very soft and is extremely durable and stain resistant. Sorona is deployed e.g. in carpets, apparel and automotive textile. DuPont de Nemours, Inc., Wilmington, DE/USA, advertises performance first and foremost with the added benefit of enhanced sustainability: their manufacture requires 30 % less energy and emits 63 % fewer greenhouses gases than in the case of the production of PA 6. Compared to PA 66, the manufacture requires 40 % less energy and emits 56 % fewer greenhouse gases. According to DuPont, Sorona is increasingly being used as a stretch fiber replacement for Spandex (elastane) due to its inherent superior performance and sustainability benefits. Sorona polymer fabrics can be sorted into today’s 100 % polyester fabric recycling streams without compatibility issues.
PA 56 also seems to harbor lots of future potential. The bio-based PA material is generated from starch and does not need to shy away from comparison with PA 66 or PA 6. On the contrary: PA 56 fibers such as Terryl from Cathay Biotech, Shanghai/China, which can be used for sports apparel, underwear and carpets for example, are good for spinning, have good mechanical properties as well as a high degree of textile wear comfort, and even exceed the classics in terms of their heat resistance and moisture absorbency. Terryl has also established itself in the high-performance industrial yarn market, which requires high melting temperatures and high modulus. Cathay Biotech is collaborating intensively with Oerlikon Barmag in order to generate optimum system processes for manufacturing fibers using biopolymers. Biopolymers such as PA 56 and PLA are high on the agenda at Oerlikon Barmag, particularly in China and Asia, where global bioplastics production is concentrated. Here, the company is registering growing customer interest in such yarns. In other words: consumers are increasingly demanding sustainable clothing.
Incidentally, bio-based materials are – contrary to popular belief – not really manufactured at the expense of the food sector. According to figures provided by the European Bioplastics Association, just 0.017 % of all globally available arable land are currently used for growing biomass for producing bioplastics in 2020. However, there is a surprising downside to biodegradable polymers. The University of Plymouth in the UK discovered that these do not break down in the environment very much faster than conventional plastics. Its study compared shopping bags made from various plastic materials: conventional ones manufactured from polyethylene, biodegradable, compostable and so-called oxo-degradable ones, which (incompletely) degrade in the absence of UV light, heat or oxygen. After 3 years under stable laboratory conditions, in the open air, in the ground or in the sea, the results were very sobering: only the compostable bag had lost some firmness in the ground and had completely decomposed in the sea after 3 months. However, it remained unclear here whether microplastic residue was released into the water.
Another argument currently casts doubt on the ecological benefits of biodegradable plastics. These are very difficult, or even impossible, to recycle and – due to their low tear-resistance – are not suitable as packaging for very long. Also, as waste, they increase the time and effort required for sorting. Their disposal therefore still poses several questions regarding integration into a meaningful closed-loop recycling system. However, progress is ongoing and bioplastics – whether bio-based or biodegradable – offer sufficient potential to also be a successful alternative to conventional plastics in the future.
Sorona, TERRYL = registered trademarks
Oerlikon Textile GmbH & Co. KG