What do we know today about the extent of the environmental impact of microplastics? What kind of role do synthetic textiles play in this field? And how can the input of textile microplastics into the environment be sustainably reduced? These questions were in the focus of a conference on 17 May 2018 at the Hotel Dietrich Bonhoeffer Haus in Berlin, organised by the "TextileMission" partner organisations in Berlin.
The objective of the event was a presentation the project "TextileMission" funded by the Federal Ministry of Education and Research (BMBF) to a specialist audience, to discuss possible solutions and to offer an platform for exchange between representatives from industry, research, politics and environmental protection. Central topics:
- Microplastics in the environment - status quo of research
- Bio-based plastics and biodegradability of fibre materials
- Potentials of textile technology research
- Filtering of microplastics in sewage treatment plants
Establishing standard methods and concepts
Dr. Claus-Gerhard Bannick, head of wastewater technology research at the German Federal Environment Agency (UBA), presented current UBA activities on microplastic reduction and provided information on scientific and regulatory aspects. All in all, UBA's experts estimate the annual volume of textile related microplastic input into the environment in Germany at 80 to 400 tonnes. In comparison, the abrasion of car tires amounts to between 60,000 and 110,000 tons.
An exact number of the total amount of primary and secondary microplastics in the environment is currently not available for the national, European or international sector due to a lack of data for various reasons. As one of them, Bannick cited the lack of a uniform, internationally recognised definition for microplastics. Bannick further explained that the different methods of sampling and the different detection methods lead to the fact that many of the studies circulating so far on the subject of microplastics are difficult or even non-comparable. "However, hard facts are required for the creation of standards and the implementation of proposed measures. The prerequisite for this is a uniform database based on harmonized, better standardized examination procedures," continued Bannick.
The presentation of Dr. Claus Gerhard Bannick can be found here.
Microplastics in soil, air and water
Dr. Bernhard Bauske, Senior Advisor Marine Litter Reduction at WWF Germany, summarised in his lecture the state of play of the new research field "Microplastics in the environment". With regard to the origin of the particles, a distinction is made ranging from primary microplastics (deliberately produced plastic particles) to secondary microplastics (plastic particles resulting from abrasion or decomposition). "Sources of primary microplastics include cosmetics and industrial abrasives. Secondary microplastics originate primarily from the abrasion of car tyres, the decomposition of plastic waste such as plastic bottles and shopping bags, but also from the production, wearing and household washing of synthetic textiles," Mr. Bauske explained.
In the context of textile microplastics, Mr. Bauske argued that the misleading term "microfibre" should not be used when referring to "microplastics". As for the background: Within the field of textile research microfibres are very thin and long fibres of every kind of material with a weight of one gram or less having a running length of 9,000 metres and more. They are used for very fine and dense fabrics.
Apart from uncertain definitions and still uncertain data with regard to the most important sources of microplastics, the need for action was clear for Bernhard Bauske: "Microplastics have been found all over the world in nature - in the air, in the soil, in freshwaters, in oceans, in sediments, also in the ice of the Arctic". In addition, microplastics are stored in mussels and food fish, for example, and can thus return to humans. "It is not yet possible to make a clear statement about the effect of microplastics on organisms. Although negative effects on organisms have been proven in various laboratory experiments, but so far this has mostly been done with concentrations that do not occur at altitude in nature".
The presentation of Dr. Bernhard Bauske can be found here.
Biobased does not always mean biodegradable
One research focus of the TextileMission project is on the potentials of biodegradable fibre material for reducing the textile related microplastic input into the environment. Michael Carus, Managing Director of the nova-Institut GmbH, explained some misunderstandings that are circulating in connection with the biodegradability of plastics: "Biodegradable is not the same as bio-based. Most biodegradable plastic products, for example car tyres made of rubber, are not supposed to be biodegradable at all. On the other hand, plastics that are biodegradable can be obtained from petrochemical processes."
It should also be noted that plastics have to fulfill special requirements for biological degradation in the ocean (more on this topic below). The figures presented by Carus with reference to the study "The Fiber Year 2018", in which his institute participated, are also exciting. "We expect an additional global fiber demand of 200 million metric tons by 2050. If the current trend continues, non-degradable petrochemical fibers will have a share of 85 percent - this has to be reduced." Mr. Carus is pinning hopes on an increased use of cellulose fibers which are not only biodegradable, but also have a good CO2 footprint.
The presentation of Michael Carus can be found here.
Fleece materials in the focus of textile technology research
Stefan Brandt, scientist at the Research Institute for Textiles and Clothing at Hochschule Niederrhein - University of Applied Sciences, informed the audience on the most promising prevention strategies for microplastics of textile origin. "Textiles are an important source of microplastics," Mr. Brandt said. "No matter if staple fibre, filament or fleece - different textile constructions have an influence on the extent of microplastic loss. The researchers and thus the TextileMission project are focusing in particular on fleece materials. The reason can already be found in the way they are produced: in order to obtain the properties desired by consumers in terms of heat retention, volume, wearing comfort and appearance, the knitted fabrics are processed in the manufacturing process with special roughing rollers. "The roughening process mechanically destroys fibres, resulting in increased particle output both during the wearing and household laundering process," explained Stefan Brandt.
This is where textile researchers intent to start to produce textiles with low microparticle emission. For this purpose they first use washing tests to determine textiles release of plastic particles and its size distribution. From this, they can draw conclusions about effects on the chemical processing of the fabrics or on the emission behaviour of clothing. In addition to process optimisation, the Niederrhein University of Applied Sciences will experiment with biodegradable yarns. "Easy processability and suitability for mass production are important criteria for us," said Stefan Brandt describing the challenge.
You can find Stefan Brandt's presentation here.
Retention of microplastics in sewage treatment plants
Prof. Dr. Stefan Stolte, head of the Institute for Water Chemistry at TU Dresden, in his lecture dealt with material flows of microplastics and the question of the retention capacity. "Synthetic textiles lose up to 20 percent of their weight during their product life cycle when worn and washed - we expect up to 1900 particles per wash," said the researcher. According to studies, modern wastewater treatment plants retain over 95 percent of the microplastic in wastewater, but the retention of fibrous microparticles is less well investigated. "It also has to be clarified how many microparticles are brought to the fields with the sewage sludge, which is partly used as fertiliser in Germany," said Stolte.
Either way, the five percent that are not retained still represent too much for Stefan Stolte. Mr. Stolte and his colleagues hope that this could be remedied by a fourth purification stage in sewage treatment plants, which could not only remove harmful trace substances such as drug residues and hormones, but also microplastics. The researchers at the TU Dresden are now elaborating on the effectiveness of the fourth purification stage to retain microparticles. Before the end of the project, the researchers hope to transfer the findings to a municipal sewage treatment plant.
The presentation of Prof. Dr. Stefan Stolte can be found here.