TRENDBOOK Technical Textiles 2018/2019
The importance of recycling for the areas of application of technical textiles (TU Wien)
Andreas Bartl, TU Vienna at the Institute of Chemical,
Environmental and Bioscience Engineering, Vienna/Austria
Legal conditionsIn the European Union, the waste framework directive 2008/98/EU (WFD) stipulates a so-called waste hierarchy . According to the WFD the following priority order in waste prevention and management legislation and policy shall be applied:
2. preparing for re-use,
4. other recovery, e.g. energy recovery,
On December 2, 2015 the European Commission launched a circular economy package (CEP). By the end of 2017 the European Council of Ministers, member of the European Parliament and representatives of the EU Commission had agreed on the key points of the circular economy package. It is expected that the respective directives concerning the CEP will be released in 2018. The intention of the CEP includes, on the one hand, improvements of environmental protection and, on the other hand, a strengthening of the economy as well as the creation of new jobs. Its main elements include new, binding targets for the recycling of municipal solid waste (MSW) and packaging waste. At the same time the fraction of MSW to be landfilled is limited to a maximum of 10 %. The textile industry is only partially affected but has to face the circular economy. The CEP exceeds simple quotas for reuse and recycling and covers the complete cycle from raw materials, use phase, waste management and secondary raw materials. Among other things, the CEP demands additional actions to promote features such as durability or reparability of products. These measures might directly affect the complete textile processing chain.
Production and waste volumesAnnual fiber production is currently approaching a volume of 100 million tons , while in the next years a further growth is expected to take place. Although in the last years cotton has stagnated at around 20-25 million tons, growth was mainly driven by man-made fibers, in particular polyester. A large share of fibers is used for apparel and home textiles. However, experts forecast an increase particularly in the area of technical textiles. By 2014, a total of 26.6 million tons (out of 93.2 million tons, i.e. 29 %) were used for technical textiles only. The volume of this market segment is expected to grow to 35.5 million tons by 2020, which corresponds to an increase of 33 % . The areas of application for technical textiles are heavily fragmented and include end markets such as agriculture, building and construction, geotextiles and civil engineering, industrial textiles, hygiene and medical, transportation packaging, personal and property protection, and sports. By 2010, out of a total volume of 24.2 million tons of technical textiles  the largest sector was packaging with a volume of 3.6 million tons (i.e. 15 %), including products such as tea bags, desiccant bags, mobile containers or protective covers. Due to the broad areas of application, there is a requirement to adapt existing schemes for reuse and recycling. Systems which function in the area of apparel and home textiles cannot be directly transferred to technical textiles.
Detailed data on the quantities of end-of-life technical textiles are not available. It is reported that by 2007 in Germany about 400,000 tons of technical textiles had been put on the market. In the period from 2007 to 2013 the volume of apparel and home textiles had grown from 1.126 million to 1.347 million tons which represents an increase of 10 %. It can be assumed that the growth rate in the area of technical textiles was even higher.
Waste preventionWaste prevention means measures taken before a (textile) product has become waste. A distinction has to be made between quantitative and qualitative prevention . Quantitative prevention comprises in particular the extension of the lifespan of textile products. However, in the field of apparel and home textiles this measure is only a pious wish. On the one hand, these products are subject to quickly changing fashion trends. On the other hand, more and more cheap and low quality textiles, in particular from Asia, are dominating the market. Both trends have caused a tremendous decrease in the useful life of apparel . The lifespan of apparel can also be prolonged by re-use. According to the WFD, re-use means any operation by which products or components that are not waste are used again for the same purpose for which they were conceived . Typically second hand clothing belongs to this category.
The same considerations apply to technical textiles. Due to the strong fragmentation of the market, it is difficult to make general statements about waste prevention. As for apparel, the avoidance of toxic additives is an issue for technical textiles. As mentioned above, in the coming years the volume of technical textiles is expected to grow at a significant pace. Thus, an increase of waste in this segment is likely to be forthcoming in the foreseeable future.
© Foto: Sashkin – Adobe Stock
CollectionA separate collection of end-of-life textiles is a prerequisite for any recovery operation. Any commingling of textiles with municipal solid waste will cause contaminations hindering any further re-use or recycling. A separate collection system for apparel and home textiles is established in several European countries. As an example, in Germany 75 % of the available volume of apparel and home textiles are covered by a separate collection . Data from different countries are difficult to compare as frequently also carpets and shoes are include. In most cases technical textiles are not collected together with established systems for apparel.
Statistics and data on the volumes of technical textiles that are covered by a separate collection are hardly available. This is aggravated by the fact that the area of application for technical textiles is extremely broad which demands totally different collection systems and, later, distinct recycling schemes. In contrast to apparel, technical textiles (e.g. geotextiles) are in use for a quite long time period and are not instantly available for recycling.
Preparing for re-usePreparing for re-use means checking, cleaning or repairing recovery operations, by which products or components of products that have become waste are prepared so that they can be re-used without any other pre-processing . In the area of apparel, second-hand clothing is understood as re-use. In this sense preparing comprises a sorting procedure which separates re-wearables from worn or soiled items on the one hand, and waste on the other. Sorting facilities, which are mainly based on manual labor, split the collected textiles into 150-350 fractions of re-wearable items . Most second-hand clothes are sold, in particular, to developing countries.
Even if re-use has a high priority according to the waste hierarchy, the advantageousness of the systems must be questioned. Even if the requirements for fashion and condition are much lower in developing countries, any piece of apparel will at some point be damaged and not be feasible for any further use. Usually waste management does not function in the receiving countries and end-of-life textiles will end up on open dumps or in rivers, and, later, in the ocean. This procedure does not correspond to the idea of the circular economy. This also raises the question of whether the export of (cheap) second-hand clothing could negatively affect the local textile industry. Even if data on preparation for re-use of technical textiles are hardly available, it can be assumed that it does not represent common practice. Among other things, this is due to the following reasons:
- Technical textiles usually reach their end-of-life status on the basis of damage rather than on the basis of fashion. Thus, they are commonly not feasible for re-use.
- Protective clothing such as uniforms are inadequate for re-use as they serve as distinguishing feature (e.g. military) and have to be destroyed. EU-wide, annually 80,000 tons of uniforms arise of which about 70,000 (i.e. 88 %) are landfilled or incinerated .
- Technical nonwovens and textiles are frequently integrated into complex products such as automobiles. A disassembly from the end-of-life products is usually not justifiable for financial reasons. Frequently, vehicles, washing machines, etc. end up in a shredder, after which any recycling of the fibrous components is impossible.
- Technical textiles in the field of medical textiles are often contaminated and for legal reasons have to undergo a special incineration process.
- Technical textiles used in composite material are usually not recoverable. Due to a good adhesion between fiber and matrix a separation is difficult and usually only economically viable for expensive fiber materials such as carbon fibers.
RecyclingAccording to the WFD, recycling means any recovery operation by which waste materials are reprocessed into products, materials or substances whether for the original or other purposes. It does not include energy recovery or backfilling operations . For textiles, it is possible to distinguish between the following processes:
- Cleaning and wiping rags
According to the standard DIN 61650 for cleaning and wiping rags (C&WR) a minimum size of about 20-30 cm is required. Knitted or woven fabrics composed of cotton, half-linen or viscose are feasible materials and have to be free of ticks, eyelets, buttons, tapes and zippers. Usually clothing which is not suitable for re-use is sorted out for production of C&WR. The use of technical textiles as a source for C&WR is only possible to a limited extent.
- Reclaimed fibers
The process of reclaiming fibers comprises a mechanical breaking down of knitted or woven fabrics by a Garnett machine. The obtained reclaimed fibers exhibit a significantly reduced fiber length but can also contain unopened fabrics. Depending on the pre-treatment, reclaimed fibers are composed of various polymers and colors. In principle, it is feasible for reclaimed fibers to undergo a yarn formation process. In practice, in Germany 95 % are processed into nonwovens used as technical textiles, e.g. in the automotive industry . The European patent EP3260595 describes a possibility to recycle flame-retardant protective clothes . Technical textiles go through an enzymatic hydrolysis process and the remaining fibers, commonly aromatic polyamides (aramids) or polyimides, undergo a fiber tearing process to obtain individual fibers ready for another yarn formation.
The scheme of re-spinning comprises the melting of the polymer and its use for another fiber forming process. In practice, fibers are produced from recycling-polyester, whereby the polymer predominantly originates from beverage bottles. By 2012, worldwide 8.2 million tons of end-of-life polyester has been collected. After preparation, 6.4 million tons of polyester could be supplied for recycling, with the fibers industry being the major consumer with 4.6 million tons corresponding to 72 % . By 2012 this amount corresponded to 15 % of total polyester fiber production of 29.1 million tons.
In view of the circular economy it would be desirable for textiles containing polyester to be used for a de novo fiber spinning. This scheme is significantly more challenging than using polyester from bottles and is in practice rarely carried out. Mostly textiles contain several finishing agents and are composed of different fiber types. Recently, a research project was launched which treats blended fabric by an enzymatic hydrolysis. Thereby it is possible to obtain a pure polyester fraction feasible for re-granulation and re-spinning . The scheme is suitable for apparel, home textiles and certain technical textiles.
- Feedstock recycling
Feedstock recycling comprises procedures which break down the polymers of end-of-life textiles into smaller molecules. On the one hand, rather unspecific processes such as pyrolysis, hydrocracking or gasification can be applied. Thereby more or less all kinds of textile waste can be utilized.
However, a broad spectrum of gaseous, liquid and solid products is obtained which requires a rather expensive further processing into products such as fuels .
Alternatively, a selective de-polymerization of certain polymers is an option. For instance, polyester can be broken down into oligomers or monomers by means of ionic liquids, enzymes, alcoholysis, hydrolysis, glycolysis or aminolysis .
A subsequent de novo polymerization generates polyester which is equal to polyester from virgin raw materials. Possible input materials are all materials containing polyester, including apparel and technical textiles.
Technical textiles represent an increasingly substantial market segment in the area of textiles. Not least because of changing framework conditions such as the circular economy package, appropriate concepts for waste prevention and recycling have to be implemented. Processes which are viable for apparel are only partially transferable to technical textiles. Only recently, new concepts such as the use of highly specific enzymes to break down polymers have been available on a large scale and are currently being checked for possible industrial application. Finally, based on the circular economy package, the European Commission demands intensive exchanges between all stakeholders of the textile value chain. Therefore, it will already be necessary in the near future to keep the recyclability of textile products in mind during the design phase.
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The article has been published in our TRENDBOOK Technical Textiles 2018/19 of our magazine TECHNISCHE TEXTILIEN/TECHNICAL TEXTILES.