For the textile industry, application of regenerative raw materials is a matter of daily routine. Plant fibres such as linen and cotton, as well as animal products such as wool, silk and leather – natural products are used in many textile areas. With regard to sustainability and resource efficiency, however, unconventional ideas are now being implemented. New high-tech fibres with previously unknown properties, for example, are now being produced from formerly discarded materials from the food and beverage industry.
FACTS & FIGURES
No. of companies:
€32 billion (2015)
(Source: Confederation of the German Textile and Fashion Industry)
Examples of bioeconomy:
High-tech fibres made from spider silk,
plant tanning agents
Natural products have been used for thousands of years to make clothing. The Egyptians and Romans of antiquity used flax fibres to make linen fabrics. Leather, which is tanned animal hide, was a favourite material even in the Stone Age, as a material for making shoes and belts. It has been only in recent decades that inexpensive petroleum-based synthetic fibres have predominated over leather. In the recent past, however, a return to traditional natural fibres has become particularly apparent.
Unlike cotton, the stems of other textile plants are further processed: for example, flax, hemp and jute. Global production of such bast fibres, however, is much less – around 2 million tons annually. After the bast fibres have been separated, their further processing is similar to that for cotton. Yarn is spun from the individual fibres, which is then processed to textiles. Their areas of use, however, are different: bast fibres are used primarily as so-called technical textiles for industrial applications, and not so often to manufacture clothing.
The capability for cotton to cover the enormous international demand for textiles continues to decline. In 1990, 19 million tons was internationally available, which amounted to a share of 49%. Although 20 million tons was available in 2000, this amounted to a share of only 40 %, since the international market for all fibres had grown. Currently, cotton has a share of 31%.
The majority of materials used by industry, however, consists of synthetic and chemical fibres made of synthetic polymers such as polyester, Teflon™, Lycra®, Trevira, nylon and others. Today there are also other examples of natural polymers that are used as raw materials for fibres, but that are produced by chemical processes. These include viscose, made of cellulose. Unlike cotton fibres, viscose fibres are characterized by greater variation in their fibre geometry: in length, crimp, fineness and cross-section form. As a result, they have more extensive application. Although energy and water consumption in production and processing of viscose is less than for cotton, its processing creates unhealthy and environmentally harmful toxins such as hydrogen sulphide (H2S) and carbon disulphide (CS2). Other chemical fibres made from cellulose do not present this problem. As a result, a direct-dissolving process was developed for the production of Tencel® and lyocell fibres, which features a non-toxic solvent and which functions in a closed materials cycle. In addition, the required cellulose is obtained from eucalyptus or beech wood. Since these trees grow rapidly and offer appreciable yield per land area, their environmental balance is better than for cotton. Recent research work has additionally revealed that flax, hemp, bamboo, banana plants and soya are suitable sources for the cellulose pulp.
Synthetic fibres dominate the market.
Breeding of new fibre plants
Recently, interest has again been focused on plants that had virtually lost public attention: for example, the stinging nettle. In addition to hemp and fibre flax, the stinging nettle was among the most important domestic fibre plants until the Second World War. Afterward, it was forgotten. Thanks to new processing methods, however, it is today possible to make textiles from the stinging nettle with the fineness of cotton and with excellent textile properties – and to make fleece for technical uses. The usual propagation by or from cuttings, however, is less suitable for large-scale cultivation, and with the fibre content of existing cultivated varieties, increases in yields are still possible. With funding from the BMEL, the Institut für Pflanzenkultur (IFP) in Wendland, Germany, and the Faserinstitut Bremen e. V. (FIBRE) have now developed new breeding lines of fibre nettle characterized by fine yet strong fibres and by large fibre content.
Spider silk is a true wonder of nature – one-tenth the diameter of human hair, yet twenty times stronger than steel and at the same time more elastic than rubber. This natural material would therefore be ideal for a whole range of applications: for example, for high-tech textiles. Until now, production of spider silk has been problematic, since these animals cannot be bred in large numbers or “milked”. The company AMSilk GmbH in Martinsried has taken a biological approach here. After many years of experimentation together with material researchers from Bayreuth, and with funding from the BMBF, AMSilk – a spin-off of Technische Universität München – has tailored bacteria such that they can produce spider silk proteins. In addition, a process has been developed to process these molecules to fibres. In March of 2013 the first biotech fibres were spun that are suitable for use in high-tech textiles and medicine. The next step is to move the technology from the lab to the pilot scale.
Spider silk – one-tenth of human hair bute twenty times stronger than steel.
The textile industry offers not only plant raw materials: wool, silk and leather and other animal products also play a major role in the current assortment of raw materials. Whereas wool and silk also represent fibres, leather production entails tanning the hides of animals to preserve them. Of all the hides processed in the world, over 95 % of them originate from cattle, calves, sheep, goats and hogs: by-products of the food industry. In earlier time, tanning agents from wood and bark were primarily used; in more recent years, tanning based on chrome salts and other minerals has come to be used. Although these methods are cheaper and less labour-intensive, they have earned criticism owing to their environmental impact.
For this reason, recent years have seen increasing development of plant-based tanning agents. The company Wet-Green GmbH, for example, has developed an extract of olive leaves as tanning agent – an active agent that intrinsically protects trees from herbivores. During olive harvest and pruning of the olive trees, around 10 % of the harvest by weight consists of leaves. Earlier, these leaves were frequently burned on site – but now they serve as raw material for production of plant tanning agents. As a result, they improve the environmental balance of a great variety of products such as cars, shoes, couches and watchbands. This economic potential of olive leaf waste is great: theoretically, up to 40 % of world leather production could be processed in this manner.
The sports article manufacturer Puma also emphasizes sustainability. The remake of its classic Suede models is now being marketed as a complete eco-shoe. The upper material of the shoes is synthetic suede developed by Toray, a Japanese company. It consists of 100 % recycled polyester fibres transformed from production waste into synthetic material by a chemical recycling process. The rubber part of the shoe soles consists partly of rice hulls obtained from food-production waste – which reduces the share of petroleum-based rubber. Production of this remake saves 80% of the CO2 emissions produced by conventional shoe manufacturing. Production and sales of the recycling shoe, 140 g lighter than its 1968 predecessor, protect the environment: according to Puma, savings of 15 tons of CO2 emissions result for every 10,000 Suede pairs that leave the factory.
The company Qmilk Deutschland GmbH in Hanover has specialized in the profitable use of waste from the food industry. Qmilk is developing a biopolymer consisting of the milk protein casein, which the company obtains from no longer marketable raw milk: of which 1.9 million tons is available annually. Already in the 1930s there were approaches to use this waste for textile manufacture – but excessive chemistry was required in those days. This is no longer the case. Currently, production of these biopolymer fibres takes place in collaboration with the Bremen Fibre Institute (FIBRE), without chemical additives. The product is used not only for clothing and home textiles but also as technical fibres: for example, for use in medical technology and in automobile construction.
For the textile industry, however, importance is being placed not only on regenerative raw materials. In order to improve the environmental balance of industrial production and processes heavily based on chemistry, biotechnological approaches are also currently receiving greater emphasis. One example is the bleaching of textiles, for which hydrogen peroxide (H2O2) is still widely used. This oxidant, however, must be completely removed from the textile material after each bleaching process. In the conventional method, this takes place by rinsing the textile material at least twice with water at 80 to 95 °C. This procedure lasts about two hours and consumes large quantities of water and energy, but since it does not completely remove the bleach, various other chemicals are necessary for post-treatment. The biotechnological variant exploits the natural power of biocatalysts, for example, of the enzyme catalase. This enzyme allows removal of the hydrogen peroxide with warm water (30 to 40 °C) within a few minutes, in only one rinse step. This reduces costs for cooling water, process water and steam – and protects the environment by use of less energy.
Biotechnological processes on the basis of enzymes are also used in production of jeans. Traditionally, pumice is used to achieve the so-called stonewashed effect: an uneven colour structure. This costs water, energy and product quality, since the pumice treatment is harsh on textiles. For each pair of jeans, this also produces 600 g of stone abrasion, which damages the machines and must also be disposed of. But there is an alternative – without pumice but with special enzymes. The stone-washed effect achieved with cellulase is the same, but this alternative reduces environment-related costs by 54 %, and there are virtually no pollutants released into effluent water (-97 %) and into the air (-86 %). Another example shows the environmental relief and the cost-reduction potentials in textile dying. By use of the enzyme catalase in dying pre-treatment of cotton, it was possible for each ton of treated textile to reduce climate-adverse carbon dioxide emission by up to 120 kg, water by up to 19,000 l and power by up to 500 kWh. Enzymes also play an important role in the cleaning of textiles. Even with old household agents such as bile soaps, enzymes already showed their cleansing effects.
The enzyme cocktails used today for washing agents are usually produced by microbes (see section “”). They serve not only to remove soiling from textiles, but also perform many and various other tasks: for example, cellulase removes small protruding individual fibres and thereby assures that no lint forms on the textiles.
In Mediaeval times, clothing was dyed red with dyer’s madder (Rubia tinctorum) – and today natural dying processes are experiencing a renaissance.
Natural dyes for exclusive textiles
To enhance the sustainability of textile dying, producers now resort to an old tradition in the textile trade. As early as 4,000 years ago, Europeans dyed natural fibres with plant dyes. Since Mediaeval times dye plants have been cultivated: for example, dyer’s woad for blue, dyer’s madder for red and reseda for yellow. With the development in the nineteenth century of synthetic dyes based on coal and petroleum, these substance lost significance: until their renaissance in the 1990s. Upon the initiative of the state of Brandenburg, the domestic plants madder and reseda began to be cultivated again: to be sure, only on small, job-order scale. The greatest challenge was to obtain standardized extracts. The company Spremberger Tuche GmbH, in a project funded by the BMEL, has now developed a functioning process. The extracts can now be processed in advanced dying machines and dosing systems. A total of 120 colour shades can be produced from two extracts. Owing to the high price, these producers cannot serve a mass market; their customers come primarily from the area of exclusive textiles.