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| Issue date:14/10/2009 |
| ATA Journal for Asia on Textile & Apparel - Oct 2009 Issue |
| Source:Journal for Asia on Textile & Apparel |
| by Sanjay Gupta |
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| Expectations from textile products in terms of functionality and variety have been on the rise in recent times. With a growing world population and the spread of the fashion industry, textile and apparel consumption has escalated. However, an increasing public attention on global warming and environmental protection has brought into sharp focus the ecologically damaging footprint of this industry. The primary concerns are related to the use of water and energy. |
The supply of water is finite and demand for water has outgrown the world’s population in these decades. Livelihood of more people around the world is affected by water shortages and wastewater problems.
According to the recent “Water in a Changing World” report on world water development published by the United Nations in March 2009, the world’s population is growing by about 80 million people a year, implying increased freshwater demand of about 64 billion cubic metres a year. Population growth and rapid economic development have led to accelerated freshwater withdrawals, and the report explained the need to intensify water investment on infrastructure and various aspects to resolve the water issue.
In the business world, new companies in urban areas of China and India have to meet the environmental standards before they can operate in order to reduce costs of treating water. Enterprises in Europe faced closure for the same reason years ago as the governments, like their peoples, became more conscious with environmental protection. Regulatory standards are getting stricter and fabric manufacturers are looking to new ways for times ahead.
Increasing water scarcity was observed by the UN |
Almost half of the world’s demand for textile fibers is fulfilled by cotton, which is preferred for its comfort and for being natural. It is also thought to be better for the environment.
A number of studies, however, reveal that cotton does bring pollution: pesticides used during cultivation and a large consumption of water during cultivation and later during wet processing of fabrics, i.e. washing, de-sizing, bleaching, rinsing, dyeing, printing, coating and finishing.
Groundwater use has grown rapidly in some countries
Note: Countries with multiple lines have different datasets that do not reconcile |
It takes an estimated 20,000 litres of water to produce one kilo of cotton, apart from chemicals and energy. The entire wet process on cotton (from pre-treatment to finishing) can consume up to 700 liters of fresh water/kg of fabric. About 600 liters of it becomes wastewater after the process. On polyester, the figure does not exceed 100 liters.
In terms of energy, approximately 25% of energy in the total textile chain, i.e. fibre production to spinning, twisting, weaving, knitting, clothing manufacturing etc, is used in dyeing.
About 34% of energy is consumed in spinning, 23% in weaving, 38% in chemical wet processing and rest in miscellaneous processes. Power dominates consumption pattern in spinning and weaving, while thermal energy is an area of concerns for chemical wet processing.
It is clear that the option of switching from cotton to man-made fibers would be difficult in the short-term, and more attention has been put on improving wet processing, which might call for a drastic change in approach.
Eco-efficiency pursued by Asian textile players
Concerns over the Earth are likely to drive all machinery development in the next decade. There is a need to not only modify technology, machines, chemicals and dyestuffs to save water and energy; but to change the processes completely so that water and energy usage is minimized and wastewater discharge reduced to zero.
The trend is visible in the choice of processing machinery from Asia. Shipping data of the 2007 international textile finishing machinery market showed an increase in global deliveries of mercerizing equipment, a process which increases a fabric’s affinity for dye and thereby reduce percentage of colour in effluent, as well as the re-emergence of cold pad-batch dyeing ranges known to be more environmentally friendly than conventional dyeing methods. This underlying trend is likely to continue in years to come.
Textile machine builders have been working on other improvements for preparation and pre-treatment processes like the separation of streams for the disposal of industrial effluents, which facilitates recycling of less polluted water. Producers of dyeing machines continue to come up with better machines consuming reduced energy and water, chemicals and dyestuffs consumption. Fong’s ECO-6 high temperature dyeing machine, for example, has a reduced dyeing cycle of only 291 minutes, and the total water consumption is as little as 38 l/kg. Automation and process control is the focus, such as programmable process control of the machinery, automated dye weighing, dissolution and dispensing interfaced with computerized colour measurement and recipe formulation. Most solutions being offered can lead to 10-30% saving in water and energy consumption, in addition to improvements on quality, delivery times and pollution prevention.
Another focus area is reusing and recycling of water.
A good example is Benninger’s diaphragm filtration system that allows water, chemicals and waste thermal energy to be recovered and recycled. The multi-stage diaphragm system comprises of an ultrafiltration stage and downstream reverse osmosis stage. The ultrafiltration stage has a ceramic diaphragm that separates particulates and long-chain organic wastewater components at temperatures of up to 95°C. The reverse osmosis diaphragm almost completely separates water from dissolved dyestuffs and salts. The separated process water can be reused directly in all areas of the textile finishing plant without adversely affecting the quality of the end product. A recovery rate in excess of 80% for wastewater and 70% for thermal energy is achievable in desizing, bleaching, mercerizing, dyeing and finishing. In addition, 80% of water-soluble size and caustic soda can be recovered as concentrate.
These innovations or added value in terms of functionality are not likely to make a drastic reduction in the consumption of energy and/or water.
Radical change is under research
In the traditional processes, waiting times and distances between the processes are too long. They cost much money and energy (due to transport). We have to look for solutions that eliminate the use of water, not just minimize it. The three emerging technologies,
i.e. information technology (IT), biotechnology and nanotechnology, are expected to bring new interventions on the front of textile systems and processing.
IT-based process control systems for wet processing are well known for ensuring overall efficiency and quality along with savings in time, energy, water and other utilities.
However, newer and more innovative applications of information technology are being developed. A Dutch scientist Jan A. Craamer has proposed an innovation wherein dyeing has been carried out using the ink-jet printing technique. The process uses only about 2.4 liters of water per kilogram of fabric, only a tiny fraction of energy and reduces processing time by one tenth. Dyeing can be combined with printing and finishing as well. Lot size is inconsequential and there are no wastages or pollution.
The use of biotechnology, meanwhile, involves the integration of natural and engineering sciences that offers the potential for new industrial processes requiring less energy, and renewable raw materials. It can replace harsh and energy demanding chemicals by enzymes in textile processing; provide environmentally friendly routes to manufacture of textile auxiliaries and dyestuffs; and help manage waste more effectively.
By using enzymes in the bleaching process, for example, 6,300 to 19,000 liters of water per tonne of textiles can be saved. Moreover, by substituting the enzyme for a reducing agent in a hot rinse, additional 1.6 to 1.8 GJ/tonne of energy can be saved. Furthermore, owing to the reduced energy consumption, release of CO2 will be lowered by 100-120 kg/tonne of textiles produced.
The third new technology, nanotechnology is often quoted as having the potential to revolutionize traditional production methods. Teijin Fibers has developed luminescent polyester where the fiber core is covered with about 60 layers of nylon and polyester with different refractive indices for light. Such fibers may lead to elimination of dyeing process altogether.
Research institutes and enterprises involved in textiles are increasingly utilizing technological advancements in diverse fields of information technology, automation and robotics, biotechnology, nanotechnology and etc, in quest for more efficient and eco-efficent ways of manufacturing and processing textiles.
Dr Sanjay Gupta is Professor of Textile Design and Development at the National Institute of Fashion Technology, New Delhi, India
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| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
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| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
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