Neha Arora and Dr Seema Sekhri provide a comprehensive review of pollution caused during denim manufacturing process and how sustainable practices can be adopted to reduce the environmental pollution.
Amongst the top foreign exchange earning industries for India, the textile units are scattered all over India. The textile industry involves processing or converting raw material into finished cloth employing various operations. It consumes large quantities of water and produces polluted waste effluents. Water is used extensively throughout textile processing operations. Almost all dyes, specialty chemicals, and finishing chemicals are applied to textile substrates from water baths. In addition, most fabric preparation steps, including desizing, scouring, bleaching, and mercerising, use aqueous systems. The amount of water used varies widely in the industry, depending on the specific processes operated at the mill, the equipment used. Typically 0.2–0.5 m3 of water is needed to produce one kg of finished product.
Reducing water consumption in textile processing is important aspect of pollution prevention efforts. The excess water used dilutes pollutants and add to the effluent load. Interest in ecologically friendly, wet processing textile techniques has increased in recent years because of increased awareness of environmental issues throughout the world. Consumers in developed countries are demanding biodegradable and ecologically friendly textiles. The main challenge for the textile industry today is to modify production methods, so they are more ecologically friendly at a competitive price, by using safer dyes and chemicals and by reducing cost of effluent treatment/disposal. Recycling has become a necessary element, not because of the shortage of any item, but because of the need to control pollution.
Sustainability in denim industry
Sustain means to maintain or to uphold and with regard to industrial processes, sustainability means establishing those principles and practices, which can help to maintain the equilibrium of nature in other words to avoid causing irreversible damage to earth’s natural resources. Moving to a greater degree of sustainability in our industrial processes and system requires that we achieve a fine balance between the social, economic and environmental aspects of textile production (figure 1). But equally important, a sustainable product is one which can compete effectively in the global marketplace against less sustainable products, i.e., which offers value benefits to the consumer, and where the economic returns from its success are fairly distributed back along the supply chain. (Colourage, 2009) Sustainability in textiles refers to methods employed in the production of fabrics that are more environmentally friendly and are produced in such a way that reduces the effect on the environment including recycling of water and raw materials, heat recovery from waste water and steam generation and reduction of dye and chemical usage and chemical substitution. (www.epa.gov/sustainability/basicinfo.htm)
The issue of sustainability with regard to dyeing in denim (fabrics) has for many years been a matter of concern to environmentally-concerned garment consumers as well as leading jeans retailers. By demonstrating a commitment to reducing demands on resources like water and energy, pollution of water and air as well as wastefulness of dyes/chemicals for denim dyeing and waste and degradation of cotton yarns and fabrics, participating denim producers establish themselves as truly responsible providers of the world’s most popular fabric. In the area of denim dyeing, there is enormous potential for reducing demand on resources including unnecessary dye/chemical consumption, water treatment and energy.
Benefits of sustainable practices in denim industry
The benefits of employing sustainable practices in the denim industry include:
Life cycle assessment of denim: Definition of LCA from ISO 14040* Series: “the compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its lifecycle”. (http://lsco.s3 /A-Product- Lifecyle-Approach-to-Sustainability.pdf)
- Improved brand reputation to concerned garment producers, retailers and jeans consumers.
- Improved customer satisfaction by establishing your company as an environmentally-responsible fabric producer.
- Improved profitability by reducing waste, especially reducing excessive use of dyes and chemicals which occurs in most denim operations.
- Reduction of waste water treatment by identifying and correcting causes of unnecessary dye losses in washing.
A Lifecycle assessment (LCA) is a global analysis of the environmental impacts resulting from a product during its whole life cycle that is from the moment of the extraction of raw materials to manufacturing, transportation and use and finally to the disposal of waste.
The consumptions and emissions of materials and energy for each step of the life cycle are quantified. These data are then used to proceed to the assessment of a cluster of environmental impacts (energy consumption, greenhouse effect, exhaustion of natural resources, acidification, etc). (www.avnir.org/ademe/EPD_en_jeans_v2.pdf)
In the lifecycle assessment of denims (LCA), the lifecycle of jeans from cradle-to-grave it was reported as a collection of seven independent systems. These systems in their respective order are: a) cotton production; (b) fabric production; (c) garment manufacturing; (d) transportation and distribution; (e) consumer use; (f) recycling, which then goes back to step (b); or (g) waste stream in a landfill.
Cotton production: The cotton-growing component of jeans, necessary for the creation of the fabric, is perhaps one of the most resource intensive, politically heated, and socially unjust of all the individual systems involved in product’s lifecycle. Because cotton growing is an agriculture-based system, it has sustainability factors rooted directly to the environment with respect to the land use, as well socially sustainable factors with respect to livelihoods of the farmers who cultivate the crop. These environmental and social components are dependent on each other, with changes either one of these having a linked affect to the other.
Fabric production and garment manufacturing: These processes were grouped together because of the many similarities in their social and environmental impacts that are common between them. While these stages are explicit in the jean making process, they both typically take place in factories, they both need to be adjacent to water bodies for their effluent, chemicals are used heavily for both sectors, and they both employ low paid laborers. Denim production is largely concentrated in developing nations like India, Pakistan, Bangladesh, etc. the major reasons of these are cheaper raw material and lower wages.
To get that blue colour in your pair of jeans, indigo dye is applied to the cotton fabric during these stages of the product’s lifecycle. Although once a natural dye, the indigo color now mostly synthetically produced in the past century. Only a handful of countries, led by China and India, continue to produce natural indigo in notable quantities. Synthetic indigo was first produced for commercial use in 1897 by a German Company BASF (Badisch Anilin and Soda Fabrik) founded by Berlin chemist Adolf von Baeyer. This indigo was called - Indigo Pure and subsequently used very heavily for jean manufacturing. (www.uvm.edu/~shali/Levi.pdf)
Indigo, which is otherwise a low quality dye, is widely used in denim dyeing to give characteristic blue color to denim while the low fastness of the dye is a boon for achieving a distressed look, it leads to major effluent problems during the dyeing process and later in washing of denim garment. Natural indigo has been completely replaced with synthetic indigo which seems to be more sustainable but biosynthesis of indigo will be really sustainable. At present what raises concern is the reduction technique in indigo dyeing. The use of sodium hydrosulphite as a reducing agent is associated with several environmental issues. Commercially available pre reduced indigo shows better fixation requires fewer chemicals and results in low effluent load. Alternate reducing systems have been explored, such as organic reducing agent, biological reduction, electrochemical reduction and chemical hydrogenation of indigo.
Non indigo dyes such as sulfur based dyes are widely used in denim warp dyeing and offer vivid colors. Due to their better affinity for cotton, this dyeing is more efficient and modern techniques can further reduce water wastage considerably. Sulphur dye are used for bottoming and topping of indigo for overall cost reduction. Sodium hydroxide, hydrosulfate, and formaldehyde are chemicals typically used in the manufacturing processes. Even if the colour is removed from wastewater, this does not necessarily mean that the water is clean: sulphur dye residues tend to remain in wastewater even after treatment. Any dye is a fundamentally polluting process. Textile mills require a nearby water source for breaking down dyes, washing, and treating the fabric. Worldwide, the single biggest threat in textiles is the wastewater effluence. Water quality regulations are typically based on measurements such as salt load content, toxicity, and dissolved oxygen content, which are all affected negatively when wastewater improperly treated (sometimes not even treated) is discharged into water bodies adjacent to these factories.
In addition to harmful environmental effects of the effluent, serious human health effects are also significant and not surprisingly, the link between textile workers and certain cancers, particularly bladder or nasal cancer, have long been known. Benzidine, a chemical component of synthetic dyes, as well as many others in the industry have been listed by the EPA as being of - concern and put textile workers at a much higher risk of cancer.
Stonewashing is a finishing process towards the end of the manufacturing in which the jeans are chemically treated to get the -faded look. In stone-washing the worn-out look is given purposely. The fabric is washed along with pumice stones. The stones and denim are spun together in large industrial washing machines. The longer they are spun together lighter the colour of the fabric with better contrasts would result. The time duration of this procedure is set beforehand so as to avoid the tear and wear of the fabric. Thereafter, the fabric undergoes various other processes of rinsing, softening and finally tumble-drying. These stone-washed fabrics are used for different purposes garment making as well as for upholstery purpose. Such chemicals in these finishing processes, like potassium permanganate and sodium hydroxide, tend to appear in high concentrations in the wastewater effluent as well as high basic pH levels.
Transportation: As with any globally marketed product, there are inherent environmental impacts as a direct result of transportation. The transportation of any consumer good has its relative carbon impacts on the environment and so it was necessary to at least have it be addressed briefly as worldwide, the GHG emissions from the transportation sector are substantial. Environmental and social impacts from the other steps involved in the lifecycle of a pair of jeans were more apparent; however the impact from this part of the jeans lifecycle cannot not be overlooked when addressing their overall sustainability.
Consumer use: LCA report by the research showed that the largest energy use and largest affect on global climate change occurred during the consumer phase of their jeans. While the overall water consumption in a jeans lifecycle is largely accounted for in the cotton growing stage at around 49 per cent, the consumer phase comes in a close second at 43 per cent (percentages based on the cumulative water usage for each stage in the jeans lifecycle. It would seem that most of the consumer use impact as reported in their assessment came from the energy and water consumption based on an average lifespan of two years with one washing per week totaling 104 washings. By decreasing the number of times jeans is washed on a monthly basis, significant amount of consumer impact can be reduced.
Recycling and landfill waste: Not surprisingly, there exists great potential for recycling in the jean industry. In a study done by Dennis Wambuguh in 2008, it was found that their existed a simple method of recycling indigo dye waste from effluent though absorption with palygorskite clay and subsequent conversion into - maya blue, an inorganic-organic hybrid pigment used in the paint and coating industry . It was determined that roughly one-fifth of indigo dye does not fix on the fabric and is sent into the effluent stream.
The denim scraps from factories in developing worlds end up going to nearby municipal landfills. Many times these landfills present serious environmental hazards, with respect to the chemicals that end up getting dumped in landfills, like sodium hydroxide, or the carcinogens released from incinerating the waste. However there are also significant social impacts from the typically unregulated disposal of textile scraps. It was common practice for the workers dumping the garbage to set fire to it, plaguing the lungs of the locals with many cases of respiratory and eye problems. The chemicals they were dumping their included sodium hydroxide, which can cause serious chemical burns and rashes.
Lifecycle assessment benefits
LCA of jeans by Levi Strauss in 2007
- It helps to focus on the most significant environmental impacts as we develop and evaluate sustainability programs and policies
- Informs product decisions to reduce the environmental impact from design, materials, and manufacturing
- Supports engagement with external stakeholders to reduce the impact of materials and consumer care
In 2006, Levi’s 501® jeans conducted LCA of, medium stonewash Produced for the US market during 2006. The full lifecycle of jeans from cradle to grave was studied. ISO standard were followed14040 series standards for results intended for internal use only.
The LCA results of the studied Levi’s® 501® Jeans was divided into three categories: climate change, energy use and water consumption. Results were as following
Consumer care impact on denim lifecycle
- Climate change impact was highest at the consumer use phase (58 per cent)
- Energy use impact was also highest at consumer use phase (58 per cent)
- Water consumption was highest at the cotton production and consumer use phases (49 per cent and 45 per cent respectively)
Reducing water consumption: It was found that number of washes can effect climate change impact consumers can decrease the climate change impact by about 32 per cent by decreasing the number of times they wash their jeans to once every two weeks from once per week and about 48 per cent by decreasing the number of times they wash their jeans to once per month from once per week.
Energy use impact: Consumers can decrease the amount of energy used when caring for their jeans by about 20 per cent by decreasing the number of times they wash their jeans to once every two weeks from once per week and by about 40 per cent by decreasing the number of times they wash their jeans to once per month from once per week.
Water consumption: Consumers can decrease water consumption by about 23 per cent (799.2 litres) by decreasing the number of times they wash their jeans to once every two weeks from once per week and by about 35 per cent (1,223.3 litres) by decreasing the number of times they wash their jeans to once per month from once per week.
Findings of LCA done in 2007
The majority of environmental impacts occur in lifecycle phases outside of our direct control. In order to decrease our overall environmental impact, efforts have to be continued within their own sphere of influence in addition to focusing on:
LCA of jeans by Levi Strauss in 2013
- Cotton production: the cultivation of our most important raw material.
- Consumer engagement: consumers have to be engaged and educated about the environmental impact of their fashion choices and the responsible care of their washable garments.
In 2013, Levi Strauss released a new global LCA study, an update on the 2007 study that examined the environmental impact of their LS&Co. products. The new study, initiated in 2013, looked at three LS&Co. products: a pair of Levi’s® 501® jeans, a pair of Levi’s® Women’s jeans, and a pair of Dockers® Signature Khakis. This latest study benefited from the latest advancements in LCA scientific methods, tools and data collection processes and gives greater insight into the two biggest impact areas by expanding the scope of data collected. This presentation dives deeply into the findings related to a pair of Levi’s® 501® medium stone wash jeans. The goal is that these findings will help LS and others in the apparel sector take more effective and holistic approaches to our industry’s environmental impact.
The new study analysed the complete product lifecycle, probing deeper into the environmental impacts of cotton in key growing regions, apparel production and distribution in a range of locations, and consumer washing and drying habits in key markets.
The new LCA expands on previous research to better understand the impact of cotton cultivation and includes data from the world’s primary cotton producing countries, including the United States, China, Brazil, India, Pakistan and Australia. It also analyses consumer care data from new markets, including China, France and the United Kingdom, to understand the costs and benefits of differences in washing habits.
General findings of LCA done in 2013
Consumer use findings
- Water consumption: fibre production, predominantly cotton, contributes by a wide margin to water consumption.
- Climate change: Consumer care and fabric production are the most significant phases for climate change impact and energy.
- Expanded scope: By expanding scope of study to include leading cotton- producing countries; it was observed that the water consumption from cotton cultivation increase, since the amount of water used to grow cotton varies significantly across the world. Also, by including new consumer markets it was found that washing and drying habits vary by region.
Washing every 10 times a product is worn instead of every two times reduces energy use, climate change impact, and water intake by up to 80 per cent.
Significant differences between regions:
Consumers in China are leading the pack: when it comes to laundering their jeans, they mostly wash in cold water and air dry
Materials, production and other findings:
- American consumers had the highest water intake and use of non- renewable energy. The good news is that Americans more prevalently use cold water
- Consumers in the UK and France mostly air dry their jeans but they use more hot water than American or Chinese consumers
- Consumers in the USA, UK and France wash their jeans more frequently than in China
The key findings of both the LCA OF LEVI’S® 501® JEANS was as following:
- Life cycle stages that had minimal contribution to impact include: fabric transport, product transport, packaging, production wastes, distribution, retail, and end of life waste.
Water consumption: Nearly 3,800 litres of water are used to make a pair of jeans. Fibre production, predominantly cotton (68 per cent), consumes the most water, followed by consumer care (23 per cent).
Climate change: Of the 33.4 kg of carbon dioxide produced during the lifecycle of a pair of jeans, consumer care (37 per cent) and fabric production (27 per cent) generate the most significant climate change impact and energy use.
Impact: By wearing jeans 10 times before washing, American consumers can reduce their water and climate change impact by 77 per cent, U.K. and French consumers by 75 per cent and Chinese consumers by 61 per cent.
Pollution caused by denim: Globally the textile industry manufactures a staggering five billion pairs of denim jeans every year and the potential impact on natural resources is significant. In addition to using billions of gallons of water as a byproduct of manufacturing, non organic cotton agriculture (which accounts for 98.5 per cent of all cotton grown worldwide) involves pesticides that can impair drinking water quality.
Denim garment is one of the most important and highly used textile clothing because of its exclusive features including color, versatile appearance and high strength that are widely used by young people. Blue jeans are much dirtier than we can predict. That cool distressed denim wash is the result of a several chemical-intensive washes. Fabric printing and dyeing involves such heavy metals as cadmium, lead and mercury.
Denim is produced from cotton yarn and in the conventional process is dyed blue with indigo. In its natural agglomerated form, this dye isn’t soluble in water. The dye molecules first have to be separated before dyeing – this is done by reduction using the strong reducing agent sodium hydrosulfite. Because reduced indigo also adheres poorly to the cotton, dyeing has to be repeated six to fifteen times. In each of these steps, the cotton yarn is passed through a dyeing vat and then oxidised in the air to fix the dye. This process requires not only vast amounts of energy but also large quantities of water.
It is estimated that 11,000 litres of water are consumed between production of the raw material and the finished jeans – a rather negative water footprint for this popular garment. Indigo dyeing also produces large amounts of cotton waste in slasher ranges because the production lines through which the cotton threads pass can be more than half a mile long. Every time the color is changed, the fibres remaining in the machines have to be disposed of. Also not very climate-friendly are the chemicals like hypochlorite and permanganate used to achieve fashionable washed-out effects in the final finishing stage.
In a LCA done by Levi’s it was concluded that over the lifespan of just one pair of jeans, 3408.5 liters of water is used, which is equivalent of running a garden hose for 106 minutes. The energy consumed is equivalent to powering a computer for 556 hours and the CO2 emissions are equivalent to those produced by an average automobile driving 78 miles.
It requires a lot of energy for the production of yarn and fabric. Additionally dyeing and finishing requires a lot of energy as laundering. Hot water and steam are required throughout the production process. Further most denim is no longer produced in the region where the finished garments are consumed so transportation as well impacts denim supply chain sustainability.
The conventional washing process (used in manufacturing) with the standard steps and chemicals is harmful to the environment. More specifically the most harmful (processes) to the environments are stone washing and the use of potassium permanganate. It’s also important to mention processes that have a high potential risk to put workers’ health at risk such as sandblasting, manual scraping and exposure to potassium permanganate.
Alternative solutions for denim production
- Organic cotton farming can help reduce some of the water quality impact from jeans production by removing pesticides from the early agricultural stages of the process but there are obstacles to organic cotton capturing more than a small slice of global cotton market share.
- Many of denim manufacturing’s harmful chemicals can be replaced by alternate garment finishing processes using new technology such as lasers or ozone.
- Another approach that can help reduce the environmental impact tied to jeans manufacturing is blending cotton with other fibres that have less environmental impact. Cotton is generally blended with polyester yarn. Polyester used in warp is kept low about 20-25 per cent, because the blend is harder to dye than cotton. It is used in higher amount in filling yarn since it has the advantage of being strong, durable and even in appearance. Another example is flax, which needs less water to absorb dye and can be grown with fewer pesticides than cotton.
- By replacing many of the older chemistry intensive denim washing and finishing process with technologies such as laser, those have little impact on natural resources.
- In order to minimise chemical concentrations, neutralise, and remove the color of the wastewater, it must go through treatments before it can be discharged into rivers or lakes. Research into these technologies can provide sustainable solutions for reducing the environmental impacts of effluent on the aquatic ecosystems by textile mills and can increase the potential for recycling the wastewater to be reused in the mill itself.
- LCA of denim analysed that half the impacts is generated during the jeans manufacturing stages and other half on the use of jeans (cleaning, ironing) and their end of life. Hence the consumer can have an influence on this stage by his purchasing behaviour: they can choose to buy pants made of organic cotton, or pants made of unbleached fabric to avoid the use of chemicals for the washing up etc. As half the impacts is due to the utilisation and the end of life of jeans, which are under the full responsibility of consumers. They can minimise those impacts by adopting a sustainable user’s behaviour.
Initiatives taken: Denim producers are working hard to reduce their impact on the environment. With the issue of water scarcity ever more important, they are focusing on using suppliers who have dramatically reduced water consumption and who recycle a significant proportion of their water. Many producers are also realising that low consumption and more careful and efficient use of water, energy, raw materials and chemicals benefits their bottom line performance. With new monitoring technology, information and support now available, weavers can improve their processing in ways that benefit both themselves and the environment. There are many ways in which sustainability has been taken into consideration while producing denims.
A recent development in the making of denim fabrics, handloom denims are much softer than mill made denims in comparison. It’s an imitative by denim club to promote and popularise the concept of sustainable and eco-freindly clothing. Denim made on handlooms is softer than mill made denim, has a unique texture and breathes well and helps feel cool in summer and retain body warmth in winter.
Energy impacts of handloom denim are almost zero, no energy is consumed either in the weaving processes or in forms of transportation of weavers to their place of work, thus resulting in a fabric with very low carbon footprint. Handloom denim is a true eco- friendly fabric as it does not require any kind of chemical washing post the weaving stage. The inherent softness and wear ability of the fabric eliminates the need for any kind of distressing or softening of the fabric or garments and no use of harmful chemicals or acids is required at all. Garments and other items made out of handloom denim can be used by infants, kids and everyone with a soft and sensitive skin due to the fabric being chemical free and soft.
A real denim recycling starts from worn out Blue Jeans as raw material in the denim production chain. Pure cotton Blue Jeans could be liberated from all metal parts and labels and shredded. The shredded denim, mainly cellulosic material, could be similarly deinked as realised in the paper industry for another origin of cellulosic material. The so achieved recycling cotton could as is or as mix with fresh cotton used again as raw material in the denim production chain.“Recycled -Jeans” would generate an attractive marketing concept, especially for the growing conscious customers.
Advanced denim by Clariant
With the revolutionary Advanced Denim technology, Clariant has now developed a more ecologically positive dyeing method. Instead of indigo, the Pad/Sizing-Ox process uses a new eco-friendlier generation of concentrated sulfur dyes such as Diresul® RDT. In the first working step – as with indigo – the dye molecule is reduced using a sugar- based reducing agent. Since sulfur dyes have a different chemical structure than indigo, they bond much better with the cotton. In the Advanced Denim’s Pad/Sizing-Ox process, a single dyeing box is therefore sufficient to intensively and permanently dye the yarn. A second rinsing step is no longer necessary. The dye is then oxidised with efficient fixing agents to make it adhere. In the same immersion bath, using Arkofil® DEN-FIX the yarn is coated with layer of starch to protect it during the following stressful weaving operation.
The groundbreaking technology of Advanced Denim’s Pad/Sizing-Ox therefore greatly simplifies and shortens the production. Naturally, this considerably improves the eco- friendliness. Compared to indigo dyeing, Advanced Denim’s Pad/Sizing-Ox saves up to 92 percent water, 30 per cent energy and 87 percent cotton waste. Numerous practical trials have confirmed these figures. A further advantage is that there are no effluents. Advanced Denim is a multipurpose concept for denim warp dyeing and denim garment processing, allowing a significant reduction in resources, particularly water consumption. It offers clear answers to modern ecological and technical requirements in the denim market and also in the field of fabric and garment finishing, with the development of specific products. It offers advantages in the field of water use and treatment as well as in the fashion (such as a large variety of shades, special ring or solid dyeing effects and stay-colour shades) and technical aspects.
Compared to indigo dyeing corrections and changes of color are easier and quicker, which also makes smaller production runs for specific market niches more profitable. Moreover, the sulfur dye Diresul RDT has only low sulfide content, and no unpleasant odors develop during production. The concentrated, liquid dyes are also free of heavy metals and ensure easy and safe handling during manufacture.
There is clear evidence that opportunities exist for optimising and minimising the use of natural resources, while simultaneously creating opportunities for cost savings and increased competitiveness. Made possible by new technologies, but encouraged and stimulated by consumer demand and legislation, the area has developed considerably, demonstrating that where there’s a will, there’s a way to create better denim. The sustainable denim production in future will be always a process, involving all single steps of the entire denim production chain. Hereby, the optimum comes from harmonising the used products, machinery equipment and process parameters to an optimum. In this process of development it would be very helpful, if the retailers (global jeans brands) could not only implement a global jeans recycling concept but also orientate the future eco-labeling on Best Available Technology (BAT) parameters. Minimising environmental impact and cost in the denim production will mean the use of minimal resources, chemicals, energy and water as well as minimal CO2 emission.
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Neha Arora is Research Scholar with the Department of Fabric & Apparel Science, Lady Irwin College, University of Delhi, New Delhi. Dr Seema Sekhri, the corresponding author is Associate professor, with the Department of Fabric & Apparel Science, Lady Irwin College, University of Delhi, New Delhi. She can be contacted on: email@example.com