Mapping Environmental Sustainability in Denim Processing

Md Shadman Shakil

With a long history, denim has seen several changes to fit different fashions. Investigating sustainability, including products and industrial processes, is crucial to achieving Sustainable Development Goal (SDG) 12 and identifying areas for improvement. Cotton fiber obtained from fields is spun into skeins, stained with indigo, and then woven to create denim. Jeans, the most significant item manufactured from denim, can be further colored, digitally printed, or washed using various methods. Sustainability difficulties emerge with cotton production and processing because it takes 1500 gallons of water to cultivate the 1.5 pounds of cotton needed to make one pair of jeans. Weft yarn that is undyed and indigo-dyed warp yarn are typically used to make denim. The traditional indigo dye was natural and generated from plant sources, but synthetic indigo dye became more popular with time. Sustainability became a problem once more. Recycling jeans is challenging due to using metal fasteners like rivets, zippers, and leather-look labels in addition to composition and care labels. This chapter discusses the global denim industry, the effects of processing denim on the environment, and the critical sustainability challenges related to the denim sector.

Denim Weaving: The final step in making denim is weaving, which significantly impacts the final product’s quality. The yarn counts affect the fabric’s weight, stiffness, cover, drape, tensile strength, and other characteristics. Denim fabric is woven as a 3/1 twill using an interlaced warp and grey weft. Projectile, rapier, and air jet looms are frequently used weaving machines in denim manufacturing. The denim industry is notoriously cutthroat, with volume often overriding specific niches. Therefore, factors like optimization and marketing profile influence the performance of denim weaving businesses. The utilization of designed yarns, intelligent machines that weave denim efficiently, and online quality monitoring systems are some of the possibilities. These could lessen the energy needed for weaving while improving resource and material efficiency. The commercialization of these technologies indicates the direction of denim weaving and should produce high-quality, economically feasible denim.

Recovery of cotton solid waste from denim weaving: Waste jeans are one of the most considerable portions of the millions of tons of textile trash produced each year. Waste jeans are seen as a cotton-rich substance which has the essential to develop into a renewable source of unprocessed cotton for the manufacture of new products to address the shortage of cotton grown on farms. Under this context, the current research aims to create a green, sustainable system for recovering polyester and cotton fibers from textile waste. The first phase of the process involved leaching nitric acid (concentrated. 60%) to remove textile colors from used jeans, followed by activated carbon to regenerate the used acid. Then, cotton and polyester were broken down and separated using a green reconfigurable hydrophilicity solvent.

After mixing distilled water and the solution for one hour at 0 °C, CO2 was added to renew the solvent and extract the polyester. The precipitated polyester was then recovered by filtration, and the solvent was changed back to hydrophobic via steaming and matching CO2 removal. The content and morphology of the freed fibers and recovered polyester were studied using electron microscopy, SEM, and FITR. FTIR and titration-based analyses were used to investigate the regenerated solvent and acid. Following the circular economy concepts, the suggested technology’s performance was examined and included calculating recycling rates, assessing the economics, estimating greenhouse gas emissions, and exploring the sustainability of the materials that were used and recovered. The findings indicated the potential for economic rewards of up to $1,629 per ton of waste and a decrease in the carbon footprint of about 1,440 kg of CO2 equivalent per ton of garbage. Investigations were conducted on the chemical composition, thermal behavior, and morphology of recovered cotton, solvent, acid, and polyester. The suggested technique can be viewed as a high-potential method for recovering cotton depending on the ecological footprint (93%), profitability (1466 dollars per ton), emissions of greenhouse gases (-1,534 CO2-eq/ ton), and sustainability assessment.

The Woes of Denim: Due to fashion, cotton was substituted for wool, initially used to make denim. There are 2 billion pairs of jeans made each year worldwide, so any significant change will require a considerable persistent effort. Yet, cotton production and processing have sustainability challenges. Only one pair of jeans may be made from 1.5 pounds of cotton that needs more than 1450 gallons of water to grow. As previously noted, denim jeans produce a significant amount of water. According to Tatiana Schlossberg, a prominent ecological correspondent for the New York Times, “Cotton, in general, is an extremely thirsty crop.” Based on where it is cultivated, producing 1 kilogram (2 lb) of cotton could commence the test to 7,560 gallons of water. Using 16 percent of all pesticides on cotton plants exposes farm workers and others in the area to serious health hazards. Cotton crops also absorb a lot of chemicals. Weft yarn that is undyed and indigo-dyed warp yarn are typically used to make denim. Before the move to synthetic indigo dye, indigo dye was natural and obtained from a plant source. Yet, as seen from the material below, these dyes also present a unique threat to environmental degradation. The tint of denim blue found in trendy jeans is created with the defining blue dye, Indigofera tinctoria. A typical pair of jeans requires half an ounce of dye, according to Vice (2011).

The issue, though, is with its manufacture. This polluting process is highly noticeable in the waterways and how the manufacturing impacts the workers and residents near Xintang, China, the denim world’s fashion capital. One of every three jeans pairs sold worldwide is made of denim in Xintang, China. By 2013, Xintang’s rivers ran a shade of blue and odor poorly due to manufacturers discharging chemical-filled wastewater into nearby waterways without regulatory oversight. The river in the image above has a blue tint due to chemicals released by factories that make jeans. Residents rely on this water for drinking and bathing, but hazardous elements like lead, mercury, and copper have been discovered in unsafe concentrations. According to some locals, workers and residents have reported rashes, lesions, and infertility (Guang et al., 2020). An enormous quantity of water, energy, and pollutants are used to produce just one pair of jeans. Concerns about the water supply for residents downriver exist in addition to the workers’ health. Millions of Guangzhou residents receive their drinking water from the East River. The safety of the water supply in Dongguan and Shenzhen is at risk as a result.

Microfibers the actual offender: The phase of denim life cycle during which they are constantly used and cleansed by their end user is the most harmful. Microfibers most frequently wind up in our rivers, lakes, and oceans when they don’t release them into the air and contaminate our airways.

Those were the exact conclusions of the Canadian study, which found residues of denim microfibers in the Great Lakes of the United States and Canada, the suburban lakes of Ontario, and even in the Canadian-owned Arctic Archipelago. Furthermore, they weren’t detected in insignificant quantities. 23% of the microfibers discovered in sediments from the Great Lakes, 12% from Ontario lakes, and 20% from the Arctic were denim microfibers. Although the researchers did find a single microfiber in the abdomen of a rainbow-smelt fish inside the Great Lakes, it is still unclear exactly what type of effects this pollution is predicted to have on the local flora and fauna. Even though you might never travel to the North in your lifetime, your jeans can do so.

Pollution and Remedies in the Dyeing Process: Due to the extensive use of chemicals and dyes during production, the denim processing sector is known to produce substantial amounts of pollution. These are a few of the contaminants produced during the production of denim:

• Chemicals used in dyeing: Formaldehyde, benzidine, including heavy metals, including chromium and cadmium, can be found in many synthetic dyes used in the processing of denim. These pollutants may harm both individuals and the environment.
• Water pollution: The production of denim uses a lot of water, and the wastewater produced might have significant amounts of chemicals and colors. This effluent can harm aquatic life and pollute surrounding waterways if it is not adequately treated.
• Air pollution: The manufacturing of denim can release volatile organic compounds (VOCs) into the atmosphere due to the usage of specific chemicals and dyes.
• Pollution from solid waste: The production of denim produces solid waste composed of residual dye and chemical sludge, potentially hazardous to dispose of.

Companies can take several actions, such as the following, to reduce the adverse effects of denim processing on the environment:

• Employing natural dyes: Unlike synthetic dyes, natural dyes derived from plant extraction are less damaging to the environment.
• Recycling water: Businesses can put water recycling systems in place to cut down on process water usage and water pollution.
• Correct wastewater treatment: To reduce the number of pollutants released, denim processing wastewater should be processed before discharge.
• Using environmentally friendly chemicals: Businesses can transition to environmentally friendly, less damaging chemicals.
• Correct waste maintenance: Solid waste produced during the production of denim should be carefully managed, such as through recycling or secure disposal.

Pollution and Remedies in Washing Process: Denim processing requires washing to give the cloth the proper feel and appearance. Yet, there are several other ways that washing might cause pollution.

• Water pollution: Washing in denim produces a lot of effluents, which may be highly contaminated with chemicals and dyes. This effluent can harm aquatic life and pollute surrounding waterways if it is not adequately treated.
• Energy usage: The washing process uses a lot of energy, which can increase emissions of greenhouse gases and the effects of climate change.
• Chemical use: Certain denim washing methods call for the benefit of substances that can be hazardous to the environment but also human health, including enzymes, bleaches, as well as softeners.
• Microplastic pollution: Denim washing can produce microplastics, which are small plastic strands that can damage aquatic life when they enter streams.

Companies can adopt several measures, such as the following, to lessen the impact of washing on the environment while processing denim:

• Employing environmentally friendly washing methods: Businesses can utilize environmentally friendly cleaning methods like laser etching as well as ozone washing that use less water and energy and produce fewer pollutants.
• Employing environmentally friendly chemicals: Businesses can transition to environmentally and health-friendly chemicals that are less detrimental to the environment.
• Wastewater treatment: To minimize the number of contaminants released in wash water should be treated until discharged.
• Using recycled water: Businesses can set up a water recycling program to cut down on process water usage and water pollution.
• Using natural fibers: Businesses can use fibers that require less washing while being less prone to shed microplastics, such as organic cotton or hemp.

Conclusion: The production of solid waste, energy utilization, greenhouse gas emissions, and water and air pollution are just a few of the adverse effects that denim manufacturing can have on the environment. Denim processing businesses can, however, take a number of steps to lessen their environmental impact and support sustainability. The use of natural dyes, the implementation of water recycling systems, the treatment of wastewater, the use of eco-friendly chemicals, the use of sustainable washing methods, the use of recycled water, and the use of natural fibers are some of these steps. Companies that produce denim can lessen their environmental effect, lower their carbon footprint, and increase their overall sustainability by implementing these sustainable practices. The denim industry must take responsibility for developing sustainable methods to reduce environmental damage and must be aware of its impact on the environment. By purchasing denim items created with sustainable methods and pressuring businesses to do the same, consumers can play a significant part in advancing sustainability.

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