**1. Introduction**

Denim is one of the most prevalent fabrics worldwide, and therefore the environmental degradation associated with denim jean production is highly dangerous as the volume of jeans produced and used by consumers today is humongous. Also, as cotton is the fundamental building block for denim production, denim represents a mainspring for cotton consumption. Considering the fact that the textile and apparel industry in general is pressured to increase the recycling potential for cotton to cover contemporary and prospective market demands, the use of recycled materials (fiber, yarn, and fabric) in the production of new denim products has become an area of great interest. The decision to use recycled materials in products occurs during design and product development, and it continues throughout the manufacturing processes. The most important requirements for recyclable denim

designs are monomaterials, elimination of toxic substances, modular manufacturing for ease of removal or exchange, easily compatible materials, and labels or codes that can be recycled.

In 2019, the global denim market was valued at approximately 90 billion US dollars and is expected to reach a value of around 107 billion US dollars by 2023 [5]. The global denim jean market size, on the other hand, was valued at USD 64.62 billion in 2018, and it is estimated to expand further at a compound annual growth rate (CAGR) of 6.81% from 2019 to 2025 [6]. The Asia-Pacific region led the market in 2019, which was followed by North America, Europe, South America, and the Middle East as a response to the introduction of global brands and an emphasis on premium denim. Japan, China and India are expected to lead the region through 2024 as a result of the countries' rise in promotional activities within the denim

*Understanding Denim Recycling: A Quantitative Study with Lifecycle Assessment Methodology*

According to the World Denim Fabric Foreign Trade Report published by the Istanbul Textile and Raw Materials Exporters Association (ITHIB), global denim fabric exports increased by 5.1% in 2018 and reached approximately 5 billion US dollars. The top five countries performing most denim exports are China (42% share of total exports), Pakistan (11.7% share of total exports), India (8.2% share of total exports), Hong Kong (7.4% share of total exports), and Turkey (6.8% share of total exports). It is stated that there is a strong growth in the denim production in Bangladesh and Vietnam, although these countries are mostly importing denim

Europe, the United States, and Japan are the biggest consumers of denim, whereas China and India, being relatively younger economies, are witnessing a steady rise in demand for denim. In 2018, men's wear segment accounted for the largest market share of more than 55%. It is forecasted that the segment will retain its leading position over the upcoming years mainly because of the improved standards of living and demand for trendy fashion apparels. Women's wear segment is, on the other hand, expected to register the fastest compound annual growth rate (CAGR) of 7.25% from 2019 to 2025. This growth is attributed to the high product demand, especially in emerging countries. In addition to that, constant product innovation in this segment is also expected to drive the growth further [2, 6].

It is estimated that producing a pair of jeans consumes around 2900 liters of water and large amounts of chemicals and energy. If this is multiplied by the number of jeans produced globally, one can get an idea of the enormous contribution of wastewater and harmful gases by denim industry to the environment [8, 9]. Indigo dye is one of the organic colorants used to color textiles, paper, leather, and plastic and for many applications such as cosmetic and photochemical production. Unfortunately, textile effluents containing indigo dye and other dye types make water toxic and harmful for human and animal consumption, which causes an imbalance in different aquatic ecosystem food chains [10]. The use of synthetic indigo and sulfur dyes also presents serious effluent problem. Bearing in mind that majority of warp dyeing for denim uses indigo and sulfur dyes, the environmental

impacts of denim processing can be classified into three main categories:

• Air pollution: cotton dust, abrasives, and chemicals found in air

• Water pollution: dyeing and finishing effluent discharge in water bodies

As is well-known, denim washing is imparted to fabric to improve the softness,

comfort, and most importantly achieving a variety of looks such as a faded or

**2.1 Environmental impacts of denim processing**

• Solid waste (sludge)

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market [2, 4].

*DOI: http://dx.doi.org/10.5772/intechopen.92793*

fabric [7].

The environmental impact of denim products, during manufacture, use, or disposal, can be evaluated by looking at the different phases of the product's life cycle and taking action at the phases where it will be most effective to reduce the impact. However, the lifecycle of a product is long and complicated, covering many areas with many people involved in each phase [1]. There is a variety of voluntary and mandatory tools which help achieve this objective. These include economic instruments, bans on certain substances, environmental labeling, voluntary agreements, product design guidelines, etc. Life cycle assessment (LCA) methodology is one of the aforementioned tools, and within the frame of this chapter, it is adopted to quantify and compare the environmental impact of recycled denim fabrics. But before that, the global denim market, environmental impacts of denim manufacturing, sources of denim waste, and recycling processes currently used in textiles and apparel today are also discussed in this chapter.
