**3. An overview of recycling in textiles and apparel**

An average person buys 60% more clothing items every year and keeps them for half as long as they used to keep about 15 years ago. It is assumed that overall consumption of textiles will have reached to 102 million tons by 2030 and that the textile industry's waste will have increased by about 60% between 2015 and 2030. That means the total level of fashion waste will reach to 148 million tons in 2030. As is known, the majority of clothing waste ends up in landfills or is incinerated, and once in landfills, it takes hundreds of years for natural fibers to decompose and may release methane and CO2 into the atmosphere. Synthetic materials, on the other

worn-out appearance. Pumice stone is used to stonewash denim garments. The stone gets abraded during the process and becomes powdered; part of it remains in the liquor, and part of it sticks to the garment. A sizeable amount of water is required for repeated washing cycles to remove the deposited pumice from the denim. The effluent and pumice dust lead to environmental pollution. Sandblasting is a mechanical finish which uses sand containing silica. The minute silica dust

Micro sanding is another finish which pollutes the environment. In the case of chemical washing involving the use of sodium hypochlorite or potassium permanganate, the effluent contains chlorinated organic substances which cause severe impacts to the environment, and the bleaching chemicals are harmful to human health. Acid wash uses both pumice stone and chemicals, namely, sodium hypochlorite or potassium permanganate, and it does not require water but leads to pollution through the effluent having pumice dust and residual manganese which

Despite all these setbacks of the denim processes summarized above, various suitable treatment processes have been developed and employed for the dyeing effluent on the basis of the nature and complexity of the dyes and chemicals present in denim. Fortunately, many denim companies and their suppliers have been striving hard to embrace greener methods such as laser processing and nano bubble ozone washing machines and are also making effort to develop new techniques of producing jeans, as a part of their business strategies to preserve the environment. They have also understood the importance and the need to build a sustainable

It is considered that sustainable material management is a precursor of circular economy, which promotes recycling, reuse, and remanufacturing. It was estimated that around 65 billion tons of raw materials were processed by the industrial system at the end of the first decade of the twenty-first century, and this quantity is expected to reach about 82 billion tons by the end of 2020. Therefore, in the last two decades, circular economy (CE) is gaining growing global consideration as the new development model which is capable of influencing the existing production and consumption model [15]. Within that concept, waste is classified on the basis of generation as pre-consumer textile waste, post-consumer textile waste, and industrial textile waste. Pre-consumer waste is the remaining production processes in the industry which includes raw material to finished products ready for market. This may include offcuts, shearing, selvedges, b-grade garments, export surplus, etc. which are homogenous and clean in nature to be used for other purposes. The waste under this class has great potential for reuse and recycling. The post-consumer textile waste can include any product that has completed its life cycle and is no longer useful to the consumer in both function and esthetics. Industrial textile waste is, however, the result of the manufacturing processes and is termed as dirty

The textile and apparel industry, which generates a substantial environmental footprint from cultivation, fabric and garment manufacturing, to the landfill disposal of post-consumer items, faces tremendous environmental and resource challenges [17]. In order to tackle such challenges to some extent, several fashion companies offer their customers to take care of their worn-out clothes including denim jeans. However, studies have concluded that less than 1% of these collected clothes are being recycled while nearly 80% of them are mainly sold on the secondhand market in poor countries around the world or used as blankets or isolation

spreads in air, it poses serious respiratory disease such as silicosis [10].

are hazardous [11–12].

*Waste in Textile and Leather Sectors*

business [12–14].

waste [13, 16].

**62**

**2.2 Sources of denim waste**

hand, are not designed to decompose and may release toxic substances into groundwater and the surrounding soil. If the average life of clothing could be extended by only 3 months, it would reduce waste generation as well as their carbon and water footprints, by 5–10% [19, 31–34].

2.Downcycling where the product of the recycled material is of lower quality. As the length of fibers is shortened and the constituent of molecules is reduced by wear, laundry, and recycling process, the textile recycling is often in the way

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

3.Upcycling where the product of the recycled material is of higher quality.

4.Open-loop recycling covers a concept in which a product's raw material is separated to be utilized as a part of a randomly used item. Generally, the second item is not recycled and discarded toward the end of its life.

5.Closed-loop recycling refers to recycling techniques where the material

• Recycling pre- or post-consumer textile waste.

within industry to create the same products again.

Downcycling can be equalized with open-loop recycling system in which the reclaimed material is used to make a less valuable product than the disposed one. Therefore, it results in little economic value and low environmental

recycled is a similar material which is being delivered. For example, the waste material reenters a piece of clothing production chain. Closed-loop recycling generates a greater impact on sustainability, and a product remains in a circular stream and retains its material quality. There are a number of ways to define closed-loop recycling approaches in the apparel industry. Three of them

• Cradle-to-cradle (C2C) methodology in which waste is reclaimed and used again in the production of products of the same or higher value. Biological waste can be composted, while technical waste can be reused

• Closed-loop reuse of existing garments: Although reuse of garments is not recycling in the sense of breaking down a product into its raw materials, the product may enter a new life cycle within the same production chain.

Textile recycling technologies are also categorized into four classes as primary, secondary, tertiary and, quaternary approaches [13, 40, 42–43]. Primary recycling involves recycling of material in its original form for recovery of equal value. Secondary recycling incorporates processing a post-consumer product into raw materials usually by mechanical means into a product with different physical and/or chemical properties (mechanical recycling). Tertiary includes processes like pyrolysis and hydrolysis, in which waste is converted to basic chemical constituents, monomers, or fuels (chemical recycling). Quaternary (recovery) covers waste-toenergy conversion processes such as incineration of solid waste or utilization of heat

Recycling is the process of breaking down a product or material to make a material of a higher or equal value (upcycling) or of a lower value (downcycling), in which textiles are commonly mechanically or chemically broken down to their fiber constituents [41]. Biodegradation is another method used to recycle waste and to

of downcycling.

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

benefits.

are [41]:

generated.

**65**

**3.1 Textile recycling techniques**

break down organic materials into compounds.

The textile industry's linear model of "make, use, and dispose of" represents an apparent pressure on scarce natural resources. Circular economy, on the other hand, aims to move away from the unsustainable linear model by decoupling economic activity from the consumption of finite resources and designing waste out of the system. When the recycling component is included, it helps to absorb the residuals of industrial and consumer use [35–36]. Accordingly, circular economy's principles may be given as follows:


Within that concept, a five-step waste management hierarchy was introduced in order to direct toward a more sustainable behavior (**Figure 1**) [37].

Waste generation prevention has the highest significance followed by reuse. Reusing is the concept of using undamaged parts of used products for manufacturing activities. When textiles turn into waste and are disposed by their consumers, recycling offers the opportunity to save raw materials and energy as well as to reduce pollution. Product/material recovery includes the activities like repairing, refurbishing, and disassembling, performed to regain the product value at the end of its life cycle. To dispose generated waste is the last step of the hierarchy [17, 38–41].

Textile recycling routes can be categorized in different ways as follows:

1.Mechanical, chemical, thermal, and biological based on the nature of the process.

**Figure 1.** *Waste management hierarchy [38–39].*

*Understanding Denim Recycling: A Quantitative Study with Lifecycle Assessment Methodology DOI: http://dx.doi.org/10.5772/intechopen.92793*

	- Recycling pre- or post-consumer textile waste.
	- Cradle-to-cradle (C2C) methodology in which waste is reclaimed and used again in the production of products of the same or higher value. Biological waste can be composted, while technical waste can be reused within industry to create the same products again.
	- Closed-loop reuse of existing garments: Although reuse of garments is not recycling in the sense of breaking down a product into its raw materials, the product may enter a new life cycle within the same production chain.

Textile recycling technologies are also categorized into four classes as primary, secondary, tertiary and, quaternary approaches [13, 40, 42–43]. Primary recycling involves recycling of material in its original form for recovery of equal value. Secondary recycling incorporates processing a post-consumer product into raw materials usually by mechanical means into a product with different physical and/or chemical properties (mechanical recycling). Tertiary includes processes like pyrolysis and hydrolysis, in which waste is converted to basic chemical constituents, monomers, or fuels (chemical recycling). Quaternary (recovery) covers waste-toenergy conversion processes such as incineration of solid waste or utilization of heat generated.
