Abstract
Introduction
The textile industry is one of the world’s largest polluters, generating millions of tons of waste annually and contributing significantly to greenhouse gas emissions.1–4 Each year, the world generates a staggering 92 million tons of textile waste, and the figure is projected to soar to 134 million tonnes by 2030 without drastic changes. Moreover, the textile industry accounts for a shocking 10% of global greenhouse gas emissions. 5 For example, the United States produces a staggering 16.2 million tons of textile waste per year, of which a mere 15% is recycled. 6 In China, only 3.5 million tonnes of textile waste are recycled, despite 45% of the total textile waste being discarded. 7 The European Union generates 16 million tonnes of textile waste, and recycling is only 26%. 8 So, regenerating and utilizing textile waste as resources has become a global focus not only to create economic opportunities but also to tackle environmental pollution. Nowadays, various textile wastes have been employed as reinforcement in producing green composites for sustainability across multiple applications. Cotton fibers are among the most widely discarded textile waste materials. Regenerating textile waste as resources has become a global focus, not only to create extraordinary economic opportunities but also to tackle environmental pollution. Utilizing recycled cotton waste fibers as reinforcement is a promising research area due to their availability, biodegradability, low cost, and favorable mechanical properties. However, further research is needed to fully understand the potential and role of cotton fibers as reinforcement in composite and laminated non-woven applications. This literature survey explores the technologies, equipment, methods, and materials used to recycle waste cotton fiber, yarn, fabric, and apparel. It first examines the different types and forms of cotton waste (fiber, yarn, fabric, apparel) and discusses their typical sources. The paper continues to explore the different methods, systems, technologies, and equipment used to recycle waste cotton textile materials. The paper will also extensively explore the use of recycled cotton and cotton product waste materials as reinforcements in different matrices to develop sustainable and biobased wearable and non-wearable products, including composites for various applications such as automotive, construction, agriculture, defense, furniture, sports, and packaging. Additionally, the paper highlights the technical challenges, trends, and issues in recycling cotton fiber towards more sustainable practices and how these can be addressed. Moreover, it discusses the current and future opportunities in terms of economic viability, including cost reduction, market potential, and environmental impact.
Overviews of textile waste materials
Textile waste can be broadly divided into post-consumer and pre-consumer waste, both of which have distinct characteristics and recycling implications.
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Pre-consumer waste is by-products generated in manufacturing processes, such as spinning waste, cutting waste, yarn residue, and spoiled or rejected materials.
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These wastes tend to be cleaner, less soiled, and more uniform in fiber length and composition, and hence more suitable to recycle into high-quality materials. In contrast, post-consumer waste comprises worn, used clothing and home textiles that are discarded.
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They are susceptible to fiber degradation, contamination (e.g., finishes, dyes, blended fibers), and intensive cleaning and sorting. Pre-consumer waste is primarily recycled into yarns, nonwovens, and green composites with relatively lower processing, while post-consumer waste is more technically challenging but with greater environmental impact potential when recycled. Pre-consumer recycled cotton finds applications like insulation products, padding, and industrial cleaning cloths, while post-consumer recycled cotton is increasingly being studied for use in nonwoven composites, building materials, and even chemically and mechanically regenerated fibers. Both streams must be contrasted to best optimize recycling technologies and achieve maximum resource recovery in a circular textile economy. China and the United States are the world’s leading producers of textile waste by a significant margin. Both nations whip out billions of clothing items annually to meet high consumer demand. For example, China generates the most textile waste, at a staggering 20 million tonnes per year, followed by the USA, which generates 17 million tonnes, and India, which generates 7.8 million tonnes (Figure 1(a). European countries also contribute a substantial amount, led by Italy and Germany (Figure 1(b)). European countries like Italy, Germany, France, and the UK also contribute significantly. This translates to China accounting for 43.4% of global textile waste, the USA at 36.9%, and India at 16.9%, with the remainder spread across other countries.
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The escalating problem of textile waste highlights the urgent need for more efficient recycling processes. This is not just an environmental imperative but also an economic necessity. Textiles and apparel are indispensable to daily life and are a cornerstone of the global economy. Production has surged over the past 15 years, transforming the industry into a $1.3 trillion powerhouse employing more than 300 million people worldwide.
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To meet specific performance requirements, including exceptional strength, heat resistance, or chemical resistance, specialty fibers are also engineered. Additionally, many products combine various polymers and other materials, such as blended textiles, carpets, conveyor belts, and composites.
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(a) Global textile waste percentage sharing by country; (b) Textile waste generation per year (Figures developed based on BusinessWaste.co.uk data).
Basically, textile industrial waste comprises materials generated during the manufacturing of fibrous products. Its composition varies widely, ranging from single polymers to complex multi-material blends, depending on the production stage. Given the higher value and recyclability of single polymers, implementing a robust corporate recycling process to separate waste by component carefully is crucial. This approach not only enhances recycling efficiency but also aids in identifying waste sources and developing strategies to minimize generation. 15 The post-consumer waste is a discarded fibrous product after their useful life. Due to the high fiber consumption and the prevalent practice of replacing worn-out or outdated products with new ones, the volume of post-consumer waste is substantial. It closely mirrors fiber consumption rates. 16 The circular economy aims to replace the traditional linear model of consumption with a more sustainable approach that emphasizes resource conservation and reuse. 17 The textile and fashion industry can significantly reduce material waste and reliance on virgin resources through the adoption of circular economy principles. Material waste is a critical environmental and economic challenge within the textile supply chain. Khairul Akter’s team found that cotton textile production generates a significant amount of waste, representing approximately 55.8% of the fiber processed. 18 At the same time, the remainder is disposed of in open dumps or, less frequently, landfills, contributing to various environmental problems. Bangladesh, the world’s second-largest apparel maker after China, produces around 577,000 tons of textile waste yearly.19,20 Besides, China is on track to produce over 100 million tonnes of pre-consumer textile waste annually, a major contributor to the country’s environmental and human health crises. 7 The circular economy offers a promising solution to the environmental burden of textile waste. However, implementing circular principles within the complex textile supply chain, characterized by its extensive length, numerous suppliers, and technical challenges, presents significant obstacles. 21 To achieve a circular textile production system, it’s essential to recycle the surplus materials generated during production and the inevitable waste products like yarn and fabric scraps. 22 Such a recycling process for textiles typically involves several key stages: fiber, yarn, and fabric recycling.
Fiber recycling
Mechanical fiber recycling is a well-established process with a history dating back nearly 250 years, capable of handling significant volumes. 23 Textile recycling presents significant challenges in achieving 100% recycled garments. While the need for chemicals, dyes, and water is generally reduced due to color sorting, the quality of recycled fibers often falls short of producing high-quality garments, except first-time recycled wool. 24 Recycled cotton fibers are shorter than those of new cotton, which can affect their quality. To make up for this, recycled cotton is often mixed with longer fibers, either from new cotton or polyester. The amount of recycled cotton in yarn can range from 20% to 90%, depending on the type of product being made. Durable fabrics like denim currently incorporate only around 20% recycled cotton from used clothing, though recent advancements have increased this to 40%. 14 Utilizing factory offcuts can significantly boost recycled fiber content as fiber quality declines during product use. Hilaturas Ferre produces a yarn that blends 90% recycled cotton with 10% of other fibers like polyester, nylon, acetate, linen, viscose, or wool. Recycled wool is a popular choice due to its lower cost compared to virgin wool. Companies like Wolkat and Geetanjali employ specialized technologies for this purpose. Moreover, Prato, Italy, has a history of transforming wool scraps into affordable “regenerated wool” garments. 3C Filati even claims to offer fully recycled product.9,14,24
Yarn recycling
Yarn recycling, while theoretically straightforward, remains largely untapped at an industrial scale. A key challenge lies in creating garments from a single yarn that won’t unravel, hindering widespread adoption. Technological breakthroughs, such as increased automation and 3D knitting techniques, offer promising solutions to the challenge of yarn waste. Benetton’s innovative single-thread knitwear, created using a specialized Japanese knitting machine and a single 450-m yarn, demonstrates the feasibility of this approach. To fully harness the potential of yarn recycling, further investment in research and technological development is crucial.25–27
Fabric recycling
Recycling fabric off-cuts is a common practice within the fashion industry. Companies like Nurmi Clothing, Reformation, Ahlma, and Looptworks exemplify this approach by transforming high-quality leftover materials from factories into new garments. These off-cuts are particularly suitable for recycling as they typically lack complex components such as buttons or seams.28–30 Finnish fashion retailer Lindex is giving new life to unsold denim. By repurposing and redesigning previous seasons’ garments, the brand creates fresh collections. This innovative process involves everything from adding subtle details to completely deconstructing and reconstructing denim into entirely new pieces.14,31–33 Digital startup Reverse Resources has developed a software-as-a-service solution to optimize factory cuts, including fabric scraps, for recycling. While small-scale fabric recycling initiatives already exist for post-consumer materials, these often lack the consistency required for large-scale production. However, there’s a growing demand from independent designers for unique, bespoke garments made from these leftover materials. For instance, Eileen Fisher’s “tiny factory” repurposes excess customer returns into new clothing items, demonstrating the potential of upcycling in the fashion industry.34–36 C-Tech’s innovative Wear2 microwave technology streamlines the recycling process by simplifying disassembly. The company’s dissolvable yarn breaks down in a microwave, transforming leftover fabrics into recyclable materials.14,37 Cotton can be recycled mechanically without the need for additional chemicals when blended with virgin fibers. Additionally, its high cellulose content enables chemical recycling into materials like lyocell or viscose.38–41
Recycling processes and technologies for cotton and cotton blended waste
Cotton, the soft, white fiber that has clothed humanity for millennia, has become an integral part of our daily lives. From apparel to home furnishings, their versatility is undeniable. However, the production and consumption of cotton also generate a substantial amount of waste. This waste, often overlooked, presents a significant environmental challenge while simultaneously offering a golden opportunity for innovation and sustainability.42,43 The cotton industry, from cultivation to final product, leaves a considerable ecological footprint. Water scarcity, pesticide use, and deforestation are pressing issues associated with cotton production. On the end of the consumption, the fast fashion industry, characterized by rapid turnover and low-quality garments, exacerbates the problem. Billions of pounds of textile waste end up in landfills each year, decomposing slowly and releasing harmful greenhouse gases. 44 Cotton waste is a complex issue with various forms. Pre-consumer waste arises during the manufacturing process, including fabric scraps, yarn remnants, and lint. Post-consumer waste comes from discarded clothing, bedding, and other textile products. Both types of waste possess valuable fibers that can be recovered and repurposed.45,46 Recycling cotton waste is a great way to help the environment. It keeps cotton out of landfills, saves resources, and reduces pollution. Plus, it creates jobs and boosts the economy.47–49 The potential applications for recycled cotton are vast. It can be transformed into new textiles, insulation materials, paper, and even biofuels. Advancements in recycling technologies have made it possible to recover high-quality fibers from cotton waste, enabling the production of garments and other products that rival those made from virgin cotton.
Pre-processing: sorting and cleaning
Before diving into the heart of recycling, waste cotton undergoes a crucial pre-processing stage. Pre-processing is a critical initial step in cotton waste recycling. It involves meticulously sorting the waste into different categories based on fiber type, color, and contamination level. This meticulous process ensures that the recycled material maintains its quality. Subsequently, the sorted waste undergoes a thorough cleaning process to remove impurities such as dirt, oil, and other foreign substances. This cleaning step is vital to prevent defects in the final recycled product and to optimize the recycling process’s efficiency. 45
Sorting
Textiles are meticulously sorted based on crucial factors such as fiber content, color, and condition, a step acknowledged as fundamental for ensuring efficient downstream processing and minimizing contamination within recycled materials. While this initial categorization is essential, our analysis suggests that the accuracy and efficiency of current sorting techniques, particularly when relying heavily on manual labor, present significant limitations. The inherent variability in human judgment can lead to inconsistencies, impacting the quality of the recycled output. Furthermore, the increasing complexity of textile blends poses a considerable challenge for rapid and precise identification. In our opinion, future advancements in automated sorting technologies, incorporating spectroscopic analysis and artificial intelligence, hold the key to overcoming these limitations and significantly enhancing the efficacy of textile waste recycling. The two main categories of sorting techniques for textile waste, while providing a foundational framework, highlight the need for continuous innovation in this critical initial stage. 46
Manual sorting
This is the traditional method and remains dominant for several reasons. Firstly, it’s well-suited for identifying textiles appropriate for reuse, which is a major goal for many sorting facilities. Manual sorting allows for inspection of the condition, style, and potential resale value of each garment. Secondly, it doesn’t require a high upfront investment in technology. However, manual sorting also has limitations. It’s labor-intensive and can be slow. Additionally, accurately sorting textiles by fiber content for recycling purposes is difficult to do by hand, especially for blends or mixed fabrics. Sorters carefully examine each item, checking its condition fabric (by feel and labels. It’s tough to tell exactly what fibers something is made of just by looking at and feeling it, and sorting everything by hand takes a lot of time and effort. Plus, the quality of sorting can vary depending on the person doing it.50–52
Automated sorting
Automated Sorting is a field that’s rapidly gaining traction. This is driven by the need for faster and more precise methods to sort textiles for recycling. Different technologies are employed to achieve this.
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These technologies can identify, and separate textiles based on various properties of the fabric. Several technologies are being explored to automate textile sorting and improve efficiency.
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The following are examples of automated sorting for textile waste. (i) Sensor-based sorting
Sensor-based sorting is the umbrella term for any sorting that uses sensors to identify and separate materials. This can involve various sensors like cameras (optical), metal detectors, X-ray scanners, and more. Conveyor belts equipped with sensors can identify different fiber types based on properties like near-infrared (NIR) spectroscopy.
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This allows for more accurate sorting by fiber content for recycling. Nowadays, different recycling companies use NIR with a color identifier or an RGB system. As shown in Figure 2, an electromagnetic wave (NIR sensor) is transmitted to the sample for analysis, where it interacts with the sample’s chemical structure (molecules, atoms, bonds, etc.). The wave is then measured in post-interaction, leading to the creation of a spectrum representing the sample’s unique chemical fingerprint. By comparing this spectrum with a database of pre-recorded reference spectrum, the composition of the analyzed item can be determined.
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Developing a robust materials recognition system for textiles requires a comprehensive reference library of material samples. These samples must align precisely with the desired sorting categories, such as pure materials (e.g., 100% cotton), material blends (e.g., 50/50 cotton/polyester), or related material families (e.g., cellulose fibers). To ensure accurate sorting, each category should be represented by enough diverse samples. All samples must be scanned using the same spectrometer that will be employed for the sorting process.
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Sensor-based sorting of textile waste
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NIR has limitations in accurately identifying materials with complex structures, such as textiles. Its inability to penetrate beyond the surface can lead to the misidentification of items with non-uniform 3D characteristics, like layered clothing. Additionally, factors such as coatings, thread types, and weave patterns can interfere with material recognition.58,59 While NIR is a valuable tool, alternative spectroscopic techniques offer greater potential for textile identification. Raman, mid-infrared (MIR), terahertz, and nuclear magnetic resonance (NMR) spectroscopy can provide a more comprehensive chemical composition analysis.60,61 However, their practical application in textile sorting is currently hindered by several challenges. These include the significantly higher cost of equipment compared to NIR, a relative dearth of research on textile recognition using these methods and limited or nonexistent implementation in waste sorting processes. (ii) Optical sorting
Optical sorting is a specific type of sensor-based sorting that relies on cameras and light detection to identify and sort materials. It uses visible spectrum (VIS) cameras. VIS cameras capture images in the red, green, and blue (RGB) color spectrum.
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This allows the machine to sort textiles’ color and near-infrared (NIR) spectroscopy to analyze material composition. This technique uses cameras and machine learning to identify textiles based on color, pattern, and potentially even material type. For example, NIR + COLOR (RGB) sorting is a type of optical sensor-based sorting. Because of optical, it uses light to identify and sort materials. NIR analyzes the material’s composition based on its interaction with near-infrared light. COLOR (RGB) cameras capture images in the visible red, green, and blue spectrum for color-based sorting.
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Both automated sorting methods are still under development, but they promise faster, more accurate sorting in the future. (iii) RFID sorting
Radio-frequency identification (RFID) technology is emerging as a potential solution for textile sorting. This system employs radio waves to identify and track objects. Small RFID tags attached to items communicate with RFID readers, enabling data to capture without direct visual contact. Unlike near-infrared spectroscopy (NIR), which identifies dyes and finishes, RFID focuses on tracking specific textiles. 64 Tiny RFID labels containing unique identifiers are affixed to products. These labels allow for remote data retrieval, including serial numbers and manufacturing data, from a connected database. The fashion industry is a leading adopter of RFID technology, utilizing it for supply chain management, inventory control, and loss prevention. 65
RFID technology has the potential to revolutionize the textile industry. By embedding RFID labels containing textile composition and color information into clothing during manufacturing, we can significantly enhance end-of-life sorting processes. Once a garment reaches its end of life, the embedded RFID chip can be read remotely, enabling precise and efficient sorting by material and color. This would streamline recycling operations, reducing costs and environmental impact. 66 While the concept is promising, widespread implementation faces challenges. These include securing industry-wide adoption, establishing standardized data and RFID tag protocols, effectively managing vast amounts of data, ensuring chip durability, and overcoming societal and cultural barriers. Despite these hurdles, the potential benefits of RFID-enabled textile sorting make it a compelling area for further research and development. 67 Automation significantly enhances textile waste sorting by accelerating the process and improving accuracy, resulting in a more consistent material quality for recycling. This consistency is vital for optimizing downstream recycling operations. However, implementing automated sorting systems requires a substantial initial investment. It may have limitations when handling certain textile types, particularly complex blends, which can still require some human expertise for accurate identification. 68
Cleaning
Textile recycling facilities sort used textiles by fiber type, quality, and intended use. After sorting, cleaning is the next critical stage. This cleaning process removes dirt, debris, and contaminants from the textiles. 69 There are several reasons why cleaning is essential. Firstly, clean textiles are easier to process further. Whether the textiles are destined for a second life as used clothing or are broken down into fibers for new products, cleanliness improves quality. Dirt and debris can damage fibers, reducing their value. Additionally, cleaning ensures the hygiene of recycled textiles, particularly those intended for reuse. Finally, clean textiles can be more efficiently sorted by color and may require less water or chemicals during the actual recycling process. 70 Contamination by dirt, oils, and dyes needs to be removed. Techniques like mechanical cleaning (using de-dusting machines) and wet cleaning (with water and mild detergents) are employed. However, wet cleaning should be approached judiciously and avoided in certain scenarios. For instance, textiles known to be highly degraded or prone to excessive shrinkage or color bleeding during washing are often better candidates for mechanical cleaning methods alone. Similarly, for certain high-value or delicate vintage textiles intended for direct reuse, specialized dry cleaning or minimal intervention may be preferable to prevent damage. Furthermore, the water and energy consumption associated with wet cleaning must be carefully considered, especially when dealing with large volumes of textiles or in regions with water scarcity. In such cases, optimizing mechanical cleaning or exploring alternative low-water cleaning technologies may be more sustainable options.
Cotton waste recycling methods
The ever-expanding textile industry generates an undeniably substantial volume of cotton waste, posing significant environmental challenges. While the imperative to recover valuable fibers from this waste to promote sustainability and mitigate ecological impact is clear, our initial assessment suggests that the current adoption and optimization of cotton waste recycling methods still lag the scale of the problem. This review aims to explore the key methods employed in cotton waste recycling, highlighting their inherent potential to transform discarded materials into valuable resources for bio-based nonwoven and composite materials. However, we contend that a more critical evaluation of the efficiency, scalability, and environmental trade-offs associated with each method is essential for truly advancing sustainable practices. The following are major methods, each requiring careful consideration of its practical implementation and overall impact:
Mechanical recycling
After preparation, non-fibrous materials like buttons, zippers, and trims are removed. The sorted cotton materials might be cut into smaller pieces for easier processing.
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Figure 3 shows the general conversion process of textiles, such as cotton waste, into recycled yarn. Following the removal of non-fibrous components and potential cutting of sorted cotton materials, the shredding stage is a critical step in mechanical recycling, directly influencing the sustainability and environmental footprint of the process. This involves the use of tearing machines, which employ robust rotating cylinders with aggressive teeth or wires to mechanically disrupt the fabric structure and liberate the fibers. The energy consumption and efficiency of these machines are key considerations from an environmental perspective. Subsequently, the material is often processed by a garnet machine, which further refines the fiber separation using a series of rollers with finer wire teeth operating at varying speeds. This more delicate action aims to improve fiber alignment and remove smaller impurities, ultimately impacting the quality and yield of the recycled fibers. Optimizing the operational parameters of both tearing and garnet machines, such as rotor speed, tooth configuration, and processing time, is crucial not only for achieving desired fiber characteristics but also for minimizing energy usage and waste generation within the mechanical recycling pathway, thus contributing to its overall sustainability. Mechanical recycling process of textile wastes into recycled yarns.
Shredding and opening
Cotton waste gets a new lease of life through a two-step process: shredding and opening. First, specialized machinery tears the material into smaller fibers, and this process is called shredding.
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This stage is crucial, as it aims to maximize the length of the resulting fibers for better reusability. The second step, opening, further refines the shredded cotton. Here, carding machines take over, separating and aligning the individual fibers.
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This well-established method relies solely on physical processes to transform cotton waste into a valuable resource. As shown in the schematic (A) Schematic workflow for the mechanical recovery of cotton fibers; (B) Physical Mechanical recycling process (a) material feeding to shredding machine, (b) shredding in several zones, (c) material delivery after shredding, (d) final bale making, (C) Pre-consumer textile wastes: (a) spinning hard waste, (C-b) woven cut clips and (c) knit cut clips, (d) garments cut clips (D) After shredding, pre-consumer recycled fiber obtained from (a) spinning hard waste & woven cut clip, and (b) knit cut clip. Post-consumer recycled fibers obtained from (c) second-hand garments cut clips
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Cotton fiber waste recycling is a multi-step process. As it is seen in Figure 4(b), First, the raw cotton fiber waste is fed into a shredding machine (Figure 4(b-a)). Then, the material is shredded in multiple zones to ensure complete fragmentation and then transported to the next stage, as illustrated in Figure 4(b-b). The materials then delivered for baling after shredding (Figure 4(b-c)). The final step of the process is bale making. It is the stage where the shredded fiber is compressed into bales for storage or further processing, as depicted in Figure 4(b-d). The recycled cotton fiber obtained from this process can be used in various textile applications. For example, Figure 4(d-a and b) illustrates the spinning of hard waste and woven cut clips, which are then used to create new fabrics. whereas Figure 4(d-c and d) demonstrates the knitting of cut clips of the post-consumer textile waste and garment cut clips procured from second-hand clothing shop, both are another method of utilizing recycled cotton fiber. The pre-and post-consumer recycled fibers obtained after shredding are shown in Figure 4(d-a, b and c). This illustrates how post-consumers recycle fibers, made from used clothing and fabric scraps, and could be used in new textile products to promote a more sustainable and circular economy.
Reliability index.
SCI measures the reliability of fiber. A higher SCI indicates better material quality and manufacturing performance. STR is the fiber’s resistance to breakage. It’s measured in grams per tex, where tex is a unit of linear density. MIC measures fiber fineness by assessing its linear density based on maturity. UHML is the average length of the longest 50% of fibers, measured in inches. UI measures the consistency of fiber length. It’s calculated as the percentage difference between the mean length (ML) and the mean length of the longest 50% of fibers (UHML). It is important to note that the constant term in the SCI formula, −322.98, is an empirically derived baseline value, likely originating from the statistical regression analysis used to establish the relationship between fiber properties and spinning consistency.
A researcher shredded different pre-consumer cotton scraps (loose vs tight-knit, dyed vs undyed) to see how it affects recycled fiber quality. They analyzed for fiber yield, length, spinnability, and final yarn strength. Shredding loose, undyed knits resulted in better-quality recycled fibers with higher yarn strength and less waste. Dyed fabrics overall produced lower-quality recycled fibers. 74 Recycled denim was used to create a textile reinforcement for epoxy resin composites. The denim, made entirely of cotton, was shredded into small pieces and blended to simulate the industrial tearing process. These recycled cotton scraps were then incorporated into epoxy resin composites. The addition of 30% recycled denim significantly improved the composite’s tensile strength and stiffness compared to pure resin. 75
Cleaning and refining
The shredded fibers may go through cleaning processes to remove dust, impurities, or any remaining unwanted materials. Carding machines are a common technology used to perform openings, mixing, cleaning, and parallelization. Carding machines utilize rotating cylinders with fine teeth to separate, clean, and align the recovered fibers for further processing. Refining can involve carding techniques, which align the fibers and remove any remaining short fiber fragments. Opening and picking machines further refine the fibers by removing impurities and preparing them for spinning. The types of machines can be drawn as frame machines, as indicated in Figure 5. The process uses a breaker draw frame and a finisher draw frame to produce more parallelized slivers. Carded slivers are fed into the breaker draw frame, where 6-8 slivers are combined to create breaker slivers. This stage also allows for mixing and blending. The breaker slivers then go through the finisher draw frame to create even more parallelized slivers. Textile waste blending and spinning process flowchart.
Blending and spinning
Mechanically recycled cotton fibers are generally shorter than their virgin counterparts. This length difference can be accommodated at both the fiber and yarn stages of production. Common textile machinery like blow rooms, carding machines, draw frames, and spinning frames can be used to blend recycled and virgin cotton fibers into a uniform yarn, as illustrated in Figure 5. Simplex performs mainly attuning the silver that comes from the drawing frame and making it ready for the next process, which is spinning. There are different spinning techniques. Even though ring spinning is the common one after the simplex process, an open-end spinning is also practiced in the recycling fiber production as it is capable of processing shorter and more irregular fibers, which are plentiful in recycled fiber. Open-end spinning is specifically preferred in the production of coarse and medium-count yarns utilized in the manufacturing of denim fabrics, towels, socks, upholstery fabrics, and industrial fabrics. It possesses high efficiency, lower power requirement, and tolerance to variation in fibers, thus making it a good method to utilize post-consumer and post-industrial textile waste in producing new yarns. Once the thin yarn is produced in the spinning machine, the autoconer machine changes the coped yarns into a big form of the cone for the best suitability of the next process. They might be blended with virgin cotton or other fibers to achieve desired properties in the final yarn. Finally, the blended fibers are spun into new yarns for use in textile production. The recovered fibers are then spun into new yarn for various applications. The final spinning can be performed using ring spinning, compact spinning, rotor spinning, and others.
A study investigated the potential of using recycled cotton from pre-consumer fabric waste in the production of elastic core-spun yarns for stretch denim. Recycled cotton fibers were blended with virgin cotton Figure 6(a) in varying proportions (10%–60%) and spun into 16 Ne (36.9 Tex) yarns. The addition of recycled cotton improved fiber control during the drafting process, allowing for a higher incorporation of recycled material (up to 60%) into the yarn (Figure 6(b)). The elastic yarn was then used as a core in the spinning process (Figure 6(c)). The yarns we produced were of very high quality. They were much smoother, had fewer flaws, and were stronger than regular yarns. They were among the top 5% to 50% best yarns according to the Uster Statistics 2023. Even the yarn made with 60% recycled material (as shown in Figure 6(d)) was strong enough to be used on a fast air-jet loom that runs at 950 rpm.
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Another research project explored the possibility of making denim fabric with dual-core elastic yarn from recycled cotton waste. A modified ring spinning process was employed to create these yarns, incorporating various elastomeric components such as T400®, PBT, PES, Lycra®, and both virgin and recycled cotton. The resulting Ne 18/1 yarns were assessed for strength, imperfection index, elongation, unevenness, and hairiness. As shown in Figure 6(e), compared to dual-core yarn made entirely from virgin cotton, the recycled cotton version exhibited lower strength and elongation, as well as higher imperfection index, unevenness, and hairiness values. This is because recycled cotton fibers may have undergone degradation due to factors such as exposure to sunlight, chemicals, or mechanical stress during their previous use. This degradation can result in weaker, shorter, and more damaged fibers, leading to lower overall yarn quality.
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(a) Virgin cotton; (b) recycled cotton; (c) spandex filament; (d) elastic core-spun melange yarn consisting of an elastane filament at the core, surrounded by a sheath made from a blend of recycled and virgin cotton fibers.
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; (e) yarn tensile strength, yarn elongation, and unevenness of 100% cotton and recycled yarn
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Cotton waste recycling for value-added textiles.
Chemical recycling
Chemical recycling is combined with mechanical recycling to improve the quality of recycled materials, especially for uses like food contact. This process transforms waste into high-value raw materials that would otherwise be discarded. This solution supports the circular economy, which promotes the use of waste as a valuable resource.77,78 Solvent-based technologies can recycle both natural and synthetic fibers. Cotton, lyocell, viscose, polyester, and other cellulose or plastic-based fibers can be processed using these techniques. While chemical recycling of cotton has achieved commercial scale, technologies for blended fabrics are still under development, progressing from research to pilot and industrial stages. To accelerate the adoption of chemical recycling, transparency in material composition and collaborative innovation are crucial. By deconstructing cotton at the molecular level, this innovative approach unlocks the potential to create entirely new materials.79,80 Current chemical polymer recycling processes convert pure cotton into cellulose pulp, a precursor for other regenerated cellulose fibers. While theoretically recyclable multiple times, the polymer chains within the cellulose degrade with each cycle. Additionally, research indicates that fiber quality deteriorates with each use, limiting the number of times the material can be recycled for apparel applications. 81 Further research is necessary to fully understand the potential for repeated recycling of this process, including effective methods for identifying and treating low-quality fibers. While several examples exist for recycling pure cellulose-based fiber streams, such as Lenzing’s Refibra lyocell fiber made from cotton scraps and wood, the industry is still in its early stages. Innovative companies are developing technologies to turn used clothing into new fabric. Renewcell, Infinited Fibre Company, and Evrnu are examples of this, with Evrnu even creating prototype jeans and T-shirts from recycled cotton in partnership with Levi’s and Target. 14 Chemical recycling presents a promising avenue for transforming cotton waste into high-quality recycled fibers or even innovative new materials. While these technologies offer substantial potential, their widespread adoption and optimization are essential to fully realizing their environmental and economic benefits. Several techniques have been developed for chemically recycling textile waste. The following section discusses the common chemical recycling methods.
Pyrolysis
This technique breaks down textile waste into smaller molecules using high temperatures (typically 400-900°C) in an environment with limited oxygen. In the absence of sufficient oxygen, the complex molecules in textiles decompose rather than burn. 76 The pyrolysis process breaks down plastics into their original components, making it a valuable method for recycling plastic waste. This process not only helps recover valuable materials but also reduces energy consumption as the reactor can be self-sufficient in heating. Currently, pyrolysis is the most advanced technology for recycling plastic waste on an industrial scale.82–85
Hydrolysis
This technique uses water, sometimes with added heat, acid, or enzymes, to break down the polymer chains in textiles. Such categories depend on the fiber, for example, polyester can be hydrolyzed with strong acids or enzymes. It also uses water and heat to break down polyester and other textiles into their base components, which can then be reused to make new fibers. For example, short cotton fibers were transformed into a renewable, self-reinforcing cellulose fiber composite paper (CCP). In research, denim waste was cut mechanically and passed through the bleaching process as shown in Figure 7(a). The recycled cotton fibers under 3 mm (Figure 7(b)) were converted into cellulose nanofibers (CNFs) through TEMPO oxidation (Figure 7(c)). Longer recycled cotton fibers (3-7 mm) served as reinforcement within a CNF matrix, bonded together by hydrogen bonding. Paper pulp was created by combining the recovered fibers and CNFs, which were then formed into CCP using wet-laid webs and hot pressing, as shown in Figure 7(d).
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When CNF content reached 5%, CCP exhibited a tensile strength of 86.68 MPa, surpassing commercial A4 paper by a factor of 1.8. Notably, CCP retained 75% of its dry tensile strength even when wet, whereas A4 paper experienced near-total loss. This remarkable water resistance expands CCP’s potential applications. CCP preparation from denim waste (a) denim waste mechanical treatment; (b) recycled cotton fiber preparation; (c) CNF preparation; (d) CCP preparation
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Another research has also demonstrated the dissolution of post-consumer garments (PCG) using suitable solvents as shown in Figure 8. For example, polyester fabric can be dissolved in trifluoroacetic acid and dichloromethane. This process enables the creation of nanofiber membranes that are applicable to air or water filter media.
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Transforming post-consumer garments (PCG) fabric into electrospun nano mat
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Glycolysis
Like solvolysis, glycolysis uses a solvent (often a glycol like ethylene glycol) to break down polyester waste. 87 However, unlike alcoholysis, it doesn’t necessarily aim for complete depolymerization into monomers. Instead, it can yield oligomers (shorter polymer chains) that can be used in various applications, like chemical intermediates or lower-grade recycled fibers. 88
Enzymatic/biological degradation, gasification and hydrothermal
This environmentally friendly approach uses enzymes specifically designed to break down certain types of fibers. 89 For example, cellulase enzymes can be used to break down cellulose in cotton waste. The enzymes act as catalysts, accelerating the natural degradation process. This method utilizes enzymes and biological catalysts to break down specific components of textiles. It’s particularly effective for natural fibers like cotton, where enzymes like cellulase can degrade cellulose polymers. The resulting breakdown products can be used for various applications, including biofuels or regenerated cellulose materials. Microorganisms or their enzymes can break down polymers into smaller pieces called monomers. These monomers can be used to make new products. This process can work with both bioplastics and traditional plastics. It might also help clean up pollution. 52 Besides, gasification uses high temperatures in an oxygen-limited environment to convert textile waste into combustible gas (syngas). The syngas can then be used for energy generation or further processed into fuels. Gasification doesn’t directly create new fibers, but it offers a way to utilize waste for energy production.90,91 Hydrothermal is considered an emerging technique that uses high-pressure hot water (typically above 180°C) to break down textile waste into valuable chemicals or precursors for new. 92 This process uses high-pressure and hot water (not necessarily boiling) to break down complex molecules in the textile waste. It can be used alone or combined with other methods like enzymatic treatment. Depending on the conditions and textile composition, hydrothermal treatment can achieve various outcomes, like breaking down dyes, weakening fiber bonds for easier mechanical recycling, or even converting biomass into usable chemicals. 93
Comparison of different techniques of chemical recycling.
Plasma technology and microwave-assisted recycling
The plasma technology method utilizes high-temperature ionized gas (plasma) to break down textile waste into valuable components. 46 It’s still under development, but researchers see the potential for depolymerization into usable monomers or even conversion into valuable chemicals. 92 However, the microwave-assisted approach uses microwave radiation to break down or modify textile materials. It’s being explored for various applications, such as separating blended fabrics or enhancing the digestibility of natural fibers for enzymatic recycling. 94 Considering the potential for both plasma and microwave technologies to offer novel pathways for textile waste valorization, particularly for complex waste streams, we recommend increased research and development efforts to optimize their efficiency and assess their overall environmental and economic feasibility compared to more established methods.
Fabrication of bio-based nonwovens from recycled cotton waste
Recovered fibers undeniably represent a valuable resource to produce nonwoven fabrics and various products, particularly for applications like insulation materials and wipes. The increasing popularity of recycled fiber nonwovens, driven by their perceived affordability, environmental advantages, and reasonably comparable performance characteristics, 95 is a positive trend. However, we believe a more nuanced perspective is necessary. While cost-effective in some respects, the overall economic viability often hinges on the efficient sourcing and processing of the waste stream. Furthermore, while generally considered environmentally friendlier, the specific ecological benefits are contingent upon the energy consumption and chemical inputs of the chosen nonwoven fabrication technique. Dry-laid, wet-laid, and air-laid web formation, along with mechanical bonding (such as needle punching), resin bonding, and thermal bonding, are indeed common techniques for producing bio-based nonwovens from recycled cotton wastes. In our assessment, the selection of the most appropriate technique requires a thorough evaluation of the desired end-product properties, the characteristics of the recycled fibers, and a comprehensive life cycle analysis to truly ascertain the environmental sustainability and optimal performance. 96
Needle punching
This method involves punching carded cotton waste fibers with barbed needles. The barbs interlock the fibers, creating a strong and dimensionally stable nonwoven fabric. In research, shredded 100% cotton waste is used to create nonwoven mats. The waste is first cut into fibers (see Figure 9(a)) and turned into mats using carding and needle punching (see Figure 9(b)).
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(a) Recycled cotton fibers; (b) Cotton nonwoven fabric
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Dry, wet and air-laid
The dry-laid method involves opening and cleaning of the cotton waste, followed by a carding process that orients the fibers predominantly in one or two directions. In contrast, the air-laid method involves spreading the fibers into a uniform layer using air currents, resulting in a more random fiber orientation. A bonding agent, often a resin or heat, is applied to create a web-like structure. This technique is known for its simplicity and is good for lower-strength applications.
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On the contrary, in the wet-laid process, a dilute slurry of cotton waste fibers is deposited onto a forming screen. Water is then drained, and the remaining web is bonded using heat, pressure, or a chemical binder.
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Like wet-laid, but instead of a water slurry, air is used to transport the cotton waste fibers onto a forming screen. Binders are then applied to create the final nonwoven structure. Cotton/Polyester garment waste was recycled for thermal and acoustic functions using the Air-Laid process. Waste materials from “cut and sew” knitwear production are used as raw input. Post-consumer knitwear scraps were collected from garment manufacturing facilities and sorted by color before recycling. These materials were processed in a reused fabric opener machine to yield recycled fibers. Subsequently, a carding machine was employed to convert the recycled fibers into air-laid webs of varying densities. Carding system of recycled fiber differs from conventional systems in that it handles short, irregular, and contaminated fibers from shredded fabrics in more powerful machinery (e.g., Garnett machines) and includes multiple opening steps, intensive cleaning, and waste removal units to recover usable fibers, whereas conventional systems handle longer, cleaner virgin fibers in weaker, single-stage processing. Polyvinyl acetate (PVA), as depicted in Figure 10(a), served as the binding agent for these webs. It is noteworthy that the binder primarily adheres to the surface layers and exhibits limited penetration into the relatively thick structure. Spray adhesive bonding ensures precise binder application, even distribution, and a soft fabric finish. Adhesive application is strictly controlled at a 20% add-on rate. Careful monitoring prevents excessive or insufficient adhesive flow from the sprayer. Finally, the nonwoven fabrics are obtained, as shown in Figure 10(b) and (c).
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Resin and thermal bonding
Comparison of different techniques for bio-based nonwovens from cotton waste.
Fabrication of bio-based composites reinforced by recycled cotton wastes
The ever-growing demand for sustainable materials has led to a surge in the development of bio-based composites. These composites offer a compelling alternative to traditional materials, combining the strength and versatility of composites with the environmental benefits of biodegradability and reduced reliance on petroleum resources. One particularly promising approach involves utilizing recycled cotton waste as reinforcement within these bio-based composites. 103 Discarded textiles and cotton byproducts present a significant waste stream and incorporating them into composites offers a valuable solution for both waste management and sustainable material production. Several fabrication methods can create these bio-based composites reinforced with recycled cotton. Each method offers distinct advantages and caters to different production needs. The best way to make cotton waste composites depends on what you want the final product to look like, how much you need to make, and what specific qualities you’re aiming for. Here are some popular methods used to create these kinds of materials.104–115
Hand lay-up
In this manual method, cotton fibers are arranged in a mold and then saturated with a bio-based resin. This process is repeated to build up multiple layers of the material Figure 11(a). To ensure a smooth, even finish, a vacuum bag is used to eliminate air pockets and compress the laminate. Hand lay-up is a versatile method suitable for producing complex shapes, but it is labor-intensive and has lower production rates compared to other methods. Researchers discovered that discarded woven fabrics can be used directly as reinforcing materials in composites without needing to separate individual fibers. The fabric’s consistent alignment ensures that the resulting composites have uniform properties. By using soybean-based bio-resins to reinforce cotton fabric, researchers created biocomposites with impressive strength and durability. Without any additional fiber treatments, these composites achieved a tensile strength of over 100 MPa and a modulus of over 10 MPa. Additionally, they exhibited an impact strength of over 70 kJ/m2.
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As shown in Figure 11(b), researchers employed cotton waste fabric as reinforcement and sawdust as filler with pp matrix using a hot press technique. Single cotton fabric fiber was sandwiched between layers of polypropylene and wood sawdust particles. The composites exhibited improved tensile and flexural properties when cotton fabric was incorporated.
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The composite was prepared using the hand lay-up method, using recycled cotton fibers (CFRC) with epoxy resin. As shown in Figure 11(c), the composite reinforced with 30% recycled cotton fiber had better flexural strength. 105 The composite tensile strength was significantly boosted by incorporating varying amounts of cotton fibers, as depicted in Figure 11(d). The flexural result was also high at 25 wt% cotton fiber. In another study, composites were prepared from recycled grey cotton fabric reinforced with polyester matrix in various configurations. All composites demonstrated good thermal stability up to 305°C, followed by a gradual mass loss (310°C–405°C), significant degradation (>405°C), and residual char at 655°C. Free vibration analysis revealed superior energy absorption properties in cotton-wool fiber composites compared to the other configurations. 1
Compression molding
Compression molding involves placing a pre-measured mixture of bio-based resin (e.g., epoxy) and cotton fiber preform into a heated mold cavity. The mold is closed under high pressure (typically 5–20 MPa) using hydraulic or mechanical presses (Figure 12(b)), and heat (100°C–200°C) is applied to cure the resin. This process is cost-effective for small-to-medium production runs due to low tooling costs, though cycle times increase with part thickness. Researchers utilized recycled cotton fibers blended with epoxy resin, varying fiber weight fractions (0.1–0.4), to produce 3 mm-thick thermoset composites. Cotton/epoxy composites exhibited superior mechanical strength compared to polyester/epoxy due to enhanced fiber-matrix adhesion (Figure 12(c)). Key advantages include simplicity, compatibility with natural fibers, and suitability for flat or moderately complex geometries (e.g., automotive panels, industrial mats). Limitations include slower cycle times for thick sections and challenges in achieving uniform fiber distribution.
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(a) Development process of textile waste-reinforced composite; (b) Compression molding technique; (c) comparison of flexural strength of Cotton-epoxy and polyester/epoxy composites
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Extrusion molding
In this method, the bio-based resin and cotton fibers are continuously fed into an extruder. The extruder mixes and heats the materials, forcing the molten composite through a die to create a desired shape (Figure 13(a)). Extrusion is a high-volume production process suitable for producing long, continuous profiles like pipes, boards, and films. Researchers studied composite materials made from silk fiber and cotton waste. These materials were shaped into various sizes and combined in different proportions with a plastic called polypropylene (PP). The materials were then processed using a double-screw extruder. The study found that adding more cotton waste to the composite improved its heat resistance and softening point. This was confirmed by Vicat softening tests and heat deflection temperature. Additionally, the cotton waste addition had a similar effect on the composite’s thermal properties as adding silk fiber. Finally, the impact strength and elongation of the composite increased when 6% cotton waste was added. This suggests that cotton waste can enhance the composite’s toughness and flexibility. As shown in Figure 13(b), the composite is made from 3% cotton waste, and 97% PP has a smooth surface, which indicates that the fiber and matrix are well harmonized. Some fibers were shown on the surface of the composite at higher magnification (Figure 13(c)). When cotton waste percentage increased to 6%, the SEM results showed a slightly rough surface compared to 3% cotton waste (Figure 13(d)). This result is clearly shown at a 750X magnification level (Figure 13(e)). This surface change may be because of the use of large sizes of recycled waste fiber.
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Injection molding
Injection molding is a high-pressure manufacturing process where molten composite material is forced into a closed mold (70–150 MPa) and rapidly cooled to solidify into precise, complex shapes. To integrate cotton waste into this method, preprocessing is essential. First, raw cotton fibers undergo cleaning to remove impurities, followed by chopping or milling into short fibers (0.5–5 mm) to ensure uniform dispersion. Due to cotton’s hydrophilic nature, thorough drying (e.g., 80°C–100°C for 4–6 h) is critical to reduce moisture content below 1%, preventing voids and interfacial defects during molding. To address compatibility issues between hydrophilic cotton and hydrophobic polymer matrices (e.g., PLA or recycled PET), coupling agents like maleic anhydride-grafted PLA (MA-g-PLA) are often incorporated to enhance adhesion. The prepared cotton fibers are blended with a thermoplastic matrix, such as biodegradable PLA or recycled plastics, using a twin-screw extruder. The mixture is melted at controlled temperatures (160°C–200°C, depending on the polymer) to avoid thermal degradation of cotton fibers, which can occur above 180°C. The molten composite is injected into a steel or aluminum mold equipped with cooling channels to ensure rapid solidification, with cycle times ranging from 30 to 120 s. After cooling, the finished part is ejected and trimmed. Research demonstrates that cotton fiber-reinforced PLA composites exhibit significant improvements in mechanical properties, including up to 25% higher stiffness and 15% greater tensile strength compared to pure PLA, as shown in Figure 14(c).
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While injection molding enables high-volume production of intricate parts like biodegradable food containers, agricultural tools, and automotive components, challenges persist. Cotton’s low flowability can lead to fiber clumping, necessitating optimized screw designs for even distribution. Additionally, the process is limited to thermoplastic matrices, excluding thermosets, and narrow processing windows due to cotton’s moisture sensitivity and thermal instability. Despite these constraints, advancements in material compatibility and process control continue to expand applications in sustainable consumer goods and packaging.
The composite, made from recycled denim fibers and polypropylene (PP), showed improved tensile strength compared to the unreinforced PP. The denim fibers were first bound with polyvinyl acetate and then pelletized with PP before being extruded into the composite. This new manufacturing process helped to preserve the beneficial properties of the recycled denim fibers. 119 Researchers have created eco-friendly and affordable composite materials using recycled cotton waste. By breaking down textile scraps into short fibers, they combined these fibers with a partially plant-based plastic (bio-PET). This new material is stronger, stiffer, and more resistant to heat than the original plastic alone. With the right amount of recycled cotton fibers, these composite pieces could be ideal for packaging food and other products. 120 Injection molding excels at creating intricate, three-dimensional forms with remarkable precision.121,122 This is due to it cast molten material into precision molds under controlled pressure and temperature. Such a high-pressure process forcing the material into every nook and cranny of the mold and helps to produce complex geometries, fine details, and uniform dimensions among high volumes of parts with ease, which makes it suitable for producing detailed and repeatable parts at high efficiency. Furthermore, injection molding offers precise control over fiber orientation within the part through mold design and how the process is run. This intricate control over both shape and fiber alignment makes injection molding ideal for creating complex parts with a smooth surface finish and minimal material waste.
Solution casting and resin transfer molding
To make a bio-based polymer composite, we first dissolve the polymer in a liquid to form a thick mixture. Then, we add cotton fibers to this mixture and spread it out on a flat surface. As the liquid dries, the polymer and cotton fibers stick together to form a solid film. This method is ideal for creating thin, flat materials (Figure 15). Solution casting.
The composite panels in Figure 16 were made by placing 100% cotton fabric on a nonwoven mat and covering it with perforated film and peel-ply. A vacuum pump was then used to eradicate air from the system and ensure that the resin fully infiltrated the fabric. After vacuum sealing, the resin was cured to create a composite panel. Although composite properties are generally different from those of virgin fibers, the chemical modifications in this process improved fiber-matrix adhesion, resulting in panels with promising characteristics. These lightweight panels with excellent mechanical properties showed substantial applications in different industries, including automotive and construction.
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Resin transfer molding (RTM) involves placing a dry cotton fiber preform into a closed mold, then injecting low-viscosity bio-based resin (e.g., epoxy, soy-based resins) under moderate pressure (0.3–1 MPa) until the preform is fully impregnated. The resin cures at elevated temperatures (80°C–120°C), forming a high-strength composite. Key considerations include resin viscosity (<500 cP) to ensure proper flow through the fiber bed and mold design with strategic inlet/outlet ports to minimize voids. RTM excels in producing large, intricate parts with consistent fiber alignment (e.g., automotive body panels, wind turbine blades). For cotton waste, studies show that surface treatments (alkali or silane) improve resin wettability, reducing porosity. Compared to compression molding, RTM offers better control over fiber placement and resin distribution but requires higher initial tooling costs. Resin transfer molding.
Vacuum infusion
Vacuum infusion is a manufacturing process used to create composite materials by drawing resin through dry reinforcement materials using vacuum pressure. This method (Figure 17(a) involves placing dry reinforcement materials in a mold, sealing the mold with a vacuum bag, and introducing resin into the mold. A vacuum pump is then activated to draw air out of the mold, forcing the resin to flow through the reinforcement materials. Once the resin has completely infiltrated the materials, the part is cured, solidifying the composite. Vacuum infusion offers several benefits, including high-quality parts, controlled resin-to-fiber ratio, reduced waste, versatility, and suitability for large-part production. By using recycled nonwoven materials like cotton, polyester, and cotton/polyester blends mixed into epoxy resin, this technique is widely applied in various industries, including aerospace, automotive, marine, wind energy, and sports equipment. As shown in Figure 17(b), the composite panels are made using a vacuum infusion process. Mechanical, thermal, and acoustic tests show that both the nonwoven fabrics and composite panels have good properties. These panels are promising for reducing noise and offer advantages over pure epoxy products.
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(a) Vacuum infusion method; (b) Composite produced by vacuum infusion method.
Bio-based composite materials reinforced by recycled cotton.
Sustainability and life cycle assessment of recycled cotton waste
Cotton wastes and its environmental impact
Globally, the textile industry is considered as the second largest source of pollution and waste, responsible for 10% of all carbon emissions and 20% of wastewater.124–134 In 2020, European clothing consumption per person used 9 cubic meters of water, 400 square meters of land, and 391 kg of raw materials, producing 270 kg of carbon emissions. By 2030, Emissions are expected to increase to 2.8 billion tons.135,136 The environmental impact of fiber production varies depending on the type of fiber. Polyester, the most widely used fiber, has an annual production of 54 million tons, while cotton, the most popular natural fiber, accounted for 24.5 million tons in 2013. However, cotton production has the highest water consumption, requiring 1559 L of water per kilogram of fiber. China leads cotton production, followed by India, the USA, Pakistan, Brazil, and other countries (Figure 18).
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China has become the global leader in cotton production and consumption. In fact, over the past 10 years, 40% of all fiber produced worldwide has been cotton. The Keqiao Industrial Park, a major textile hub in China, can produce a massive amount of cotton fibers enough to make nearly 19 billion pieces of clothing.138,139 The U.S. and the U.K. together produce over 16.8 million tons of cotton waste each year. This waste often ends up in landfills or incinerators, harming the environment.
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As one researcher reported in 2016, 76% of cotton waste in Australia was deposited in landfills.
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China, as a leading textile producer, generates a substantial amount of waste, with an estimated 26 million tons of clothing discarded each year.
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Waste cotton and cotton textile dyeing use energy, water, and chemical bleaching agents, generating significant wastewater and harmful environmental effects. Common fibers used in textile industries and their environmental impact
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Additionally, the use of gaseous fuel in cotton production leads to greenhouse gas emissions and the release of harmful pollutants, which contribute to climate change. 143 Therefore, owing to the problems and the global increase in fiber consumption, there is an urgent need for sustainable solutions to address the accumulation of cotton waste. A comparative study was done by some groups of researchers and found that waste recycling is a more sustainable approach to reducing environmental impacts than incineration or landfilling. 144
The circular economy and life cycle assessment of cotton wastes
Life Cycle Analysis (LCA) is a critical tool for assessing and evaluating the environmental impacts of cotton recycling, from raw material extraction to production, use, and end-of-life management.
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A linear economic system involves the conversion of raw materials into final products with short shelf lives, leading to waste accumulation. This system is not sustainable and requires a circular system as it lacks processes such as recycling, which is essential for a circular economy to be sustainable.
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Therefore, a circular system is necessary to replace the traditional linear economy, as shown in Figure 19. The circular economy is a system that aims to reduce waste by recycling and reusing materials. Instead of throwing things away, they are turned into new products. This helps to protect the environment and conserve resources.
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The 3 Rs of reducing, reusing, and recycling have expanded to 10 Rs, including refusing, rethinking, repairing, refurbishing, remanufacturing, repurposing, and recovering. Rethinking is a crucial step in creating more sustainable products and consumption habits. It encourages us to question whether we truly need something before buying it and to consider the environmental and social consequences of our choices. By rethinking our consumption patterns, we can make more mindful decisions and reduce our impact on the planet.148–150 Therefore, companies should incorporate environmental considerations into their design process, such as eco-design, as the product design phase significantly impacts the environment, accounting for 80% of a product’s sustainability performance.151,152 In addition, the LCA methodology, as applied to cotton textiles, helps to identify hotspots where interventions can have the most significant impact in reducing environmental burdens.153,154 LCA has demonstrated that utilizing recycled cotton can significantly decrease cumulative energy demand, eutrophication potentil, water usage, acidification potential, and global warming impact.
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Additionally, the use of recycled cotton has been associated with substantial savings in CO2, water, and oil equivalents when compared to virgin materials.
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However, some research studies compiled goals for LCA studies on textiles using the Higg Index, a suite of sustainability assessment tools for the apparel and footwear industry that measures environmental and social performance across the value chain, to benchmark textile life cycle impacts.157,158 The researchers examined how to turn textile waste into valuable products. They looked at the materials used, energy needed, and environmental damage caused throughout the process. Most studies have focused on making textiles and using them, but there’s still a lot to learn about the environmental impact when textiles are thrown away. This study shows that more research is needed in this area. The linear economy and circular economy system
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Sustainability and environmental benefits of recycling cotton waste
As mentioned in the previous section, the environmental effects of cotton cultivation and yarn spinning are intricate and varied. Key factors to consider during production include water usage, land use, emissions, and chemical application, even though there is limited literature on the subject.
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Therefore, the global challenge of cotton waste management is multifaceted and requires a combination of strategies to reduce environmental harm effectively.
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Sustainable practices such as recycling, reuse, and repurpose not only conserve resources, but also offer economic and environmental benefits. The adoption of these practices is essential for transitioning towards a circular economy, where the lifecycle of cotton products is extended, and waste is minimized.164,165 The European Parliament and Council (2008) emphasized that the optimal waste management strategy is to prevent waste.
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Reduce and reuse practices reduce waste, whereas textile materials can be recycled, incinerated, biodegraded, or disposed of in landfills after their lifespan, as shown in Figure 20. Implementing such strategies is imperative for the textile industry to address its environmental footprint and to contribute to broader sustainability goals. Textile waste recycling is a widely studied topic, with unblended cotton being the most frequently studied material. Mechanical recycling methods such as melt extrusion or cutting, shredding, and carding are the main methods used to manage fabric waste. Chemical and biochemical strategies comprise 38% and 14% of the studies analyzed, respectively, with chemical methodologies following depolymerization, repolymerization, or dissolution.167,168 Recycling mostly followed open-loop approaches (34%), with the construction and building sectors being the main contributors. However, the environmental benefits of recycling cotton are complex, primarily contributing to the reduction in the environmental burden associated with cotton production and textile waste.
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Textile waste management
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Recycling cotton conserves natural resources by reducing the need for virgin cotton cultivation, which is often associated with significant water and pesticide use. 169 For instance, the use of mechanically recycled cotton fibers in denim fabric production, as opposed to virgin cotton, has been shown to significantly improve various environmental impacts, including resource depletion, global warming potential, ozone layer depletion, and total water use. 170 Similarly, the use of recycled polypropylene (PP) fibers over virgin PP fibers and steel-reinforcing mesh resulted in significant environmental savings, 171 which suggests that similar benefits might be observed with cotton recycling. Additionally, the concept of avoiding problems shifting from one life cycle stage to another, or from one environmental impact to another, is crucial for assessing the true benefits of recycling cotton. 172 Recycling can mitigate the volume of textile waste in landfills, thereby reducing the associated greenhouse gas emission potential and water contamination. 173
Therefore, the transformation towards organic and recycled materials, as seen in the cotton textile market, is indicative of a broader trend towards sustainability, supported by LCA findings.
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To fully evaluate the environmental benefits of cotton recycling, further research that specifically focuses on the LCA of recycled cotton textiles is required. According to the literature, the reuse and recycling of textiles, including cotton, generally decreases environmental impacts when compared to disposal methods, such as incineration and landfilling, is. This is largely because recycling cotton conserves the resources and energy that would otherwise be expended in the production of new cotton fibers. Interestingly, while the environmental advantages of cotton recycling are well documented, certain studies highlight scenarios in which these benefits may not be as significant. For instance, if the production processes being avoided are relatively clean, or if the replacement rates of new products by recycled products are low, the environmental benefits may be reduced. Additionally, the environmental impact of customer transport for reused cotton products can sometimes exceed the benefits of avoided production unless the use phase is significantly extended.
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Future research is needed to optimize cotton recycling processes and explore new markets for recycled cotton, which could further enhance its environmental benefits.
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Denim jeans and jackets are the most extensively used global clothing, primarily made from 100% cotton fibers. The denim industry relies heavily on cotton, which is a source of waste. Therefore, the use of recycled cotton is being increasingly considered to mitigate these effects.143,169,176 Recycled cotton, derived from pre- or post-consumer waste, significantly reduces the environmental impact of denim production by conserving resources, minimizing the need for new raw materials, and reducing waste, as demonstrated by life cycle analysis.
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Studies on recycling in the denim industry are growing as textile waste is generated during production or after consumer consumption. This includes clothing or household items made of textile materials that are no longer needed and discarded.
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Yüksel and Korkmaz
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conducted a study on the life cycle analysis (LCA) of recycled cotton products for sustainable textile designs. This study found that the use of recycled cotton in denim production has been found to have a lower environmental impact than conventional cotton. The recovered materials, particularly cotton, can serve as a new source of material to address the high demand and supply issues in the textile water sector, thereby achieving the core principles of a circular economy,
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as shown in Figure 21. Apart from denim, recycling cotton for different applications not only supports the sustainability of the textile industry by reducing the environmental impact of raw material production but also contributes to the advancement of circular economy.
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This is evidenced by the improved properties of materials incorporating recycled cotton and the broader systemic benefits of reducing resource consumption and wastage.182,183 For instance, the integration of recycled cotton in composite and nonwoven applications presents an opportunity to extend the life cycle of the material and enhance the sustainability of products. Natural Fiber Composite materials (NFCs), which can incorporate recycled cotton, offer advantages such as biodegradability and lower raw material costs while being lightweight and renewable.184,185 The use of recycled cotton in such composites can further improve the environmental profile of these materials, as indicated by LCA studies that consider the full range of impacts, from raw material extraction to end-of-life.
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Moreover, nonwoven applications of recycled cotton can lead to the development of new, sustainable products with a reduced environmental footprint compared with their virgin counterparts. Generally, cotton recycling offers significant environmental benefits by conserving resources and reducing waste. LCA is an essential tool for quantifying these benefits and guiding the improvement of recycling processes. The integration of recycled cotton into composite and nonwoven applications not only extends the utility of cotton fibers but also contributes to the development of sustainable materials with lower environmental impacts.159,186,187 The reviewed studies collectively underscore the positive environmental impact of incorporating recycled cotton into textile manufacturing, and the importance of LCA in guiding and validating these sustainable practices.169,171,188–190 The developed recycling technology within the sustainability system
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Integration of recycled cotton in wearable, biobased composite and non-woven
The global population is anticipated to reach 8.2 billion by the year 2025, exhibiting an annual growth rate of 1%. Currently, approximately 50% of the population resides in urban areas or is in the process of urban migration. Furthermore, the ongoing industrialization in developing nations is expected to contribute to an increase in both energy consumption and waste generation.
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This suggests that the textile industry is projected to produce a growing volume of waste, with annual waste generation anticipated to increase by 70% from 2016 levels, reaching 3.40 billion tons by 2050.
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Therefore, the integration of recycled cotton into wearable, composite, and non-woven bio-based materials is a subject of considerable interest in the field of sustainable materials research. Recycling textile waste for bio-based materials is crucial.
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Therefore, the utilization of recycled cotton waste fibers in the production of wearable materials is a significant step towards sustainability in the textile industry. Research has demonstrated various applications of these materials, contributing to the circular economy and reducing the environmental impact.194–202 Both academic and industrial initiatives have focused on integrating cellulosic fibers derived from textile waste into materials like thermoplastics, thermosets, and concrete. These applications include sound-absorbing building components, electronics, packaging, furniture, and automotive parts.
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For example, the study leveraged the distinctive characteristics of cotton fabrics such as their expansive, adaptable surface, lightweight nature, and flexibility to develop flexible composite strain sensors for monitoring muscle contractions, as illustrated in Figure 22.
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The pattern of ∆R/R0 of vacuum bagging cotton fiber composites (VB-CF) during finger bending shows increased resistance, with peaks at the bent finger and troughs at the flat finger, as shown in Figure 22(ai). This suggests that the sensing composites can monitor finger-bending motion and muscle contraction. Figure 22(aii) illustrates the relative resistance changes associated with the contraction of the dizzy biceps during a third-class lever movement. When the forearm is flat, the dizzy biceps relax, resulting in a ∆R/R0 of 7.5 at the wave trough. However, the ∆R/R0 curves for finger bending and muscle contraction exhibit varying amplitudes and shapes, indicating that sensing composites can effectively differentiate between different body movements.
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A research study created a sound-absorbing material using waste cotton knit, waste polyester yarn, and natural rubber, demonstrating comparable sound insulation properties to commercial panels and increasing insulation properties with panel thickness.
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Another study found that recycled cotton fibers could be shredded and mixed with partially bio-based polyethylene terephthalate (Bio-PET) using a twin-screw extruder.
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The results indicated that incorporating 1-10 wt.% cotton waste into bio-PET enhanced stiffness and rigidity but decreased ductility and toughness due to poor interfacial adhesion. Additionally, cotton waste served as a nucleating agent for the crystallization of bio-PET, improving thermal resistance. The overall dimensional stability of the samples varied with fiber content, with bio-PET samples containing 3-5 wt.% cotton waste exhibiting balanced properties, making them suitable for rigid food packaging applications, as demonstrated in Figure 22(b). Sakthivel et al.
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explored the use of recycled polypropylene (PP) combined with recycled cotton (RC) and recycled polyester (RP) to produce nonwoven composites. This study sought to enhance manufacturing techniques and assess the physical and mechanical properties of air-laid and melt-bonded nonwoven composites designed for use as construction materials in housing systems. Sakthivel et al.
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explored the use of reclaimed cotton and polyester fibers in the production of nonwoven composites with sound absorption capabilities, finding that specific blend ratios yielded outstanding sound absorption performance. Araújo et al.
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investigated the hydrolysis of cotton fibers derived from textile waste to produce micro- and nanofibers for polymer composites. The study concluded that cotton waste can be effectively recycled as a filler in polymer-based composites when suitable surface modification strategies are applied. The research utilized various forms of textile waste, including woven fabrics, very short fibers, and particles and nanosized materials for composite reinforcement. However, Mohl et al.
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investigated the development of textile semi-finished products using medium-to-long cotton and flax fibers from textile waste combined with a bio-based thermoplastic matrix. They produced natural fiber-polylactide hybrid yarns, which were then consolidated into bio-based composites, as shown in Figure 22(c). This study examined the textile and mechanical properties of biocomposites hybrid yarns, considering factors like fiber length, distribution, structure, and volume content. The results indicate that bio-based semi-finished products may serve as a viable solution for upcycling textile waste. Todor et al.
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discussed the potential of textile waste fiber-reinforced polymer matrix composites, including those with cotton fibers, for various industrial applications due to their moldability and toughness. Contradictions or interesting facts emerge when considering different approaches to integrate recycled cotton.212–214 Sakthivel et al. emphasized the combination of recycled cotton with synthetic materials such as PP, while
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determined on the acoustic behaviors of nonwoven composites made from reclaimed cotton and polyester. Todor et al.
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expanded the scope by considering the use of cotton fibers in hybrid sandwich structure composites, potentially combined with other fibers like carbon or glass. Therefore, this research indicated that recycled cotton can be effectively integrated into composite and non-woven bio-based materials, offering sustainable alternatives for various applications. These studies demonstrated the potential for optimizing physical and mechanical properties through manufacturing techniques and material blends. These findings support the broader movement towards sustainable materials in industries such as construction, automotive, and textiles, aligning with environmental norms and market demands for eco-friendly products.212–214 (a) Tracking the patterns of (i) finger bending and (ii) dizzy biceps contraction during third-class lever movements using VB-CF [174]. (b) Creation of a sustainable and cost-effective partially bio-based PRT by utilizing cotton textile waste.
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(c) Hybrid yarns made from waste cotton (above) and waste flax (below)
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Method of integrating recycled cotton waste into wearable and biobased materials
The integration of recycled cotton waste into composite and non-woven products is a complex process that involves the reclamation of cotton fibers from post-consumer or post-industrial waste and their subsequent transformation into new materials. Mechanical recycling is a prevalent method for recycling cotton waste, where the fibers are shredded, potentially reducing their length and quality, which may limit their application.
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However, innovative strategies have been developed to overcome these limitations and add value to recycled cotton fibers by incorporating them into composites for sustainable construction and geotechnical applications
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as well as into non-woven materials for insulation purposes.
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Interestingly, research has indicated that the quality of recycled cotton can vary, with some studies noting a higher percentage of fabrics containing recycled cotton compared to those with original cotton.
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Additionally, the color of waste textiles poses a challenge in recycling, with some processes focusing on decolorizing fibers to facilitate their reuse.
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Despite these challenges, the development of composite materials using waste textiles and biodegradable components, such as starch, has been explored, resulting in environmentally friendly materials suitable for furniture design.
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The integration of recycled cotton into non-woven products is particularly relevant for applications such as thermal and acoustic insulation, where the properties of cotton fibers are advantageous.
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The process typically involves the mechanical carding of cotton fibers to form a web, which is then bonded using various techniques to create non-woven fabrics. Another study used recycled cotton fibers sourced from apparel cutting waste to develop high-performance thermal barrier fabrics.
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These fabrics exhibited consistent thickness and undistorted fiber surfaces, thanks to the optimized recycling process of cotton waste, as illustrated in Figure 23(a).
These materials can be used directly in insulation products (non-woven or composites), thereby contributing to energy savings and reducing environmental pollution.
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Similarly, Shoaib et al.
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created recycled cotton nonwoven panels as multifunctional porous sustainable materials, as shown in Figure 23(b). A study
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developed new hybrid composites using waste cotton textiles, a carded web of cotton fibers laminated with unidirectional glass fiber preform, and needle-punched jute nonwoven fabric, as indicated in Figure 23(c). Another study
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created high-value-added composite panels using textile and packaging waste from two sectors. These panels offer alternative thermal and acoustic materials, allowing 100% recycled insulation production, which is a unique method for creating composite insulation panels. Cotton fibers from waste denim fabrics have also been used as reinforcement materials.
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Therefore, the integration of recycled cotton after the reclamation of cotton fibers from post-consumer or post-industrial into composites and nonwoven fabrics involves the selection of appropriate fiber blends, bonding techniques, and manufacturing processes to achieve the desired material properties.
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Moreover, woven and nonwoven laminated fabrics for sound absorption applications highlight the versatility of recycled cotton in enhancing the properties of multilayered composites.
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Research has also shown that recycled cotton can be combined with other waste fibers and reinforced with high-performance materials such as carbon or glass fibers to create hybrid sandwich structure composites that are moldable, lightweight, and tough, offering a range of industrial applications.
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In applications for acoustic insulation, nonwoven fabrics with sound absorption capabilities have been created using recycled cotton and polyester fibers. This was achieved through methods including thermal bonding, chemical bonding, and thermochemical hybrid bonding.
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Additionally, the study on shirting fabrics woven with threads from recycled cotton blends underscores the importance of quality control in the production of recycled cotton-based textiles.
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Apart from bio-based materials (non-woven and composites), the concept that “nothing is wasted until we know how to use it” is exemplified by the preparation of sustainable clothing and accessories for different wearable applications.
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Various wearable fabrics by using felt loom nonwoven, woven, quilted, and loop-tufted from end-of-use cotton garments and other textile materials, as illustrated in Figure 24 were also developed.
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(a) Production process for felt-loom nonwoven fabrics. (b) Weaving methods: (a) Macomber floor loom; (b) frame loom. (c) Loop tufting technique: (a) loop pile tufting machine; (b) tufting method. (d) Confetti quilting procedure: (a) small fabric scraps layered on a base fabric; (b) confetti quilting process using a base fabric; (c) confetti quilting process without a base fabric
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Moreover, research on greige-cotton-containing nonwoven fabrics has shown that combines greige cotton lint with man-made fibers could achieve desirable whiteness and absorbency, offering an environmentally friendly option for wearable products. 231 However, the use of cotton fibers in nonwoven fabrics for single-use applications such as hygiene products is increasing because of the demand for natural, sustainable, and biodegradable materials. 232 The correlation between cotton fiber quality and nonwoven textile performance for fluid handling and moisture management in personal hygiene applications also demonstrates the potential of utilizing lower-grade cotton fibers in nonwoven textiles. 233 The recycling and manufacturing design of waste protective products made of high-strength PET fibers into hybrid-fabric fibrous planks showcases the integration of recycled cotton into high-performance materials. 234 The biodegradability of nonwoven fabrics containing cotton and synthetic fibers such as polypropylene have been compared, with findings indicating that natural fibers such as cotton are more susceptible to biodeterioration, making them a preferable choice for disposable goods. 235 In general, recycled cotton materials can be effectively integrated into bio-based and wearable materials through various processes, including blending with other fibers, employing different bonding techniques, and optimizing manufacturing methods. Studies have shown that recycled cotton enhances the creation of materials with improved mechanical, acoustic, and moisture management characteristics, which can be customized for various applications. This approach promotes sustainability and provides alternative uses for cotton waste, aligning with both environmental and economic objectives.169,213,214,236–241
Applications of recycled cotton waste for wearable products
The applications of recycled cotton waste fibers in wearable materials are diverse and have been the subject of extensive research. Recycled cotton fibers, often derived from pre- and post-consumer textile waste, are increasingly utilized in the textile industry to create sustainable clothing and accessories. These fibers are typically obtained through the chemical or mechanical shredding of textile waste and can be blended with other fibers to produce yarns and fabrics suitable for wearables.
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Interestingly, while recycled cotton fibers are generally considered to have lower quality values, research has shown that they can be effectively used in the production of coarse yarns for denim, towels, and home furnishings, as well as medium-count yarns for knit-top garments, such as T-shirts and polo shirts, as shown in Figure 25.
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The fabrics produced, as illustrated in the figure, feature a mélange-like look and have a soft, comfortable texture. This research specifically concentrated on creating soft (low-twist) yarns from both pre-consumer and post-consumer recycled fibers through ring spinning, making them suitable for top-knit garments. Additionally, high-performance thermal barrier fabrics have been developed from recycled cotton fiber, demonstrating enhanced functional properties, such as a high softness index, low rigidity, and improved thermal resistance, without compromising breathability or moisture management.
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However, it is important to note that the inclusion of recycled cotton can affect the physical properties of the resulting fabrics. For instance, fabrics containing recycled cotton showed a decrease in air permeability and effective clothing insulation but an increase in thermal resistance.
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Moreover, the presence of recycled cotton fibers in woven fabrics can lead to a higher percentage of surface defects and second-quality products than in fabrics made with original cotton fibers.
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Despite these challenges, the use of recycled cotton fibers in wearable materials is a cost-effective and environmentally sustainable option. Garments produced from recycled fibers have been found to be cheaper than those made from virgin materials, offering economic benefits to manufacturers and consumers while addressing waste management and disposal issues.
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Sample knit fabrics were created using 30 Ne ring yarns that incorporated: (a) 10% pre-consumer recycled cotton, (b) 25% pre-consumer recycled cotton, and (c) 10% pre-consumer recycled cotton
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Research has demonstrated various applications of these materials, contributing to the circular economy and reducing the environmental impact.216,221,242–248 The studies examined different ways to use recycled cotton and found that post-consumer cotton waste can be turned into new products like bags, clothes, and phone cases. This helps reduce waste and promotes more sustainable use of cotton, as shown in Figure 26.
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(a) Prototypes for cell phone cases: (a) confetti quilt cell phone case, (b) felt loom fabric cell phone case, and (c) glasses case. (b) Prototypes for bags: (a) handbag, (b) backpack, (c) makeup bag, and (d) and (e) tote bags. (c) Hat prototype: (a) side view and (b) back view. (d) Jacket made from felt cotton fabric: (a) front view and (b) back view. (e) Jacket crafted from tufted cotton fabric and a repurposed denim jacket: (a) jacket with tufted textile and (b) close-up of the tufted textile
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Recycled cotton fibers have also been compared with standard cotton fibers, with a focus on abrasion resistance, suggesting the viability of recycled cotton as a sustainable alternative. 249 Research has also shown that utilizing waste fabric from the cutting department in garment production can lead to cost-effective and eco-friendly apparel, with recycled fibers yielding garments with reasonable physical characteristics. 244 For instance, Ukrainian fashion brands have been analyzed for their sustainable manufacturing practices, including the use of recycled materials for clothing and accessories. However, these materials are often sourced from abroad owing to technological limitations. 250 Denim-cut waste has also been recycled into yarn and fabric for apparel manufacturing, exemplifying a sustainable and effective recycling method to produce wearable materials. 251 For instance, a researcher examined the impact of recycled cotton on denim fabric strength and performance. 252 The researcher discovered that although recycled cotton denim fabric’s tear strength was slightly lower, it still met all industry standards. This suggests that recycled cotton is a viable option for denim production. Additionally, a study comparing recycled denim waste to traditional pocket fabric showed no significant difference in strength. This indicates that recycled denim can be used as pocket material without compromising quality. 253 In general, the reviewed research indicates that recycled cotton waste fibers can be effectively applied to the production of wearable materials, offering sustainable alternatives to virgin cotton. These applications range from high-value products to everyday garments with the potential for significant environmental and economic benefits. The studies collectively underscore the importance of innovation and consumer awareness in promoting the use of recycled cotton in the textile and apparel industries.216,221,242–248
Applications for recycled cotton waste biobased composites
Natural fibers are increasingly being used as reinforcements in composites because of their light weight, low cost, reasonable specific strength, energy-efficient production, and environmental benefits. When combined with traditional plastics, they offer superior performance at lower prices, making them a potential replacement for competing materials in various applications, particularly in the automobile industry.254,255 Even small weight savings can significantly contribute to energy savings, reduced gasoline consumption, and eco-friendliness.256,257 These environmentally safe composites can be promoted by using natural waste fibers as reinforcements. Therefore, recycled cotton waste fibers have been increasingly utilized in composite materials for various applications, addressing both environmental concerns and the need for sustainable materials, as shown in Figure 27. Researchers have attempted to create composites from polymers reinforced with waste cotton and paper, and recently, natural fiber-reinforced polymer composites have gained increasing interest owing to increasing environmental pollution and stricter environmental policies.
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Research work outlined the process of converting thermoplastics from waste into fibers for use in composites, including concrete and technical textiles, highlighting the versatility of recycled fibers in industrial products.
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Further research emphasized the sustainability aspect by using recycled cotton fibers as reinforcement in composites, which were subsequently applied as insulation panels and construction materials and
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respectively. These studies demonstrate the potential of recycled cotton fibers for enhancing the physical and thermal properties of composites. While research focused on carbon fiber recycling, they also mentioned the use of recycled fibers in medium-to-high-performance composites, suggesting a broader applicability of recycled fibers beyond low-performance applications. The study presented a novel method for converting short cotton fibers into a renewable cellulose fiber self-reinforcing composite paper, showcasing substantial strength and versatility for various applications, including smart packaging.
Research also discussed the sustainability and mechanical advantages of using recycled fibers in composites,188–200,261 with specifically exploring the use of silk and cotton waste fibers in polymeric materials. Another study presented the use of waste cotton fibers as fillers in polylactide composites to enhance their mechanical properties. 262 Therefore, the utilization of recycled cotton waste fibers in composite materials is an innovative approach to address environmental concerns, while providing functional materials for various applications. In the automobile industry, these fibers can be used as reinforcement materials in composites, potentially reducing the weight of the components and improving fuel efficiency. For construction, recycled cotton fibers have been explored as insulation panels because of their thermal properties and as nonwoven composites for building materials, offering eco-friendly alternatives to traditional construction materials.197–202 In agriculture, cotton waste fibers have been combined with other biomasses, such as pineapple leaf fibers, to create aerogel composites with excellent thermal insulation properties, which can be used to maintain temperature regulation in agricultural facilities. Sports applications may benefit from the mechanical strength and flexibility of these composites, which could be used in equipment or protective gears. Packaging applications are particularly promising, as demonstrated by the development of a renewable cellulose fiber self-reinforcing composite paper (CCP) that exhibits high tensile strength and water resistance and is suitable for intelligent packaging solutions. 85 While CCP developed from cotton waste fibers shows potential for broad application prospects owing to its strength and recyclability, it also highlights the challenge of finding mature utilization methods for short cotton fibers. 199 Additionally, the combination of cotton waste with other materials, such as polyethylene, can lead to sustainable solutions that address the increasing waste from both the textile and packaging sectors.200–202 Generally, recycled cotton waste fibers are incorporated into composite materials for a range of applications across various industries, offering sustainable and functional alternatives to traditional materials. These composites contribute to cleaner production, resource conservation, and waste reduction, aligning with global sustainability goals. Research in this area is ongoing, with the potential for expanded applications and improved material properties as technology advances.
Recycled cotton biocomposites in automotive industry
The global automobile market’s growing demand and the need for sustainability have led to a growing demand for natural fiber-based materials for automotives. The researcher discussed the fabrication of small automobile components using natural fibers, including textile waste (cotton waste), as shown in Figure 28. These composite materials can be recycled regularly to reduce textile waste and promote sustainable transportation.197–205 Furthermore, biocomposites are transforming the composite sector for the automotive industry by promoting a circular economy from fiber extraction to final disposal, as indicated in Figure 28(a). This approach is safer and more environmentally friendly than synthetic and plastic materials.
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This indicates that recycling and working in this area in the automotive industry can improve the economic cycle and reduce environmental pollution. Additionally, the incorporation of textile and cotton fabric solid waste materials can contribute to a zero-waste environment,
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as shown in Figure 28(b). In addition to their biodegradability, natural fibers (recycled cotton) offer superior sound absorption owing to their porous structure, making them increasingly popular in automotive composites (Figure 28(c) and (d)).
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(a) Different automotive components and parts can be fabricated directly from natural fiber composite materials.208,209 (b) Life cycle of biodegradable natural fiber-reinforced composites.
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(c) Recycling cotton fiber waste.
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(d) The different garment and cotton fabric wastes are released into landfill
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Owing to its advantages and properties, the utilization of recycled cotton waste fibers in composite materials for automotive applications is an emerging area of interest, and numerous researchers have contributed their work in this area by adopting the concept of other fibers. Meng et al.
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highlighted the potential for recycled carbon fiber components to achieve lower life cycle environmental impacts in automotive applications, suggesting that similar benefits could be realized with recycled cotton fibers when used in composites. Research emphasized the automotive sector’s focus on lightweight materials to meet CO2 emission limits, indicating that fiber-reinforced composites, potentially including those with recycled cotton, could contribute to this goal.
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But there are challenges related to the use of recycled fibers including milled fibers, which could include cotton, are often relegated to low-value applications owing to performance concerns after the reclamation process.
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This necessitates rigorous testing and qualification to ensure confidence in their performance. Additionally, researchers have used the blending of waste cotton with virgin cotton and other fibers to mitigate the performance issue of recycled cotton fiber composites for automotive applications. Researchers also discussed the use of recycled cotton fibers blended with virgin cotton in the textile sector, which could inform similar blending strategies in automotive composites to achieve desired properties.
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Another research work also highlighted the use of recycled e-glass/cotton reinforced with epoxy resin composite felt in the automotive industry, emphasizing the positive effect of natural fibers on improving the flammability behavior of fabrics, which is crucial for safety in automotive applications.
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The use of waste cotton fibers as a filler for polylactide (PLA) composites, noting improvements in thermal and mechanical properties, albeit with a slight reduction in thermal stability further supported by other research work. In contrast, study pointed out that although the reuse of construction and demolition waste in composites has been studied, the specific application of recycled cotton from such sources in automotive composites has not been thoroughly examined.
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It also cautions that recycled materials can result in lower mechanical properties than virgin materials and highlights the need for careful consideration of potential contamination. Another research discussed mechanical and physical property improvements in composites using silk and cotton fibers, suggesting their potential use in automotive parts to achieve lighter vehicles and reduce environmental impact. Another researcher also provided insights into the recycling process of textile waste and the advantages of natural fibers, including cotton, as reinforcing materials in composites, which align with the automotive industry’s goals for lightweight and eco-friendly materials.213,247 Further reinforced the suitability of composite materials with recycled cotton for automotive applications,
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discussing the classification of composites in automotive parts and presenting mechanical testing of hybrid bio-composites, including cotton, for potential automotive use. In general, the literature suggests that recycled cotton waste fibers have significant potential for use in automotive composites, offering benefits such as improved flammability, mechanical properties, and environmental sustainability. Another work also outlined the benefits of implementing waste recycling in four main organizations: cotton producers, textile industry, garment factories, waste recyclers, and automotive industry as shown in Figure 29.
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This approach promotes a circular economy, pollution-free environment, and zero-waste production system, ultimately fostering a cleaner environment. However, challenges such as potential contamination and weaker mechanical properties compared to those of virgin materials must be addressed. Further research into the practicality and economics of production, as well as comprehensive mechanical testing, is necessary to fully realize the potential of recycled cotton fiber composites in automotive applications. Recycling and circular economy diagram of textile, automotive, and cotton planters
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Recycled cotton waste biocomposite materials in construction industry
The clothing and textile industries have significant environmental impacts and consume substantial raw materials.
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To tackle these challenges, there is a need for sustainable solutions that balance environmental, economic, and performance factors. Potential applications include eco-friendly thermal and acoustic insulation, innovative concrete, asphalt concrete, and composite materials manufacturing, which could help reduce waste in the rapidly expanding textile sector.
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Processing cotton waste fibers for reinforcement offers notable environmental and economic advantages, especially in construction applications.
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In concrete, waste cotton fibers serve as reinforcements without pozzolanic properties, enhancing composite volume more than weight and improving resistance to flexural and compressive stress.
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For example, incorporating 1% gamma-irradiated cotton fibers from discarded blue jeans into polyester concrete boosts flexural strain by 40% and flexural strength by 7%.
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Research indicates that mixing cotton with polyester enhances their mechanical properties
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and combining cotton waste with limestone powder waste and concrete can yield lightweight bricks.
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Textile waste, including fabrics and fibers, is also integrated into modern construction. Fiber-based composites emerging as viable alternatives to traditional building materials in residential construction.
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Recent studies have investigated hybrids that use textile fibers as reinforcements, resulting in lighter composites made from fabric scraps, epoxy resin, and foundry gravel. While textile fibers do not significantly improve the bending and compressive strengths of polymeric materials, they can mitigate brittleness.
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The use of recycled cotton waste fibers in construction composites is gaining interest due to its environmental and economic benefits. One study examined hybrid composites reinforced with cotton fibers from waste textiles, revealing significant improvements in mechanical properties when combined with glass and jute fibers. These thermally stable composites have the potential to replace timber in various construction applications.
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Additionally, research emphasizes the importance of waste utilization in sustainable composites, noting that the properties of waste materials and their intended use within the composite matrix are critical for successful structural applications.
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However, challenges remain, such as variability in the physical and mechanical properties of waste cotton fibers, which can impact composite performance.
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Figure 30 illustrates the sustainable properties of cotton fiber composites, showcasing their effective applications. Research has indicated that using waste cotton in construction can enhance bending and compressive properties. Studies have developed composite materials from cotton waste for building insulation, improving compressive strength, stiffness, and durability while enhancing energy absorption and flexural stiffness.
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Another investigation into fly ash-based geopolymer reinforcement with cotton fiber found that increasing cotton fiber content enhanced porosity and flexural strength, attributed to good adhesion within matrix.
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Recycled cotton waste has also been used as a filler in reinforced structures, expanding its application in geopolymer reinforcements. Research has explored recycled cotton fibers as reinforcement in composites with recycled polyethylene and polypropylene matrices, indicating their potential for sustainable insulation panels and nonwoven composites in housing systems. Furthermore, studies have developed bio-composites from cotton carpel, kenaf, flax, cotton stalks, and southern yellow pine, showing improved mechanical properties compared to unblended composites. The strength of these bio-composites is influenced by the physical and mechanical properties of the cotton fibers, fiber orientation, and composite composition.
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Effective sustainable composite properties for construction applications
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The acoustic, thermal, and physical properties of composites made from waste cotton and pigeon pea stalk fibers were also studied (Figure 31(a) and (b)) and the result reveals high sound absorption coefficients and insulation properties, which are desirable characteristics for construction materials (Figure 31(d)).
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The acoustic absorption values for the waste cotton and pea stalk-blended samples indicate that the sound absorption coefficient increases with frequency across all samples (S1C, S2P, S3C/P, S4C/P, S5C/P, and S6C/P). Examination of the waste composite samples after tensile testing revealed that fiber pull-out was significant in blends containing 6% fiber with a length of 4 mm. In contrast, composites with 20% fiber content and a length of 14 mm demonstrated the best matrix/fiber adhesion quality, as illustrated in Figure 31(c). (a) Pigeon pea and cotton fibers; (b) Composite material comprising cotton and pigeon pea fibers; (c) Scanning Electron Microscope (SEM) images: (i) Composites of cotton fibers and (ii) Composites of pigeon pea fibers; (d) Sound absorption performance metrics for the following samples: Cotton (S1C 100%), Pigeon pea stalk (S2P 100%), Cotton/pigeon pea stalk composite (S3C/P 50/50), Cotton/pigeon pea stalk composite (S4C/P 70/30), Cotton/pigeon pea stalk composite (S5C/P 60/40), and Cotton/pigeon pea stalk composite (S6C/P 30/70)
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A study highlighted the significance of recycling waste fibers for cement-based composites (CBCs), which can improve the mechanical behaviors and durability of construction materials with minimum environmental impacts. Additionally, Do et al. developed cellulose-based aerogel composites from pineapple leaf (PF) and cotton waste fibers (CF), which demonstrated high mechanical strength and low thermal conductivity, that lead them to be suitable for building thermal insulation. The PF/CF aerogel composites exhibited excellent thermal conductivity, ranging from 0.039 to 0.043 W m−1 K-1, as shown in Figure 32, indicating their effectiveness as thermal insulators. As the total fiber content increased, thermal conductivity rose from 0.041 to 0.043 W m−1 K-1 (Figure 32(a)). However, variations in the fiber ratio did not significantly influence the thermal conductivity due to minimal changes in porosity (Figure 32(b)). Similarly, Piekarska et al. investigated the use of waste cotton fibers as fillers in polylactide (PLA) composites, which showed enhanced thermal and mechanical properties, indicating their potential for construction applications. Recycling pineapple leaf and cotton waste fibers into thermally insulating and flexible cellulose aerogel composites. Analysis of thermal conductivity in cellulose aerogel composites as a function of increasing fiber concentration (a) and varying fiber ratios (b)
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Taşdemır et al. investigated fiber-reinforced composite structures against their mechanical and thermal properties, made form waste silk and cotton fibers for improved construction. This research conclusion indicated that recycled cotton waste fibers can be effectively utilized in various composite materials for construction applications. These composites offer enhanced mechanical and thermal properties, sound and moisture insulation, and sustainability. The integration of such materials into the construction industry could contribute to more environmentally friendly practices and efficient waste management.206–209,223
Recycled cotton fiber biocomposite in agriculture and furniture
The use of recycled cotton waste fibers in composites is gaining traction, especially for applications in agriculture and furniture. These composites bring sustainable replacement to traditional materials by leveraging the inherent properties of cotton waste to increase the performance and environmental footprint of the resulting products.123,169–172 Wang and his colleagues developed a method to turn short cotton fibers into a strong, eco-friendly paper material. This new paper could be used for many different purposes, including colorful papers and smart packaging. 265 This CCP demonstrates significant strength and water resistance, suggesting its utility in agricultural applications, where durability and resistance to moisture are crucial. Piekarska et al. didn’t directly address agricultural applications, but they did highlight the potential of waste cotton fibers as fillers for polylactide (PLA) composites, which could be extrapolated to agricultural uses such as biodegradable plant pots or mulch films. The improved thermal and mechanical properties of these composites indicate their suitability for such applications. Sakthivel et al. 212 further explored the use of recycled cotton and polyester fibers reinforced with recycled polypropylene (PP) for nonwoven composites, which could be utilized as construction materials for housing systems, potentially including agricultural structures. Some researchers also discussed the development of composites using waste cotton and other agricultural residues, such as pigeon pea stalks, for applications that require sound absorption, thermal insulation, and moisture resistance. 227 These properties are beneficial for agricultural applications, such as in controlled environment agriculture or storage facilities. On the contrary, other studies did not directly focus on agricultural applications provided insights into the mechanical and physical properties of waste cotton fiber composites, which could inform their use in agricultural contexts, such as in the development of responsive materials for sensing applications. In turn, this research indicates that recycled cotton waste fibers can be effectively utilized in composites for various agricultural applications. These applications range from packaging and mulching materials to construction elements for agricultural buildings and responsive materials for agricultural technologies. These studies collectively demonstrate the potential of these materials to contribute to sustainability in agriculture by repurposing textile waste and enhancing the performance of agricultural products. 236
In the context of furniture applications, Dhir highlighted the advantages of natural fiber composites (NFCs), including cotton fibers, for use in various industries, including furniture. NFCs are appreciated for their mechanical and physical properties, which make them suitable for molded materials that require moderate strength. Kucukali-Ozturk et al.
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discussed the use of recycled cotton fibers and polyethylene in composites designed for sustainable insulation panels, which could be applied in furniture or building applications, providing thermal and physical benefits. Baccouch et al.
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focused on enhancing the fiber-matrix interface in cotton-waste-reinforced composite panels, which could be used in furniture construction, as shown in Figure 33(a). Chemical treatment of cotton fibers significantly improved the mechanical properties of the composites, highlighting their suitability for furniture applications. In a similar vein, Bodur et al.
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found that alkaline treatment of waste cotton fabric enhances the mechanical properties of low-density polyethylene composites. The optimal treatment conditions were identified as 1 M concentration and a soaking time of 5 h, leading to notable increases in tensile strength and Young’s modulus. This improvement is attributed to the roughened surface of the treated cotton fibers, as shown in Figure 33(b). These properties make the waste cotton fiber composite better suited for outdoor applications, especially in the agricultural sector. However, the mechanical properties deteriorated with increasing soaking time and concentration. In summary, the incorporation of recycled cotton waste fibers into composites presents a promising avenue for the development of sustainable materials in the agricultural and furniture sectors. These composites capitalize on the advantageous properties of cotton waste, such as biodegradability and mechanical strength, to create products that are both environmentally friendly and functionally superior. Research in this field supports the broader objectives of cleaner production and resource efficiency, contributing to the achievement of Sustainable Development Goals123,169. (a) Depictions of (a) recycled cotton fibers, (b) cotton nonwoven fabric, and (c) cotton/epoxy composite.
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(b) Surface morphology of cotton fibers prior to (a and b) and subsequent to (c and d) alkaline treatment. (a) Untreated fiber surface at 20,000 × magnification; (b) untreated fiber surface at 5000 × magnification; (c) treated fiber surface at 20,000 × magnification; (d) treated fiber surface at 5000 × magnification)
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Recycled cotton waste biocomposite materials in the sport industry
Utilization of recycled cotton fibers in composites for sports applications is an emerging area of interest as it corresponds with the sustainability and resource efficiency principles. While the provided papers do not explicitly discuss the application of such composites in sports, they offer insights into the properties and potential uses of recycled cotton fiber composites that could be relevant to the sports industry. Recycled cotton fibers have been shown to enhance the mechanical properties of various composites. For example, the incorporation of cotton waste fibers into polyethylene matrices has been shown to improve the elongation characteristics of the resulting composites. This suggests that such materials could be beneficial in sports applications where flexibility and impact resistance are important, such as in protective gears or flexible components of sports equipment. The enhancement of the engineering properties of concrete through the incorporation of recycled textiles could be extrapolated to sports infrastructure, where improved durability and energy absorption are desirable features on surfaces such as running tracks or courts. Additionally, the thermal insulation properties of cotton-waste fiber composites can be explored for sportswear or outdoor sports equipment. 180 Sezgin et al. 181 developed high-value composite materials by integrating textile and packaging waste from two different sectors. They tested the acoustic insulation properties of the composite panels, finding that the sound absorption analysis revealed the composites acted like porous materials, with improved performance across the frequency range. In summary, while the direct application of recycled cotton waste fiber composites in sports has not been extensively covered in the literature, the properties of these materials suggest potential benefits for sports applications. The improved mechanical properties, such as enhanced elongation, tensile strength, and durability, indicate that recycled cotton fiber composites can be used in the development of sports equipment and infrastructure that are both environmentally friendly and performance-oriented. 265 Further research and development are needed to tailor these materials for specific sporting applications and fully understand their performance in such contexts.
Recycled cotton waste biocomposite materials in packaging industry
Innovative waste management strategies are spread in the technology and engineering sectors to bring environmental sustainability, particularly through waste engineering and effective technological solutions to address cotton waste issues. The bioeconomy concept has revolutionized the sustainable processing of cotton waste into bioproducts for packaging applications. Leal et al.
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proposed that circular design can significantly minimize the use of additives and chemicals when recycling cotton waste for packaging materials. Reichert et al. explored the potential of utilizing cellulose from biobased materials for bio-packaging applications, emphasizing the opportunities for creating a bioeconomy through the processing of cotton waste for sustainable packaging. They highlighted the promising prospects of circular design in bio-packaging, as illustrated Figure 34. Additionally, bio-cellulose composites derived from cellulose offer a promising structural solution for sheet coating and binders, owing to their high degree of polymerization, modulus, and tensile strength, making them suitable for bio-composite production.
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Reddy
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suggested that polymer composites made of cotton could be combined with fillers and additives and then reprocessed into various forms. Ramamoorthy et al.
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suggested that cotton waste can be combined with feather fibers to create handspun yarns for packaging purposes. Montava-Jordà and colleagues
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discovered that cotton fibers measuring between 10 and 30 μm in diameter and having a long, thin shape improved the strength and durability of a polymer composite material used for non-food packaging. This enhanced composite exhibited high tensile strength and desirable mechanical properties, making it well-suited for its intended purpose. Schematic representation of bio-derived materials for packaging applications includes the following materials: PEF (polyethylene furanoate), PLA (polylactic acid), PBS (polybutylene succinate), and PHA (polyhydroxyalkanoate)
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Specifically, Wang et al.
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presented a novel approach for creating a renewable cellulose fiber self-reinforcing composite paper (CCP) from short cotton fibers, which demonstrates superior tensile strength and water resistance compared with commercial A4 paper. This CCP, with its potential for a wide range of applications, including colored and intelligent packaging papers, exemplifies the innovative use of cotton waste in packaging materials, as shown in Figure 35.
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In contrast, while Wang et al.
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focused on the creation of paper-like composites, other studies have explored the use of cotton waste fibers in combination with thermoplastics. Some researchers discussed the reinforcement of polyethylene with recycled cotton fibers to produce sustainable composite materials that are potentially applicable in packaging owing to their improved physical and thermal properties.
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Similarly, others investigated the use of recycled cotton and polyester fibers in polypropylene composites, which could be tailored for packaging applications owing to their enhanced mechanical characteristics.
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Do et al.
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introduced an innovative cellulose-based aerogel composite using cotton waste fibers, which exhibited excellent thermal insulation properties and mechanical strength, making it suitable for packaging applications that require thermal management. A sustainable strategy to convert cotton waste into renewable cellulose fiber self-reinforcing composite paper, promoting eco-friendly material use and minimizing waste
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Furthermore, Srivastava et al.
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discussed the development of biodegradable packaging films using lignocellulosic biomass, which includes cotton waste, in combination with biodegradable polymers, such as polyvinyl alcohol, highlighting the role of cotton waste in reducing plastic pollution. Jamshaid et al. investigated the creation of knitted hollow composites using recycled cotton fibers (RCF) and glass fibers (GF). These composites are suitable for packaging heavy-weight products across various industries, including aerospace, marine, automotive, civil infrastructure, medical prosthetics, and sports equipment, as illustrated in Figure 36. The flexural strength of RCF-reinforced hollow composites surpassed that of double-layered cardboard packaging material, highlighting their enhanced stiffness. The impact energy absorption of GF and RCF composites, as well as cardboard material, was also assessed. GF-reinforced composites consistently exhibited higher impact energy absorption than RCF-based samples. Furthermore, specimens with thicker tube walls, regardless of reinforcing fiber type, demonstrated improved impact energy absorption. The utilization of recycled fiber represents a significant stride towards environmentally friendly materials and waste reduction. Their performance, when compared to commercial packaging materials, suggests potential applications as replacements, contributing to a reduction in environmental burdens. Therefore, this research indicates that recycled cotton waste fibers can be effectively utilized in various composite materials for packaging applications. These composites not only help in managing textile waste but also contribute to the development of sustainable packaging solutions.
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These studies demonstrate the flexibility of cotton waste as a reinforcement material, which can improve the mechanical properties, thermal insulation, and environmental sustainability of packaging products. Mechanical properties of knitted hollow composites made from recycled cotton and glass fibers for packaging purposes
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The applications of recycled cotton waste in biobased non-woven materials
Nonwoven materials made from recycled fibers, including cotton, are gaining attention owing to their environmental benefits and cost-effectiveness.
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Recycled cotton fibers are used in nonwoven textiles for sound absorption, and studies have shown that recycled PET/cotton waste made nonwoven mats can absorb sound resistance of more than 70%.
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Additionally, nonwoven fabrics developed from recycled cotton and acrylic-blended fibers exhibit desirable properties, such as abrasion resistance, water penetration resistance, and air permeability, making them suitable for various applications.
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Interestingly, while recycling textile waste into nonwoven fabrics contributes to resource conservation and addresses environmental concerns,
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it also enables the creation of high-value products. For example, recycled high-strength PET fibers have been used to produce hybrid-fabric fibrous planks with good mechanical properties and stab resistance. Moreover, the use of lower-grade cotton fibers, which are typically discounted in the market, has been found to be advantageous for nonwoven textiles in applications requiring moisture management, such as personal hygiene products.
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This research also extends to the quality control of fabrics woven with recycled cotton fibers, ensuring that the end products meet the necessary standards.
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Furthermore, nonwoven fabrics made from waste fibers have been successfully incorporated into cladding panels, improving their thermal conductivity and bending strength.
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Innovative applications have also emerged, such as the development of colorimetric sensors using plasma-induced coloring of nonwoven recycled cotton for the detection of harmful substances, such as ammonia.240–246 This indicates that nonwoven fabrics made from recycled cotton offer a range of desirable properties, such as absorbency, comfort, insulation, and durability, which are beneficial for diverse applications, as shown in Figure 37.
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In the automobile industry, nonwoven fabrics can be used for interior components such as seat covers, headliners, and insulation materials. The breathability and thermal resistance of cotton-based nonwovens contribute to passenger comfort and vehicle insulation. Nonwoven textiles are indispensable for medical and hygienic products because of their disposability, sanitation value, and cost-effectiveness. They are used in surgical products, wound dressings, and disinfectant wipes, where the absorbency and softness of cotton are crucial.
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In sports, nonwoven materials with recycled cotton are used in apparel and equipment, offering moisture management and comfort during physical activity. Packaging applications benefit from the development of nonwoven fabrics that incorporate recycled polyester and other fibers to enhance mechanical properties while maintaining the light weight and chemical resistance required for packaging materials.
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It is important to note that while recycled cotton fibers are advantageous, the quality control of fabrics containing recycled fibers is critical because defects can affect the performance and aesthetics of the final product.243,244 These nonwoven fabrics should offer a balance of performance, comfort, and environmental benefits, making them suitable for use in the automobile, medical, hygienic, sports, and packaging industries.241,245,246
Automobile applications
Nonwoven fabrics, which are engineered fabrics created by mechanical, thermal, or chemical bonding or interlocking fibers, are increasingly being considered for use in the automotive industry owing to their versatility and cost-effectiveness.185–212,261 However, there are challenges associated with the use of recycled cotton fibers in nonwoven materials, particularly in terms of maintaining the quality and performance of end products. Mechanical recycling methods, such as shredding, can shorten the fiber length and reduce the fiber quality, which may limit the application of recycled textiles in demanding environments such as those found in automobiles.
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Despite these challenges, research has shown that nonwoven fabrics made from recycled cotton and other fibers possess desirable properties such as abrasion resistance, thermal resistance, and air permeability, which are important for automotive applications.236–244 For instance, loop-bonded nonwoven fabrics created from recycled cotton and acrylic-blended fibers have shown desirable properties, such as abrasion resistance and water penetration resistance, which are beneficial for automotive applications where durability and resistance to elements are crucial.245,246 Nonwoven materials made from recycled cotton fibers can be used for interior components, such as car seat covers, headliners, and insulation materials. These components benefit from the natural properties of cotton, such as breathability and absorbency, while also contributing to sustainability goals by reducing waste and consumption of virgin materials.
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Additionally, the incorporation of recycled cotton fibers into nonwoven composites has been shown to improve sound absorption, which is a critical factor for acoustic comfort in vehicle interiors.
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The research examined the acoustic properties of nonwoven fibrous materials created from coffee husk and cotton waste, revealing that sound absorption is influenced by both the thickness of the materials and the ratio of coffee husk to cotton fibers. The study also showed that these materials were most effective at absorbing low-frequency noise, which is more harmful to human health than high-frequency noise (Figure 38). These advancements support the industry’s move towards greater sustainability without compromising performance or comfort.
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Various stages for the preparation of sustainable sound absorption nonwoven materials
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Moreover, in cotton weaving, false self-edge formation results in waste in weft and warp yarns.249–251 The extra weft yarn can account for 9%–10% of the waste, with the extra yarn length accounting for 7–9 cm on each side. Interestingly, researchers have analyzed the economic benefits and key technologies for overcoming weaving waste selvage, finding that efficient and reasonable use of bio-based materials offers better economic and environmental benefits.249–251 Fera et al.
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created stitch-bonded non-woven samples by recycling woven fabric selvage waste, as shown in Figure 39. The air permeability of the developed sample decreased its sound absorption performance. The test results highlight the importance of the sound absorption properties of sound-absorbing materials for automotive applications.
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Conversion of the cotton selvage to stitch-bonded non-woven production and sound absorption performance of non-woven samples (increasing thickness from samples #1 to #8)
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Medical and hygienic applications
Biopolymers, such as cotton, are utilized in biomedical packaging, antimicrobial materials, biosensing, and tissue engineering applications; cotton is a prime example of a natural fiber with over 95% cellulose content.250,251 Therefore, the utilization of recycled cotton waste fibers as nonwoven materials for medical applications is an area of growing interest. Nonwoven fabrics are increasingly used in medical settings because of their cost-effectiveness and functional properties such as disposability, absorbency, and barrier protection. 252 Interestingly, although nonwoven materials are advantageous for medical applications, the incorporation of recycled cotton fibers enhances these benefits. Recycled cotton, derived from garment waste or other textile by-products, offers a sustainable alternative to virgin cotton, reducing the environmental impacts associated with cotton cultivation and processing. 253 Moreover, the inherent properties of cotton, such as breathability, softness, and high absorbency, are preserved during the recycling process, making it suitable for medical textiles. 254 However, maintaining the performance standards required for medical applications is a challenge. Research shows that nonwoven fabrics made from recycled cotton can meet industry demands. For example, loop-bonded nonwoven fabrics combining recycled cotton and acrylic fibers demonstrate excellent durability, comfort, and moisture management, making them suitable for medical textiles. 255 Additionally, the abrasion resistance and water repellency of these fabrics can be optimized, which is crucial for protective medical garments. 256 Moreover, nonwovens made from recycled cotton fibers offer a sustainable alternative to traditional materials, aligning with the increasing demand for environmentally friendly and biodegradable products. 238 These nonwoven materials are suitable for single-use medical products, such as hygiene items, wipes, and other disposables because of their natural properties, including absorbency and comfort. 238 However, the mechanical recycling of cotton can lead to a reduction in fiber length and quality, which may limit the application of recycled textiles in certain contexts. 216 Despite this, the development of nonwoven fabrics from recycled cotton has been shown to possess desirable properties, such as adequate moisture resistance, which is crucial for medical applications, without compromising insulation and acoustic properties. Furthermore, research has explored the link between cotton fiber classification and the physical and functional characteristics of nonwoven fabrics. This suggests that fibers can be selectively sourced based on quality for specific applications, which could improve the performance of medical nonwoven fabrics. 238 However, further study can lead to the wider adoption of recycled cotton nonwovens in healthcare, contributing to both environmental conservation and the advancement of medical textiles. 214 Additionally, nonwoven fabrics made from recycled cotton and other fibers exhibit beneficial properties, including excellent absorbency, low electrostatic charge, comfort, disposability, and sanitation value, making them ideal for hygienic applications. 263 These fabrics can be designed for faster drying, enhanced durability, and a luxurious soft feel, making them ideal for hygiene applications. However, there are challenges associated with the use of recycled cotton, such as a reduction in fiber quality, which may limit the application of the resulting textiles. 216 Despite these challenges, research has demonstrated that non-woven materials made from recycled cotton can be designed with specific properties such as thermal resistance, air permeability, and moisture vapor transmission, which are beneficial for hygienic applications.216,236 Additionally, recycling cotton-based non-woven fabrics are being explored for their potential use in various hygienic products such as diapers, wipes, and medical textiles.237,238,258 These materials are valued for their absorbency, softness, and disposability, which are critical for hygiene applications. The research has demonstrated that even lower-quality cotton fibers, often sold at discounted prices, can be effectively used in nonwoven applications, enhancing moisture management and fluid handling performance. 237 This suggests that the non-woven fabric industry could provide an alternative market for these fibers, which are less suitable for conventional textile manufacturing.
Packaging applications
Nonwoven fabrics composed of recycled cotton and polyester fibers can be utilized in various forms, including filling fibers and recycled yarn, making them suitable for packaging applications. 239 These non-woven fabrics can be engineered to possess desirable properties, such as uniform thickness, softness, and low rigidity, which are beneficial for protective packaging materials. However, there are challenges associated with the recycling of cotton waste, as the process can shorten the fiber length and reduce the fiber quality, potentially limiting the application of the resulting textiles. 216 Despite these challenges, research has shown that nonwoven preforms made from a combination of polypropylene and cotton can exhibit satisfactory mechanical and thermal behavior, making them suitable for use in composite materials that could be applied in packaging. 216 In the context of sustainability, the incorporation of textile waste nonwoven fabric as reinforcement in cement-based matrices has demonstrated improved toughness and stress-bearing capacity, indicating its potential for use in nonstructural packaging applications. Moreover, the selection of appropriate cotton waste, such as loosely knitted greige cotton fabrics, can lead to better quality recycled fibers and, consequently, higher-quality non-woven materials for packaging. 167 Rodrigues et al. 255 studied the use of small cotton pieces for the production of wet-laid nonwoven fabrics. These pieces were shrunk to obtain recycled fibers, which were then refined using a process. The results showed that replacing bleached eucalyptus kraft pulp (BEKP) with 70% cotton waste fibers in wet-laid nonwovens reduced the use of virgin raw materials and improved the mechanical properties of the structures by 80% and 14%, respectively. The study also found that refining small cotton pieces was more promising than refining recycled fibers because fewer steps were required. This approach can be explored for various products and end applications, such as lampshades and flower packaging. Moreover, several studies have demonstrated that recycled cotton and polyester fibers can be effectively used to create non-woven mats with desirable properties, such as sound absorption, moisture resistance, and thermal insulation. These are achieved through various blending ratios and bonding methods, with a focus on maintaining the performance under high humidity conditions.242,253 In addition, this research highlights the importance of physical properties, such as density, thickness, porosity, and air permeability, for packaging applications. These characteristics are crucial for packaging materials that require a balance between protection and breathability. Moreover, the creation of loop-bonded nonwoven fabrics from a blend of recycled cotton and acrylic fibers demonstrates potential for applications that demand abrasion resistance, water penetration resistance, and air permeability. 182 However, further research is needed to tailor these non-woven materials to specific packaging requirements and to evaluate their performance in packaging applications.
Challenges and opportunities
The cotton fiber recycling processes face several technical challenges, trends, and issues that impact the move towards sustainable practices. One of the primary challenges is the difficulty in collecting and classifying waste materials, which is exacerbated by the presence of contaminants, such as blends and chemicals. 254 This led to the large-scale textile industry posing a significant challenge to effective waste management and recycling. 255 Mechanical and chemical recycling processes are essential, yet they come with their own set of obstacles, including the high cost of recovery procedures and technical difficulties in separating fiber blends. 256 Despite these challenges, positive trends and initiatives were observed. For instance, Brazil has shown progress in industrial sustainability and has adopted global production trends in textile recycling. 258 Moreover, the concept of circular economy is gaining traction, emphasizing the need for commercially viable recycling processes for low-grade materials and the development of advanced recycling technologies. To address logistical and technical hurdles, it is essential to advance eco-friendly methods and innovative recycling technologies. 259 Government initiatives, along with public awareness and skill development, can aid in promoting sustainable practices. 266 Insights gained from future research in cotton fiber recycling can further enhance environmentally responsible methods. Recycled cotton from industrial and consumer waste is gaining traction in creating composite and nonwoven materials due to its adaptability, lightweight characteristics, and durability. 214 These materials are not only eco-friendly but also offer economic viability through cost-effective production processes and potential for market growth, as evidenced by the projected expansion of the green composite market. 253 However, the use of recycled cotton as a bio-based material is challenging. Although the environmental benefits are clear, with reduced ecological footprints and support for green ecosystems, 255 the economic viability of these materials can be influenced by factors such as the availability of recycled cotton and the cost of processing. Additionally, the integration of recycled cotton into high-value applications requires careful consideration of the material’s performance characteristics and compatibility with other fibers. 256 Interestingly, hybrid reinforcement systems that incorporate both natural fibers and nanoparticles can significantly enhance the functional applications of recycled cotton in bio-based materials. The integration of natural fibers, such as cotton, with other natural fibers can lead to the development of hybrid composites with improved mechanical properties and environmental benefits. 257 The addition of nanoparticles to these composites has been shown to positively influence the overall strength and performance of materials. 258 Although natural fibers (cotton) offer advantages such as biodegradability and cost-effectiveness, they also present challenges such as lower strength and durability compared to synthetic fibers. However, surface modification techniques and the addition of nanoparticles have been explored to improve the physicochemical properties and stability of natural fibers.259,266 Moreover, the use of bio-based resins in combination with natural fiber reinforcements can lead to the creation of composites that are not only strong but also environmentally friendly.260,267 In general, the development of hybrid reinforcement systems that combine recycled cotton with other natural fibers and nanoparticles hold promise for advancing the functionality of bio-based materials. These hybrid composites can potentially offer a balance between performance and sustainability, making them suitable for a wide range of applications in various industries. Research indicates that through chemical treatments and the incorporation of nanoparticles, the properties of natural fiber composites can be significantly enhanced, leading to materials that are both highly performing and environmentally responsible. 268 However, the literature presents a different view of the regulatory and policy landscape impacting recycling practices, including those for cotton-fiber-based materials. There are supportive regulations and policies aimed at promoting recycling. For instance, Taiwan’s government has implemented a comprehensive regulatory system to encourage industrial waste recycling and offers financial incentives and technical assistance. 269 Similarly, the United States has federal regulations such as the Resource Conservation and Recovery Act (RCRA) to manage waste, although variability exists across states. 270 However, there are significant obstacles to effective recycling. These include the lack of comprehensive local government-level regulations in China, 271 the absence of effective policy implementation and enforcement, as seen in urban Kenya, 262 and barriers identified in the Chinese WEEE recycling industry, such as the need for optimized legislation and improved collection efficiency. 272 Interestingly, although some regions have developed targeted programs to address waste management, such as the “Zero Waste North Lombok” initiative, they often face barriers such as inadequate policies, lack of stakeholder cooperation, and insufficient financial support.265,273 Therefore, while there are supportive policies and regulations aimed at promoting recycling practices, including those for cotton-fiber-based materials, there are also numerous obstacles that hinder their effectiveness. These range from inadequate policy implementation and enforcement to financial and technical barriers. Addressing these challenges requires concerted efforts from governments, industry stakeholders, and communities to create a more conducive environment for recycling practices to thrive.
Conclusion
This comprehensive review underscores the growing significance of cotton waste recycling as a cornerstone of sustainable material science, yielding substantial environmental and economic advantages. By examining diverse mechanical, chemical, plasma, and microwave-assisted recycling technologies, the review highlights their capacity to convert waste into valuable resources, often maintaining or enhancing fiber quality. The fabrication of bio-based nonwovens and composites from recycled cotton, utilizing techniques like needle punching and various molding processes, presents promising avenues for creating high-performance, sustainable materials across numerous industries, contributing to a circular economy. The environmental benefits, including reduced landfill use and resource conservation, are significant, emphasizing the need for a holistic life cycle assessment to ensure alignment with broader sustainability goals. Despite the considerable potential and versatility of recycled cotton in sectors ranging from automotive to packaging, the review acknowledges existing challenges in processing, maintaining fiber quality, and ensuring economic viability. These obstacles, however, also represent opportunities for innovation in developing more efficient recycling technologies and expanding market applications. Ultimately, cotton waste recycling is a critical research area addressing sustainability and resource efficiency, with continued advancements poised to overcome current limitations and fully realize the potential of recycled cotton, thereby fostering a more sustainable and circular economy.
Footnotes
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