In recent years, there has been a growing concern about environmental issues and high energy consumption. Ensuring the sustainability of energy resources and the environment has become one of the significant challenges of our time (Islam and Bhat, 2019). From an environmental perspective, the rapid growth in the global population, coupled with its escalating consumption rates and the growing tendency to dispose of materials in landfills as waste prematurely, poses significant obstacles to sustainability (Bergstrom and Randall, 2016).

Textile waste has a significant impact on the environment and public health, as millions of tons of clothes are produced and disposed of every year, causing a large accumulation of waste in landfills, with very negative consequences (Islam and Bhat, 2019; European Parliament, 2023). Waste management is important to minimize the consequences on the environment. The best strategies for reducing waste start with avoiding, reducing and reusing. At the end of the products’ life cycle, there are several approaches that can be followed: recycling, incineration, biodegradation and landfill (Muthu, 2020).

Circular economy aims to reduce excessive waste, promoting its use as a ‘raw material’ for the manufacture of new products. This allows economic growth to be decoupled from the negative consequences of resource depletion and environmental degradation (Neves and Marques, 2022).

The recovery and attribution of new applications to textile waste is currently possible through several reprocessing technologies, enabling its reuse within the textile industry or its utilization in emerging sectors such as construction, non-woven production industries, furniture and paper industries, automotive and agriculture (Bhatia et al., 2014).

This review article aims to delve into the multifaceted implications associated with textile waste, alongside a rigorous examination of the underlying principles governing the circular economy framework. The comprehensive elucidation of textile waste valorization constitutes a focal point of this analysis, wherein a meticulous exposition will be provided, elucidating numerous examples that highlight the transformation of waste into innovative materials. These new materials are mainly used for thermal and acoustic insulation and structural reinforcing. Incorporating thermal insulation in buildings plays a vital role in reducing energy consumption by minimizing temperature changes (Al-Homoud, 2005; Islam and Bhat, 2019). Sound insulation is also important to reduce the harmful effects of noise to which the population is constantly exposed (Islam and Bhat, 2019).

Every year, millions of tons of clothing and footwear are produced and discarded, according to the European Environment Agency, between 2000 and 2020 textile production almost doubled, from 58 million tons to 109 million tons. An increase up to 145 million tons is expected by 2030 (Islam and Bhat, 2019; European Parliament, 2023). In Europe, every year, each citizen uses about 26 kilos of textiles and discards about 11 kilos, with most of the used clothes (87%) being incinerated or landfilled (European Parliament, 2023). In the US only about 12% of clothing waste is recovered (Ütebay et al., 2019). It is estimated that every year more than 92 million tons of textile waste are produced (Niinimäki et al., 2020; Centobelli et al., 2022).

“Fast fashion” is the main culprit for this trend, because it is a business model based on offering consumers frequent novelty in the form of low-priced, trend-led product (Islam and Bhat, 2019; Muthu, 2020; Niinimäki et al., 2020). This concept probably explains the increase of clothes consumed per capita by 47% between 2000 and 2015 (Peters et al., 2021). These companies are characterized by the rapid ability to design, manufacture and distribute clothing, which allows them to respond quickly to changing trends and bring new styles to the market within weeks. This fact, alongside the low-prices associated, leads consumers to shop more frequently in order to stay up to date with the latest fashion trends (Islam and Bhat, 2019; Niinimäki et al., 2020; Bailey et al., 2022). These products are available at low prices, which is why companies often adopt measures to reduce production costs, such as using cheaper raw materials and producing in countries with lower labour costs (Bailey et al., 2022). Due to the low cost and rapid turnover of these products, consumers tend to understand fashion as disposable, buying clothes for the short term and quickly disposing of them (Islam and Bhat, 2019; Niinimäki et al., 2020). For example, some clothes are projected to be used only 10 times (McNeill and Moore, 2015). While fast fashion has gained popularity for its affordability and quick response to trends, it has also been criticized for its environmental and ethical impacts. The industry’s emphasis on low-cost production can contribute to environmental degradation, exploitation of labour in developing countries, and the generation of large amounts of textile waste (Islam and Bhat, 2019; Niinimäki et al., 2020; Bailey et al., 2022). In recent years, there has been a growing awareness and movement towards sustainable and ethical fashion practices as consumers seek alternatives to the fast fashion model (Centobelli et al., 2022).

Textile industry is the second most polluting and waste-generating sector in the world, accounting for 10% of total atmospheric carbon emissions (which corresponds to 1.7 billion tonnes of emissions) (Ütebay et al., 2019; Niinimäki et al., 2020; Baccouch et al., 2022; Centobelli et al., 2022) and 20% of global wastewater (79 billion l) annually (Islam and Bhat, 2019; Niinimäki et al., 2020; Centobelli et al., 2022; European Parliament, 2023). Furthermore, chemical treatments and dyes used in the manufacturing process are responsible for 35% of ocean pollution by microplastics (Niinimäki et al., 2020). In 2020, to produce clothes for each EU citizen around 9 m³ of water, 400 m² of land and 391 kg of raw materials were required. For each citizen, around 270 kg of carbon was emitted, meaning that textile products consumed in the EU generated 121 million tons of greenhouse gases (European Parliament, 2023). CO₂ emissions are expected to increase to nearly 2.8 billion tons until 2030 (Islam and Bhat, 2019).

The environmental impact of production varies according to the types of fibers, synthetic or natural. In Figure 1, the values of fiber production, water consumption, energy consumption and carbon dioxide emission for polyester, cotton, non-cotton cellulosic, polyamide, wool and helm are represented (Niinimäki et al., 2020). Polyester is the most used fiber in industries, representing a production of 54 million tons of fibers (Islam and Bhat, 2019; Niinimäki et al., 2020). In relation to the freshwater consumption, cotton has the highest, accounting for 1559l per kg of fiber. In textile industry, energy consumption and CO₂ emissions are more increased during the initial fiber extraction, mainly synthetic fibers because they are from fossil fuels. To produce polyamide, 160 kWh are used per kg of fiber. One way to reduce CO₂ emissions associated with fiber production is to replace synthetic fibers with natural fibers (e.g., wool and hemp). Wool and hemp have low carbon emissions of 17.0 and 3.1, respectively. Natural fibers (cotton, non-cotton cellulosics, wool and hemp) require less energy, but during their production they require significantly more water than synthetic fibers (polyester and polyamide).

When textile waste decomposes, several gases are released into the atmosphere, namely, methane. This powerful gas contributes significantly to greenhouse gas emissions because it absorbs the sun’s heat that radiates on the Earth’s surface and retains it in the atmosphere. This leads to an increase of Earth’s temperature, which is called global warming (Islam and Bhat, 2019). Non-renewable petroleum-based materials release gases during their decomposition, making a very harmful contribution to air, water and soil pollution (Baccouch et al., 2022).

In addition to these problems, this industry has a devastating impact on the health of local populations, animals and ecosystems where the factories are located (European Parliament, 2023).

According to directive 2008/98/EC of 19 November 2008 of the European Union Waste Framework Directive, the best waste management strategy is to prevent the waste (European Parliament and Council, 2008). Waste management began with the concept of 3Rs: reducing, reusing and recycling (Neves and Marques, 2022). Over the years, these concepts have evolved into 10Rs, as will be presented in section 4 (Morseletto, 2020). Reduce and reuse are some of the practices that help decrease the amount of waste. At the end of the lifespan of textile materials, there are several destinations that they can follow: recycling, incineration, biodegradation and landfill (Figure 2). (Muthu, 2020)

Reducing the consumption of textile products is a good practice, because it minimizes the amount of waste generated and uses fewer resources to produce new products. A good practice to reduce textile consumption is to opt for high-quality items that are more expensive, but perform better and, therefore, will last longer and cause less waste (Abdul-Rahman, 2014). Reuse, as the name suggests, refers to various means of extending the practical useful life of textile products, with or without prior modification, by transferring them to new owners (Sandin and Peters, 2018; Muthu, 2020). This can take two forms: primary: reuse for the same purpose; - secondary: reuse for a purpose other than that originally intended. This process can be achieved in several ways, such as collecting goods by charities, selling them in second-hand stores, donating them to loved ones, etc. In many countries, it is common to see bins collecting second-hand clothes with the intention of being distributed to people in need (Muthu, 2020). An example is Gekas Ullared’s (retail store), where its customers can since 2012 leave clothes, fabrics and toys to be donated to Human Bridge (a charitable organization). Buying second-hand clothes has also been increasing in recent years (Ekström and Salomonson, 2014). For post-consumer textiles, in environmental terms, this is the best option because it delays the disposal of the product and prevents it from being deposited in landfill before the necessary time. Furthermore, it also minimizes the production of new textile products (Muthu, 2020). The companies Lindez and Myrorna give a discount coupon if customers deliver old clothes. The objective is to increase customer awareness on the importance of giving their clothes a second chance (Ekström and Salomonson, 2014; Filho et al., 2019). In Brazil, there is a Reuse Fabric Bank that aims to extend the lifespan of clothing, fabrics and post-consumer waste from industries, allowing them to return to circulation and avoiding sending them to landfills prematurely. If one deposits the parts directly in this bank, they receive credits for each kilogram which can later be used to obtain other materials from the bank. The most common users are artisans, fashion and design students, stylists, among others (Broega et al., 2017; Filho et al., 2019). The environmental impact of reusing textiles is 70 times lower than producing new clothes. A recent study shows that it is possible to save 3 kg of CO₂ for each garment reused and water use is only 0.01% of what it would be to produce a new garment (BIR, 2022). Another study demonstrated that by reusing pairs of trousers (made from 65% polyester/35% cotton) it is possible to reduce approximately 20% of natural gas and crude oil consumption, 25% of nutrient enrichment impact, 28% of acidification impact, 30% of soil toxicity and 45% of water toxicity during the production chain (Muthu, 2020).

Recycling refers to the destructuring of a discarded product after its use and subsequent processing of the resulting components for application in similar or different products. This approach is advantageous because it allows the use of resources (water and energy consumption) to be reduced, as virgin raw materials are replaced by these new materials, preventing the depletion of non-renewable resources. Recycling textile waste reduces carbon emissions in the life cycle of these products, thus reducing the greenhouse effect and, consequently, global warming and waste disposal in landfills is avoided/reduced (Muthu, 2020; Baccouch et al., 2022). Recycling can be divided into two categories: closed-loop: the recycled material returns to the same life cycle (raw material for the same product); - open-loop: the recycled material leaves its current life cycle and appears as a completely new product, with a new life cycle (Muthu, 2020; Baccouch et al., 2022). This process is generally downcycling so, in most cases, the quality of the recycled material is lower than the equivalent virgin material (Muthu, 2020). To improve the quality of the recycled product, for example, avoid mixing different fibers or using lower quality fibers, aiming for a product with a single fiber in its composition (Morley et al., 2009). Collection rates for potentially recyclable materials are still low. In Brazil, South Africa, Russia and China, collection rates are 12, 10, 11% and 20%, respectively. In more economically developed countries such as Canada, France and Italy, collection rates are 32% 40% and 43%, respectively (Filho et al., 2019). This is due to the existence of several obstacles to overcome in the recycling of textile waste (Filho et al., 2019; Muthu, 2020).Textile products are very complex, as they contain several types of materials such as metals, plastics, polymers, among others. Recycling is not always viable, due to the difficulty in separating these materials, given their different mechanical and technological properties (Marconi et al., 2018). The strength of textile fibers is also a challenge, because their strength complicates their crushing, which is necessary to convert the material back into raw material. Furthermore, there is also the presence of chemical materials and dyes that are toxic and carcinogenic, making the recycling process difficult. Consequently, this problem leads to the unavailability of recycled textile materials, due to insufficient quantities of suitable and accessible textile waste for recycling. One of the main reasons for the insufficient quantity of recyclable materials is the lack of technologies for sorting and separating textile waste for recycling. Existing technology also cannot separate dyes and other chemical contaminants from fibers. Automated sorting will improve the efficiency of the production process and increase the number of textiles suitable for recycling. In economic terms, the demand for recycled textiles is limited, because virgin raw materials have better quality and lower market prices. Recycled textile materials still have relatively high prices due to the high cost of recycling processes, plus transportation, which discourages potential investors. Economically, it is more attractive to use multiple textile fibers, as it makes the recycling process more accessible (Filho et al., 2019). The low recycling rate is also due to society’s low awareness of textile recycling. Currently, many countries prioritize the recycling of waste, such as glass, wood, paper, plastic and metal, while textile recycling is less prioritized and publicized (Anthouli et al., 2013).

Textile waste recycling has been thoroughly discussed in the literature. Dissanayake et al., conducted an extensive review on the topic and concluded that unblended cotton (50%) was the most frequently studied, followed by cotton and polyester blends (29%) (Dissanayake and Weerasinghe, 2021). The main method used for fabric waste managing was mechanical recycling, either by melt-extrusion (shredding, crushing, grinding, melting, and re-extruding into fibers, spun into yarns or directed towards non-wovens), or cutting, shredding and carding (construction and industrial sector applications) (Shen et al., 2010; El Wazna et al., 2017; Dissanayake et al., 2018; Peña-Pichardo et al., 2018). Chemical and biochemical strategies comprised 38% and 14% of the studies analyzed. Chemical methodologies follow one of two paths—either there’s depolymerization into the material’s monomer units, followed by repolymerization; or dissolution, where the waste’s constituents are separated, filtered and regenerated into fibers through the use of adequate solvents (Raj et al., 2009; Vadicherla and Saravanan, 2017). According to their findings, recycling follows mostly open-loop approaches (34%), with the construction and building sectors being the main contributors (Dissanayake and Weerasinghe, 2021).

A different approach for waste management is biodegradation, as it guarantees the effective disposal of a product and helps it complete its life cycle, without causing any impact on the environment. This process occurs through the chemical degradation of materials, which is aggravated by the action of microorganisms, namely, fungi, bacteria and algae (Leja and Lewandowicz, 2010; Muthu, 2020). The materials are converted into biomass, carbon dioxide and water. Biodegradation can be aerobic and anaerobic. If oxygen is present in the reaction medium, this is aerobic biodegradation and carbon dioxide is produced. Otherwise, it is anaerobic degradation (absence of oxygen) and methane is produced instead of carbon dioxide. The extent of biodegradation of materials depends on several factors such as ambient temperature, the amount of water available, the presence of microorganisms and chemical factors (for example, pH) (Muthu, 2020). Arshad et al. studied the degradation of fabrics (cotton, jute, hemp, linen, polyester and wool) for 3 months, under attack by microorganisms present in the soil, using two methods: in contact with the soil and in the absence of soil. When in contact with the soil, it was difficult to understand which fiber was most biodegradable because most of them are natural fibers, which are mainly made up of cellulose. In the absence of contact with the soil, jute and linen are the most biodegradable. Of the natural fibers, wool is the least biodegradable since its molecular structure and surface are very resistant, making it difficult for microorganisms to penetrate. As polyester is a synthetic material, microorganisms cannot degrade it, making it a non-biodegradable material (Arshad and Mujahid, 2011).

Textiles wastes consisting of a synthetic polymer alongside cellulose fractions pose danger to the environment and present potential towards biofuel production (Wojnowska-Baryła et al., 2022). Roughly 35%–40% of textile waste is constituted by cellulose, which can be harnessed to be used as a feedstock in the generation of products such as ethanol and biogas (Jeihanipour et al., 2010; Shen et al., 2013). Anaerobic biodegradation is often applied towards the production of biogas from textile waste (Juanga-Labayen et al., 2022), exploiting its biodegradable cotton content as a source for bioethanol biorefining and the production of biogas. (Wojnowska-Baryła et al., 2022). Examples of previous studies in which this textile waste management strategy was employed are summarized below, alongside processing conditions and main results (Table 1). Most methane-rich biogas textile sources for anaerobic digestion found consist of textile cotton wastes, mainly due to its high cellulose percentage (∼54%) (Raj et al., 2009). Studies have also described the possibility of producing methane from other textile related wastes through anaerobic digestion, such as sludges resultant from the textile dying process, posing an energetically and cost-effective alternative (Zhou et al., 2021).

In addition to biogas, bioethanol production using textile waste as a feedstock in fermentation has been investigated, although far fewer studies have been developed (Table 2). Pre-treatments are determining in this process, notably improving ethanol yields. Cellulose feedstocks are often pre-treated in order to increase surface area and enzyme accessibility, through alterations in porosity and crystallinity. Attempts have been made using chemical treatments (alkali, organo-solvents), joint physical and chemical treatments (hydrothermal, acid pretreatments assisted by microwaves) and synergic combinations (organo-solvents, trailed by hydrothermal treatment) (Wojnowska-Baryła et al., 2022).

Another approach to waste management is incineration. This involves burning waste under conditions and it has a negative impact on the environment and human health. Incineration can be carried out with or without energy recovery, with the former being preferably used, as, despite the negative impact, it also brings benefits (energy production). Incineration without energy recovery is not a desirable option (Muthu, 2020). Textile waste can be incinerated, but the incinerator often cannot accept large quantities because the long threads act as a fuse from incineration to waste storage. For this reason, industrial textiles are landfilled. However, this is decreasing with the addition of pre-treatments such as cutting and shredding (Palm, 2011).

The last and least desired option is to dispose of waste in landfills, which only generates negative effects on the environment and human health. In addition, problems such as space availability also arise, as in most countries current landfills are full (waste takes many years to decompose) and there is no more space to build new ones (Muthu, 2020). Only textile waste unsuitable for other waste management strategies can be disposed of in landfills (Rapsikevičienė et al., 2019). The Environmental Protection Agency revealed that in the United States, in 2015 around 12 million tons of clothing and footwear were discarded, of which more than 8 million tons ended up in landfills (Brewer, 2019). In Europe, only around 15%–20% of textile products are recycled. The 75%–80% was landfilled or incinerated (Sandin and Peters, 2018; Bailey et al., 2022).

Life cycle assessment is the process of evaluating or estimating the impact a product in its useful life has on the environment and human health, that is, from its production (including the extraction of raw materials) until elimination. For this estimate, emissions to air, water and soil are assessed during production, use and disposal of the product. After that, the assessed amount is related to possible environmental effects, including resource depletion, ozone depletion, global warming, among others (Asdrubali et al., 2015; Islam and Bhat, 2019).

In a linear economic system (Figure 3), raw materials are taken from the environment and converted into final products that will be disposed of at the end of their useful life. These products are often designed for a single purpose and have a short shelf life, leading to a large accumulation of waste (Sariatli, 2017; Neves and Marques, 2022). A traditional linear economy, without processes such as recycling, is not sustainable and, therefore, must be replaced by a circular system (Geisendorf and Pietrulla, 2018).

The circular economy (CE), often termed a “closed-loop economy”, prevents the generation of excessive waste by transforming it into valuable resources for producing new goods (Figure 3). This economy model extends the useful life of products and restores and regenerates them, guided by regenerative design (Geisendorf and Pietrulla, 2018). CE’s objective is to create a sustainable development, generating a method to create economic growth without depleting resources and degrading the environment (Jørgensen and Pedersen, 2018; Morseletto, 2020; Webster, 2021; Neves and Marques, 2022). It began with the concept of reducing, reusing and recycling (known as the 3Rs), essential for the waste management process (Section 3) (Neves and Marques, 2022) It has since extended to 10 Rs: “refuse, rethink, reduce, reuse, repair, refurbish, remanufacture, repurpose, recycle and recovery” (Table 3). Rethink is part of a strategy of smarter product use and/or manufacture and it can be applied before production starts (companies) or before acquiring the products (individuals). Rethink principle encourages individuals and businesses to reconsider their consumption patterns and make more mindful choices. On the individual’s point of view, it involves questioning and reevaluating the necessity of purchases, as well as assessing product’s environmental and social impacts (Morseletto, 2020). Companies should integrate environmental considerations into the design process, like ecodesign, since the product design phase plays a crucial role on environmental impacts (Delaney et al., 2022), as this phase can be responsible for 80% of products’ sustainability performance (Riesener et al., 2023). Ecodesign is part of the rethink strategy as an approach to designing products, processes, and systems, which during the design phase considers factors such as type and quantities of resource used, energy efficiency, waste reduction, and the overall ecological footprint (Kirchherr et al., 2023; Morseletto, 2023). This process is carried out to extend the final product’s life and turns these products’ recycling less complex. Besides all environmental concerns, ecodesign also considers social and ethical needs. By integrating environmental considerations into the design process, ecodesign aims to contribute to a more sustainable and ecologically responsible future (Riesener et al., 2023). In 2005, the European Commission wrote the first directive on ecodesign for energy-using products (European Parliament, 2005), nonetheless revoked by 2009/125/EC Framework Directive (EUROPEAN PARLIAMENT et al., 2009) which includes any good that could have an impact on energy consumption during its use know as energy related products. Recently, the EU proposed regulation on ecodesign, which established a framework for ecodesign requirements for sustainable products (EUROPEAN PARLIAMENT AND COUNCIL, 2022), the main instrument to guide product design phases and life cycles with continuous improvements (Bundgaard and Huulgaard, 2023). This regulation focused on two major aspects - the importance given to substances of concern, and the establishment of a digital product passport that may introduce changes on the perspective for the textile production, helping the transition to a non-toxic circular economy. Ecodesign means the integration of environmental sustainability considerations into the characteristics of a product and the processes taking place throughout the product’s value chain (EUROPEAN PARLIAMENT et al., 2009).

The combination of all these concepts defines an economic model that, in addition to minimizing the extraction of raw materials and natural sources, transforms end-of-life materials into a resource for new materials, closing cycles in industrial ecosystems and minimizing waste (Morseletto, 2020; Neves and Marques, 2022).

However, drawbacks, such as not enough investments to introduce the CE in the sector, no internationally recognized normative institutions to regulate the sector, insufficient and ineffective public opinion on the topic have been hindering its progress (Sariatli, 2017; Jørgensen and Pedersen, 2018).

The CE is therefore beneficial and fundamental to society, leading industries into a more efficient and environmentally friendly future (Sariatli, 2017; Jørgensen and Pedersen, 2018). The execution of CE within global economy is essential to ensure human life on planet Earth in the long term (Geisendorf and Pietrulla, 2018). So, a transition from the linear economy to the CE is essential and urgent. (Sariatli, 2017).

In respect to LCA studies on textiles, Chopra et al. (2023) compiled goals reoccurring in the literature, presented below with adaptations (Table 4). According to the authors, The Higg Index allows the benchmarking of textile life cycle impacts in the sector, systematically assessing the processes involved, regarding material/energy flows, and quantifying the environmental impacts associated with developing valorization methods. Their review showed that the life cycle production phase of textiles and its use phase are the most studied, in that order; however, analyses on the impact of the end-of-life stage is yet to be developed (Chopra et al., 2023).

Textile waste comes from various sources, such as household use and waste from production lines, both of which are increasing considerably. Based on sources, textile waste is classified as pre-consumer/post-industrial (PCPIW) and post-consumer waste (PCW). PCPIW refers to material discarded during the manufacturing process of textile materials (yarns, cuttings, mill ends, damaged goods, etc.), before it is used by the consumer. It is generated from natural and synthetic fibers production, spinning, weaving, knitting, dyeing, printing, finishing, designing, and cutting, wholesalers, trading companies, retailers and mass merchandise chains. Typically, PCPIW can be recovered and reused as raw material for the automotive, furniture, non-wovens and other industries. PCW refers to a product the consumer has used and that no longer serves a need, being subsequently disposed of. This waste can also be recovered and recycled, a practice that is only enacted in a low percentage of cases (Bhatia et al., 2014; Islam and Bhat, 2019; Rapsikevičienė et al., 2019; Patti et al., 2020).

Currently, resorting to several reprocessing technologies, it is already possible to recover fibers from textile waste and assign them a new application. High quality fibers can be obtained from PCPIW; however, if recovered at the end of the material’s life, they’ll present lower quality. The recovered fibers can be once again used in the textile industry or be given new applications, such as in the building, non-woven, furniture, carpet, agriculture and paper industries (Table 5). They can be spun into new yarns for the production of fabrics, knitting or non-woven fabrics, upholstery materials, biomaterial composites, insulation materials, among others (Bhatia et al., 2014).

In the literature, there are already several examples of new materials incorporating textile waste (cotton, polyester, EVA, leather, wool, etc.) such as, non-woven structures and composites, produced from PCPIW and PCW. In the sections below, several examples of both types of waste will be described, but mainly from PCPIW. Most of the new materials produced feature acoustic and/or thermal insulation capabilities. The use of efficient thermal insulation materials reduces energy consumption by minimizing heat losses and gains during the heating and cooling of the building (Al-Homoud, 2005). In domestic buildings, good thermal insulation can reduce energy consumption by around 65% (Hadded et al., 2016). Sound insulation is also key in reducing the harmful effects of noise that the population is constantly exposed to. The gradual increase in noise pollution is due to various factors such as urbanization, industrialization, increased use of vehicles, electrical and household and industrial mechanical appliances. Noise pollution is responsible for a number of negative health effects, encouraging the incorporation of insulation materials into buildings, cars, etc (Islam and Bhat, 2019)

This literature review introduces various innovative materials, including non-wovens and composites, which incorporate textile waste. These materials exhibit mechanical, thermal, and acoustic properties that rival or surpass those of conventionally employed materials in similar applications.

In general, there is a tendency for textile waste to be used as thermal/acoustic insulating materials. Regarding thermal properties, all non-woven (=0.012–0.049 W/mK) and composite (λ = 0.026–0.062 W/mK) structures presented have acceptable thermal conductivity values for application as thermal insulation materials. Within non-woven structures, it is worth highlighting the sample produced by Sakthivel et al. (Sakthivel et al., 2020), from polyester and recycled cotton, as they present the best thermal conductivity values (λ = 0.120–0.130 W/mK). Within the composites, the structure produced from recycled Kevlar showed the best thermal conductivity, 0.026 W/mK (Lin et al., 2016). In general, composites have higher thermal conductivity values ​​than non-woven structures. This happens because non-woven structures are more porous, that is, they have more air spaces inside, preventing air movement and loss through radiation (Song, 2009).

Regarding acoustic properties, the absorption coefficient values are between 0.100–1.000 and 0.000–1.000 for non-woven and composite structures, respectively. Within the non-woven structures, samples from (Drochytka et al., 2017; Fera et al., 2022), made from polyester and recycled cotton, show the best results, recording a maximum absorption coefficient of 0.990. For composite structures, the sample made with recycled wool from Rubino et al. presents the best absorption coefficient values, 0.700–1.000 (Rubino et al., 2021).

Other alternatives to using waste as insulation are beginning to be studied, such as, for example, the introduction into cement matrices, fertilizers, production of enzymes, etc. The use as fertilizers and in the production of enzymes is due to the fact that some types of textile waste are organic and biodegradable materials.

All the examples described in this review are in line with the concept of circular economy, as textile waste is transformed into new products with added value. This prevents the excessive generation of waste and its accumulation in landfills, which are harmful to the environment and public health. Furthermore, by incorporating these wastes into the production of new products, the need for virgin raw materials is also reduced. Despite the advantages that these new materials present, there are also some disadvantages, such as the use of glues and resins as binders, which are harmful. It is also necessary to carry out studies on the cost of producing materials on a large scale, as companies tend to buy the cheapest materials.

In the future, it is expected that companies will begin to adopt these sustainable practices and that manufacturing techniques for these new green materials will become increasingly accessible. Due to the growing interest of companies in environmental sustainability, the application of these materials is also expected to increase, particularly in civil and automotive industries. It is also expected that studies on the incorporation of textile waste in applications for agriculture and 3D printing filaments will increase.

These new materials contribute to cost-benefit, to the reduction of textile waste, to the reduction of the use of virgin raw materials, among others. In short, it is expected that these alternative materials will help minimize the carbon footprint and the harmful consequences that the planet has suffered.

In this review paper, an extensive overview on disposal and recovery of textile waste has been compiled. Millions of tons of clothing are produced and disposed of every year, causing immeasurable consequences to the environment and human health. For this reason, the concept of circular economy has emerged, according to which no excess waste is generated as it becomes a starting point for the production of new materials. There is not yet an innovative universal solution for textile waste management, but reduce, reuse and recycling practices have already positive and significantly impacted air, water and soil pollution. Recovered textile waste can be used to manufacture non-wovens, composites or cementitious matrices, new materials that can be employed as thermal and acoustic insulation, upholstery materials, biomaterial composites, among others. Based on these literature findings, recovery of textile waste and its use to produce new materials is essential. The low costs of new materials, the decrease in raw material extraction and the reduction of environmental impact justify the active implementation of the circular economy concept in this sector. It is urgent and essential to develop new materials from existing waste for the preservation of the environment and the continuation of human life on planet Earth. In the near future, there is an anticipation that research into opportunities for reclaiming textile waste will grow, marking the exponential growth of the implementation of these novel eco-friendly products.