# Opportunities and Limitations in Recycling Fossil Polymers from Textiles
### Microplastics Issue  
Despite 30% of Europeans' wardrobes not having been used for at least one year, it is reported that a single laundry load of polyester clothes can discharge 700,000 microplastic (MP) fibres, which can end up in the animal and human food chain [2, 3, 5]. Microplastics, in fact, that were detected in teacups, human placenta and blood [37, 38, 39], might be the cause of toxicity or other hazardous and poorly known effects [40]. Apparel is responsible for 35% of microplastics invading oceans each year, as part of textile fibres (0.5 million tonnes of microfibres per year). This high quantity of waste is due to the increased amount of waste apparel made of non-degradable synthetic fibres [41]. Figure 4: Global production capacities of bioplastics in 2022 [23]. Source: European Bioplastics, Nova-Institute (2022). More information: www.european-bioplastics.org/market and www.bio-based.eu/markets (accessed on 12 February 2023). Synthetic microfibres (MFs) are a ubiquitous class of MPs that pollute the marine and freshwater environments, thus raising an increasing global concern. These MFs mainly originate from textile industry discharges, textile releases in domestic and industrial effluents, illegal dumping and abandoned fishing gear [42; 43; 44; 45]. Textile MFs [46; 47] are the majority of MPs detected in the inflow and outflow of wastewater treatment plants. PET and PA (mainly nylon 6 and nylon 6.6) account for the majority of synthetic MFs produced worldwide at a ratio of approximately 10:1 [48]. Consequently, the largest fraction of synthetic MFs found in municipal sewage sludge are MFs in PET [49; 50; 51]. However, because the analytical protocols for quantifying MPs in environmental matrices commonly rely on the physical separation of MPs [52; 53], followed by their detection by optical microscopy and identification by FT-IR micro-spectroscopies [54] or Raman [55; 56], MFs in PAs often go undetected due to their similar spectroscopic characteristics to protein materials [57; 58]. Techniques combining thermal [59] or hydrolytic [60] decomposition of MPs coupled with mass spectrometry have been exploited to improve the accuracy of MP quantification. Most of the analytical protocols proposed so far involve time-consuming physical separation from the environmental matrix and particle counting, which often result in overestimation of the actual MP content due to natural fibres being mistaken for synthetic MFs, or underestimation due to a failure to separate or detect them due to their small size. While adequate accuracy and sensitivity have recently been achieved for PET through depolymerization, chromatographic separation and quantification of its monomers by HPLC and spectroscopy or mass spectroscopy [57], the quantification of MFs in PAs is still a challenge. Recently, the first procedure for an accurate and highly sensitive determination of total nylon 6 and nylon 6.6 content in complex environmental matrices, such as sediments, soils and sludge, was presented [61]. The salient features of the procedure include acid-catalysed hydrolytic depolymerisation followed by the attachment of a fluorescent tag to the obtained monomers and their quantitative determination by reversed-phase HPLC. This technique was adopted, together with one previously developed for PET [61], to develop a protocol for the analysis of PA and PET in sludge samples from sewage treatment plants. The actual hazard of MF depends on many factors, including the concentration and bioavailability of the fibres in the environment, their state of degradation and the way they are fed to and assimilated by consumers.