Novel sustainable alternatives for the fashion industry: A method of chemically recycling waste textiles via acid hydrolysis

The fashion industry has a considerable environmental impact, especially due to the increased generation of waste textiles as a result of fast fashion business models. Although fiber-to-fiber recycling processes are being developed, such a process is in reality a downcycling process, in which the mechanical properties of the textile fibers are impoverished with each cycle. Thus, new alternatives are required to completely close the fashion loop through chemically recycling textile fibers unfit for other types of recycling or resale due to their poor quality. We have evaluated the possibility of using acid hydrolysis to directly depolymerize the cotton fibers in waste textiles to produce a glucose solution, which could subsequently be used for the production of chemicals or fuels. Although a one-step procedure with sulfuric acid was unable to deliver high glucose production, it was possible to achieve a glucose yield over 90% through a two-step procedure, in which concentrated and dilute sulfuric acid were combined to exploit the benefits of both concentrations. Glucose concentrations around 40 g/L were achieved by increasing the solids loading in the two-step process, which might be sufficiently high for the fermentation of the solution into high-value products. Thus, this study demonstrates that it would be possible to chemically recycle (cellulose-based) waste textiles via acid hydrolysis, which, if correctly designed, could avoid the need to use enzymes to achieve high conversion efficiencies.