Cascade enzymatic hydrolysis

In the textile recycling process, the third stream consists of a wide range of textile items and materials and has no value for reuse nor for repair and typically end up for incineration (or landfill, depending on the country). For the cotton and polyester-rich stream, cellulases will be used to break down cotton. Indeed, after an initial textile sorting and shredding process, the textile (PET-cotton-commingled) will be fed into a hydrolysis reactor, where the cotton is broken down to sugars with the help of specialized enzymes, e.g. cellulases or mixtures therefrom. For the polyester and other polymers-rich stream, we will break down polyester into MEG and PTA.

The PU coatings will already contain components, which helps the degradation of the coating, which will be realised by enzymatic treatment. Enzymatic breakdown of PU has been studied using esterases, like lipases and cutinases15. The PET would be degraded as well, but as these coatings are on the outside of the fibres, the process will be controlled via the enzyme selection and reaction time to keep PET intact.