Environmental life cycle assessment of textile bio-recycling – valorizing cotton-polyester textile waste to pet fiber and glucose syrup

Emerging textile bio-recycling approaches can address the environmental challenges associated with the end-of-life of clothing. However, it is imperative to assess the environmental impacts associated with these technologies, systematically, to ensure they are environmentally sustainable. The objective of this study is to evaluate the environmental implications of a novel bio-recycling method that recovers polyester (PET) fibres and glucose, from 50/50 cotton/PET blend of fabric waste from H&M, using Life Cycle Assessment (LCA). The chosen functional unit is one kg of recovered PET fibre. Life Cycle Impact Assessment (LCIA) was conducted in terms of ReCiPe, both midpoint and endpoint indicators, and Cumulative Energy Demand (CED) impact categories. LCA results of the gate-to-cradle analysis indicate pre-treatment as the most dominant process, followed by melt-spinning and then enzymatic hydrolysis. Sensitivity analysis with Global Warming Potential (GWP) indicator shows that pre-treatment step influences the results and contributes to uncertainty. Pre-treatment (207 MJ) is also the most energy-intensive step, followed by melt-spinning (98.5 MJ) and enzymatic hydrolysis (44.8 MJ). We also describe linkages between addition of PET bottles in the melt-spinning step and environmental impacts. Environmental impacts on all three endpoints increased as the percentage of waste PET bottle chips added was decreased. LCA of the textile bio-recycling method suggests that environmental impacts can be further reduced, provided the involved unit processes are made more energy-efficient, and the fibre quality of the recovered polyester is improved such that it can be directly used for garment production without the need to add waste PET bottle chips.