Polyester fibres, integral to textiles and medical devices, contribute significantly to global carbon emissions, with over 60 million metric tons produced annually. These sustainability challenges are further compounded by the fact that over 80% of global textile waste is currently disposed of through incineration or landfill. We address this challenge by proposing a sustainable alternative: polyhydroxyalkanoates (PHAs), fossil-free polyesters synthesised by microorganisms. Our focus is on green wet spinning of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibres, utilising eco-friendly solvents.

Commercial-grade PHBV fibres, wet-spun from a 16 wt.% solution in 1,3-dioxolane into an ethanol coagulation bath, demonstrated an average diameter of 57 ± 12 µm (n=200). Additionally, we explore coffee waste as a sustainable carbon source for PHBV production, with comparable coffee oil yields using green solvents (2-methyltetrahydrofuran and dimethyl carbonate) compared to hexane (8 ± 1 wt.% vs 9 ± 1 wt.%). Coffee oil characteristics extracted using green solvents are similar to those extracted using hexane (e.g. Acid value: 7 ± 1 vs 6 ± 1 mg KOH/g, Saponification value: 177 ± 6 vs 184 ± 7 mg KOH/g).

Our findings showcase the feasibility of green solvents for PHBV fibre production and the potential of coffee waste-derived oil for bacterial fermentation. This sustainable approach not only addresses the environmental impact of polyester but also emphasises effective end-of-life degradation and upcycling.