Anaerobic co-digestion of textile waste with food waste could transform two problematic waste streams into renewable methane while reducing landfilling and incineration, according to a study published in Waste Disposal & Sustainable Energy. The research, conducted by scientists at the University of Auckland in New Zealand and James Cook University in Australia, examined mono- and co-digestion of cotton, polycotton, and wool with food waste under mesophilic conditions. The findings matter because textile waste is generated at enormous scale—about 92 million tonnes disposed of annually—yet landfilling, incineration, and recycling remain costly or environmentally problematic.
The study tested substrate-to-inoculum (S/I) ratios of 0.5 and 1 and multiple feedstock mixing ratios, tracking methane yield, biodegradability, process stability, and synergistic effects. Results showed that lower S/I ratios and higher food waste shares generally improved methane production, but performance depended strongly on textile type, carbon-to-nitrogen (C/N) balance, and the co-digestion performance index (C1). Among textiles, cotton performed best in mono-digestion, producing 103 mL/g volatile solids (VS) and reaching 25.87% biodegradability at an S/I ratio of 0.5. Co-digestion with food waste raised methane production further, with the highest yield—129.7 mL/g VS—from a cotton-to-wool ratio of 6:1, which had a balanced C/N ratio of 20.63. Synergy was strongest when food waste made up more than 80% of the blend, especially with cotton, where C1 exceeded 1.
Kinetic analysis using a modified Gompertz model showed that more food waste shortened lag phases and accelerated biogas production. For example, a 1:4 cotton-to-food-waste blend reached 111 mL/g VS and about 29% methane content, while a 1:1 wool-to-food-waste blend produced almost no methane due to ammonia inhibition. Polycotton and wool exhibited antagonistic effects (C1 < 1) because polyester resisted degradation and wool's keratin structure limited microbial access. Post-digestion analyses linked poor performance to residual volatile fatty acids, soluble chemical oxygen demand, and free ammonia nitrogen above inhibitory thresholds.
The authors said the findings offer a clear operating principle: co-digestion is most effective when food waste dominates the blend and the C/N ratio stays within the optimal window. Cotton-rich mixtures were especially promising, while polycotton and wool need pretreatment or fiber separation. They added that C1 provides a simple way to screen promising feedstock combinations before scaling up. For textile manufacturers, waste managers, and biogas operators, the study suggests that co-digesting textile waste with food waste can improve methane yields, stabilize digesters, and divert waste from landfill. The full study is published (DOI: 10.1007/s42768-026-00316-y) and was supported by open access funding enabled and organized by CAUL and its Member Institutions.
