Anaerobic co-digestion of textile waste with food waste could transform two problematic waste streams into renewable methane while reducing reliance on landfilling and incineration, according to a study published in Waste Disposal & Sustainable Energy. The research, conducted by scientists at the University of Auckland and James Cook University, examined how different textile types and mixing ratios affect methane production and process stability.
Textile waste is generated at enormous scale, with about 92 million tonnes disposed of annually. Landfilling, incineration, and recycling remain costly or environmentally problematic. Anaerobic digestion can convert organic-rich waste into biogas, but mono-digestion of textiles is limited by imbalanced carbon-to-nitrogen ratios, recalcitrant keratin in wool, and non-biodegradable polyester in blended fabrics. Food waste, being highly biodegradable and nutrient-rich, emerges as a promising co-substrate.
The study tested mono- and co-digestion of cotton, polycotton, and wool with food waste under mesophilic conditions, varying substrate-to-inoculum ratios and feedstock mixing ratios. Results showed that lower substrate-to-inoculum ratios and higher food waste shares generally improved methane production, but performance depended strongly on textile type, carbon-to-nitrogen balance, and the co-digestion performance index. Cotton performed best in mono-digestion, producing 103 mL/g volatile solids and reaching 25.87% biodegradability. Co-digestion with food waste raised methane production, with the highest yield of 129.7 mL/g volatile solids from a cotton-to-wool ratio of 6:1, which had a balanced carbon-to-nitrogen ratio of 20.63. Synergy was strongest when food waste made up more than 80% of the blend, especially with cotton. Kinetic analysis showed that more food waste shortened lag phases and accelerated biogas production.
However, polycotton and wool showed antagonistic effects. Polyester resisted degradation, while wool's keratin structure limited microbial access. A 1:1 wool-to-food waste blend produced almost no methane due to ammonia inhibition. Post-digestion analyses linked poor performance to residual volatile fatty acids and free ammonia nitrogen above inhibitory thresholds.
The authors conclude that co-digestion is most effective when food waste dominates the blend and the carbon-to-nitrogen ratio stays within the optimal window. Cotton-rich mixtures were especially promising, while polycotton and wool need pretreatment or fiber separation. 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 findings are published (DOI: 10.1007/s42768-026-00316-y) in the journal.
