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 in New Zealand and James Cook University in Australia, examined how different textile compositions and mixing ratios affect methane production and process stability.
The findings matter because 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 textiles are difficult to digest alone due to imbalanced carbon-to-nitrogen ratios, recalcitrant keratin in wool, and non-biodegradable polyester in blended fabrics. Food waste, being highly biodegradable and nutrient-rich, offers a promising co-substrate.
The study tested mono- and co-digestion of cotton, polycotton, and wool with food waste under mesophilic conditions, using substrate-to-inoculum ratios of 0.5 and 1 and multiple 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 at a substrate-to-inoculum ratio of 0.5. 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, a 1:1 wool-to-food-waste blend produced almost no methane because of ammonia inhibition, and polycotton and wool showed antagonistic effects. 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 carbon-to-nitrogen ratio stays within the optimal window. Cotton-rich mixtures were especially promising, while polycotton and wool need pretreatment or fiber separation because polyester and keratin resist microbial breakdown. The study was published (DOI: 10.1007/s42768-026-00316-y) in the journal.
For textile manufacturers, waste managers, and biogas operators, the research suggests that co-digesting textile waste with food waste can improve methane yields, stabilize digesters, and divert waste from landfill. The best results came from optimizing substrate-to-inoculum ratio and carbon-to-nitrogen balance, particularly when food waste exceeded 80% of the feedstock. Pretreatment strategies such as thermal hydrolysis for cotton and wool, and environmentally friendly solvents to separate polyester from blended fabrics, could further improve digestibility. Digestate quality also matters: most co-digestion treatments produced free ammonia nitrogen within safe biofertilizer limits, although polycotton and wool blends exceeded inhibitory thresholds.
The study provides a simple screening tool, the co-digestion performance index, to identify promising feedstock combinations before scaling up. As pressure mounts to reduce waste and transition to renewable energy, these findings could help industry turn problematic waste streams into valuable resources. More information is available through Chuanlink Innovations.
