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, substrate-to-inoculum (S/I) ratios, and food waste blending ratios affect methane yields and process stability.
The findings matter because textile waste is generated at enormous scale—about 92 million tonnes disposed of annually—yet current disposal methods remain costly or environmentally problematic. Anaerobic digestion can convert organic-rich waste into biogas, but textiles alone are difficult to digest 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, emerged as a promising co-substrate to overcome these limitations.
The study tested mono- and co-digestion of cotton, polycotton, and wool with food waste under mesophilic conditions, using S/I ratios of 0.5 and 1 and multiple feedstock mixing ratios. Results showed that lower S/I ratios and higher food waste shares generally improved methane production, but performance depended strongly on textile type and carbon-to-nitrogen balance. Cotton performed best in mono-digestion, producing 103 mL/g volatile solids and reaching 25.87% biodegradability at an S/I ratio of 0.5. Co-digestion with food waste further raised methane production, with the highest yield of 129.7 mL/g VS achieved 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 the co-digestion performance index exceeded 1. Kinetic analysis 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. In contrast, polycotton and wool showed antagonistic effects, as polyester resisted degradation and wool's keratin structure limited microbial access.
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. They noted that 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 full study is available via published (DOI: 10.1007/s42768-026-00316-y).
