Production of Biogas from Anaerobic Co-digestion of Textile Sludge: Options of Sustainable Sludge Management

Textile industry wastewater treatment generates large quantities of hazardous sludge, posing significant environmental challenges, particularly in developing countries like Ethiopia where open dumping remains common practice. This study investigated anaerobic co-digestion (ACoD) of textile semi-liquid sludge (TSLS) with cow dung (CD) as a sustainable sludge management and renewable energy recovery strategy. Batch experiments were conducted using four TSLS:CD mixing ratios (100:0, 75:25, 50:50, 25:75) under three temperature regimes (ambient ~25°C, 30°C, and 35°C) over a 30-day digestion period. Physicochemical characterization revealed raw TSLS had high organic content (VS: 76.91±0.681 g/L) but suboptimal C/N ratio (13.68) and alkaline pH (8.18), making mono-digestion inefficient. Co-digestion with CD significantly improved substrate properties, with the 50:50 ratio achieving optimal C/N balance (24.99) and near-neutral pH (7.47). This configuration produced maximum biogas yield of 1,533 mL at 35°C with 66.3% methane content, approximately ten times higher than mono-digestion (143 mL). Temperature significantly influenced process kinetics, with 35°C demonstrating fastest biogas initiation (day 3) and highest cumulative yields. The 50:50 ratios consistently outperformed other mixtures across all temperatures, confirming that substrate balancing is critical for process stability. These findings establish ACoD as a technically viable waste-to-energy pathway for Ethiopia's textile sector, transforming hazardous sludge into valuable renewable energy while promoting circular economy principles and mitigating environmental pollution from open dumping practices.