Abstract
<title>Abstract</title> <p>The textile industry in Ethiopia faces significant environmental challenges due to the generation of large volumes of semi-liquid sludge containing heavy metals and organic contaminants.This study evaluates anaerobic co-digestion as a sustainable solution for managing toxic textile semi-liquid sludge (TSLS) in Ethiopia. TSLS from Arbaminch Textile Share Company was co-digested with cattle manure (CM) at ratios of 100:0, 75:25, 70:30, and 60:40 under three temperature conditions (~ 25°C, 30°C, and 37°C) over a 30-day period. Mono-digestion of TSLS (100:0) was infeasible due to high alkalinity (pH 9.45) and low organic content, producing only 37–133 mL of biogas. However, co-digestion significantly enhanced performance. The 60:40 (TSLS:CM) ratio operated under upper mesophilic conditions (37°C) achieved the maximum cumulative biogas yield of 2,597 mL with 66.5% methane content. This temperature condition substantially outperformed lower operational temperatures. Furthermore, co-digestion effectively stabilized toxic heavy metals. Post-digestion analysis showed dramatic reductions in cadmium (366.01 to < 0.026 mg/kg), chromium (156.86 to 2.61 mg/kg), copper (295.42 to 6.54 mg/kg), and zinc (305.88 to 32.03 mg/kg), safely meeting international biosolid standards. Ultimately, co-digesting textile sludge with cattle manure at a 60:40 ratio at 37°C offers a highly viable waste-to-energy solution that recovers renewable energy while mitigating industrial pollution.</p>