Revolutionizing cotton scouring: From ancient methods to eco-friendly breakthroughs

Cotton scouring, a critical pretreatment in textile wet processing, has historically relied on alkaline methods that consume 10–20 L of water per kilogram of fabric and generate effluents with chemical oxygen demand (COD) of 2000–3500 mg/L, often exceeding sustainability thresholds. This review evaluates conventional and emerging scouring technologies with respect to technical efficiency, environmental performance, and economic viability. Based on the reviewed data, the enzymatic scouring reduces COD to 300–600 mg/L and < 3% fiber strength loss, though with longer processing times (90–120 min). Ultrasound-assisted methods shorten treatment to 20–40 min and achieve 85–90% wax removal, while plasma scouring reduces water use to 1–2 L/kg and achieves effluents < 100 mg/L COD. Supercritical CO₂ (scCO₂) enables near waterless operation with < 1% fiber strength loss but requires capital costs of USD 200,000–500,000. Nanotechnology-based scouring achieves 85–90% impurity removal with COD 200–400 mg/L while cutting surfactant use by up to 45%. Economic analysis shows alkaline scouring remains cheapest ($0.50–1.20/kg), whereas enzymatic and ultrasound methods achieve 2–4-year return on investment (ROI), and scCO₂ adoption is largely confined to high-margin markets. Barriers include high capital intensity, operational complexity, and cultural resistance, as 87% of global brands still specify alkaline-scoured fabrics. However, policy drivers such as the EU Industrial Emissions Directive and Digital Product Passport (2026) are catalyzing the adoption of emerging scouring techniques. Looking ahead, microbial scouring, lab-grown cotton, and blockchain traceability could render scouring near zero-impact by 2035. This synthesis underscores the urgent need for integrated technical, economic, and regulatory strategies to advance sustainable textile pretreatment globally.