Life cycle water footprint assessment of modern coal chemical industry coupled with CCUS technology

This study employs life cycle assessment (LCA) to systematically quantify the water footprints of six major modern coal chemical (MCC) technologies integrated with carbon capture, utilization, and storage (CCUS), including direct/indirect coal-to-liquids (DCL/ICL), coal-to-natural gas (SNG), coal-to-olefins (CTO), coal-to-ethylene glycol (CTE), and coal-to-methanol (CTM). Results reveal significant variations in water footprints across technologies. CTO exhibits the highest total water footprint (blue: 38.18 t water/ton product; gray: 155.33 t H 2 O/ton product), driven by complex processes, high coal consumption (5.87–6.15 kg/kg), and direct water use (17.2–22 kg/kg). In contrast, CTNG shows the lowest footprints (blue: 16.55 t water/ 1 0 3 m 3 ; gray: 76.15 t water/ 1 0 3 m 3 ). Blue water dominates in production stages (e.g., process/cooling water) and coal mining/washing, with CCUS contributing 12.3–18.7% via electricity consumption. Gray water primarily stems from wastewater discharge in production and coal processing. Direct water use and wastewater discharge account for > 80% of total footprints, while indirect electricity-related impacts contribute 15%–22%. Sensitivity analysis indicates that ± 50% changes in electricity emission factors alter blue and gray water footprints by ± 4.0–7.4% and ± 4.56–6.16%, respectively, with ICL exhibiting the highest sensitivity. Given China’s coal-water spatial mismatch, targeted MCC-CCUS deployment is recommended in regions with balanced coal-water resources and viable CO 2 storage (e.g., Xinjiang, Shaanxi, Shandong, Hebei, Heilongjiang). The findings emphasize lifecycle water management, renewable energy integration, and regionally tailored strategies to reconcile water–carbon trade-offs in coal-based industries.