Increased Giga-Cubic Meters of the Water Footprint of China’s Coal Caused by Washing

Coal washing plays a vital role in improving coal quality and reducing atmospheric pollutant emissions from coal combustion. However, the water footprint burdens caused by substantial freshwater consumption and wastewater discharge remain poorly understood. In this study, a comprehensive water footprint framework for coal washing was developed and used for a bottom-up analysis based on firsthand data from 2,367 coal washing plants across China in 2022. Compared with the scenario where coal was not washed, the national coal washing industry increases the water footprint by 7.38 Gm3, bringing the total water footprint of China’s coal supply chain to 27.68 Gm3, with gray water accounting for 90.9%. The water footprint intensities of commercial coal varied between 6.93 and 27.33 m3/t depending on the washing technologies, with a national average of 8.73 m3/t. Among the various technologies, jigging and jigging-based combined processes demonstrated relatively low water footprint intensities. From a production perspective, the spatial distribution of water footprint intensities in China exhibits a “high in the south and low in the north” pattern. However, an interprovincial transfer of 12.72 Gm3 of water footprint exacerbated the spatial mismatch between coal resources and water availability, owing to mismatches between production and consumption centers and prevailing trade flows. This study highlights the significant contribution of coal washing to the total water footprint of the coal life cycle and underscores the urgent need to incorporate water footprint balance into policies and decision-making regarding coal washing practices.