The N(itrogen)- and P(hosphorus)-Related Grey Water Footprints of Domestic and Industrial Water Use—A Global Analysis from 1990 to 2019

Freshwater pollution by nutrients is a global concern. While agriculture is the largest contributor globally, domestic and industrial emissions are responsible for substantial emission hotspots worldwide. To this end, this paper presents the global grey water footprint (GWF) of nitrogen (N) and phosphorus (P) from domestic and industrial sources as a water pollution indicator. GWFs are displayed as gridded datasets with 5 × 5 arc minute resolution annually from 1990 to 2019, extending previous time series. Methodologically, the domestic GWF calculations were refined but were largely based on previous GWF studies. For industrial GWFs, this study presents a novel approach to estimating emissions based on country-specific industrial-to-domestic load ratios instead of the uniform ratios used in earlier studies. The global N-related GWF rose from 2.6 × 1012 m3/yr to 6.3 × 1012 m3/yr between 1990 and 2019. During the same period, the P-related GWF increased from 75.2 × 1012 m3/yr to 194.5 × 1012 m3/yr. Domestic wastewater is the dominant contributor, with hotspots in densely populated regions, such as East China, North India, and parts of Africa. Industrial contributions show relevance in heavily industrialized areas with limited wastewater treatment infrastructure. Population growth was the primary driver of increased GWFs, particularly in regions with limited sanitation and wastewater treatment. This reflects the need to improve these to mitigate nutrient pollution.