Estimating global shipborne domestic wastewater using AIS data: A bottom-up assessment of cargo and container ships

The rapid growth of global shipping has raised increasing concerns about domestic wastewater generated by ships, yet its global spatiotemporal patterns remain insufficiently understood. This study integrated global AIS data from 2022 with a bottom-up model to estimate the potential domestic wastewater generation from cargo ships and container ships. Approximately 1.56 × 10 9 m 3 of domestic wastewater was generated annually, comprising 1.22 × 10 9 m 3 of greywater and 3.37 × 10 8 m 3 of blackwater. Cargo ships accounted for 73.44% of the total, whereas container ships accounted for 26.56%. The Pacific Ocean was the dominant contributor, accounting for approximately 64% of global wastewater generation. Spatially, wastewater generation was concentrated along major shipping routes and in coastal waters with intensive vessel activity. Its spatial overlap with marine protected areas was particularly evident in European, East and Southeast Asian, Australian, and American coastal waters. Wastewater generation reached its minimum in February and peaked in August, with fluctuations exceeding 40%. Considering the uncertainties examined in crew complement and per-capita wastewater generation rates, the global estimate ranged from 9.96 × 10 8 to 2.26 × 10 9 m 3 . These results provide a global characterization of potential wastewater generation and help identify priority regions for further monitoring and assessment.