Using satellites to characterize urban methane emissions in support of emission mitigation

Methane emissions from waste dominate urban emissions and provide a key pathway for emission mitigation.We quantify 2023 methane emissions across ten major cities in the Global South (Abidjan, Buenos Aires, Brasilia, Dakar, Delhi, Lagos, Nairobi, Rio de Janeiro, Santo Domingo, and São Paulo) at ~12-km spatial resolution using TROPOspheric Monitoring Instrument (TROPOMI) observations (5.5 km × 7.0 km at nadir)within a Bayesian inversion framework implemented in the Integrated Methane Inversion (IMI). Prior emissions come from the Global Fuel Exploitation Inventory (GFEI v2) for fossil fuel and EDGAR v8 for other anthropogenic emissions. The high-resolution inversion improves the spatial attribution of methane emissions, showing localized enhancements consistent with GHGSat facility scale (25 × 25 m²) observations of landfills in the cities. Including GHGSat-based estimates in the landfill prior emissions further improves the sensitivity and grid-level results of the inversion, while posterior urban emissions with and without GHGSat are consistent. Sparse TROPOMI observation density limits inversion precision for four of the cities. Our urban estimates show substantial discrepancies with prior emissions (-70% to +141%), with Buenos Aires showing the largest increase. Local inventory evaluation shows that EDGAR systematically underestimates grid-level landfill emissions compared to GHGSat due to insufficient site-level information on the spatial allocation of emissions. Landfills contribute 7 to 53 % of total urban methane emissions across the ten cities, with emissions concentrated on the active surface based on GHGSat, demonstrating the value of multi-tier satellite observations to support emission mitigation.