Compilation of remote sensing emission estimates of CH4 with environmental parameters and operational practices at US sanitary landfills: what works for mitigation?

From 2016 to 2024, multiple flights were performed over managed landfills in the US, with successful quantification of emissions. The publicly available data from Carbon Mapper as well as not yet published Methane AIR data cover 170 managed landfills with 2202 methane plumes quantifications. Most analyses interpret instantaneous plumes against annual emission rates, assuming the average of the measured flux representative of the yearly emissions. We deliberately avoided this framing, and used reported fluxes in kg CH₄ h⁻¹ normalized by the added amounts of waste only as indicators of the “leak intensity” on a specific year. Operational parameters were extracted from yearly reports under the EPA Greenhouse Gas reporting framework, and the facilities of interest were classified in three aridity levels based on meteorological data.

Our approach allowed us to analyze drivers of change in emissions by taking into account multiple factors. We find that the humidity of a region is one of the main causes for inefficient gas capture in US landfills. We have followed the evolution of the magnitude of CH₄ emissions as well as the improvement of the gas collecting infrastructure as a case study from the highest emitting climate category.

In relatively wet climates, gas collection is more difficult because of higher generation and increased soil humidity. We show that collection can improve with more wells, but reaching the efficiency of dryer climates landfills is very challenging. It is also important, as previous studies have shown, to implement gas collection as soon as possible after the disposal of organic waste.

On the global scale, the emissions of large dump sites in lower income countries can be reduced with appropriate gas collection systems, but best results are to achieve in relatively dry climates. The disposal of organic waste in landfills is even more to be avoided in tropical countries with relatively high precipitations. We emphasize that collaboration with local operators to investigate landfill specific parameters such as organic content is of major importance to design the best mitigation strategies, together with the analysis of environmental data.