Quantifying Agricultural Methane Emissions Using Satellite Observations

Methane (CH₄) is the second most important greenhouse gas after CO₂, and its emissions from the agricultural sector, particularly rice paddies and dairy farms, remain highly uncertain and challenging to quantify. While recent advancements in satellite technology, such as high spatial resolution instruments, have enabled the detection of methane sources from global to facility scales, agricultural emissions still pose challenges. These emissions are typically diffuse and area-like, making them less detectable by targeted satellites like GHGSat and EMIT, which are better suited for isolated point sources such as oil/gas facilities or landfills. Additionally, agricultural emissions exhibit significant spatiotemporal variability driven by climate conditions, water management practices in rice paddies, and differences in farm types.

In the AGATE project of ESA, we apply an improved divergence method to estimate monthly methane emissions using TROPOspheric Monitoring Instrument (TROPOMI) satellite observations at a 0.1° grid resolution. We focus on major agricultural regions, including the Po Valley in Italy, as well as India and Bangladesh, over the period 2019-2022. To better isolate agricultural emissions, we separate area-like sources (e.g., rice paddies) from isolated point sources. The locations of identified big emitters are cross-validated using bottom-up emission inventories and targeted satellite observations (e.g., EMIT, Carbon Mapper) to minimize the influence of non-agricultural sources. Furthermore, to better understand the seasonality of methane emissions, we analyze the correlations between methane emission variations and auxiliary datasets, such as rice paddy maps and ammonia emissions derived from satellites.