Single-blind validation of space-based point-source methane emissions detection and quantification

Abstract

Satellites are increasingly seen as a tool for identifying large greenhouse gas point sources for mitigation, but independent verification of satellite performance is needed for acceptance and use by policy makers and stakeholders. We conduct to our knowledge the first single-blind controlled methane release testing of satellite-based methane emissions detection and quantification, with five independent teams analyzing data from one to five satellites each. Teams correctly identified 71% of all emissions, ranging from 0.20 [0.19, 0.21] metric tons per hour (t/h) to 7.2 [6.8, 7.6] t/h. Over three-quarters (78%) of quantified estimates fell within ±50% of the metered value, comparable to airplane-based remote sensing technologies. The relatively wide-area Sentinel-2 and Landsat 8 satellites detected emissions as low as 1.4 [1.3, 1.5, 95% confidence interval] t/h, while GHGSat’s targeted system quantified an 0.20 [0.19, 0.21] t/h emission to within 13%. While the fraction of global methane emissions detectable by satellite remains unknown, we estimate that satellite networks could see 18-81% of total oil and natural gas system emissions detected in a recent survey of a high-emitting basin.

Investigating high methane emissions from urban areas detected by TROPOMI and their association with untreated wastewater

“…One of them is within the urban hotspot, one corresponds to an area with a minor enhancement in TROPOMI XCH4 but with limited data availability due to the presence of surface water, and the remaining two do not match any enhancement in the TROPOMI concentrations. These are on the edge of the detection limit for TRO-POMI (10 tonnes per hour [45,46]). In contrast, the urban enhancement of 21 ppb is well above the TRO-POMI detection limit and suggests that emissions in Dhaka are well in excess of those of the surrounding regions.…”

Evaluating methane emission quantification performance and uncertainty of aerial technologies via high-volume single-blind controlled releases

“…Flow rates > 500 kg h -1 CH4 were released sparingly due to the high cost of such tests. Flow rates > 1000 kg h -1 CH4 most commonly coincided with satellite overpasses to maximize efficient use of gas [29].…”

Towards multi-scale measurement-informed methane inventories: reconciling bottom-up inventories with top-down measurements using continuous monitoring systems

“…Satellite measurements can capture super-emitters on a global scale, but have a high detection threshold 27 and only quantified emissions on 1 of 40 overflights performed during this field campaign. Drone and aerial measurements have reasonably well characterized quantification accuracy 31,32 but are subject to sampling error, which has been found to introduce negative bias on cumulative emission estimates.…”

“…Ground-based OGI+Hi-Flow measurements are not included in the TDA because they are poorly suited for capturing total site-level emissions. [24][25][26] Satellite measurements from GHGSat are also not included because of the system's high detection threshold (100 kg/hr 27 ), which we determined to be out of line with the project's focus on both small and large emissions. We create three levels of TDA: site-, operator-, and basin-level.…”