Informing Methane Emissions Inventories Using Facility Aerial Measurements at Midstream Natural Gas Facilities

Real-Time Visual Monitoring and High Spatiotemporal-Resolution Mapping of Air Pollutants Using a Drone-Mass Spectrometer System

Volatile organic compounds (VOCs) play multifaceted roles in the formation of air pollutants. Real-time online monitoring of VOCs is highly needed for understanding their emission sources, environmental impacts, health effects, and climate changes, as many analytical methods are limited to field detection. In this work, a flying-drone-based mass spectrometer (drone-MS) system was developed for visual real-time monitoring of complex VOCs and mapping their diffusions and distributions in the air along with spatiotemporal, geospatial, and environmental information that varies with the flight paths. Analytical performances of the drone-MS system were investigated by detecting a mixture of 18 VOCs, showing high sensitivity (limits of detection, LODs: 1.10-17.91 μg/m3; limits of quantification, LOQs: 3.84-37.61 μg/m3), good reproducibility (relative standard deviations, RSDs, intraday: 0.96-16.49%; interday: 1.17-18.28%; n = 7), and excellent quantitative ability (R2 > 0.99). Online monitoring of complex VOCs was successfully obtained at high temporal resolution (1.0 s) and high spatial resolution (2.0 m), providing an accurate source apportionment of different VOC emissions. Furthermore, practical applications of urban air quality monitoring and spatial distribution mapping of complex VOCs in air were also demonstrated. Overall, this methodology offers new possibilities for the online monitoring of complex VOCs in the air, effectively tackling the longstanding challenge of accurately characterizing complex VOCs and their diffusions and distributions.

Multiscale Measurements of Greenhouse Gas Emissions at U.S. Natural Gas Liquefaction Terminals

Addressing methane emissions across the liquefied natural gas (LNG) supply chain is key to reducing climate impacts of LNG. Actions to address methane emissions have emphasized the importance of the use of measurement-informed emissions inventories given the systematic underestimation in official greenhouse gas (GHG) emission inventories. Despite significant progress in field measurements of GHG emissions across the natural gas supply chain, no detailed measurements at US liquefaction terminals are publicly available. In this work, we conduct multiscale, periodic measurements of methane and carbon dioxide emissions at two US LNG terminals over a 16-month campaign. We find that methane emission intensity varied from 0.007% to 0.045%, normalized to methane in LNG production. Carbon dioxide emissions accounted for over 95% of total GHG emissions using 100-year global warming potential (GWP) for methane. Thus, contrary to observations across other natural gas supply chain segments, we find that reported GHG emissions intensity closely matches measurement informed GHG emissions intensity of 0.24-0.27 kg CO2e/kg CH4. In the context of developing LNG supply chain emissions intensity, we conclude that the use of the Greenhouse Gas Reporting Program emissions intensity provides reasonably accurate estimates of total GHG emissions at LNG terminals.

Progress in monitoring methane emissions from landfills using drones: an overview of the last ten years

Solid waste landfills are responsible for much of the anthropogenic methane emitted from the waste sector. The quantification of fugitive CH4 emissions from a landfill is to date characterised by high uncertainty and several methodologies have been devised to estimate emission fluxes. Unmanned Aerial Vehicles (UAVs, also known as drones) are revolutionising the way CH4 emission monitoring is conceived and offer new opportunities for quantifying emission fluxes from a landfill, mainly due to recent advances in sensor miniaturisation that make these instruments lighter and more suitable to be equipped on a drone. The paper analyses publications from the period 2014-2024 that illustrate UAV-based methods that can be used for this purpose, identifying experiences in the field and the current state of research. The review has highlighted a current research status characterised by a strong experimental focus, with few tests carried out in landfills under real emission conditions (33 % of the reviewed papers). Since 2018, there has been a growing interest in open-path sensors, tested in some controlled-release experiments according to different configurations which have given promising results, but experiences are limited and there are no experiments conducted directly in landfills. In general, the UAV-based methods identified by this systematic review are characterised by unclear uncertainties. Drones are a viable alternative to traditional monitoring methods at landfills and allow data to be acquired with a spatial and temporal resolution that can hardly be achieved by other low-cost methods. However, further studies and field trials are needed to better understand methodological aspects: especially the uncertainty of each step in the quantification process need to be properly analysed and quantified more precisely.

Unaddressed Uncertainties When Scaling Regional Aircraft Emission Surveys to Basin Emission Estimates

Wide-area aerial methods provide comprehensive screening of methane emissions from oil and gas (O & G) facilities in production basins. Emission detections ("plumes") from these studies are also frequently scaled to the basin level, but little is known regarding the uncertainties during scaling. This study analyzed an aircraft field study in the Denver-Julesburg basin to quantify how often plumes identified maintenance events, using a geospatial inventory of 12,629 O & G facilities. Study partners (7 midstream and production operators) provided the timing and location of 5910 maintenance events during the 6 week study period. Results indicated three substantial uncertainties with potential bias that were unaddressed in prior studies. First, plumes often detect maintenance events, which are large, short-duration, and poorly estimated by aircraft methods: 9.2 to 46% (38 to 52%) of plumes on production were likely known maintenance events. Second, plumes on midstream facilities were both infrequent and unpredictable, calling into question whether these estimates were representative of midstream emissions. Finally, 4 plumes attributed to O & G (19% of emissions detected by aircraft) were not aligned with any O & G location, indicating that the emissions had drifted downwind of some source. It is unclear how accurately aircraft methods estimate this type of plume; in this study, it had material impact on emission estimates. While aircraft surveys remain a powerful tool for identifying methane emissions on O & G facilities, this study indicates that additional data inputs, e.g., detailed GIS data, a more nuanced analysis of emission persistence and frequency, and improved sampling strategies are required to accurately scale plume estimates to basin emissions.