Assessing a low-cost methane sensor quantification system for use in complex rural and urban environments

Abstract

Abstract.Low-cost sensors have the potential to facilitate the exploration of air quality issues on new temporal and spatial scales. Here we evaluate a low-cost sensor quantification system for methane through its use in two different deployments. The first, a one-month deployment along the Colorado Front Range includes sites near active oil and gas operations in the Denver-15Julesberg basin. The second deployment in an urban Los Angeles neighborhood, an subject to complex mixture of air pollution sources including oil operations. Given its role as a potent greenhouse gas, new low-cost methods for detecting and monitoring methane may aid in protecting human and environmental health. In this paper, we assess a number of linear calibration models to convert raw sensor signals into ppm concentration values. We also examine different choices that can be made during calibration and data processing, and explore cross-sensitivities that impact this sensor type. The results 20 illustrate the accuracy of the Figaro TGS 2600 sensor when methane is quantified from raw signals using the techniques described. The results also demonstrate the value of these tools for examining air quality trends and events on small spatial and temporal scales as well as their ability to characterize an area -highlighting their potential to provide preliminary data that can inform more targeted measurements or supplement existing monitoring networks.

Methane Mitigation: Methods to Reduce Emissions, on the Path to the Paris Agreement

“…For typical small quadcopter and octocopter drones, the lifting ability is sufficient to carry small sensors able to achieve methane measurement to moderate precision. Most low‐cost low‐weight sensors are capable of measuring methane to 2‐ppm precision (Collier‐Oxandale et al, ; Shah et al, ), which should be capable of detecting significant emissions around known candidate sites. However the precision and accuracy of lightweight small sensors is currently poor compared to vehicle‐mounted or static ground‐mounted instruments.…”

“…Aircraft, UAV, and vehicle surveys can now be augmented by direct on‐site continuous monitoring, which is now feasible around production facilities, to watch superemitters and potential super‐emitters across their life cycle, using low cost sensors such as those described by Collier‐Oxandale et al (). Similarly, to achieve higher precision on large offshore gas platforms, automated cavity‐based analyzers can be linked to air inlets distributed around the platform (e.g., an “octopus” design, with air hoses feeding via a central multivalve to the analyzer).…”

“…“Habitually” high methane air commonly exists in many places, ranging from near vents of domestic boilers and water heaters to the surrounds of industrial gas handling facilities such as compressor stations and gas distribution centers (Figure ) (Schwietzke, Pétron, et al, ; Subramanian et al, ; Zavala‐Araiza et al, ). In dealing with the high numbers of small leaks and emissions, low‐cost sensors are becoming capable of detecting methane anomalies at the sub‐ppm level (e.g., Collier‐Oxandale et al, ). Just as smoke detectors are now ubiquitous, so methane sensors could be widely deployed to identify leaks rapidly.…”

Understanding the ability of low-cost MOx sensors to quantify ambient VOCs

“…We used analysis of variance to determine what the differences in selectivities might be and the results of this analysis are listed in Tables 5 and 6. The application of this technique is similar to previous studies where it was used to determine the effects of confounding species (Collier-Oxandale et al, 2018b;Eugster & Kling et al, 2012). These tables list the results of multiple runs in which different variables were included to determine their ability to explain the variance in the raw sensor signals.…”

“…CC BY 4.0 License. This deployment is described in greater detail in our previous paper (Collier-Oxandale et al, 2018b). While VOC quantification was not the original intent of the deployment, it was something we were able to explore from the unique dataset provided through this co-location.…”