Vehicle-Based Methane Surveys for Finding Natural Gas Leaks and Estimating Their Size: Validation and Uncertainty

Abstract

Managing leaks in urban natural gas (NG) distribution systems is important for reducing methane emissions and costly waste. Mobile surveying technologies have emerged as a new tool for monitoring system integrity, but this new technology has not yet been widely adopted. Here, we establish the efficacy of mobile methane surveys for managing local NG distribution systems by evaluating their ability to detect and locate NG leaks and quantify their emissions. In two cities, three-quarters of leak indications from mobile surveys corresponded to NG leaks, but local distribution companies' field crews did not find most of these leaks, indicating that the national CH 4 activity factor for leaks in local NG distribution pipelines is underestimated by a factor of 2.4. We found the median distance between mobile-estimated leak locations and actual leak locations was 19 m. A comparison of emission quantification methods (mobile-based, surface enclosure, and tracer ratio) found that the mobile method overestimated leak magnitude for the smallest leaks but accurately estimated size for the largest leaks that are responsible for the majority of total emissions. Across leak sizes, mobile methods adequately rank relative emission rates for repair prioritization, and they are easily deployed and offer efficient spatial coverage.

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

“…In Boston, 7% of leak sources contributed 50% of emissions (Hendrick et al, 2016) and in U.S. cities, it is estimated (von Fischer et al, 2017) that repairs to the largest 20% of pipeline leaks would cut losses by half. Leak prioritization by mobile measurement is now rapid, inexpensive, and effective (Weller et al, 2018).…”

Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

“…Besides quantifying urban CH 4 emissions using fixed sites, XCH 4 , aircraft data and inverse modeling studies, measurements from simpler vehicle‐based platforms have been hugely successful in identifying the importance of natural gas infrastructure in different cities (e.g., Lamb et al, ; McKain et al, ; Phillips et al, ). Such surveys often do not rely on exact quantification of CH 4 emission rates from each source location in the city but can use more empirical methods to translate concentration enhancements into emission rate estimates (e.g., von Fischer et al, ; Weller et al, ). Using this approach, it is possible to quickly rank sources into categories, which then allow more efficient repair schedules and targeted mitigation efforts.…”

Implications of Sampling Methods on Geospatial Mapping of Methane Sources

“…Researchers have implemented methane detection systems to quantify natural gas emissions [14][15][16][17][18][19][20][21][22].…”

“…Researchers have operated vehicles with methane analyzers for methane detection [14][15][16][17][18]23], methane quantification [19-21, 24, 25], and methane quantification method comparisons [22]. Picarro Inc. and Los Gatos Research have created commercially available mobile methane detection services using their closed-path methane analyzers [26,27].…”

“…Von Fischer et al and Weller et al outfitted Google ® Street View Cars with a methane analyzer for methane quantification and comparisons [22,24]. Using controlled releases in Fort Collins, Colorado, a methane leak rate algorithm was created using the methane reported by a Picarro G2301 sampling at 2 Hz [24].…”