Quantifying Methane Emissions from Natural Gas Water Heaters

Lebel, Eric D.; Lu, H.; Speizer, S.; Finnegan, Colin; Jackson, Robert B.

doi:10.1021/acs.est.9b07189

Cited by 42 publications

(56 citation statements)

References 13 publications

(30 reference statements)

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“…The footprints were convolved with a 1-km resolution prior model of anthropogenic and biogenic CH 4 emissions previously described by McKain et al ( 4 ), which was augmented with updated landfill and NG point source fluxes ( 17 – 19 ), residential ( 20 – 22 ) and commercial ( 23 ) building losses, and seasonally varying wetland emissions ( 24 ) ( SI Appendix , section S2 ). The inventory also included newly reported pipeline losses from Weller et al ( 25 ), who assessed pipeline leaks with methane analyzers driven through four cities, covering ∼10,000 km of pipelines.…”

Section: Methodsmentioning

confidence: 99%

Majority of US urban natural gas emissions unaccounted for in inventories

Sargent

Floerchinger

McKain

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Across many cities, estimates of methane emissions from natural gas (NG) distribution and end use based on atmospheric measurements have generally been more than double bottom-up estimates. We present a top-down study of NG methane emissions from the Boston urban region spanning 8 y (2012 to 2020) to assess total emissions, their seasonality, and trends. We used methane and ethane observations from five sites in and around Boston, combined with a high-resolution transport model, to calculate methane emissions of 76 ± 18 Gg/yr, with 49 ± 9 Gg/yr attributed to NG losses. We found no significant trend in the NG loss rate over 8 y, despite efforts from the city and state to increase the rate of repairing NG pipeline leaks. We estimate that 2.5 ± 0.5% of the gas entering the urban region is lost, approximately three times higher than bottom-up estimates. We saw a strong correlation between top-down NG emissions and NG consumed on a seasonal basis. This suggests that consumption-driven losses, such as in transmission or end-use, may be a large component of emissions that is missing from inventories, and require future policy action. We also compared top-down NG emission estimates from six US cities, all of which indicate significant missing sources in bottom-up inventories. Across these cities, we estimate NG losses from distribution and end use amount to 20 to 36% of all losses from the US NG supply chain, with a total loss rate of 3.3 to 4.7% of NG from well pad to urban consumer, notably larger than the current Environmental Protection Agency estimate of 1.4% [R. A. Alvarez et al., Science 361, 186–188 (2018)].

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Section: Methodsmentioning

confidence: 99%

Majority of US urban natural gas emissions unaccounted for in inventories

Sargent

Floerchinger

McKain

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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“…At the GGL, FlexFoil SKC bag samples were each analyzed for methane mole fractions and δ 13 C. Methane mole fractions were determined using a Picarro G1301 CRDS, which measured every 5 s for 2 min, resulting in a precision ±0.3 ppb (Lowry et al, 2020;France et al, 2016;Zazzeri et al, 2015). Each sample was then measured for stable isotopes (δ 13 C-CH 4 ) using an Elementar Trace gas and continuous-flow gas chromatography isotope ratio mass spectrometry (CF-GC-IRMS) system (Fisher et al, 2006), which has an average repeatability of ±0.05 ‰.…”

Section: Lab Isotopic Analysis Of δ 13 C and δDmentioning

confidence: 99%

“…Each sample was measured three times for δ 13 C-CH 4 , and the duration of each analysis was ≈ 20 min. Both instruments are calibrated weekly to the WMO X2004A methane scale using air-filled cylinders that were measured by the National Oceanic and Atmospheric Administration (NOAA) and cylinders that were calibrated against the NOAA scale by the MPI-BGC (France et al, 2016;Lowry et al, 2020).…”

Section: Lab Isotopic Analysis Of δ 13 C and δDmentioning

confidence: 99%

“…Hu et al (2018) reported 2 ± 2.1 ppb ppm −1 in a tunnel but 12±5.3 ppb ppm −1 on roads. In addition to car exhaust, there are other combustion sources that can affect CH 4 and CO 2 mole fractions at the street level, including natural gas water heaters (CH 4 : CO 2 ratio of ≈ 2 ppb ppm −1 ; Lebel et al, 2020) and restaurant kitchens. Based on the CH 4 : CO 2 ratio (ppb ppm −1 ) criterion defined above (see Sect.…”

Section: Attribution Of Ch 4 Emissions Across Utrecht Andmentioning

confidence: 99%

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Methane mapping, emission quantification, and attribution in two European cities: Utrecht (NL) and Hamburg (DE)

et al. 2020

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Abstract. Characterizing and attributing methane (CH4) emissions across varying scales are important from environmental, safety, and economic perspectives and are essential for designing and evaluating effective mitigation strategies. Mobile real-time measurements of CH4 in ambient air offer a fast and effective method to identify and quantify local CH4 emissions in urban areas. We carried out extensive campaigns to measure CH4 mole fractions at the street level in Utrecht, the Netherlands (2018 and 2019), and Hamburg, Germany (2018). We detected 145 leak indications (LIs; i.e., CH4 enhancements of more than 10 % above background levels) in Hamburg and 81 LIs in Utrecht. Measurements of the ethane-to-methane ratio (C2:C1), methane-to-carbon dioxide ratio (CH4:CO2), and CH4 isotope composition (δ13C and δD) show that in Hamburg about 1∕3 of the LIs, and in Utrecht 2∕3 of the LIs (based on a limited set of C2:C1 measurements), were of fossil fuel origin. We find that in both cities the largest emission rates in the identified LI distribution are from fossil fuel sources. In Hamburg, the lower emission rates in the identified LI distribution are often associated with biogenic characteristics or (partly) combustion. Extrapolation of detected LI rates along the roads driven to the gas distribution pipes in the entire road network yields total emissions from sources that can be quantified in the street-level surveys of 440±70 t yr−1 from all sources in Hamburg and 150±50 t yr−1 for Utrecht. In Hamburg, C2:C1, CH4:CO2, and isotope-based source attributions show that 50 %–80 % of all emissions originate from the natural gas distribution network; in Utrecht more limited attribution indicates that 70 %–90 % of the emissions are of fossil origin. Our results confirm previous observations that a few large LIs, creating a heavy tail, are responsible for a significant proportion of fossil CH4 emissions. In Utrecht, 1∕3 of total emissions originated from one LI and in Hamburg >1/4 from two LIs. The largest leaks were located and fixed quickly by GasNetz Hamburg once the LIs were shared, but 80 % of the (smaller) LIs attributed to the fossil category could not be detected and/or confirmed as pipeline leaks. This issue requires further investigation.

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“…4 and residential or commercial consumption of NG (Table2). NG exhaust from diverse residential implements (for heating, water heating, and cooking) contains some unburned CH 4 due to inevitable incomplete combustion(Lebel et al 2020;Merrin and Francisco 2019) Helfter et al (2016). suggest that in winter, increases in CH 4 concentrations above the background level could be attributed to CH 4 losses from over-pressurized pipelines as a response to an increase in gas demand.…”

mentioning

confidence: 99%

Analysis of the Influence of Sources on the Spatial Variation in Atmospheric Methane Concentrations in the City of Tandil, Argentina

Fusé

Stadler

Picone

et al. 2021

Preprint

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There is an overall trend in urban methane (CH4) emissions due to the presence of several sources; however, differences exist between cities, and therefore further local research should be undertaken. The present study analyzes the spatiotemporal variation in atmospheric CH4 concentrations during a year at ten sampling sites in the urban core of a medium-sized city. The mean annual atmospheric CH4 concentrations varied between 2.02 ppm and 5.45 ppm; the maximum concentrations were found in a site close to a wastewater treatment plant (WWTP), presenting a significant increase toward the summer. In the rest of the sites, the maximum concentrations were recorded in the coldest months due to the influence of combustion sources dependent on natural gas (NG). An exploratory regression analysis was performed, in which the variables “homes connected to the gas network” and “distance from compressed NG stations” each explained 66 and 65% of the spatial variation of the atmospheric CH4 concentrations at the 9 sites (excluding that one nearest the WWTP). The results show the need to prevent NG leaks in all urban areas to reduce the emissions of this potent greenhouse gas, which, at the same time, will provide economic benefits for the sectors involved.

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Quantifying Methane Emissions from Natural Gas Water Heaters

Cited by 42 publications

References 13 publications

Majority of US urban natural gas emissions unaccounted for in inventories

Majority of US urban natural gas emissions unaccounted for in inventories

Methane mapping, emission quantification, and attribution in two European cities: Utrecht (NL) and Hamburg (DE)

Analysis of the Influence of Sources on the Spatial Variation in Atmospheric Methane Concentrations in the City of Tandil, Argentina

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