Papers on gas leakage from natural gas industry

This is a list of papers on gas leakage from natural gas industry. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (January 8, 2018): Alvarez et al. (2018), Boothroyd et al. (2018), and Omara et al. (2018) added.
UPDATE (September 7, 2018): Dedikov et al. (1999) added.
UPDATE (January 23, 2014): Miller et al. (2013), Karion et al. (2013), Allen et al. (2013), Pétron et al. (2012), Alvarez et al. (2012) added.
UPDATE (February 5, 2012): Howarth et al. (2011), Cathles et al. (2012), and Howarth et al. (2012) added.

Assessment of methane emissions from the U.S. oil and gas supply chain – Alvarez et al. (2018) “Methane emissions from the U.S. oil and natural gas supply chain were estimated by using ground-based, facility-scale measurements and validated with aircraft observations in areas accounting for ~30% of U.S. gas production. When scaled up nationally, our facility-based estimate of 2015 supply chain emissions is 13 ± 2 teragrams per year, equivalent to 2.3% of gross U.S. gas production. This value is ~60% higher than the U.S. Environmental Protection Agency inventory estimate, likely because existing inventory methods miss emissions released during abnormal operating conditions. Methane emissions of this magnitude, per unit of natural gas consumed, produce radiative forcing over a 20-year time horizon comparable to the CO2 from natural gas combustion. Substantial emission reductions are feasible through rapid detection of the root causes of high emissions and deployment of less failure-prone systems.” Ramón A. Alvarez, Daniel Zavala-Araiza, David R. Lyon, David T. Allen, Zachary R. Barkley, Adam R. Brandt, Kenneth J. Davis, Scott C. Herndon, Daniel J. Jacob, Anna Karion, Eric A. Kort, Brian K. Lamb, Thomas Lauvaux, Joannes D. Maasakkers, Anthony J. Marchese, Mark Omara, Stephen W. Pacala, Jeff Peischl, Allen L. Robinson, Paul B. Shepson, Colm Sweeney, Amy Townsend-Small, Steven C. Wofsy, Steven P. Hamburg (2018). Science 13 Jul 2018: Vol. 361, Issue 6398, pp. 186-188. DOI: 10.1126/science.aar7204 [Full text]

Methane Emissions from Natural Gas Production Sites in the United States: Data Synthesis and National Estimate – Omara et al. (2018) “We used site-level methane (CH4) emissions data from over 1000 natural gas (NG) production sites in eight basins, including 92 new site-level CH4 measurements in the Uinta, northeastern Marcellus, and Denver-Julesburg basins, to investigate CH4 emissions characteristics and develop a new national CH4 emission estimate for the NG production sector. The distribution of site-level emissions is highly skewed, with the top 5% of sites accounting for 50% of cumulative emissions. High emitting sites are predominantly also high producing (>10 Mcfd). However, low NG production sites emit a larger fraction of their CH4 production. When combined with activity data, we predict that this creates substantial variability in the basin-level CH4 emissions which, as a fraction of basin-level CH4 production, range from 0.90% for the Appalachian and Greater Green River to >4.5% in the San Juan and San Joaquin. This suggests that much of the basin-level differences in production-normalized CH4 emissions reported by aircraft studies can be explained by differences in site size and distribution of site-level production rates. We estimate that NG production sites emit total CH4 emissions of 830 Mg/h (95% CI: 530–1200), 63% of which come from the sites producing <100 Mcfd that account for only 10% of total NG production. Our total CH4 emissions estimate is 2.3 times higher than the U.S. Environmental Protection Agency’s estimate and likely attributable to the disproportionate influence of high emitting sites." Mark Omara, Naomi Zimmerman, Melissa R. Sullivan, Xiang Li, Aja Ellis, Rebecca Cesa, R. Subramanian, Albert A. Presto, Allen L. Robinson (2018). Environ. Sci. Technol., 2018, 52 (21), pp 12915–12925. DOI: 10.1021/acs.est.8b03535. [Full text]

Assessing fugitive emissions of CH4 from high-pressure gas pipelines in the UK – Boothroyd et al. (2018) “Natural gas pipelines are an important source of fugitive methane emissions in lifecycle greenhouse gas assessments but limited monitoring has taken place of UK pipelines to quantify fugitive emissions. This study investigated methane emissions from the UK high-pressure pipeline system (National Transmission System – NTS) for natural gas pipelines. Mobile surveys of CH4 emissions were conducted across four areas in the UK, with routes bisecting high-pressure pipelines (with a maximum operating pressure of 85 bar) and separate control routes away from the pipelines. A manual survey of soil gas measurements was also conducted along one of the high-pressure pipelines using a tunable diode laser. For the pipeline routes, there were 26 peaks above 2.1 ppmv CH4 at 0.23 peaks/km, compared with 12 peaks at 0.11 peaks/km on control routes. Three distinct thermogenic emissions were identified on the basis of the isotopic signal from these elevated concentrations with a peak rate of 0.03 peaks/km. A further three thermogenic emissions on pipeline routes were associated with pipeline infrastructure. Methane fluxes from control routes were statistically significantly lower than the fluxes measured on pipeline routes, with an overall pipeline flux of 627 (241–1123 interquartile range) tonnes CH4/km/yr. Soil gas CH4 measurements indicated a total flux of 62.6 kt CH4/yr, which equates to 2.9% of total annual CH4 emissions in the UK. We recommend further monitoring of the UK natural gas pipeline network, with assessments of transmission and distribution stations, and distribution pipelines necessary.” Ian M. Boothroyd, Sam Almond, Fred Worrall, Rosemary K. Davies, Richard J.Davies (2018). Science of The Total Environment, Volumes 631–632, 1 August 2018, Pages 1638-1648. https://doi.org/10.1016/j.scitotenv.2018.02.240. [Full text]

Anthropogenic emissions of methane in the United States – Miller et al. (2013) “This study quantitatively estimates the spatial distribution of anthropogenic methane sources in the United States by combining comprehensive atmospheric methane observations, extensive spatial datasets, and a high-resolution atmospheric transport model. Results show that current inventories from the US Environmental Protection Agency (EPA) and the Emissions Database for Global Atmospheric Research underestimate methane emissions nationally by a factor of ∼1.5 and ∼1.7, respectively. Our study indicates that emissions due to ruminants and manure are up to twice the magnitude of existing inventories. In addition, the discrepancy in methane source estimates is particularly pronounced in the south-central United States, where we find total emissions are ∼2.7 times greater than in most inventories and account for 24 ± 3% of national emissions. The spatial patterns of our emission fluxes and observed methane–propane correlations indicate that fossil fuel extraction and refining are major contributors (45 ± 13%) in the south-central United States. This result suggests that regional methane emissions due to fossil fuel extraction and processing could be 4.9 ± 2.6 times larger than in EDGAR, the most comprehensive global methane inventory. These results cast doubt on the US EPA’s recent decision to downscale its estimate of national natural gas emissions by 25–30%. Overall, we conclude that methane emissions associated with both the animal husbandry and fossil fuel industries have larger greenhouse gas impacts than indicated by existing inventories.” Scot M. Miller, Steven C. Wofsy, Anna M. Michalak, Eric A. Kort, Arlyn E. Andrews, Sebastien C. Biraud, Edward J. Dlugokencky, Janusz Eluszkiewicz, Marc L. Fischer, Greet Janssens-Maenhout, Ben R. Miller, John B. Miller, Stephen A. Montzka, Thomas Nehrkorn, and Colm Sweeney, PNAS, 2013, doi: 10.1073/pnas.1314392110. [Full text]

Methane emissions estimate from airborne measurements over a western United States natural gas field – Karion et al. (2013) “Methane (CH₄) emissions from natural gas production are not well quantified and have the potential to offset the climate benefits of natural gas over other fossil fuels. We use atmospheric measurements in a mass balance approach to estimate CH₄ emissions of 55 ± 15 × 10³ kg h⁻¹ from a natural gas and oil production field in Uintah County, Utah, on 1 day: 3 February 2012. This emission rate corresponds to 6.2%–11.7% (1σ) of average hourly natural gas production in Uintah County in the month of February. This study demonstrates the mass balance technique as a valuable tool for estimating emissions from oil and gas production regions and illustrates the need for further atmospheric measurements to determine the representativeness of our single-day estimate and to better assess inventories of CH₄ emissions.” Anna Karion, Colm Sweeney, Gabrielle Pétron, Gregory Frost, R. Michael Hardesty, Jonathan Kofler, Ben R. Miller, Tim Newberger, Sonja Wolter, Robert Banta, Alan Brewer, Ed Dlugokencky, Patricia Lang, Stephen A. Montzka, Russell Schnell, Pieter Tans, Michael Trainer, Robert Zamora, Stephen Conley, Geophysical Research Letters, Volume 40, Issue 16, pages 4393–4397, 28 August 2013, DOI: 10.1002/grl.50811.

Measurements of methane emissions at natural gas production sites in the United States – Allen et al. (2013) “Engineering estimates of methane emissions from natural gas production have led to varied projections of national emissions. This work reports direct measurements of methane emissions at 190 onshore natural gas sites in the United States (150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers). For well completion flowbacks, which clear fractured wells of liquid to allow gas production, methane emissions ranged from 0.01 Mg to 17 Mg (mean = 1.7 Mg; 95% confidence bounds of 0.67–3.3 Mg), compared with an average of 81 Mg per event in the 2011 EPA national emission inventory from April 2013. Emission factors for pneumatic pumps and controllers as well as equipment leaks were both comparable to and higher than estimates in the national inventory. Overall, if emission factors from this work for completion flowbacks, equipment leaks, and pneumatic pumps and controllers are assumed to be representative of national populations and are used to estimate national emissions, total annual emissions from these source categories are calculated to be 957 Gg of methane (with sampling and measurement uncertainties estimated at ±200 Gg). The estimate for comparable source categories in the EPA national inventory is ∼1,200 Gg. Additional measurements of unloadings and workovers are needed to produce national emission estimates for these source categories. The 957 Gg in emissions for completion flowbacks, pneumatics, and equipment leaks, coupled with EPA national inventory estimates for other categories, leads to an estimated 2,300 Gg of methane emissions from natural gas production (0.42% of gross gas production).” David T. Allen, Vincent M. Torres, James Thomas, David W. Sullivan, Matthew Harrison, Al Hendler, Scott C. Herndon, Charles E. Kolb, Matthew P. Fraser, A. Daniel Hill, Brian K. Lamb, Jennifer Miskimins, Robert F. Sawyer, and John H. Seinfeld, PNAS, 2013, vol. 110 no. 44, 17768–17773, doi: 10.1073/pnas.1304880110. [Full text]

Greater focus needed on methane leakage from natural gas infrastructure – Alvarez et al. (2012) “Natural gas is seen by many as the future of American energy: a fuel that can provide energy independence and reduce greenhouse gas emissions in the process. However, there has also been confusion about the climate implications of increased use of natural gas for electric power and transportation. We propose and illustrate the use of technology warming potentials as a robust and transparent way to compare the cumulative radiative forcing created by alternative technologies fueled by natural gas and oil or coal by using the best available estimates of greenhouse gas emissions from each fuel cycle (i.e., production, transportation and use). We find that a shift to compressed natural gas vehicles from gasoline or diesel vehicles leads to greater radiative forcing of the climate for 80 or 280 yr, respectively, before beginning to produce benefits. Compressed natural gas vehicles could produce climate benefits on all time frames if the well-to-wheels CH₄ leakage were capped at a level 45–70% below current estimates. By contrast, using natural gas instead of coal for electric power plants can reduce radiative forcing immediately, and reducing CH4 losses from the production and transportation of natural gas would produce even greater benefits. There is a need for the natural gas industry and science community to help obtain better emissions data and for increased efforts to reduce methane leakage in order to minimize the climate footprint of natural gas.” Ramón A. Alvarez, Stephen W. Pacala, James J. Winebrake, William L. Chameides, and Steven P. Hamburg, PNAS, 2013, vol. 109 no. 17, 6435–6440, doi: 10.1073/pnas.1202407109. [Full text]

Hydrocarbon emissions characterization in the Colorado Front Range: A pilot study – Pétron et al. (2012) “The multispecies analysis of daily air samples collected at the NOAA Boulder Atmospheric Observatory (BAO) in Weld County in northeastern Colorado since 2007 shows highly correlated alkane enhancements caused by a regionally distributed mix of sources in the Denver-Julesburg Basin. To further characterize the emissions of methane and non-methane hydrocarbons (propane, n-butane, i-pentane, n-pentane and benzene) around BAO, a pilot study involving automobile-based surveys was carried out during the summer of 2008. A mix of venting emissions (leaks) of raw natural gas and flashing emissions from condensate storage tanks can explain the alkane ratios we observe in air masses impacted by oil and gas operations in northeastern Colorado. Using the WRAP Phase III inventory of total volatile organic compound (VOC) emissions from oil and gas exploration, production and processing, together with flashing and venting emission speciation profiles provided by State agencies or the oil and gas industry, we derive a range of bottom-up speciated emissions for Weld County in 2008. We use the observed ambient molar ratios and flashing and venting emissions data to calculate top-down scenarios for the amount of natural gas leaked to the atmosphere and the associated methane and non-methane emissions. Our analysis suggests that the emissions of the species we measured are most likely underestimated in current inventories and that the uncertainties attached to these estimates can be as high as a factor of two.” Gabrielle Pétron, Gregory Frost, Benjamin R. Miller, Adam I. Hirsch, Stephen A. Montzka, Anna Karion, Michael Trainer, Colm Sweeney, Arlyn E. Andrews, Lloyd Miller, Jonathan Kofler, Amnon Bar-Ilan, Ed J. Dlugokencky, Laura Patrick, Charles T. Moore Jr., Thomas B. Ryerson, Carolina Siso, William Kolodzey, Patricia M. Lang, Thomas Conway, Paul Novelli, Kenneth Masarie, Bradley Hall, Douglas Guenther, Duane Kitzis, John Miller, David Welsh, Dan Wolfe, William Neff, Pieter Tans, Journal of Geophysical Research: Atmospheres (1984–2012), Volume 117, Issue D4, 27 February 2012, DOI: 10.1029/2011JD016360. [Full text]

Venting and leaking of methane from shale gas development: response to Cathles et al. – Howarth et al. (2012) “In April 2011, we published the first comprehensive analysis of greenhouse gas (GHG) emissions from shale gas obtained by hydraulic fracturing, with a focus on methane emissions. Our analysis was challenged by Cathles et al. (2012). Here, we respond to those criticisms. We stand by our approach and findings. The latest EPA estimate for methane emissions from shale gas falls within the range of our estimates but not those of Cathles et al. which are substantially lower. Cathles et al. believe the focus should be just on electricity generation, and the global warming potential of methane should be considered only on a 100-year time scale. Our analysis covered both electricity (30% of US usage) and heat generation (the largest usage), and we evaluated both 20- and 100-year integrated time frames for methane. Both time frames are important, but the decadal scale is critical, given the urgent need to avoid climate-system tipping points. Using all available information and the latest climate science, we conclude that for most uses, the GHG footprint of shale gas is greater than that of other fossil fuels on time scales of up to 100 years. When used to generate electricity, the shale-gas footprint is still significantly greater than that of coal at decadal time scales but is less at the century scale. We reiterate our conclusion from our April 2011 paper that shale gas is not a suitable bridge fuel for the 21st Century.” Robert W. Howarth, Renee Santoro and Anthony Ingraffea, Climatic Change, DOI: 10.1007/s10584-012-0401-0. [Full text]

A commentary on “The greenhouse-gas footprint of natural gas in shale formations” by R.W. Howarth, R. Santoro, and Anthony Ingraffea – Cathles et al. (2012) “Natural gas is widely considered to be an environmentally cleaner fuel than coal because it does not produce detrimental by-products such as sulfur, mercury, ash and particulates and because it provides twice the energy per unit of weight with half the carbon footprint during combustion. These points are not in dispute. However, in their recent publication in Climatic Change Letters, Howarth et al. (2011) report that their life-cycle evaluation of shale gas drilling suggests that shale gas has a larger GHG footprint than coal and that this larger footprint “undercuts the logic of its use as a bridging fuel over the coming decades”. We argue here that their analysis is seriously flawed in that they significantly overestimate the fugitive emissions associated with unconventional gas extraction, undervalue the contribution of “green technologies” to reducing those emissions to a level approaching that of conventional gas, base their comparison between gas and coal on heat rather than electricity generation (almost the sole use of coal), and assume a time interval over which to compute the relative climate impact of gas compared to coal that does not capture the contrast between the long residence time of CO₂ and the short residence time of methane in the atmosphere. High leakage rates, a short methane GWP, and comparison in terms of heat content are the inappropriate bases upon which Howarth et al. ground their claim that gas could be twice as bad as coal in its greenhouse impact. Using more reasonable leakage rates and bases of comparison, shale gas has a GHG footprint that is half and perhaps a third that of coal.” Lawrence M. Cathles, Larry Brown, Milton Taam and Andrew Hunter, Climatic Change, DOI: 10.1007/s10584-011-0333-0. [Full text]

Methane and the greenhouse-gas footprint of natural gas from shale formations – Howarth et al. (2011) “We evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life-time of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured—as methane escapes from flow-back return fluids—and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.” Robert W. Howarth, Renee Santoro and Anthony Ingraffea, Climatic Change, Volume 106, Number 4, 679-690, DOI: 10.1007/s10584-011-0061-5. [Full text]

Future development of the upstream greenhouse gas emissions from natural gas industry, focussing on Russian gas fields and export pipelines – Lechtenböhmer & Dienst (2010) “Natural gas makes an increasing contribution to the European Union’s energy supply. Due to its efficiency and low level of combustion emissions this reduces greenhouse gas emissions compared to the use of other fossil fuels. However, being itself a potent greenhouse gas, a high level of direct losses of natural gas in its process chain could neutralise these advantages. Which effect will finally prevail depends on future economical as well as technical developments. Based on two different scenarios of the main influencing factors we can conclude that over the next two decades CH₄ emissions from the natural gas supply chain can be significantly reduced, in spite of unfavourable developments of the supply structures. This, however, needs a substantial, but economically attractive investment into new technology, particularly in Russia.” S. Lechtenböhmer, C. Dienst, Journal of Integrative Environmental Sciences, Volume 7, Issue S1, 2010, Pages 39 – 48, DOI: 10.1080/19438151003774463.

Study on Methane Emission Reduction Potential in China’s Oil and Natural Gas Industry – Liu et al. (2008) A review report of China’s situation with natural gas methane emissions. Junrong Liu and Jun Yao, Michael Gallaher and Jeff Coburn, Roger Fernandez, RTI Project Number 0208702.027, Prepared for U.S. EPA, April 2008. [Full text]

Tapping the leakages: Methane losses, mitigation options and policy issues for Russian long distance gas transmission pipelines – Lechtenböhmer et al. (2007) “The Russian natural gas industry is the world’s largest producer and transporter of natural gas. This paper aims to characterize the methane emissions from Russian natural gas transmission operations, to explain projects to reduce these emissions, and to characterize the role of emissions reduction within the context of current GHG policy. It draws on the most recent independent measurements at all parts of the Russian long distance transport system made by the Wuppertal Institute in 2003 and combines these results with the findings from the US Natural Gas STAR Program on GHG mitigation options and economics. With this background the paper concludes that the methane emissions from the Russian natural gas long distance network are approximately 0.6% of the natural gas delivered. Mitigating these emissions can create new revenue streams for the operator in the form of reduced costs, increased gas throughput and sales, and earned carbon credits. Specific emissions sources that have cost-effective mitigation solutions are also opportunities for outside investment for the Joint Implementation Kyoto Protocol flexibility mechanism or other carbon markets.” Stefan Lechtenböhmer, Carmen Dienst, Manfred Fischedick, Thomas Hanke, Roger Fernandez, Don Robinson, Ravi Kantamaneni and Brian Gillis, International Journal of Greenhouse Gas Control, Volume 1, Issue 4, October 2007, Pages 387-395, doi:10.1016/S1750-5836(07)00089-8.

Greenhouse gases: Low methane leakage from gas pipelines – Lelieveld et al. (2005) “Using natural gas for fuel releases less carbon dioxide per unit of energy produced than burning oil or coal, but its production and transport are accompanied by emissions of methane, which is a much more potent greenhouse gas than carbon dioxide in the short term. This calls into question whether climate forcing could be reduced by switching from coal and oil to natural gas1. We have made measurements in Russia along the world’s largest gas-transport system and find that methane leakage is in the region of 1.4%, which is considerably less than expected and comparable to that from systems in the United States. Our calculations indicate that using natural gas in preference to other fossil fuels could be useful in the short term for mitigating climate change.” J. Lelieveld, S. Lechtenböhmer, S. S. Assonov, C. A. M. Brenninkmeijer, C. Dienst, M. Fischedick & T. Hanke, Nature 434, 841-842 (14 April 2005) | doi:10.1038/434841a.

Estimating methane releases from natural gas production and transmission in Russia – Dedikov et al. (1999)
Abstract: Methane releases from the RAO Gazprom gas production and transmission facilities in Russia were determined in an extensive measurement program carried out in 1996 and 1997. Subsequently, the measurements were extrapolated to the Russian scale. The results show that methane releases from gas transmission are less than 1% of throughput. Methane loss from gas production in northwestern Siberia appears to be relatively small, generally less than 0.1%. The largest methane emissions result from venting during maintenance and repairs, leaks from valves on transmission lines, and from compressor stations. The measurements show that, in the case of leaks, a limited number of major ones accounts for most of the methane releases. Methane emissions expressed as a percentage of the gas volume produced or transported are (rounded figures): production and processing 0.1%, pipelines 0.2%, compressor stations 0.7%, so that the total release by production and transmission in Russia amounts to about 1.0%, i.e. ∼5.4×109 m3/a (∼4 Tg/a). This is consistent with our previous preliminary estimates, indicating that maximum emissions are 1.5–1.8%/a. However, this is generally lower than most other estimates and speculations.
Citation: J.V. Dedikov, G.S. Akopova (VNIIGaz), N.G. Gladkaja (VNIIGaz), A.S. Piotrovskij (Tyumentransgaz), V.A. Markellov (Volgotransgaz), S.S. Salichov (Yamburggazdabuicha), H. Kaesler, A. Ramm, A. Müller von Blumencron, J. Lelieveld (1999). Estimating methane releases from natural gas production and transmission in Russia, Atmospheric Environment, 33(20), 3291-3299, https://doi.org/10.1016/S1352-2310(98)00388-4.

Estimate of methane emissions from the U.S. natural gas industry – Kirchgessner et al. (1997) “Global methane emissions from the fossil fuel industries have been poorly quantified and, in many cases, emissions are not well-known even at the country level. Historically, methane emissions from the U.S. gas industry have been based on sparse data, incorrect assumptions, or both. As a result, the estimate of the contribution these emissions make to the global methane inventory could be inaccurate. For this reason the assertion that global warming could be reduced by replacing coal and oil fuels with natural gas could not be defended. A recently completed, multi year study conducted by the U.S. Environmental Protection Agency’s Office of Research and Development and the Gas Research Institute had the objective of determining methane emissions from the U.S. gas industry with an accuracy of t 0.5% of production. The study concluded that, in the 1992 base year, methane emissions from the industry were 314 t 105 Bscf or 6.04 t 2.01 Tg (all conversions to international units are made at 15.56 °C and 101.325 kPa)” David A. Kirchgessner, Robert A. Lott, R. Michael Cowgill, Matthew R. Harrison and Theresa M. Shires, Chemosphere, Volume 35, Issue 6, September 1997, Pages 1365-1390, doi:10.1016/S0045-6535(97)00236-1. [Full text]

Methane emission measurements in urban areas in Eastern Germany – Shorter et al. (1996) “We have investigated methane emissions from urban sources in the former East Germany using innovative measurement techniques including a mobile real-time methane instrument and tracer release experiments. Anthropogenic and biogenic sources were studied with the emphasis on methane emissions from gas system sources, including urban distribution facilities and a production plant. Methane fluxes from pressure regulating stations ranged from 0.006 to 24. l/min. Emissions from diffuse sources in urban areas were also measured with concentration maps and whole city flux experiments. The area fluxes of the two towns studied were 0.37 and 1.9 g/m2/s. The emissions from individual gas system stations and total town emissions of this study are comparable to results of similar sites examined in the United States.” Joanne H. Shorter, J. Barry Mcmanus, Charles E. Kolb, Eugene J. Allwine, Brian K. Lamb, Byard W. Mosher, Robert C. Harriss, Uwe Partchatka, Horst Fischer and Geoffrey W. Harris, et al., Journal of Atmospheric Chemistry, Volume 24, Number 2, 121-140, DOI: 10.1007/BF00162407. [Full text]

Indirect chemical effects of methane on climate warming – Lelieveld & Crutzen (1992) “METHANE concentrations in the atmosphere have increased from about 0.75 to 1.7 p.p.m.v. since pre-industrial times1,2. The current annual rate of increase of about 0.8% yr-1 (ref. 2) is due to increases in industrial and agricultural emissions. This increase in atmospheric methane concentrations not only influences the climate directly, but also indirectly through chemical reactions. Here we show that the climate effects of methane’s atmospheric chemistry have previously been overestimated, notably by the Inter-governmental Panel on Climate Change (IPCC)3, largely owing to neglect of the height dependence of certain atmospheric radiative processes. Using available estimates of fossil-fuel-related leaks of methane, our results show that switching from coal and oil to natural gas as an energy source would reduce climate warming. A significant fraction of methane emissions cannot, however, be accounted for by known sources; should leakages from gas production and distribution be underestimated for some countries, then it might be unwise to switch to using natural gas.” Jos Lelieveld & Paul J. Crutzen, Nature 355, 339 – 342 (23 January 1992); doi:10.1038/355339a0.

Gas leakage in United Kingdom – Wallis (1992) No abstract. M. K. Wallis, Nature 359, 355 (01 October 1992); doi:10.1038/359355a0.

Leaking gas in the greenhouse – Wallis (1991) “Greenhouse gas emissions by the United Kingdom could be significantly reduced by replacement of old and leaking gas mains. Such a programme could even be cost-effective for the utility concerned.” Max K. Wallis, Nature 354, 428 (12 December 1991); doi:10.1038/354428a0.

Leaky answer to greenhouse gas? – Wallis (1990) No abstract. Max K. Wallis, Nature 344, 25 – 26 (01 March 1990).

A study of leakage from the UK natural gas distribution system – Mitchell et al. (1990) “This paper studies leakage from the UK natural gas distribution system. British Gas maintains that the leakage rate is around 1% of supply. This paper estimates a Low, Medium and High Case leakage rate of 1.9%, 5.3% and 10.8% respectively. The authors are confident that the leakage rate is above 1.9% and consider it more likely that the leakage rate is between the Medium and High Case. This investigation has been very cautious in that only leakage from the low pressure, medium pressure and service pipelines has been calculated. No estimates of leakage from the broader supply system have been included because of lack of verifiable information. The implications of these leakage rates for energy policy are considered.” Catherine Mitchell, Jim Sweet and Tim Jackson, Energy Policy, Volume 18, Issue 9, November 1990, Pages 809-818, doi:10.1016/0301-4215(90)90060-H.

Methane leakage from natural gas – Okken (1990) “Carbon dioxide (CO₂) emissions from fossil fuels are a major cause of the global greenhouse effect. Fuel switching is one of the options to reduce emissions. However, CO₂ is not the only greenhouse gas. This paper addresses the question whether greenhouse effect mitigating strategies such as fuel switching would change if methane (CH₄) is taken into account, by calculating the global warming from current energy related CH₄ and CO (carbon monoxide) emissions as ‘CO₂ equivalents’.” P. A. Okken, Energy Policy, Volume 18, Issue 2, March 1990, Pages 202-204.