Global methane emissions from natural gas networks

Global methane emissions from natural gas networks | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Global methane emissions from natural gas networks Geoffroy Hureau, Armelle Lecarpentier, Sylvain Serbutoviez, Jean Kaniewicz, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3762945/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Given the significant global warming power and short atmospheric lifetime of methane, one of the most effective mitigation strategies for limiting global warming over the short term is to target the anthropogenic sources of methane and rapidly reduce their emissions. The unaccounted for gas phenomenon in natural gas transmission and distribution networks reflects an imbalance between what enters the gas network and what leaves it. The aim of this paper is to investigate the possibility of leaks along these gas networks, and to determine whether this leads to methane emissions, since natural gas is mainly composed of methane. First, flow data measured along gas networks are collected and used to assess unaccounted for gas by country. A global average value of 1.7% is observed, but with significant disparities between regions ranging from 0.01% to 15%. Second, unaccounted for gas values permit to assess the quantities of methane released into the atmosphere by gas networks. In total, 18 Mt of methane were emitted in 2021. The main producing countries present high unaccounted for gas volumes and methane emissions, which can be explained by the age of their gas networks. Conversely, networks in more recent markets or advanced countries have fewer leaks, leading to more moderate methane emissions. This shows than methane emissions can be reduced in well-maintained networks. The accounting method developed in this article would make it possible to verify the emissions reductions announced for gas networks in the future if repeated over time. methane emissions gas network greenhouse effect global warming Figures Figure 1 Figure 2 Figure 3 1. Introduction Many human activities (agriculture, burning fossil fuels, cutting down forests, raising livestock, etc .) add huge quantities of greenhouse gases to those naturally present in the atmosphere, increasing the greenhouse effect and global warming. Carbon dioxide (CO 2 ) is the most emitted anthropogenic greenhouse gas: it is responsible for more than half of global warming. Methane (CH 4 ) comes next with a contribution of 20-30% (Intergovernmental Panel on Climate Change - IPCC 2021; International Energy Agency - IEA 2022). Nitrous oxide (N 2 O) and fluorinated gases (F-gases) follow to a lesser extent. Two properties characterize the impact of greenhouse gases on climate: the time they remain in the atmosphere and their ability to absorb energy. Methane has a much shorter lifespan in the atmosphere than CO 2 (around 12 years versus centuries for CO 2 ). However, it is more potent as it absorbs much more energy while in the atmosphere: its global warming potential (GWP) is about 30 times that of CO 2 over 100 years, or 80 times over 20 years (IPCC 2021). For both reasons, removing methane from the atmosphere should reduce temperatures faster than removing CO 2 (Saunois et al. 2020; Shindell et al. 2020). It is therefore a key factor in achieving the 2050 climate objectives. Mitigating methane emissions could contribute to a temperature reduction of around 0.1°C by 2050 (Cain et al. 2022; Smith et al. 2020). In addition, this would have a positive impact on human health as methane is a precursor of tropospheric ozone (O 3 ), and thus plays a part in air pollution worldwide (Mar et al. 2022). The primary source of anthropogenic methane emissions is agriculture (142 Mt) closely followed by the energy sector (133 Mt) with around 40 Mt for coal, the same for oil and also for gas, and waste landfills (71 Mt) (IEA 2023; Ciais et al. 2013). Clearly, efforts need to be made in all sectors. However, it may prove simpler and more effective in the short term to act on the energy lever. In the short term, oil and gas industry offers the greatest short-term opportunity to lower methane emissions. Indeed, according to the IEA, global methane emissions from the oil and gas sector could be reduced by 75% with existing technologies at low cost, by investing nearly $100 billion between now and 2030. Under the Global Methane Pledge launched at the 26th Conference of the Parties (COP26) in 2021, the European Union (EU) together with 149 countries committed to reducing global anthropogenic methane emissions by 30% in 2030 compared to 2020 levels. Then, in November 2023, the EU reached a provisional agreement with the aim of reducing energy sector methane emissions in Europe and also in our global supply chains. The text also introduces global monitoring tools to ensure transparency of methane emissions from oil, gas, and coal imports into the EU. The natural gas supply chain can be split into several segments, with upstream and gas transportation among them (Saint-Vincent and Pekney 2020). The emissions in the upstream segment result from production, gathering and processing in all onshore and offshore oil and gas facilities. Gas transportation generates emissions because of the transport and distribution of gas by pipeline or in the form of liquefied natural gas (LNG) and regasification. Other sources of emissions can be also accounted for in refining, oil transport and oil and gas consumption. In the special case of the natural gas value chain, methane is emitted in three ways: through fugitive emissions, incomplete flaring, and venting. Fugitive methane emissions are caused by unintentional leaks, such as a faulty seal or leaky valve. Methane emissions from flaring can occur when natural gas is burned instead of being sold or vented because it cannot be used or recovered economically. Most of the natural gas is then converted into CO 2 and water, but some may not be flared and is released into the atmosphere as methane. Last, vented methane emissions result from intentional releases, often for safety reasons, due to the design of the facility or equipment ( e.g ., pneumatic controllers) or operational requirements ( e.g ., venting a pipeline for inspection and maintenance). This paper provides estimates of the losses along natural gas networks. The first section is dedicated to the quantification of “Unaccounted for gas” (UFG) all over the world. UFG usually refers to the difference between the measured quantity of gas entering the gas network and the measured quantity of gas flowing out of the same network (Botev and Johnson 2020). The reasons for gas loss and unaccountability are manifold: leaks, theft, inaccurate metering, and gas used to operate network equipment that is known as “own use gas” (it is not accounted for). Then, the second section aims to deduce the methane released by each country into the atmosphere along gas networks. The value of quantifying UFG is to help assess methane emissions. Since natural gas is a mixture of different hydrocarbons, of which methane is the main constituent (usually 87-97%), a non-zero UFG is an indicator of potentially high methane emissions. In other words, methane emissions are not the prerogative of distant oil and gas-producing countries; they can be found just around the corner (Weller et al. 2020). 2. Quantification of unaccounted for gas Various techniques can be used to estimate methane emissions. For instance, methane concentrations can be measured locally in ambient air with gas analyzers (e.g., Maazallahi et al. 2023; MacMullin and Rongère 2023; Kumar et al. 2021) or regionally in the atmosphere using satellite, drone, and other imaged-based techniques (Pandey et al. 2023; Duren et al. 2019). Another strategy can be followed in the very specific case of natural gas network utilities. These consist of both transmission networks and distribution networks. Immediately after production at the field, the gas produced is purified and prepared for pumping. Pumped by compressor stations to high pressures, it enters the transmission network designed to transport substantial volumes of gas across extensive distances. Gas flows into the high-pressure pipeline network via a number of entry sites, delivered either via pipelines from offshore or onshore gas fields, or via international transit pipelines and, in some cases, LNG imports. At all entry points, the gas must be measured with great accuracy for fiscal reasons. At some point, the gas leaves the gas transmission networks and enters the distribution networks. The interface between both systems requires accurate gas metering. The distribution networks, which are adjusted to gradually reduce pressure, then transport gas from transmission networks to end consumers. Again, gas metering is essential for billing purposes. The imbalance between gas entering the network and gas exiting is unaccounted for gas (UFG). In what follows, the aim is to estimate UFG volumes in the world's networks, based on data compiled in a database by the CEDIGAZ association. This international non-profit association was founded in 1961 and is widely recognized as a reliable source of information by gas analysts. Over the years, it has collected a large amount of data from natural gas network operators and created a database covering more than 120 countries. We define UFG as (CEDIGAZ 2023): UFG = Leakage + Own use gas + Theft “Leakage” refers to gas losses due to daily operations, venting, accidentally damaged pipes or metering errors. Leaks can occur on various devices such as compressors. “Own use gas” (OUG) is the gas used by the network utility to deliver the gas it transports to the customers. It is then used to support network operations, in the form of preheating and fuel for compressor stations. For example, gas must be heated prior to pressure reduction, through the preheating process, to mitigate the negative effect of a temperature drop on equipment during pressure reduction. Besides, “Theft” represents the gas withdrawn from the network by unauthorized third parties. Leaks from high-pressure gas transmission pipelines are generally very rare and very low, as the high-pressure gas transmission network consists of welded steel high-pressure pipelines, which do not normally leak. Under normal circumstances, the percentage of UFG associated with gas transport systems is therefore quite low, typically less than 0.5% of total flows. On the other hand, UFG levels in distribution networks can be much higher, usually in the order of 1 to 5%. The evaluation of UFG volumes calls for data on UFG percentages, gas demand and pipeline network sizes. Demand data were extracted from the 2021 CEDIGAZ database. Pipeline lengths were sourced from transmission system operators (TSO) or the Central Intelligence Agency world factbook. The UFG percentages used at national level, defined as the ratios of UFG volumes to national gas demands, were those provided by national regulators, governments or TSOs, where available and reliable. Otherwise, there were two possible cases. First, UFG percentages were calculated as a weighted average of the UFG percentages reported by individual TSOs and distribution system operators (DSOs). Second, in the absence of any data, they were estimated on the basis of the age and physical characteristics of the pipeline network and the number of customers. The CEDIGAZ database lists 108 countries with gas demand above 0, ranging from 0.05 billion m 3 to 868 billion m 3 (USA). This list has been reduced to 82 countries based on the following criteria: annual gas demand greater than 1 billion m 3 ; existing gas transmission/distribution networks; data of sufficient quality. Table 1. UFG volume, mean UFG percentage, and resulting methane emissions per world regions in 2021 (CEDIGAZ 2023). Region Mean UFG (%) Total UFG (bcm) Resulting methane emissions (Mt) Asia Oceania 2.04 11.77 3.02 Middle East 1.64 9.14 2.85 Africa 1.35 2.29 0.72 Central & South America 1.32 1.72 0.54 Europe 0.52 2.25 0.70 North America 1.88 19.87 6.20 CIS and Ukraine 1.95 12.68 3.95 World 1.67 59.72 17.98 UFG percentages by countries are displayed in Figure 1. They range from 0.01% to 15%, with an average value of 1.7%. The countries with the highest UFG percentages are Myanmar (15%), Syria (13.8%), Pakistan (11.7%), South Africa (8%) and Australia (4%). However, UFG percentages must be set against UFG volumes, which depend on the size and maturity of the natural gas market. For example, Myanmar's UFG percentage and volume are 15% and 0.615 billion m 3 respectively, compared with 2.10% and 17.997 billion m 3 for the USA, and 0.75% and 0.325 billion m 3 for France. A 0.1 decrease in the percentage of UFG can result in a significant drop in UFG volume, depending on the country. At the regional level (Table 1), the largest UFG percentages are in Asia-Oceania (2.04%) and the Commonwealth of Independent States (CIS) (1.95%), followed by North America (1.88%), the Middle East (1.64%), Africa (1.35%), Central and South America (1.32%), and Europe (0.52%). The UFG percentages for CIS and North America are above the world mean. They are also the two leading producers of natural gas with the oldest and largest natural gas networks. 3. Resulting methane emissions Non-zero volumes of UFG mean that some gas is lost along the transmission and distribution networks, and that these losses result, at least in part, in methane emissions into the atmosphere. However, it is quite difficult to estimate the amount of methane emitted. The contribution of leaks is clearly direct. As for the stolen volumes, some of them also lead to methane emissions, as non-standard connections to the system are highly susceptible to leakage. Most of the time, network operators do not know with any real certainty the actual proportions of OUG associated with leaks and theft so that these figures can only be estimated. In some cases, these estimates are to be linked to concerns of the gas network operator. For example, estimates of high levels of leakage could be used to justify demands for further investment in infrastructure, while estimates of high levels of theft could be used to conceal poor operation and maintenance practices. Consequently, since the relative proportions of leakage and theft in the UFG volumes are unknown, the resulting methane emissions are assumed to correspond to 50% of the UFG. This is obviously a crude approximation, but it reflects the poor quality of the data displayed on the UFG. We also assume that natural gas contains 95% methane. Given these hypotheses and the data available, we estimate that the total amount of methane emitted along natural gas transmission and distribution networks in the world was around 18 Mt in 2021 (Table 1). These figures are comparable to those of the IEA (2023), which states that the energy sector is responsible for almost 135 Mt of methane emissions, including 12 Mt of fugitive emissions from pipelines and LNG facilities. Besides, O'Rourke et al. (2021) report 11 Mt of methane emissions from the downstream oil and gas sector and Cooper et al. (2021) 26.4 Mt for the largest natural gas supply chains. Our calculations therefore lead to estimates of the same order. Focusing on mitigating these 18 Mt of emissions would make a significant contribution to the fight against global warming. Shirizadeh et al. (2023) showed that adopting the best available methane abatement technologies can lead to an 80% reduction in methane leakage along the natural gas value chain, capping the additional environmental burden to 8% of direct CO 2 emissions (compared with 35% today). As shown in Figure 2, the greater the demand for gas, the greater the methane emissions. However, the data are widely dispersed around the regression line. This is due to UFG percentage effects: countries with a high UFG percentage are above the line, the others below. The results by countries are mapped in Figure 3. They point to the following top 10 countries: USA (5.62 Mt), Russia (3.06 Mt), Pakistan (1.76 Mt), Iran (1.45 Mt), Australia (0.65 Mt), Saudi Arabia (0.59 Mt), Argentina (0.49 Mt), Turkey (0.45 Mt), Canada (0.43 Mt), and Qatar (0.35 Mt). These top ten countries include major gas producers, consumers and transit countries. The largest producing countries (United States, Russia, Canada, Iran) are the most mature, as gas networks were first built in the vicinity of major gas fields. They therefore have the oldest infrastructure networks. The main producing countries are among the top 10 emitters, with the exception of China and Norway, but these two countries have not been analyzed here. China, the world's leading methane emitter due in part to coal mining, also records a significant amount of fugitive and vented methane emissions from downstream gas (0.85 Mt from pipelines and LNG facilities, according to the IEA's Methane Tracker database 2023). Norway is a special case, as its production fields are export-oriented, while the volume of natural gas transported for domestic use is marginal. On the other hand, more recent markets and "modern" importing economies also have very dense but better-maintained infrastructure networks, and therefore lower emissions. This is generally the case in Europe with Italy (0.16 Mt), France (0.10 Mt), United Kingdom (0.08 Mt) or Germany (0.02 Mt) and in the advanced Asian countries with South Korea (0.03 Mt), Japan (0.01 Mt) or Taiwan (0.0008 Mt). For the former, the results can be attributed to good practices. For the latter, it should be remembered that they mainly import LNG, which means that their networks are less dense. This choice can also be explained, particularly in the case of Japan, by the high seismic risk. 4. Conclusion With growing environmental and financial concerns about potential levels of methane emissions, the issue of methane emissions in general and UFG in particular is increasingly on the agenda. UFGs are associated with leaks, theft, inaccurate metering, and operations along natural gas transmission and distribution networks. Reducing them would not only reduce financial losses, but also, and above all, help meet the 2050 climate objectives. The persistence of methane in the atmosphere is much lower than that of CO 2 : a decrease in the quantities of methane emitted would have a rapid beneficial effect. On the basis of various gas network data, we first estimated the UFG and then calculated the associated methane emissions. The average UFG for the world is 1.7%, but with significant disparities between regions, ranging from 0.01% to 15%. The resulting methane emissions are provided by country and correspond to 18 Mt worldwide. The results point to two types of country. On the one hand, the main producing countries are characterized by high UFG volumes and high methane emissions. The reason for this is the age of their gas networks. By comparison, networks in more recent markets or advanced countries have fewer leaks, leading to more moderate methane emissions. This suggests that it is possible to cut methane emissions. The complete elimination of gas leaks is impossible, but the implementation of robust maintenance and inspection strategies for pipelines and equipment can help reduce them. An additional advantage of the counting methodology developed in this paper is that it can be repeated every year enabling future emission reductions to be verified. Finally, regulations encouraging the disclosure of shrinkage and OUG data will be a step in the right direction. These practices will make operators publicly accountable. Greater transparency of UFG data on the part of the stakeholders concerned is necessary to better identify actions to be taken to curb methane emissions. In addition, it will prevent operators from potentially passing on the cost of UFG to the end consumer. References Botev L, Johnson P (2020) Applications of statistical process control in the management of unaccounted for gas. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3762945","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":269178130,"identity":"00f6fdcc-21e2-4546-8e0c-74213cbec3d2","order_by":0,"name":"Geoffroy Hureau","email":"","orcid":"","institution":"IFPEN: IFP Energies nouvelles","correspondingAuthor":false,"prefix":"","firstName":"Geoffroy","middleName":"","lastName":"Hureau","suffix":""},{"id":269178131,"identity":"9332819e-adbc-4659-9513-a0d146c64ca4","order_by":1,"name":"Armelle Lecarpentier","email":"","orcid":"","institution":"IFPEN: IFP Energies nouvelles","correspondingAuthor":false,"prefix":"","firstName":"Armelle","middleName":"","lastName":"Lecarpentier","suffix":""},{"id":269178132,"identity":"4ea1fe75-ab96-43ee-8154-0ec0da6f7f0a","order_by":2,"name":"Sylvain Serbutoviez","email":"","orcid":"","institution":"IFPEN: IFP Energies nouvelles","correspondingAuthor":false,"prefix":"","firstName":"Sylvain","middleName":"","lastName":"Serbutoviez","suffix":""},{"id":269178133,"identity":"8c30ad53-cccc-42b2-a36d-bcc3bd251c93","order_by":3,"name":"Jean Kaniewicz","email":"","orcid":"","institution":"IFPEN: IFP Energies nouvelles","correspondingAuthor":false,"prefix":"","firstName":"Jean","middleName":"","lastName":"Kaniewicz","suffix":""},{"id":269178134,"identity":"1ddfcf77-6386-4696-a69f-51900d45cc55","order_by":4,"name":"Mike Madden","email":"","orcid":"","institution":"MJMEnergy","correspondingAuthor":false,"prefix":"","firstName":"Mike","middleName":"","lastName":"Madden","suffix":""},{"id":269178135,"identity":"d9508bc2-da6d-4cc8-9b48-e0248953ce42","order_by":5,"name":"Chris Brooks","email":"","orcid":"","institution":"MJMEnergy","correspondingAuthor":false,"prefix":"","firstName":"Chris","middleName":"","lastName":"Brooks","suffix":""},{"id":269178136,"identity":"f0a246e6-1296-44e5-adeb-fe49a77017a8","order_by":6,"name":"Aileen Robertson","email":"","orcid":"","institution":"MJMEnergy","correspondingAuthor":false,"prefix":"","firstName":"Aileen","middleName":"","lastName":"Robertson","suffix":""},{"id":269178137,"identity":"a85dc97b-6a14-4594-a1d3-6718787b0469","order_by":7,"name":"Colin Harrison","email":"","orcid":"","institution":"MJMEnergy","correspondingAuthor":false,"prefix":"","firstName":"Colin","middleName":"","lastName":"Harrison","suffix":""},{"id":269178138,"identity":"c72bf38a-42b1-4381-9200-a0664f2a0dae","order_by":8,"name":"Chris Langston","email":"","orcid":"","institution":"MJMEnergy","correspondingAuthor":false,"prefix":"","firstName":"Chris","middleName":"","lastName":"Langston","suffix":""},{"id":269178139,"identity":"b43c9606-ba3b-4072-82e9-e0381c561ed7","order_by":9,"name":"mickaele le ravalec","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABKklEQVRIie2RMUvDQBSA3/HgsqRmPUGaXyAkHLQKEf/KhUImB8cMhV4JnIvo6s/ITzg5iEvBtUOHSKFTh7pIHVpMiiiUpOgmct8N9+7e+3jvOACL5S+C1QI4A3A+L44ASCmiOiTlAYXBbquhVRiIZJcLWvvsK5TBAeX0BufBOmVdQNSYDo1PnWyRlmLW7QPSVYPSM5THtxPGq7wgk8KEyi16UyEW/FwiPjQqLuqOYrFEt/8uaUIUu6LTeG3iXHumabBaedxs2UiityJym1wqf0mvhTCjXCO2KYOOZALQBTJWUayYS6FSRNCqUM5PChYqpAEZ30UD5SacVW8Jc9OiPJv58XIY+Z6TlUS+sYt7x7y8rsXMD56yRuULunfW3z/1U/Qv6y0Wi+Uf8wEgGVc40NK/tQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0009-0003-0927-7022","institution":"IFPEN: IFP Energies nouvelles","correspondingAuthor":true,"prefix":"","firstName":"mickaele","middleName":"le","lastName":"ravalec","suffix":""}],"badges":[],"createdAt":"2023-12-16 10:53:01","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3762945/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3762945/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":50308912,"identity":"5d43d83f-7608-4fcc-98a0-677790bf803d","added_by":"auto","created_at":"2024-01-29 14:02:35","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":115778,"visible":true,"origin":"","legend":"\u003cp\u003eUFG percentages by country\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3762945/v1/bc9e262e3367634fce9592d8.png"},{"id":50308521,"identity":"31c54da0-39c4-44f1-a9ad-ecb81f12575b","added_by":"auto","created_at":"2024-01-29 13:54:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":83444,"visible":true,"origin":"","legend":"\u003cp\u003eVolume of methane emitted against gas demand. Bubble’s sizes and colors are determined by UFG percentages.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3762945/v1/e59ab29534789dc70ba4c4a8.png"},{"id":50308911,"identity":"f3ff54b3-581b-401a-9edb-366bdaac4f2f","added_by":"auto","created_at":"2024-01-29 14:02:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":114205,"visible":true,"origin":"","legend":"\u003cp\u003eEstimated methane emissions due to UFGs by country in 2021.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3762945/v1/209266f0690f6f16555d91c8.png"},{"id":58424617,"identity":"e4635205-3d38-4d9d-a694-dd9234b26dd7","added_by":"auto","created_at":"2024-06-15 17:58:15","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":582465,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3762945/v1/294c7925-100c-4707-b8bd-8469a2b99808.pdf"}],"financialInterests":"","formattedTitle":"Global methane emissions from natural gas networks","fulltext":[{"header":"1.\tIntroduction","content":"\u003cp\u003eMany human activities (agriculture, burning fossil fuels, cutting down forests, raising livestock, \u003cem\u003eetc\u003c/em\u003e.) add huge quantities of greenhouse gases to those naturally present in the atmosphere, increasing the greenhouse effect and global warming. Carbon dioxide (CO\u003csub\u003e2\u003c/sub\u003e) is the most emitted anthropogenic greenhouse gas: it is responsible for more than half of global warming. Methane (CH\u003csub\u003e4\u003c/sub\u003e) comes next with a contribution of 20-30% (Intergovernmental Panel on Climate Change - IPCC 2021; International Energy Agency - IEA 2022). Nitrous oxide (N\u003csub\u003e2\u003c/sub\u003eO) and fluorinated gases (F-gases) follow to a lesser extent. Two properties characterize the impact of greenhouse gases on climate: the time they remain in the atmosphere and their ability to absorb energy. Methane has a much shorter lifespan in the atmosphere than CO\u003csub\u003e2\u003c/sub\u003e (around 12 years versus centuries for CO\u003csub\u003e2\u003c/sub\u003e). However, it is more potent as it absorbs much more energy while in the atmosphere: its global warming potential (GWP) is about 30 times that of CO\u003csub\u003e2\u003c/sub\u003e over 100 years, or 80 times over 20 years (IPCC 2021). For both reasons, removing methane from the atmosphere should reduce temperatures faster than removing CO\u003csub\u003e2\u003c/sub\u003e (Saunois et al. 2020; Shindell et al. 2020). It is therefore a key factor in achieving the 2050 climate objectives. Mitigating methane emissions could contribute to a temperature reduction of around 0.1\u0026deg;C by 2050 (Cain et al. 2022; Smith et al. 2020). In addition, this would have a positive impact on human health as methane is a precursor of tropospheric ozone (O\u003csub\u003e3\u003c/sub\u003e), and thus plays a part in air pollution worldwide (Mar et al. 2022).\u003c/p\u003e\n\u003cp\u003eThe primary source of anthropogenic methane emissions is\u0026nbsp;agriculture (142 Mt) closely followed by the energy sector (133 Mt) with around 40 Mt for coal, the same for oil and also for gas, and waste landfills (71 Mt) (IEA 2023; Ciais et al. 2013). Clearly, efforts need to be made in all sectors. However, it may prove simpler and more effective in the short term to act on the energy lever. In the short term, oil and gas industry offers the greatest short-term opportunity to lower methane emissions. Indeed, according to the IEA, global methane emissions from the oil and gas sector could be reduced by 75% with existing technologies at low cost, by investing nearly $100 billion between now and 2030.\u003c/p\u003e\n\u003cp\u003eUnder the\u0026nbsp;Global Methane Pledge launched at the 26th Conference of the Parties (COP26) in 2021, the European Union (EU) together with 149 countries committed to reducing global anthropogenic methane emissions by 30% in 2030 compared to 2020 levels. Then, in November 2023, the EU reached a provisional agreement with the aim of reducing energy sector methane emissions in Europe and also in our global supply chains. The text also introduces global monitoring tools to ensure transparency of methane emissions from oil, gas, and coal imports into the EU.\u003c/p\u003e\n\u003cp\u003eThe natural gas supply chain can be split into several segments, with upstream and gas transportation among them (Saint-Vincent and Pekney 2020). The emissions in the upstream segment result from production, gathering and processing in all onshore and offshore oil and gas facilities. Gas transportation generates emissions because of the transport and distribution of gas by pipeline or in the form of liquefied natural gas (LNG) and regasification. Other sources of emissions can be also accounted for in refining, oil transport and oil and gas consumption. In the special case of the natural gas value chain, methane is emitted in three ways: through fugitive emissions, incomplete flaring, and venting. Fugitive methane emissions are caused by unintentional leaks, such as a faulty seal or leaky valve. Methane emissions from flaring can occur when natural gas is burned instead of being sold or vented because it cannot be used or recovered economically. Most of the natural gas is then converted into CO\u003csub\u003e2\u003c/sub\u003e and water, but some may not be flared and is released into the atmosphere as methane. Last, vented methane emissions result from intentional releases, often for safety reasons, due to the design of the facility or equipment (\u003cem\u003ee.g\u003c/em\u003e., pneumatic controllers) or operational requirements (\u003cem\u003ee.g\u003c/em\u003e., venting a pipeline for inspection and maintenance).\u003c/p\u003e\n\u003cp\u003eThis paper provides estimates of the losses along natural gas networks. The first section is dedicated to the quantification of \u0026ldquo;Unaccounted for gas\u0026rdquo; (UFG) all over the world. UFG usually refers to the difference between the measured quantity of gas entering the gas network and the measured quantity of gas flowing out of the same network (Botev and Johnson 2020). The reasons for gas loss and unaccountability are manifold: leaks, theft, inaccurate metering, and gas used to operate network equipment that is known as \u0026ldquo;own use gas\u0026rdquo; (it is not accounted for). Then, the second section aims to deduce the methane released by each country into the atmosphere along gas networks. The value of quantifying UFG is to help assess methane emissions. Since natural gas is a mixture of different hydrocarbons, of which methane is the main constituent (usually 87-97%), a non-zero UFG is an indicator of potentially high methane emissions. In other words, methane emissions are not the prerogative of distant oil and gas-producing countries; they can be found just around the corner (Weller et al. 2020).\u0026nbsp;\u003c/p\u003e"},{"header":"2.\tQuantification of unaccounted for gas ","content":"\u003cp\u003eVarious techniques can be used to estimate methane emissions. For instance, methane concentrations can be measured locally in ambient air with gas analyzers (e.g., Maazallahi et al. 2023; MacMullin and Rong\u0026egrave;re 2023; Kumar et al. 2021) or regionally in the atmosphere using satellite, drone, and other imaged-based techniques (Pandey et al. 2023; Duren et al. 2019). Another strategy can be followed in the very specific case of natural gas network utilities. These consist of both transmission networks and distribution networks. Immediately after production at the field, the gas produced is purified and prepared for pumping. Pumped by compressor stations to high pressures, it enters the transmission network designed to transport substantial volumes of gas across extensive distances. Gas flows into the high-pressure pipeline network via a number of entry sites, delivered either via pipelines from offshore or onshore gas fields, or via international transit pipelines and, in some cases, LNG imports. At all entry points, the gas must be measured with great accuracy for fiscal reasons. At some point, the gas leaves the gas transmission networks and enters the distribution networks. The interface between both systems requires accurate gas metering. The distribution networks, which are adjusted to gradually reduce pressure, then transport gas from transmission networks to end consumers. Again, gas metering is essential for billing purposes. The imbalance between gas entering the network and gas exiting is unaccounted for gas (UFG).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn what follows, the aim is to estimate UFG volumes in the world\u0026apos;s networks, based on data compiled in a database by the CEDIGAZ association. This international non-profit association was founded in 1961 and is widely recognized as a reliable source of information by gas analysts. Over the years, it has collected a large amount of data from natural gas network operators and created a database covering more than 120 countries.\u003c/p\u003e\n\u003cp\u003eWe define UFG as (CEDIGAZ 2023):\u003c/p\u003e\n\u003cp\u003eUFG = Leakage + Own use gas + Theft\u003c/p\u003e\n\u003cp\u003e\u0026ldquo;Leakage\u0026rdquo; refers to gas losses due to daily operations, venting, accidentally damaged pipes or metering errors. Leaks can occur on various devices such as compressors. \u0026ldquo;Own use gas\u0026rdquo; (OUG) is the gas used by the network utility to deliver the gas it transports to the customers. It is then used to support network operations, in the form of preheating and fuel for compressor stations. For example, gas must be heated prior to pressure reduction, through the preheating process, to mitigate the negative effect of a temperature drop on equipment during pressure reduction. Besides, \u0026ldquo;Theft\u0026rdquo; represents the gas withdrawn from the network by unauthorized third parties.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLeaks from high-pressure gas transmission pipelines are generally very rare and very low, as the high-pressure gas transmission network consists of welded steel high-pressure pipelines, which do not normally leak. Under normal circumstances, the percentage of UFG associated with gas transport systems is therefore quite low, typically less than 0.5% of total flows. On the other hand, UFG levels in distribution networks can be much higher, usually in the order of 1 to 5%.\u003c/p\u003e\n\u003cp\u003eThe evaluation of UFG volumes calls for data on UFG percentages, gas demand and pipeline network sizes. Demand data were extracted from the 2021 CEDIGAZ database. Pipeline lengths were sourced from transmission system operators (TSO) or the Central Intelligence Agency world factbook. The UFG percentages used at national level, defined as the ratios of UFG volumes to national gas demands, were those provided by national regulators, governments or TSOs, where available and reliable. Otherwise, there were two possible cases. First, UFG percentages were calculated as a weighted average of the UFG percentages reported by individual TSOs and distribution system operators (DSOs). Second, in the absence of any data, they were estimated on the basis of the age and physical characteristics of the pipeline network and the number of customers. The CEDIGAZ database lists 108 countries with gas demand above 0, ranging from 0.05 billion m\u003csup\u003e3\u003c/sup\u003e to 868 billion m\u003csup\u003e3\u003c/sup\u003e (USA). This list has been reduced to 82 countries based on the following criteria: annual gas demand greater than 1 billion m\u003csup\u003e3\u003c/sup\u003e; existing gas transmission/distribution networks; data of sufficient quality.\u003c/p\u003e\n\u003cp\u003eTable 1. UFG volume, mean UFG percentage, and resulting methane emissions per world regions in 2021 (CEDIGAZ 2023).\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"491\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003e\u003cstrong\u003eRegion\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\"\u003e\n \u003cp\u003e\u003cstrong\u003eMean UFG (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal UFG (bcm)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\"\u003e\n \u003cp\u003e\u003cstrong\u003eResulting methane emissions (Mt)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eAsia Oceania\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e11.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e3.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eMiddle East\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e9.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eAfrica\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.72\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eCentral \u0026amp; South America\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.54\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eEurope\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e2.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eNorth America\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e19.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e6.20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003eCIS and Ukraine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e1.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e12.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e3.95\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.586558044806516%\"\u003e\n \u003cp\u003e\u003cstrong\u003eWorld\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.34826883910387%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.67\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.181262729124235%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e59.72\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"26.883910386965375%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e17.98\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eUFG percentages by countries are displayed in Figure 1. They range from 0.01% to 15%, with an average value of 1.7%. The countries with the highest UFG percentages are Myanmar (15%), Syria (13.8%), Pakistan (11.7%), South Africa (8%) and Australia (4%). However, UFG percentages must be set against UFG volumes, which depend on the size and maturity of the natural gas market. For example, Myanmar\u0026apos;s UFG percentage and volume are 15% and 0.615 billion m\u003csup\u003e3\u003c/sup\u003e respectively, compared with 2.10% and 17.997 billion m\u003csup\u003e3\u003c/sup\u003e for the USA, and 0.75% and 0.325 billion m\u003csup\u003e3\u003c/sup\u003e for France. A 0.1 decrease in the percentage of UFG can result in a significant drop in UFG volume, depending on the country.\u003c/p\u003e\n\u003cp\u003eAt the regional level (Table 1), the largest UFG percentages are in Asia-Oceania (2.04%) and the Commonwealth of Independent States (CIS) (1.95%), followed by North America (1.88%), the Middle East (1.64%), Africa (1.35%), Central and South America (1.32%), and Europe (0.52%). The UFG percentages for CIS and North America are above the world mean. They are also the two leading producers of natural gas with the oldest and largest natural gas networks.\u003c/p\u003e"},{"header":"3.\tResulting methane emissions","content":"\u003cp\u003eNon-zero volumes of UFG mean that some gas is lost along the transmission and distribution networks, and that these losses result, at least in part, in methane emissions into the atmosphere. However, it is quite difficult to estimate the amount of methane emitted. The contribution of leaks is clearly direct. As for the stolen volumes, some of them also lead to methane emissions, as non-standard connections to the system are highly susceptible to leakage. Most of the time, network operators do not know with any real certainty the actual proportions of OUG associated with leaks and theft so that these figures can only be estimated. In some cases, these estimates are to be linked to concerns of the gas network operator. For example, estimates of high levels of leakage could be used to justify demands for further investment in infrastructure, while estimates of high levels of theft could be used to conceal poor operation and maintenance practices. Consequently, since the relative proportions of leakage and theft in the UFG volumes are unknown, the resulting methane emissions are assumed to correspond to 50% of the UFG. This is obviously a crude approximation, but it reflects the poor quality of the data displayed on the UFG. We also assume that natural gas contains 95% methane.\u003c/p\u003e\n\u003cp\u003eGiven these hypotheses and the data available, we estimate that the total amount of methane emitted along natural gas transmission and distribution networks in the world was around 18 Mt in 2021 (Table 1). These figures are comparable to those of the IEA (2023), which states that the energy sector is responsible for almost 135 Mt of methane emissions, including 12 Mt of fugitive emissions from pipelines and LNG facilities. Besides, O\u0026apos;Rourke et al. (2021) report 11 Mt of methane emissions from the downstream oil and gas sector and Cooper et al. (2021) 26.4 Mt for the largest natural gas supply chains. Our calculations therefore lead to estimates of the same order. Focusing on mitigating these 18 Mt of emissions would make a significant contribution to the fight against global warming. Shirizadeh et al. (2023) showed that adopting the best available methane abatement technologies can lead to an 80% reduction in methane leakage along the natural gas value chain, capping the additional environmental burden to 8% of direct CO\u003csub\u003e2\u003c/sub\u003e emissions (compared with 35% today).\u003c/p\u003e\n\u003cp\u003eAs shown in Figure 2, the greater the demand for gas, the greater the methane emissions. However, the data are widely dispersed around the regression line. This is due to UFG percentage effects: countries with a high UFG percentage are above the line, the others below. The results by countries are mapped in Figure 3. They point to the following top 10 countries: USA (5.62 Mt), Russia (3.06 Mt), Pakistan (1.76 Mt), Iran (1.45 Mt), Australia (0.65 Mt), Saudi Arabia (0.59 Mt), Argentina (0.49 Mt), Turkey (0.45 Mt), Canada (0.43 Mt), and Qatar (0.35 Mt). These top ten countries include major gas producers, consumers and transit countries. The largest producing countries (United States, Russia, Canada, Iran) are the most mature, as gas networks were first built in the vicinity of major gas fields. They therefore have the oldest infrastructure networks. The main producing countries are among the top 10 emitters, with the exception of China and Norway, but these two countries have not been analyzed here. China, the world\u0026apos;s leading methane emitter due in part to coal mining, also records a significant amount of fugitive and vented methane emissions from downstream gas (0.85 Mt from pipelines and LNG facilities, according to the IEA\u0026apos;s Methane Tracker database 2023). Norway is a special case, as its production fields are export-oriented, while the volume of natural gas transported for domestic use is marginal. On the other hand, more recent markets and \u0026quot;modern\u0026quot; importing economies also have very dense but better-maintained infrastructure networks, and therefore lower emissions. This is generally the case in Europe with Italy (0.16 Mt), France (0.10 Mt), United Kingdom (0.08 Mt) or Germany (0.02 Mt) and in the advanced Asian countries with South Korea (0.03 Mt), Japan (0.01 Mt) or Taiwan (0.0008 Mt). For the former, the results can be attributed to good practices. For the latter, it should be remembered that they mainly import LNG, which means that their networks are less dense. This choice can also be explained, particularly in the case of Japan, by the high seismic risk.\u003c/p\u003e"},{"header":"4.\tConclusion","content":"\u003cp\u003eWith growing environmental and financial concerns about potential levels of methane emissions, the issue of methane emissions in general and UFG in particular is increasingly on the agenda. UFGs are associated with leaks, theft, inaccurate metering, and operations along natural gas transmission and distribution networks. Reducing them would not only reduce financial losses, but also, and above all, help meet the 2050 climate objectives. The persistence of methane in the atmosphere is much lower than that of CO\u003csub\u003e2\u003c/sub\u003e: a decrease in the quantities of methane emitted would have a rapid beneficial effect.\u003c/p\u003e\n\u003cp\u003eOn the basis of various gas network data, we first estimated the UFG and then calculated the associated methane emissions. The average UFG for the world is 1.7%, but with significant disparities between regions, ranging from 0.01% to 15%. The resulting methane emissions are provided by country and correspond to 18 Mt worldwide. The results point to two types of country. On the one hand, the main producing countries are characterized by high UFG volumes and high methane emissions. The reason for this is the age of their gas networks. By comparison, networks in more recent markets or advanced countries have fewer leaks, leading to more moderate methane emissions. This suggests that it is possible to cut methane emissions. The complete elimination of gas leaks is impossible, but the implementation of robust maintenance and inspection strategies for pipelines and equipment can help reduce them. An additional advantage of the counting methodology developed in this paper is that it can be repeated every year enabling future emission reductions to be verified.\u003c/p\u003e\n\u003cp\u003eFinally, regulations encouraging the disclosure of shrinkage and OUG data will be a step in the right direction. These practices will make operators publicly accountable. Greater transparency of UFG data on the part of the stakeholders concerned is necessary to better identify actions to be taken to curb methane emissions. In addition, it will prevent operators from potentially passing on the cost of UFG to the end consumer.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBotev L, Johnson P (2020) Applications of statistical process control in the management of unaccounted for gas. Journal of Natural Gas Science and Engineering 76:103194. https://doi.org/10.1016/j.jngse.2020.103194\u003c/li\u003e\n\u003cli\u003eCain M, Jenkins S, Allen MR, Lynch J, Frame DJ, Macey AH, Peters GP (2022) Methane and the Paris Agreement temperature goals. Phil. Trans. R. Soc. A.380.https://doi.org/10.1098/rsta.2020.0456. \u003c/li\u003e\n\u003cli\u003eCEDIGAZ (2023) Unaccounted for gas (UFG) in gas network utilities \u0026ndash; An international perspective. https://www.cedigaz.org/unaccounted-for-gas-ufg-in-gas-network-utilities-an-international-perspective/. 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Nature Communications. 14:5756. https://doi.org/10.1038/s41467-023-41527-9\u003c/li\u003e\n\u003cli\u003eSmith SJ, Chateau J, Dorheim K, Drouet L, Durand-Lasserve O, Fricko O, Fujimori S, Hanaoka T, Harmsen M, Hilaire J, Keramidas K, Klimont Z, Luderer G, Moura MCP, Riahi K, Rogelj J, Sano F, van Vuuren DP, Wada K (2020) Impact of methane and black carbon mitigation on forcing and temperature: a multi-model scenario analysis. Climatic Change. 163:1427\u0026ndash;1442. https://doi.org/10.1007/s10584-020-02794-3\u003c/li\u003e\n\u003cli\u003eWeller ZD, Hamburg SP, von Fisher JC (2020) A national estimate of methane leakage from pipeline mains in natural gas local distribution systems. Environmental Science and Technology. 54:8958-8967. https://doi.org/10.1021/acs.est.0c00437\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"methane, emissions, gas network, greenhouse effect, global warming","lastPublishedDoi":"10.21203/rs.3.rs-3762945/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3762945/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Given the significant global warming power and short atmospheric lifetime of methane, one of the most effective mitigation strategies for limiting global warming over the short term is to target the anthropogenic sources of methane and rapidly reduce their emissions. The unaccounted for gas phenomenon in natural gas transmission and distribution networks reflects an imbalance between what enters the gas network and what leaves it. The aim of this paper is to investigate the possibility of leaks along these gas networks, and to determine whether this leads to methane emissions, since natural gas is mainly composed of methane. First, flow data measured along gas networks are collected and used to assess unaccounted for gas by country. A global average value of 1.7% is observed, but with significant disparities between regions ranging from 0.01% to 15%. Second, unaccounted for gas values permit to assess the quantities of methane released into the atmosphere by gas networks. In total, 18 Mt of methane were emitted in 2021. The main producing countries present high unaccounted for gas volumes and methane emissions, which can be explained by the age of their gas networks. Conversely, networks in more recent markets or advanced countries have fewer leaks, leading to more moderate methane emissions. This shows than methane emissions can be reduced in well-maintained networks. The accounting method developed in this article would make it possible to verify the emissions reductions announced for gas networks in the future if repeated over time.","manuscriptTitle":"Global methane emissions from natural gas networks","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-29 13:54:31","doi":"10.21203/rs.3.rs-3762945/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1d4277cf-0aa7-4dfe-9eba-a90517c61166","owner":[],"postedDate":"January 29th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-06-15T17:50:09+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-29 13:54:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3762945","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3762945","identity":"rs-3762945","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}