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    Breaking down methane emissions across the gas value chain [Making Sense of Methane]

Summary

Part 3 of a five-part series examining the global methane emissions issue: Making Sense of Methane

When natural gas is efficiently combusted to produce energy to heat homes and businesses and fire electric power plants, the associated methane emissions are very small. However, as the Pew Center on Global Climate Change observes, methane from natural gas that is released directly into the atmosphere without being combusted is a potent greenhouse gas.

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Meeting the Methane Challenge: The global natural gas industry has identified the reduction of methane emissions as a key challenge in supporting the global energy transition, and programs are underway around the world to meet this challenge. To inform these initiatives, Natural Gas World and Gas Transitions is pleased to present a five-part series examining methane emissions and their mitigation, contributed by energy consultant and researcher Jennifer Heullant.

by: Jennifer N. Heullant

Posted in:

Featured Articles, Premium, Making Sense of Methane, Volume 4, Issue 8, Volume 4, Issue 4

Breaking down methane emissions across the gas value chain [Making Sense of Methane]

When natural gas is efficiently combusted to produce energy to heat homes and businesses and fire electric power plants, the associated methane emissions are very small. However, as the Pew Center on Global Climate Change observes, methane from natural gas that is released directly into the atmosphere without being combusted is a potent greenhouse gas.

So while natural gas has the lowest direct methane emissions of all fossil fuels when combusted, concerns have been raised about un-combusted emissions in the gas production, processing, and delivery segments.

In 2017, Chris Le Fevre, senior visiting research fellow at the Oxford Institute for Energy Studies, published a paper titled Methane Emissions: From Blind Spot to Spotlight. In this paper, Le Fevre writes that estimating an accurate figure for global methane emissions from the natural gas industry remains a work in progress. Several studies suggest that a global average of 1.5% – 2% of gas across the entire supply chain is broadly correct.

According to data presented in a 2016 methane emissions guide prepared by ICF International for the US Natural Gas Council (NGC), within the natural gas value chain gas transmission accounts for 35% of the gas industry’s methane emissions followed by production (30%), distribution (21%), and processing (14%).

Sources of methane emissions from across the natural gas value chain

The NGC identifies in the report Finding the Facts on Methane Emissions: A Guide to the Literature sources of methane emissions from across the natural gas value chain are characterised as either vented emissions, fugitive emissions, or un-combusted emissions.

Vented emissions are intentional releases of methane due to equipment design or operational procedures, such as from pneumatic device bleeds, blowdowns, and equipment venting. Equipment venting and non-routine flaring occur by design but are difficult to measure.

Fugitive emissions result from methane that leaks unintentionally from equipment or components such as flanges, valves or other equipment. These emission types are the most challenging to manage since the measurement is both impractical (given the size and complexity of the infrastructure) and typically expensive. As these emissions are linked to the natural gas supply chain, they represent more of a threat to the positioning of gas as a low carbon fuel than do other methane emission types.

Un-combusted emissions, as described in NGC’s Finding the Facts report,are small amounts of methane in the exhaust of natural gas combustion equipment in the production, processing and transmission segments. Methane emissions associated with incomplete combustion of fuel in stationary sources is relatively well understood due to the widespread metering of fuel usage and manufacturers’ equipment performance specifications.

According to a 2019 E-brief by Sarah Marie Jordaan and Kate Konschnik published by the C.D. Howe Institute, the magnitude of these emissions remains unresolved. Citing a 2006 piece written by National Gas Machinery Laboratory, Jordaan and Konschnik write, both industry and regulators face challenges in monitoring emissions from oil and gas infrastructure at the level of devices and components, due to the sheer number of them across the supply chain.

Jordaan and Konschnik further write meters have yet to produce reliable data – many are in need of replacement, calibration, or maintenance, creating challenges for accurate calculation due to variations in environmental and other factors (time lags across meters, changing temperatures, volume and pressure of natural gas). Absent the ability to conduct real-time measurement of all devices and components across an extensive oil and gas supply chain, the authors write, inventories rely on occasional, time-limited measurements combined with often outdated emissions factors.

Beyond monitoring of methane emissions, an issue gaining attention amongst NGOs (non-governmental organizations) and regulators are so-called “fat tails” – a small number of leaking components that account for the largest portion of fugitive emission from the natural gas supply chain.

The issue has led some to question the value proposition of natural gas as the significant emission volumes involved means that this issue has the potential to reduce the climate benefits of switching from coal to natural gas. For industry, a better understanding of potential fat tails may offer a very cost-effective means of reducing significant emissions.

Methane emissions influence but do not undermine the environmental case for gas. Le Fevre writes, for example, that if the industry can build on the progress to date and deliver a clearer picture on the level of emissions and actions to address them, the arguments for gas in a decarbonising economy would be more secure.