10/14/2014 A Close Look at Fugitive Methane Emissions from Natural Gas | World Resources Institute

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A natural gas drilling rig. Photo credit: JustinWoolford, Flickr

A Close Look at Fugitive Methane Emissions fromNatural Gasby James Bradbury and Michael Obeiter - April 02, 2013

Natural gas is booming in the UnitedStates. Production has increased by20 percent in the last five years,fueled largely by technologicaladvances in shale gas extraction.Other countries--including China--arenow studying our experience withthis abundant new resource.

But the growing role of natural gas inthe U.S. energy mix hasn’t comewithout controversy. Natural gasdevelopment poses a variety of environmental risks. In addition to habitatdisruption and impacts on local water and air quality, one of the most significantconcerns is the climate impact resulting from the “fugitive methane emissions”that escape into the atmosphere from various points along the natural gas supplychain.

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So what are fugitive methane emissions, and how big of a problem are they? Howdo emissions from natural gas compare to those from coal? And are there ways tomitigate them? The answers to these questions will help us better understand hownatural gas development will affect climate change.

What Are Fugitive Methane Emissions, and How Do They Contribute to ClimateChange?

Methane, the primary component of natural gas, is a powerful greenhouse gas--25times stronger than carbon dioxide (CO2) over a 100-year time horizon and 72times stronger over a 20-year horizon. Though methane represents only about 10-12 percent of all U.S. greenhouse gas emissions, it is a significant driver of short-term warming, and reducing methane emissions can help slow the rise in globaltemperatures.

While proponents of natural gas often tout its “green” credentials—combustion ofnatural gas emits roughly one-half the CO2 of coal combustion—this is not thewhole story. When it is extracted from the well, natural gas is composed of roughly83 percent methane, after processing and through the point of delivery, it is morethan 90 percent methane. Producing, processing, and transporting of natural gascan release some of this methane into the atmosphere. Accidental methane leaksand routine venting--which together, make up fugitive methane emissions--reducethe comparative climate advantage of natural gas for electricity generation. Plus, atcurrent estimated leakage rates, fugitive emissions actually make compressednatural gas a questionable choice for fuel-switching in cars and trucks.

What Is the Extent of the Problem?

There is still considerable uncertainty over the amount of fugitive methane emittedover the lifetime of a natural gas well. However, some aspects generate little debate—namely, that emissions from natural gas production are substantial and occur atevery stage of the natural gas life cycle, from pre-production through production,processing, transmission, and distribution. The U.S. Environmental Protection

10/14/2014 A Close Look at Fugitive Methane Emissions from Natural Gas | World Resources Institute

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Agency (EPA) estimates that more than 6 million metric tons of fugitivemethane leaked from natural gas systems in 2011. Measured as CO2-equivalentover a 100 year time horizon, that’s more greenhouse gases than were emitted byall U.S. iron and steel, cement, and aluminum manufacturing facilities combined.

Many ongoing studies aim to provide more clarity on the extent of fugitive methaneemissions from natural gas. We’ll get a clearer picture when data from thesestudies is looked at in conjunction with industry data reported to the EPAGreenhouse Gas Reporting Program. But with about 500,000 existing natural gaswells, thousands of miles of pipeline, and a growing interest in natural gasdevelopment, we’ll never have a truly complete picture of the amount of methanebeing emitted.

Is Natural Gas Better than Coal?

Considerable media attention has focused on the question of whether gas is“better” than coal from a climate perspective. On the one hand, this question sets alow bar for environmental performance—studies have found that by just about anymeasure, every other energy source is less damaging to the environment and publichealth than coal. On the other hand, this is an important benchmark, since morethan 30 percent of U.S. natural gas is used for electric power generation and morethan 90 percent of all U.S. coal consumption is used for this purpose. The questionhas also received heightened attention as many older, inefficient coal-fired powerplants retire and natural gas-fired plants provide a growing share of total electricpower generation.

At the point of combustion, natural gas is roughly half as carbon-intensive as coal.However, this comparison fails to account for upstream fugitive methaneemissions. When used for electric power generation, natural gas is typically muchmore efficient than coal, but natural gas is not a more energy efficient fuel optionfor all uses—for example, in the case of vehicles. Also, if fugitive methaneemissions exceed 3 percent of total gas production, natural gas’s climateadvantage over coal disappears over a 20-year time horizon.

The critical question is: Given the current extent of U.S. natural gas production—

10/14/2014 A Close Look at Fugitive Methane Emissions from Natural Gas | World Resources Institute

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and the fact that production is projected to expand by more than 50 percent in thecoming decades—are we doing everything we can to ensure that emissions are aslow as is technologically and economically feasible? The answer to that questiontoday is clearly “no.”

How Can We Mitigate Natural Gas’s Impact?

Numerous cost-effective technologies can reduce fugitive methane emissions,which will curb global warming and save money for energy companies and forconsumers. While some companies are voluntarily implementing thesetechnologies to varying degrees, the industry is vast, including thousands ofparticipants with diverse market interests. Much more can be done. In a workingpaper to be published later this week, we discuss in greater detail the scale of themethane leakage issue, as well as numerous policy and technology pathways forstate and federal authorities to begin limiting these harmful emissions.

Ultimately, cleaning up fugitive methane should be an urgent priority to help slowthe rate of climate change in the near-term. We’ll also need policies to significantlyreduce carbon dioxide emissions—from the combustion of natural gas as well asother fossil fuels. To stabilize the climate at safe levels by mid-century, we need toaddress GHG emissions from all sources. Fugitive methane is one important, cost-effective opportunity that we can begin addressing today.

LEARN MORE: Stay tuned for our forthcoming working paper, Clearing theAir: Reducing Upstream Greenhouse Gas Emissions from Natural GasSystems, which will be released later this week.

TAGS:

climate change, emissions, energy, natural gas, shale gas, uspolicy

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If the global warming

link by Jeremy on Apr 07, 2014If the global warming potential (GWP) of CH₄ is 25 times greater than CO₂ over a100-year period, and if CH₄ emissions account for 10% of total U.S. GHGemissions, then the U.S. impact on global warming is much greater through CH₄emissions than through CO₂. [I'm calculating it like this: volume x GWP = impacti.e. 10 x 25 =250 for methane, and 90 x 1 = 90 for CO₂]. So CH₄ has an impact 2.77times greater (250/90) than CO₂. Surely, you need to emphasize this?

Thanks for your comment,

link by Michael Obeiter on Apr 08, 2014Thanks for your comment, Jeremy, but the 10% figure you cite already takes thehigher global warming potential of methane into account. According to theEPA, methane is roughly 10% of U.S. greenhouse gas emissions, which theycalculate by multiplying the volume of methane emissions - roughly 27 millionmetric tons in 2012 - by the global warming potential of methane (in this case,EPA uses the somewhat outdated 100-year global warming potential of 21).That calculation yields 564.4 million metric tons of CO2 equivalent from allsources of methane. By comparison, EPA estimates that CO2 emissions in 2012were 5,377 million metric tons. For more information, seehttp://www.epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory....

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