Measuring Fugitive Methane Emissions

In recent days, news reports and blog posts have highlighted the problem of fugitive methane emissions from natural gas production — leakage of a potent greenhouse gas with the potential to undermine the carbon advantage that natural gas, when combusted, holds over other fossil fuels. These news accounts, based on important studies in the Denver-Julesburg Basin of Colorado and the Uinta Basin of Utah by scientists affiliated with the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado (UC) at Boulder, have reported troubling leakage rates of 4% and 9% of total production, respectively —higher than the current Environment Protection Agency (EPA) leakage estimate of 2.3%.

While the Colorado and Utah studies offer valuable snapshots of a specific place on a specific day, neither is a systematic measurement across geographies and extended time periods  and that is what’s necessary to accurately scope the dimensions of the fugitive methane problem. For this reason, conclusions should not be drawn about total leakage based on these preliminary, localized reports. Drawing conclusions from such results would be like trying to draw an elephant after touching two small sections of the animal’s skin: the picture is unlikely to be accurate. In the coming months, ongoing work by the NOAA/UC team, as well as by Environmental Defense Fund (EDF) and other academic and industry partners, will provide a far more systematic view that will greatly increase our understanding of the fugitive methane issue, though additional studies will still be needed to fully resolve the picture. What follows is a briefing on the fugitive methane issue, including the range of measurements currently underway and the need for rigorous data collection along the entire natural gas supply chain.

Why methane leakage matters. Natural gas, which is mostly methane, burns with fewer carbon dioxide emissions than other fossil fuels. However, when uncombusted methane leaks into the atmosphere from wells, pipelines and storage facilities, it acts as a powerful greenhouse gas with enormous implications for global climate change due to its short-term potency: Over a 20-year time frame, each pound of methane is 72 times more powerful at increasing the retention of heat in the atmosphere than a pound of carbon dioxide. Based on EPA’s projections, if we could drastically reduce global emissions of short-term climate forcers such as methane and fluorinated gases over the next 20 years, we could slow the increase in net radiative forcing (heating of the atmosphere) by one third or more.

Fugitive methane emissions from natural gas production, transportation and distribution are the single largest U.S. source of short-term climate forcing gases. The EPA estimates that 2.3% of total natural gas production is lost to leakage, but this estimate, based on early 1990’s data, is sorely in need of updating. The industry claims a leakage rate of about 1.6%. Cornell University professor Robert Howarth has estimated that total fugitive emissions of 3.6 to 7.9% over the lifetime of a well.

To determine the true parameters of the problem, EDF is working with diverse academic partners including the University of Texas at Austin, the NOAA/UC scientists and dozens of industry partners on direct measurements of fugitive emissions from the U.S. natural gas supply chain. The initiative is comprised of a series of more than ten studies that will analyze emissions from the production, gathering, processing, long-distance transmission and local distribution of natural gas, and will gather data on the use of natural gas in the transportation sector. In addition to analyzing industry data, the participants are collecting field measurements at facilities across the country. The researchers leading these studies expect to submit the first of these studies for publication in February 2013, with the others to be submitted over the course of the year.

The systemic leakage rate will determine whether or not natural gas provides a net climate benefit, with implications for assessing the relative environmental benefits of fuel switching from coal or diesel to natural gas.

EDF’s model disaggregates the leak rate of 2.8% as follows: 2.0% is leakage from well to city gate (this applies to power plants); 2.3% is leakage from well-to-end user (applies to homes and industrial users); the additional 0.5% accounts for leakage from natural gas vehicle refueling and use.
Note: EDF’s model disaggregates the leak rate of 2.8% as follows: 2.0% is leakage from well to city gate (this applies to power plants); 2.3% is leakage from well-to-end user (applies to homes and industrial users); the additional 0.5% accounts for leakage from natural gas vehicle refueling and use.

As this chart illustrates, lowering the methane leakage and venting rate to 1% of total production would double the climate benefit derived from coal-to-natural gas fuel switching over the next 20 years — producing as much climate benefit in that time as closing one-third of the nation’s coal plants. (This assumes that 1% is the amount of natural gas produced at well sites lost to the atmosphere, in comparison to a baseline of 2.8%, and that the retired coal-fired generation is replaced with equal parts high efficiency natural gas fired generation and zero-emissions electric generation, such as renewables.)

Preliminary studies. Recently, a series of studies has emerged, each providing a snapshot of leakage from a specific region and a specific segment of the natural gas system at a specific point in time:

  • 2010; Fort-Worth, TX: Analysis of reported routine emissions from over 250 well sites with no compressor engines in Barnett Shale gas well sites in the City of Fort Worth revealed a highly-skewed distribution of emissions, with 10% of well sites accounting for nearly 70% of total emissions. Natural gas leak rates calculated based on operator-reported, daily gas production data at these well sites ranged from 0% to 5%, with 6 sites out of 203 showing leak rates of 2.6% or greater due to routine emissions alone.
  • February 2012; Denver-Julesburg, CO: Tower study by NOAA/University of Colorado at Boulder scientists suggested that up to 4% of the methane produced at a field near Denver was escaping into the atmosphere.
  • December 2012: At an American Geophysical Union meeting in San Francisco, the NOAA/University of Colorado at Boulder team described the unpublished results of a study in the Uinta Basin, Utah, suggesting even higher rates of methane leakage, 9% of total production.
  • Forthcoming studies include: March 2013 (est.) reporting by University of Texas at Austin (in collaboration with nine corporate partners and EDF) of a study about emissions from gas production; subsequent 2013/early 2014 studies will address gathering, processing, long-distance transmission and local distribution.

Some of these studies have revealed or are likely to reveal relatively high levels of fugitive methane emissions, while others are likely to reveal lower levels. None of them, taken alone or in tandem, can yet provide an accurate picture of system-wide leakage. As a news story in the journal Nature concluded, “Whether the high leakage rates claimed in Colorado and Utah are typical across the U.S natural-gas industry remains unclear. The NOAA data represent a 'small snapshot' of a much larger picture that the broader scientific community is now assembling.”

Great care should be taken to avoid drawing conclusions based on the partial data these studies provide. This will be a particular challenge given that advocates for natural gas production are likely to call attention to the low-leakage results, while opponents of natural gas production are likely to call attention to the high-leakage results, with each side claiming that the latest study “proves” its argument. Neither claim will be reliably accurate.

In other words, anyone who wants to get this important story right will need to be patient and wait for the more comprehensive results to come in later this year. Until then, no accurate conclusion can be drawn about the full scope of this critical issue. Please proceed with caution.

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4 Comments

  1. Posted January 4, 2013 at 7:47 pm | Permalink

    Thank you for pointing out that much more comprehensive measurement needs to be done, as initially suggested by Howarth et al.,2011. However, I suggest you add these items to your future discussions on this topic:

    1. You correctly point out the importance of the ~20 year time period for methane emissions, but write: "Over a 20-year time frame, each pound of methane is 72 times more powerful at increasing the retention of heat in the atmosphere than a pound of carbon dioxide." You should point out that there is uncertainty about GWP's and that more recent peer-reviewed science (Shindell et al., 2009) suggests that the GWP over 20 years could be as high as 105. Such an increase would lower even further the tipping point in leak rate for "advantage natural gas" over coal for electricity generation.

    2. Your write: "February 2012; Denver-Julesburg, CO: Tower study by NOAA/UC scientists suggested that up to 4% of the methane produced at a field near Denver was escaping into the atmosphere." That is not correct. Petron et al. estimate between 2.3 and 7.7% annual production loss, not "..up to 4%". Nobody can or should present a single value when there is significant uncertainty in such measurements, regardless of who is doing the measurement, including the EDF team. You should also more clearly indicate that both NOAA measurements did NOT include transmission/distribution pipeline system and storage losses.

    3. The tipping point for "advantage natural gas" for electricity generation also has uncertainty associated with it. Therefore, when sufficient (in space and time) measurements across the life cycle have been completed in a few years, we will have two ranges of numbers, one for measured loss rate, another for estimated tipping point rate. The former is technology-of-measurement-based, the latter is both technology ( e.g. generation efficiencies) and science based (e.g. which GWP to use). It is likely these ranges will overlap, which will then lead to a policy decision: how much difference does one want between the average value of one relative to the other? Does one want to use an average value for each, or does one want a "factor-of-safety" based on risk analysis?

    4. You should point out that only about a third of natural gas use in the US is for electricity generation. If it turns out to be a wash, or even a close call, between coal and natural gas for this purpose, then what do you propose to do about the other uses of natural gas? Your readers should be asked to contemplate the choice between home heating (a higher use of natural gas in the US) with natural gas and with electricity generated from green renewables, rapid deployment of which is being hindered by rising natural gas production.

    5. Finally, it will take a few more years to get all the leak rate measurements done. It will take many more years to coerce the industry to implement leak reduction measures, and it will also take much capital which could be better invested in the real long-term fix to the problem: more rapid deployment of green renewables. Global warming continues, and we do not have 100 years, or even 20, to spend before starting to do the right things. You know what they are.

    • shamburg
      Posted January 7, 2013 at 7:58 pm | Permalink

      You raise several good points, Dr. Ingraffea. Each of them are addressed here:

      1. As you suggest it is important to continue to evaluate the implications of different greenhouse gases on net radiative forcing. While there is evidence that the short-term forcing may be higher for methane than previously suggested, there is a lack of consensus on this point. The analytical framework we proposed – Technology Warming Potentials – in our 2012 paper in Proceedings of the National Academy of Sciences (PNAS) easily allows for such adjustments as the science coalesces around a better understanding (http://www.pnas.org/content/109/17/6435).

      2. Agreed, I should have presented the paper results as a range. The related efforts to quantitative fugitive methane work EDF is currently involved with will present leak rates as mean values with confidence intervals.

      3. The issue of how to ensure that fuel switching leads to net climate benefits is one I have been concerned about for the past several years and was the impetus for the development of the Technology Warming Potential metric that more easily allows for these shifting factors to be considered across time and space. It is important to not limit concern about the impacts of fuel switching at 20 years and 100 years, but rather to consider all points in time and across shifting technologies. We developed a simple spreadsheet model that uses the underlying science and math in the PNAS paper described above to allow users to understand the interactions of different technologies with fuel switching across time (http://www.edf.org/energy/methane-leakage-modeling-tool).

      4. As to your points about the role that natural gas plays in our energy economy now and in the future, I couldn’t agree more that getting a handle on methane emissions is critical — whether or not natural gas continues to be a fuel of choice for new electric generation. Two-thirds of the natural gas consumed in the U.S. goes to a variety of commercial and industrial uses, to say nothing of the natural gas used to heat our homes and cook our food, where alternatives, beyond aggressively ramping up energy efficiency efforts – an important thing to do – are few. We recently produced a graphic showing how natural gas is used in the U.S., (http://www.edf.org/climate/why-natural-gas-important), as well as one illustrating our chief areas of concern with gas production (http://www.edf.org/climate/five-areas-of-concern). We conclude that no one should have to trade their health or quality of life for cheap energy, and that's why EDF is fighting for tough rules and strict oversight.

      As to the role that natural gas plays in the electric sector, my colleague, Mark Brownstein, reminds me that supply and price of natural gas is only one factor in the competitive equation for renewables. What also matters is demand for electricity and public policies such as carbon pricing, renewable portfolio standards, or the recently renewed production tax credit. Mark notes that, by itself, a high natural gas price simply becomes an invitation to new coal and nuclear, as was the situation five years ago when natural gas regularly cleared $6-$8 mmbtu and we were battling proposals for over 100 new coal fired power plants. It’s the reason why whether gas prices are high or low, a major thrust of EDF’s energy and climate work is focused on pollution standards for power plants, effective carbon mitigation policies, and accelerating the shift to clean, renewable energy.

      Bottom line: any amount of natural gas, produced for any reason, at any price should be done with minimal fugitive emissions, and maximum effort to protect public health and the environment.

      5. Based on the scope and number of ongoing research projects focused on quantifying fugitive emissions from the natural gas supply chain I am confident there will be a clearer understanding of activities/equipment requiring mitigation over the next year. Additionally the early data (again see PNAS paper) suggests that emissions profiles represent a ‘fat tail’ problem, relatively few emitters account for a high proportion of total emissions. If in fact this is the case in most regions then mitigation can be accomplished by ensuring that best practices (those not producing significant leaks at the majority of sites) are implemented more uniformly. The point is, we already know enough to be sure that we need to reduce fugitive emissions, and we have the technology to begin doing so now. Reducing leaks as soon as possible is not in conflict with rapid deployment of green renewables – we need both!

  2. Mark Ruffalo
    Posted January 5, 2013 at 9:45 pm | Permalink

    The NOAA Study vindicates Bob Howarth's Study on gas migration. It is interesting to note that Robert Howarth has been attacked repeatedly by the Fossil Fuel industry and the dead end pro natural gas "environmentalists". They say that these studies are inconclusive. Kind of reminds one of the phony Climate Change deniers saying that the studies on Climate Change are also inconclusive. Whoops, actually they are the same. Beware studies done by the Fossil Fuel industry. Cigarette industry anyone? Fund bunk studies paid for by the industry, throw doubt on the real studies, use front groups created and maintained by the industry to green wash, spread propaganda and further cloud the issue. Where there is smoke there is a cigarette and where there is natural gas production there is uncontrollable migration.

    Natural Gas is many more times damaging then carbon dioxide. Natural Gas is a dirty carbon fuel, mining it degrades water and air, brings tons of toxic material up to the surface of the earth including heavy metals and radiation and requires using trillions of gallons of fresh surface water out of which about a third of that will never be usable again, remaining trapped in the well.

    When it will cost us about 700 billion dollars to convert our infrastructure to a natural gas Infrastructure and the Climate Change mitigation is now clearly negligible why not put that incredibly enormous amount of money into sustainable and clean energy sources such as Wind Water and Sun that won't contribute to climate change and will actual begin to stop it? Why not invest our time and money into truly fighting this enemy of all living things and ween ourselves off of dirty killing fossil fuels? Why wallow around in the muck of gas drilling mud and instead take some real and responsible steps to move away from more carbon fuel usage?

    It would be nice to see on EDF's home page a link to real renewable and sustainable energy instead of a "Natural gas" link. Proceeding with real caution is proceeding with a fossil-fuel-free nation by 2030. Proceeding with natural gas is neither cautious nor particularly clear headed. Fortunately the party is coming to an end, the fog of fossil fuel propaganda is lifting and what do we see appear in the distance? A long expensive bridge fuel leading to absolutely nowhere, well, rather, to disaster.

    For those that stuck with me please refer to Anthony Ingraffea's comments further up this thread. He raises some very interesting points.

    • shamburg
      Posted January 7, 2013 at 8:01 pm | Permalink

      Mark, Thanks for your thoughtful post. I know and respect Bob Howarth as well as the NOAA scientists, and I think all of us would agree that it is too soon to say whether the NOAA studies support’s Bob’s work on gas migration. As I explain above, the NOAA studies are troubling snapshots, but they are not conclusive. The data simply aren’t in yet. We are working on it, as described above, and we aim to begin answering these questions with methane research data we are collecting along with our partners. The first data set will be released in the early spring.

      You asked for links to EDF’s renewable and sustainable energy work. Here are a few:

      • EDF Energy Innovation Series: http://www.edf.org/energy/energy-innovation-series
      • Pushing for a clean energy future: http://www.edf.org/climate/remaking-energy
      • Smart grid: http://www.edf.org/climate/smart-grid-overview
      • Pecan Street Inc.: http://www.edf.org/energy/building-smarter-grid-austin-texas

      If you’re interested in hearing more about our renewables work – and there’s a great deal to tell — I’d invite you to speak with my colleagues Jim Marston and Mark Brownstein in our US Energy and Climate Program. They’d love to sit down with you.