Natural gas: Not all it’s fracked up to be?
Natural gas is being touted as a “game changer” and a “bridge to a low carbon economy.” It is an abundant, made-in-America energy source. It is about half as carbon intensive as coal when burned.
The figure below suggests that a natural gas fueled transition to a less carbon intensive economy has already begun. Domestic, energy-related carbon dioxide emissions have declined 12 percent since the peak in 2007. An important driver of this trend is the substitution of natural gas for coal in electricity generation.
Of course, this picture gets much more complicated when you look upstream and broaden your perspective to consider not just carbon dioxide -the most prevalent anthropogenic greenhouse gas- but also “fugitive” methane emissions.
Methane, the primary constituent of natural gas, can escape during extraction, processing, and distribution. These emissions have the potential to eliminate the carbon advantage of gas over coal and oil. There is heated debate over the extent to which this potential is being realized. A new study suggests that more methane is leaking out of the natural gas supply system than we previously thought.
A little methane goes a long way
A recent WRI report summarizes the conventional wisdom about the relationship between methane leakage from natural gas production and the relative carbon intensity of gas versus coal. The graphic below (taken from the WRI report) suggests that natural gas loses its relative carbon advantage at a methane leakage rate of between 3-4 percent over a 20 year time horizon:
How much methane is leaking?
This is a complicated and controversial question. Complicated because there are hundreds of thousands of natural gas wells and thousands of miles of pipeline in the U.S. This precludes direct measurement of all sources. The controversy stems from the fact that different approaches to measuring fugitive emissions are yielding different answers:
- The US EPA uses a “bottom up” approach. Total emissions are calculated based on assumed emissions factors which summarize the amount of methane leakage associated with different types of equipment or processes. In April, the EPA revised its estimates of methane emissions from natural gas production to levels consistent with a leakage rate of 1.65 percent.
- In September, the first of 16 EDF-sponsored academic studies of methane emissions was released. Researchers monitored methane releases from 190 sites. Although certain devices were found to have emissions rates that exceeded EPA estimates, the overall findings were generally consistent with EPA numbers. This study provides an important data point. But only a subset of domestic companies volunteered to participate. The study thus characterizes the practices at sites operated by participating companies, but not necessarily the industry at large.
- An alternative “top down” approach measures methane concentrations directly. In February of last year, researchers took advantage of weather conditions that allowed them to directly measure methane emissions from a natural gas field in Utah. This study was groundbreaking- but limited to a single field on a single day. Researchers found methane levels that were consistent with leakage rates between 6.2 and 11.7 percent. Although critics have raised questions about how direct measurements of methane emissions are converted to a percentage leakage rate.
- More recently, a far more comprehensive top down study of domestic methane concentrations was released. Researchers combined ground-level and aerial measurements of methane with meteorological data and computer modeling that attributes emissions to specific economic sectors. The paper provides evidence to suggest that fugitive methane emissions from oil and gas systems in 2007-2008 were five times greater than EPA estimates. Analysis of more recent measurements is in the works.
Connecting the dots between these different studies is not easy. But it is important because the stakes are enormous. Future work by EDF-sponsored researchers and others should bring these leakage numbers into sharper focus.
How about plugging those leaks?
Recent news that fugitive emissions from the natural gas system are higher than previously thought strengthens the case for more stringent regulation of these emissions. Fortunately, there are several seemingly cost effective leakage mitigation measures that have been successfully implemented in the field, but are far from universally adopted. There are also some exciting new technologies in the proverbial pipeline; just last week, some Berkeley students showcased an emerging fuel cell technology that can be used to power electronic controls at gas wells while eliminating venting and flaring. Accelerated deployment of these mitigation options would help seal in the near-term climate change mitigation benefits of natural gas versus coal.
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Very interesting article! Thank you Meredith for sharing it! I agree with you that methane leaks has to be taken care of, especially since “fracking” looks like its here to stay for at least the next several decades. Moreover, with the U.S. Gas Boom, one can expect to see a sharp rise in the use of “fracking.” It will be the job of the GTC Techs of the world to develop and put in place technologies that help decrease Greenhouse gas emissions, so the next Generation doesn’t have to suffer our consequences.
There’s another factor that limits the beneficial effects of natural gas on power sector GHG emissions, which is that natural gas displaces non-fossil resources also, it doesn’t just displace coal. My friends at CO2 scorecard explored both of these issues in this recent research note: http://www.co2scorecard.org/home/researchitem/28
Because of the regional variations it’s important to do the analysis at a fine level of regional disaggregation (previous national level analyses give misleading results). There is still significant uncertainty, but it’s not at all clear that the low price of natural gas has helped reduce greenhouse gas forcings significantly when you include the fugitive methane emissions and the displaced non-fossil resources.
In an earlier Energy Institute study it was concluded that in most parts of the US the plug-in electric car produces more carbon (because in the final analysis it is fueled by coal) than the hybrid. The exception was in California where natural gas produces much of our electricity. So is it possible that fracking eliminates the plug-in electric car slight carbon advantage even in California?
Leaking Methane contributes to global warming and combines with sunlight causing Colorado to have some of the Nation’s highest ozone levels (10% of Colorado children now have asthma). Colorado recently adopted regulations urgently needed to address leaking frac gas and the resulting ozone.
• Detect leaks from tanks, pipelines, wells and other facilities using devices such as infrared cameras.
• Inspect for leaks at least once a month at large facilities and plug leaks.
• Adhere to more stringent limits on emissions from equipment near where people live and play.
• Use flare devices to burn off emissions from facilities not connected to pipelines.
http://www.denverpost.com/environment/ci_24548337/proposed-colorado-air-pollution-regs-clamp-down-oil
Meredith
Do these studies examine the full system-wide impacts of natural gas substitution or just the incremental methane impacts? For example, do these new calculations include the additional carbon reductions that could be attributed to natural gas because it is transported in pipelines that eliminate rail and truck transport, with corresponding reductions in distribution losses, reduced roadway wear, and reductions in the environmental mitigation necessary to reclaim coal and oil sites?
A significant fraction of CO2 production (~1/3) is from the transportation sector. It is economically feasible to produce both jet fuel and diesel with existing technology (Sasol) to replace imported oil
to US. Flaring of stranded natural gas and methane escape from imported oil production (which I assume is less efficient than US oil production) should be considered in the scenario of fracking to produce natural gas in the US to be used for transportation fuel to replace that produced from imported oil. I think that would be an interesting study.
Do these comparisons to coal also account for coal bed methane that escapes during coal mining?
Great question. I was able to correspond with one of the authors of the WRI study who indicated he was “reasonably sure” that upstream coal emissons are included in the WRI analysis of the GHG emissions intensity of gas vis a vis coal. Another paper germane to this comparison is Alvarez at al (2011) http://www.pnas.org/content/early/2012/04/02/1202407109. These authors find that new natural gas power plants produce net climate benefits relative to efficient, new coal plants using low gassy coal as long as leakage in the naturalgas system is less than 3.2% from well-to-burn. These authors report assuming average leakage rates for both coal and natural gas. Hope this suffices as an incomplete answer to your good question…
Thanks for the response!