Methane leaks claims in a recent study turn out to be fragile at best, dashing fractivist hopes for the illusive game-changer in war over natural gas.
When a study came out a short time ago suggesting, against all previous evidence, that methane leaks from natural gas development made a switch from diesel to natural gas less than beneficial for the climate, the fractivist contingent, including “Tony the Tiger” Ingraffea went ga-ga insisting this was a game-changer. Like all their previous game-changers, it quickly proved to illusive as it was revealed the report was actually net-positive regarding the switch to natural gas. Now comes evidence indicating the negative conclusions seized on by fractivists are flimsy at best.
The basic flaws in the reporting on the study by the New York Times (surprise, surprise) were noted quickly by a writer at the Council on Foreign Relations (CFR) blog (see picture to right of the CFR’s headquarters in New York City). The American Natural Gas Association (ANGA) explains further in a post on its blog (emphasis added):
Over the last week, members of the energy and environment press have been aflutter about methane. This comes in response to the release of a paper titled “Methane Leaks from North American Natural Gas Systems” in Science Magazine, whose primary claim is that there are higher-than-expected methane emissions.
It’s unfortunate that one reported finding – that there is little to no climate benefit from switching vehicles from diesel to natural gas – is not based on the paper’s data and conclusion. Brandt relies on a 2012 Proceedings of the National Academy of Sciences paper that uses an uncharacteristically low estimate of engine efficiency. The Council on Foreign Relations’ Michael Levi does a good job putting this claim into context, which you can read here.
The paper’s authors outline a number of causes for uncertainty, and so we outline them here:
- When determining the emissions from the natural gas production process, activity data is important. Adam Brandt, the paper’s lead author, concedes this point and notes that data should improve with increased reporting requirements by the EPA. The EPA has published data for 2011 and 2012 showing a drop in methane emissions. While a modest drop, it occurred despite increased natural gas production.
- Brandt also identifies clear challenges associated with estimating natural gas sector emissions by using an atmospheric approach (“top-down”). The most significant of these being how observed concentrations of methane are attributed to potential sources. Does the methane come from fossil sources rather than naturally occurring ones? The authors point out that studies can differentiate liquid petroleum and natural gas sources from coal, but are quick to admit that attributing methane emissions to the natural gas system is “more challenging.”
- Brandt uses EPA’s Greenhouse Gas Index as a comparative baseline to illustrate how it under-reports methane emissions compared to measurement-based studies. Estimating methane emissions is a complex and difficult task, and it should be noted that the EPA changes its Inventory every year. The magnitude of these changes can be significant.
Some of the news coverage is perpetuating a straw-man argument by limiting the benefits of using natural gas to reduced greenhouse gas (GHG) emissions. While lower GHG emissions are one benefit of using natural gas, it is not the only one. Growing use of natural gas in the power and transportation sectors is helping cut hazardous emissions, increase our nation’s energy security and saving consumers money.
Despite the uncertainty surrounding the emission sources of methane, this paper makes two positive observations. The first is that this greater-than-expected methane emissions are “unlikely to be large enough to negate climate benefits of coal-to-[natural gas] substitution.” The second is that hydraulic fracturing is unlikely to be a dominant contributor to total emissions.
There is no doubt that more information is needed to identify the sources of methane emissions, and to limit emissions during the natural gas development process. It is encouraging that early EPA data shows progress as the industry reduces its environmental footprint. As emissions capturing technology and so-called “green completions” are implemented across the country, we believe this downward trend will continue.
This isn’t all the CFR post uncovered either. Here’s some more from that source:
The sole sentence in the paper that addresses diesel-to-gas switching cites a two-year-old Proceedings of the National Academy of Sciences (PNAS) paper – nothing new is added. More problematic is that the 2012 paper, which is mostly excellent, stumbles when it comes to comparing diesel with natural gas.
Why? If you dig up the references that the PNAS paper uses you’ll find that it assumes CNG-fueled vehicles are 20.7 percent less efficient than diesel-fueled ones. There is a citation for this – and indeed many CNG-fueled vehicles suffer a severe efficiency penalty. But this is far from universal. Diving a couple references deep reveals that the figures are not for CNG-fueled trucks in general but for urban buses – one of the worst cases (and perhaps the worst case) for CNG. Moreover, the original reference has pretty big uncertainty bounds, though those are dropped as the paper’s contents are exploited elsewhere. A quick spin through reports unearthed by a Google search about the CNG efficiency penalty reveals a wide range of estimates – from no penalty at all to a bit north of the 20.7 percent that the PNAS authors use – depending on the engine technology chosen and how (and where) the vehicle is driven. If you adopt the more favorable estimates for the efficiency penalty – which tend to correspond to more modern engines (though not universally) and to non-urban applications – switching from diesel to CNG is indeed mildly beneficial for the climate.
So, when we get to the bottom line, the one negative from the study is nothing but a damned poor assumption. So goes the day to day battles in the fracking war; lousy assumptions, poor data, even worse reporting and bias all the way down. Still, the truth emerges after a time, as it always does.