EPA’s Methane Assumptions Still Way Too High

Last month, the EPA released its latest Greenhouse Gas Inventory, in which the agency significantly lowered its estimate of the amount of methane emissions from natural gas systems. But even with those dramatic revisions, EPA still has a long way to go to get this right.

In its fact sheet about its changes to methane emissions estimates, EPA admits that at least some of its prior methods for collecting emissions data were flawed:

“The study data show that there is more widespread use of emissions control technologies than had been assumed in the previous Inventory.  It also demonstrated that duration of emissions from liquids unloading activities is shorter than had been assumed in the previous Inventory.”

The key word here is “assumed.” While EPA’s current revisions are certainly an improvement and bring its estimates closer to accuracy, there are still a number of assumptions that are simply wrong. Digging deeper, and frankly speaking, it’s difficult to ascertain anything other than a fundamental lack of understanding of the actual development process.

One of the biggest problems with EPA’s latest report is that it still grossly overestimates emissions from well completions, based an inappropriate interpretation of data from its own Natural Gas STAR program.  EPA assumes that the amount of methane that is captured from a “green completion” is the same amount of methane that is released in operations without green completions. Put differently, EPA assumes that operators not using a particular technology or process are just venting methane into the air that would have been captured by it. These faulty estimates have long been criticized, as a report by IHS CERA from 2011 made clear:

“EPA derives its new emissions factor from two slide presentations at Natural Gas STAR technology transfer workshops, one in 2004 and one in 2007.  These two presentations primarily describe methane that was captured during ‘green’ well completions, not methane emissions.  EPA assumes that all methane captured during these green completions would have been emitted in all other completions.  This does not reflect industry practice.” (emphasis added)

Got that? EPA is using data on captured methane to estimate how much methane is being emitted into the air. Try to wrap your head around that one!

EPA also does not properly assess the role of flaring, a process that burns off methane instead of releasing it directly into the air. Since EPA’s Natural Gas STAR program does not consider flaring a recommended technology, it does not provide any data on the process – therefore, EPA simply assumes it isn’t happening. This assumption wholly misrepresents industry practice.  Although states are rapidly moving toward reducing its usage (opting instead for methane capture), flaring is actually used for a whole host of reasons that the EPA is either unaware of or refuses to acknowledge. “Flaring is used not exclusively to limit potential greenhouse gas emissions from completions, but it is also often used due to safety concerns for the protection of industry employees,” according to Devon Energy, which – last we checked – is certainly no stranger to this whole shale development business.

Essentially, EPA assumes that, in states where flaring is not mandated, it’s never used there. This is like assuming that, in states that don’t mandate the use of hybrid vehicles, there are no hybrid cars on the road.

Furthermore, EPA’s prior estimate assumes that flowback duration is twice as long as it actually is in field practice, which in turn greatly distorted EPA’s estimates (again).  More specifically, EPA asserts that the flowback periods for wells that utilize green completions are identical to wells that vent or flare the gas. But according to a report by URS Corporation (see Appendix A in here), the average flowback duration from a well with green completion is 7.7 days, while wells whose emissions are flared or vented take an average of only 3.5 days.  That means the EPA assumes the duration of emissions (and, by extension, the total amount of emissions) from certain wells is more than double what it actually is.

According to EPA, well completions are the largest methane emission source within natural gas systems, which means EPA’s entire data set for this segment of the economy is not only inflated, but perhaps wildly so.

The worst part, however, is that future public policy decisions could be – and perhaps already are – based on EPA’s irresponsible use of data. By extension, the EPA has even justified costly regulations based on emissions that are not even occurring. For example, here’s what the EPA said in its overview of the New Source Performance Standard rule last year:

“In addition, the reductions would yield a significant environmental co-benefit by reducing methane emissions from new and modified wells. Methane, the primary constituent of natural gas, is a potent greenhouse gas – more than 20 times as potent as carbon dioxide when emitted directly to the atmosphere. Oil and natural gas production and processing accounts for nearly 40 percent of all U.S. methane emissions, making the industry the nation’s single largest methane source.” (emphasis added)

And yet, even with one small revision, in which the EPA adjusted its estimates based on better data, the agency was forced to recognize that methane emissions since 1990 have not been increasing, but have actually decreased – even as natural gas production grew exponentially. One can only imagine how significant of a downward revision would be made if the EPA actually corrected all of its errors.

As long as the EPA continues to rely on assumptions about industry activity that are not, in fact, based on actual industry activity, their estimates for methane emissions will remain wrong. The fact that those assumptions result in inflated emissions estimates makes the agency’s conscious decision not to adjust its methods even more troubling.


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