Yes, We In Fact Do Know How to Accurately Measure Methane

Methane – the primary component of natural gas – has been in the news a good bit this week, primarily in the context of the role it is expected to play (or not play?) in helping states comply with new power plant rules issued by the Obama administration and EPA. But there’s another big methane story that’s making the rounds, one from The New York Times posted on Monday that basically argues everything we know about measuring methane leakage rates is wrong – because, as it turns out, the highly sophisticated equipment we’ve always used to do that apparently doesn’t work.

It’s an interesting and provocative assertion, to be sure, and the fact that the claims are being made by a retired consultant and current professional firefighter who lives in North Carolina makes it all the more interesting and provocative. The consultant is a guy named Touché Howard, and his core argument, articulated in a research paper that appeared in the journal Energy Science & Engineering this week, is that since the instruments widely used to detect methane emissions today have the potential to fail, the landmark study released 2013 by researchers at the University of Texas (UT) and the Environmental Defense Fund (EDF) can’t be trusted. Oh, and it’s probably the case that emissions are a lot higher than we think.

If you haven’t been following the methane debate that closely this summer, you might think this is a new story. But truth is, Howard actually already released a similar study earlier this year that brought up exactly the same issues regarding the equipment on which he trains most of his attack: the Bacharach Hi-Flow Sampler (BHFS).

The questions raised in that previous report were fully addressed in a public scientific forum by the UT/EDF researchers.  In a piece published in March 2015 in Environmental Science and Technology, the UT/EDF researchers explained that they used multiple instruments and conducted rigorous testing of the instruments both in the laboratory and in the field before it was used.   They also used infrared video camera scans in conjunction with the instrument to obtain an even more thorough reading of methane emissions.  In other words, these guys really ran this stuff through the wringer.

Of course, we don’t actually expect you to read any of these comments – that’s why you have us around!  So let’s go through quick and highlight some of the relevant and compelling responses Dr. Allen, the lead researcher of the UT/EDF study, and his colleagues have put forth over the past several months to Mr. Howard:

“To assess whether this potential crossover failure impacted measurements in Allen et al., or our earlier work employing the instrument, we conducted laboratory testing, field testing, and additional analyses of field data.

Laboratory Testing: As documented in the Supporting Information for Allen et al., prefield deployment laboratory testing of the sampler used in our work (referred to here as the University of Texas (UT) HiFlow sampler) demonstrated successful crossover between the two measurement modes for methane and a wet gas surrogate (70.5% methane by volume).

Field Testing: The study team participated in a two day field test of several HiFlow samplers. Participants in the field testing included our team, the commenter, a consulting firm, an instrument provider and consulting firm, and a natural gas producer. During this field test, the UT HiFlow sampler successfully crossed-over on sites with methane concentrations in the produced gas ranging from 77%−91%. Over 2 days of testing, the UT HiFlow sampler crossed-over successfully in all but one test; that test occurred at a site with a produced gas containing 91% methane. Subsequent examination of the instrument indicated that it had lost calibration after losing power, then being restarted by personnel not on our study team. The sampling protocol in Allen et al. required a calibration check each time the HiFlow sampler was turned on. Once the calibration protocol was followed, the HiFlow sampler resumed proper operation.

Additional Analysis of Allen et al. Data: Infrared (IR) video camera scans were taken on some sites during field work for Allen et al.,3 including for 118 of the 305 pneumatic controllers (39%) sampled in that work. These infrared camera scans were done immediately upon arrival at the site and thus were not exactly contemporaneous with the UT HiFlow measurements…Overall, the comparison with IR camera data suggests that the UT HiFlow sampler was capturing the emissions from pneumatic controllers in its measurements.”

In the New York Times article, Dr. David Allen explains the process this way:

 “There may be issues with some of these instruments, but we tested our instruments pretty thoroughly and when we went out into the field we had multiple instruments, all of which gave us information,” he said. Alternate measurement methods were used at some sites, he said, and “we didn’t see any evidence that we were missing any large numbers.”

It’s also worth pointing out that while so-called bottom-up studies using direct field measurements of have found low emissions, the most recent studies using flyovers – when emissions are measured by instruments in aircrafts – have also found very low emissions.  One example comes from another EDF-sponsored study, Lyon et al, which takes measurements in aircrafts over the Barnett Shale and finds very low emissions:

 “Barnett Shale O&G wells produced 5.6 Bcf day-1 natural gas and 54.5mbl oil and condensate day-1 in October 2013.  Assuming a constant production rate and weighted average gas composition of 88.5% methane by volume, our O&G emission estimate is equivalent to 1.2% (1.0-1.4%) of gas production. If oil production site emissions (4% of O&G total) are excluded then the natural gas leak rate decreases to 1.1% (1.0% – 1.3%).  (p. 8153; emphasis added)

Researchers from the University of Colorado at Boulder and the National Oceanic and Atmospheric Administration (NOAA) also recently released a report, which uses measurements from flyovers.  It found that methane leakage rates from three major shale developing regions are in line with EPA’s leakage estimate of 1.1 percent (of production).  Specifically, the researchers found emissions in the Haynesville in Louisiana and Texas to be between 1.0 and 2.1 percent; in the Fayetteville in Arkansas to be between 1.0 and 2.8 percent; and in the Marcellus to be between 0.18 and 0.41 percent.  Importantly, the areas collectively represent over half of total U.S. shale production.  From the report:

“The climate impact of CH4 loss from shale gas production depends upon the total leakage from all production regions. The regions investigated in this work represented over half of the U.S. shale gas production in 2013, and we find generally lower loss rates than those reported in earlier studies of regions that made smaller contributions to total production. Hence, the national average CH4 loss rate from shale gas production may be lower than values extrapolated from the earlier studies.” (emphasis added)

As EID has noted on a number of occasions, one of the obvious drawbacks and limitations associated with evaluating methane concentrations from flyovers is that there is often a lot of uncertainty about where exactly the methane is coming from.  Evaluating what percentage of the methane originates from oil and gas production versus other sources, such as agriculture, coal production, or natural seeps, often involves Rube Goldberg-esque modeling exercises and hypothesizing.  Yet, even taking other sources of methane into account, the researchers still found exceedingly low methane leakage rates.

In the end, the only conclusion Howard really comes to in his “new” study is that there’s a possibility that the instrumentation might not work properly if it is not used properly.  That’s it.  In response, UT/EDF researchers have made it abundantly clear that they went above and beyond from a process and methodological standpoint to ensure that the instruments were tested and deployed in the proper manner.

A “new” study that raises already answered questions is essentially a distraction from the only real question that matters here, and that’s this: What’s the actual leakage rate? Good news is, we actually have some pretty good answers to that, thanks in large part to a number of good (if not always perfect) studies that have been released on the topic. Those studies tell us that methane leakage rates are low, and continue to drop. And good thing for that, considering that literally no one supports the imperative of detecting, capturing and ultimately selling more methane than the folks who actually do that work for a living.


Post A Comment