American Oil and Gas Reporter - July 2018 - 136

METHANE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FROM PAGE 35
conditions' such as malfunctions and large
leaks. But this rationale ignores flaws with
facility-level measurements that can lead
to overestimating emissions," EID states.
Lack Of Collaboration
Regarding the facility-level studies
EDF uses as the basis for its emissions
estimates, EID says the report's supplementary information document acknowledges that sites reported to be sampled
were done so on a quasi-random basis
without advance operator knowledge.
"This again flies in the face of NAS recommendations," EID charges.
EID calls the lack of industry participation surprising, considering that EDF
frequently has touted its past methane
research as being collaborative. EID says
EDF justifies excluding industry by contending operators are likely to fix problems
or be more careful to avoid errors if
warned measurement teams are about to
arrive, thereby biasing the data.
"Not only does EDF fail to provide a
single reference to back this claim, but
none of the five co-authors of this report,
who were also the lead authors of past
EDF methane research that was conducted
in close concert with industry, have ever
publicly claimed any bias," EID counters.
"EDF's assertion appears to be purely
speculative in nature and an excuse to
use these studies (to) exaggerate national
emission estimates."
Missing Alternative
EID reveals that the supplemental materials document for EDF's report includes
an alternative national emissions estimate
based on source-based reports, several
of which are past EDF studies. This alternative estimate finds the national
methane leakage rate is 1.4 percent, which
EID notes not only aligns with past EDF
studies, but also the EPA Greenhouse
Gas Inventory.
"Remarkably, the data from this alternative estimate isn't mentioned in the
actual report, even though EDF notes
that an extensive list of source-based
studies featured in the supplemental data
has 'dramatically improved understanding
of the sources and magnitude of CH4
emissions from the industry's operations,''
EID reflects.
EID says EDF also argues that its "primary" estimate-again based solely on facility-level studies-is in line with aggregate
average emissions found in nine top-down
studies based on emissions largely collected
from aircraft measurements.
"But this claim is a stretch on a couple

levels," EID replies. "First, the cumulative
data from the TD studies show a national
leakage rate of 1.8 percent. Although that
is within the (EDF) study's 0.5 percent
uncertainty range, TD studies typically
overestimate oil and gas methane emissions
because measurements from such studies
are difficult to attribute to specific sources.
"In other words," EID goes on, "it is
highly implausible that 'bottom-up'
methane emission estimates would be
higher than TD estimates."
EID backs this by pointing to a National
Oceanic and Atmospheric Administration
report that says TD studies likely overestimate emissions by mischaracterizing
episodic emissions as normal emissions.
"Such emissions also can be detected
and mischaracterized using facility-level
measurements. So it's not surprising this
EDF study tries to discredit that NOAA
study," EID comments.
Inflated Estimates
EID says another factor that can lead
to facility-scale measurements overestimating actual emissions is that such methods are conducted in the daytime and,
thus, can capture emissions from episodic
events such as liquids unloading, which
then are extrapolated inaccurately as if
they are constant. This is confirmed by a
peer-reviewed NOAA study of the Fayetteville Shale EID says it covered last year.
Perhaps anticipating that 2017 study
would be used to call its new report's
conclusions into question, EID says EDF
attempts to discredit the NOAA study by
arguing, "(T)here is no reason to expect
daytime bias in the kinds of abnormal
operating conditions that are thought to
characterize high-emitting production
(and gathering) sites, which operate continuously. In fact, it is plausible that abnormal emissions actually could be higher
at night because they are less likely to be
found and corrected in the absence of
operators."
This claim is contradicted directly by
the following EDF statement, EID counters, which acknowledges the validity of
the NOAA Fayetteville study, but claims
it isn't relevant to other basins:
"O/NG emissions are systematically
higher during daytime hours. This situation
was reported for the Fayetteville Shale,
but appears to be unique because the
effect is caused by manual liquids unloading, which represents a much higher
fraction of total production emissions
than in any other basin."
The fact is, EID differs, events such
as liquid unloading are common in other

136 THE AMERICAN OIL & GAS REPORTER

basins, and downwind measurements,
such as those used as the basis for the
EDF analysis, do tend to be higher because
they are conducted during the day.
Benefits Remain Clear
Finally, EID says, the EDF report claims
the level of oil and natural gas emissions
it estimates is having the same climate
impact as coal in the short term (20-year
time span) when combined with carbon
emissions from natural gas combustion.
The report states, EID quotes, "Indeed,
our estimate of CH4 emissions across the
supply chain, per unit of gas consumed,
results in roughly the same radiative forcing
as does the CO2 from combusting natural
gas over 20 years. Moreover, the climate
impact . . . roughly equals that from the
annual CO2 emissions from all U.S. coalfired power plants operating in 2016."
Nevertheless, EID insists, it is essential
to note that natural gas maintains clear
climate benefits over other traditional
sources even at much higher leakage
rates than purported by the EDF study.
The group points to a hydraulic fracturing issues brief published by Washington-based Resources for the Future,
which says, "If more than 4 percent of
the natural gas produced in the United
States is emitted as methane (rather than
being burned), the climate benefits of
gas's displacement of coal disappears
over 20 years. If the time frame is 100
years, the leakage rate would have to be
more than 8 percent for natural gas to be
a climate loser relative to coal."
All of which leads EID to conclude,
"This EDF study spends an inordinate
amount of time explaining why its conclusions are plausible rather than explaining how it reached its conclusions. And
it's clear why: Once one digs into the report's supplemental information, it's clear
the conclusions are based on pretty shaky
assumptions and speculation that runs
counter to established and/or recommended best practices for such research.
"At the end of the day, the EDF study
is not only an outlier in terms of the
overall body of methane research, it's
also an outlier with regard to EDF's collective methane research, which has consistently found leakage rates between 1.2
and 1.5 percent. In the meantime, EPA
data show oil and gas methane emissions
have declined 14 percent since 1990,
even as oil and natural gas production
have skyrocketed."
The full EID response may be found
at www.eidclimate.org/five-things-knowabout-new-edf-methane-study/.
r

http://www.eidclimate.org/five-things-know-about-new-edf-methane-study/ http://www.eidclimate.org/five-things-know-about-new-edf-methane-study/

American Oil and Gas Reporter - July 2018

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