Cornell University researchers say
that natural gas pried from shale formations is dirtier than coal in the short
term, rather than cleaner, and "comparable" in the long term.
That finding -- fiercely disputed by
the gas industry -- undermines the widely stated belief that gas is twice as
"clean" as coal in terms of greenhouse gas emissions. The gas
industry has promoted that concept as a way for electric utilities to prepare
for climate change regulations by switching from coal-fired plants to gas.
But if both gas and coal are
considered plentiful and cheap, utilities would have little incentive to
The lead author of the study, Robert
Howarth, had previously stated the idea that shale gas production emits more
greenhouse gases than coal production (ClimateWire, April 2, 2010). But now it is
being published in a peer-reviewed scientific journal.
"Compared to coal, the footprint
of shale gas is at least 20 percent greater and perhaps more than twice as
great on the 20-year horizon and is comparable when compared over 100
years," states a pre-publication copy (pdf) of the study, which is slated to
be published in the journal Climatic Science and originally obtained by The
Howarth and his fellow Cornell
professors, Renee Santoro and Anthony Ingraffea, found the process of
"hydraulic fracturing," which is required to extract gas from shale,
emits enough methane to make it dirtier than coal. Methane is a greenhouse gas
that is more potent than carbon dioxide but does not last as long in the
But industry representatives
disputed numerous points in the study, saying the researchers used
unconventional methodologies to reach their conclusion.
"These guys weren't about to
let a silly thing like data get in the way of a good story," said Chris
Tucker, spokesman for the industry group Energy in Depth, which was founded by
drillers to fight federal regulation of fracturing.
"Reading the paper, it's tough
not to get the impression that the fix was in from the start, that they set out
with a series of conclusions and then just worked backward from there, moving
the parameters in and out as needed to get where they wanted to go."
Howarth said that the findings were
not predetermined and said the study's credibility has been bolstered by peer
"In fact, we came up with two
things that surprised me. First, I expected the indirect CO2 emissions from
trucks moving frac water, the compressors, the drills, etc., to be greater than
we found. They are actually pretty small, when you add up all the numbers. And
second, the influence of methane is greater than I expected," Howarth said
in a response to Greenwire. "The data tell the story. Unfortunately
for Mr. Tucker, the statements that industry has liked to make have never been
based on data."
In hydraulic fracturing, drillers
inject chemical-laced water and sand underground under extremely high pressure
to break apart rock formations and release gas. The method has been used for
years to coax more oil and gas from wells. But it is essential to obtaining any
gas from dense shale formations.
And a great deal of methane escapes
during the process, according to the Cornell study. The professors said it
escapes from flow-back return fluids and during drill-out following the
Industry has criticized Howarth
before. Energy in Depth's parent group, the Independent Petroleum Association
of America, wrote to U.S. EPA in September seeking to prevent him from being
selected as a peer reviewer for an agency study of fracturing (E&ENews PM, Sept. 29, 2010).
The Cornell trio are not the only
ones questioning the climate change reductions from natural gas and fracturing.
In January, the news organization ProPublica reported that new research
released by EPA shows that natural gas production could be 25 percent cleaner
than coal, or less, rather than twice as clean (Greenwire, Jan. 25). The report gave similar
reasons as the Cornell study -- methane emissions from the full life cycle of
gas production are taken into account.
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