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EPA methane figures ‘dramatically overstated’

The US Environmental Protection Agency (EPA) has “dramatically overstated” the amount of methane released from shale gas wells, a new study by consultancy IHS Cera claimed.

In the report, Mismeasuring Methane: Estimating Greenhouse Gas Emissions from Upstream Natural Gas Development, IHS Cera claimed the EPA’s method for measuring methane emissions from shale gas wells is incorrect and should not be used to form environmental policies covering shale gas.

The EPA told PEU it is in the process of reviewing the IHS Cera report.

“In fact, the report acknowledges the benefits of capturing air emissions generated in this sector and that many companies are already following the requirements included in EPA's proposal,” it said in an email. 

IHS CERA added that the EPA does not base its calculations on the actual amount of methane emitted during well completions, but on a sample of data captured during well completions. IHS Cera said this means that actual measured emissions from shale gas wells could be significantly lower than EPA estimates.

“The assumptions underlying the EPA’s methodology do not reflect current industry practices,” the report said. “Its estimates of methane emissions are dramatically overstated and it would be unwise to use them as a basis for policymaking.”

Last year, in its Greenhouse Gas Emissions Reporting from the Petroleum and Natural Gas Industry report, the EPA increased its estimates of methane emissions from a variety of natural gas production activities. It created separate categories for conventional and unconventional well completions and upped its estimated emissions for both categories. For conventional gas production, EPA raised its emissions estimate from 0.02 tonnes of methane for each well completion to 0.71 tonnes per completion. And for unconventional wells, the EPA’s methane emissions estimates soared from 0.02 tonnes of methane per completion to 177 tonnes per completion.

Greenhouse gas tally

As a result of the agency’s findings, it more than doubled its 2006 estimates of total upstream greenhouse gas (GHG) emissions from 90.2 million tonnes of carbon dioxide (CO2) equivalent to 198 million tonnes of CO2 equivalent.

However, IHS Cera said the EPA’s findings are flawed because they are based on a simple average of four data points which describe methane captured for sale, rather than methane emitted. IHS Cera also said the EPA assumes that gas produced during completion is vented, rather than flared, which is “at odds with industry practice”.

Advocates for natural gas believe it could be an important fuel in the transition to a lower-carbon energy industry, while shale-gas campaigners frequently cite the environmental benefits of natural gas, which emits around 50% less CO2 than coal when burnt for power generation, as a factor in its favour.

Methane gas, however, is believed to be 25 times more potent than carbon dioxide as a greenhouse gas.

As US shale-gas production increased over the past decade, scrutiny of the industry’s methane emissions has also grown. US shale gas output has soared from just 1.2 trillion cubic feet (cf) in 2007, about 6% of US gas production, to about 17% last year, according to the Energy Information Administration. The Wood Mackenzie consultancy previously predicted that shale gas will comprise 35% of US natural gas production by 2020.

Some studies of shale-gas developments’ environmental impact have suggested that it could be more harmful to the environment than either coal or methane gas.

The American Gas Association (AGA) recently branded a Cornell University report  which claimed life-cycle GHG emissions from shale-gas could be higher than those of coal, both "inaccurate" and "misleading".

Emissions calculations

The report, published in the scientific journal Climatic Change in April, claimed methane emissions from shale-gas production are "at least 30% and perhaps more than twice as great" as those from conventional gas. The study’s publication followed the release of a preliminary study last year. In that report, lead author Robert Howarth, a professor of ecology and environmental biology at Cornell, said shale-gas development emits more GHGs than coal production.

The second Cornell University study, also led by Howarth, said the higher emissions from shale gas can occur at the time wells are hydraulically fractured – as methane escapes from flow-back return fluids – and during drill out following fracturing. The Cornell study further stated that between 3.6% and 7.9% of the methane from shale-gas production escapes into the atmosphere through venting and leaks over the lifetime of a well.

Dave McCurdy, chief executive of the AGA, said at the time that the study was full of "inaccuracies and hyperbole".This view is echoed by IHS Cera, which said the Howarth study makes “similar errors” to the EPA.

“If methane emissions were as high as EPA and Howarth assume, extremely hazardous conditions would be created at the well site,” the report said. “Such conditions would not be permitted by industry or regulators. For this reason, if no other, the estimates are not credible.”

The EPA has proposed tighter regulation of hydraulic fracturing as part of the new Clean Air Act. While IHS Cera said these proposals are already standard industry practice, it did acknowledge they would give more comprehensive documentation of actual GHG emissions from shale-gas and natural-gas development.

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