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November 02, 2012
EPA said to overestimate methane emissions

According to an industry survey, the EPA has overestimated methane emissions from natural gas production by more than 50 percent.  The alleged overestimates are particularly troublesome, note American Petroleum Institute and America’s Natural Gas Alliance (API/ANGA), which sponsored the survey, because they are being used in a series of rules that have wide-ranging ramifications on national natural gas policies both in the United States and globally.

Nonrepresentative

The API/ANGA note that EPA’s estimate of 8.8 million metric tons of methane emissions was based on data gathered from about 8,800 wells—roughly 2 percent of wells covered in EPA’s national GHG inventory—which are, moreover, “confined to specific areas of the country and not representative of the entire country.” 

In contrast, the API/ANGA say their own survey effort gathered activity data from over 20 companies covering nearly 91,000 wells and 19 of the 21 American Association of Petroleum Geologists (AAPG) basins.

Members believe that the API/ANGA survey represents the most comprehensive data set compiled for natural gas operations and, as such, provides a much more accurate picture of operations and emissions than the information EPA has relied on for its emission estimates,” state the API/ANGA.

Liquids unloading

The report indicates that major difference between the EPA and industry estimates center on methane emissions from liquids unloading.  Liquids unloading is a technique to remove water and other liquids from wellbores to improve the flow of natural gas in gas wells.  This activity accounted for 51 percent of total methane emissions—about 4.5 million metric tons—from the natural gas production sector in EPA’s national GHG inventory. 

When applying their own emissions factors to liquids unloading, the API/ANGA estimate methane emissions at about 320,000 metric tons, 93 percent less than the EPA estimate. 

EPA’s sources

The survey report asserts that the EPA lacks a single coordinated and cohesive estimate of well completions and well counts.  The EPA inventory used data from the Energy Information Administration, various state governments, and privately sourced data, such as HPDI, an information services company for the energy industry.  But in putting together its estimates, the EPA did not solicit information directly from industry.  In addition, the Agency did not take into account the “considerable” improvements in equipment and industry practice that have occurred over the past 15 years.  “Under the best of circumstances, EPA had remarkably little information to draw on in determining their new emission estimates,” charge the API/ANGA.

The organizations note that EPA’s methane emissions estimates are being used to question the overall environmental benefits of natural gas and have led to speculation about the role natural gas can play in a clean energy future. 

Click here to read the API/ANGA report.

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