Yesterday brought major, new data for conducting life cycle calculations of the comparative carbon emissions from natural gas and coal production.
The API and ANGA released a paper that sharply cuts estimates of methane emissions from gas production, as a result of new data collected from a massive survey of 20 companies and 91,000 gas wells.
http://anga.us/media/249160/anga%20api%20survey%20report%201%20june%20final.pdf. It is the single, biggest source of data about methane emissions ever made available for public inspection and discussion.
A good result of the shale gas battles is the increased focus on getting better data about gas drilling and specifically on how much methane "leaks" or is emitted to the atmosphere from the gas drilling stage all the way to combustion. Broad agreement exists that the data available to estimate methane emissions must be increased and urgently. The urgency springs from the increasing role of natural gas in powering America and the incompleteness of current data.
Despite the data gaps, EPA revised upward by 204% in 2011 its previous 1996 estimates of methane emissions during gas production. The EPA upward revision was based on data gathered in 2010 through its Natural Gas Star program and from about 8,800 or 2% of the nation's gas wells. This data, from 4 sets, was then used to extrapolate emissions for all the nation's more than 440,000 gas wells.
The EPA 2011 upward estimate was made without the benefit of a formal public comment and hearing process that can provide a testing of information and diverse inputs. Once the EPA released last year its upward revision, some observers questioned the accuracy of the data and analysis, while others accepted the new projection.
In his paper, Professor Howarth even pushed forward a range of higher estimates and made other assumptions that inflated the life cycle scoring of emissions from gas. Numerous studies have now been published that rebut the conclusions reached by Professor Howarth.
To fill the data gaps that has been one basis for controversy, the Secretary of Energy's Advisory Board on Shale Gas in its 2011 Report called for the industry to cooperate to provide more complete information to the public as soon as possible.
With that as background, now comes the API and ANGA with its paper based on data from a survey of 18.8% of the nation's estimated total gas wells. The paper focuses on two parts of the gas production process--gas wells liquid unloading and rates of unconventional well re-fracturing--that accounted for 59% of the EPA's 2011 total emission estimates.
The API/ANGA reported data reduces by 86% the EPA emission estimate for gas well liquids unloading that accounted for 51% of the EPA total methane emissions. The paper also reduces by 72% the EPA emission estimate for unconventional well refracturing emissions that accounted for another 8% of the EPA 2011 total methane emission estimates.
On the rate of refracturing of wells, the EPA had estimated that 10% of wells are refractured, while the API data reports the re-fracture rate is 0.7% to 2.3%.
The API/ANGA data on just gas wells liquid unloading and unconventional well re-fracturing would indicate that the EPA 2011 revision is significantly mistaken. Using the API/ANGA data for just the two processes that they surveyed would cut the EPA 204% upward revision to about a 50% upward revision.
Importantly the API/ANGA survey does not provide a basis for adjusting the 41% of total emissions in the EPA 2011 revision that are attributable to processes other than re-fracturing and liquids unloading. Also this survey was done before the EPA final rule on gas air emissions went into effect, and that rule will cut further methane (and other) emissions from gas production.
While API and ANGA themselves state more work must be done to refine and collect more information about methane emissions, this paper sharply boosts the available data and will be undoubtedly carefully reviewed by many observers. Moreover, still more data is being collected by the EPA and others.
All the new data and efforts to collect more will increase public and scientific understanding, and that is a good thing indeed.