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Listed below are the requests from EDF received via a phone call regarding U.S. Inventory of Greenhouse Gas Emissions and Sinks data. After each request is the response which is based on publicly available information

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 Request: He wants to understand th e Gas STAR source pie charts that we put in our presentations

- specifically , what are the inventory sources that make up those pie pieces.

o Response: Consult the Energy Section 3 and Sections 3.4 and 3.5 of the Annexes in the 2007 U.S. I nventory found at epa.gov/climatechange/emissions/usgginv_archive.html . The individual source categories and their methane emissions begin on page A

- 143 for natural gas and page A

- 151 for petroleu m in Annex 3. The Annex more thoroughl y covers the methodology used to arrive at the results in Section 3.

 Request: He noted that REC reductions are greater than the entire inventory number for well completions and had a general question about how we de al with that when removing NGS reductions from the inventory . Also wanted to talk generall y about our policy for updating the inventory and why we haven't done that for this source

. o Response: Generally , when estimating emissions from the natural gas indu stry in the U.S. GHG I nventory , CH4 emissions are quantified for each segment of the industry (e.g., production, processing, transmission, distribution) based on a bottom up assessment of different emissions sources. Reductions reported by Gas STAR partner s are subtracted at the segment level. Please see Annex 3.4 in the 2007 Inventory

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o The Inventory

is annually

subject to a peer review, a public review and review b y an international team of experts. Based upon issues identified during these reviews, as well as experience gained in the Natural Gas STAR program, the U.S. strives to continually improve the national Inventory . EPA has undertaken efforts in the past couple of ye ars to update the underl yi ng activity data used in the inventory for a number of sources, including well completions and we are evaluating the appropriateness of incorporating revised data into the National Inventory

. We have communicated preliminary revised emissions estimates to external stakeholders to enable a dialogue among all interested parties about the potential magnitude of emissions from this industry . We have used man y of these revised emissions estimates as the foundation for the anal ys is used to support development of reporting requirements for this industry under the M andatory

GHG Reporting Rule. We also intend to incorporate these revised emissions estimates into our next annual inventory submission to the United Nations Framework Convention on Climate Change.2 Presently , REC reductions reported in the Natural Gas STAR body of work is larger than well completion venting in the inventory on an annual basis. Section 3 of the inventory discusses improvements and future plans for each sector. For the natural gas industry , the planned improvements are discussed on p age 3

- 4 6. For the petroleum industry , the planned improvements are discussed on p age 3

- 51. In a New York Times article published on October 15, 2009, it is mentioned that the EPA is currentl y reviewing and revising methane emissions from U.S. gas wells. As a r esult, the EPA found that the amount emitted by

routine operations at gas wells is approximately 12 times larger than the existing estimate of 9 Bcf. The NYT article can be found here at www.n yt imes.com/2009/10/15/business/energy

environment/15degrees.html#

. EPA has included these re vised emission numbers in the MRR. Specificall y, these new numbers are in the TS D, explained in Appendix B (pages 79 to 85) and us ed in the TSD on page 9 . On page 82, the new 2007 U.S. emissions from well completion and workover venting is approximately

120 Bcf. The TSD can be found here at www.epa.gov/climatechange/emissions/downloads10/Subpart

- W_TSD

022310.pdf

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 Request: Itlooked to him like NGS reductions, which include both oil and natural gas production operations, are only removed from the natural gas portion of the inventory

- wh y is this? I f we were to differentiate the emission reductions associated with the oil sector, what would these be (sources and volumes)?

o Response: The methodology in Annex 3 of the inventory indicates how Natural Gas STAR reductions are applied to the natural gas s ys tems sector.
Natural Gas STAR considers data at the level of the production sector, rather than further dividing its reporting into natural gas and petroleum. At the same time, the inventory considers data at the level of natural gas sy st ems production & petroleum sy stems production. Often a Natural Gas STAR reduction activity

straddles both natural gas sy stems and petroleum sy stems and is therefore inherentl y an overall production sector activity. The Natural Gas STAR production sector reductions are not further deconstructed and are thus applied to natural gas sy stems production sector. For example, vapor recovery units (VRUs) can be installed on both condensate (gas) and storage (oil) tanks, but it is not a Natural Gas STAR reporting requirement to specify which.3

 Request: Do we have a number (%) we can provide publicl y about the amount of gas lost from what comes out of the ground versus what gets to consumers/export?

o Response: This percentage is not a published statistic but can be roughl y calculated from public sources such as the inventory and such as EIA gas production data. It is also important to understand numerical treatment of gas imports and exports, NGL imports and exports, gas reinjected, gas consumed on site, gas unacco unted for due to intrinsic metering errors, and distinguishing between methane versus natural gas data, which all have first order effects on the resulting percentage. An y result using this calculation method would not apply to an y specific site given the top

down nature of the calculation.

 Request: Are changes/updates to the national inventory tracked every

y ear? In particular, he noticed that there were changes to past y ear volumes in the most recent inventory

and wondering wh y those would change retr oactively

. o Response: Yes, for each annual inventory cy cle, the entire time series is considered and updated . The entire time series of 1990 to the present repo rting y ear is updated annually because revised activity

data is applied as it is available. It is not uncommon for EIA or other data sources to issue revised estimates for y ears in the recent past, and such revisions are tracked b y the inventory . Any chan ges in the data sources used are be noted in the executive summary and introduction sections o f the inventory

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