Understanding the sources and quantities of greenhouse gas (GHG) emissions is critical to developing an emissions inventory that accurately represents oil and natural gas industry operations. In response to continued interest by its member companies about consistency in emissions estimation, the American Petroleum Institute (API) developed a Compendium of Greenhouse Gas Emissions Estimation Methodologies for the Oil and Gas Industry.TheCompendiumis a result of more than a year long effort by API to screen, evaluate and document a range of calculation techniques and emission factors that could be useful for developing GHG emissions inventories.

In this work all oil and gas industry segments from exploration and production to transportation, refining and distribution were considered. Particular emphasis has been placed on including estimation techniques that depend on knowledge of oil and gas processing simulation, along with a ranking of preferred and alternate methods.

Initially distributed in June 2001 as a "Road-Test" document, API will continue to gather comments from end users and other interested parties for a one-year trial period. API has reached out to governmental, non-governmental and industry associations during the development process to ensure broad peer-review. Additional opportunities will be sought for further discussions prior to finalizing the document in 2002.

This paper will summarize the technical approach adopted for the Compendium and introduce some of the techniques for estimating GHG emissions from specific oil and gas industry operations. It will discuss decisions that need to be made when designing a GHG emissions inventory. It will also present findings from users of theCompendium and feedback from end-user reviews.

The Compendium

The Compendium of Greenhouse Gas Emissions Estimation Methodologies for the Oil and Gas Industry documents a number of currently recognized calculation techniques and emission factors available for developing GHG emissions inventories for oil and gas industry operations. The Compendium was developed to accomplish the following:

  • Assemble an expanse of relevant emission factors for estimating GHG emissions from oil and gas industry activities, based on currently available public documents;

  • Outline detailed procedures for conversions between different measurement unit systems, with particular emphasis on implementation of oil and gas industry standards;

  • Provide descriptions of the multitude of oil and gas industry operations—from exploration and production through refining to the marketing of products, as well as the transportation of crude oil, natural gas and petroleum products—and the associated emissions sources that should be considered;

  • Develop emission inventory examples—based on selected facilities from the various industry segments—to demonstrate the broad applicability of the methodologies; and

  • Outline scope and boundary issues and provide suggestions on how to handle them in constructing an overall inventory.

The Compendiumrepresents a compilation of recognized methodologies for estimating GHG emissions specific to oil and gas industry operations.

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