Development of a Consistent Methodology for Estimating Greenhouse Gas Emissions from Oil and Gas Industry Operations

Understanding the sources and quantities of greenhouse gas (GHG) emissions is critical to developing an emissions inventory that accurately represents various oil and gas industry segment operations. To address this, the American Petroleum Institute (API) formed a Greenhouse Gas Emissions Methodology Working Group. The working group’s objectives were to review, summarize and recommend methodologies for consistent estimation of GHG emissions from oil and gas industry facilities, including exploration and production through refining to product marketing. In a continued pursuit of consistent emission estimation methodologies for the oil and gas industry, the working group is meeting with other protocol development organizations to compare and reconcile different estimation techniques. This paper discusses the process undertaken to compare methodologies used by member companies, national governmental bodies, and intergovernmental experts and to develop a compendium of emission estimation methodologies. It highlights technical, scope, and boundary considerations that play a key role in the final inventory calculations. It presents a general classification scheme for all oil and gas industry devices and operations, while identifying the parameters needed to generate robust estimates of emissions for each equipment category and industry segment. The paper also illustrates ways in which GHG emissions inventory data can be presented and summarizes some of the considerations in designing a GHG emissions inventory.