Understanding Greenhouse Gas Emissions from Unconventional Natural Gas Production

Natural gas comprises almost one-fourth of all energy used in the U.S. New technologies, sometimes referred to as “unconventional” have enabled the production of more natural gas and have expanded domestic energy reserves. Natural gas is generally recognized as a clean-burning fuel source, producing less greenhouse gas (GHG) emissions per quantity of energy consumed than either coal or oil. However, a number of recent studies are raising questions as to the impact of these new production techniques especially hydraulic fracturing on the carbon footprint of natural gas. Current published assessments rely mostly on highly uncertain information provided in EPA’s November 2010 Technical Support Document (TSD) for mandatory GHG reporting from petroleum and natural gas systems, and from information associated with EPA’s Inventory of Greenhouse Gas Emissions and Sinks: 1990-2009. It is becoming increasingly important to document the GHG emissions associated with the different stages of natural gas production in order to demonstrate the continued environmental benefits of natural gas. Therefore, technically sound quantification and assessment of GHG emissions from its lifecycle from production to delivery to end-users is essential. This paper will summarize results from a technical review of the emissions data used to develop EPA’s 2009 national inventory and the 2010 inventory updates. The paper will also discuss a collaborative effort between the American Petroleum Institute (API) and America’s Natural Gas Alliance (ANGA) to gather industry-specific information on emissions from key emission sources associated with unconventional natural gas production.