The 1996 GRI/EPA Study was completed to identify sources and quantification of U.S. national methane emissions. This data was then used to develop default emission factors for the gas industry. These emission factors are not applicable for all operators and do not address improvements that have since been made in equipment, pipe materials, and O&M practices.
The GTI-OTD final report, Field Measurement Program to Improve Uncertainties for Key Greenhouse Gas Emission Factors for Distribution Sources, was issued on November 10, 2009. This report summarizes the measurement and subsequent fugitive and vented EFs for methane for six Local Distribution Companies (LDCs) from 2007 to 2009. This report reviews the 1996 GRI/EPA Study findings for methane and determines the applicability of these factors. AGA submitted this report on November 19, 2010 alongside AGA's Subpart W questions for EPA.