Greenhouse gas (GHG) emissions management and reporting have emerged as leading environmental policy issue at the state, provincial, regional and federal levels in the United States and Canada. Several new initiatives have been launched or are currently under development in the U.S. and Canada that establish rules to report and track these emissions. In addition, the 110th Congress will begin to focus more intently on the merits and the possible form of a mandatory Federal GHG control program.
The primary GHG emissions attributable to the natural gas transmission industry include Carbon Dioxide (CO2) from combustion sources and methane (CH4) from fugitive emissions (leaks) and venting. Methane emissions are especially important due to the global warming potential (GWP) of methane. GWP is the index that has been developed to compare different GHGs on a common reporting basis. It is a scaling factor that considers the radiative forcing effect of GHG gases on a relative mass basis as compared to CO2. The commonly accepted GWP for methane is 21.
To understand better how potential regulation of GHG might impact natural gas pipeline companies, one must first have a clear picture of the overall US emissions compared to that of the gas transmission industry. Total U.S. GHG emissions in 2005 were 7260.4 million metric tonne (MMT). Of that amount, 6089.5 MMT (80 percent) was CO2 emissions from fuel combustion. Combustion of natural gas accounted for 1170 MMT, 20 percent of the CO2 from combustion and 16 percent of the total GHG emissions.
The natural gas industry had direct GHG emissions of 232 MMT CO2e in 2005, 3.2 percent of the total GHG emissions for the U.S. The transmission and storage segment of the natural gas industry had emissions of 68.8 MMT CO2e, less than 1 percent of the U.S. total. This included 31.9 MMT CO2 from the combustion of “pipeline fuel” and 36.8 MMT CO2e from the release of methane. Thus, direct emissions from pipelines were 68.8 MMT CO2, while the CO2 content of gas throughput was 1170 MMT CO2e.
The gas transmission industry CO2 emissions comprise just 0.5 percent of U.S.GHG emissions. Natural gas systems have a relatively small carbon footprint compared to overall emissions due to their small size and the low carbon content of natural gas. In fact, due to its low carbon content, natural gas can play a significant role in helping to reduce GHG emissions when used in place of other fossil fuels in end use applications such as power generation, commercial or industrial applications.