The goal of hydraulic fracturing is to extract methane (CH4), a natural gas, from the Marcellus Shale for human use. Some of this methane is released into the atmosphere as a result of the process of drilling and transporting natural gas.
Methane is a powerful greenhouse gas; although it stays in the atmosphere for a shorter period of time
than carbon dioxide (CO2), it has 25 times the global warming potential of carbon dioxide over a 100 year period. Gas released during the drilling process is discussed below, but for an in-depth discussion on methane lost in pipelines as fugitive
emissions, see Marcellus Shale Issue 11: Life Cycle Analysis.