This entails extraction through the distribution and delivery and use of the finished fuel to the ultimate consumer, where the mass values for all greenhouse gases are adjusted to account for their relative global warming potential.
According to a study commissioned by the European Commission's Directorate General for Climate Action, on the Climate Impact of potential shale gas production in the EU, "emissions from shale gas generation are significantly lower (41 per cent to 49 per cent) than emissions from electricity generation from coal" on a lifecycle basis.
In light of the large-scale unconventional gas development operations in the U.S., comprehensive studies have been undertaken to assess the life cycle GHG emissions of unconventional gas in comparison to both conventional gas and other fossil fuels.
According to a study by Carnegie Mellon University, shale gas in Pennsylvania (Marcellus) adds only 3 per cent more emissions to average conventional gas, which is within the uncertainty bounds of the study. The study also found Marcellus shale gas has up to 50 per cent lower GHG emissions relative to coal when used to generate electricity.
Furthermore, the U.S. Department of Energy completed a comprehensive study, released in October 2011, estimating that the 'life cycle' GHG emissions of unconventional natural gas-fired baseload power production is 39 per cent lower than coal per delivered megawatt-hour (MWh).