Life cycle greenhouse gas emissions of Marcellus shale gas

Abstract

This study estimates the life cycle greenhouse gas (GHG) emissions from the production ofMarcellus shale natural gas and compares its emissions with national average US naturalgas emissions produced in the year 2008, prior to any significant Marcellus shaledevelopment. We estimate that the development and completion of a typical Marcellusshale well results in roughly 5500 t of carbon dioxide equivalent emissions or about 1.8 g CO2e/MJ of gas produced, assuming conservative estimates of the production lifetime of a typical well.This represents an 11% increase in GHG emissions relative to average domestic gas (excludingcombustion) and a 3% increase relative to the life cycle emissions when combustion is included.The life cycle GHG emissions of Marcellus shale natural gas are estimated to be 63–75 g CO2e/MJ of gas produced withan average of 68 g CO2e/MJ of gas produced. Marcellus shale natural gas GHG emissions are comparable tothose of imported liquefied natural gas. Natural gas from the Marcellus shale hasgenerally lower life cycle GHG emissions than coal for production of electricity inthe absence of any effective carbon capture and storage processes, by 20–50%depending upon plant efficiencies and natural gas emissions variability. There issignificant uncertainty in our Marcellus shale GHG emission estimates due to eventualproduction volumes and variability in flaring, construction and transportation.