Life Cycle Greenhouse Gas Emissions and Freshwater
Consumption of Marcellus Shale Gas
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Abstract
We
present results of a life cycle assessment (LCA) of Marcellus
shale gas used for power generation. The analysis employs the most
extensive data set of any LCA of shale gas to date, encompassing data
from actual gas production and power generation operations. Results
indicate that a typical Marcellus gas life cycle yields 466 kg CO<sub>2</sub>eq/MWh (80% confidence interval: 450–567 kg CO<sub>2</sub>eq/MWh) of greenhouse gas (GHG) emissions and 224 gal/MWh
(80% CI: 185–305 gal/MWh) of freshwater consumption. Operations
associated with hydraulic fracturing constitute only 1.2% of the life
cycle GHG emissions, and 6.2% of the life cycle freshwater consumption.
These results are influenced most strongly by the estimated ultimate
recovery (EUR) of the well and the power plant efficiency: increase
in either quantity will reduce both life cycle freshwater consumption
and GHG emissions relative to power generated at the plant. We conclude
by comparing the life cycle impacts of Marcellus gas and U.S. coal:
The carbon footprint of Marcellus gas is 53% (80% CI: 44–61%)
lower than coal, and its freshwater consumption is about 50% of coal.
We conclude that substantial GHG reductions and freshwater savings
may result from the replacement of coal-fired power generation with
gas-fired power generation