102
Using this framework, NETL developed four study scenarios, identified below. To
compare scenarios, NETL used a common denominator as the end result for each scenario: one
megawatt-hour (MWh) of electricity delivered
to the consumer, representing the final
consumption of electricity. Additionally, NETL considered GHG emissions from all processes
in the LNG supply chains—from the “cradle” when natural gas or coal is extracted from the
ground, to the “grave” when electricity is used by the consumer. This method of accounting for
cradle-to-grave emissions over a single common denominator is known as a life cycle analysis,
or LCA.
237
Using this LCA approach, NETL’s objective was to model realistic LNG export
scenarios, encompassing locations at both a medium and long distance from the United States,
while also considering local fuel alternatives. The purpose of the medium and long distance
scenarios was to establish likely results for both extremes (
i.e., both low and high bounds).
2.
Study Scenarios
NETL identified four modeling scenarios to capture the cradle-to-grave process for both
the European and Asian cases. The scenarios vary based on where the fuel (natural gas or coal)
comes from and how it is transported to the power plant. For this reason, the beginning “cradle”
of each scenario varies, whereas the end, or “grave,” of each scenario is the same because the
uniform goal is to produce 1 MWh of electricity. The first three scenarios explore
different ways
to transport natural gas; the fourth provides an example of how regional coal may be used to
generate electricity, as summarized in Table 9 below:
237
The data used in the LCA GHG Report were originally developed to represent U.S. energy systems. To apply the
data to this study, NETL adapted its natural gas and coal LCA models. The five life cycle stages used by NETL,
ranging from Raw Material Acquisition to End Use, are identified in the LCA GHG Report at 1-2.
103
Table 9: LCA GHG Scenarios Analyzed by NETL
238
238
The four scenarios are set forth in the LCA GHG Report at 2.
239
Yamal, Siberia, was chosen as the extraction site because that region accounted for 82.6% of natural gas
production in Russia in 2012.
Scenario
Description
Key Assumptions
1
•
Natural gas is extracted in the
United States
from the Marcellus Shale.
•
It is transported by pipeline to an LNG
facility, where it is cooled to liquid form,
loaded onto an LNG tanker, and transported
to an LNG port in the receiving country
(Rotterdam, Netherlands, for the European
case and Shanghai, China,
for the Asian
case).
•
Upon reaching its destination, the LNG is
re-gasified, then transported to a natural gas
power plant.
The power plant is located near the
LNG import site.
2
•
Same as Scenario 1, except that the natural
gas comes from a regional source closer to
the destination.
•
In the European case,
the regional source is
Oran, Algeria, with a destination of
Rotterdam.
•
In the Asian case, the regional source is
Darwin, Australia, with a destination of
Osaka, Japan.
Unlike Scenario 1, the regional gas
is produced using conventional
extraction methods, such as
vertical
wells that do not use
hydraulic fracturing. The LNG
tanker transport distance is
adjusted accordingly.
3
•
Natural gas is produced in the Yamal region
of Siberia, Russia, using conventional
extraction methods.
239
•
It is transported by pipeline directly to a
natural gas power plant in either Europe or
Asia.
The pipeline distance was
calculated based on a “great circle
distance” (the shortest possible
distance between two points on a
sphere) between the
Yamal district
in Siberia and a power plant
located in either Rotterdam or
Shanghai.
4
•
Coal is extracted in either Europe or Asia.
It is transported by rail to a domestic coal-
fired power plant.
This scenario models two types of
coal widely used to generate
steam-electric power: surface
mined sub-bituminous coal and
underground mined bituminous
coal. Additionally, U.S. mining
data and U.S.
plant operations
104
In all four scenarios, the 1 MWh of electricity delivered to the end consumer is assumed to be
distributed using existing transmission infrastructure.
3.
GHGs Reported as Carbon Dioxide Equivalents
Recognizing that there are several types of GHGs, each having a different potential
impact on the climate, NETL normalized GHGs for the study. NETL chose carbon dioxide
equivalents (CO
2
e), which convert GHG gases to the same basis: an equivalent mass of CO
2
.
CO
2
e is a metric commonly used to estimate the amount of global warming that GHGs may
cause, relative to the same mass of CO
2
released to the atmosphere.
NETL chose CO
2
e using the
global warming potential (GWP) of each gas from the 2013 Intergovernmental Panel on Climate
Change (IPCC) Fifth Assessment Report (AR5) (IPCC, 2013). The LCA GHG Report applied
the respective GWPs to a 100-year and a 20-year time frame.
4.
Natural Gas Modeling Approach
NETL states that its natural gas model is flexible, allowing for the modeling of different
methods of producing natural gas. For Scenario 1, all natural gas was modeled as
unconventional gas from the Marcellus Shale, since that shale play reasonably represents new
marginal gas production in the United States. For Scenarios 2 and 3, the extraction process was
modeled after conventional onshore natural gas production in the United States. This includes
both the regional LNG supply options that were chosen for this study (Algeria for Europe and
Australia for Asia) and extraction in Yamal, Siberia, for pipeline transport to the power plants in
Europe and Asia.
were
used as a proxy for foreign
data.