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In the above three natural gas scenarios, the natural gas is transported through a pipeline,
either to an area that processes LNG (Scenarios 1 and 2) or directly to a power plant (Scenario
3). NETL’s model also includes an option for all LNG steps—from extraction to consumption—
known as an LNG supply chain. After extraction and processing, natural gas is transported
through a pipeline to a liquefaction facility. The LNG is loaded onto an ocean tanker,
transported to an LNG terminal, re-gasified, and fed to a pipeline that transports it to a power
plant. NETL assumed that the natural gas power plant in each of the import destinations already
exists and is located close to the LNG port.
The amount of natural gas ultimately used to make electricity is affected by power plant
efficiency. Therefore, the efficiency of the destination power plant is an important parameter
required for determining the life cycle emissions for natural gas power. The less efficient a
power plant, the more gas it consumes and the more GHG emissions it produces per unit of
electricity generated. For this study, NETL used a range of efficiencies that is consistent with
NETL’s modeling of natural gas power in the United States.
240
NETL also assumed that the
efficiencies used at the destination power plants (in Rotterdam and Shanghai) were the same as
those used in the U.S. model.
5.
Coal Modeling Approach
NETL modeled Scenario 4, the regional coal scenario, based on two types of coal:
bituminous and sub-bituminous. Bituminous coal is a soft coal known for its bright bands. Sub-
bituminous coal is a form of bituminous coal with a lower heating value. Both types are widely
used as fuel to generate steam-electric power. NETL used its existing LCA model for the
extraction and transport of sub-bituminous and bituminous coal in the United States as a proxy
240
See LCA GHG Report at 4 ( citing NETL, Life Cycle Analysis of Natural Gas Extraction and Power Generation).
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for foreign extraction in Germany and China. Likewise, NETL modeled foreign coal production
as having emissions characteristics equivalent to average U.S. coal production. No ocean
transport of coal was included to represent the most conservative coal profile (whether regionally
sourced or imported).
The heating value of coal is the amount of energy released when coal is combusted,
whereas the heat rate is the rate at which coal is converted to electricity by a power plant. Both
factors were used in the model to determine the feed rate of coal to the destination power plant
(or the speed at which the coal would be used). For consistency, this study used the range of
efficiencies that NETL modeled for coal power in the United States. The study also assumed the
same range of power plant efficiencies for Europe and Asia as the U.S. model.
6.
Key Modeling Parameters
NETL modeled variability among each scenario by adjusting numerous parameters,
giving rise to hundreds of variables. Key modeling parameters described in the LCA GHG
Report include: (1) the method of extraction for natural gas in the United States, (2) methane
leakage for natural gas production,
241
(3) coal type (sub-bituminous or bituminous),
242
(4) the
flaring rate for natural gas,
243
(5) transport distance (ocean tanker for LNG transport, and rail for
coal transport),
244
and (6) the efficiency of the destination power plant.
For example, as shown in Table 5-1 of the LCA GHG Report, NETL used two different
241
The key modeling parameters for the natural gas scenarios are provided in Table 5-1 (LNG) and Table 5-2
(Russian natural gas). See LCA GHG Report at 6. The key parameters for natural gas extraction, natural gas
processing, and natural gas transmission by pipeline are set forth in Tables 5-4, 5-5, and 5-6, respectively. See id. at
7-8.
242
The modeling parameters and values for the coal scenarios are provided in Table 5-3. See LCA GHG Report at
6.
243
Flaring rate is a modeling parameter because the global warming potential of vented natural gas, composed
mostly of methane, can be reduced if it is flared, or burned, to create CO
2
. See id. at 7.
244
The distances used for pipeline transport of Russian gas are provided in Table 5-2. See id. at 6.
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ranges for methane leakage rates for Scenarios 1 and 2: from 1.2 to 1.6% for natural gas
extracted from the Marcellus Shale, and from 1.1 to 1.6% from gas extracted using conventional
extraction methods. For Scenario 3 (the Russian cases), however, NETL used a higher range for
methane leakage rates for both the European and Asian locations, in light of the greater pipeline
distance from Russia.
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As the pipeline distance increases, the total methane leakage from
pipeline transmission also increases, as does the amount of natural gas that is extracted to meet
the same demand for delivered natural gas. Notably, as part of the study, NETL conducted a
methane leakage breakeven analysis to determine the “breakeven leakage” at which the life
cycle GHG emissions for natural gas generated power would equal those for the coal Reference
case (Scenario 3).
246
In sum, NETL noted that the LCA study results are sensitive to these key modeling
parameters, particularly changes to natural gas and coal extraction characteristics, transport
distances, and power plant performance.
247
NETL also identified several study limitations
based on the modeling parameters, including: (1) NETL’s LCA models are U.S.-based models
adapted for foreign natural gas and coal production and power generation, and (2) the specific
LNG export and import locations used in the study represent an estimate for an entire region
( e.g., New Orleans representing the U.S. Gulf Coast).
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7.
Results of the LCA GHG Report
NETL states that two primary conclusions may be drawn from the LCA GHG Report.
249
First, use of U.S. LNG exports to produce electricity in European and Asian markets will not
245
See LCA GHG Report at 5.
246
The methane leakage breakeven analysis is described in the LCA GHG Report at 14 and 15.
247
See LCA GHG Report at 5. To ensure that the study results were robust, NETL conducted several side analyses
and sensitivity calculations, as discussed in the LCA GHG Report.
248
The study limitations are described in the LCA GHG Report at 18.
249
NETL’s detailed study results, with corresponding figures, are set forth on pages 8 through 18 of the LCA GHG
Report.
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