The Impact of Using
LNG-Derived Natural Gas in the
South Coast Air Basin
January 2006
1
Background
• Future natural gas demand in the United States
will rise
• Traditional natural gas sources are increasing in
cost and new supplies will not meet demand
• Regassification of LNG imports is commercially
feasible and economically beneficial
• Imported LNG typically has higher heat content
(HHC) than current NG in the South Coast
– More ethane, propane, butane
– Less N2, CO2, and O2
2
Air Quality Background
• South Coast is a severe-17 ozone non-attainment
and serious PM10 non-attainment area
– NOx is an ozone and PM10 precursor
– 2003 AQMP: reduce NOx 48% from 2003 to 2010
• Combustion of HHC (e.g. LNG-derived) NG may
increase NOx and CO emissions from some types
of equipment
• 2003 AQMP control measure MSC-07 proposes
upper limit on heating value
– Condensing (e.g. extracting) out higher hydrocarbons
– Adding inerts (e.g. N2, CO2)
• Question: what would be the impact of HHC NG
on South Coast emissions and air quality?
3
Impact Analysis Approach
• Review relevant emission inventories for SCAB
natural gas combustion emission categories
– Compare to overall SCAB inventory
• Review equipment test data comparing the
emissions from HHC gas combustion to base gas
combustion
• Apply emission ratio to SCAB stationary source
natural gas combustion inventory categories and
assess the inventory impact
• Apply applicable SCAQMD regulatory limits,
where possible – assess inventory impact
4
SCAB Emission Inventory
tons/day
1200
1049
1000
807
800
600
454
400
308
200
15
5
53
0
VOC
CO/10
NOx
Natural Gas Combustion
63
2
SOx
7
PM10
Total
Source: CARB, 2003 Inventory for SCAB, anthropogenic only
5
Contributions to 2003 NOx Inventory
All Mobile
90%
Remaining
Sources
2%
NG-Industrial
3%
*
Other Fuel
Combustion
3%
1049 tons/day NOx
NG-Residential
2%
Stationary Source Combustion Sources
* Other fuels include diesel, propane, distillate oil, LPG, gasoline, etc.
6
South Coast Energy from Different Fuels
Gasoline
47%
Diesel
8%
Natural
Gas
45%
Total energy consumed: 1,723,000 Bbtu/year
Based on reported fuel consumption from 2000 Fuel Tax Report, SoCalGas
7
HHC Emission Studies
• Initial SoCalGas sponsored tests of gas-fired
equipment (2005 Final Report, SoCalGas)
– Tests used NG with higher heating values and Wobbe
numbers, compared to base gas
– Wobbe = heating value / square root of specific gravity
– Equipment was NOT modified / adjusted for HHC gas
• Gas #6 (HHV=1100, Wobbe=1400) results were used
in the analysis
– Gas #3 (HHV=1150, Wobbe=1430) used for residential
forced air heating units since equipment was not tested on
Gas #6
– 2003 LNG Research Study – Phase I for IC engines
8
NOx Test Results for Base and HHC Gas
(Gas #6)
*
CHART 5: NOx Test Results for Base and HHC Gas (Gas 6)
Emissions (ppm @ 3% O2)
140
133
NOx Base Gas Emissions
NOx Gas Six Emissions
120
111
101
Emissions (ppm @ 3% O2)
100
90
89
88
80
66
64
60
54
39
40
20
52
16
3
3
7
10
ICE
0
Commercial
Water Boiler
Horizontal
Condensing
FAU
Legacy Water
Heater
ICE
Ultra Low NOx
Steam Boiler
Wall Furnace
Instantaneous
Water Heater
Commercial
Conveyor
Broiler
Note: For HCFAU,
2003Category
LNG Study Report results (after controls)
Source
*
* Gas #3
* results
* used. For ICE,
ENVIRO
9N
* The test results which were applied to Scenario 1 and 2 test results.
Emission Impact Analysis
•
•
•
•
Total Basin natural gas usage: 2.04 Bcf/day
Assessed the emission impact from two
scenarios:
1. Replacement of 1 Bcf/day with HHC gas
2. Replacement of 0.5 Bcf/day with HHC gas
Adjusted the emissions from each source
category with related test results
Assessed impact for the effect of certain
SCAQMD rules
10
Applicable Test Results
Tested Equipment1
Source Category
2003 NOx Emissions
(tons/day)
Internal Combustion All ICEs
Engine2
6.9
Commercial Water
Boilers
All boilers categories
7.8
HCFAU3
Residential, service and
commercial space heating
10.6
Legacy water heater Residential, service and
commercial water heating
10.7
None available
(no adjustment)
16.9*
gas turbines, oven heaters,
in-process fuel, other
* 5.8 tpd from residential (cooking and other)
and 3.3 tpd from gas turbine engines generally 1.
2.
in RECLAIM
3.
LNG study April 2005, except as noted
LNG Research Study – Phase 1, 2003
Gas #3 results used
11
Rule Adjustments
• Almost all in basin sources that emit over 4
tons/day of NOx are in RECLAIM
– Net Basin change in emissions from those
sources would be zero
• RECLAIM applied to:
– All electric utilities, co-generation, oil / gas
production, petroleum refining, and industrial /
manufacturing categories
• No rule or permit limits applied to any other
categories
12
NOx Impact of HHC Gas
CHART 8b: NOx Emission Impacts for HHC Gas Scenarios
1200
NOx tons/day
1044.8
Emissions (ton/day)
1000
2003 SCAB NG Combustion Emissions
Scenario 1 (1 Bcf HHC Gas)
Scenario 2 (0.5 Bcf HHC Gas)
2003 Total Emissions
800
600
400
200
52.9
54.1
53.5
0
Total 2003 NOx Emissions
Test-adjusted NG emissions with RECLAIM impact
ENV I RO N
13
Seasonality
• Ozone season is summer/early fall
• Emissions are seasonal
– Greater electrical generation in summer
• Sources under RECLAIM, BACT
– Residential emissions reduced in summer
• No space heating July through October
• Reduced water heating needs
• Pool heaters not used during hottest periods
– Commercial/Industrial – less seasonality
14
VOC Emission Impacts
Chart 2: VOC Test Results for Base and HHC Gas (Gas 6)
400
Emissions (ppm @ 3% O2)
Base Gas
LNG
350
Emissions (ppm @3% O2)
394.0
300
232.8
250
230.0
215.0
200
150
100
50
76.8
37.5
31.2
22.8
3.8
10.3
3.3
1.6
1.2
1.6
0
Ultra Low
NOx Steam
Boiler
Legacy Floor Instantaneous Commercial
Furnace
Water Heater Water Boiler
Wall Furnace
ICE
Low NOx
Steam Boiler
Sourcereduction
Category
Analysis shows a 0.8 ton/day
for Scenario 1
15
Latest SCAQMD Modeling Analysis
• Black lines are ozone
episode isopleths
• Colored lines are
annual average PM2.5
isopleths
 Ozone decreases as
NOx increases
 PM2.5/PM10
insensitive to NOx
changes
 Ozone and
PM2.5/PM10 decrease
as VOC decreases
Source: SCAQMD, 2007 AQMP Technical Advisory Group, 12/7/05
16
Other Air Quality Impact Issues
• NOx emissions from residential and service /
commercial sources are spread throughout the SCAB
– For example, emissions changes in San Fernando Valley
do not affect peak Inland Empire areas
• Weekday/Weekend Effect
– Natural gas usage 13% higher on weekdays, but 65% of
ozone exceedences occur on weekends
• Uncertainty in mobile source emissions greater than
potential NOx increase due to HHC combustion
• Air quality modeling possible, but may be insensitive to
such small emission changes
 Ozone and PM2.5/PM10 air quality impacts expected
to be negligible, with impact potentially beneficial
17
Preliminary Conclusions
•
0.11% annual increase in NOx emissions if 1.0
Bcf/day of LNG-derived natural gas is used
– 0.06% increase for 0.5 Bcf/day
– Does not account for reductions from proper tuning
– Does not account for non-RECLAIM emission limits
• Ozone and PM10 air quality impact expected to be
negligible, with impact potentially beneficial
• Given the small potential impact, other more costeffective, local approaches should be considered
– Expanded use of natural gas instead of higher
emitting diesel and gasoline
18