United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-84/091 Apr. 1985
<&ERr\ Project Summary
Status Report on the
Development of the NAPAP
Emission Inventory for the 1980
Base Year and Summary of
Preliminary Data
Douglas A. Toothman, John C. Yates, and Edward J. Sabo
The report documents the compilation
of a 1980 emissions inventory for use in
the National Acid Precipitation Assess-
ment Program (NAPAP). The current
inventory (Version 3.0) contains point
source data for over 50,000 plants (with
over 201,000 emission points) and area
source data for the 3,069 counties in
the 48 contiguous states and the District
of Columbia. Emissions of SO2, NOX,
VOC, CO, and participates are included
in the inventory, but the report focuses
on SO2. NOx, and VOC which are of
primary interest for acid deposition
research. NAPAP Version 3.0 emissions
of SO2. NO,, and VOC are 27.1, 23.7,
and 23.3 million tons per year, respec-
tively. Summaries of emissions by
source category, geographic region,
state, fuel type, season, and stack height
range are presented along with emission
density maps and fuel use summaries.
Emissions in the NAPAP data base are
in reasonable agreement with Work
Group 3B and EPA/OAQPS emissions
trends estimates. NAPAP fuel use data
show reasonable agreement with fuel
values in DOE's State Energy Data
Report. Version 3.0 of NAPAP repre-
sents a detailed inventory of emissions
on a national scale; however, it should
be noted that additional improvements
are planned.
The full report is an initial version of
the 1980 NAPAP emissions inventory.
While it describes the methods used to
compile the 1980 NAPAP emissions
inventory and gives preliminary results
from applying those methods, several
improvements to the methods and data
used are currently in process. Other
changes can be anticipated as the need
or opportunity for changes is identified.
Thus, it is important to emphasize the
less-than-final nature of this report and
the many numbers it contains. The
report is being circulated to facilitate
the critique process, not because it is a
completed document suitable for un-
critical use. Any use outside of these
bounds should be considered with the
utmost caution.
This project was administered by the
USEPA, with funding from NAPAP's
Task Group B—Man-Made Sources. The
report has been reviewed and approved
for publication consistent with the
above conditions by appropriate EPA
and NAPAP personnel.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC. to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
A detailed 1980 base year emission
inventory has been developed by Task
-------
Group B of the Interagency Task Force on
Acid Precipitation to support the needs of
the National Acid Precipitation Assess-
ment Program (NAPAP). This report sum-
marizes the current version (3.0) of the
NAPAP inventory.
Development History of
Version 3.0
The NAPAP data were developed start-
ing with information from EPA's National
Emissions Data System (NEDS). These
data have been improved by incorporating
the latest available emission factors,
substitution of data from the Northeast
Corridor Regional Modeling Project and
other more representative of 1980 NEDS
data, cross-checking the electric utility
data with DOE's data compiled by E. H.
Pechan and Associates, cross-checking
data with information from the U.S./
Canada Work Group 3B report, and adding
county centroid latitude and longitude for
sources with missing or incorrect Uni-
versal Transverse Mercator (UTM) coordi-
nates. The NAPAP data are stored in the
Emission Inventory System (EIS) format
on EPA's IBM computer at Research
Triangle Park, NC. The data consist of
point source data for 50,200 establish-
ments (with over 201,000 emission
points) and area source data for each of
3,069 counties included in the 48 con-
tiguous states of the U.S. and the District
of Columbia. Currently, NAPAP reports
emissions of S02, NO,, VOC, particulates,
and CO. It is planned to add sulfates,
ammonia, and other pollutants in the
future. This report focuses on emissions
of S02, NO*, and VOC which are of
primary interest for acid deposition re-
search.
Emissions Summary and
Comparison
Tables 1-7 summarize national emis-
sions of SO2, NOX, and VOC from Version
3.0 of NAPAP. Regional totals of emis-
sions and state totals of point and area
source emissions are also shown. More
detailed emissions summary information
is given in report Chapter 2, including
emissions by state, emissions by season
and stack height ranges, and emission
density maps.
The S02 emissions are dominated by
electric utilities, primarily from coal-fired
generating stations in the eastern U.S.
Other significant source sectors include
industrial combustion (again, mostly from
coal), non-ferrous smelters (primarily
copper smelters in the southwestern
U.S.), and other industrial processes
(largely petroleum refining, chemicals,
cement plants, and pulp mills). For NO,,
the largest sources are transportation
(mostly highway vehicles), electric util-
ities, and industrial combustion. Electric
utility emissions result primarily from
coal combustion, but a significant portion
also results from natural gas combustion.
For industrial sources, the largest portion
of NO, emissions comes from natural gas
combustion. For VOC, emissions result
largely from transportation (again, primar-
ily highway vehicles), other industrial
processes, and miscellaneous sources.
Principal industrial process sectors in-
clude chemicals, petroleum refining,
petroleum transportation and storage,
and a wide variety of activities involving
organic solvent consumption. Miscella-
neous sources include additional organic
solvent use not accounted for by point
sources in NAPAP, retail gasoline service
stations, and forest wildfires.
The geographic breakdown of SOa
emissions shows that EPA Regions 4 and
5 are the largest contributors, accounting
for about 53% of the national total. Region
3 also has significant emissions, with a
14% contribution. The eastern 31 states
account for over 82% of nationwide
emissions. For NO,, RegionsA 5, and 6
are the highest emitters, with 60% of the
national total. Region 3 is again next, with
10% of total emissions. Although not as
great a contribution as for SOz, the
eastern 31 states still account for about
64% of national emissions. Regions 4, 5,
and 6 are also responsible for the greatest
amount of VOC emissions, with 54% of
the national total. The eastern 31 states
account for 66% of the nation's emissions,
which is about the same as for NO,. Thus,
emissions of all three pollutants are
concentrated in the east, especially those
of SO2 Substantial variability in SO2
emissions exists between regions, with
less difference for NO, and even less for
VOC.
The relative importance of point versus
area source emissions varies for each of
the three pollutants. Point sources con-
tribute about 92% of national SOa emis-
sions. For NO,, emissions are nearly
evenly distributed, with area sources
contributing 51%. Area sources, on the
other hand, emit about 79% of total VOC
emissions. Ohio, Pennsylvania, and Indi-
ana have the greatest SOz emissions.
Texas, California, and Ohio are the great-
est NO, emitters, while Texas and
California have the greatest VOC emis-
sions. The relative contribution of point
versus area sources varies from state to
state.
Seasonal variations were derived from
operating data in the point source inven-
tory and seasonal factors added to the
area source file. Power plant operating
data were updated based on monthly fuel
use data reported on FPC Form 4. Sea-
sonal variations are less than expected.
For S02, the maximum variation is 3% (24
to 27%). Emissions are greatest in winter,
lowest in spring, and differ by 11.9%. The
maximum variation for NO, is only 2% (24
to 26%). Emissions are again greatest in
winter and lowest in spring, with only a
6.3% difference. The maximum variation
for VOC is the same as for NO, (24 to
26%), with an 8.0% difference between
the highest season (summer) and the
lowest (winter).
Although effective plume height is of
greatest interest to modelers, only stack
height data are included in NAPAP. Thus,
only emissions by stack height range
Table 1. NAPAP Emissions by Source
Category* (Preliminary Data)
SO2 NO, VOC
Electric Utilities
Industrial Combustion
Residential/ Commerical
Combustion
Non-ferrous Smelters
Other Industrial
Processes
Transportation
Miscellaneous
Total
"106 tons/year.
17.3
3.7
0.9
1.2
3.0
0.9
0.1
27.1
Table 2. NAPAP Emissions
81
4.5
0.7
Neg
1.0
9.1
0.3
23.7
0.1
1.0
0.1
Neg
45
8.0
9.6
233
by Region''"
(Preliminary Data)
SO, /VO* VOC
EPA Region 1
EPA Region 2
EPA Region 3
EPA Region 4
EPA Region 5
EPA Region 6
EPA Region 7
EPA Region 8
EPA Region 9
EPA Region 10
31 Eastern States"
Nation
0.7
1 2
3.8
65
7.9
23
2.0
08
1.5
0.4
223
27.1
0.6
1.2
2.3
4 1
48
5.3
1.8
1 2
1.7
0.7
151
23.7
12
1.8
2 1
4.0
45
4.0
1 4
0.9
2.4
1.0
15.3
23.3
"Includes Continental U.S. only.
"10s tons/year.
"Includes tier of states from Minnesota south
to Louisiana and all states east.
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Table 3.
State
AL
AZ
AR
CA
CO
CT
DE
DC
FL
GA
ID
IL
IN
IA
KS
KY
LA
ME
MO
MA
Ml
MN
MS
MO
MT
NE
NV
NH
NJ
NM
NY
NC
ND
OH
OK
OR
PA
Rl
SC
SO
TN
TX
UT
VT
VA
WA
WV
Wl
WY
Totals
National Summary of NAPAP Emissions by State' (Preliminary Data}
SO2 /VOx
Point
774
824
59
416
114
51
105
11
1.124
847
36
1.360
1,746
366
198
1,113
343
122
273
317
844
242
256
1.236
146
65
140
102
234
247
787
621
95
2,655
86
31
1.770
10
324
34
1.103
1.081
89
3
338
280
1.091
668
224
25,001
Area
76
20
30
118
20
18
22
6
78
30
20
99
134
24
33
45
158
12
23
45
34
21
50
61
22
12
7
5
69
11
77
32
19
50
16
25
82
4
18
7
31
260
27
7
48
46
13
20
25
2,110
Total
850
844
89
534
134
69
127
17
1.202
877
56
1.459
1.880
390
231
1.158
501
134
296
362
878
263
306
1,297
168
77
147
107
303
258
864
653
114
2,705
102
56
1,852
14
342
41
1,134
1,341
116
10
386
326
1,104
688
249
27,111
Point
273
141
65
455
137
41
36
5
246
279
9
655
536
167
302
373
568
21
114
88
378
229
99
349
28
92
76
30
160
224
321
302
103
665
177
53
595
6
154
22
336
1.543
80
1
160
131
352
205
184
1 1.566
Area
252
153
167
868
155
103
33
22
383
308
82
462
324
'182
290
231
253
43
164
184
368
227
196
258
102
118
47
30
274
83
427
268
65
554
285
175
487
30
148
55
237
1,943
95
43
251
219
121
221
115
12.101
Total
525
294
232
1.323
292
144
69
27
629
587
91
1.117
860
349
592
604
821
64
278
272
746
456
295
607
130
210
123
60
434
307
748
570
168
1.219
462
228
1,082
36
302
77
573
3.486
175
44
411
350
473
426
299
23.667
Point
73
13
14
417
21
44
26
1
23
28
6
208
117
31
81
125
322
20
76
108
238
63
52
177
12
46
4
20
155
52
143
108
2
165
72
40
240
13
228
3
157
940
11
4
105
48
14
76
20
4,962
VOC
Area
351
228
230
1,691
300
259
48
43
725
495
205
768
472
241
241
280
299
73
270
444
730
360
234
429
203
119
73
69
562
109
988
465
46
914
297
279
802
84
259
88
353
1.710
134
36
358
373
124
372
74
18,307
Total
424
241
244
2.108
321
303
74
44
748
523
211
976
589
272
322
405
621
93
346
552
968
423
286
606
215
165
77
89
717
161
1,131
573
48
1.079
369
319
1.042
97
487
91
510
2.650
145
40
463
421
138
448
94
23.269
°/03 tons/year.
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Table 4. NAPAP Emissions by Season"
(Preliminary Data)
SO2 /VO. VOC
Winter
27 26
24
Spring 24 24 25
Summer 25 25 26
Fall . 24 25 25
Total (10* tons/year) 27.1 23.7 23.3
"Percent of total.
Table 5.
Range(ft)
NAPAP Emissions by Stack
Height Range* (Preliminary Data)
SO2 /VO,
VOC
0-120
121-240
241-480
>480
Total (10* tons/year)
20
15
22
43
25.0
34
1-7
20
29
116
94
5
1
0
5.0
"Percent of total.
from stacks >480feet in height are about
twice as much as from any other one
range, demonstrating the dominance of
power plants and smelters with respect to
SC>2 emissions. NO, emissions are a little
more evenly distributed: the lowest height
range, <120 feet, has the greatest emis-
sions, followed closely by the highest
range. Thus, relatively small boilers and
internal combustion engines probably
emit slightly more NO, as a group than do
power plants. Nearly all VOC emissions
come from the lowest stack height range,
indicating the predominance of evapo-
rative point source categories. These data
show that nearly all VOC emissions (both
point and area) are emitted below 120
feet. Of total NO, emissions, 80% or more
also are released below 120 feet. On the
other hand, nearly 40% of all SO2 is
emitted at heights above 480 feet.
The county emission density summary
was derived from data used to generate
the density maps included in Chapter 2 of
the report. The highest range shown on
the maps, >100 tons/square mile, is
Table 6, NAPAP County Emission Density Summary (Preliminary Data)
SO,
NO,
VOC
Density
flange
(tons/mi2)
0-10
10-30
30-100
100-1000
>1000
Counties
in Range
<%)
84
6
6
4
0
Emissions
in Range
(%)
10
11
25
51
3
Counties
in Range
(%>
78
12
7
3
0
Emissions
in Range
(%)
24
19
30
27
0
Counties
in Range
(%/
78
14
6
2
0
Emissions
in Range
(%)
27
20
24
27
2
Table 7. Comparison of NAPAP, Trends, and Work Group 3B Emissions of SO2 and /V0,a
(Preliminary Data)
Electric Utilities
Non-Utility
Combustion
Non-Ferrous
Smelters
Transportation
Other Sources
Total
WG3B
173
3.5
1.3
0.9
3.3
26.3
SOz
Trends
17.1
3.6
1.3
1.0
2 7
25.7
NAPAP
173
46
1 2
0.9
3.1
271
WG3B
6.2
4.6
0.0
9.3
1.1
21.2
/VO,
Trends
7.1
4 1
0.0
105
1.1
228
NAPAP
8 1
52
00
9.1
1.3
23.7
"10s tons/year.
could be summarized for this report. The
stack height ranges were not selected
based on any specific criteria; neverthe-
less, they show how emissions vary with
height. Emissions of S02 in the three
lowest ranges are similar, but emissions
divided into two ranges in the table for
illustrative purposes. For SO2, the coun-
ties in the two highest ranges shown in
the table result from power plants m the
east, primarily in the Ohio Valley and
Great Lakes areas. These counties repre-
sent only 4% of those in the nation, but
have 54% of the total emissions. The two
counties with densities over 1,000 tons/
square mile are Gallia, Ohio, and
Marshall, West Virginia. Both have two
power plants that are in the top 25
emitters in the nation. Counties in the
lowest density range represent 84% of all
counties, but only 10% of the total emis-
sions. For NO,, the counties in the two
highest ranges shown in the table result
from either power plants or highway
vehicles. These counties represent only
3% of those in the nation, but contribute
27% of the total emissions. The only
county with a density over 1,000 tons/
square mile is New York City-Manhattan.
Counties in the lowest density range
represent 78% of all counties, but only
24% of the total emissions. Due to the
greater area source influence, NO, emis-
sions are more evenly distributed among
the ranges than are those for S02- For
VOC, the counties in the two highest
ranges shown in the table result from
solvent use and highway vehicles These
counties represent only 2% of all counties
in the nation, but contribute 29% of the
total emissions. The six counties with
densities over 1,000 tons/square mile—
Manhattan, Kings {New York), Baltimore,
St. Louis, Denver, and San Francisco—
are heavily urbanized, with relatively
small geographic areas. Counties in the
lowest density range represent 78% of all
counties, but only 27% of the total
emissions. Since area sources have a
greater influence on VOC than on NOX,
emissions of VOC are even more evenly
distributed among the density ranges
than are those for NOX.
The comparison of NAPAP, Trends, and
Work Group 3B emissions of SO2 and NO,
shows reasonable agreement. NAPAP
total S02 emissions are greater than
Work Group 3B by 3%, and than Trends by
5.5%. NAPAP and Work Group SB/Trends
emissions compare well for all categories
except non-utility combustion. The dif-
ference in this category is caused by
differences' m fuel use, sulfur content,
and control efficiency. NAPAP total NO,
emissions are greater than Work Group
3B by 11.8%, and than Trends by 4%. The
greatest difference between NAPAP and
Work Group 3B occurs for electric utilities.
Although some of this variation is caused
by fuel differences, most is believed to be
a result of different emission factors and
control efficiencies. The differences be-
tween NAPAP and Trends occur for
electric utilities, non-utility combustion,
and transportation. NAPAP emissions are
higher for the first two categories and
-------
lower for the last. As was the case for the
Work Group 3B comparison, some of the
variation is a result-of fuel differences,
but most is likely to be caused by different
emission factors and control efficiencies.
The non-utility combustion variation oc-
curs for the same reasons as the variation
in utilities, except that non-utilities may
be more affected by fuel differences. The
transportation variation occurs because
more detailed traffic data are used in
developing the Trends estimate. Although
these detailed traffic data are available on
a national basis, very few areas in the
nation maintain data with this detail.
Thus, insufficient detailed data exist for
use in NAPAP.
Data Evaluation
Version 3.0 of NAPAP represents a
detailed inventory of emissions on a
national scale; however, it should be
noted that additional improvements are
planned. Over 80% of the NAPAP emis-
sions truly represent 1980. Over 90% are
in the range from 1978 to 1981. Future
efforts to improve NAPAP will focus on
major point sources that currently do not
have a 1980 year of record. Emissions of
SC>2 and NOX tend to be dominated by
relatively few very large sources. The
1,000 largest emitting plants account for
about 84% of total S02 emissions. The
1,000 largest emitting plants account for
about 42% of total NO, emissions (about
68% of the emissions from all stationary
sources). Many of these large emitting
facilities are electric utility plants and
non-ferrous smelters for which extensive
quality assurance efforts have already
been performed. A review of the data for
other large emitting plants would be
desirable. To a limited extent, this activity
can be completed using NAPAP resources.
In addition, EPA is currently working with
selected state agencies to review the top
50 or so largest emitting plants in each
state. Results of this effort may also
benefit NAPAP.
A principal use of the NAPAP inventory
will be to support atmospheric long range
transport and acid deposition modeling.
In addition to emissions estimates, these
models need location coordinates and
stack parameters for major point sources.
Currently, about 80% of point source SO2
and NOX emissions occur at sources with
complete stack data and valid UTM co-
ordinates. About 2-5% of the sources
account for most of the 20% of emissions
associated with sources that are lacking
some stack parameters or valid coordi-
nates. An effort will be made to collect the
missing data for these sources. Note that
sources with invalid coordinates have at
present a default value corresponding to
the county centroid.
Future Activities
Most Task Group B emission inventory
resources remaining in FY 84 and FY 85
will be used to try to improve NAPAP to
meet the needs of Eulerian modeling
activities. The Eulerian models under
development require additional pollutants
not now in NAPAP, speciation of VOC and
NO, emissions, hourly temporal resolu-
tion of emissions, and spatial resolution
of data into small grid zones covering the
entire U.S. (48 states and the District of
Columbia). At projected resource levels
and the requested time frame (September
1984 for a preliminary data set and
September 1985 for the final inventory),
the Eulerian modeling requirements for
an emissions inventory will have to be
met using existing computer software to
the extent possible, and perhaps, a
number of simplifying assumptions to
achieve adequate temporal, spatial, and
species resolution of the data. The quality
of emissions estimates for additional
pollutants to be included may be limited.
Additional activities are planned for
NAPAP that would support Eulerian
modeling, but would be of interest for
other purposes as well. These include
incorporation of emissions data for
Canada into NAPAP, coordination with
TaskGroup A to include natural emissions
sources into NAPAP, and a statistical
evaluation of the uncertainty of NAPAP
emissions estimates. Successful comple-
tion of these activities depends on the
availability of adequate future funding.
D. A. Toothman, J. C. Yates, andE. J. Sabo are with Engineering-Science. Fairfax.
VA 22030.
Charles O. Mann andJ. David Mobley are the EPA Project Officers (see below).
The complete report, entitled "Status Report on the Development of the NAPAP
Emission Inventory for the 1980 Base Year and Summary of Preliminary Data,"
(Order No. PB 85-167 930/AS; Cost: $11.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
AUSGPO: 1985 — 559-111/10812
-------
United States
Environmental Protection
Agency
Official Business
Penalty for Private Use $300
Center for Environmental Research
Information
Cincinnati OH 45268
OCOC329
CHICAGO
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