United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-90/073 Jan. 1991
EPA Project Summary
National- and State-level
Emissions Estimates of
Radiatively Important Trace
Gases (RITGs) from
Anthropogenic Sources
Stephen Piccot and Mark Saeger
This report documents the develop-
ment of national- and state-level emis-
sions estimates of radiatively important
trace gases (RITGs) that were prepared
in support of the staff committee of the
National Governors' Association's Taslc
Force on Global Climate Change. Emis-
sions estimates are presented for the
principal anthropogenic sources of car-
bon dioxide (CO2), methane (CHJ, chlo-
rof luorocarbons (CFCs), and ozone pre-
cursors. The national annual emission!}
of CO, CH4, CFCs, volatile organic com-
pounds (VOCs), nitrogen oxides (NOx)
and carbon monoxide (CO), in units of
thousands of tons per year, are esti-
mated to be 5,517,223; 33,000; 440;
22,072; 20,541; and 60,938, respectively.
Emissions were estimated for these spe-
cies from readily available databases
and other information. Thus, the emis-
sions estimates presented in this report
are not totals of all possible sources and
should be Interpreted only as estimate!!
of the contributions of some of the major
source categories. No estimates of any
natural sources of these compounds are
presented in this report. The data sources
used to estimate the emissions are dis-
cussed and referenced.
This Project Summary was developed
by ERA'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).
Background
• Increased atmospheric concentrations!
of carbon dioxide (CO2) and other radiatively
important trace gases (RITGs) — methane
(Cf-y, nitrous oxide (N2O), chlorofluorocar-
bons (CFCs), and tropospheric ozone (O3)
— have raised concerns about potential
climate change among the general public
and members of the scientific community.
Since volatile organic compounds (VOCs),
oxides of nitrogen (NOX), and carbon mon-
oxide (CO) are involved in atmospheric
chemistry processes which form tropo-
spheric ozone, they are also of concern.
Much uncertainty exists about how cli-
mate change may affect specific geographic
regions or ecological systems. To reduce
this uncertainty, research is underway to
estimate the potential magnitude and tim-
ing of climate change, the relative contribu-
tion of anthropogenic and natural sources
of the implicated trace gases, the atmo-
spheric/chemical processes in which these
gases participate, and the extent of eco-
logical effects resulting from climate change.
Emissions from human activities such
as fossil fuel combustion, industry, and ag-
riculture are a primary cause of the increas-
ing concentrations of RITGs in the Earth's
atmosphere. In order to evaluate the extent
to which these human activities will influence
future atmospheric composition and climate,
it is necessary to characterize all significant
sources and to identify their locations and
strengths.
Project Description
This report presents state-level esti-
mates of emissions of RITGs — with the
exception of N2O — resulting from anthro-
pogenic activities. The emissions estimates
presented here were developed in a short
time frame to assist the National Gover-
nors' Association and should be consid-
ered preliminary estimates. Considerable
Printed on Recycled Paper
-------
research Is currently underway which could
improve these estimates, particularly for
gases (such as CH4) whose emission esti-
mates have a high degree of uncertainty.
The geographic scope of the emissions
estimates includes the 48 contiguous U.S.
and the District of Columbia. Table 1
cross-references the gases and sources
for which emissions estimates were devel-
oped. These emissions estimates were
developed from readily available databases
and include most of the significant sources
of RITG emissions. Some potentially sig-
nificant sources were not included because,
at the time this report was prepared, repre-
sentative data were not readily available
(e.g., CH4 emissions from surface mining
operations and manure piles were not in-
cluded). Emissions of CO2 from cement
manufacturing were not included because
of its relatively minor role on the national
scale and because of project resource con-
straints.
The state-level emissions estimates
presented here are for sources within the
boundaries of each state. Therefore, the
results of this study do not quantify the
emissions which occur outside a state that
may be attributable to activities within the
state. For example, power plants and fuel
production facilities located outside of Cali-
fornia provide electricity and natural gas to
users within the state. Although the energy
is provided to satisfy demand in California,
the emissions associated with these sources
are not attributed to California. Rather, they
are attributed to the state in which the power
plants and natural gas transmission lines
are located. Clearly, significant greenhouse
gas emissions may be associated with the
interstate transport of energy and other
commodities. However, developing the
energy and commodity balances neces-
sary to take this into account was beyond
the scope of this study.
Historically, major anthropogenic emis-
sions inventory development activities per-
formed by the Environmental Protection
Agency have focused on issues related to
the potential health effects of air pollutants.
Atmospheric concentrations of CO2, CH4
and CFCs have not been associated with
health hazards; therefore, the available
emissions estimates for these species are
not as complete as for other air pollutants.
Tropospheric ozone is recognized as a
health hazard; however, ozone is not emit-
ted directly from anthropogenic activities.
Ozone is formed in the near surface tropo-
sphere by a complex reaction mechanism
that involves reactive hydrocarbons (VOCs),
NO,, and CO in the presence of sunlight.
Table 1. Sources and Gases Included in This Study
Source
Trace Gases
Fuel Combustion8
Industrial
Residential
" Commercial
Transportation
Electric Power Plants
Major Sources of Methane11
Landfills
Underground Coal Mines
Domestic Animals
General Industrial/Othet0
Natural Gas Transmission/Distribution
Sources of Chlorofluorocarbons
Refrigeration
Air conditioning
Blowing Agents
Solvents
Aerosols
CO* CO, A/O> VOC
CFC-11, CFC-12,HCFC-22
CFC-113
Other
Industrial Processes
CO, WO, VOC
a Fuels include coal, oil, natural gas, biomass, gasoline, diesel, process gas.
6 Note that rice cultivation is not included here and is not thought to be a major source in the U.S.
Emissions from manure piles are also not included but these sources may be significant in the
U.S.
0 Includes the methane emissions from significant sources included in the National Acid
Precipitation Assessment Program (NAPAP) inventory: transportation, wood combustion, coke
manufacturing, and others.
Discussion of Results
State total emissions for each RITG are
listed in Table 2. Emissions estimates are
included for CO2, CH4, NOX, VOCs, CO, and
CFCs. Emissions were aggregated at the
state level to assist in interpretive analyses
of the relative contributions of various states
and RITGs to the national totals of these
emissions. The national summary presented
in Table 2 clearly shows the dominance of
CO2 emissions among the principal green-
house gases. The anthropogenic sources
of CO2 are primarily fossil fuel and biomass
combustion. The largest fuel combustion
sector in the U.S. is electric utilities. Indus-
trial combustion, commercial/residential
combustion, and transportation are other
important fuel combustion activities. The
utility sector is estimated to contribute 35%
of the total CO2 emissions. Industrial com-
bustion and transportation fuel use are es-
timated to contribute 26 and 24%, respec-
tively. In general, these sources are rea-
sonably well characterized, particularly the
fossil fuel sources, and the uncertainty as-
sociated with these emissions estimates is
low.
Of the CH4 sources examined in this
study, offgasing from landfills is the most
significant national source of methane.
Methane emissions from landfills are esti-
mated to account for 48% of the total
emissions associated with all the sources
examined here. Emissions associated with
farm animals are the second largest source
(21% of the total) while emissions from
natural gas pipeline transmission/distribu-
tion systems are the third largest (14% of
the total). Underground coal mines contrib-
ute 10% of CH4 emissions to the national
total. This estimate understates emissions
from coal mines because it does not include
CH4 emissions from surface mines. The
emissions from surface mining operations
are potentially significant, but available data
are inadequate for estimating state level
emissions. Current estimates of emissions
from the most significant sources of CH4
(landfill offgasing, coal mines, domestic
animals, natural gas transmission/distribu-
tion, and general industrial) are highly un-
certain.
Although the national total emissions of
CFCs presented in Table 2 are orders of
magnitude less than the emissions totals
for other RITGs included in these analy-
ses, the relative importance of CFCs on
global climate change processes should
-------
Table 2. State Level Emissions Estimates for All Radiatively Important Trace
State Name
Alabama
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Dist. of Col.
Florida
Georgia
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Totals1
CO
1,274
701
653
5,436
1,139
532
177
93
2,605
1,763
1,065
2,406
2,026
674
673
1,020
1,654
335
785
924
2,282
1,315
783
1,303
865
402
275
229
1,156
752
2,412
1,839
188
2,857
989
1,056
2,496
121
882
382
1,339
4,620
745
160
1,404
1,948
578
1,250
374
60,938
VOCs
498
240
223
2,185
301
231
87
30
797
604
186
947
557
214
243
410
626
105
276
416
778
423
270
494
163
126
82
82
595
165
989
669
62
1,008
342
302
904
68
363
87
535
2,329
168
49
572
455
307
420
. 89
22,072
NOX
460
248
238
1,245
293
128
68
20
680
588
88
969
885
267
423
520
763
67
282
274
656
354
237
536
155
165
113
55
356
283
628
501
185
1,017
398
169
956
30
258
73
508
2,512
171
25
390
274
457
348
224
20,541
Gases (103 tons/year)
CHt
1,200
350
370
2,200
670
290
61
54
1,100
650
230
1,400
710
640
660
700
800
100
360
530
1,000
660
370
810
260
540
130
86
710
260
1,500
640
190
1,200
770
380
1,800
85
340
310
630
3,100
280
70
1,200
530
1,100
690
160
33,000
C02
129,163
68,031
71,113
452,615
73,512
41,903
16,401
5,512
161,178
165,060
14,197
345,814
264,793
71,620
77,557
124,089
213,892
21,925
81,857
83,989
189,598
83,502
51,722
120,585
30,155
37,776
24,821
15,318
99,472
65,429
201,125
119,947
56,299
286,392
101,290
36,216
. 270,653
9,275
60,078
14,146
117,431
517,239
47,543
7,871
103,508
79,805
108,234
104,299
73,273
5,517,223
CFC
7
6
4
49
6
7
•f
1
20
11
2
20
12
5
4
7
7
2
8
12
18
8
5
9
1
3
1
2
14
2
29
17
1
20
5
4
21
2
7
1
10
29
3
1
12
7
3
9
1
440
' Differences between national totals and the sum of state totals are the result of roundoff error.
not be minimized. These compounds have
lifetimes that are on the order of tens of
years; therefore, past emissions as well
as current and future emissions will have
impacts. The extremely long lifetimes of
these compounds result in their accumu-
lation in the stratosphere, where they
disrupt the stratospheric ozone equilibrium.
In addition to having greater lifetimes,
CFCs are generally much more radiatively
active on a per molecule basis than the
other greenhouse gases. The principal CFC
compounds are CFC-12, HCFC-22, CFC-11
and CFC-113. These compounds are used
in many different applications including air
conditioning, refrigeration, blowing agents,
solvents, and in aerosols; and national
emissions for 1985 are estimated to be
440,000 tons. The most significant of these
applications include activities related to air
conditioning and refrigeration. Data per-
taining to emissions estimates from these
sources are less readily available and a
great deal of uncertainty is associated with
them.
U. S. GOVERNMENT PRINTING OFFICE: 1991/548-028/20158
-------
Stephen Pkcot and Mark Saegerare with Alliance Technologies Corp., Chapel Hill,
NC 27514.
Julian W. Jones is the EPA Project Officer (see below).
The complete report, entitled "National- and State-level Emissions Estimates of
Radiatively Important Trace Gases (RITGs) from Anthropogenic Sources," (Order
No. PB91-103572/AS; Cost: $17.00, (subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield,VA22161
Telephone: 703-487-4650
The EPA Project Off her can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Tnangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati. OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S8-90/073
------- |