United States
Environmental Protection
Agency
Office of Environmental Engineering
and Technology
Washington DC 20460
Research and Development
EPA-600/S7-82-061 Mar. 1983
&EPA Project Summary
Estimates of Sulfur Oxide
Emissions from the Electric
Utility Industry: Volume 1 and
Volume II
Edward H. Pechan
The report that this summary
describes was prepared as part of the
Electric Utility Analysis Project, a re-
search project supported by the U.S.
Environmental Protection Agency
(EPA). The objective of the report is to
provide detailed information on
atmospheric emissions of sulfur oxides
(SOx) from electric generation plants
from 1976 to 1980. Annual emissions
estimates for all generating plants were
calculated using fuel use, fuel quality
and plant configuration data from
several sources.
The analysis of yearly emissions from
1976 to 1980 shows a gradual reduc-
tion of about 7.7 percent in emissions
from the utility industry. The reductions
are attributed to use of cleaner coals
and increased use of SQ2 scrubbers.
Analysis also shows that a subset of
plants with high emissions accounts for
a substantial share of industry capacity
and coal use. Approximately 10 percent
of the plants produced roughly 85
percent of the SOX emissions and
account for 50 percent of total capacity.
Volume I presents a summary of fuel
use and emissions information as well
as results of analyses of the data.
Volume II presents selected statistics
for the 237 plants which were the
largest emitters of SOx during the
1976-1980 period.
This Project Summary was developed
by EPA's Office of Environmental Engi-
neering and Technology, Washington,
DC, 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
Purpose
The purpose of the full two volume
report is to provide detailed and definitive
information on atmospheric emissions of
sulfur oxides from generating plants
operated by the electric utility industry
from 1976 through 1980. To provide the
needed information, a detailed database
at the individual plant level of detail was
used. Analyses based on this database
are presented at the plant level. These
analyses are also aggregated to state or
national totals. The database and the
analyses are the major products of this
study. In addition to sulfur oxide
emissions, the database contains power
generation statistics and information on
quantity and quality of fuels used.
Appendix A of the full report describes the
contents of this database.
In Volume I, summary information and
analytical results are presented. The
companion volume, Volume II, contains
selected statistics for the 237 plants that
emitted the most sulfur oxides over the
period 1976 through 1980. An example
of the information contained in Volume II
is presented in Appendix B of the full
report.
Background
Sulfur dioxide (SOa) is one of the seven
pollutants for which national ambient air
quality standards have been promulgated.
These standards are designed to limit
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ground level concentrations of SO2. More
recently, a number of studies have linked
emissions of sulfur oxides to elevated
levels of acid deposition, thus increasing
the interest in understanding emission
quantities and distribution patterns of
sulfur oxides. In the United States, the
electric utility industry is responsible for
approximately two-thirds of sulfur oxide
emissions.1
Two research needs have been
identified in this context. The first
concerns emissions of S02 and other
possible precursors of acidic deposition
from the electric utility industry. The
second concerns the need to quantify the
effects on the industry of possible actions
to alter emission quantities and/or
patterns. Thus, the EPA has initiated the
Electric Utility Analysis Project (EUAP).
The EUAP is a cooperative agreement
between EPA and the University of Illinois
at Urbana-Champaign, with E.H. Pechan
and Associates, Inc. (EHPA) as the
principle subcontractor.
This summary announces the first of a
series of reports to be produced as part of
the EUAP. One major project activity is
the development of a comprehensive
Electric Utility Analysis Database. The
information presented here is derived
from the Utility Fuel Quality and Use
Database, a major component of this
system.
Scope of Analysis
The analysis encompassed the
following three interrelated tasks:
1. Develop as accurate an estimate as
possible of emissions from the
electric utility industry for the base
year of 1980.
2. Analyze the emission estimates for
the years 1976 through 1979 to
permit further comparison with the
1980 data.
3. Compare the results from task 1
with other available estimates.
Included among these other
estimates are the "AIRTEST 80"
estimate developed by Teknekron
Research, Inc., and modified by
EHPA, estimates reported to the
'Throughout this report, what we refer to as sulfur
dioxide or SO2 emissions are actually total sulfur
emissions expressed as SO2 While the vast majority
of sulfur emitted to the atmosphere from utility plants
is emitted as S02, small amounts are emitted as
sulfate (S04) or other sulfur compounds. The relative
share of sulfur emitted as sulfate differs by source.
Additional research is under way to better character-
ize these emissions
Department of Energy (DOE), by
the utilities themselves, and
estimates maintained by the EPA
as part of the National Emissions
Data System (NEDS). The AIRTEST
estimate generally has been con-
sidered to be the best available
base case utility emissions
estimate. It has been used as part
of the "unified inventory"
developed by the U.S. and
Canadian working groups that
have been examining transbound-
ary air pollution issues, including
acid rain, since August, 1980
under a Memorandum of Intent
between the two governments.
Results
The analyses of yearly S02 emissions
from 1976 to 1980 show a gradual
reduction of about 7.7 percent in
emissions from the utility industry. As
shown in Table 1, this reduction was due
both to reductions in the sulfur content of
coals used by the industry and to the
increased use of flue gas desulfurization
("scrubber") systems. These reductions
amounted to 1.1 million tons from the
levels that would have occurred had coal
sulfur contents not changed from 1976,
and 1.0 million tons due to operation of
more SO2 scrubber systems. Growth in
quantities of coal use accounted for an
increase of 0.9 million tons, almost as
much as either of the two decreasing
factors. Oil-related emissions showed a
net decrease due to a significant decline
in oil use. The decline (430,000 tons)
overshadowed the increase (185,000
tons) that occurred due to the use, on the
average, of higher sulfur oils. The
increase in natural gas use by the
industry had no noticeable effect on S02
emissions, since natural gas combustion
produces almost no S02.
Another illustration of these trends is
presented in Table 2, which compares
total utility fossil fuel use by fuel type and
S02 emissions from these fuels by totals
and per million Btu heat input. Again, the
dominance of coal as a source of utility
S02 emissions is apparent. Average
sulfur content of coal and oil used by the
industry is presented in Table 3.
Almost all of the reductions indicated in
Table 1 occurred in the states with the
highest SO2 emissions. As Table 4
indicates, essentially all of the net
reduction for the nation occurred in the
15 states with the highest utility
emissions in 1980. The set of major S02
emitting states, however, remained fairly
constant between 1976 and 1980. For
example, 8 of the 10 highest emitting
states in 1980 were also among the
Table 1. Summary of Changes in Utility SOz Emissions from 1976 to 1980 (1.000 Tons)
Coal-Related
Emissions
Oil-Related
Emissions
1976 Emissions
17.065
1.755
Difference Due to Change in Quantity of Fuel Used
Difference Due to Change in Fuel Sulfur Content
Difference Due to Increased S02 Scrubbing
1980 Emissions
929
-1.113
-1.013
15.868
-430
185
0
1.510
Table 2. National Utility SO2 Emissions and Heat Value of Fuels Used
Total S02 Emissions (million tons}
Total Heat Value Used (quads)
Coal
Oil
Gas
1976
18.8
16.3
9.7
3.4
3.1
% Change
1980 1976-1980
17.4
18.8
12.2
2.6
4.0
-7.7
15
26
-24
29
Net SO? Emissions as Pounds/Million Btu
All Fuels
Coal
Oil
Gas
2.3
3.5
1.0
<.01
1.9
2.6
1.2
<.01
-17
-26
20
0
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Table 3. National Average Sulfur Content
of Fuels Used by the Utility
Industry
Coal Coal Oil
Sulfur S02 Content Sulfur
Year (%> (Ib/MMBtu) (%)
1976 2.12 3.91 .96
1977 2.01 3.74 .91
1978 1.86 3.50 .96
1979 1.80 3.36 1.02
1980 1.68 3.15 1.04
highest emitting states in 1976.
Michigan and Alabama, ranked ninth and
tenth in 1976, were replaced by Georgia
and Florida in 1980. The set of states
comprising the 1 5 highest emitting states
did not change from 1976 to 1980. The
share of total emissions contributed by
the 15 highest states declined slightly
over the period, falling from 86 percent in
1976 to 83 percent in 1980.
Table 4 also shows utility emissions for
a 31 -state eastern U.S. region which
includes all of the states east of the
Mississippi River plus the first tier of
states west of the Mississippi (Minnesota,
Iowa, Missouri, Arkansas, and Louisiana).
This region, which has been used in a
variety of acid rain-related studies, ac-
counted for 95 percent of national utility
S02 emissions in 1 976 and 92 percent in
1980.
A subset of plants with high emissions
accounts for a substantial share of
industry capacity and coal use. To
illustrate this, a subset of plants was
developed consisting of the 200 highest
SO2 emitting plants during 1980. As
Table 5 shows, these plants, about 10
percent of plants included in the study,2
accounted for slightly less than 50
percent of all generating capacity, over 75
percent of all coal used, and over 85
percent of all SO2 emissions. The coal
plants constructed in the last three
decades are generally more economically
efficient because of their larger size.
These plants are used to generate power
a larger fraction of the time, and, without
sulfur emission controls, emit a relatively
larger amount of S02 than comparable
oil- and gas-fired plants.
Appendix C of the full report contains
summary S02 estimates for the 200
highest SO2 emitting plants from three
sources: (1) AIRTEST, (2) Form 67 (for
2 All utility generating plants burning at least some
coal, oil, or natural gas between 1976 and 1980.
Table 4. Trendsin Utility SOiEmissions 1976-1 980 for the 15 Highest Emitting States (1980)
and the Nation (Emissions in 1000 Tons per Year)
1980 1976 Emissions
Rank State Rank 1976 1977 1978 1979 1980
1 Ohio 1
2 Indiana 3
3 Pennsylvania 4
4 Missouri 7
5 Illinois 5
6 Kentucky 2
7 West Virginia 8
8 Tennessee 6
9 Georgia 13
10 Florida 11
1 1 Michigan 9
12 Alabama 10
13 Wisconsin 14
14 New York 12
15 North Carolina 15
2,750 2.686 2.463 2,515 2,172
1,443 1.458 1.351 1.537 1,540
1.432 1,381 1.323 1.415 1,466
1,179 1,202 1,014 1,076 1,141
1,429 1,367 1,293 1,168 1.126
1.512 1.357 1.210 1.130 1.008
1,010 1.001 896 956 944
1,228 1,258 1.033 893 934
499 581 616 666 737
673 658 595 659 726
888 905 807 741 565
705 735 531 521 543
470 515 472 496 486
513 549 520 508 480
410 427 396 380 435
Total of 15 Highest 16.141 16,080 14.520 14.661 14.303
Eastern U.S. Total 17,853 17,945 16.472 16.459 16.459 16.068
National Total 18.821 19.071 17.593 17.685 17,379
Table 5. Shares of 1980 Emissions and Other Variables Attributed to Large Plants
200 Highest
All Plants SO2 Emitting % of Total in
(N=1.878) Plants (N=200) 200 Highest
Total SO2 Emissions (thousand tons)
Total Generating Capacity (gigawatts)
Total Generation (terawatt-hours)
Average Capacity Factor
Total Coal Used (million tons)
Total Oil Used (million barrels)
Total Gas Used (billion cubic feet)
1979), and (3) our own work (for 1976
through 1980).
Table 6 further emphasizes the
dominance of coal plants (plants
consuming at least some coal) among the
set of all plants as well as those in the set
of the 200 highest S02 emitting plants.
The 24 percent of plants burning at least
some coal account for over half of all
17.379 14.984 86
477 227 48
1.754 1,027 59
.42 .52
569 438 77
420 162 39
3,682 1,282 35
generating capacity and over two-thirds
of actual generation. Of the 200 highest
emitters, 183 use at least some coal.
In developing the information pre-
sented here, we conducted extensive com-
parisons with other recent estimates
of SO2 emissions. Extensive comparisons
were made with EPA's National
Emissions Data System (NEDS) as well as
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Table 6. Shares of 1980 Emissions and Other Variables Attributed to Coal Plants
Coal Plants
Among
All 200 Highest Percent of
All Plants Coal Plants Emitters 200 Highest
(N=1,878) (N=457) (N=183) Emitters
Total SO2 Emissions (thousand tons)
Total Generating Capacity (gigawatts)
Total Generation (terawatt hours)
Average Capacity Factor
Total Coal Used (million tons)
Total Oil Used (million barrels)
Total Gas Used (billion cubic feet)
17.379
477
1.754
.42
569
420
3.682
16.153
278
1,223
.50
569
70
239
14,355
209
959
.52
438
57
101
89
75
78
77
81
42
with the AIRIEST system recently used in
the EPA-DOE Acid Rain Mitigation Study.
In addition, selected comparisons were
made with utility-reported data contained
in the DOE's Form 67. Finally, we sub-
jected our draft results to detailed review
by the utilities that own the major S02
emitting plants. We compared NEDS data
with our 1978 estimates because the
weighted average year of record on the
NEDS data type was closest to 1978. The
national differences are relatively small,
but the state differences are much larger.
This may be due at least in part to
different years of record for NEDS data by
state, since the NEDS system is depend-
ent upon state data. AIRTEST data were
compared with our 1980 figures. Again,
the relatively small national differences
mask somewhat larger state differences.
A summary of the comparison of our
estimates with NEDS and AIRTEST is
presented in Table 7. State- and plant-
level comparisons are presented later in
the full report.
We conducted sensitivity analyses on
two key elements of our analyses, coal
sulfur ash retention and capacity
Table 7. Summary Comparison of Utility SO2 Emissions from this Report with Other Estimates
1978 NEDS 7380 AIRTEST
National Emissions (thousand tons) 17,593 18,255 17,379 17,465
Difference (thousand tons) 662 86
Percent Difference 4 0.5
Maximum State Difference (thousand tons) 251.2 266.3
Average Absolute State Difference
(thousand tons)
Average Absolute Difference (percent)
utilization of large plants (see Table 8).
These sensitivity analyses, intended to be
illustrative rather than comprehensive,
show that operating practice has a major
effect on emissions, while the range of
conventional assumptions concerning
how much sulfur is retained in ash rather
than emitted from the stack is relatively
unimportant to overall emissions esti-
mates. The significance of capacity utili-
zation of large plants isfurther illustrated
in Table 9. An increase in minimum
capacity utilization of the 200 highest
emitting plants in 1980 from the current
average of .53 to a minimum of .70 could
increase SO2 emissions by approximately
5.7 million tons. On the other hand, a
decrease in capacity utilization (to a
maximum of .40) in the same plants could
reduce SO2 emissions by about 3.6 million
tons. Of course, such changes would also
affect quantities of fuels used as well as
other aspects of utility operations.
47.8
29.1
35.0
24.2
Table 8. Summary of Sensitivity Analyses Related to Coat Sulfur Ash Retention and Changes in
Capacity Factors
Base Case
AP-42 Sulfur Retention
Low Capacity Utilization of 200 Highest Emitting Plants
(.40 maximum)
High Capacity Utilization of 200 Highest Emitting Plants
(. 70 minimum)
1980 SO2
Emissions
(WOO tons)
17.379
17.583
% of Base 1980
SO2 Emissions
100
101
13.761
23,128
79
133
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Table 9. Emissions from the 200 Highest S02 Emitting Plants under 1980 Conditions and if
Capacity Utilization Were Changed (Emissions in WOO Tons)
Emissions Under Potential Emissions % of Potential Emissions % of
1980 Operating Assuming Maximum 1980 Assuming Minimum 1980
State Conditions 4O% Capacity Factor Actual 70% Capacity Factor Actual
Ohio
Indiana
Pennsylvania
Missouri
Illinois
Kentucky
West Virginia
Tennessee
Georgia
Florida
2.100
1.400
1.400
1.000
900
900
900
900
700
600
1,600
1,100
900
800
700
700
600
700
500
500
75
80
65
80
80
80
65
80
70
85
2,900
2,000
1,700
1,500
1,300
1,300
1.100
1,400
900
1.000
140
140
120
150
145
145
120
155
130
165
Total of 10
Highest States
National Total
10,800
15.000
8,100
11.400
75
75
15,100
20,700
140
140
Edward H. Pechan is withE. H. Pechan & Associates, Inc., Springfield, VA22151.
Paul Schwongels is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Estimates of Sulfur Oxide
Emissions from the Electric Utility Industry,"
"Volume I. Summary and A nalysis," (Order No. PB83-130 229; Cost: $14.50,
subject to change)
"Volume II. Databook," (Order No. PB 83-130 237; Cost: $23.50, subject to
change)
The above reports will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Office of Environmental Engineering and Technology
U.S. Environmental Protection Agency
Washington, DC 20460
•&U. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1916
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