NATIONAL STRATEGY
FOR
CONTROL OF SULFUR OXIDES
FROM
ELECTRIC POWER PLANTS
July ](), 1974
U.S. ENVIRONMENTAL PROTECTION AGENCY
Washinnton, D.C. 20460
Conci
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CONTENTS
Synopsis i
Impact of Sulfur Oxides in the Atmosphere 1
Adverse Effects of Sulfur Dioxide 2
Adverse Effects of Sulfates 4
Available Sulfur Oxides Control Measures 6
Low - Sulfur Fuel 7
Desulfurization of Fuel 8
Flue Gas Desulfurization 9
Intermittent Control Systems 11
Increased Stack Height 14
Current Sulfur Oxides Control Strategy 15
Summary of the Strategy 17
Application to New Plants 18
Application to Plants Switching Fuels 19
Application tO'Existing Plants 19
Basic Priority System for Scheduling Controls 23
Secondary Consideration for Scheduling Controls 24
Long Range Activities for Control of Sulfur Oxides ... 25
Anticipated Results of Control Strategy Application. ... 26
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SYNOPSIS
As part of the Clean Air Act's mandate to protect and
enhance the environment, an extensive national effort is under-
way to attain the current ambient air quality standards for
sulfur dioxide. This effort includes a comprehensive program
for control of sulfur oxides from steam electric power plants.
The objective of the program is to attain the primary (health
related) sulfur dioxide standards as rapidly as possible without
disruption of electrical power generation capability and through
use of domestic energy resources. In order to accomplish this
objective, it will be necessary to delay application of control
measures on some power plants in order to give priority consider-
ation to the plants which cause the current standards to be
exceeded. Of the approximately 1000 existing plants seme 100
coal fired plants (representing 67,000 megawatts) require addi-
tional controls to meet the primary ambient air quality standards
for sulfur dioxide.
The strategy incorporates the following major features:
Emissions from new plants will be minimized by incor-
porating the best demonstrated control measures during
construction. (Currently available techniques include
use of low sulfur fuels and stack gas cleaning systems).
In cases where control measures must be applied to
existing plants in order to attain the current primary
standards, these measures will be of the type capable
of minimizing the adverse effects of acid and particu-
late sulfates as well as sulfur dioxide.
When extended periods of time are necessary to apply
appropriate emission control measures, measures such
as intermittent control will be utilized on a temporary
basis where attainment of the sulfur dioxide standards
can be expedited by their use.
Immediate application of control measures to existing
plants which do not cause violations of the current
primary ambient standards will be given lower priority
until attainment of the primary standards in other
areas is assured.
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Federal enforcement orders will be issued under Section
113 of the Clean Air Act where necessary to ensure that
available control measures are applied under optimum
time schedules nationwide. Where temporary shortages
of permanent control alternatives make attainment of
emission limits impossible, these enforcement orders
will extend beyond the attainment dates under the Act,
in such a manner as to ensure early installations in
priority "locations.
The strategy will not require or authorize use of intermittent
controls as a permanent substitute for constant emission controls
because:
In certain situations (e.q., urban areas) these systems
can't be used in a manner that is enforceable and that
will reliably attain health standards.
There is a growing body of health effects data which
links the sulfate particulates associated with sulfur
dioxide emissions to serious health problems. We do
not believe these problems will be averted by the use
of tall stacks or intermittent control systems, even
if such techniques are successful in achieving the
existing air quality standards for sulfur dioxide.
However, temporary use of intermittent controls iri carefully
selected circumstances will facilitate more rapid attainment of the
current primary sulfur dioxide standards without the necessity for
power plant shutdown, will allow the continued use of the nation's
high sulfur coal reserves while control technology, which will make
it environmentally acceptable is being installed, and will also
allow time to increase the availability of low sulfur fuels.
The end result of this strategy will be to attain the current
primary sulfur dioxide standards as rapidly as possible, while en-
suring that the health effects from sulfate particulates are mini-
mized. This approach will also allow electric utilities to continue
to use available high sulfur coal production to meet the nation's
energy demands. However, under certain limited circumstances,
conversion to oil on a temporary basis may be required.
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NATIONAL STRATEGY FOR CONTROL
OF SULFUR OXIDES FROM
ELECTRIC POWER PLANTS
This paper provides a brief explanation of the Environmental
Protection Agency's long range program for control of sulfur oxides
emissions from fossil fuel-fired electric power plants. It explains
the need for control of sulfur oxides, the currently available
measures for that control, and the basic strategy for application
of those measures.
Impact of Sulfur Oxides in the Atmosphere
Sulfur oxides in the atmosphere consist primarily of gaseous
sulfur dioxide, particulate sulfates, and sulfuric acid aerosols.
Fuel combustion contributes approximately 80 percent of the total
emissions of sulfur oxides in this country. Power plants alone
contribute over one half of these emissions, of which the vast
majority are in the form of sulfur dioxide.
The majority of the sulfur dioxide emitted is eventually
converted into sulfates, including both acid and other particulate
sulfates. However, conversion of sulfur dioxide into sulfates
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involves complex photochemical and catalytic processes in the
atmosphere. The conversion process may require from a few hours
to as long as a week. Since these substances are transported
widely in the atmosphere during these periods, the emissions from
an individual power plant often significantly affect concentrations
of sulfates over thousands of square miles for relatively long
time periods.
Adverse Effects of Sulfur Dioxide
Epidemiological studies (studies of large populations exposed
to ambient air) and other research studies indicate that sulfur
dioxide concentrations in the ambient air are associated with both
morbidity (illness rate) and mortality (death rate), due primarily
to damaqe to the upper respiratory tract, damage to lung tissue,
and aggravation of respiratory systems and lung disease. The adverse
effects are most pronounced in the young, the aged, and those with
existing respiratory ailments such as bronchitis and emphysema.
It is difficult to identify conclusively the level of ambient
sulfur dioxide below which adverse health effects will not occur,
and research studies indicate that such a "threshold level" may not,
in fact, exist. However, primary (health related) national ambient
air quality standards for sulfur dioxide have been established under
Section 109 of the Clean Air Act on the basis of criteria developed
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from over a hundred studies conducted over many years, including
clinical research, laboratory studies, and epidemiological studies
of several hundred thousand individuals. These criteria have
been reviewed and approved by the National Air Quality Advisory
Committee composed of recognized authorities from the government,
medical, industrial, and academic communities. The criteria and
the resulting standards have recently been reaffirmed by independent
reviews by the National Academy of Sciences and the U.S. Department
of Health, Education and Welfare. The standards are necessary to
protect the health of the 3 to 5 percent of the population with
existing respiratory ailments, as we11 as the very young and the
aged in the general population.
Secondary national ambient air quality standards have also
been established to protect the public welfare from known adverse
effects caused by sulfur dioxide. These standards are based on
criteria developed from over 150 scientific studies of effects of
atmospheric sulfur oxides on materials, vegetation, and animals.
These criteria have also been subjected to similar comprehensive
review and approval procedures.
In addition to the ambient air quality standards, standards of
performance for new power plants have been established under Section
111 of the Clean Air Act to limit new emissions to the level
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achievable by the best demonstrated techniques for emission reduction
considering cost. These standards require that all new power plants
use either low sulfur fuel or flue gas desulfurization, irrespective
of whether the surrounding ambient air meets the current ambient
standards for sulfur dioxide.
Adverse Effects of Sulfates
There currently are no national ambient air quality standards
established for sulfates. However, recent research studies conducted
by EPA and other agencies provide strong, albeit preliminary, evidence
of adverse health effects associated with sulfate levels which cur-
rently exist in many areas of the country, particularly in the heavily
populated areas.
This evidence is only tentative, but it provides strong indica-
tions that: (1) when daily sulfate levels exceed approximately 6 to
10 ug/m3, asthma attacks increase in frequency; (2) when daily
levels exceed 9 ug/m^, the elderly experience aggravation of heart
and lung disease; (3) when daily levels exceed 25 ug/m^, daily
mortality (death rate) increases; and (4) when sulfate levels
exceed approximately 13 uq/m^ for several years, acute lower res-
piratory disease increases in children.
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These levels are currently exceeded in many areas of the country.
Excessive levels are most frequent in the major urban areas of the
northeast; non-urban areas ofthe northeast exhibit somewhat lower,
but still excessive, levels. Most western areas exhibit relatively
low, and apparently safe, levels although there are indications in
some regions of the west that sulfate levels are sufficiently high
to pose a threat to public health.
Due to the complex and variable nature of the atmospheric
reactbns which convert sulfur dioxide emissions into acid and par-
ticulate sulfates, it is not yet possible to determine precisely
the degree of sulfur dioxide emission reduction which will be re-
quired to reduce existing sulfate concentrations to acceptable levels.
However, preliminary evidence now exists that: {1} current
sulfate levels in many areas of the country are associated with
adverse effects on the public health; and that (2) substantial
reductions in sulfur dioxide emissions over large areas will be
required to reduce sultate concentrations to acceptable levels,
although little or no reductions may be required in others.
Additionally, world wide attention is beginning to focus on
the severe long range welfare impacts of sulfates. Particulate
sulfates and acid aerosols from the atmosphere are known to accelerate
the corrosion of materials, inhibit growth of vegetation, reduce crop
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yields, restrict visibility, reduce sunlight, and through acidification
of soil and water (the "acid rain" phenomenon), contribute to long
term adverse impacts on many activities related to living organisms,
including agriculture, forestry, fishing, etc.
These effects are being extensively researched in Europe due
to the adverse economic impact which has been attributed to increased
acidity of soil and water. Research is being conducted in the U. S.
but more extensive data are available from abroad (especially from
Sweden) than from work in this country, so we do not yet know whether
the negative effects of acid soil and water in the United States have
reached the levels reported elsewhere. Although these long range
impacts are not addressed by our current ambient standards, it would
be imprudent to ignore these effects during formulation of a long
term strategy for control of sulfur oxides.
Available Sulfur Oxides Control Measures
For fossil fuel-fired power plants, there are five basic methods
capable of attaining the current ambient standards for sulfur dioxide:
1) use of naturally low sulfur fuel; (2) removal of sulfur from the
fuel prior to combustion; (3) removal of sulfur oxides from the
flue gas after combustion; (4) intermittent or periodic reductions
in short term emissions based upon meteorologic conditions or forecasts;
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and (5) dispersing the sulfur oxides resulting from combustion
throughout the atmosphere through the use of tall stacks.
Use of naturally low sulfur fuel results in minimal byproducts;
desulfurization of either the fuel or the flue gas results in by-
products which must either be sold, or disposed of as waste at
deliberately selected sites; and dispersion techniques simply
distribute the waste products over wide areas. Since no single
method may be universally applicable to all situations, it is
necessary to consider the salient features of each in order to
properly assess their application in an effective long range
control strategy.
Low Sulfur Fuel
Gas-fired and most oil-fired power plants can be expected to
experience little difficulty in controlling sulfur oxides emissions.
Except for those plants which convert to coal because of the unavail-
ability of gas or oil as part of the mandatory coal conversion program
under the Energy Supply and Environmental Coordination Act of 1974,
gas and oil-fired plants are of relatively minor concern. Conversions
under the 1974 Act, of course, are subject to strict clean air conditions.
Over one half of the nation's coal reserves are of low sulfur
content, and much of this coal is adequate to attain the ambient
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standards.. Insufficient quantities of low sulfur coal are currently
being mined, but the deficiency can be largely overcome through long
term contracts for low sulfur coal which commercially justify opening
new or expanding existing mines.
However, about 15% of the coal-fired utility capacity is unable
to use most low sulfur coals unless the plants' boilers ere completely
rebuilt. Also, since coal with low sulfur content reduces the
efficiency of electrostatic precipitators commonly used to control
particulate emissions; the reduction in sulfur oxides emissions is
often achieved at the cost of increased expenditures to maintain
acceptable efficiency of control of particulate emissions.
Despite these problems, demand for low sulfur coal has signif-
icantly increased in recent years. The price, which is highly
dependent on geographic location with respect to the reserves, has
escalated; and low sulfur coal is currently in short supply.
Desulfurization of Fuel
Desulfurization of coal has not yet reached the level of
effectiveness achieved by desulfurization of oil. Nevertheless,
limited coal desulfurization is a currently demonstrated practice.
Unlike oil desulfurization, which can reduce sulfur content to
extremely low levels, current commercially feasible coal cleaning
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practices can generally reduce the sulfur content by about one-
third; the exact level depending upon the type of coal and other
factors.
The current level of technology is adequate for the large
number of plants which need relatively small reductions in sulfur
content of coal amenable to current forms of desulfurization to
attain the ambient standards. However, for the many plants which
require major reductions, practical desulfurization of coal must
await further development of chemical coal cleaning, coal gasifi-
cation, and coal liquefaction technology. These technologies
are not expected to be sufficiently developed for widespread
commercial use until the 1980's. Even when they are developed,
they will not be appropriate for all uses due to the water and
energy requirements, the type of coal required, and the heating
quality of the resulting product.
Flue Gas Desulfurization
Flue gas desulfurization technology represents the most practical
medium or long term solution to the sulfur oxides problem for a large
number of coal-fired power plants. Flue gas desulfurization removes
the sulfur oxides from the flue gas after combustion of the fuel.
Depending upon the technology used, the by product is either sold
(generally as sulfur or sulfuric acid) or is disposed of as waste.
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Techniques are commercially available for processing the waste into
stable, non-leaching landfill, or for converting it into various
consturction materials such as aggregate. Although waste disposal
represents a problem for some plants, it is more desirable to dis-
pose of the waste products at deliberately selected sites under
adequate environmental controls, rather than to distribute them
randomly over the countryside through atmosphere dispersion which
will cause adverse health and other effects.
Flue gas desulfurization requires approximately $50 to $70
per killowatt in capital costs, or $25 to $35 million for complete
retrofit of a 500 megawatt plant. Many American utilities have
little or no experience with the technology, and it typically
requires approximately 3 years to design, install, and check
out an individual system. However, EPA'srecently conducted "Na-
tional Public Hearings on Power Plant Compliance with Sulfur
Oxide Air Pollution Regulations" substantiate that the technology
has been sufficiently demonstrated on full scale units to warrant
widespread utility industry commitments for use. Although some
scrubbers tested in the United States have encountered reliability
problems, it is important to realize that each of these problems
has a known solution. Further, these systems can be installed so
that the reliability of power generation itself is not threatened
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by any start up problems experienced in getting the "scrubber"
system operating successfully. It is important to realize that
nearly 50 individual units in this country are in various stages
of planning for, installing, or operating flue gas desulfurization
systems.
The energy required to operate a flue gas desulfurization
unit varies fron) approximately 3 to 7 percent of the power produced
by the plant needing control. If flue gas desulfurization were
applied to all of the some 100 power plants which clearly require
additional contrpl by either scrubbers or low sulfur coal, less
than one percent of the nation's electrical generating capactiy
would be consume^. In cases where low sulfur coal is unavailable,
or impractical fpr use, flue gas desulfurization represents an
available method for meeting the nation's energy needs without
adversely impacting on the public health and welfare. Moreover,
its use will permit maximum utilization of the nation's reserves
of high sulfur cc?al.
Intermittent or Supplementary Control Systems
The preceding three measures would attain the current ambient
standards by reducing total emissions of sulfur oxides. Inter-
mittent control is a concept which, at least in theory, permits
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careful tailoring of emissions to avoid violating the current
ambient standards for sulfur dioxide without significantly reducing
total emission of sulfur oxides. These systems are based cn the
fact that, in the vicinity of many plants, the current short term
sulfur dioxide ambient standards are threatened only during
specific types of meteorological conditions. In the absence of
other sources in the vicinity, it is sometimes possible to predict
the onset of meteorological conditions which will cause the stan-
dards to be exceeded and to predict and implement the degree of
emission reduction required to protect the standards. The rest
of the time emissions are virtually uncontrolled because atmospheric
dispersion would prevent the current sulfur dioxide standards from
being exceeded at ground level.
Intermittent control represents a comparatively inexpensive
(approximately $.5 to 1.5 million capital investment per plant)
interim method by which some isolated plants could attain the
current sulfur dioxide ambient standards.
The concept requires that a plant be capable of temporarily
reducing emissions on short notice. This must normally be accom-
plished in power plants by either: 1) shifting the electrical load
to another power plant; or 2) using a temporary supply of low
sulfur fuel. The first alternative is available to only a limited
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number of plants because many power pools in the country have in-
sufficient spare generating capacity to accommodate the necessary
degree of load shifting at the time when emissions must be reduced.
The second alternative is impractical in many cases due to problems
involving rapid switching of fuel type, increased particulate
emissions, and basic system configuration.
A major operating constraint on use of intermittent control
is the inability to operate an enforceable control system in a
multi-source environment. It is not normally possible for an
individual source to reliably maintain ambient air quality with
intermittent control when other sources are affecting the air
quality also, because the source using intermittent control cannot
control the emissions from the other sources. Since there is no
known way to operate a reliable and enforceable intermittent
control system in a multi-source environment, the systems are at
most generally feasible only for relatively "isolated" plants.
Intermittent control, does not significantly reduce total
emissions of sulfur oxides, and therefore even if it permits
attainment of current ambient standards for SO2 at ground level it
may cause or exacerbate areawide sulfate and "acid rain" problems.
Moreover, the concept is not compatible with the Clean Air Act
requirement that constant emission limitations be used whenever
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possible. This view recently has been confirmed by a decision of
the Fifth Circuit U.S. Court of Appeals, NRDC vs. EPA, and by a
Congressional decision to require constant emission controls to be
installed eventually on power plants that switch from oil to coal.
Accordingly, intermittent control is currently considered an
acceptable control measure only in cases where constant emission
reduction measures are unavailable, and only until such measures
become available. Under this philosophy, authorized intermittent
control systems are referred to as "Supplementary Control Systems,"
meaning that they are intended to supplement available constant
emission controls.
Increased Stack Height
The use of increased stack height (the so-called "Tall Stack"
issue) is one frequently misunderstood aspect of the sulfur oxide
control problem. Stack height is a necessary feature of most air
pollution control strategies even with best available controls
applied. Since it is not normally possible to totally eliminate
pollutant emissions, stacks must be constructed so as to reduce
the possibility of the plume impacting in the immediate vicinity
of the plant.
EPA's "Tall Stack Policy" encourages the use of stacks con-
forming to good engineering practice, which is a function of the
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individual facility configuration and local terrain features. In
general, this policy results in stack heights suffciently tall to
minimize ground level effects caused by aerodynamic wakes, eddies,
and downwash, and those caused by high winds during neutral atmos-
pheric stability conditions. In some cases good engineering
practice requires a relatively tall stack to overcome adverse
terrain features.
However, use of excessively tall stacks in an attempt to
avoid reducing emissions merely results in dispersion of sulfur
dioxide, sulfates, and acid aerosols over wide areas. Their use
as a substitute for permanent emission controls, in addition to
a harmful effect on health and welfare, would be inconsistent
with the aforementioned Fifth Circuit decision.
CURRENT SULFUR OXIDES CONTROL STRATEGY
The sulfur oxides control strategy is oriented toward two
basic objectives: 1) to attain the current primary ambient air
quality standards for sulfur dioxide as rapidly as possible and
2) where additional control measures are required on existing
sources, to ensure that as rapidly as possible those measures
reduce overall levels of sulfur oxide emissions. This second
objective is necessary to minimize threats to the public health
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and welfare from dispersion of dangerous levels of particulates
in the atmosphere.
The strategy will be implemented through a combination of
State Implementation Plans and Federal Enforcement Orders. Imple-
mentation is of necessity, a joint effort of the States and EPA in
order to expedite attainment of the national ambient air quality
standards, new source performance standards, and State emission
limitations under a national priority system which considers the
limited availability of resources as well as the finite time re-
quired to apply available resources.
There are currently slightly over one hundred coal fired
power plants which will be directly impacted by the strategy, and
among the more significant problems which must be accommodated
are: 1) the current temporary deficit of low sulfur coal; 2)
the inability to install flue gas desulfurization technology
nationwide in time to meet the statutory attainment date; 3) the
limited experience of many utilities with flue gas desulfurization
technology; 4) the need to give priority to protection of the
public health; and 5) the current U.S. energy policy which vir-
tually precludes widespread substitution of oil or natural gas
for coal as a viable means for protecting the public health.
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Summary of the Strategy
The strategy contains the following major features:
1) The best demonstrated control measures -- either low
sulfur fuel or flue gas desulfurization -- are required for new
plants in order to hold new emissions to the lowest practical
level, pursuant to Section 111 of the Clean Air Act.
2) The requirement to immediately apply control measures
to existing plants is minimized by placing lower priority on com-
pliance with State regulations which are more stringent than
required to attain the current primary ambient standards.
3) The states are enrnnraged to revise the emission regu-
lations where they are more stringent than necessary to attain
primary standards.
4) All available control measures are applied as rapidly as
possible to existing plants which violate the current primary
ambient standards, including temporary measures such as inter-
mittent or supplementary, controls where necessary to minimize
ambient concentrations.
5) Enforcement orders are used to ensure that application
of interim and permanent control measures is time phased in
accordance with technical practicality and nationwide priorities.
6) Application of additional control measures to existing
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plants where there is nc violation of current ambient standards
is generally deferred until attainment of the primary standards
by other plants is assured.
7) Research and development of improved sulfur oxides
control measures is actively encouraged and supported as a long
range policy.
Application to New Plants
Current estimates are that electric utilities will install
approximately 24,000 megawatts of new capacity per year over the
near term. Of this new capacity, approximately 14,500 megawatts
will be coal-fired and will require either low-sulfur coal or flue
gas desulfurization to achieve the best demonstrated level of
control as required by the Clean Air Act-
The requirement for adequate emission controls on new sources
is accomplished by the existing New Source Performance Standards,
and it is a major consideration in the sulfur oxides control
strategy only to the extent that new sources require low sulfur
coal and flue gas desulfurization systems which could otherwise
be made available to existing sources. Recognizing that existing
sources can generally convert to low sulfur coal more easily than
retrofit flue gas desulfurization technology and that new facilities
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can more easily install such technology, use of low sulfur coal
by new plants at the expense of existing plants that need it should
not be encouraged.
Application to Plants Switching Fuels
Some existing gas-fired or oil-fired power plants are expected
to convert to coal but the exact number of plants and timing of
conversions is currently uncertain. Plants are prohibited from
conversion if the conversion would cause the primary ambient stan-
dards to be exceeded. Some plants may convert for only a short,
specified time period; those plants will be granted variances from
the State emission limitations during the conl-burning ppriod if
conforming fuels are not available. Plants undergoing permanent
conversion will be placed on compliance schedules to incorporate
adequate emission reduction measures within a specified time period,
and might be required to employ interim control measures such as
intermittent control where appropriate.
Application to Existing Plants
There are currently nearly 1000 power plants operating in the
country, with a generation capacity of approximately 300,000 mega-
watts. The vast majority of these plants are currently meeting or
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connng into compliance with State emission limitations and will
not threaten the current sulfur dioxide standards.
However, some plants are subject to State emission limitations
which are more stringent than required to attain the current primary
ambient standards. These emission limitations often require low-
sulfur coal which, if diverted, could be used in other areas to
reduce the threat to the primary standards. Since the fall of 1972.
EPA has been imDlementina a "Clean Fuels Policy" of askinq the
States to aive priority for low-sulfur fuel to plants which are
threatening the primary (health-related) ambient standards, and
defer or modify excessively stringent emission limitations* in
other areas. Currently, major coal-burning States are in the process
of changing their regulations for this purpose, in compliance with
requests by the EPA Administrator and the President.
Of the approximately 1000 existing plants, approximately 100
coal-fired plants (representing about 67,000 megawatts) require
additional emission controls to attain the current primary ambient
standa rds.
Approximately 25 of these plants (about 12,000 megawatts)
require only moderate additional control to attain the standards.
*i.e. More stringent than needed to attain the primary ambient
standards, or sot to meet the secondary standards in an unreason-
ably short time in view of the available supplies of low sulfur
fuels and control technology.
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The necessary degree of control can be achieved through coal de-
sulfunzation, limited blending of low-sulfur coal with the coal
currently being used, and possible increases in some stack heights
up to the level of good engineering practice. In general, these
plants do not represent a major problem, and most will be brought
into compliance with little difficulty.
The remaining plants (55,000 megawatts) require substantial
control to attain the primary standards. It is these plants which
represent the major problem because, although many of these plants
could attain the standards with low-sulfur coal, there are currently
insufficient supplies of low-sulfur coal available. Further, there
is not sufficient time remaining prior to the statutory attainment
date (1975-1977) to install flue gas desulfurization systems on all
remaining plants due to a combination of reasons, including design
and installation times, insufficient vendor capacity and experience,
insufficient experience within many utility systems, and the reluc-
tance of many utilities to apply control systems which are available.
Approximately ten of these existing plants are currently com-
mitted to installation of flue gas desulfurization technology*,
although some of these have only partial commitments which will be
finalized as soon as possible.
*lhere are nearly r>0 individual flue gas desulfurization units
currcrilly in or committed to operation. However, most of those not
yet in operation are planned for new, as opposed to existing, plants.
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Of the approximately 65 plants remaining (a capacity of
53,000 megawatts), a very few are currently incapable of installing
flue gas desulfurization systems or using low-sulfur fuel. Regu-
lations are being developed to specify the conditions and criteria
under which these plants could use Supplementary Control Systems
for an indefinite period while adequate emission control measures
are being developed. These regulations would insure reliable and
enforceable methods for attaining and maintaining the ambient
standards, although they would not significantly alleviate the
adverse impact attributed to atmospheric sulfates.
However, the vast majority of the remaining plants could
apply cither low-sulfur coal, or flue gas desulfurization systems,
or both. Federal enforcement orders will be issued to these plants
requiring time-phased application of available low-sulfur fuels and
flue gas desulfurization systems, with selected interim measures
as appropriate to attain the current ambient standards as rapidly
as possible. Each order will generally apply to an individual
plant, but the compliance times specified in each order will be
prepared in accordance with criteria based on minimizing the
nationwide adverse impact of sulfur oxides emissions. These
criteria include a general priority system based on magnitude
of the health impact on the affected population, and are supplemented
by a variety of secondary considerations.
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Basic Priority System for Scheduling Controls
First priority will be given to plants which severely impact
on major urban, heavily populated areas which are currently in
violation of primary standards for sulfur dioxide. Enforcement
orders will generally require flue gas desulfurization where low
sulfur fuel is not practical, and low sulfur fuel where flue gas
desulfurization is not practical. Secondary considerations (as
outlined below) will be used to suggest the appropriate control
measures in other cases.
A lower priority will be given to those plants with a lesser
impact on attainment of air quality standards in urban areas. For
many of these plants, it may be necessary to extend the compliance
dates until the late 1970's because higher priority plants may be
fully utilizing the available resources until that time. For
some of these plants, it will be necessary to reduce the health
impact of the extended compliance times by requiring some form
of supplementary control during the interim period.
The lowest priority will be given to plants in non-urban
environments now meeting air quality standards for sulfur dioxide
where intermittent control could serve as a reasonably reliable
and enforceable means of maintaining these standards. Enforcement
orders for these plants will contain compliance dates for
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application of constant emission controls which might, in some
cases, extend into the early 1980's. extension beyond this time
is considered unnecessary due to the projected availability of
control systems and low sulfur fuel.
Secondary Consideration for Scheduling Controls
Development of the enforcement orders reguires detailed eval-
uation of each plant on a case-by-case basis, and in many cases will
require considerable negotiation to ensure that the compliance
schedules can be met. In addition to the broad priorities outlined
above, there are several secondary considerations which will influence
compliance schedules for many plants.
Very few electric utilities have adequate experience with
flue gas desulfurization technology at this time. Early installa-
tion of flue gas desulfurization on at least one facility in each
appropriate utility system will be encouraged in order to apply the
technology more effectively to subsequent facilities.
Because prior experience with desulfurization technology per-
mits more effective application of the technology, a time phased
approach will be adopted in some cases, so that a desulfurization
system can be installed on one unit of a facility for checkout and
optimization purposes, and installation on any additional units
would be deferred until experience is gained from the -.nfcial unit.
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Installation of flue qas desulfurization equipment and plant
modifications to use low-sulfur coal often require a period of time
when the facility cannot produce power: Similar off-line periods
are routinely scheduled to permit normal maintenance of the boiler
and generation equipment. To the extent possible, off-line periods
required for application of emission controls will be integrated
into the normal plant maintenance schedules.
Individual plant characteristics and locations result in
differing requirements for and problems with disposal; and hence,
some types of flue gas desulfurization are more desirable than
others at an individual plant. The availability of individual
types of systems is variable, and time-phased application will be
used to ensure that the optimum system is applied to each facility.
And finally, intermittent control offers a potential for
temporarily reducing threats to the current sulfur dioxide standards
until constant control measures can be applied. Because intermittent
control does not alleviate the threat from excessive sulfates and
does not significantly reduce total emissions of sulfur oxides,
its use will be discontinued as soon as possible.
Long Range Activities for Control of Sulfur Oxides
The combined use of flue gas desulfurization, low-sulfur fuels,
and good engineering practice stacks, supplemented where necessary
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by interim use of supplementary control systems, will permit attain-
ment of the current primary sulfur dioxide standards in the relatively
near future. However, increasing energy demands will eventually
overwhelm the ability of control measures to protect the public
health and welfare unless more efficient control measures are made
available.
For this reason, EPA strongly supports and encourages research
and development in diverse areas such as coal desulfurization, gasi-
fication, and liquefaction; more efficient flue gas desulfurization
systems with reduced waste disposal requirements; increased availability
of low-sulfur fuels; and more efficient methods for extracting energy
from the nation's available fuel reserves. The nation must depend
on fossil-fuels as a major energy source for the foreseeable future,
but unless major improvements are made in controlling the sulfur
oxides emissions, our reliance on domestic fossil fuels will be
maintained only at the expense of the health and welfare of large
segments of the population.
Anticipated Results of Control Strategy Application
Application of EPA's sulfur oxides control strategy will have
the following results:
All new plants will come on line with best demonstrated emission
control measures. New emissions growth will thereby be held to the
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lowest practical level, thus providing for maximum future economic
and industrial growth consistent with protection of the public health
and welfare.
Appl ication of emission control measures to existing sources
which are not required to meet the primary ambient standards, but
are required solely to meet State or local emission limitations,
will generally be deferred until attainment of the primary standards
in other areas is assured. This will allow primary standards to be
met as rapidly as possible while allowing the continued use of the
nation's plentiful high-sulfur coal reserves.
Control measures which are required on existing plants will
result in continuous reduction of emissions, thereby minimizing the
adverse effects of sulfates as well as sulfur dioxide.
Control measures will be applied to existing sources on a time
phased basis under enforcement orders which consider nationwide
availability of control measures, degree of impact on the public
health, and secondary considerations which influence the efficiency
y
with which the ambient standards can be attained throughout the
nation.
For a variety of reasons, it will be necessary to apply
intermittent controls or tall stacks temporarily on some plants to
minimize public health impacts from sulfur dioxide until adequate
emission control measures can be applied. In a few cases, interim
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controls may be required until the early 1980's. The use of inter-
mittent controls will be minimized and will be discontinued as soon
as possible. Intermittent controls will not be sanctioned for long
term use where constant control measures are available.
For the long term, development of improved emission reduction
measures is being encouraged because the nation's reliance on fossil-
fuels as a primary energy source will cause future emission levels to
overwhelm the ability of current, emission control measures to protect
the public health and welfare.
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