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•rOP-DOHM' BEST AVAILABLE CONTROL TECHNOLOGY
GUIDANCE DOCUNENT
Environmental Protection Agency
Office of Air Quality Planning and Standards
A1r Quality Nanageaent Division
Noncrlterla Pollutants Prograa Branch
New Source Review Section
March 15, 199r
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TABLE OF CONTENTS
I. Purpose .............................. i
II. Introduction ........................... 4
III. BACT Applicability ........................ 6
IV. A Step by Step Summary of the Top-Down Process .......... 7
A. STEP l--Identify All Control Technologies . . . . • ...... 7
B. STEP 2--Eliminate Technically Infeasible Options ....... 9
C. STEP 3--Rank Remaining Control Technologies by Control
Effectiveness ..................... g
D. STEP 4--Evaluate Most Effective Controls and Document
Results ........... jO
E. STEP 5--Select BACT . . . . ...... '.'.'.'.'.'.'.'.'.'.'.'. 11
V. Top-Down Analysis: Detailed Procedures .............. 12
A. Identify Alternatives Emission Control Techniques ...... 12
1. Demonstrated and Transferable Technologies ....... 13
2. Innovated Technologies ................ .14
3. Consideration of Inherently Lower Polluting
Processes ....................... 15
4. Example .................... .".'!!! 16
B. Technical Feasibility Analysis ................ 19
C. Ranking the Technically Feasible Alternatives to
Establish a Control Hierarchy ............... 24
1. Choice of Units of Emissions Performance to Compare
Levels Amongst Control Options ............ 24
2. Control Techniques With a Wide Range of
Emissions Performance Levels ............. 25
3. Establishment of the Control Options Hierarchy ..... 27
D. The BACT Selection Process .................. 28
1. Energy Impacts Analysis ................. 32
2. Cost/Economic Impacts Analysis ............. 33
a. Estimating Control Costs .............. 35
b. Cost Effectiveness ................ 38
c. Determining an Adverse Economic Impact ....... 45
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TABLE OF CONTENTS, Continued
Pace
3. Environmental Impacts Analysis 47
a. Examples (Environmental Impacts) 49
b. Consideration of Emissions of Toxic
and Hazardous Pollutants 51
E. Selecting BACT 55
F. Other considerations 55
VI. Enforceability of BACT 57
VII. Example BACT Analyses for Gas Turbines 58
A. Example I — Simple Cycle Gas Turbines Firing Natural Gas ... 59
1. Project Summary 59
2. BACT Analysis Summary 59
a. Control Technology Options. 59
b. Technical Feasibility Considerations. . 62
c. Control Technology Hierarchy 63
d. Impacts Analysis Summary 66
e. Toxics Assessment 66
f. Rationale for Proposed BACT 69
B. Example 2--Combined Cycle Gas Turbines Firing Natural Gas . . 70
C. Example 3--Combined Cycle Gas Turbine Firing Distillate
Oil 74
D.Other Considerations 75
APPENDIX A. Definition of Selected New Source Review Terms
APPENDIX B. Estimating Control Costs
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LIST OF TABLES
Table
IV- 1 KEY STEPS IN THE "TOP-DOWN" BACT PROCESS ......... 8
V-l SAMPLE BACT CONTROL HIERARCHY ............... 29
V-2 SAMPLE SUMMARY OF TOP-DOWN BACT IMPACT ANALYSIS RESULTS. . 30
V-3 EXAMPLE CONTROL SYSTEM DESIGN PARAMETERS ......... 37
VII-1 EXAMPLE 1 -- COMBUSTION TURBINE DESIGN PARAMETERS ..... 60
VII-2 EXAMPLE 1 -- SUMMARY OF POTENTIAL NO CONTROL TECHNOLOGY
OPTIONS .......................... 61
VI I -3 EXAMPLE 1 -- CONTROL TECHNOLOGY HIERARCHY ......... 64
VI I -4 EXAMPLE 1 -- SUMMARY OF TOP-DOWN BACT IMPACT ANALYSIS
RESULTS FOR NOX ...................... 67
VII-5 EXAMPLE 2 -- COMBUSTION TURBINE DESIGN PARAMETERS ..... 71
VI I -6 EXAMPLE 2 -- SUMMARY OF TOP-DOWN BACT IMPACT ANALYSIS
RESULTS .......................... 72
B-l EXAMPLE OF A CAPITAL COST ESTIMATE FOR AN ELECTROSTATIC
PRECIPITATOR ....................... B"5
B-2 EXAMPLE OF A ANNUAL COST ESTIMATE FOR AN ELECTROSTATIC
PRECIPITATOR APPLIED TO A COAL-FIRED BOILER ........ B-8
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LIST OF FIGURES
Figure Eaflfi
V-l LEAST-COST ENVELOPE 44
VII-1 LEAST-COST ENVELOPE FOR EXAMPLE 1 68
VII-2 LEAST-COST ENVELOPE FOR EXAMPLE 2 73
B-l ELEMENTS OF TOTAL CAPITAL COST B-2
B-2 ELEMENTS OF TOTAL ANNUAL COST B-6
IV
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I. PURPOSE
This document describes the U.S. Environmental Protection Agency (EPA)
guidance for performing analyses leading to determinations of best available
control technology (BACT) under the prevention of significant air quality
deterioration (PSO) program. This document supersedes prior EPA guidance
documents, policies, and interpretations in this subject area which are
inconsistent with its terms.
The BACT requirement is defined as:
"an emissions limitation (including a visible emission standard)
based on the maximum degree of reduction for each pollutant
subject to regulation under the Clean Air Act which would be
emitted from any proposed major stationary source or major
modification which the Administrator, on a case-by-case basis,
taking into account energy, environmental, and economic impacts
and other costs, determines is achievable for such source or
modification through application of production processes or
available methods, systems, and techniques, including fuel
cleaning or treatment or innovative fuel combustion techniques for
control of such pollutant. In no event shall application of best
available control technology result in emissions of any pollutant
which would exceed the emissions allowed by any applicable
standard under 40 CFR Parts 60 and 61. If the Administrator
determines that technological or economic limitations on the
application of measurement methodology to a particular emissions
unit would make the imposition of an emissions standard
infeasible, a design, equipment, work practice, operational
standard, or combination thereof, may be prescribed instead to
satisfy the requirement for the application of best available
control technology. Such standard shall, to the degree possible,
set forth the emissions reduction achievable by implementation of
such design, equipment, work practice or operation, and shall
provide for compliance by means which achieve equivalent results."
The requirement to conduct a BACT analysis and determination 1s set
forth 1n section 165(a)(4) of the Clean Air Act, 1n federal regulations at
40 CFR 52.21(j), In regulations setting forth the requirements for State
implementation plan approval of a State prevention of significant
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deterioration (PSD) program at 40 CFR 51.166(j), and in the SIP's of the
various States at 40 CFR Part 52, Subpart A - Subpart fFF. Neither this
guidance document in particular nor EPA's policies regarding BACT in general
establish binding regulatory requirements; such requirements are contained in
the regulations and implementation plans referred to above. Rather, this
document is intended to guide permitting officials in those areas subject to
the federal PSD regulations 40 CFR 52.21. The EPA strongly recommends that
this guidance also be followed in areas where a PSD program has received SIP
approval under 40 CFR 51.166. In any event, both EPA and the States must
continue to adhere to the binding regulatory requirements governing BACT
determinations. In this regard, EPA notes that it has consistently
interpreted the statutory and regulatory BACT definitions as containing two
core requirements which EPA believes must be met by any BACT determination,
irrespective of whether it is conducted in a "top-down" manner. First, the
BACT analysis must include consideration of the most stringent available
technologies, i.e., those which provide the "maximum degree of emissions
reduction." Second, any decision to require a lesser degree of emissions
reduction must be justified by an objective analysis of "energy,
environmental, and economic impacts" contained in the record of the permit
decision.
A number of terms and acronyms used in this document have specific
meanings within the context of new source review (HSR). Since this document
is intended for use by permit engineers and others generally familiar with
NSR, these terns are used throughout this document, often without definition.
To aid users of the guidance document who are unfamiliar with these terns,
general definitions of these terns can be found in Appendix A. The specific
regulatory definitions for most of the terms can be found in 40 CFR 52.21.
Should there be any Inconsistency between the definitions contained In
Appendix A and the regulatory definitions or other requirements found In Part
40 of the Code of Federal Regulations, Including any policies or
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interpretations Issued pursuant to those regulations following the issuance of
this document, the regulations and policies, or interpretations shall govern.
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II. INTRODUCTION
On December 1, 1987, the EPA Assistant Administrator for Air and
Radiation Issued a memorandum that implemented certain program initiatives
designed to Improve the effectiveness of the new source review (NSR) programs
within the confines of existing regulations and state implementation plans.
Among these was the "top-down" method for determining best available control
technology (BACT). The purpose of this document is to provide a detailed
description of the top-down method in order to assist permitting authorities
and prevention of significant deterioration (PSD) applicants in conducting
BACT analyses.
In brief, the top-down process provides that all available control
technologies be ranked in descending order of control effectiveness. The PSO
applicant first examines the most stringent -- or "top" -- alternative. That
alternative is established as BACT unless the applicant demonstrates, and the
permitting authority in its informed judgment agrees, that technical
considerations, or energy, environmental, or economic impacts justify a
conclusion that the most stringent technology is not "achievable" in that
case. If the most stringent technology is eliminated in this fashion, then
the next most stringent alternative is considered, and so on.
There are two key criteria that must be satisfied in any BACT analysis
under the Clean A1r Act. First, the permit applicant must consider the Host
stringent control technologies available. Second, if the applicant proposes
less stringent controls, 1t must demonstrate, using objective data, that the
most stringent controls are not achievable due to source-specific energy,
environmental, or economic impacts, and the permitting authority must exercise
Us Informed judgment before accepting that determination. The EPA's adoption
of a top-down approach reflects concern that the Implementation of other prior
approaches to determining BACT was deficient in fulfilling these key BACT
requirements. The EPA expects that the top-down approach will be «ore
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effective than other approaches in assuring that BACT analyses comply with the
requirements of the Clean Air Act.
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III. BACT APPLICABILITY
The applicability criteria for imposition of the BACT requirement vary
from State to State. In general, BACT is required of those new sources and
modifications to existing sources which exceed some specified trigger level.
The trigger level is bases on potential emissions.
The BACT requirement applies to each individual new or modified affected
emissions unit and pollutant emitting activity. Also, individual BACT
determinations are performed for each pollutant emitted from the same emission
unit. Consequently, the BACT determination must separately address, for each
regulated pollutant with a significant emissions increase at the source, air
pollution controls for each emissions unit or pollutant emitting activity
subject to review.
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IV. A STEP BY STEP SlWilARY OF THE TOP-DOWN PROCESS
Table IV-1 shows the five basic steps of the top-down procedure,
including some of the key elements associated with each of the individual
steps. A brief description of each step follows.
IV.A. STEP 1--IDEHTIFY ALL COHTROL TECHNOLOGIES.
The first step in a "top-down" analysis is to identify, for the
emissions unit in question (the term "emissions unit" should be read to mean
emissions unit, process or activity), all "available" control options.
Available control options are those air pollution control technologies or
techniques with a practical potential for application to the emissions unit
and the regulated pollutant under evaluation. Air pollution control
technologies and techniques include the application of production process or
available methods, systems, and techniques, including fuel cleaning or
treatment or innovative fuel combustion techniques for control of the affected
pollutant. This includes technologies employed outside of the United States.
In some circumstances inherently lower-polluting processes are appropriate for
consideration as available control alternatives. The control alternatives
should include not only existing controls for the source category in question,
but also (through technology transfer) controls applied to similar source
categories and gas streams, and innovative control technologies. Technologies
required under lowest achievable emission rate (LAER) determinations are
available for BACT purposes and must also be included as control alternatives
and usually represent the top alternative.
In the course of the BACT analysis, one or more of the options may be
eliminated from consideration because they are demonstrated to be technically
infeasible or have unacceptable energy, economic, and environmental Impacts on
a case-by-case (or site-specific) basis. However, at the outset, applicants
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TABLE IV-1. - KEY STEPS IN THE 'TOP-DOWN' BACT PROCESS
STEP 1: IDENTIFY ALL CONTROL TECHNOLOGIES.
LIST 1s comprehensive (LAER included).
STEP 2: ELIMINATE TECHNICALLY IHFEASIBLE OPTIONS.
A demonstration of technical infeasibility should be clearly
documented and should show, based on physical, chemical, and
engineering principles, that technical difficulties would preclude
the successful use of the control option on the emissions unit
under review.
STEP 3: RANK REN AIMING CONTROL TECHNOLOGIES BY CONTROL EFFECTIVENESS.
Should include:
control effectiveness (percent pollutant removed);
expected emission rate (tons per year);
expected emission reduction (tons per year);
energy impacts (BTU, kWh);
environmental impacts (other media and the emissions of toxic and
hazardous air emissions); and
economic impacts (total cost effectiveness, incremental cost
effeciveness).
STEP 4: EVALUATE HOST EFFECTIVE CONTROLS AND DOCUMENT RESULTS.
Case-by-case consideration of energy, environmental, and economic
impacts.
If top option 1s not selected as BACT, evaluate next Most
effective control option.
STEP 5: SELECT BACT
Most effective option not rejected is BACT.
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should initially identify all control options with potential application to
the emissions unit under review.
IV.B. STEP 2--ELIMINATE TECHNICALLY INFEASIBLE OPTIONS.
In the second step, the technical feasibility of the control options
identified in step one is evaluated with respect to the source-specific (or
emissions unit-specific) factors. In general, a demonstration of technical
infeasibility should be clearly documented and should show, based on physical,
chemical, and engineering principles, that technical difficulties would
preclude the successful use of the control option on the emissions unit under
review. Technically infeasible control options are then eliminated from
further consideration in the BACT analysis.
For example, in cases where the level of control in a permit is not
expected to be achieved in practice (e.g., a source has received a per«it but
the project was cancelled, or every operating source at that permitted level
has been physically unable to achieve compliance with the limit), and
supporting documentation showing why such limits are not technically feasible
is provided, the level of control (but not necessarily the technology) may be
eliminated from further consideration. However, a permit requiring the
application of a certain technology or emission limit to be achieved for such
technology usually is sufficient justification to assume the technical
feasibility of that technology or emission limit.
IV.C. STEP 3--RANK REMAINING CONTROL TECHNOLOGIES BY CONTROL EFFECTIVENESS.
In step 3, all reoaining control alternatives not eliminated 1n step 2
are ranked and then listed 1n order of over all control effectiveness for the
pollutant under review, with the most effective control alternative at the
top. A list should be prepared for each pollutant and for each Missions unit
(or grouping of similar units) subject to a BACT analysis. The 11st should
present the array of control technology alternatives and should Include the
following types of information:
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o control efficiencies (percent pollutant removed);
o expected emission rate (tons per year, pounds per hour);
o expected emissions reduction (tons per year);
o economic impacts (cost effectiveness);
o environmental impacts (includes any significant or unusual
other media impacts (e.g., water or solid waste), and, at a
minimum, the impact of each control alternative on emissions of
toxic or hazardous air contaminants);
o energy impacts.
However, an applicant proposing the top control alternative need not
provide cost and other detailed information in regard to other control
options. In such cases the applicant should document that the control option
chosen is, indeed, the top, and review for collateral environmental impacts.
IV.D. STEP 4--EVALUATE MOST EFFECTIVE CONTROLS AND DOCUMENT RESULTS.
After the identification of available and technically feasible control
technology options, the energy, environmental, and economic impacts are
considered to arrive at the final level of control. At this point the
analysis presents the associated impacts of the control option in the listing.
For each option the applicant is responsible for presenting an objective
evaluation of each impact. Both beneficial and adverse impacts should be
discussed and, where possible, quantified. In general, the BACT analysis
should focus on the direct impact of the control alternative.
If the applicant accepts the top alternative in the listing as BACT froa
an economic and energy standpoint, the applicant proceeds to consider whether
Impacts of unregulated air pollutants or impacts in other eedia would justify
selection of an alternative control option. If there are no outstanding
issues regarding collateral environmental impacts, the analysis is ended and
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the results proposed as BACT. In the event that the top candidate is shown to
be inappropriate, due to energy, environmental, or economic impacts, the
rationale for this finding should be fully documented for the public record.
Then the next most stringent alternative in the listing becomes the new
control candidate and is similarly evaluated. This process continues until
the technology under consideration cannot be eliminated by any source-specific
environmental, energy, or economic impacts which demonstrate that alternative
to be inappropriate as BACT.
IV.E. STEP 5-SELECT BACT
The most effective control option not eliminated in step 4 is proposed as
BACT for the pollutant and emission unit under review.
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V. TOP-DOWN ANALYSIS DETAILED PROCEDURE
V.A. IDENTIFY ALTERNATIVE EMISSION CONTROL TECHNIQUES (STEP 1)
The objective in step 1 is to identify all control options with potential
application to the source and pollutant under evaluation. Later, one or more
of these options may be eliminated from consideration because they are
determined to be technically infeasible or to have unacceptable energy,
environmental or economic impacts.
Each new or modified emission unit (or logical grouping of new or
modified emission units) subject to PSD is required to undergo BACT review.
BACT decisions will generally be made on the information presented in the BACT
analysis, including the degree to which effective control alternatives were
identified and evaluated. Potentially applicable control alternatives can be
categorized in three ways.
o Inherently Lower-Emitting Processes/Practices, including
the use of materials and production processes and work
practices that prevent emissions and result in lower
"production-specific" emissions; and
o Add-on Controls, such as scrubbers, fabric filters, thermal
oxidizers and other devices that control and reduce emissions
after they are produced.
o Combinations of Inherently Lower Emitting Processes and Add-on
Controls. For example, the application of combustion and post-
combustion controls to reduce N(L emissions at a gas-fired
turbine.
The top-down BACT analysis should consider potentially applicable control
techniques fro* all three categories. Lower-polluting processes should be
considered based on demonstrations made on the basis of Manufacturing
identical or similar products from identical or similar raw materials or
fuels. Add-on controls, on the other hand, should be considered based on the
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physical and chemical characteristics of the pollutant-bearing emission
stream. Thus, candidate add-on controls may have been applied to a broad
range of emission unit types that are similar, insofar as emissions
characteristics, to the emissions unit undergoing BACT review.
V.A.I. DEMONSTRATED AND TRANSFERABLE TECHNOLOGIES
Applicants are expected to identify all demonstrated and potentially
applicable control alternatives. Information sources to consider include:
o EPA's BACT/LAER Clearinghouse and Control Technology Center;
o Best Available Control Technology Guideline - South Coast Air
Quality Management District;
o control technology vendors;
o Federal/State/Local new source review permits and associated
inspection/performance test reports;
o environmental consultants;
o technical journals, reports and newsletters (e.g., JAPCA and
the Mclvaine reports), air pollution control seminars; and
o EPA's New Source Review (NSR) bulletin board.
The applicant should make a good faith effort to compile appropriate
information from available information sources, including any sources
specified as necessary by the permit agency. The permit agency should review
the background search and resulting list of control alternatives presented by
the applicant to check that it is complete and comprehensive.
In Identifying control technologies, the applicant needs to survey the
range of potentially available options without regard to where and how the
technologies have been applied previously. This Includes technologies In
application outside the United States to the extent that the technologies have
been successfully demonstrated in practice on full scale operations. Usually,
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technologies which have not yet been applied to (or permitted for) full scale
operations are not considered available; an applicant should be able to
purchase or construct a process or control device that has already been
demonstrated 1n practice.
While EPA's Intent Is to ensure broad consideration In determining
alternative control techniques for consideration as BACT, the focus 1s on the
technologies with a demonstrated potential to achieve the highest levels of
control. It is not necessary to consider unreasonably large numbers of
options. For example, control options incapable of meeting an applicable New
Source Performance Standard (NSPS) or State Implementation Plan (SIP) limit
would not meet the definition of BACT under any circumstances and need not be
considered in the BACT analysis and are not to be considered in step 1.
The fact that a NSPS for a source category does not require a certain
level of control or particular control technology does not preclude Its
consideration in the top-down BACT analysis. For example, the fact that S02
scrubbing is not required under the Subpart Db of the NSPS for Industrial-
Commercial -Institutional Steam Generating Units does not preclude the
inclusion of scrubbing from the list of available technologies or the BACT
selection process. In the BACT analysis, an NSPS simply defines the minimal
level of control. The fact that a more stringent technology was not selected
for the NSPS (or that a pollutant is not regulated by an NSPS) does not
exclude that control alternative or technology as a BACT candidate. When
developing a list of possible BACT alternatives, the only reason for comparing
control options to an NSPS 1s to determine whether the control option would
result in an Missions level less stringent than the NSPS. If so, the option
is unacceptable.
V.A.2. INNOVATIVE TECHNOLOGIES
Although not required in step 1, innovative technologies aav also be
evaluated and proposed as BACT. To be considered innovative, a control
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technique must meet the provisions of 40 CFR 52.21(b)(19) or, where
appropriate, the applicable SIP definition. In essence, if a developing
technology has the potential to achieve a more stringent emissions level than
otherwise would constitute BACT or the same level at a lower cost, it may be
proposed as an innovative control technology. Innovative technologies are
distinguished from technology transfer BACT candidates in that an innovative
technology is still under development and has not been demonstrated in a
commercial application on identical or similar emission units. In certain
instances, the distinction between innovative and transferable technology may
not be straightforward. In these cases, it is recommended that the permit
agency consult with EPA prior to proceeding with the issuance of an innovative
control technology waiver.
Applicants should note that EPA has in the past approved only a limited
number of innovative control technology waivers for a specific control
technology; if a waiver has been applied for or granted to a similar source
for the same technology, granting of additional waivers to similar sources is
highly unlikely.
V.A.3. CONSIDERATION OF INHERENTLY LOWER POLLUTING PROCESSES/PRACTICES
Historically, EPA has not considered the BACT requirement as a means to
redefine the design of the source when considering available control
alternatives. For example, applicants proposing to construct a coal-fired
electric generator, have not been required by EPA as part of a BACT analysis
to consider building a natural gas-fired electric turbine although the turbine
nay be inherently less polluting per unit product (in this case electricity).
However, this Is an aspect of the PSD permitting process 1n which states have
the discretion to engage 1n a broader analysis if they so desire. Thus,
although the gas turbine normally would not be included 1n the list of control
alternatives for a coal-fired boiler. However, there may be instances where,
in the permit authority's judgment, the consideration of alternative
production processes Is warranted and appropriate for consideration in the
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BACT analysis. A production process is defined in terms of its physical and
chemical unit operations used to produce the desired product from a specified
set of raw materials. In such cases, the permit agency should require the
applicant to Include the inherently lower-polluting process in the list of
BACT candidates.
In many cases, a given production process or emissions unit can be made
to be inherently less polluting (e.g; the use of water-based versus solvent
based paints 1n a coating operation or a coal-fired boiler designed to have a
low emission factor for NOX). In such cases the ability of design
considerations to make the process inherently less polluting must be
considered as a control alternative for the source. Inherently lower-
polluting processes/practice are usually more environmentally effective
because of lower amounts of solid wastes and waste water than are generated
with add-on controls. These factors are considered in the cost, energy and
environmental impacts analyses in step 4 to determine the appropriateness of
the additional add-on option.
Combinations of inherently lower-polluting processes/practices (or a
process made to be inherently less polluting) and add-on controls are likely
to yield more effective means of emissions control than either approach alone.
Therefore, the option to utilize a inherently lower-polluting process does
not, in and of itself, mean that no additional add-on controls need be
included in the BACT analysis. These combinations should be identified in
step 1 of the top down process for evaluation in subsequent steps.
V.A.4. EXAMPLE
The process of Identifying control technology alternatives (step 1 1n the
top-down BACT process) Is Illustrated 1n the following hypothetical example.
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Description of Source
A PSD applicant proposes to Install automated surface coating process
equipment consisting of a dip-tank priming stage followed by a two-step spray
application and bake-on enamel finish coat. The product is a specialized
electronics component (resistor) with strict resistance property
specifications that restrict the types of coatings that may be employed.
List of Control Options
The source is not covered by an applicable NSPS. A review of the
BACT/LAER Clearinghouse and other appropriate references indicates the
following control options may be applicable:
Option #1: water-based priaer and finish coat;
[The water-based coatings have never been used in applications
similar to this.]
Option »2: low-VOC solvent/high solids coating for priaer and
finish coat;
[The high solids/low VOC solvent coatings have recently been
applied with success with similar products (e.g., other types of
electrical components).]
Option #3: electrostatic spray application to enhance coating
transfer efficiency; and
[Electrostatically enhanced coating application has been applied
elsewhere on a clearly similar operation.]
Option »4: Missions capture with add-on control via Incineration
or carbon adsorber equipment.
[Jhe VOC capture and control option (incineration or carbon
adsorber) has been used in many cases involving the coating of
different products and the emission stream characteristics *re
similar to the proposed resistor coating process and is identified
as an option available through technology transfer.]
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Since the low-solvent coating, electrostatically enhanced application,
and ventilation with add-on control options may reasonably be considered for
use in combination to achieve greater emissions reduction efficiency, a total
of eight control options are eligible for further consideration. The options
include each of the four options listed above and the following four
combinations of techniques:
Option *5; low-solvent coating with electrostatic applications
without ventilation and add-on controls;
Option *6; low-solvent coating without electrostatic applications
with ventilation and add-on controls;
Option *7; electrostatic application with add-on control; and
Option *8: a combination of all three technologies.
A "no control" option also was identified but eliminated because the
applicant's State regulations require at least a 75 percent reduction in VOC
emissions for a source of this size. Because "no control" would not meet the
State regulations it could not be BACT and, therefore, was not listed for
consideration in the BACT analysis.
Sin«arv of Kev Points
The example illustrates several key guidelines for identifying control
options. These include:
o All available control techniques must be considered in the BACT
analysis.
o Technology transfer uust be considered in identifying control
options. The fact that a control option has never been applied
to process eorission units similar or Identical to that proposed
does not mean It can be ignored In the BACT analysis if the
potential for Its application exists.
o Combinations of techniques should be considered to the extent
they result in more effective means of achieving stringent
emissions levels represented by the "top" alternative,
particularly if the "top" alternative is eliminated.
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V.B. TECHNICAL FEASIBILITY ANALYSIS (STEP 2)
In step 2, the technical feasibility of the control options identified
in step 1 is evaluated. This step is straightforward and simple for control
technologies that are demonstrated--if the control technology has been
installed and operated successfully on the type of source under review, it is
demonstrated and it is technically feasible. For control technologies that
are not demonstrated in the sense indicated above, the analysis is somewhat
more involved.
Two key concepts are important in determining whether an undemonstrated
technology is feasible: "availability" and "applicability." A technology is
considered "available" if it can be obtained by the applicant through
commercial channels or is otherwise available within the common sense meaning
of the term. An available technology is "applicable" if it can reasonably be
installed and operated on the source type under consideration. A technology
that is available and applicable is technically feasible.
Availability in this context is further explained using the following
process commonly used for bringing a control technology concept to reality as
a commercial product:
o concept;
o research and patenting;
o bench scale or laboratory testing;
o pilot scale testing;
o licensing and cownercial demonstration; and
o commercial sales.
A control technique is considered available, within the context presented
above, if it has reached the licensing and commercial sales stage of
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development. A source would not be required to experience extended time
delays or resource penalties to allow research to be conducted on a new
technique. Neither is it expected that an applicant would be required to
experience extended trials to learn how to apply a technology on a totally
new and dissimilar source type. Consequently, technologies in the pilot scale
testing stages of development would not be considered available for BACT
review. An exception would be if the technology were proposed and permitted
under the qualifications of an innovative control device consistent with the
provisions of 40 CFR 52.21(v) or, where appropriate, the applicable SIP.
In general, if a control option is commercially available, it falls
within the options to be identified in step 1. Commercial availability by
itself, however, is not necessarily sufficient basis for concluding a
technology to be applicable and therefore technically feasible. Technical
feasibility, as determined in Step 2, also means a control option may
reasonably be deployed on or "applicable" to the source type under
consideration.
Technical judgment on the part of the applicant and the review authority
is to be exercised in determining whether a control alternative is applicable
to the source type under consideration. In general, a commercially available
control option will be presumed applicable if it has been or is soon to be
deployed (e.g., is specified in a permit) on the same or a similar source
type. Absent a showing of this type, technical feasibility would be based on
examination of the physical and chemical characteristics of the pollutant-
bearing gas stream and comparison to the gas stream characteristics of the
source types to which the technology had been applied previously. Deploy»ent
of the control technology on an existing source with similar gas stream
characteristics is generally sufficient basis for concluding technical
feasibility barring a demonstration to the contrary.
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Alternately, for process-type control alternatives, more general criteria
must be considered in determining whether or not it is applicable to the
source 1n question. The decision would have to be based" on an assessment of
the similarities and differences between the proposed source and other sources
to which the process technique had been applied previously. Absent an
explanation of unusual circumstances by the applicant showing why a particular
process cannot be used on the proposed source the review authority may presume
it 1s technically feasible.
In practice, decisions about technical feasibility are the purview of the
review authority. Further, a presumption of technical feasibility nay be made
by the review authority based solely on technology transfer. Decisions of
this type would be made in the case of add-on controls by comparing the
physical and chemical characteristics of the exhaust gas stream from the unit
under review to those of the unit from which the technology is to be
transferred. Unless significant differences between source types exist that
are pertinent to the successful operation of the control device, the control
option is presumed to be technically feasible.
Within the context of the top-down procedure, an applicant becomes
involved with the issue of technical feasibility in asserting that a control
option identified in Step 1 is technically infeasible. In this instance, the
applicant should make a practical, factual demonstration of infeasibility
based on commercial unavailability and/or unusual circumstances which exist
with application of the control to the applicant's emission units. Generally,
such a demonstration would Involve an evaluation of the pollutant-bearing gas
stream characteristics and the capabilities of the technology. Also a showing
of unresolvable technical difficulty with applying the control would
constitute a showing of technical Infeasibility (e.g., size of the unit,
location of the proposed site, and operating problems related to specific
circumstances of the source), where the resolution of technical difficulties
1s a matter of cost, the applicant should consider the technology as
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technically feasible. The economic feasibility of a control alternative is
reviewed in the economic impacts portion of the BACT selection process.
A demonstration of technical infeasibility is based on a technical
assessment considering physical, chemical and engineering principles and/or
empirical data showing that the technology would not work on the emissions
unit under review, or that unresolvable technical difficulties would preclude
the successful deployment of the technique. Physical modifications needed to
resolve technical obstacles do not in and of themselves provide a
justification for eliminating the control technique on the basis of technical
infeasibility. However, the cost of such modifications can be considered in
estimating cost and economic impacts which, in turn, may form the basis for
eliminating a control technology.
Vendor guarantees may provide an indication of commercial availability and
the technical feasibility of a control technique and could contribute to a
determination of technical feasibility or technical infeasibility, depending
on circumstances. However, EPA does not consider a vendor guarantee alone to
be sufficient justification that a control option will work. Conversely, lack
of a vendor guarantee by itself does not present sufficient justification that
a control option or an emissions limit is technically infeasible. Generally,
decisions about technical feasibility will be based on chemical, and
engineering analyses (as discussed above) in conjunction with information
about vendor guarantees.
A possible outcome of the top-down BACT procedures discussed in this
document Is the evaluation of Multiple control technology alternatives which
result in essentially equivalent emissions. It 1s not EPA's Intent to
encourage evaluation of unnecessarily large numbers of control alternatives
for every emissions unit. Consequently, judgment should be used In deciding
what alternatives will be evaluated in detail in the impacts analysis (Step 4)
of the top-down procedure discussed In a later section. For example, If two
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or more control techniques result in control levels that are essentially
identical considering the uncertainties of emissions factors and other
parameters pertinent to estimating performance, the source may wish to point
this out and make a case for evaluation and use only of the less costly of
these options. The scope of the BACT analysis should be narrowed in this way
only if there is a negligible difference in emissions and collateral
environmental impacts between control alternatives. Such cases should be
discussed with the reviewing agency before a control alternative is dismissed
at this point in the BACT analysis due to such considerations.
It is encouraged that judgments of this type be discussed during a
preapplication meeting between the applicant and the review authority. In
this way, the applicant can be better assured that the analysis to be
conducted will meet BACT requirements. The appropriate time to hold such a
meeting during the analysis is following the completion of the control
hierarchy discussed in the next section.
Smaarv of Kev Points
In summary, important points to remember in assessing technical
feasibility of control alternatives include:
o A control technology that is "demonstrated" for a given type or
class of sources is technically feasible unless source-specific
factors exist and are documented to justify technical
infeasibility.
o Technical feasibility of technology transfer control candidates
generally 1s assessed based on an evaluation of pollutant-bearing
gas stream characteristics for the proposed source and other
source types to which the control had been applied previously.
o Innovative controls that have not been demonstrated on any source
type similar to the proposed source need not be considered 1n the
BACT analysis.
o The applicant is responsible for providing a basis for assessing
technical feasibility or infeasibility and the review authority Is
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responsible for the decision on what is and is not technically
feasible.
V.C. RANKING THE TECHNICALLY FEASIBLE ALTERNATIVES TO ESTABLISH A CONTROL
HIERARCHY (STEP 3)
Step 3 involves ranking all the technically feasible control alternatives
which have been previously identified in Step 2. For the regulated pollutant
and emissions unit under review, the control alternatives are ranked-ordered
from the most to the least effective in terms of emission reduction potential.
The primary focus in the ranking at this time is the overall capabilities of
the control technology options. Later, once the control technology is
determined, the focus shifts to the specific limits to be met by the source.
Two key issues that must often be addressed in this process include:
o What common units should be used to compare emissions
performance levels among options?
o How should control techniques that can operate over a wide
range of emission performance levels (e.g., scrubbers, etc.)
be considered in the analysis?
V.C.I. CHOICE OF UNITS OF EMISSIONS PERFORMANCE TO COMPARE LEVELS AMONGST
CONTROL OPTIONS
In general, this issue arises when comparing inherently lower-polluting
processes to one another or to add-on controls. For example, direct
comparison of powdered (and low-VOC) coatings and vapor recovery and control
systems at a «etal furniture finishing operation 1s difficult because of the
different units of neasure for their effectiveness. In such cases, 1t 1s
probably most effective to express emissions performance as an average steady
state emissions level per unit of product or process. Other examples are:
o pounds VOC emission per gallons of solids applied,
o pounds PM emission per ton of cement produced,
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March 15. 1990
o pounds SOo emissions per million Btu heat input, and
o pounds SOg emission per kilowatt of electric power produced,
Calculating annual emissions levels (tons/yr) using these units becomes
straightforward once the projected annual production or processing rates are
known. The result is an estimate of the annual pollutant emissions that the
source or emissions unit will emit. Annual "potential" emission projections
are calculated using the source's maximum design capacity and full year round
operation (8760 hours), unless the final permit is to include federally
enforceable conditions restricting the source's capacity or hours of
operation. However, emissions estimates used for the purpose of calculating
and comparing the cost effectiveness of a control option are based on a
different approach (see section V.D.2.b. COST EFFECTIVENESS).
V.C.2. CONTROL TECHNIQUES WITH A WIDE RANGE OF EMISSIONS PERFORMANCE LEVELS
The objective of the top-down BACT analysis is to not only identify the
best control technology, but also a corresponding performance level (or in
some cases performance range) for that technology considering source-specific
factors. Many control techniques, including both add-on controls and
inherently lower polluting processes can perform at a wide range of levels.
Scrubbers, high and low efficiency electrostatic precipitators (ESPs), low-VOC
coatings are examples of just a few. It is not the EPA's intention to require
analysis of each possible level of efficiency for a control technique, as such
an analysis would result in a large number of options. Rather, the applicant
should use the «>st recent regulatory decisions and performance data for
identifying the emissions performance level(s) to be evaluated In all cases.
The EPA does not expect an applicant to necessarily accept an emission
limit as BACT solely because it was required previously of a similar source
type. While the most effective level of control must be considered In the
BACT analysis, different levels of control for a given control alternative can
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be considered. This may occur, for example, the consideration of a lower
level of control for a given technology may be warranted in cases where past
decisions involved different source types. The evaluation of an alternative
control level can also be considered where the applicant can to the
satisfaction of the permit agency demonstrate that other considerations
demonstrate the need to also evaluate the control alternative at a lower level
of effectiveness.
Manufacturer's data, engineering estimates and the experience of other
sources provide the basis for determining achievable limits. Consequently, in
the evaluation, latitude exists to consider any special circumstances
pertinent to the specific source under review, or regarding the prior
application of the control alternative, in assessing the capability of the
control alternative. However, the basis for choosing the alternate level (or
range) of control in the BACT analysis must be well documented 1n the
application. In the absence of a showing of differences between the proposed
source and previously permitted sources achieving lower emissions limits, the
permit agency should conclude that the lower emissions limit is representative
for that control alternative.
The permit agency should require an applicant to consider a control
technology alternative otherwise eliminated by the applicant, if the operation
of that control technology at a lower level of control (but still higher than
the next control technology alternative) could no longer warrant the
elimination of the alternative. For example, while a scrubber operating at
98% efficiency Bay be eliminated as BACT by the applicant due to source
specific economic considerations, the scrubber operating in the 90% to 95%
efficiency range nay not have an adverse economic impact.
In summary, when reviewing a control technology with a wide range of
emission performance levels, it is presumed that the source can achieve the
same emission reduction level as another source unless the applicant
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demonstrates that there are source-specific factors or other relevant
information that provide a technical, economic, energy or environmental
justification to do otherwise. Also, a control technology that has been
eliminated as having an adverse economic impact at its highest level of
performance, may be acceptable at a lesser level of performance. For example,
this can occur when the cost effectiveness of a control technology at its
highest level of performance greatly exceeds the cost of that control
technology at a somewhat lower level (or range) of performance.
V.C.3. ESTABLISHMENT OF THE CONTROL OPTIONS HIERARCHY
After determining the emissions performance levels (in common units) of
each control technology option identified in Step 2, a hierarchy is
established that places at the "top" the control technology option that
achieves the lowest emissions level. Each other control option is then placed
after the "top" in the hierarchy by its respective emissions performance
level, ranked from lowest emissions to highest emissions (most effective to
least stringent effective emissions control alternative).
From the hierarchy of control alternatives the applicant should develop a
chart (or charts) displaying the control hierarchy and, where applicable,:
o expected emission rate (tons per year, pounds per hour);
o emissions performance level (e.g., percent pollutant removed,
emissions per unit product, Ib/MMbtu, ppm);
o expected emissions reduction (tons per year);
o economic impacts (total costs, cost «ffectiveness, incremental
cost effectiveness);
o environmental Impacts (includes any significant or unusual
other media Impacts (e.g., water or solid waste), and the
relative ability of each control alternative to control
emissions of toxic or hazardous air contaminants);
o energy impacts (indicate any significant energy benefits or
disadvantages).
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This should be done for each pollutant and for each emissions unit (or
grouping of similar units) subject to a BACT analysis. The chart is used in
comparing the control alternatives during step 4 of the BACT selection
process. Some sample charts are displayed in Table V-l and Table V-2.
Completed sample charts accompany the example BACT analyses provided in
section VII.
At this point, it Is recommended that the applicant contact the reviewing
agency to determine whether the agency feels that any other applicable control
alternative should be evaluated or if any issues require special attention in
the BACT selection process.
V.D. THE BACT SELECTION PROCESS (STEP 4)
After identification of available control options is the consideration of
energy, environmental, and economic impacts and the selection of the final
level of control. The applicant is responsible for presenting an objective
evaluation of each impact. Consequently, both beneficial and adverse impacts
should be discussed and, where possible, quantified. In general, the BACT
analysis should focus on the direct impact of the control alternative.
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TABLE V-l. SAMPLE BACT CONTROL HIERARCHY
Pollutant
SO,
2
Technology
First Alternative
Second Alternative
Third Alternative
Fourth Alternative
Fifth Alternative
Baseline Alternative
Range
of
control
W
80-95
80-95
70-85
40-80
50-85
-
Control
level
for BACT
analysis
(*)
95
90
85
75
70
-
Emissions
limit
15 ppm
30 ppm
45 ppm
75 ppm
90 ppm
-
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TABLE V-2. SAMPLE SUXNMI7 Of TOP-DOW MCT DIPKT MUTSIS RBSULTS
DRAFT
Pollutant/
Emissions
Unit
Econoalc Impacts
Control alternative
Emissions
(Wnr,tpy)
Eilssions
reduction(a)
(tpy)
Total Total Incremental
annualized Cost cost
cost(b) effectiveness(c) effectiveness(d)
($/yr) ($/ton) ($/ton)
Environmental Imnacte
Toxics
inpact(e)
(Yes/Ho)
Adverse
environnental
inpacts(f)
(Yes/Ho)
Energy
Impacts
Incremental
increase
over
baseline(g)
(HBtu/yr)
NDx/Uhit A
HOx/Unit B
SB/Unit ft
SQ2/Unit. B
Top Alternative
Other Alternatlve(s)
Baseline Alternative
Top Alternative
Other Altenatlve(s)
Baseline Alternative
Top Alternative
Other Alternative(s)
Baseline Alternative
Top Alternative
Other Alternatives)
Baseline Alternative
(a) Missions reduction over baseline level.
(b) Total amiuallied cost (capital, direct, and Indirect) of purchasing, installing, and operating the proposed control alternative. A capital recovery
factor approach using a real interest rate (i.e., absent inflation) is used to express capital costs in present-day annual costs.
(c) Cost Effectiveness Is total annualiied cost for the control option divided by the Missions reductions resulting from the option.
(d) The incremental cost effectiveness is the difference in annualized cost for the control option and the next nost effective control option divided by the
difference in missions reduction resulting from the respective alternatives.
(e) Toxics Impact mans there is a toxics impact consideration for the control alternative.
(f) Adverse environmental intact Mam there is an adverse environmental impact consideration Nith the control alternative.
(g) Energy impacts an the difference la total project energy requirements tilth the control alternative and the baseline control alternative expressed in
equivalent illlloM of Itw per year.
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Step 4 validates the suitability of the top control option in the listing
for selection as BACT, or provides clear justification why the top candidate
is Inappropriate as BACT. If the applicant accepts the top alternative in the
listing as BACT from an economic and energy standpoint, the applicant proceeds
to consider whether collateral environmental impacts (e.g., emissions of
unregulated air pollutants or impacts in other media) would Justify selection
of an alternative control option. If there are no outstanding issues
regarding collateral environmental impacts, the analysis is ended and the
results proposed as BACT. In the event that the top candidate is shown to be
inappropriate, due to energy, environmental, or economic impacts, the
rationale for this finding needs to be fully documented for the public record.
Then, the next most effective alternative in the listing becomes the new
control candidate and is similarly evaluated. This process continues until
the control technology under consideration cannot be eliminated by any source-
specific environmental, energy, or economic impacts which demonstrate that the
alternative is inappropriate as BACT.
Determining a control alternative to be inappropriate involves a
demonstration that circumstances exist at the source under review which
distinguish it from other sources where the control alternative may have been
required previously, or that argue against the transfer of technology or
application of new technology. Alternately, where a control technique has
been applied to only one or a very limited number of sources, the applicant
can Identify those characteristlc(s) unique to those sources that nay have
made the application of the control appropriate In those case(s) but not for
the source under consideration. In showing unusual circumstances, objective
factors dealing with the control technology and Its application should be the
focus of the consideration. The specifics of the situation will determine to
what extent an appropriate demonstration has been Bade regarding the
elimination of the more effective altematlve(s) as BACT. In the absence of
unusual circumstance, the presumption Is that sources within the same category
are similar in nature, and that cost and other impacts that have been borne by
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one source of a given source category may be borne by another source of the
same source category.
V.D.I. ENERGY IMPACTS ANALYSIS
Applicants should examine the energy requirements of the control
technology and determine whether the use of that technology results in any
significant or unusual energy penalties or benefits. A source nay, for
example, benefit from the combustion of a concentrated gas stream rich in
volatile organic compounds; on the other hand, more often extra fuel or
electricity is required to power a control device or incinerate a dilute gas
stream. If such benefits or penalties exist, they should be quantified.
Because energy penalties or benefits can usually be quantified in terms of
additional cost or income to the source, the energy impacts analysis can, in
most cases, simply be factored into the economic impacts analysis. However,
certain types of control technologies have inherent energy penalties
associated with their use. While these penalties should be quantified, so
long as they are within the normal range for the technology in question, such
penalties should not, in general, be considered adequate justification for
nonuse of that technology.
Energy impacts should consider only direct energy consumption and not
indirect energy impacts. For example, the applicant could estimate the direct
energy impacts of the control alternative in units of energy consumption at
the source ( e.g., Btu, kWh, barrels of oil, tons of coal). The energy
requirements of the control options should be shown in terns of total (and in
certain cases also incremental) energy costs per ton of pollutant removed.
These units can then be converted into dollar costs and, where appropriate,
factored Into the economic analysis.
As noted earlier, indirect energy impacts (such as energy to produce raw
materials for construction of control equipment) generally are not considered.
However, if the permit authority determines, either independently or based on
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a showing by the applicant, that the indirect energy impact is unusual or
significant and that the impact can be well quantified, the indirect impact
may be considered. The energy impact should still focus on the application of
the control alternative and not a concern over general energy impacts
associated with the project under review as compared to alternative projects
for which a permit is not being sought, or as compared to a pollution source
which the project under review would replace (e.g., it would be inappropriate
to argue that a cogeneration project is more efficient in the production of
electricity than the powerplant production capacity it would displace and,
therefore, should not be required to spend equivalent costs for the control of
the same pollutant).
The energy impact analysis may also address concerns over the use of
locally scarce fuels. The designation of a scarce fuel may vary from region
to region, but in general a scarce fuel is one which is in short supply
locally and can be better used for alternative purposes, or one which nay not
be reasonably available to the source either at the present time or in the
near future.
V.D.2. COST/ECONOHIC IMPACTS ANALYSIS
Cost effectiveness, in terms of dollars per ton of pollutant emissions
reduction, is one of the key criteria to be used in assessing the economic
feasibility of a control alternative. Incremental cost effectiveness may also
be considered in conjunction with total cost effectiveness. In the economic
impacts analysis, primary consideration should be given to quantifying the
cost of control and not the economic situation of the individual source.
Consequently, applicants generally should not propose elimination of control
alternatives on the basis of economic parameters that provide an Indication of
the affordablllty of a control alternative relative to the source. BACT 1s
required by law. Its costs are Integral to the overall cost of doing business
and are not to be considered an afterthought. Consequently, for control
alternatives that have been effectively employed in the same source category,
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the economic Impact of such alternatives on the particular source under review
should be not nearly as pertinent to the BACT decision making process as the
total and, where appropriate, Incremental cost effectiveness of the control
alternative. Thus, where a control technology has been successfully applied
to similar sources in a source category, an applicant should concentrate on
documenting significant cost differences, if any, between the application of
the control technology on those other sources and the particular source under
review.
Cost effectiveness values above the levels experienced by other sources
of the same type and pollutant, are taken as an indication that unusual and
persuasive differences exist with respect to the source under review. In
addition, where the cost of a control alternative for the specific source.
reviewed is within the range of normal costs for that control alternative, the
alternative, in certain limited circumstances, may still be eligible for
elimination. To justify elimination of an alternative on these grounds, the
applicant should demonstrate to the satisfaction of the permitting agency that
costs of pollutant removal for the control alternative are disproportionately
high when compared to the cost of control for that particular pollutant and
source in recent BACT determinations. If the circumstances of the differences
are adequately documented and explained in the application and are acceptable
to the reviewing agency they may provide a basis for eliminating the control
alternative.
In all cases, economic impacts need to be considered In conjunction with
energy and environmental Impacts (e.g., toxics and hazardous pollutant
considerations) 1n selecting BACT. It 1s possible that the environmental
Impacts analysis or other considerations (as described elsewhere) would
override the economic elimination criteria as described 1n this section.
However, absent overriding environmental impacts concerns or other
considerations, an acceptable demonstration of a adverse economic Impact can
be adequate basis for eliminating the control alternative.
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V.D.Z.a. ESTIMATING CONTROL COST
Once the control technology alternatives and achievable emissions
performance levels have been identified, capital and annual costs are
developed. This is an Important step because these costs will form the basis
of the cost and economic impacts used to determine and document If a control
alternative should be eliminated on grounds of its economic impacts.
Consistency in the approach to decision-making is a primary objective of
the top-down BACT approach. In order to maintain and improve the consistency
of BACT decisions made on the basis of cost and economic considerations,
procedures for estimating control equipment costs are based on EPA's OAQPS
Control Cost Manual and are set forth in Appendix B of this document.
Applicants should closely follow the procedures in the appendix and any
deviations should be clearly presented and justified in the documentation of
the BACT analysis.
Normally the submittal of very detailed and comprehensive project cost
data is not necessary. However, where initial control cost projections on the
part of the applicant appear excessive or unreasonable (in light of recent
cost data) more detailed and comprehensive cost data may be necessary to
document the applicant's projections. An applicant proposing the top
alternative usually does not need to provide cost data on the other possible
control alternatives.
Control technology total cost estimates developed for BACT analyses
should be on the order of plus or minus 30 percent accuracy. If wore accurate
cost data are available (such as specific bid estimates), these should be
used. However, these types of costs nay not be available at the tine permit
applications are being prepared. Costs should also be site specific. Soee
site specific factors are costs of raw materials (fuel, water, chemicals) and
labor. For example, in some remote areas costs can be unusually high. For
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example, remote locations in Alaska may experience a 40 - 50 percent premium
on installation costs. The applicant should document any unusual costing
assumptions used in the analysis.
Before costs can be estimated, the control system design parameters must
be specified. The most important item here is to ensure that the design
parameters used in costing are consistent with emissions estimates used in
other portions of the PSD application (e.g., dispersion modeling inputs and
permit emission limits). In general, the BACT analysis should present vendor-
supplied design parameters. Potential sources of other data on design
parameters are BIO documents used to support NSPS development, control
technique.guidelines documents, and cost manuals developed by EPA, or control
data in trade publications. Table V-3 presents some example design parameters
which are important in determining system costs.
To begin, the limits of the area or process segment to be costed is
specified. This well defined area or process segment is referred to as the
control system battery limits. The second step is to list and cost each major
piece of equipment within the battery limits. The top-down BACT analysis
should provide this list of costed equipment. The basis for equipment cost
estimates also should be documented, either with data supplied by an equipment
vendor (i.e., budget estimates or bids) or by a referenced source (such as the
OAQPS Control Cost Manual (Fourth Edition), EPA 450/3-90-006, January 1990).
Inadequate documentation of battery limits is one of the most common reasons
for confusion in comparison of costs of the same controls applied to similar
sources. For control options that are defined as inherently lower-polluting
processes (and not add-on controls), the battery limits may be the entire
process or project.
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TABLE V-3. EXAMPLE CONTROL SYSTEM DESIGN PARAMETERS
Control
Deslon parameter
Wet Scrubbers
Carbon Absorbers
Condensers
Incineration
Electrostatic Precipitator
Fabric Filter
Selective Catalytic Reduction
Scrubber liquor (water, chemicals, etc.)
Gas pressure drop
Liquid/gas ratio
Specific chemical species
Gas pressure drop
Ibs carbon/lbs pollutant
Condenser type
Outlet temperature
Residence time
Temperature
Specific collection area (ft2/acfm)
Voltage density
Air to cloth ratio
Pressure drop
Space velocity
Ammonia to NOx molar ratio
Pressure drop
Catalyst life
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Design parameters should correspond to the specified emission level. The
equipment vendors will usually supply the design parameters to the applicant,
who in turn should provide them to the reviewing agency. In order to
determine if the design is reasonable, the design parameters can be compared
with those shown in documents such as the OAQPS Control Cost Manual. Control
Technology for Hazardous Air Pollutants (HAPS) Manual (EPA 625/6-86-014,
September 1986), and background information documents for NSPS and NESHAP
regulations. If the design specified does not appear reasonable, then the
applicant should be requested to supply performance test data for the control
technology in question applied to the same source, or a similar source.
V.D.2.b. COST EFFECTIVENESS
Cost effectiveness, or dollars per ton of pollutant reduction, is one of
the key economic criterion used to determine if a control option presents
adverse economic impacts. By expressing costs in terms of the amount of
emission reduction achieved, comparisons can more readily be performed among
different locations and types of sources.
Cost effectiveness is calculated as the annualized cost of the control
option being considered divided by the baseline emissions minus the control
option emissions rate, as shown by the following formula:
Cost Effectiveness (dollars per ton removed) -
Control option annualized cost
Baseline emissions rate - Control option emissions rate
Costs are calculated in (annualized) dollars per year ($/yr) and
emissions rates are calculated 1n tons per year (tons/yr). The result is a
cost effectiveness nuaber in (annualized) dollars per ton ($/ton) of pollutant
removed.
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The baseline emissions rate represents a realistic scenario of upper
boundary uncontrolled emissions for the source. The NSPS/NESHAP requirements
or the application of controls, including other controls necessary to comply
with State or local air pollution regulations, are not considered in
calculating the baseline emissions. In other words, baseline emissions are
essentially uncontrolled emissions, calculated using realistic upper boundary
operating assumptions.
A realistic upper-bound case scenario does not mean that the source
operates in an absolute worst case manner all the time. For example, in
developing a realistic upper boundary case, baseline emissions calculations
can also consider inherent physical or operational constraints on the source.
Such constraints should accurately reflect the true upper boundary of the .
source's ability to physically operate and the applicant should submit
documentation to verify these constraints. If the applicant does not
adequately verify these constraints, then the reviewing agency should consider
the application incomplete in cases where the constraints would substantively
affect the outcome of the BACT determination. In addition, the reviewing
agency may require the applicant to calculate the cost effectiveness based on
values exceeding the upper boundary assumptions to determine whether or not
the assumptions have a deciding role in the BACT determination. If the
assumptions have a deciding role in the BACT determination, the reviewing
agency should include enforceable conditions in the permit. For example, VOC
emissions from a storage tank might vary significantly with temperature,
volatility of liquid stored, and throughput. In this case, 1t would not be
realistic to calculate annual VOC emissions by extrapolating over the course
of a year VOC emissions based solely on the hottest summer day. Instead, the
range of expected temperatures should be acknowledged 1n determining baseline
emissions. Likewise, 1t would be unreasonable to assume that gasolIne would
be stored 1n a storage tank being build to feed an oil-fired power boiler or
that such a tank will be continually filled and emptied. However, on the other
hand, an upper boundary case for a storage tank being constructed to store and
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transfer liquid fuels at a marine terminal would consider emissions based on
the most volatile liquids at a high annual through put level since it would
not be unrealistic for the tank to operate in such a manner.
In addition, historic upper boundary operating data, typical for the
source or industry, may be used in defining baseline emissions in evaluating
the cost effectiveness of a control option for a specific source. For
example, if for a source or industry, historical upper boundary operations
call for two shifts a day, it is not necessary to assume full time (8760
hours) operation on an annual basis in calculating baseline emissions. For
comparing cost effectiveness, the same realistic upper boundary assumptions
must, however, be used for both the source in question and other sources (or
source categories) that will later be compared during the BACT analysis. For
example, suppose (based on verified historic data regarding the industry in
question) a given source can be expected to utilize numerous colored Inks over
the course of a year. Each color ink has a different VOC content ranging from
a high VOC content to a relatively low VOC content. The source verifies that
its operation will indeed call for the application of numerous color inks. In
this case, it is more realistic for the baseline emission calculation for the
source (and other similar sources) to be based on the expected mix of inks
that would be expected to result in an upper boundary case annual VOC
emissions rather than an assumption that only one color (i.e, the ink with the
highest VOC content) will be applied exclusively during the whole year.
In another example, suppose sources in a particular industry
historically operate at most at 85 percent capacity. For BACT cost
effectiveness purposes (but not for applicability), an applicant aay calculate
cost effectiveness using 85 percent capacity. However, In comparing costs
with similar sources, the applicant must consistently use an 85 percent
capacity factor for the cost effectiveness of controls on those other sources.
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Although permit conditions are normally used to make operating
assumptions enforceable, the use of "standard industry practice" parameters
for cost effectiveness calculations (but nfll applicability determinations) is
acceptable without permit conditions. However, when a source projects
operating parameters (e.g., limited hours of operation or capacity
utilization, type of fuel, raw materials or product mix or type) that are
lower than standard Industry practice or which have a deciding role in the
BACT determination, then these parameters or assumptions must be made
enforceable with permit conditions. If the applicant will not accept
enforceable permit conditions, then the reviewing agency should use the
absolute worst case uncontrolled emissions. This 1s necessary to ensure that
the source operates within the upper boundary of those parameters used 1n
defining baseline emissions. For example, the baseline emissions calculation
for an emergency standby generator may consider the fact that the source does
not intend to operate more than 2 weeks a year. On the other hand, baseline
emissions associated with a base-loaded turbine would not consider limited
hours of operation. This produces a significantly higher level of baseline
emissions than in the case of the emergency/standby unit and results in more
cost effective controls. As a consequence of the dissimilar baseline
emissions, BACT for the two cases could be very different. Therefore, it is
important that the applicant confirm that the operational assumptions used to
define the source's baseline emissions (and BACT) are genuine. As previously
mentioned, this is usually done through enforceable permit conditions which
reflect limits on the source's operation which were used to calculate baseline
emissions. In certain cases, as discussed above, such explicit perwlt
conditions «ay not be necessary. For example, a source for which continuous
operation would be a physical Impossibility (by virtue of Its design) «ay
consider this limitation In estimating baseline emissions, without a direct
permit limit on operations. However, the permit agency has the responsibility
to verify that the source is constructed and operated consistent with the
Information and design specifications contained in the permit application.
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For some sources it may be more difficult to define what emissions level
actually represents uncontrolled emissions in calculating baseline emissions.
For example, uncontrolled emissions could theoretically be defined for a spray
coating operation as the maximum VOC content coating at the highest possible
rate of application that the spray equipment could physically process, even
though use of such a coating or application rate is unrealistic for the
source. Assuming use of a coating with a VOC content and application rate
greater than expected is unrealistic and would overestimate the emissions
reductions achievable by various control options. The cost effectiveness of
the options could also be greatly underestimated. In this case, uncontrolled
emission factors should be represented by the highest realistic VOC content of
the types of coatings and highest realistic application rates that would be
used by the source, rather than by highest VOC based coating materials or rate
of application in general.
Conversely, if uncontrolled emissions are underestimated, emissions
reductions to be achieved by the various control options would also be
underestimated and their cost effectiveness overestimated. For example, this
type of situation occurs in the previous example if the baseline for the above
coating operation was based on a VOC content coating or application rate that
is too low [when the source had the ability and intent to utilize (even
infrequently) a higher VOC content coating or application rate].
In addition to the cost effectiveness of a control option, incremental
cost effectiveness between control options may also be calculated where the
control option 1s not selected. The Incremental cost effectiveness should be
examined 1n combination with the total cost effectiveness in order to justify
elimination of a control option. For the reasons discussed below, the
incremental cost , by Itself, generally is not an appropriate basis on which
to eliminate a control option. The Incremental cost effectiveness calculation
compares the costs and emissions performance level of a control option to
those of the next most stringent option, as shown in the following formula:
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Incremental Cost (dollars per incremental ton removed) -
Control option annualized cost - Annualized cost of next control option
Next control option emission rate - Control option emissions rate
Caution should be exercised in deriving incremental costs of candidate
control options. For example, assume that eight technically available control
options for analysis are listed in the BACT hierarchy. These are represented
as A through H in Figure V-l. In calculating incremental costs, the analysis
should only be conducted for control options that are dominant among all
possible options. In Figure V-l, the dominant set of control options, A, B,
D, F, G, and H, represent the least-cost envelope depicted by the curvilinear
line connecting them. Points C and E are inferior options and should not be
considered in the derivation of incremental cost effectiveness. Points C and
E represent inferior controls because D will buy more emissions reduction for
less money than C; and similarly, F will by more reductions for less money
than E.
Consequently, care should be taken in selecting the dominant set of
controls when calculating incremental costs. First, the control options need
to be rank ordered in ascending order of higher costs. Then, as Figure V-l
illustrates, the most reasonable smooth curve of the control options is
plotted in such a way that incremental cost effectiveness should be ever-
increasing for increasing levels of stringency. The incremental cost
effectiveness 1s then determined by the difference 1n total annual costs
between two contiguous options divided by the difference 1n emissions
reduction. An example 1s Illustrated 1n Figure V-l for the Incremental cost
effectiveness for control option F. The vertical distance, 'delta' Total
Annual Costs, divided by the horizontal distance, 'delta" Emissions Reduction,
would be the measure of the incremental cost effectiveness for option F.
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Figure V-1. LEAST-COST ENVELOPE
t
Dominant controls (A, B, D, F, G, H) lie on envelope
03
o
O
O
U>
s
cc
o
-A
Inferior controls (C,E)
'd*lta' Total Annual Cost*
*(ttta* Emission* Reduction
I t
INCREASING EMISSIONS REDUCTION (Tons/yr)
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March 15. 1990
A comparison of Incremental costs can also be useful in evaluating the
economic viability of a specific control option over a range of efficiencies.
For example, depending on the capital and operational cost of a control
device, total and incremental cost may vary significantly (either increasing
or decreasing) over the operation range of a control device.
In addition, when evaluating the total or incremental cost effectiveness
of a control alternative, reasonable and supportable assumptions regarding
control efficiencies should be made. An unrealistically low assessment of the
emission reduction potential of a certain technology could result in inflated
cost effectiveness figures.
The final decision regarding the reasonableness of calculated cost
effectiveness values will be made by the review authority considering previous
regulatory decisions. Study cost estimates used in BACT are typically
accurate to ± 20 to 30 percent. Therefore, control cost options which are
within ± 20 to 30 percent of each other should generally be considered to be
indistinguishable when comparing options.
V.D.2.C. DETERMINING AN ADVERSE ECONOMIC IMPACT
It is important to keep in mind that BACT is primarily a technology-
based standard. In essence, if the cost of reducing emissions with the top
control alternative, expressed in dollars per ton, is on the same order as the
cost previously borne by other sources of the same type in applying that
control alternative, the alternative should initially be considered
economically achievable, and therefore acceptable as BACT. However, unusual
circumstances «ay greatly affect the cost of controls in a specific
application. If so they should be documented. An example of an unusual
circumstance night be the unavailability In an arid region of the large
amounts of water needed for a scrubbing system. Acquiring water from a
distant location might add unreasonable costs to the alternative, thereby
justifying its elimination on economic grounds. Consequently, where unusual
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factors exist that result in cost/economic impacts beyond the range normally
incurred by other sources in that category, the technology can be eliminated
provided the applicant has adequately identified the circumstances, including
the cost or other analyses, that show what is significantly different about
the proposed source.
Where the cost of a control alternative for the specific source being
reviewed is within the range of normal costs for that control alternative, the
alternative may also be eligible for elimination in limited circumstances.
This may occur, for example, where a control alternative has not been required
as BACT (or its application as BACT has been extremely limited) and there is a
clear demarcation between recent BACT control costs in that source category
and the control costs for sources in that source category which have been
driven by other constraining factors (e.g., need to meet a PSD increment or a
NAAQS). To justify elimination of an alternative on these grounds, the
applicant should demonstrate to the satisfaction of the permitting agency that
costs of pollutant removal (e.g., dollars per total ton removed) for the
control alternative are disproportionately high when compared to the cost of
control for the pollutant in recent BACT determinations. Specifically, the
applicant should document that the cost to the applicant of the control
alternative is significantly beyond the range of recent costs normally
associated with BACT for the type of facility (or BACT control costs in
general) for the pollutant. This type of analysis should demonstrate that a
technically and economically feasible control option is nevertheless, by
virtue of the magnitude of its associated costs and limited application,
unreasonable or otherwise not "achievable" as BACT in the particular case.
Total and Incremental cost effectiveness numbers are factored Into this type
of analysis. However, such economic information should be coupled with a
comprehensive demonstration, based on objective factors, that the technology
is inappropriate in the specific circumstance.
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The economic Impact portion of the BACT analysis should not focus on
inappropriate factors or exclude pertinent factors, as the results may be
misleading. For example, the capital cost of a control option may appear
excessive when presented by itself or as a percentage of the total project
cost. However, this type of information can be misleading. If a large
emissions reduction is projected, low or reasonable cost effectiveness numbers
may validate the option as an appropriate BACT alternative irrespective of the
apparent high capital costs. In another example, undue focus on incremental
cost effectiveness can give an impression that the cost of a control
alternative is unreasonably high, when, in fact, the total cost effectiveness
is well within the normal range of acceptable BACT costs.
V.D.3. ENVIRONMENTAL IMPACTS ANALYSIS
The environmental impacts analysis is not to be confused with the air
quality impact analysis, which is an independent statutory and regulatory
requirement and is conducted separately from the BACT analysis. The purpose
of the air quality analysis is to demonstrate that the source (using the level
of control ultimately determined to be BACT) will not cause or contribute to a
violation of any applicable national ambient air quality standard or PSD
increment. Thus, regardless of the level of control proposed as BACT, a
permit cannot be issued to a source that would cause or contribute to such a
violation. In contrast, the environmental impacts portion of the BACT
analysis concentrates on impacts other than impacts on air quality (i.e.,
ambient concentrations) due to emissions of the regulated pollutant In
question, such as solid or hazardous waste generation, discharges of polluted
water from a control device, visibility impacts, or emissions of unregulated
pollutants.
Thus, the fact that a given control alternative would result 1n only a
slight decrease in ambient concentrations of the pollutant 1n question when
compared to a less stringent control alternative should not be viewed as an
adverse environmental impact justifying rejection of the more stringent
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control alternative. However, if the cost effectiveness of the more stringent
alternative is exceptionally high, it may (as provided in section V.D.2.) be
considered in determining the existence of an adverse economic impact that
would justify rejection of the more stringent alternative.
The applicant should identify any significant or unusual environmental
impacts associated with a control alternative that have the potential to
affect the selection or elimination of a control alternative. Some control
technologies may have potentially significant secondary (1.C;, collateral)
environmental impacts. Scrubber effluent, for example, may affect water
quality and land use. Similarly, emissions of water vapor from technologies
using cooling towers may affect local visibility. Other examples of secondary
environmental impacts could include hazardous waste discharges, such as spent
catalysts or contaminated carbon. Generally, these types of environmental
concerns become important when sensitive site-specific receptors exist or when
the incremental emissions reduction potential of the top control is only
marginally greater than the next most effective option. However, the fact
that a control device creates liquid and solid waste that must be disposed of
does not necessarily argue against selection of that technology as BACT,
particularly if the control device has been applied to similar facilities
elsewhere and the solid or liquid waste problem under review is not
significantly greater than in those other applications. On the other hand,
where the applicant can show that unusual circumstances at the proposed
facility create greater problems than experienced elsewhere, this may provide
a basis for the elimination of that control alternative as BACT.
The procedure for conducting an analysis of environmental impacts should
be made based on a consideration of site-specific circumstances. In general,
however, the analysis of environmental impacts starts with the Identification
and quantification of the solid, liquid, and gaseous discharges from the
control device or devices under review. This analysis of environmental
impacts should be performed for the entire hierarchy of technologies even if
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the applicant proposes to adopt the "top", or most stringent, alternative).
However, the analysis need only address those control alternatives with any
significant or unusual environmental impacts that have the potential to affect
the selection or elimination of a control alternative. Thus, the relative
environmental impacts (both positive and negative) of the various alternatives
can be compared with each other and the "top" alternative.
Initially, a qualitative or semi-quantitative screening is performed to
narrow the analysis to discharges with potential for causing adverse
environmental effects. Next, the mass and composition of any such discharges
should be assessed and quantified to the extent possible, based on readily
available information. Pertinent information about the public or
environmental consequences of releasing these materials should also be
assembled.
V.D.3.a. EXAMPLES (Environmental Impacts)
The following paragraphs discuss some possible factors for considerations
in evaluating the potential for an adverse other media impact.
o Hater Impact
Relative quantities of water used and water pollutants produced and
discharged as a result of use of each alternative emission control system
relative to the "top" alternative would be identified. Where possible, the
analysis would assess the effect on ground water and such local surface water
quality parameters as ph, turbidity, dissolved oxygen, salinity, toxic
chemical levels, temperature, and any other important considerations. The
analysis should consider whether applicable water quality standards will be
met and the availability and effectiveness of various techniques to reduce
potential adverse effects.
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o So7/d Haste Disposal Impact
The quality and quantity of solid waste (e.g., sludges, solids) that must
be stored and disposed of or recycled as a result of the application of each
alternative emission control system would be compared with the quality and
quantity of wastes created with the "top" emission control system. The
composition and various other characteristics of the solid waste (such as
permeability, water retention, rewatering of dried material, compression
strength, Teachability of dissolved ions, bulk density, ability to support
vegetation growth and hazardous characteristics) which are significant with
regard to potential surface water pollution or transport into and
contamination of subsurface waters or aquifers would be appropriate for
consideration.
o Irreversible or Irretrievable Commitment of Resources
The BACT decision may consider the extent to which the alternative
emission control systems may involve a trade-off between short-term
environmental gains at the expense of long-term environmental losses and the
extent to which the alternative systems may result in irreversible or
irretrievable commitment of resources (for example, use of scarce water
resources).
o Other Environmental Impacts
Significant differences in noise levels, radiant heat, or dissipated
static electrical energy may be considered.
One environmental impact that could be examined Is the trade-off
between emissions of the various pollutants resulting fro* the application of
a specific control technology. The use of certain control technologies Bay
lead to Increases in emissions of pollutants other than those the technology
was designed to control. For example, the use of certain volatile organic
compound (VOC) control technologies can Increase nitrogen oxides (NOX)
emissions. In this instance, the reviewing authority may want to give
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March IS. 1990
consideration to any relevant local air quality concern relative to the
secondary pollutant (in this case NOX) in the region of the proposed source.
For example, if the region in the example were nonattainment for NOX, a
premium could be placed on the potential NOX impact. This could lead to
elimination of the most stringent VOC technology (assuming it generated high
quantities of NOX) 1n favor of one having less of an impact on ambient NOX
concentrations. Another example is the potential for higher emissions of
toxic and hazardous pollutants from a municipal waste combustor operating at a
low flame temperature to reduce the formation of NOX. In this case the real
concern to mitigate the emissions of toxic and hazardous emissions (via high
combustion temperatures) may well take precedent over mitigating NOX emissions
through the use of a low flame temperature. However, in most cases (unless an
overriding concern over the formation and impact of the secondary pollutant is
clearly present as in the examples given), it is not expected that this type
impact would affect the outcome of the decision.
Other examples of collateral environmental impacts would include
hazardous waste discharges such as spent catalysts or contaminated carbon.
Generally these types of environmental concerns become important when site-
specific sensitive receptors exist or when the incremental emissions reduction
potential of the top control option is only marginally greater than the next
most effective option.
V.D.3.b. CONSIDERATION OF EMISSIONS OF TOXIC AND HAZARDOUS AIR POLLUTANTS
The generation or reduction of toxic and hazardous emissions, Including
compounds not regulated under the Clean Air Act, are considered as part of the
environmental 1«pacts analysis. Pursuant to the EPA Administrator's decision
1n north County Resource Recovery Associates. PSD Appeal No. 85-2 (Remand
Order, June 3, 1986), a PSD permitting authority should consider the effects
of a given control alternative on emissions of toxics or hazardous pollutants
not regulated under the Clean A1r Act. The ability of a given control
alternative to control releases of unregulated toxic or hazardous emissions
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roust be evaluated and nay, as appropriate, affect the BACT decision.
Conversely, hazardous or toxic emissions resulting from a given control
technology should also be considered and may, as appropriate, also affect the
BACT decision.
Because of the variety of sources and pollutants that nay be considered
in this assessment, it Is not feasible for the EPA to provide highly detailed
national guidance on performing an evaluation of the toxic Impacts as part of
the BACT determination. Also, detailed Information with respect to the type
and magnitude of emissions of unregulated pollutants for many source
categories 1s currently limited. For example, a combustion source e«1ts
hundreds of substances, but knowledge of the magnitude of some of these
emissions or the hazards they produce is sparse. While the EPA Is pursuing a
variety of projects that will help pertaining authorities to determine
pollutants of concern, EPA believes it 1s appropriate for agencies to proceed
on a case-by-case basis using the best information available. Thus, the
determination of whether the pollutants would be emitted in amounts sufficient
to be of concern is one that the permitting authority has considerable
discretion in making. However, reasonable efforts should be made to address
these issues. For example, such efforts might include consultation with the:
o EPA Regional Office;
o Control Technology Center (CTC);
o National Air Toxics Information Clearinghouse;
o A1r Risk Information Support Center in the Office of Air
Quality Planning and Standards (OAQPS); and
o review of the literature, such as: EPA-prepared compilations of
emission factors.
Source-specific Information supplied by the permit applicant Is often the best
source of information, and it Is Important that the applicant be made aware of
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its responsibility to provide for a reasonable accounting of air toxics
emissions.
Similarly, once the pollutants of concern are Identified, the permitting
authority has flexibility In determining the methods by which 1t factors air
toxics considerations Into the BACT determination, subject to the obligation
to make reasonable efforts to consider air toxics. Consultation by the review
authority with EPA's Implementation centers, particularly the CTC, is again
advised.
It is important to note that several acceptable methods, Including risk
assessment, exist to Incorporate air toxics concerns Into the BACT decision.
The depth of the toxics assessment will vary with the circumstances of the
particular source under review, the nature and magnitude of the toxic
pollutants, and the locality. Emissions of toxic or hazardous pollutant of
concern to the permit agency should be identified and, to the extent possible,
quantified. In addition, the effectiveness of the various control
alternatives in the hierarchy at controlling the toxic pollutant should be
estimated and summarized to assist in making judgements about how potential
emissions of toxic or hazardous pollutants may be mitigated through the
selection of one control option over another.
Under a top-down BACT analysis, the control alternative selected as BACT
will most likely reduce toxic emissions as well as the regulated pollutant.
An example 1s the emissions of heavy metals typically associated with coal
combustion. The metals generally are a portion of, or adsorbed on, the fine
partlculate In the exhaust gas stream. Collection of the ptrtlculate 1n a
high efficiency fabric filter rather than a low efficiency electrostatic
predpltator reduces criteria pollutant partlculate matter emissions and
toxic heavy metals emissions. Because 1n most Instances the Interests of
reducing toxics coincide with the interests of reducing the pollutants subject
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to BACT, consideration of toxics In the BACT analysis generally amounts to
quantifying toxic emission levels for the various control options.
In limited other instances, though, control of regulated pollutant
emissions may compete with control of toxic compounds, as in the case of
certain selective catalytic reduction (SCR) NOX control technologies. The SCR
technology itself results In emissions of ammonia, which increase, generally
speaking, with increasing levels of NOX control. It 1s the Intent of the
toxics screening in the BACT procedure to Identify and quantify this type of
toxic effect. Generally, toxic effects of this type will not necessarily be
overriding concerns and will likely not to affect BACT decisions. Rather, the
Intent is to require a screening of toxics emissions effects to ensure that a
possible overriding toxics issue does not escape notice.
On occasion, consideration of toxics emissions may support the selection
of a control technology that yields less than the maximum degree of reduction
in emissions of the regulated pollutant in question. An example is the
municipal solid waste combustor and resource recovery facility that was the
subject of the North County remand. Briefly, BACT for S02 and PM was selected
to be a lime slurry spray drier followed by a fabric filter. The combination
yields good S02 control (approximately 83 percent), good PM control
(approximately 99.5 percent) and also removes acid gases (approximately 95
percent), metals, dioxins, and other unregulated pollutants. In this
instance, the permitting authority determined that good balanced control of
regulated and unregulated pollutants took priority over achieving the maximum
degree of emissions reduction for one or more regulated pollutants.
Specifically, higher levels (up to 95 percent) of S02 control could have been
obtained by a wet scrubber.
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V.E. SELECTING BACT (STEP 5)
The most effective control alternative not eliminated 1n Step 4 Is
selected as BACT.
It 1s Important to note that, regardless of the control level proposed by
the applicant as BACT, the ultimate BACT decision 1s made by the permit
Issuing agency after public review. The applicant's role 1s primarily to
provide Information on the various control options and, when It proposes a
less stringent control option, provide a detailed rationale and supporting
documentation for eliminating the more stringent options. It 1s the
responsibility of the permit agency to review the documentation and rationale
presented and; (1) ensure that the applicant has addressed all of the nost
effective control options that could be applied and; (2) determine that the
applicant has adequately demonstrated that energy, environmental, or economic
impacts justify any proposal to eliminate the more effective control options.
Where the permit agency does not accept the basis for the proposed elimination
of a control option, the agency may inform the applicant of the need for more
information regarding the control option. However, the BACT selection
essentially should default to the highest level of control for which the
applicant could not adequately justify its elimination based on energy,
environmental and economic impacts. If the applicant is unable to provide to
the permit agency's satisfaction an adequate demonstration for one or more
control alternatives, the permit agency should proceed to establish BACT and
prepare a draft permit based on the most effective control option for which an
adequate justification for rejection was not provided.
V.F. OTHER CONSIDERATIONS
Once energy, environmental, and economic Impacts have been considered,
BACT can only be made more stringent by other considerations outside the
normal scope of the BACT analysis as discussed under the above steps.
Examples Include cases where BACT does not produce a degree of control
stringent enough to prevent exceedences of a national ambient air quality
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standard or PSD Increment, or where the State or local agency will not accept
the level of control selected as BACT and requires more stringent controls to
preserve a greater amount of the available Increment. A permit cannot be
Issued to a source that would cause or contribute to such a violation,
regardless of the outcome of the BACT analysis. Also, States which have set
ambient air quality standards at levels tighter than the federal standards nay
demand a more stringent level of control at a source to demonstrate compliance
with the State standards. Another consideration which could override the
selected BACT are legal constraints outside of the Clean Air Act requiring the
application of a more stringent technology (e.g., a consent decree requiring a
greater degree of control). In all cases, regardless of the rationale for the
permit requiring a more stringent emissions limit than would have otherwise
been chosen as a result of the BACT selection process, the emission Unit in
the final permit (and corresponding control alternative) represents BACT for
the permitted source on a case-by-case basis.
The BACT emission limit in a new source permit is not set until the final
permit is issued. The final permit is not issued until a draft permit has
gone through public comment and the permitting agency has had an opportunity
to consider any new information that may have come to light during the comment
period. Consequently, in setting a proposed or final BACT limit, the permit
agency can consider new information it learns, including recent permit
decisions, subsequent to the submittal of a complete application. This
emphasizes the Importance of ensuring that prior to the selection of a
proposed BACT, all potential sources of Information have been reviewed to
ensure that the list of potentially applicable control alternatives 1s
complete («ost Importantly as it relates to any Bore effective control options
than the one chosen) and that all considerations relating to economic, energy
and environmental Impacts have been addressed. These responsibilities reside
with the applicant.
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VI. ENFORCEABILITY OF BACT
To complete the BACT process, the reviewing agency oust establish an
enforceable emission limit for each emission unit at the source and for each
pollutant subject to review that is emitted from the source. If technological
or economic limitations in the application of a measurement methodology to a
particular emission unit would make an emissions limit infeasible, a design,
equipment, work practice, operation standard, or combination thereof, nay be
prescribed. Also, the technology upon which the BACT emissions limit is based
should be specified in the permit. These requirements should be written in
the permit so that they are specific to the individual emission unit(s)
subject to PSD review.
The emissions limits must be included in the proposed permit submitted
for public comment, as well as the final permit. BACT emission limits or
conditions must be met on a continual basis at all levels of operation (e.g.,
limits written in pounds/MMbtu or percent reduction achieved), demonstrate
protection of short term ambient standards (limits written in pounds/hour) and
be enforceable as a practical matter (contain appropriate averaging times,
compliance verification procedures and recordkeeping requirements).
Consequently, the permit must:
o be able to show compliance or noncompliance (i.e., through
monitoring times of operation, fuel input, or other Indices
of operating conditions and practices); and
o specify a reasonable averaging time consistent with established
reference methods, contain reference methods for determining
compliance, and provide for adequate reporting and
recordkeeping so that the permitting agency can determine
the compliance status of the source.
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VII. EXAMPLE BACT ANALYSES FOR GAS TURBINES
/Vote: The following example provided is for Illustration only. The example
source 1s fictitious and has been created to highlight many of the aspects of
the top-down process. Finally, It must be noted that the cost data and other
numbers presented in the example are used only to demonstrate the BACJ decision
making process. Cost data are used In a relative sense to compare control costs
among sources In a source category or for a pollutant. Mo absolute cost
guidelines have been established above which costs are assumed to be too high
or below which they are assumed reasonable. Determination of appropriate costs
is made on a case-by-case basis.
In this section a BACT analysis for a stationary gas turbine project Is
presented and discussed under three alternative operating scenarios:
o Example I—Simple Cycle Gas Turbines Firing Natural Gas
>
o Example 2--Combined Cycle Gas Turbines Firing Natural Gas
o Example 3--Combined Cycle Gas Turbines Firing Distillate Oil
The purpose of the examples are to illustrate points to be considered in
developing BACT decision criteria for the source under review and selecting
BACT. They are intended to illustrate the process rather than provide
universal guidance on what constitutes BACT for any particular source
category. BACT wist be determined on a case-by-case basis.
These examples are not based on any actual analyses performed for the
purposes of obtaining a PSD per»1t. Consequently, the actual emission rates,
costs, and design parameters used are neither representative of any actual
case nor do they apply to any particular facility.
58
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Harch 15. 1990
VILA. EXAMPLE 1--SIMPLE CYCLE GAS TURBINES FIRING NATURAL GAS
VII.A.l PROJECT SWfWRY
Table VII-1 presents project data, stationary gas design parameters, and
uncontrolled emission estimates for the new source 1n example 1. The gas
turbine 1s designed to provide peaking service to an electric utility. The
planned operating hours are less than 1000 hours per year. Natural gas fuel
will be fired. The source will be limited through enforceable conditions to
the specified hours of operation and fuel type. The area where the source is
to be located is in compliance for all criteria pollutants. No other changes
are proposed at this facility, and therefore the net emissions change will be
equal to the emissions shown on Table VII-1. Only NOX emissions are
significant (i.e., greater than the 40 tpy significance level for NOX) and a
BACT analysis is required for NOX emissions only.
VII.A.2. BACT ANALYSIS SUffWRY
VII.A.Z.a. CONTROL TECHNOLOGY OPTIONS
The first step in evaluating BACT is identifying all candidate control
technology options for the emissions unit under review. Table VII-2 presents
the list of control technologies selected as potential BACT candidates. The
first three control technologies, wet injection and selective catalytic
reduction, were identified by a review of existing gas turbine facilities in
operation. Wet injection can mean either water or steam injection.
Selective noncatalytic reduction was identified as a potential type of control
technology because it 1s an add-on NOX control which has been applied to other
types of combustion sources.
In this exanple, the control technologies were Identified by the
applicant based on a review of the BACT/LAER Clearinghouse, and discussions
with State agencies with experience permitting gas turbines 1n NOX
nonattainment areas. A preliminary meeting with the State permit Issuing
agency was held to determine whether the permitting agency felt that any other
59
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TABLE VII-1. EXAMPLE 1-COMBUSTION TURBINE DESIGN PARAMETERS
Characteristics
Number of emissions units
Unit Type
Cycle Type
Output
Exhaust temperature,
Fuel(s)
Heat rate, Btu/kw hr
Fuel flow, Btu/hr
Fuel flow, Ib/hr
Service Type
Operating Hours (per year)
Uncontrolled Emissions, tpy(a)
N0y
SOo
or
VOC
PM
1
Gas Turbines
Simple-cycle
75 HW
1,000 °F
Natural Gas
11,000
1,650 mill ion
83,300
Peaking
1,000
564 (169 ppm)
4.6 (6 ppm)
1
5 (0.0097 gr/dscf)
(a) Based on 1000 hours per year of operation at full load.
60
-------
TABLB VII-2.
EXAMPLE 1—SUMMARY OF POTENTIAL NOx CONTROL
TECHNOLOGY OPTIONS
Control technology(a)
Selective Catalytic
Reductions
Water Injection
Steam Injection
low NOx Burner
Selective Noncatalytic
Reduction
Typical
control
efficiency
range
(X reduction)
40-90
30-70
30-70
30-70
20-50
Simple
cycle
turbines
No
Yes
No
Yes
No
In Service On:
Combined
cycle
gas
turbines
Yes
Yes
Yes
Yes
Yes
Other
conbust Ion
sources (c)
Yes
Yes
Yes
Yes
Yes
Technically
feasible on
simple cycle
turbines
Yes(b)
Yes
No
Yes
No
(a) Ranked in order of highest to lowest stringency.
(b) Exhaust must be diluted with air to reduce its temperature to 600-750*F.
(c) Boiler incinerators, etc.
61
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March 15. 1990
applicable control technologies should be evaluated and they agreed on the
proposed control hierarchy.
VII.A.2.b. TECHNICAL FEASIBILITY CONSIDERATIONS
Once potential control technologies have been identified, each technology
is evaluated for its technical feasibility based on the characteristics of the
source. Because the gas turbines in this example are intended to be used for
peaking service, a heat recovery steam generator (HRSG) will not be included.
A HRSG recovers heat from the gas turbine exhaust to make steam and increase
overall energy efficiency. A portion of the steam produced can be used for
steam injection for NOX control, sometimes increasing the effectiveness of the
net injection control system. However, the electrical demands of the grid
dictate that the turbine will be brought on line only for short periods of
time to meet peak demands. Due to the lag time required to bring a heat
recovery steam generator on line, it is not technically feasible to use a HRSG
at the facility. Use of an HRSG in this instance was shown to interfere with
the performance of the unit for peaking service, which requires immediate
response times for the turbine. Although it was shown that a HRSG was not
feasible, water and steam are readily available for NOX control since the
turbine will be located near an existing steam generating powerplant.
The turbine type and, therefore, the turbine model selection process,
affects the achievability of NOX emissions limits. Factors which the customer
considered in selecting the proposed turbine model were outlined in the
application as: the peak demand which must be net, efficiency of the gas
turbine, reliability requirements, and the experience of the utility with the
operation and Maintenance service of the particular manufacturer and turbine
design. In this exaaple, the proposed turbine Is equipped with a coobustor
62
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. (torch 15. 1990
designed to achieve an emission level, at 15 percent 0?, of 25 ppm NCL with
i *• *
steam Injection or 42 ppm with water injection.
Selective noncatalytic reduction (SNCR) was eliminated as technically
Infeaslble because this technology requires a flue gas temperature of 1300 to
2100°F. The exhaust from the gas turbines will be approximately 1000°F, which
Is below the required temperature range.
Selective catalytic reduction (SCR) was evaluated and no basis was found
to eliminate this technology as technically infeasible. However, there are no
known examples where SCR technology has been applied to a simple-cycle gas
turbine or to a gas turbine in peaking service. In all cases where SCR has
been applied, there was an HRSG which served to reduce the exhaust temperature
to the optimum range of 600-750°F and the gas turbine was operated
continuously. Consequently, application of SCR to a simple cycle turbine
involves special circumstances. For this example, 1t is assumed that dilution
air can be added to the gas turbine exhaust to reduce its temperature.
However, the dilution air will make the system more costly due to higher gas
flows, and may reduce the removal efficiency because the NOX concentration at
the inlet will be reduced. Cost considerations are considered later in the
analysis.
VII.A.2.C. CONTROL TECHNOLOGY HIERARCHY
After deterrain ing technical feasibility, the applicant selected the
control levels for evaluation shown In Table VII-3. Although the applicant
reported that some sites in California have achieved levels as low as 9 ppti,
at this facility a 13 ppn level was determined to be the feasible llait with
SCR. This decision Is based on the lowest achievable level with steaa
Injection of 25 ppffl and an SCR removal efficiency of 50 percent. Even though
1 For some gas turbine models, 25 ppm is not achievable with either water
or steam injection.
63
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TABLE VII-3. EXAMPLE 1--COMTROL TECHNOLOGY HIERARCHY
Control Technology
Emissions
Steam Injection plus SCR
Steam Injection at maximum*5) design rate
Water Injection at maximum^5) design rate
Steam Injection to meet NSPS
•
(a) Corrected to 15 percent oxygen.
(b) Water to fuel ratio.
ppm(a)
13
25
42
93
TRY
44
84
140
312
64
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-DRAFT-
Harch IS. 1990
the reported removal efficiencies for SCR are up to 90 percent at some
facilities, at this facility the actual NOX concentration at the inlet to the
SCR system will only be approximately 17 ppm (at actual conditions) due to the
dilution air required. Also the inlet concentrations, flowrates, and
temperatures will vary due to the high frequency of startups. These factors
make achieving the optimum 90 percent NOX removal efficiency unrealistic.
Based on discussions with SCR vendors, the applicant has established a
50 percent removal efficiency as the highest level achievable, thereby
resulting in a 13 ppm level (I.e., 50 percent of 25 ppm).
The next most stringent level achievable would be steam injection at the
maximum water-to-fuel ratio achievable by the unit within its design operating
range. For this particular gas turbine model, that level is 25 ppm as
supported by vendor NO emissions guarantees and unit test data. The
applicant provided documentation obtained from the gas turbine manufacturer2
verifying ability to achieve this range.
After steam injection the next most stringent level of control would be
water injection at the maximum water-to-fuel ratio achievable by the unit
within its design operating range. For this particular gas turbine model,
that level is 42 ppm as supported by vendor NOX emissions guarantees and
actual unit test data. The applicant provided documentation obtained from the
gas turbine manufacturer verifying ability to achieve this range.
The least stringent level evaluated by the applicant was the current NSPS
for utility gas turbines. For this model, that level 1s 93 ppm at 15 percent
02. By definition, BACT can be no less stringent than NSPS. Therefore, less
stringent levels are not evaluated.
2 It should be noted that achievability of the NOX limits 1s dependent
on the turbine model, fuel, type of wet injection (water or steam), and system
design. Not all gas turbine models or fuels can necessarily achieve these
levels.
65
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March 15. 1990
VII.A.2.d. IMPACTS ANALYSIS SUMMARY
The next steps completed by the applicant were the development of the
cost, economic, environmental and energy impacts of the different control
alternatives. Although the top-down process would allow for the selection of
the top alternative without a cost analysis, the applicant felt cost/economic
impacts were excessive and that appropriate documentation «ay justify the
elimination of SCR as BACT and therefore chose to quantify cost and economic
impacts. Because the technologies in this case are applied in combination, it
was necessary to quantify impacts for each of the alternatives. The impact
estimates are shown in Table VII-4. Adequate documentation of the basis for
the impacts was determined to be included in the PSD permit application.
The incremental cost impacts shown are the cost of the alternative
compared to the next most stringent control alternative. Figure VII-1 Is a
plot of the least-cost envelope defined by the list of control options.
VII.A.2.e. TOXICS ASSESSMENT
Potential toxic emissions which could occur as a result of this facility
would be ammonia if SCR were applied. Ammonia emissions resulting from
application of SCR could be as large as 20 tons per year. Application of SCR
would reduce NOX by an additional 20 tpy over steam injection alone
(25 ppm)(not including ammonia emissions).
Another environmental impact considered was the spent catalyst which
would have to be disposed of at certain operating Intervals. The catalyst
contains vanadium pentoxide, which is listed as a hazardous waste under RCRA
regulations (40 CFR 261.3). Disposal of this waste creates an additional
66
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TABU VIM. EXAMPLE 1--SUMMMY OF TOP-DOW BUT IMPACT AHALYSIS FEULT3 FOR IOM
Unions Wl Turbine Econonic Imacts
Installed Total Cost
Emissions capital annual lied effectiveness
Missions ra)uction(a) cost(b) cost(c) over baseline(d)
Control alternative (Ib/hr) (tpy) (tpy) ($) ($/yr) ($/ton)
13 ppa Alternative 44 22 260 11,470,000 l,717,000(g) 6,600
25 ppB Alternative 84 42 240 1,790,000 593,000 2,470
42 ppl Alternative 140 70 212 1,304,000 356,000 1,680
KSPS Alternative 312 156 126 927,000 288,000 2,283
Uncontrolled Baseline 564 282 -
Enerav Isoacts Environmental bracts
Incraental
Increnental Increase Adverse
cost over Toxics envlronwntal
effectiveness(e) baseline(f) iapact bqact
($/ton) (MKBtu/yr) (Yes/ No) (Yes /Ho)
56,200 464,000 Yes No
8,460 30,000 No No
800 15,300 NO NO
8,000 NO No
(a) Emissions reduction over baseline control level.
(b) Installed capital cost relative to baseline.
(c) Total annualiied cost (capital, direct, and indirect) of purchasing, installing, and operating the proposed control alternative. A capital
recovery factor approach using a real Interest rate (i.e., absent Inflation) is used to express capital costs in present-day annual costs.
(d) Cost Effectiveness over baseline is equal to total annualited cost for the control option divided by the Missions reductions resulting free the
uncontrolled baseline.
(e) The optional Incremental cost effectiveness criteria is the sane as the total cost effectiveness criteria except that the control alternative
is considered relative to the next vet stringent alternative rather than the baseline control alternative.
(f) Energy ispacts are the difference in total project energy requirenents tilth the control alternative and the baseline control alternative
expressed in equivalent •!11ions of Btus per year.
(g) Assued 10 year catalyst life since this turbine operates only 1000 hours per year. Assiaptlons Bade on catalyst life My have a profound affect
upon cost effectiveness.
67
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DRAFT
Figure VIM. Least-Cost Envelope for Example 1
2,000,000
1,500,000
o
Q.
to
O
° 1,000,000
"U
O
D
C
i
500,000
13ppmi
NSPS
50 100 150 200 250 300
Emissions Reduction (tons per year)
68
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-DRAFT-
Harch IS. 1990
economic and environmental burden. This was considered in the applicant's
proposed BACT determination.
VII.A.2.f. RATIONALE FOR PROPOSED BACT
Based on these Impacts, the applicant proposed eliminating the 13 ppm
alternative as economically infeasible. The applicant documented that the
cost effectiveness 1s high at 6,600 $/ton, and well out of the range of recent
BACT NOX control costs for similar sources. The Incremental cost
effectiveness of $56,200 also is high compared to the Incremental cost
effectiveness of the next option.
The applicant documented that the other combustion turbine sources which
have applied SCR have much higher operating hours (I.e., all were permitted as
base-loaded units). Also, these sources had heat recovery steam generators so
that the cost effectiveness of the application of SCR was lower. For this
source, dilution air must be added to cool the flue gas to the proper
temperature. This increases the cost of the SCR system relative to the same
gas turbine with a HRSG. Therefore, the other sources had much lower cost
impacts for SCR relative to steam injection alone, and much lower cost
effectiveness numbers. Application of SCR would also result in emission of
ammonia, a toxic chemical, of possibly 20 tons per year while reducing NOX
emissions by 20 tons per year. The applicant asserted that, based on these
circumstances, to apply SCR in this case would be an unreasonable burden
compared to what has been done at other similar sources.
Consequently, the applicant proposed eliminating the SCR plus steam
Injection alternative. The applicant then accepted the next control
alternative, steam Injection to 25 ppmv. The review authority concurred with
the proposed elimination of SCR and the selection of a 25 ppav 11«1t as BACT.
69
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March 15. 1990
VII.B. EXAMPLE 2--COMBINED CYCLE GAS TURBINES FIRING NATURAL GAS
Table VII-5 presents the design parameters for an alternative set of
circumstances. In this example, two gas turbines are being Installed. Also,
the operating hours are 5000 per year and the new turbines are being added to
meet Intermediate loads demands. The source will be limited through
enforceable conditions to the specified hours of operation and fuel type. In
this case, HRSG units are installed. The applicable control technologies and
control technology hierarchy are the same as the previous example except that
no dilution is required for the gas turbine exhaust because the HRSG serves to
reduce the exhaust temperature to the optimum level for SCR operation. Also,
since there is no dilution required and fewer startups, the most stringent
control option proposed is 9 ppm based on performance limits for several other
natural gas fired baseload combustion turbine facilities.
Table VII-6 presents the results of the cost and economic Impact analysis
for the example and Figure VII-2 is a plot of the least-cost envelope defined
by the list of control options. The incremental cost impacts shown are the
cost of the alternative compared to the next most stringent control
alternative. Due to the increased operating hours and design changes, the
economic impacts of SCR are much lower for this case. There does not appear
to be a persuasive argument for stating that SCR is economically infeasible.
Cost effectiveness numbers are within the range typically required of this and
other similar source types.
In this case, there would also be emissions of ammonia. However, now the
magnitude of ammonia emissions, approximately 40 tons per year, Is much lower
than the additional NOX reduction achieved, which Is 270 tons per year.
Under these alternative circumstances, PM emissions are also now above
the significance level (i.e., greater than 25 tpy). The gas turbine
70
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TABLE VII-5. EXAMPLE 2--COMBUS7IO* TURBINE DESIGN PARAMETERS
Characteristics
Number of emission units
Emission units
Cycle Type
Output
Gas Turbines (2 & 75 MW each)
Steam Turbine (no emissions generated)
Fuel(s)
Gas Turbine Heat Rate, Btu/kw-hr
Fuel Flow per gas turbine, Btu/hr
Fuel Flow per gas turbine, Ib/hr
Service Type
Hours per year of operation
Uncontrolled Emissions per gas turbine, tpy (a)(b)
NOX
so2
CO
voc
PM
Gas Turbine
Combined-cycle
150 MW
70 MW
Natural Gas
11,000 BtuAw-hr
1,650 million
83,300
Intermediate
5000
1,410 (169 ppm)
<1
23 (6 ppm)
5
25 (0.0097 gr/dscf)
(a) Based on 5000 hours per year of operation.
(b) Total uncontrolled emissions for the proposed project is equal to the
pollutants uncontrolled emission rate multiplied by 2 turbines. For example,
total NOX - (2 turbines) x 1410 tpy per turbine) - 2820 tpy.
71
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TABU VII-6. EXAMPLE 2--SIHMMT OF TOP-DOM BUT HPICT MM.TSIS RESULTS FOR ».
Missions oar Turbine
Economic Iroacts
Control alternative
Installed
Missions capital
Missions reduction(a,h) oost(b)
(lb/hr)(tpT) (tpy) ($)
Energy Impacts
Incremental
Total Cost Increaental increase Mverse
annualized effectiveness cost over Toxics envinwental
oost(c) over baseline(d) effectlveness(e) baseline(f) iopact intact
($/yr) ($/ton) ($/ton) (KMBtu/yr) (fes/Ho) (Tes/Ho)
9 ppi Alternative
25 ppi Alternative
42 ppn Alternative
KSPS Alternative
Uncontrolled Baseline
30
84
140
312
564
75
210
350
780
1,410
1,335
1,200
1,060
630
•
10,980,000
1,791,000
1,304,000
927,000
•
3,380,000(9)
1,730,000
883,000
805,000
-
2,531
1,440
633
1,280
-
12,200 160,000
6,050 105,000
181 57,200
27,000
•
Yes
No
No
No
*
No
No
No
No
*
(a) Missions reduction over baseline control level.
(b) Installed capital cost relative to baseline.
(c) Total annuallied cost (capital, direct, ahd indirect) of purchasing, installing, and operating the proposed control alternative. A capital
recovery factor approach using a real interest rate (i.e., absent inflation) is used to express capital costs in present-day annual costs.
(d) Cost Effectiveness over baseline is equal to total annualited cost for the control option divided by the Missions reductions resulting fro> the
uncontrolled baseline.
(e) The optional increaental cost effectiveness criteria is the saw as the total cost effectiveness criteria except that the control alternative
Is considered relative to the next wst stringent alternative rather than the baseline control alternative.
(f) Energy Impacts are the difference in total project energy requirements with the control alternative and the baseline control alternative
expressed in equivalent lillions of Btus per year.
(g) ASSIBBS a 2 fear catalyst life. Assumptions Bade on catalyst life lay have a profound affect upon cost effectiveness.
(h) Since the project calls for t» turbines, actual project Hide Missions reductions for an alternative i»lll be equal to two tiaes the reduction
listed.
72
-------
Figure VII-2. Least-Cost Envelope for Example 2
4,000,000
3,000,000
(0
0>
Gu
8
O 2,000,000
0)
"(5
D
C
H 1,000,000
9ppm
NSPS
0 200 400 600 800 1,000 1,200 1,400 1,600
Emissions Reduction (tons per year)
73
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-DRAFT-
Harch 15. 1990
combustors are designed to combust the fuel as completely as possible and
therefore reduce PM to the lowest possible level. Natural gas contains no
solids and solids are removed from the Injected water. The PM emission rate
without add-on controls is on the same order (0.009 gr/dscf) as that for other
partlculate matter sources controlled with stringent add-on controls (e.g.,
fabric filter). Since the applicant documented that precorobustlon or add-on
controls for PM have never been required for natural gas fired turbines, the
reviewing agency accepted the applicants analysis that natural gas firing was
BACT for PM emissions and that no additional analysis of PM controls was
required.
VII.C. EXAMPLE 3-COMBINED CYCLE GAS TURBINE FIRING DISTILLATE OIL
In this example, the same combined cycle gas turbines are proposed
except that distillate oil 1s fired rather than natural gas. The reason is
that natural gas is not available on site and there is no pipeline within a
reasonable distance. The fuel change raises two issues; the technical
feasibility of SCR in gas turbines firing sulfur bearing fuel, and NOX levels
achievable with water injection while firing fuel oil.
In this case the applicant proposed to eliminate SCR as technically
infeasible because sulfur present in the fuel, even at low levels, will poison
the catalyst and quickly render it ineffective. The applicant also noted that
there are no cases in the U.S. where SCR has been applied to a gas turbine
firing distillate oil as the primary fuel.3
A second Issue would be the most stringent NOX control level achievable
with wet Injection. For oil firing the applicant has proposed 42 ppn at
15 percent oxygen. Due to flame characteristics Inherent with oil firing, and
Units on the amount of water or steam that can be Injected, 42 ppa 1s the
Though this argument was considered persuasive in this case, advances
in catalyst technology have now made SCR with oil firing technically feasible.
74
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-DRAFT-
Harch IS. 1990
lowest NOX emission level achievable with distillate oil firing. Since
natural gas 1s not available and SCR is technically Infeasible, 42 pptn 1s the
most stringent alternative considered. Based on the cost effectiveness of wet
Injection, approximately 833 $/ton, there is no economic basis to eliminate
the 42 ppro option since this cost Is well within the range of BACT costs for
NO control. Therefore, this option is proposed as BACT.
x
The switch to oil from gas would also result in S02, CO, PM, and
beryllium emissions above significance levels. Therefore, BACT analyses would
also be required for these pollutants. These analyses are not shown 1n this
example, but would be performed in the same manner as the BACT analysis for
NOX.
VII.D. OTHER CONSIDERATIONS
The previous judgements concerning economic feasibility were in an area
meeting NAAQS for both NOX and ozone. If the natural gas fired simple cycle
gas turbine example previously presented were sited adjacent to a Class I
area, or where air quality improvement poses a major challenge, such as next
to a nonattainment area, the results may differ. In this case, even though
the region of the actual site location is achieving the NAAQS, adherence to a
local or regional NOX or ozone attainment strategy might result in the
determination that higher costs than usual are appropriate. In such
situations, higher costs (e.g., 6,600 $/ton) may not necessarily be persuasive
in eliminating SCR as BACT.
While 1t 1s not the Intention of BACT to prevent construction, 1t Is
possible that local or regional air quality aanagenent concerns regarding the
need to «1n1»1ze the air quality Impacts of new sources would lead the
permitting authority to require a source to either achieve stringent Mission
control levels or, at a minimum, that control cost expenditures aeet certain
cost levels without consideration of the resultant economic Impact to the
source.
75
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-DRAFT-
Karch 15. 1990
Besides local or regional air quality concerns, other site constraints
may significantly impact costs of particular control technologies. For the
examples previously presented, two factors of concern are land and water
availability.
The cost of the raw water is usually a small part of the cost of wet
controls. However, gas turbines are sometimes located in remote locations.
Though water can obviously be trucked to any location, the costs may be very
high.
Land availability constraints may occur where a new source is being
located at an existing plant. In these cases, unusual design and additional
structural requirements could make the costs of control technologies which are
commonly affordable prohibitively expensive. Such considerations »ay be
pertinent to the calculations of impacts and ultimately the selection of BACT.
76
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ttoreh 15. 1990
APPENDIX A
DEFINITION OF SELECTED TERMS
-------
APPENDIX ft - DEFINITION OF SELECTED RSR TERNS
Best Available Control Technology is the control level required for sources subject to PSD. Fran the regulation
(reference 40 CFR 52.21(b)) BACT mans "an emissions linitation (including a visible emission standard) based on the
•lira degree of reduction for each pollutant subject to regulation under the Clean ftir Act which would be emitted
froi any proposed najor stationary source or najor modification which the Administrator, on a case-by-case basis,
taking into account energy, environmental, and economic impacts and other costs, determines is achievable for such
source or modification through application of production processes or available methods, sysUns, and techniques,
including fuel cleaning or treatment or innovative fuel combustion techniques for control of such pollutant. In no
event shall application of best available control technology result in emissions of any pollutant which would exceed
the Missions allowed by any applicable standard under 40 CFR Parts 60 and 61. If the Administrator determines that
technological or economic limitations on the application of measurement methodology to a particular emissions unit
would make the imposition of an emissions standard infeasible, a design, equipment, work practice, operational
standard, or combination thereof, may be prescribed instead to satisfy the requirement for the application of best
available control technology. Such standard shall, to the degree possible, set forth the emissions reduction
achievable by implementation of such design, equipment, work practice or operation, and shall provide for compliance
by means which achieve equivalent results."
Emission Units The Individual emitting facilities at a location that together make up the source. From the regulation (reference
40 CFR S2.21(b))f it means "any part of a stationary source which emits or would have the potential to emit any
pollutant subject to regulation under the Act."
Intrants The mini permissible level of air quality deterioration that may occur beyond the baseline air quality level.
Increments were defined statutorily by Congress for SOj and PH. Recently EPA also has promulgated increments for
RD|. Increment is consumed or expanded by actual emissions changes occurring after the baseline date and by
construction related actual emissions changes occurring after January 6, 1975, and February 8, 1988 for PM/SOj and
R0_, respectively.
A - l
-------
APPENDIX A - DEFINITION OP SELECTED KSR TERNS (Continued)
Innovative Control
Technology Proi the regulation (reference 40 CPU 52.21(b)(19)) "Innovative control technology" nans any systei of air
pollution control that has not been adequately demonstrated in practice, but would have a substantial likelihood of
achieving greater continuous missions reduction than any control systea in current practice or of achieving at
least cnparable reductions at loner cost In terns of energy, econonics, or nonalr quality environmental bracts.
Special delayed compliance provisions exist that nay be applied when applicants propose innovative control
techniques.
LAEB Lowest Achievable Eoissions Rate is the control level required of a source subject to nonattainoent review. Fron
the regulations (reference 40 CFR 51.165(a)), it means for any source "the more stringent rate of emissions based on
the following:
(a) The most stringent missions limitation which is contained in the implementation plan of any State for such
class or category of stationary source, unless the owner or operator of the proposed stationary source demonstrates
that such 1 inflations are not achievable; or
(b) The aost strir. nt emissions limitation which Is achieved in practice by such class or category of stationary
sources. This limitation, when applied to a modification, means the lowest achievable missions rate of the new or
modified missions units within a stationary source. In no event shall the application of the term peralt a
proposed new or modified stationary source to emit any pollutant in excess of the amount allowable under an
applicable new source standard of performance."
A - 2
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APPENDIX A - DEFIHITION OP SELECTED HSR TERMS (Continued)
DRAFT
ft major modification is a modification to an existing major stationary source resulting in a significant net
Missions increase (defined elsewhere in this table) that, therefore, is subject to PSD review. From the regulation
(reference 40 CFR 52.21(b)(2)):
"(1) 'Major modification' means any physical change in or change in the method of operation of a major stationary
source that would result in a significant net emissions increase of any pollutant subject to regulation under the
Act.
(11) Any net emissions increase that is significant for volatile organic coapounds shall be considered significant
for ozone.
(Hi) A physical change or change in the method of operation shall not include:
(a) routine maintenance, repair and replacement;
(c) use of an alternative fuel by reason of an order or rule under Section 125 of the Act;
(d) Use of an alternative fuel at a steam generating unit to the extent that the fuel is generated fron municipal
solid waste;
(e) Use of an alternative fuel or raw material by a stationary source which:
(1) The source was capable of accoroodating before January 6, 1975, unless such change would be prohibited under any
Federally enforceable Derail condition which was established after January 6, 1975, pursuant to 40 CFR 52.21 or
under regulations approved pursuant to 40 CFR Subpart I or 40 CFR 51.166; or
(2) The source is approved to use under any permit Issued under 40 CFR 52.21 or under regulations approved pursuant
to 40 CFR 51.166;
(f) an Increase in the hours of operation or in the production rate, unless such change would be prohibited under
any federally enforceable permit condition which was established after January 6, 1975, pursuant to 40 CFR 52.21 or
under regulations approved pursuant to 40 CFR Subpart I or 40 CFR 51.166; or
(g) any change In ownership at a stationary source."
A - 3
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APPENDIX A - DEFINITION Of SELECTED RSR TEPKS (Continued)
DRAFT
Major Stationary Source A njor stationary source is an emissions source of sufficient size to warrant PSD revieii. Major modification to
Mjor stationary sources are also subject to PSD review. Prcn the regulation (reference 40 CFR 52.21(b)(l)), (i)
"Major stationary source" means:
"(a) Any of the following stationary sources of air pollutant which emits, or has the potential to enit, 100 tons
per fear or nore of any pollutant subject to regulation under the Act: Fossil fuel-fired stean electric plants of
nre than 250 million British thermal units per hour heat input, coal cleaning plants (with thermal dryers), Kraft
pulp tills, Portland cement plants, primary zinc smelters, iron and steel sill plants, prliary aluinin ore
reduction plants, primary aluminum ore reduction plants, primary copper snelters, nunicipal incinerators capable of
charging nre than 250 tons of refuse per day, hydrofluoric, sulfuric, and nitric acid plants, petrolem refineries,
line plants, phosphate rock processing plants, coke oven batteries, sulfur recovery plants, carbon black plants
(furnace process), primary lead snelters, fuel conversion plants, sintering plants, secondary netal production
plants, chealcal process plants, fossil fuel boilers (or combinations thereof) totaling nre than 250 Billion
British thenal units per hour heat input, petrolein storage and transfer units with a total storage capacity
exceeding 300,000 barrels, taconite ore processing plants, glass fiber processing plants, and charcoal production
plants;
(b) notwithstanding the stationary source sire specified in paragraph (b)(l)(i) of this section, any stationary
source which enits, or has the potential to enit, 250 tons per year or nre of any air pollutant subject to
regulation under the Act; or
(c) Any physical change that would occur at a stationary source not otherwise qualifying under paragraph (b)(l) as a
•ajor stationary source not otherwise qualifying under paragraph (b)(l) as a Major stationary source, if the changes
wuld constitute a ujor stationary source by itself.
(li) A tajor stationary source that is ujor for volatile organic conounds shall be considered najor for ozone."
National Avient Air Quality Standards are Federal standards for the linlra anbient air quality needed to protect
public health and welfare. They have been set for six criteria pollutants including SO,, PM/PM10, »„, CO, 0,
(WC), and Pb.
X - 4
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APPENDIX A - DEFINITION OP SELECTED HSR TERNS (Continued)
DRAFT
KESHAP
HSPS
PSD
Regulated Pollutants'
HESHAP, or national Emission Standard for Hazardous Air Pollutants, is a technology-based standard of performance
prescribed for hazardous air pollutants fron certain stationary source categories under Section 112 of the Clean Mr
Act. Where they apply, NESHAP represent absolute mininun requirements for BACT.
HSPS, or Ken Source Performance Standard, is an mission standard prescribed for criteria pollutants froa certain
stationary source categories under Section 111 of the Clean Air Act. Where they apply, KSPS represent absolute
•iniwi requirements for BACT.
Prevention of significant deterioration is a construction air pollution permitting program designed to ensure air
quality does not degrade beyond the NAACjS levels or beyond specified incremental amounts above a prescribed baseline
level. PSD also ensures application of BACT to major stationary sources and major modifications for regulated
pollutants and consideration of soils, vegetation, and visibility Impacts in the permitting process.
Refers to pollutants that have been regulated under the authority of the Clean Air Act (NAAQS, KSPS, KESHAP):
0, (VOC)- Ozone, regulated through volatile organic compounds as precursors
NO. - Nitrogen oxides
- Sulfur dioxide
j- Total suspended participate matter
,) - Particulate matter with <10 nicron aerometric diameter
- Carbon lonoxide
SO,
PM(TSP)
PM (PK10
CO
Pb
As
Be
Bg
vt
F
- Lead
- Asbestos
- Berylliui
- Mercury
- Vinyl chloride
- Fluorides
- Sulfuric acid list
- Hydrogen sulfide
TRS -Total reduced sulfur (including H,S)
RDS - Reduced Sulfur Coopounds (including H,S)
Bz - Benzene
Rd - Radionuclides
As - Arsenic
CFC's - Chlorofluorocarbons
Rn-222 - Radon-222
HaIons
1 The referenced list of regulated pollutants is current as of Hoveaber 1989. Presently, additional pollutants nay also be subject to regulation
under the Clean Air let.
A - 5
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APPENDIX \ - DEPIKITION OF SELECTED HSR TEWS (Continued)
DRAFT
Significant Emissions Increase For neti aajor stationary sources and major modifications, a significant missions increase triggers PSD review.
Review requirements must be met for each pollutant undergoing a significant net emissions Increase. From the
regulation (reference 40 CFR 52.21(b)(23)).
(1) "Significant" means, in reference to a net eaissions increase from a aodified najor source or the potential of a
new tajor source to emit any of the following pollutants, a rate of eaissions that would equal or exceed any of the
following rates:
Carbon •onoilde: 100 tons per year (tpy)
lltrogen oxides: 40 tpy
Sulfur dioxide: 40 tpy
Partlculate utter: 25 tpy
PMlOi is tpy
OtOMt 40 tpy of volatile organic compounds
Lead: 0.6 tpy
Asbestos: 0.007 tpy
torylliw: 0.0004 tpy
Mercury: 0.1 tpy
Vinyl chloride: 1 tpy
fluorides: 3 tpy
Sulfurlc acid nist: 7 tpy
Hydrogen Sulfide (H^S): 10 tpy
total reduced sulfur (including H,s): 10 tpy
Reduced sulfur compounds (including H2S): 10 tpy
(11) "Significant" means, in reference to a net eaissions increase or the potential of a source to eait a pollutant
subject to regulation under the Act, that (i) above does not list, any emissions rate.
(For exanple, benzene and radionuclldes are pollutants falling into the "any emissions rate" category.)
(Hi) notwithstanding, paragraph (b)(23)(i) of this section, "significant deans any eaissions rate or any net
eaissions increase associated with a major stationary source or aajor aodification which would construct within 10
klloaeters of a Class I area, and have an lapact on such an area equal to or greater than 1 ug/mj, (24-hour
average).
A - 6
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ftPPEHDR A - DEPIHITIOH OF SELECTED HSR TERMS (Continued)
DRAFT
Sip State lamentation Plan is the federally approved State (or local) air quality nanageaent authority's statutory
plan for attaining and maintaining the NMQS. Generally, this refers to the State/local air quality rules and
peraittlng requirements that have been accepted by EPA as evidence of an acceptable control strategy.
Stationary Source For PSD purposes, refers to all emissions units at one location under canon ownership or control. Fran the
regulation (reference 40 CFR 52.21(b)(5) and 51.166(b)(5)), it means "any building, structure, facility, or
Installation which emits or may emit any air pollutant subject to regulation under the Ret."
"Building, structure, facility, or installation" means all of the pollutant-emitting activities which belong to the
saw industrial grouping, are located on one or more contiguous or adjacent properties, and are under the control of
the sane person (or person under cotnnon control). Pollutant-emitting activities shall be considered as part of the
saae industrial grouping if they belong to the sane "Major Croup" (i.e., which have the sane first two digit code)
as described in the Standard Industrial Classification Manual, 1972, as amended by the 1977 Supplement
(U.S. Governnent Printing Office stock nunbers 4101-0066 and 003-005-00176-0, respectively).
ft - 7
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-DRAFT-
Narch IS. 1990
APPENDIX B
ESTIMATING CONTROL COSTS
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-DRAFT-
Hirch 15. 1990
APPENDIX B - ESTIMATING CONTROL COSTS
I. CAPITAL COSTS
Capital costs include equipment costs, installation costs, indirect
costs, and working capital (if appropriate). Figure B-l presents the
elements of total capital cost and represents a building block approach that
focuses on the control device as the basic unit of analysis for estimating
total capital investment. The total capital investment has a role in the
determination of total annual costs and cost effectiveness.
One of the most common problems which occurs when comparing costs at
different facilities is that the battery limits are different. For example,
the battery limit of the cost of a electrostatic precipitation Bight be the
precipitator itself (housing, plates, voltage regulators, transformers, etc.),
ducting from the source to the precipitator, and the solids handling system.
The stack would not be included because a stack will be required regardless of
whether or not controls are applied. Therefore, it should be outside the
battery limits of the control system.
Direct installation costs are the costs for the labor and materials to
install the equipment and includes site preparation, foundations, supports,
erection and handling of equipment, electrical work, piping, insulation and
painting. The equipment vendor can usually supply direct installation costs.
The equipment vendor should be able to supply direct installation costs
estimates or general Installation costs factors. In addition, typical
installation cost factors for various types of equipment are available in the
following references.
o OAQPS Control Cost Manual (Fourth Edition), January 1990,
EPA 450/3-90-006
o Control Technology for Hazardous Air Pollutants (HAPS) Manual.
September 1986, EPA 625/6-86-014
B-l
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FIGURE B-l. Eleoents otal Capital Costs
o Prliary Cootrol Device
o toalllary Bqulpnnt
(Including doctwrt)
o ftdlf loitloB to Otter Bqulpawt
o InatruMBtatloo (a)
o Sales Taws (a)
o might (a)
Purchased
Equipment
Cost
o Foundation and Supports
o Handling and Enctloo
o Electrical
o Piping
o Insulation
o Painting
Direct
Installation
Costs (b)
Site Preparation (c,d)
Buildings (d)
land(e)
Working Capital (e)
Total
Direct
Costs
o Engineering
o Construction and Field
o Contractor Feet
o Start-up
o Ptrfonance Tests
o Contingencies
Indirect
Installation
Costs (b)
Total
Indirect
Costs
Total
nondepreciable
Investaant
"Battery
Halts"
Costs
Off-site
Facilities (e)
Total
Depreciable
Investment
Total
Capital
Investment
(a) These costs are factored fra the sm of the control device and auxiliary equipnnt costs.
(b) These costs are factored fra the purchased control equipment.
(c) Usually required only at "grass roots" installations.
(d) Unlike the otter direct and Indirect costs, costs for these itens are not factored fra the
purchased equipwit cost. Ratter, they are sited and oosted separately.
(e) (tonally not required Nith add-on control systeas.
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-DRAFT-
Harch IS. 1990
o Standards Support Documents
Background Information Documents
Control Techniques Guidelines Documents
o Other EPA sponsored costing studies
o Engineering Cost and Economics Textbooks
o Other engineering cost publications
These references should also be used to validate any installation cost factors
supplied from equipment vendors.
If standard costing factors are used, they may need to be adjusted due to
site specific conditions. For example, in Alaska installation costs are on
the order of 40 - 50 percent higher than in the contiguous 48 states due to
higher labor prices, shipping costs, and climate.
Indirect installation costs include (but are not limited to) engineering,
construction, start-up, performance tests, and contingency. Estimates of
these costs may be developed by the applicant for the specific project under
evaluation. However, if site-specific values are not available, typical
estimates for these costs or cost factors are available in:
o OAQPS Control Cost Manual (Fourth Edition), EPA 450/3-90-006
o Cost Analysis Manual for Standards Support Documents, April 1979
These references can be used by applicants if they do not have
site-specific estimates already prepared, and should also be used by the
reviewing agency to determine if the applicant's estimates are reasonable.
Where an applicant uses different procedures or assumptions for estimating
control costs than contained In the referenced Material or outlined In this
document, the nature and reason for the differences are to be documented in
the BACT analysis.
B-3
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-DRAFT-
March IS. 1990
Working capital 1s a fund set aside to cover initial costs of fuel,
chemicals, and other materials and other contingencies. Working capital costs
for add on control systems are usually relatively small and, therefore, are
usually not included in cost estimates.
Table B-l presents an illustrative example of a capital cost estimate
developed for an ESP applied to a spreader-stoker coal-fired boiler. This
estimate shows the minimum level of detail required for these types of
estimates. If bid costs are available, these can be used rather than study
cost estimates.
II. TOTAL ANNUAL COST.
The permit applicant should use the levelized annual cost approach for
consistency in BACT cost analysis. This approach is also called the
"Equivalent Uniform Annual Cost" method, or simply "Total Annual Cost" (TAG).
The components of total annual costs are their relationships are shown 1n
Figure B-2. The total annual costs for control systems is comprised of three
elements: "direct" costs (DC), "indirect costs" (1C), and "recovery credit"
(RC), which are related by the following equation:
TAC - DC + 1C - RC
Direct costs are those which tend to be proportional or partially
proportional to the quantity of exhaust gas processed by the control system
or, in the case of Inherently lower polluting processes, the amount of
material processed or product manufactured per unit time. These include costs
for raw materials, utilities (steam, electricity, process and cooling water,
etc.), and waste treatment and disposal. Semivariable direct costs are only
partly dependent upon the exhaust or material flowrate. These Include all
associated labor, maintenance materials, and replacement parts. Although
these costs are a function of the operating rate, they are not linear
6-4
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DRAFT
TABLE B-l. EXAMPLE OF A CAPITAL COST ESTIMATE FOR AN
ELECTROSTATIC PRECIPITATOR
Capital
cost
($)
Direct Investment
Equipment cost
ESP unit 175,800
Ducting 64,100
Ash handling system 97,200
Total equipment cost 337,100
Installation costs
ESP unit 175,800
Ducting 102,600
Ash handling system 97,200
Total installation costs 375,600
Total direct investment (TDI) 712,700
(equipment + installation)
Indirect Investment 71,300
Engineering (10% of TDI) 71,300
Construction and field expenses (10% of TDI) 71,300
Construction fees (10% of TDI) 71,300
Start-up (2% of TDI) 14,300
Performance tests (minimum $2000) 3,000
Total indirect investment (Til) 231,200
Contingencies (20% of TDI + Til) 188,800
TOTAL TURNKEY COSTS (TDI + Til) 1,132,700
Working Capital (25% of total direct operating costs)a 21,100
GRAND TOTAL 1,153,800
B-5
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DRAFT
FIGURE B-2. Elements of Total Annual Costs
o Raw Materials
o Utilities
- Electricity
- Steam
- Water
- Others
o Labor
- Operating
- Supervisory
• Maintenance
o Maintenance materials
o Replacement parts
Variable
Semi variable
Direct
Annual
Costs
Total
- Annual
Costs
o Overhead
o Property Taxes
o Insurance
o Capital Recovery
o Recovered Product
o Recovered Energy
o Useful byproduct
o Energy Gain
Indirect
Annual
Costs
Recovery
Credits
B-6
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-DRAFT-
Karch 15. 1990
functions. Even while the control system is not operating, some of the
semivariable costs continue to be incurred.
Indirect, or "fixed", annual costs are those whose values are relatively
independent of the exhaust or material flowrate and, in fact, would be
incurred even if the control system were shut down. They Include such
categories as overhead, property taxes, insurance, and capital recovery.
Direct and indirect annual costs are offset by recovery credits, taken
for materials or energy recovered by the control system, which may be sold,
recycled to the process, or reused elsewhere at the site. These credits, in
turn, may be offset by the costs necessary for their purification, storage,
transportation, and any associated costs required to make then reusable or
resalable. For example, in auto refinishing, a source through the use of
certain control technologies can save on raw materials (I.e., paint) 1n
addition to recovered solvents. A common oversight in BACT analyses is the
omission of recovery credits where the pollutant itself has some product or
process value. Examples of control techniques which may produce recovery
credits are equipment leak detection and repair programs, carbon absorption
systems, baghouse and electrostatic precipitators for recovery of reusable or
saleable solids and many inherently lower polluting processes.
Table B-2 presents an example of total annual costs for the control
system previously discussed. Direct annual costs are estimated based on
system design power requirements, energy balances, labor requirements, etc.,
and raw materials and fuel costs. Raw materials and other consumable costs
should be carefully reviewed. The applicant generally should have documented
delivered costs for most consumables or will be able to provide documented
estimates. The direct costs should be checked to be sure they are based on
the same number of hours as the emission estimates and the proposed operating
schedule.
B-7
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DRAFT
TABLE B-2. EXAMPLE OF A ANNUAL COST ESTIMATE FOR AN ELECTROSTATIC
PRECIPITATOR APPLIED TO A COAL-FIRED BOILER
Annual costs
(S/yr)
Direct Costs
Direct labor at $12.02/man-hour 26,300
Supervision at $15.63/man-hour 0
Maintenance labor at $14.63/man-hour 16,000
Replacement parts 5,200
Electricity at $0.0258/kWh 3,700
Water at $0.18/1000 gal 300
Waste disposal at SIS/ton (dry basis) 33,000
Total direct costs 84,500
Indirect Costs
Overhead
Payroll (30% of direct labor) 7,900
Plant (26% of all labor and replacement parts) 12,400
Total overhead costs 20,300
Capital charges
G&A taxes and insurance 45,300
(4% of total turnkey costs)
Capital recovery factor 133,100
(11.75* of total turnkey costs)
Interest on working capital 2,100
(10% of working capital)
Total capital charges 180,500
TOTAL ANNUALIZED COSTS 285,300
B-8
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Harch IS. 1990
Maintenance costs 1n some cases are estimated as a percentage of the
total capital Investment. Maintenance costs Include actual costs to repair
equipment and also other costs potentially Incurred due to any Increased
system downtime which occurs as a result of pollution control system
maintenance.
Fixed annual costs Include plant overhead, taxes, Insurance, and capital
recovery charges. In the example shown, total plant overhead Is calculated as
the sum of 30 percent of direct labor plus 26 percent of all labor and
maintenance materials. The OAQPS Control Cost Manual combines payroll and
plant overhead into a single Indirect cost. Consequently, for "study"
estimates, it 1s sufficiently accurate to combine payroll and plant overhead
Into a single indirect cost. Total overhead is then calculated as 60 percent
of the sum of all labor (operating, supervisory, and maintenance) plus
maintenance materials.
Property taxes are a percentage of the fixed capital investment. Note
that some jurisdictions exempt pollution control systems from property taxes.
Ad valorem tax data are available from local governments. Annual insurance
charges can be calculated by multiplying the insurance rate for the facility
by the total capital costs. The typical values used to calculate taxes and
insurance is four percent of the total capital investment if specific facility
data are not readily available.
The annual costs previously discussed do not account for recovery of the
capital cost Incurred. The capital cost shown 1n Table B-2 1s annualIzed
using a capital recovery factor of 11.75 percent. When the capital recovery
factor Is nultlpHed by the total capital Investment the resulting product
represents the uniform end of year payment necessary to repay the Investment
1n "n" years with an Interest rate "1".
B-9
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-DRAFT-
March 15. 1990
The formula for the capital recovery factor is:
CRF - 1 (1 +
(1 + 1)M
where:
CPF - capital recovery factor
n - economic life of equipment
1 • real interest rate
The economic life of a control system typically varies between 10 to 20
years and longer and should be determined consistent with data from EPA cost
support documents and the IRS Class Life Asset Depreciation Range System.
From the example shown in Table B-2 the Interest rate 1s 10 percent and
the equipment life Is 20 years. The resulting capital recovery factor 1s
11.75 percent. Also shown is interest on working capital, calculated as the
product of interest rate and the working capital.
It is important to insure that the labor and materials costs of parts of
the control system (such as catalyst beds, etc.) that must be replaced before
the end of the useful life are subtracted from the total capital Investment
before it is multiplied by the capital recovery factor. Costs of these parts
should be accounted for in the maintenance costs. To include the cost of
those parts in the capital charges would be double counting. The Interest
rate used Is a real Interest rate (I.e., 1t does not consider Inflation). The
value used In most control costs analyses 1s 10 percent In keeping with
current EPA guidelines and Office of Management and Budget recommendations for
regulatory analyses.
It is also recommended that Income tax considerations be excluded froa
cost analyses. This simplifies the analysis. Income taxes generally
B-10
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-DRAFT-
Narch IS. 1990
represent transfer payments from one segment of society to another and as such
are not properly part of economic costs.
III. OTHER COST ITEMS.
Lost production costs are not included in the cost estimate for a new or
modified source. Other economic parameters (equipment life, cost of capital,
etc.) should be consistent with estimates for other parts of the project.
B-ll
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