United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA453/R-92-017
December 1992
Air
A EPA Alternative Control
Technology Document for
Bakery Oven Emissions
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EPA-453/R-92-017
Alternative Control
Technology Document
for
Bakery Oven Emissions
Emission Standards Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
December 1992
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ALTERNATIVE CONTROL TECHNOLOGY DOCUMENTS
This report is issued by the Emission Standards Division, Office
of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, to provide information to State and local air
pollution control agencies. Mention of trade names or commercial
products is not intended to constitute endorsement or
recommendation for use. Copies of this report are available - as
supplies permit - from the Library Services Office (MD-35), U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, or for a nominal fee, from the National Technical
Information Service, 5285 Port Royal Road, Springfield, Virginia
22161.
11
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TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1-1
1.1 Objectives 1-2
1.2 Overview of the Bakery Industry 1-2
1.3 Contents of this Document 1-4
1.4 References 1-6
2.0 INDUSTRY DESCRIPTION, PROCESSES, AND EMISSIONS 2-1
2.1 Industry Description 2-1
2.2 Unit Operations 2-2
2.2.1 Dough Processes 2-2
2.2.2 Equipment 2-8
2.2.3 Operating Parameters 2-14
2.3 Air Emissions 2-15
2.3.1 Emission Sources 2-16
2.3.2 Emission Stream Characteristics 2-16
2.4 Summary of Current Air Emission Regulations .... 2-21
2.4.1 BAAQMD 2-21
2.4.2 SCAQMD 2-21
2.4.3 New Jersey 2-22
2.4.4 Other Areas 2-22
2.4.5 Prevention of Significant Deterioration . . . 2-22
2.4.6 New Source Review 2-23
2.4.7 Monitoring and Enforceability 2-23
2.5 References 2-25
3.0 VOC EMISSION CONTROL DEVICES 3-1
3.1 Combustion Control Devices 3-1
3.1.1 Direct Flame Thermal Oxidation 3-1
3.1.2 Regenerative Oxidation 3-2
3.1.3 Catalytic Oxidation 3-4
3.2 Noncombustion Control Devices 3-6
3.2.1 Carbon Adsorption 3-6
3.2.2 Scrubbing 3-7
3.2.3 Condensation 3-3
3.2.4 Biofiltration 3-9
3.2.5 Process and Formulation Changes 3-10
3.3 References 3-12
4.0 IMPACT ANALYSIS OF ALTERNATIVE CONTROL TECHNIQUES . . . 4-1
4.1 Model Ovens and VOC Emissions 4-1
4.1.1 VOC Emission Factors 4-3
4.1.2 Oven Type and Number of Stacks 4-3
4.1.3 Oven Heat Input 4-4
111
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TABLE OF CONTENTS
Section Page
4.1.4 Oven Operating Time 4-4
4.1.5 Control Devices 4-5
4.1.6 Flow Rates 4-5
4.1.7 Bread Production 4-5
4.1.8 Destruction Efficiency 4-5
4.2 Costing Methodology General Assumptions 4-6
4.3 Cost Analysis 4-6
4.4 Cost Effectiveness 4-6
4.5 References 4-14
IV
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LIST OF TABLES
Number Fteqe
2-1 Representative White Pan Bread Formula 2-3
4-1 Model Ovens 4-2
4-2a Cost of Catalytic Oxidation 4-7
4-2b Cost of Regenerative Oxidation 4-3
4-3a Cost Effectiveness of Catalytic Oxidation at
Bakery Ovens 4-9
4-3b Cost Effectiveness of Regenerative Oxidation
at Bakery Ovens 4-10
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LIST OF FIGURES
Number Page
2-1 Tunnel Oven 2-10
2-2 Single-Lap Oven 2-12
2-3 Spiral Oven 2-13
3-1 Regenerative Oxidation 3-3
3-2 Catalytic Oxidation 3-5
4-1 Cost Effectiveness of Catalytic Oxidation on
Bakery Ovens 4-11
4-2 Cost Effectiveness of Regenerative Oxidation
on Bakery Ovens . . -. 4-12
VI
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APPENDICES
Appendix
A Tables Referenced in Section 2.1 Industry
Description A-l
A-l Number of Bakeries by Product Category
and Number of Employees A-3
A-2 Top 100 Regional Contribution To Sales .... A-5
A-3 Plants by Bakery Type , Region, and State . . A-ll
B Bakery Oven Test Results ' 3-1
C Example Calculations of Cost Analysis C-l
OAQPS Control Cost Analysis for Catalytic
Incinerators c-2
OAQPS Control Cost Analysis for Regenerative
Incinerators C-7
D BAAQMD Regulation 8 Rule 42 D-l
E SCAQMD Rule 1153 E-l
Vll
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1.0 INTRODUCTION
The Clean Air Act Amendments (CAAA) of 1990 established new
requirements for State implementation plans (SIP) for many areas
that have not attained the national ambient air quality standards
(NAAQS) for ozone. These requirements include an expansion of
the applicability of reasonably available control technology
*
(RACT) to sources of volatile organic compounds (VOC) smaller
than those previously covered by the U.S. Environmental
Protection Agency (EPA). They also require that certain
nonattainment areas reduce VOC emissions below the existing RACT
requirements to ensure continual progress toward attainment of
the ozone NAAQS. In addition, certain areas require a
demonstration through atmospheric dispersion modeling that VOC
emission reductions will produce ozone concentrations consistent
with the ozone NAAQS.
To help the States identify the kinds of VOC control that
could be used to help meet these and other requirements, the 1990
Amendments also require EPA to publish alternative control
technology (ACT) documents for a variety of VOC sources. This
-document was produced in response to a request by the baking
industry for Federal guidance to assist in providing a more
uniform information base for State decision-making. The
information in this document pertains to bakeries that produce
bread, rolls, buns, and similar products, but not those that
produce crackers, pretzels, sweet goods, or baked foodstuffs thai:
are nor yeast-leavened. In mis document:, bread refers to yeast-
leavened pan bread, rolls, buns, or similar yeast-leavened
products unless otherwise noted.
1-1
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1.1 OBJECTIVES
One objective of this document is to provide information on
the baking process, potential emissions from baking, and
potential emission control options for use by State and local air
pollution control agencies in their analysis of new and existing
bakeries. This can be accomplished by identifying the cost
effectiveness of controls for each even in their area and
comparing to other facilities or industries to judge where money
might be spent*most wisely to lower emissions in the air shed.
Another important objective of this document is to provide a
predictive equation similar to an existing industry-derived
equation (described in Section 1.2), but for total VOC, using
recently gathered emission test data.
1.2 OVERVIEW OF THE BAKERY INDUSTRY
About 600 large commercial bakeries produce breadstuffs in
the United States.' Because bread is perishable and delays in
distribution to retail outlets are undesirable, bakeries are
usually located in or near population centers. Because
population correlates with vehicular travel and other VOC
emission sources, bakeries are frequently located in ozone
nonattainment areas.
About 23 bakery ovens in the United States currently have
emission control devices installed.' Some of these are located in
States or districts that have rules specific to bakeries (such as
California's Bay Area and South Coast). The other controlled
bakery ovens are located in ozone nonattainment areas where RACT
is required for na^or stationary sources, in ozone attainment
areas subject to prevention of significant deterioration (PSD)
review, or at bakeries electing to control VOC emissions for
other reasons.
The primary VOC emitted from bakery operation is ethanol.
In yeast-leavened breads, yeast metabolizes sugars in an
1-2
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anaerobic fermentation, producing carbon dioxide that is largely
responsible for causing the bread to rise. Besides the carbon
dioxide, equimolar amounts of ethanol and small amounts of other
alcohols, esters, and aldehydes are produced.
The primary emission source at a bakery is the oven.
Because the ethanol produced by yeast metabolism is generally
liquid at temperatures below 77°C (170°F) , it is not emitted in
appreciable amounts until the dough is exposed to high
temperatures in the oven. Although high concentrations of VOC
exist in the proof boxes that are often used to raise the panned
dough, the low airflow through those boxes minimizes emissions.
The regulation of VOC emissions from bakery ovens is a
recent development. Three major studies, detailed in Section
2.3.2, have been conducted to establish an emission factor for
quantifying VOC emissions from bakeries.
The first, Commercial Bakeries as a Major Source of Reactive
Volatile Organic Gases, was conducted in 1977 under an EPA
contract.' Ethanol emissions were calculated as 1.0 Ib/ton of
bread for straight dough and 11.2 Ib/ton of bread for sponge
dough.
The second study was performed by the Bay Area Air Quality
Management District (BAAQMD) in San Francisco.4 After early
tests showed that ethanol was the primary VOC emitted, a total of
16 ovens were tested using aqueous impingers and gas
chromatography/flame ionization. Ethanol emissions were
calculated to range from 0.6 to 14.0 Ib/ton of bread.1
The third study was performed by the American Institute of
Baking (AIE),' This study was intended to explain the wide range
of emission factors resulting front the BAAQMD study and to
provide a mathematical model for predicting ethanol emissions
from bakeries. Statistical analysis suggested that the factors
correlating best with ethanol emissions were yeast concentration
and total fermentation time, and that the relationship was
described as:
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EtOH = 0.40425 + 0.444585 (Yt)
where
EtOH = pounds ethanol per ton of baked bread
Y = baker's percent yeast
t = total time of fermentc.tion
This formula includes a little known correction for the addition
of spiking yeast where:
Yt = (Yj x tj) + (S x t,)
and
Yj = baker's percent yeast in sponge
tj = total time of fermentation in hours
S = baker's percent yeast added to dough
t, = proof time + floor tine
The "percent yeast in sponge" and "percent yeast added to dough"
are in tarms of baker's percent of yeast to the nearest tenth of
a percent. The "total time of fermentation" and "proof time +
floor time" are the fermentation times in hours to the nearest
tenth of an hour.
1.3 CONTENTS OF THIS DOCUMENT
Typical bakery processes, equipment, operating parameters,
emission sources, emission stream characteristics, emission
estimates, techniques for determining emissions and regulations
currently affecting VOC emissions from bakeries are described in
Chapter 2.0. Chapter 3.0 presents emission control techniques
that ara generally used, emission control techniques that inay oe
affective but are not in general use, and emission control
techniques that involve transfer of technology from other
industries. Chapter 4.0 presents capital and annualized costs of
controlling emissions for the control techniques identified as
feasible in Chapter 3.0, guidance on methods of estimating the
1-4
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costs of alternative control techniques, and environmental and
energy impacts.
1-5
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1.4 REFERENCES
1. 1991 Baking/Snack Directory & Buyer's Guide. Kansas City,
Missouri, Sosland Publishing Co.
2. Telecon. Sanford W., Research Triangle Institute (RTI),
with T. Otchy, CSM Environmental Systems, Inc. March 18,
1992. Oxidizers at bakeries.
3. Henderson, D.C. Commercial Bakeries as a Major Source of
Reactive Volatile Organic Gases. U. S. Environmental
Protection Agency. San Francisco. December 1977.
4. Cutino, J., and Owen, S. Technical Assessment Report for
Regulation 8, Rule 42 - Organic Compounds - Large Commercial
Bakeries. Bay Area Air Quality Management District. San
Francisco. July 1989.
5. Ref. 4.
6. Stitley, J.W., K.E. Kemp, B.C. Kyle, and K. Kulp, Bakery
Oven Ethanol Emissions - Experimental and Plant Survey
Results. American Institute of Baking. Manhattan, Kansas.
December 1987.
1-6
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2.0 INDUSTRY DESCRIPTION, PROCESSES, AND EMISSIONS
This chapter presents a description of the baking industry,
regulations currently affecting the industry, and information on
typical bakery unit operations including processes, equipment,
operating parameters, emission sources, and emission stream
characteristics.
2.1 INDUSTRY DESCRIPTION
The baking industry in the United States is large and
decentralized. In 1990 there were 2,636 commercial bakeries in
the United States.1 As shown in Table A-l, located in Appendix
A, 854 bakeries produced white pan bread, 980 produced buns and
soft rolls, 1,097 produced variety bread, and 713 produced hearth
bread and rolls.2 These four types of baked goods constitute the
bulk of the baked goods considered in this document. As shown in
Table A-23, of Appendix A, the -top 100 bakery companies operated
618 plants with sales ranging from $30 million to $2.6 billion in
1990.4 Aggregate sales from these 618 bakeries was $89.5
billion.5 Consumer expenditures for bakery food in 1990 ranged
between 9 and 11 percent of all dollars spent on food consumed at
home, with from $209 to $259 spent per year per household.* Per
capita bread consumption in 1990 was 49.93 Ibs, and was predicted
to increase 2.2 percent annually through 1996.7 Table A-3, in
Appendix A, presents the national distribution of bakeries by
type, region, and Stara." Because bread is perishable and
distribution delays are undesirable, the location of bakeries
tends to correlate with population and ara in larger cities in
all States.
2-1
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2.2 UNIT OPERATIONS
The following descriptions are aggregate and composite, and
not necessarily descriptive of a particular operation.
Production volumes, for example, fluctuate by daily orders,
holidays, and seasonal fluctuations.
2.2.1 Dough Processes
Bread production at large commercial bakeries is a highly
automated process. When operating at full capacity, a single
large bread bakery may produce up to 300,000 pounds of over 100
different varieties of bread and other bakery products per day.
All physical mixing and blending of ingredients, as well as the
working and dividing of the doughs, is performed mechanically.
Most dough batches are conveyed through each step of the process,
from the initial dividing through the final slicing and bagging,
with minimal handling.
Four basic dough processes are ased by commercial bread
bakeries: sponge and dough, straight dough, liquid ferments, and
no-time dough. The sponge and dough and liquid ferment methods
are used most often by large commercial bakeries. Straight
doughs are used for a few types of variety breads.
Bread in its simplest form requires four ingredients:
flour, water, yeast, and salt. Attributes such as loaf volume,
crumb softness, grain uniformity, si.Lkiness of texture, crust
color, flavor and aroma, softness retention, shelf life, and,
most important, nutritive value can all be improved by the
addition of appropriate optional ingredients. The materials that
are either required or may be optionally included in the
production of various standardized bread products are legally
defined by the Food and Drug Administration (21 CFR Part 136).9
A representative formula for wh:.te pan bread is shown in
Table 2-1.10 Two terms used throughout the document which are
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Table 2-1. Representative White Pan Bread Formula"
Ingredients
Essential
Flour
Water
Yeast
Salt
Optional
Yeast food
Sweeteners (solids)
Shortening
Dairy blend
Protease enzyme
Emulsifier
Dough strengthener
Preservative
Sponge %*
65.00
37.00
2.75
r
0.50
-
0.25
Dough (Remix) %*
35.00
27.00
2.1
7.25
2.3
2.0
0.50
0.50
0.20
Total % in
Formula
100.00
64.00
2.75
2.1
0.50
7.25
2.3
2.0
0.25
0.50
0.50
0.20
182.35
% equals baker's percent
Reference 10
2-3
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unique to the bakery industry are "baker's percent" and
"fermentation time". The baker's percent of an ingredient in a
bread formula refers to the weight of that ingredient per 100
Ibs. of flour in the formula.. For a given formula, the baker's
percent of all the ingredients will total to more than 100
percent as the flour alone equals ICO baker's percent. Table 2-1
presents a bread formula and the baker's percents (or weights) of
each ingredient. The total weight of flour in the formula is 100
Ibs., the total weight or baker's percent of yeast is 2.75. The
baker's percents of all the ingredients in this formula totals to
182.35 baker's percent. Fermentation time refers to the period
of time the yeast is fermenting. The clock for fermentation time
starts when the yeast comes in contact with water (whether it is
in a brew or dough) which can supply it with nutrients needed for
reproduction. The clock stops-when the bread enters the oven.
As about 50 percent of white pan bread produced in the
United States is made by the sponge and dough process, the
formula in Table 2-1 is shown in its adaptation to that
procedure. In the straight dough mebhod, a somewhat higher yeast
level (about 3.0 percent or more) is generally used, and all of
the listed ingredients are processed as a single batch. It
should also be kept in mind that individual bakers introduce
minor quantitative variations in their formulations and that the
values shown represent weighted averages.
In the sponge and dough method, the major fermentative
action takes place in a preferment, called the sponge, in which
normally from 50 to 70 percent of th«2 total dough flour is
subjected to the physical, chemical, and biological actions of
fermenting /east. The sponge is subsequently combined. wi~h the
rest of the dough ingredients to receive its final physical
development during the dough mixing or remix stage,11
The mixed sponge is discharged :.nto a greased trough and set
to ferment in a special fermentation room. The sponge
fermentation time normally lasts 4.5 hours, but may vary from 3.5
2-4
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hours for sponges incorporating 75 percent of the total flour to
5 hours for sponges with only 50 percent of the total flour.
Increased yeast levels bring about a noticeable reduction in
fermentation time.12
The fully fermented sponge is returned to the mixer and
mixed into the final dough, which receives additional
fermentation for a short floor time (no more than 45 minutes
under average conditions) .t3
The straight dough method is a single-step process in which
all the dough ingredients are mixed into a single batch. The
quality of the flour, the temperature of the mixed dough and the
amount of yeast used will determine the fermentation time.14 The
dough is fermented for periods of 2 to 4 hours, with the actual
practice time being generally close to 3 hours.15 Once
fermentation begins, the completion schedule is inflexible.16
About 70 years ago, efforts to simplify the sponge and dough
method of breadmaking resulted in a stable ferment process that
replaced the sponge with a liquid, flour-free ferment.17 The
basic stable ferment was made of up to 70 percent water, and
small amounts of yeast, yeast food, malt, sugar, nonfat dry milk,
and salt.18 The resultant suspension was fermented at a constant
temperature for 6 hours under gentle agitation. The mature
ferment was then either used immediately in whole or in part for
doughmaking, or it could be stored for about 48 hours, in a
stable condition, by cooling.19
Since the 1950's, the stable ferment process has been
subjected to a number of modifications and the resultant ferments
are variously referred -o as liquid sponges, liquid fermenca,
preferments, brews or broths, and continuous mix.20
Although many variations on the original list of ingredients
exist, flour-free ferments are currently often made up of 82
percent water, and small amounts of sweeteners, yeast, salt, and
buffer salts to control the pH.21 These ferments undergo
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fermentation for 1 to 1.5 hours while being mildly agitated; the
mature ferment is used or cooled.22
In general, the time required l:or the proper fermentation of
liquid ferments depends primarily on the level of flour in the
ferment. Flour-free ferments, given an appropriate set
temperature, require about 1 hour ol: fermentation, whereas
ferments containing 40 percent flour need 2 to 2.5 hours to reach
the end point.23
Attempts to reduce the time required before the final proof
have taken two directions: (1) mechanical dough development
obtained by intensive high-speed mixing of dough for a short
time, and (2) chemical dough development in which the dough is
treated with appropriate reducing agents and oxidants and mixed
at conventional speeds. Both approc.ches, in effect, eliminate
the bulk fermentation stage that represents about 60 per cent of
the total time in the traditional breadmaking process.24 These
doughs are often called no-time doughs.
The elimination of bulk fermentation time by mechanical
dough development usually means that these doughs require an
increase in the yeast level of 0.5 to 1.0 percent and a decrease
of 1.0 to 2.0 percent in the amount of added sweeteners. The
production time from the start of mixing to the end of baking may
be reduced to less than 2 hours.25
Chemically developed doughs are generally referred to as
short-time doughs if they are subjected to bulk fermentation for
periods of 0.5 to 1 hour, and no-time doughs if they are taken
directly from the mixer to the divider with no more than 15
minutes of floor time.26 These doughs require an increase in the
yeast lave! of 0.5 to 1.0 per cant and a decrease of 1.0 per cent
in the amount of added sweeteners. After an average fermentation
time of 30 minutes, the yeast slurry may be cooled or mixed as a
straight dough.27 The production time from the start of mixing to
the end of baking may be reduced to less than 3 hours.28
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Following fermentation, the dough produced by any of the
above processes is divided, rounded and made up into pieces of
proper weight for intermediate proofing, moulding, final proofing
and baking. Dividing and rounding operations subject the dough
to considerable physical abuse.29 The rounded dough balls are
given a brief rest period in an intermediate or overhead proofer.
Proofers are cabinet areas off the floor of the bakery which are
protected from drafts. The actual proof time in practice can
last anywhere from 30 seconds to 20 minutes, although it will
usually fall within a range of 4 to 12 minutes.30 On leaving the
intermediate proofer, the dough pieces enter a moulder in which
they are shaped and moulded into a cylindrical loaf form and then
deposited in the baking pan.31
After the dough is deposited in the baking pan, it is ready
for final proofing in a proof box. Proof times in practice
generally fall within a range of 55 to 65 minutes. For the most
part, panned dough is proofed to volume or height rather than for
a fixed time.32
After final proofing, the dough is baked in an oven. Modern
ovens are generally designed to convey the baking loaf through a
series of zones in which it is exposed for definite time periods
to different temperature and humidity conditions. The first
stage of baking, at a temperature of about 240°C (400° F) lasts
about 6.5 minutes. The second and third stages of baking
together last some 13 minutes at a constant temperature of about
238° C (460° F) . The final zone is maintained at a constant
temperature of 221 to 238° C (430 to 460° F) and the loaf baked
for about 6.5 minutes.33
While these temperatures and durations of the individual
baking phases are representative of conventional baking practice,
considerable deviations are encountered. Factors such as oven
design, weight or volume of product, crust character and color,
level of residual crumb moisture and others all have a bearing on
2-7
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actual baking temperature and time. Product size in particular
is an important determinant of baking time.34
These are only the basic processes. Each bakery employs
variations of these basic processes to suit its production
equipment, which is further varied for each individual type of
product.
2.2.2 Equipment
2.2.2.1 Mixers. Various mixing devices are used to combine
the dough ingredients. These devices vent inside the bakery and
are sources of minimal volatile organic compound (VOC)
emissions.35
2.2.2.2 Fermentation Vessels. These are typically vats in
brew processes and tubs in sponge processes. The yeast
reproduces here if under aerobic conditions; it generates carbon
dioxide gas, liquid ethanol, and other products if under
anaerobic conditions. The rooms housing these vats are humid and
warm, and are designed to have minimal air changes.
2.2.2.3 Intermediate Proofers. Intermediate proofers are
used to relax dough pieces for 3 to 12 minutes36 after dividing
and rounding and before they are moulded into loaves.
Intermediate proofers are generally operated under ambient
conditions. The intermediate proof time is usually between 4 and
12 minutes.37
2.2.2.4 Proof Boxes. Proof boxes are where some doughs are
allowed to proof (rise) after being panned. The proof box is a
relatively large chamber, fabricated of well insulated panels and
equipped with temperature and humidity controls. The three basic
control factors in final proofing are temperature, humidity, and
time. In practice, temperatures within the range of 32 to 54° C
2-8
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(90 to 130° F) and relative humidities of 60 to 90 percent are
encountered, with proofing temperatures of 41 to 43° C (105 to
110° F) being most prevalent for bread doughs.38 Under the
influence of the elevated temperature, the yeast activity in the
dough is accelerated and the loaves expand under the increasing
pressure of carbon dioxide produced by the yeast until its
thermal death in the oven.39 Care is taken to minimize exhausts
from these rooms, thereby minimizing the cost of heating and
humidifying them. Although significant VOC concentrations have
been measured in proof boxes, the small flow of air through them
indicates small VOC emissions.40
2.2.2.5 Ovens. Large bakeries typically operate from one to
four ovens of varying sizes, each one suited to produce certain
types of breads, buns, rolls, and other bakery products. All
known ovens burn natural gas, although some are equipped to burn
propane as a standby fuel. Approximately 85 to 90 percent are
directly fired41 by long ribbon burners across the width of the
oven. Indirectly fired ovens use gun burners and separate burner
and oven exhausts, allowing for the use of fuel such as
distillate oil. Indirectly fired ovens tend to be found in areas
where natural gas is not available, and often are adapted for
higher heat input after natural gas becomes available by jetting
(drilling) the fire tubes. This modified oven is sometimes
referred to as a semi-indirect-fired oven.
Generally, large commercial bakeries operate one very large
oven for baking high-volume products such as white and wheat
breads. Most bakeries also have one or more smallar ovens for
producing buns, rolls, and short-run specialty breads. There are
three basic configurations of large ovens:
Tunnel Oven: Doughs are conveyed along the length of the
oven from the front entrance to the
rear exit. Generally, the oven has two or
more exhaust stacks (see Figure 2-1).
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Rear
Exhaust
Comfort
Hood
Exhaust
Mid
Exhaust
Front
Exhaust
Comfort
Hood
Exhaust
Trays
Out
Figure 2-1. Tunnel oven.
2-10
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Lap Oven: Conveyor is "lapped" so that doughs are both
loaded and removed at the front of the oven,
after travelling the length of the oven and
back. Usually the oven has two or three
exhaust stacks (see Figure 2-2).
Spiral Oven: Conveyor path is spiraled so that doughs
circle the oven latitudinally several times.
The oven requires only a single exhaust stack
(see Figure 2-3).
Ovens are often equipped with a purge stack for exhausting
residual gases in the oven prior to burner ignition. The damper
for this stack is normally closed prior to baking. Emissions
from these purge stacks should be very minor, and for the
purposes of control devices and permitting, they will presumably
be treated in the same way as other minor emission sources.
Many ovens are also equipped with comfort hoods on either
end. These devices collect air emissions from the oven that
might otherwise vent to the bakery interior. Comfort hoods that
rely on fans rather than on convection to exhaust emissions have
a greater potential for emissions.
When an oven is first installed, it takes approximately 2
weeks to adjust it42 and balance the airflows before it is ready
for production. Turbulence in the exhaust airflow can cause
unstable or extinguished burner flames and non-uniform lateral
heat distribution throughout the zone. This may result in
uneven, improperly baked bread with poor texture, crumb
characteristics, and flavor, as well as other undesirable
characteristics.
Some bakeries have additional baking equipment for
producing such miscellaneous items as muffins, croutons, and
breadsticks. This equipment differs substantially from bread
ovens and was not within the scope of this document.
2.2.2.6 Cooling Boxes. After baking, bread is conveyed to
an area to cool. Cooling may take place either on a spiral
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Rear
Exhaust
Comfort
r~ Hood
Exhaust
Purge
Stack
Front
Exhaust
Trays In
Trays Out
Comfort
Hood
Exhaust
Figure 2-2. Single-hip oven.
2-12
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Exhaust
A
Bread Out -,
Trays Out
Trays In
u Dough In
Figure 2-3. Spiral oven.
2-13
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conveyor or on a multi-tier looped conveyor suspended from the
ceiling. Cooling conveyors may or nay not be enclosed.
2.2.2.7 Packaging. After cooling, the bread is packaged for
shipping. Some bread products are sliced before packaging.
These processes are highly mechanized.
2.2.3 Operating Parameters
The oven is separated into several temperature zones to
control the baking process. In the Initial zones of the oven,
the loaf rises to its final volume (oven spring) and the yeast is
killed, halting the fermentation reactions. In the middle zones,
excess moisture and ethanol are driven off. In the final zones,
the crust is browned and the sides QJ: the loaf become firm enough
for slicing. The baking process is complete when the temperature
at the center of the loaf reaches approximately 90 to 94°C (194
to 201°F) .43
The operator can adjust the oven temperature to compensate
for differences between batches and bread varieties based on
visual inspection and experience. The temperature in each zone
is controlled by adjusting the burner heat output with
temperature controllers and manually adjusting the exhaust
dampers. Constant temperature and laminar flow of exhaust gases
must be maintained across the width cf the oven.
The entire baking process is very sensitive to upset. By
law, white pan bread must weigh the amount stated on the package
without exceeding 38 percent moisture.44
All equipment must be extremely reliable to maintain high
bread quality while maintaining a tight, continuous production
schedule. For example, panned dough and bread are usually
transported from one process to another, such as from baking to
cooling, by mechanical conveyor belts. A conveyor shutdown may
cause the bread in the oven to remain too long in the oven and to
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overheat. If the loaves about to go into the oven are delayed,
they may rise above the size that will fit in the bread bags.
Each process unit depends on the smooth operation of the
preceding unit, and a breakdown in one process may affect dough
not scheduled for baking for several hours. For example, even a
minor malfunction of the bag twist-tie machine can result in the
loss of dough in the proof box. This dough cannot be baked and
stored or stored at temperatures low enough to retard proofing
because there are rarely provisions for storage at any
intermediate stage in processing. One cost of installing control
equipment on a bakery oven is the loss of production time while
rebalancing the heat flow in the oven after installation of the
control equipment.
As bread is produced for ^human consumption, bakeries are
required by health and safety regulations to maintain strict
sanitary conditions. In addition to daily cleaning, most
bakeries are shut down for cleaning and maintenance one or two
days per week.
2.3 AIR EMISSIONS
The major pollutants emitted from bread baking are VOC
emissions, chiefly the ethanol produced as a by-product of the
leavening process, which are precursors to the formation of
ambient ozone. Under aerobic conditions, yeast uses sugars added
to the dough or converts starches in the dough to sugars for
nutrients supporting the generation of new yeast cells. Oxygen
consumption during yaast reproduction produces an anaerobic
environment. Under anaerobic conditions, yeast ferments sugars,
creating carbon dioxide, ethanol, and other by-products by the
enzymatic conversion of sucrose to glucose to pyruvic acid to
acetaldehyde to ethanol. The yeast fermentation of 100 Ibs of
sugar (from either added sugar or sugar converted from starch by
the yeast) produces 49 Ibs ethanol, 47 Ibs carbon dioxide, and 4
Ibs of glycerol, organic acids, aldehydes, and various minor
2-15
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compounds.45 These compounds are responsible for the
characteristic flavors and aromas of bread. The ethanol formed
in the dough is vaporized and emitted from the oven during the
end of the baking process when the internal crumb temperature
reaches the boiling point of ethane 1. Emissions of criteria
pollutants arising from combustion (oxides of nitrogen, oxides of
sulfur, and carbon monoxide) are comparatively small from the
typically natural gas-fired ovens.
A few types of bread, such as corn bread and soda bread, are
chemically leavened with baking powder. An acid/base reaction
releases carbon dioxide, raising tha dough without ethanol
formation. However, since the traca organic flavoring agents are
also not formed, the resulting bread products taste different
from conventional breads.
2.3.1 Emission Sources
The primary source of VOC emissions at a bakery is the oven.
Screening measurements taken at mixers, fermentation vessels,
comfort hoods, proof boxes, oven exhausts, cooling area exhausts,
and packaging areas suggest that greater than 90 percent of VOC
emissions are from the oven.4*
2.3.2 Emission Stream Characteristics
Most studies of emissions from dough and bread have been to
investigate flavor constituents, rather than to evaluate air
pollution concerns.47-48 Several studi.es, however, have been
conducted co characterise bakery air emissions. They are
described below.
2.3.2.1 Commercial Bakeries as a Major Source of Reactive
Volatile Organic Gases. This study, performed under an EPA
contract in 1977, represents the first attempt at estimating
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ethanol emissions.49 Four loaves of bread were prepared,
fermented, and baked in a small electric oven under a tent to
capture emissions from each stage of the breadmaking process.
Emissions were measured at 0.5 Ibs ethanol per 1000 Ibs bread for
the straight dough process and 5.6 Ibs ethanol per 1000 Ibs bread
for the sponge dough process. Over 90 percent of the ethanol was
emitted during the baking. Several other emission factors,
ranging from 5 to 8 Ibs ethanol per 1000 Ibs bread, were also
calculated from various theoretical considerations for comparison
purposes.
The dough formulas used differed considerably from standard
industry recipes in both relative quantity and type of
ingredients used. Sweetener and yeast concentrations were both
relatively high, and a standard commercial baking grade of yeast
was not used to make the test loaves.
2.3.2.2 Bay Area Air Quality Management District (BAAQMD)
Study. This 1985-1986 study entailed source testing of bakery
ovens.50 In its attempt to develop more realistic emission
factors, the BAAQMD performed at least one source test using
BAAQMD Method ST-32 on every bread, bun, and roll oven at each of
the seven large commercial bakeries within the Bay Area. A total
of 16 ovens were tested, with some tested several times under
different operating conditions. Source emission factors,
expressed in pounds of ethanol per thousand pounds of bread, were
calculated for each test performed. The results obtained ranged
from 0.3 to 7.0 Ibs of ethanol per 1000 Ibs of bread baked. The
reasons for this variation of ethanol emissions were not
reported,
2.3.2.3 American Institute of Baking fAIB) Study. This 1987
study examined the ethanol emissions data collected by the
BAAQMD.51 The purpose of this study was to explain the wide
fluctuations in levels of ethanol measured during the BAAQMD
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survey and to look for correlations in the levels measured. The
AIB was requested to study the relationship between the test
results and process parameters that.may affect emissions. The
parameters studied included yeast and sweetener concentrations,
fermentation time, type of process i'sponge dough vs. straight
dough vs. brew), type of product (white bread, buns, sourdough
bread, variety), and baking conditions (time and temperature). A
linear relationship was found between emissions (Ibs ethanol per
1000 Ibs bread) and the product of the initial yeast
concentration and total fermentation and proof time. The dough
process type (sponge, straight, and liquid brew) also had a small
influence.
To confirm this relationship, AIB derived a mathematical
model based on the source test data. Using the formula developed
based on this model (see page 1-4), an ethanol emission factor
can be estimated for each variety of bread, and ethanol emissions
from an oven baking breads of the varieties for which the formula
is applicable can be quantified by multiplying the product mix by
the appropriate emission factors.
2.3.2.4 South Coast Air Quality Management District (SCAQMD)
Study. This 1988 survey was initiated by the SCAQMD's Rule
Development Office to quantify ethanol emissions and determine
the number, types, and characteristics of bakery ovens operating
in the District.52 The study was carried out using a
questionnaire designed by SCAQMD and distributed to bakery
operators by the newly formed Southern California Baker's Air
Quality Association. Information on bakery operations was
supplied by the major bakeries in the District. The quantity of
ethane! emissions reflected in answers to the questionnaire was
estimated by the bakery owners using the AIB formula. Results
from the questionnaire indicate that there were 24 major bakeries
operating 72 ovens in the District. Total bread production in
the District was 446,700 tons per year and total ethanol
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emissions there were calculated as 4.1 tons per day. Average
emission rates were calculated as 2.5 Ibs ethanol per 1000 Ibs
bread produced.
The SCAQMD's Emissions Inventory Unit also attempted to
quantify ethanol emissions generated by bread bakeries. Based on
their report, the total VOC emissions from bakeries in the South
Coast Air Basin was 2442 tons per year or 9.4 tons per day.
2.3.2.5 Current study. Because of increasing regulatory
concern for certain constituents emitted in small quantities
(such as acetaldehyde) from bakery oven exhausts and the need to
predict total VOC emissions (rather than just ethanol emissions)
from common baking parameters, emission data were gathered.
Sampling and analysis was performed using EPA Test Methods 18 (to
quantify total organic carbon) and 25A (to speciate the
constituents of the exhaust gas) at four typical bakeries on 18
different products with varying yeast concentrations and
fermentation times. Products sampled were selected to provide a
range of yeast concentrations and fermentation times similar to
the AIB study and representative of the baking industry. A
multiple step-wise linear regression was performed on the process
parameters and emission rates. The resulting data is summarized
in Appendix B, and indicates that total VOC from bakery ovens can
best be described as:
VOC E.F. = 0.95Y; + 0.195tj - 0.51S - 0.86t5 + 1.90
where
VOC E.F. = pounds VOC per ton of baked bread
Yj = initial baker's percent: of yeast to the nearest tenth
of a percent
t, = total yeast action time in hours to the nearest tenth
of an hour
S = final (spike) baker's percent of yeast to the nearest
tenth of a percent
2-19
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t, = spiking time in hours to the nearest tenth of an
hour
Although it appears that by changing a bread formula and
increasing the amount of final yeast (S), it would be possible to
obtain low or even a negative value for VOC emission estimates, a
product of high quality would not bo produced.53 Where no final
yeast is added, the formula condenseis to:
VOC E.F. = 0.95Yj + 0.195t; + 1.30
This predictive equation can be used for quantifying VOC
emissions from bakery ovens. A baker knows the yeast
concentrations and yeast action times for each variety baked.
Those values can be inserted into this equation and pounds of VOC
per ton of bread baked can be calculated. This number is
multiplied by the tons of bread baked during a given time period,
and the product is pounds of VOC emitted from the oven for that
particular product for the given tima period (typically per
year). The following equation demonstrates this calculation:
VOC Emissions tons/yr = VOC E.F. x BP x k
where
VOC E.F. = Ibs VOC emissions/ton of bread produced
BP = bread production in tons/yr
k = conversion constant (ton/2000lb)
2.3.2.6 Other Studies. Numerous; other studies of bread
emissions or constituents have been performed but are primarily
qualitative. These include Rothe,54 Wiseblatt and Kohn,55
Hironaka,56 El-Samahy,57 Makuljukow,58 Karkova,59 and others. These
works discuss the relative affects of baking parameters such as
proof temperature and baking time on ratios of aldehydes to
alcohols and other similar relationships. While of interest in
2-20
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efforts directed at narrowing the range of species for which to
analyze and minimize emissions through process modification,
these studies relate only slightly to the quantification and
control of total VOC emissions from bakery ovens.
2.4 SUMMARY OF CURRENT AIR EMISSION REGULATIONS
2.4.1 BAAQMD
BAAQMD in 1989 adopted Regulation 8 Rule 42 (Appendix D),
effective January 1, 1992, requiring 90 percent reduction of
ethanol emissions from large commercial bakeries. The regulation
exempts chemically leavened baked goods; miscellaneous baked
goods such as croutons, muffins, crackers, and breadsticks;
bakeries producing less than 100,000 Ibs per day of bread,
averaged monthly; and ovens emitting less than 150 Ibs per day of
ethanol. Ovens operating before January 1, 1988, are exempt if
they emit no more than 250 Ibs per day of ethanol. Emissions are
estimated using the AIB formula and measured using BAAQMD Method
ST-32.
~2.4.2 SCAOMD
SCAQMD in 1990 adopted Rule 1153 - Commercial Bakery Ovens
regulating VOC emissions from bakery ovens with a rated heat
input capacity of 2 million BTU per hour or more (Appendix E).
The rule requires 95 percent reduction of VOC emissions by
July 1, 1992, from new ovens emitting more than 50 Ibs per day of
VOC, 95 percent reduction of VOC emissions by July 1, 1994, from
ovens operating before January 1, 1991, that emit 100 or more Ibs
of VOC per day, and 70 percent reduction of VOC emissions by July
1, 1993, from ovens operating before January 1, 1991, that emit
between 50 and 100 Ibs VOC per day. Emissions are estimated
using the AIB formula and measured using EPA Test Method 25, or
SCAQMD Test Method 25.1.
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2.4.3 New Jersey
The State of New Jersey regulates VOC emissions from
bakeries according to the New Jersey Administrative Code Title 7
Chapter 27 Subchapter 16.6 "Source Operations other than Storage
Tanks, Transfers, Open Top Tanks, Surface Cleaners, Surface
Coaters and Graphic Arts Operations," This rule limits VOC
emissions to between 3.5 and 15 Ibs per hr. Emissions estimates
and measurement are by approved methods.
2.4.4 Other Areas
Several other State and local agencies regulate one or more
of the constituents of bakery oven emissions under a general
approach such as the regulation of hazardous air pollutants. In
the State of Washington, The Puget Sound Air Pollution Control
Agency limits ethanol emissions to levels that will not cause
ambient concentrations greater than 6000 ug/m3.60 Compliance
determination is by ambient modeling. The State of North
Carolina limits acetaldehyde emissions to levels that will not
cause ambient concentrations greater than 27 mg/m3.41 This type
of standard is not known to have bee.i used to require emission
reductions by a control device at a '.oakery.
2.4.5 Prevention of Significant Deterioration
Areas in attainment with National Ambient Air Quality
Standards (NAAQS) and subject to prevention of significant
deterioration (PSD) regulations typically evaluate significant
increases in emissions of VOC from a modification to an existing
bakery or a new bakery (to the extent: ihar either is considered a
major PSD source, i.e., 250 tons per year) by using either the
AIB formula or a source test generated at a similar facility.
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Under PSD, the level of significance is a 40 tons per year (tpy)
increase.
2.4.6 New Source Review
Areas in nonattainment with ozone NAAQS and subject to new
source review (NSR) regulations typically evaluate increased
emissions of VOC from a significant modification to an existing
bakery or a new bakery by using either the AIB formula or a
source test generated at a similar facility. Under NSR, the
level of significance is a 40 tpy increase in areas classified as
marginal or moderate. Modifications in areas classified as
serious, severe, or extreme are subject to more stringent levels
for determining a significant emissions increase. While not the
subject of this document, the EPA is developing guidance as to
how this review will be implemented. The major source cutoff for
new sources ranges from 100 tons per year in an area classified
as marginal ozone nonattainment to 10 tons per year in an area
classified as extreme ozone nonattainment. Several bakeries,
including an existing bakery in Atlanta, GA, and a new bakery in
Denver, PA, have been required to install VOC emission control
devices as a result of NSR regulations.
2.4.7 Monitoring and Enforceability
Careful record-keeping by any source of air emissions is
essential to the determination of compliance for that source.
This is particularly true of VOC sources since the ozone s-candard
related to VOC emissions is of short duration compared to other
criteria pollutants. Continuous emission monitoring (GEM) is one
method used to record emission rates. However, other
alternatives are available that may be less burdensome. These
include but are not limited to permit limits based on verifiable
quantities, temperature increase across catalysts, hot wire
2-23
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thermistors, and various flow-bas«»d alternatives to classical
CEM.
2-24
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2.5 REFERENCES
1. Gorman Publishing. Gorman Red Book, 1991. Chicago. February
1992. p. 18.
2. Ref. 1, pp. 24-29.
3. Ref. 1, pp. 24-29.
4. Ref. 1, pp. 24-29.
5. Ref. 1, pp. 24-29.
6. Food Survey Pinpoints Consumer's Bakery Buying Habits.
Bakery, p. 20. September, 1991. p. 20.
7. Anonymous. Per Capita Bread Consumption to Increase 2
Percent through '96. Milling and Baking News. January 15,
1991. p. 1.
8. Ref. 1, p. 30.
9. Pyler, E. J., Baking Science & Technology, Sosland
Publishing Company. Volume II, 1988. p. 590
10. Ref. 9, p. 591.
11. Ref. 9, p. 595.
12. Ref. 9, p. 596.
13. Ref. 9, p. 651.
14. Ref. 9, p. 653.
15. Ref. 9, p. 592.
16. Ref. 9, p. 593.
17. Ref. 9, p. 683.
18. Ref. 9, p, 684.
19. Ref. 9, p. 683.
20. Ref. 9, p. 684.
21. Ref. 9, p. 687.
22. Ref. 9, p. 686.
23. Ref. 9, p. 637.
2-25
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2.5 References (Continued)
24. Ref. 9, p. 699.
25. Ref. 9, p. 700.
26. Ref. 9, p. 703.
27. Ref. 9, p. 704.
28. Ref. 9, p. 706.
29. Ref. 9, pp. 709-718.
30. Ref. 9, pp. 718-719.
31. Ref. 9, pp. 719-723.
32. Ref. 9, p. 733.
33. Ref. 9, p. 741.
34. Ref. 9, p. 742.
35. Parrish, C. Radian Corporation. Site survey at Fox/Holsum
bakery. February 28, 1992.
36. Letter from Anne Giesecke, ABA to Martha Smith, EPA.
October, 20, 1992.
37. Ref. 36.
38. Ref. 9, p. 731.
39. Ref. 36.
40. Ref. 35.
41. Telecon. Sanford, W., RTI, with Lanham, W., Lanham Bakery
Solutions. May 5, 1992. Direct and indirect firing of bakery
ovens.
42. Ref. 36.
43. Ref. 36.
44. Ref. 36.
45. Sanderson, G. , G. Reed, B. Brui.isma, and E. J. Cooper. Yeast
Fermentation in Bread Baking. American Institute of Baking
Technical Bulletin. Manhattan, Xansas. V.12:4. December
1983.
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2.5 References (Continued)
46. Ref. 35.
47. Rothe, M. Aroma von Brot. Berlin, Akademie-Verlag. 1974. pp.
10-14.
48. Wiseblatt, L., F. E. Kohn. Some Volatile Aromatic Compounds
in Fresh Bread. Washington, D.C. Presented at 44th annual
meeting of the Quartermaster Food and Container Institute
for the Armed Forces. Washington, D.C. May 1959. pp. 55-66.
49. Henderson, D. Commercial Bakeries as a Major Source of
Reactive Volatile Organic Gases. U.S. Environmental
Protection Agency. San Francisco. December 1977. 18 pp.
50. Cutino, J., S. Owen. Technical Assessment Report for
Regulation 8, Rule 42-Organic Compounds - Large Commercial
Bakeries. Bay Area Air Quality Management District. San
Francisco. July 27, 1989., 34 pp.
51. Stitley, J. W., K. E. Kemp, B. G. Kyle, and K. Kulp. Bakery
Oven Ethanol Emissions - Experimental and Plant Survey
Results. American Institute of Baking. Manhattan, Kansas.
December 1987.
52. South Coast Air Quality Management District. Rule 1153 -
Commercial Bakery Ovens. El Monte. November 26, 1990.
53. Doerry, Wulf T., American Institute of Baking, to Giesecke,
A., American Bakers Association. October 8,1992. Proposed
predictive formula.
54. Ref. 47.
55. Ref. 48.
56. Hironaka, Y. Effects of Fermentation Conditions on Flavour
Substances in French Bread Produced by the Straight Dough
Method. Journal of Japanese Society of Food Science and
Technology (Yamaguchi, Japan). 1985.
57. El-Samahy, S. K. Aroma of Egyptian "Baladi" Brea'd. Getreide,
Mehl-und-Brot. Zagazig, Egypt. 1981.
58. Maklyukov, V. I. Influence of Various Baking Methods on the
Quality of Bread. Baecker-und-Konditor. Moscow. 1982.
59. Markova, J. Non-enzymic Browning Reaction in Cereal
Products. Sbornik-Vysoke-Skoly-Chemcko-Technologicke-V-
Praze. Prague. 1972.
2-27
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2.5 References (Continued)
60. Telecon. Sanford, W., RTI, with Fait, J., Puget Sound Air
Pollution Control Agency. February 7, 1992. Bakery
regulations.
61. North Carolina Administrative Code Title ISA Chapter 2
Subchapter 2D.1104.
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3.0 VOC EMISSION CONTROL DEVICES
Control technologies such as thermal oxidation, catalytic
oxidation, carbon adsorption, scrubbing, condensation,
biofiltration, and process changes were considered for reducing
VOC emissions from commercial bakery ovens. Devices under
development or not demonstrated were not considered, although
some show promise for the future.
This chapter describes emission control techniques
potentially applicable to VOC from bakeries and identifies the
control techniques to be evaluated in Chapter 4.0. These control
techniques are grouped into two broad categories: combustion
control devices and noncombustion control devices.
3.1 COMBUSTION CONTROL DEVICES
3.1.1 Direct Flame Thermal Oxidation
3.1.1.1 Control Description. Direct flame thermal
oxidation, also called thermal oxidation, is the process of
burning organic vapors in a separate combustion chamber. One
type of thermal oxidizer consists of a refractory-lined chamber
containing one or more discrete burners that premix the organic
vapor gas stream with the combustion air and any required
supplemental fuel. A second type of oxidizer uses a plate-type
burner firing natural gas to produce a flame zone through which
the organic vapor gas stream passes. Supplemental fuel,
generally natural gas, may be added to the bakery oven exhaust to
make the mixture combustible if the oven exhaust has a heating
value of less than 1.9 MJ/m3 (50 Btu/ft3),1 as is usually the case
in bakery ovens. Supplemental fuel consumption can be minimized
3-1
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by installing a heat exchanger to recover heat from the exhaust
gas to preheat the incoming gas.
Thermal oxidizer exhaust gas is mainly carbon dioxide and
water. Good design and operation limit unburned hydrocarbons and
carbon monoxide emissions to very low levels. These design
considerations include residence time, temperature, and
turbulence in the oxidizer chamber.
3.1.1.2 Effectiveness and Applicability of Thermal Oxidation
to Bakery Ovens. Oxidizers are most effective at controlling
exhaust streams with relatively high concentrations of organics.
When the oxidizer temperature is maintained at 870 °C (1600 °F)
and a residence time of 0.75 seconds;, over 98 percent of the
unhalogenated organic compounds in the waste stream can be
converted to carbon dioxide and watex.2"* Although VOC
concentrations in bakery exhaust car. fluctuate, a thermal
oxidizer can be designed to achieve reduction efficiency greater
than 98 percent.7
Although effective at VOC removal, the high cost of
supplemental fuel for thermal oxidizers usually makes some form
of heat recovery desirable in applications having gas exhaust
with heating values similar to baker/ ovens. Thermal oxidation^
is a technically feasible but relatively expensive technique for
the control of VOC emissions from ba.tery ovens and was not
evaluated in Chapter 4.
3.1.2 Regenerative Oxidation
3.1.2.1 Control Description. Regenerative thermal oxidation
is a variant of thermal oxidation (s«e Figure 3-1). The inlet
gas first passes through a hot ceram:.c bed thereby heating the
stream (and cooling the bed) to its ignition temperature. If the
desired temperature is not attainable;, a small amount of
auxiliary fuel is added in the combustion chamber. The hot gases
3-2
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then react (releasing energy) in the combustion chamber and while
passing through another ceramic bed, thereby heating it to the
combustion chamber outlet temperature. The process flows are
then switched, now feeding the inlet stream to the hot bed. This
cyclic process affords very high energy recovery (up to 95%).
Regenerative thermal oxidizers are available with either
single or multiple beds. When a single bed is employed, the bed
is used both as a combustion chamber and a regenerative heat-
recovery exchanger. Combustion of bhe air pollutant occurs in
the midsection of the single ceramic bed. When the multiple beds
are used, the combustion chamber is separate from the heat
transfer beds and is equipped with a burner to provide
supplemental heat when needed.
3.1.2.2 Effectiveness and Applicability of Regenerative
Oxidizers to Bakery Ovens. VOC reduction efficiencies greater
than 98 percent are achievable.8 Regenerative oxidizers are a
feasible control technique for control of VOC from bakery ovens,
and one is installed at a bakery in the United States. The cost
effectiveness of a regenerative oxic.izer is evaluated in Chapter
4.
3.1.3 Catalytic Oxidation
3.1.3.1 Control Description. A catalytic oxidizer is
similar to a thermal oxidizer except that combustion of the
exhaust gas takes place in the presence of a catalyst (see Figure
3-2). This allows the oxidizer to be operated at lower
temperatures, ranging from 320 to 653°C (600 to 1200 °F),9
consequently reducing NO, formation, supplemental fuel
consumption, and associated operating costs. Temperatures below
this range slow the oxidation reactions resulting in lower
destruction efficiencies. Temperatures above this range can
cause premature catalyst failure. Where catalytic oxidation cf
3-4
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-------
vapor streams with a high organic content can produce
temperatures above 650 °C (1200 °F) , catalytic oxidizers can be
suitable after dilution of those streams with fresh air.
Catalysts are typically composed of a porous inert substrate
plated with metal alloy containing platinum, palladium, copper,
chromium, or cobalt, and require an extremely clean exhaust
stream. In early bakery applications, there was some concern
that trace compounds and fine particulates may foul the catalyst,
reducing the efficiency. However, a catalytic oxidizer installed
in 1987 on a large bakery oven in the Bay Area has been running
trouble-free for five years.10 Although no test results are
available at this time, advances in catalyst technology may
eliminate the need for a preburner, thereby lowering costs. At
least one bakery is currently evaluating such a system.11
3.1.3.2 Effectiveness and Applicability of Catalytic
Oxidizers to Bakery Ovens. VOC reduction efficiencies greater
than 98 percent are achievable.12-13 Catalytic oxidation is
considered to be technically and economically feasible. Of the
23 known existing oxidizers on baker/ ovens, 21 are of a
catalytic design.14
3.2 NONCOMBUSTION CONTROL DEVICES
3.2.1 Carbon Adsorption.
3.2.1.1 Control Description. A carbon adsorption unit
consists of one or more beds of activated carbon, which adsorb
organic compounds from the exhaust stream. The organic vapors
adhere Co the large surface area and when the bed becomes
saturated, steam is passed through it to regenerate the carbon.
The steam/organic vapor mix is then condensed and either sent for
disposal or distilled to recover the organic compounds.
3-6
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3.2.1.2 Effectiveness and Applicability of Carbon Adsorption
to Bakery Ovens. Carbon adsorption is very effective in removing
low concentrations of VOC, with efficiencies greater than 95
percent. However, there are several problems with adapting this
technology to a bakery oven. Ethanol, the primary organic gas in
oven exhaust, has a high affinity for carbon and is difficult to
strip from the carbon beds. Incomplete stripping lowers bed
capacity and reduces abatement efficiency. Fats and oils in the
exhaust may clog the carbon pores, reducing capacity and bed
life. The resulting ethanol/water mixture would require further
treatment and disposal. Because of these problems, carbon
adsorption is not considered for reduction of VOC emissions from
bakery ovens.
3.2.2 Scrubbing
3.2.2.1 Control Description. Scrubbing is the absorption of
gaseous pollutants by liquid. In a packed tower scrubber, a fine
water mist is sprayed countercurrent to the exhaust flow in the
presence of packing material with a large surface area to
maximize liquid/gas mixing. Soluble organic compounds are
absorbed by the water and the water/organics mixture is either
treated for recovery of the organics or sent for disposal.
3.2.2.2 Effectiveness and Applicability of Scrubbing to
Bakery Ovens. Since ethanol is readily soluble in water,
scrubbers are technically feasible as a control device for VOC
removal in some applications. Substantial quantities of water
would be required to handle the exhaust: gas from bakery ovens
that would either present a massive wastewater disposal problem
or require the installation of large-scale wastewater treatment
that does not simply release the ethanol to the ambient air or
cause other cross-media emissions transfer, or ethanol recovery
equipment. Due to the high costs of wastewater treatment and
3-:
-------
ethanol recovery, scrubbing is not considered feasible as a
technique for VOC reduction from beikery ovens.
3.2.3 Condensation
3.2.3.1 Control Description. Condensation is the process by
which pollutants are removed by coding the gases below the dew
point of the contaminants, causing them to condense. Two types
of condensation devices are surface condensers and contact
condensers.
Surface condensers are generally of a shell-and-tube design
in which the coolant (usually water) and vapor phases are
separated by the tube wall and do not. contact each other.
Contact condensers cool vapors by spraying a relatively cold
liquid into the gas stream. They are generally more efficient,
inexpensive, and flexible than surf .ace condensers, but typically
produce large amounts of wastewater if the condensate cannot be
recycled, and therefore, are not considered appropriate for
bakeries.
3.2.3.2 Effectiveness and Applicability of Condensation to
Bakery Ovens. Condensing the VOC gcis stream emitted by baking
would require freon-chilled coils to cool a very wet gas stream
from 120 to 10 °C (250 to 50 °F) . Water would freeze on the
coils, insulating them, thereby reducing the abatement efficiency
of the system. Fats and oils would condense more readily,
exacerbating any potential sanitation problems in the ductwork.
However, the resulting condensed liquid would present a disposal
problem. Condensers are usually associated vith airflows less
than 2,000 ft3/min,15 and most older ovens are operated at
substantially higher airflows. Condensation is net considered a
technically feasible option for controlling VOC emissions from
bakeries because most ovens are operated at an airflow higher
than desirable for condensers, the cost of refrigeration is high,
3-8
-------
the value of the VOC recovered is low, and the potential for
wastewater disposal problem is high. Condensers have been not
been demonstrated to be effective VOC control devices on bakery
ovens.
3.2.4 Biofiltration
3.2.4.1 Control Description. Biofilters are a relatively
new, unproven technology, used in Europe for odor control and in
the United States on processes (such as yeast production) which
discharge gases at near ambient temperature.16 The exhaust stream
is passed through a bed of soil, which absorbs the organic
compounds. Microorganisms naturally present in the soil break
down the organics into carbon -dioxide and water. The beds must
be monitored and kept damp to prevent cracking or insult to the
microorganisms. This system appears to have several advantages
not offered by other control options. The capital costs are low
enough to permit the installation of separate beds for each stack
of a multi-stack oven. This avoids any flow-balance problems and
minimizes the expense of additional ducting. Annual operating
expenses are minimal, and include minor bed maintenance and
electricity for the exhaust fan only.
3.2.4.2 Effectiveness and Applicability of Biofiltration to
Bakery Ovens. Because the gas stream temperature from a bakery
oven is higher than the temperature which soil microorganisms can
tolerate, biofiltration has not been demonstrated to be a
feasible control tachnique for bakery ovens, 2ven if rhis
temperature problem were solved by cooling the gas stream (by
scrubbing, for example), the wastewater and fats condensation
problems associated with most cooling strategies are significant,
and sufficient space for these soil beds is unavailable at many
bakeries in the United States. The effectiveness of
biofiltration as a technique for VOC reduction from bakery ovens
3-9
-------
is not known. Therefore, biofiltration is not considered in
Chapter 4.
3.2.5 Process and Formulation Changes
3.2.5.1 Control Description. The AIB study demonstrated
that shorter fermentation and lower yeast percentages do reduce
the amount of ethanol emitted. Howaver, these changes also
affect the taste, texture, and quality of the finished product.
It is not known if comparable products can be produced using low-
ethanol formulations.
By substituting chemical leavening (baking powder) for the
yeast, bakers can produce bread without any ethanol formation or
emissions. Examples of such breads include corn bread and Irish
soda bread. However, by eliminating the fermentation reactions,
the chemical leavening process also prevents formation of the
various agents responsible for the flavors and aromas of
conventional yeast-leavened bread. Chemically leavened breads
have their own distinct flavor which may not be acceptable to
consumers as a substitute.
Much research has been done to find ways to enhance the
flavor of bread prepared with short fermentation time,17 but none
has been successful.18 A major yeast, manufacturer is currently
testing an additive intended to shorten fermentation time and
thereby lower VOC emissions,19 but ir.itial tests have not provided
consistently acceptable products.20
3.2.5.2 Effectiveness and Applicability of Process and
Formulation Changes to Bakery Ovens. Process and formulation
changes can be effective in reducing or nearly eliminating VOC
emissions from bakery ovens. However, no modified yeast,
additive, or enzyme that lowers VOC emissions has been
demonstrated to provide taste acceptable to the baking industry
and consumers in the United States. Although future prospects
3-10
-------
are promising, process and formulation changes are not currently
feasible as a means of substantially reducing bakery VOC
emissions.
-------
-------
3.3 REFERENCES
1. U. S. Environmental Protection Agency. Distillation
Operations in Synthetic Organic Chemical Manufacturing-
Background Information for Proposed Standards. Publication
No. EPA-450/3-83/005a. December 1983. p. 4-21.
2. Memorandum and attachments from Farmer, J. R., U. S.
Environmental Protection Agency, Office of Air Quality
Planning and Standards. August 22, 1980. Thermal
incinerators and flares.
3. Lee, K., J. L. Hansen, and D. C. McCauley, Union Carbide.
Revised Model for the Prediction of Time-Temperature
Requirements for Thermal Destruction of Dilute Organic
Vapors and Its Use for Predicting Compound Destructibility.
Presented at the 75th annual meeting of the Air Pollution
Control Association. New Orleans, LA. June 1982.
4. Midwest Research Institute. Emission Test of Acrylic Acid
and Ester Manufacturing Plant, Union Carbide, Taft,
Louisiana. Prepared for the U. S. Environmental Protection
Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. EMB Report 78-OCM8. September
1980.
5. Midwest Research Institute. Emission Test of Acrylic Acid
and Ester Manufacturing Plant, Rohm and Haas, Deer Park,
Texas. Prepared for the U. S. Environmental Protection
Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. EMB Report 78-OCM9. August 1980.
6. Midwest Research Institute. Stationary Source Testing of a
Maleic Anhydride Plant at the Denka Chemical Corporation,
Houston, TX. Prepared for the U. S. Environmental Protection
Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. EMB Report 78-OCM4. March 1978.
7. Cutino, J., S. Owen. Technical Assessment Report for
Regulation 8, Rule 42-Organic Compounds - Large Commercial
Bakeries. Bay Area Air Quality Management District. San
Francisco, July 27, 1339. p. 11.
8. Ref. 3, p. 11.
9. Ref. 1, p. 4-31.
10. Telecon. Sanford, W., RTI, with Gjersvik, C., Continental
Baking Company. July 14, 1992. Catalytic oxidizers.
11. Ref. 10
3-12
-------
3.3 References (Continued)
12. U. S. Environmental Protection Agency. Parametric Evaluation
of VOC/HAP Destruction via Catalytic Incineration. Project
Summary. Publication No. EPA/600/52-85/041. Research
Triangle Park, NC. July 1985. 4 p.
13. U. S. Environmental Protection Agency. Destruction of
Chlorinated Hydrocarbons by Catalytic Oxidation. Publication
No. EPA-600/2-86-079. Washington, DC. September 1986. p.
9.
14. Telecon. Sanford, W., RTI, with Otchy, T., CSM Environmental
Systems, Inc. March 18, 1992. Dxidizers at bakeries.
15. Purcell, R. Y., and G. S. Sharaef. Evaluation of Control
Technologies for Hazardous Air Pollutants. U. S.
Environmental Protection Agency. Research Triangle Park, NC.
Publication No. EPA/600/7-86/0D9a. February 1986. p. 3-3.
16. U. S. Environmental Protection Agency. Assessment of VOC
Emissions and Their Control from Baker's Yeast Manufacturing
Facilities. Research Triangle :?ark, NC. Publication No. EPA-
450-3-91-027. January 1992. p. 35-37.
17. Wiseblatt, L., and F. E. Kohn. Some Volatile Aromatic
Compounds in Fresh Bread. Washington, D.C. Presented at 44th
annual meeting of the Quartermaster Food and Container
Institute for the Armed Forces. Washington, D.C. May 1959.
18. Telecon. Sanford, W., RTI, with Lanham, W., Lanham Bakery
Solutions. May 5, 1992. Preferment additives.
19. Fleischmann's Yeast. Product Announcement. NPFC Significant
Factor in Reducing Ethanol Output. January 10, 1992.
20. Telecon. Sanford, W., RTI, with. Franek, J., Northeast Foods.
March 12, 1992. Emission tests using NPFC.
3-13
-------
4.0 IMPACT ANALYSIS OF ALTERNATIVE CONTROL TECHNIQUES
This chapter presents the cost effectiveness of various
control strategies based on a set of model baking lines. This
approach identifies a range of oven sizes and dough formulas
typical for the industry and derives VOC emissions and the
resulting costs of control for an oven. Of the control methods
described in Chapter 3.0, oxidation is the most feasible and
widely used, and the control devices selected for cost analysis
are catalytic and regenerative oxidizers. The cost analysis was
performed using the OAQPS Control Cost Manual, Fourth Edition.1
Example calculations are in Appendix C.
Because the parameters affecting bakery oven emissions vary,
a range of parameters such as yeast concentration, proofing time,
oven heat input, and air flow were used, and the resulting values
for cost per ton of VOC removed and oven heat input and air flow
are displayed as summary graphs.
4.1 MODEL OVENS AND VOC EMISSIONS
Due to the number of bakery ovens and wide variation in
process parameters affecting emissions, models were used to
represent typical baking lines. The models are not intended to
represent all bakeries, nor any specific bakery, but rather to
summarize the range of process parameters encountered at
commercial bakeries in current operation. Nine different size
ovens and three different dough formulas were used in the
modeling. This approach provides 27 different representative
model baking lines for analysis (see Table 4-1). The parameters
chosen are optimized in some respects and may not reflect the
mode of operation of some bakeries. For instance, many bakeries
do not operate 24 hours per day, their schedule being driven by
4-1
-------
TABLE 4-1. MODEL OVENS
Case
No.
1
2
3
4
5
6
7
8
9
10
It
12
13
14
15
16
17
18
19
20
21
22
23
24
23
26
27
Oven Size
10* BTU/hr
2
3
4
5
6
7
g
9
10
2
3
4
5
6
7
3
9
10
2
_ i
4
5
6
7
8
9
!0
Bread
Production
(tons/vr)
5,769
8,654
11,538
14,423
17,308
20,192
23.077
25,962
28,846
5,769
8.654
11.538
14,423
17,308
20,192
23,077
25.962
28,846
5,769
8,654
11,538
14,423
17,308
20,192
23.0T7
25.962
2S.846
Initial
Yeast
(Y)
125
125
125
125
125
125
2.25
125
125
4
4
4
4
4
4
4
4
4
425
425
425
425
425
425
425
425
425
Spike
Yeast
(S)
0
0
0
0
0
0
0
0
0
as
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0
0
0
0
0
0
0
0
0
Y Acuon
Time
7
5.i>7
5'i7
5.i 17
5.i >7
5.. 5
515
5.15
5.15
5.15
5.15
5.15
515
5 15
Spike
Time
(«»)
0
0
0
0
0
0
0
0
0
1.38
1.38
1.38
1.38
1.38
" 1.38
1.38
1.38
1.38
0
0
0
0
0
0
0
0
0
VCX; Emissions
Factor
(Ibi/ton)
4.4
4.4
4.4
44
4.4
4.4
4.4
44
4.4
5.4
5.4
5.4
5.4
5.4
54
5.4
5.4
5.4
69
69
6.9
6.9
6.9
6.9
6.9
69
69
VOC
Emissions
CtonsAr)
13
19
25
32
38
44
51
57
63
16
23
31
39
47
55
62
70
78
20
30
40
50
60
70
80
90
100
* Assumes 520 BTLYIb bread and 6000 hr/yr wtxiucuon
** Emissions calcinated from predictive formula
4-2
-------
orders, holidays, and seasonal variations. In the case of
bakeries operating less than 24 hours per day, the decrease in
hours means a decrease in emissions, but since the control device
need not be operated when the oven is not baking, fuel and other
operating costs are also reduced. Selection of the bakery
process parameters is discussed below.
4.1.1 VOC Emission Factors
In the absence of specific source tests, the emission of
VOC's from bakery ovens is best described by a formula relating
yeast concentration and total yeast action times (mixing,
proofing, floor, and fermentation times) to VOC emissions as
described in Chapter 2.0. According to this study and the AIB
study on bakery oven ethanol emissions,2 parameters such as dough
type (sponge, straight, brew), sugar concentration in the dough,
oven type, and bread type do not appreciably affect VOC
emissions. In this study four bakeries were tested. The
bakeries were chosen to test a wide variety of products
indicative of the range in the industry. In this model, values
for initial yeast (Yj) , total yeast action time (t,) , final yeast
(S) , and spiking time (t,) that are known to result in a
marketable product were chosen. These values reflect the range
of values found in the dough formulas that were tested in this
study and, therefore, represent a reasonable range of the
industry.
4,1.2 Oven Tvr;e and Number cf Stacks
Model ovens were assumed to be directly fired by natural gas
and have only one stack. Because indirectly fired ovens make up
a small portion of the known ovens, they are not considered.
Since the products of combustion would presumably not enter the
control device in indirectly fired ovens, the flow rate to the
4-3
-------
control device for indirectly fired ovens would be lower and the
control device may be smaller, lowering control costs. Oven
design (spiral, tunnel, tray) is not thought to affect emission
levels.3
Because adjustments to exhaust, stack dampers in a multi-
stack oven will change the air flow distribution and, therefore,
the distribution of emissions from individual stacks, the need to
treat the exhaust from one or more stacks must be examined on a
case-by-case basis.4 Such a site-specific engineering analysis
is beyond the scope of this document. The analysis in this
chapter assumes that each control technology would require an
exhaust system ducting sufficient stacks in multi-stack ovens
through a single plenum to a control device, in order to achieve
the required level of emission reduction. An estimate for the
increased capital cost of additional stacks is $40,000 per
stack.6
4.1.3 Oven Heat Input
Oven heat inputs from 2 to 10 JIBtu/hr were selected in
increments of 1 MBtu/hr. This is representative of the range of
heat inputs for commercial bakery ovens. This analysis assumes a
linear relationship between heat input, oven airflow, and bread
production, and uses heat input as the independent variable;
however, the physical quantity actually most affecting control
device cost is airflow.
4.1.4 Oven Operating Time
All ovens were assumed to operate 24 hours per day, five
days a week (6000 hours per year) and represents common practice
in the commercial baking industry.
4-4
-------
4.1.5 Control Devices
Of the approximately 23 ovens currently controlled, 21 use
catalytic oxidizers, one uses a thermal oxidizer, and one uses a
regenerative oxidizer.7 Cost effectiveness analyses were
generated for catalytic and regenerative oxidizers.
4.1.6 Flow Rates
Flow rates are estimated by the same mathematical model used
by the SCAQMD.8 Flow rates are calculated as a function of heat
input. Assuming 7.37 Ib air used in combusting 10,000 Btu of
natural gas, 110 percent theoretical air as supplied, 0.0808 Ib
air per cubic feet,9 and adding the resulting value to the 10
percent moisture10 potentially evaporated from the white bread
dough, flow rates can be calculated.11 The percent moisture loss
will vary for other products. The values so derived were doubled
to compensate for the increase in temperature and moisture.12
4.1.7 Bread Production
Bread production is assumed to be a linear function of heat
input. The common design value of 520 Btu per pound of bread is
used13 (see Table 4-1) .
4.1.8 Destruction Efficiency
A destruction efficiency of 93 per cent is assumed,
consistent with EPA policy.14 The EPA policy maintains that 98
percent destruction efficiency is reasonable for oxidation based
on the results of emission tests at incinerators in several
industries. Certain existing control devices may have been
designed for a lower control efficiency, such as 95 per cent.
State or local agencies considering control of bakery VOC
4-5
-------
emissions should consider allowing facilities to continue to use
these devices rather than requiring immediate replacement.
4.2 COSTING METHODOLOGY GENERAL ASSUMPTIONS
The following assumptions were made in estimating control
costs:
All costs are presented in 1991 dollars;
The factor method used is nominally accurate to within
±30 per cent;
The site is readily accessible by rail or road;
Control devices are dedicated to single ovens (one
oxidizer per oven);
Costs of combining multiple stacks are not included;
There is no salvage value for the used control equipment
at the end of its service li::e;
No site preparation or civil engineering cost other than
the amount allowed by the OAQPS Control Cost Manual is
included (site-specific costs; such as roof reinforcement
is not included); and
Utilities are available at the site.
4.3 COST ANALYSIS
Tables 4-2a and 4-2b summarize the parameters, total capital
investment, utility costs, and total annual cost used in the cost
analyses for catalytic and regenerative oxidization.
4.4 COST EFFECTIVENESS
Tables 4-3a and 4-3b summarize the cost-effectiveness of
catalytic and regenerative oxidation as control technologies for
bakeries. As reflected in the tables, the technologies become
more cost-effective as the size of ttie oven increases. The cost
of control decreases per ton of VOC removed and per pound of
bread produced as the oven size (and therefore, production
capacity) increases.
Figures 4-1 and 4-2 graphically summarize the relative cost-
effectiveness of catalytic and regenerative oxidation. The
4-6
-------
TABLE 4-2a. COST OF CATALYTIC OXIDATION'1
Case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Total Capital
Investment
($)
$84,000
$106,000
$124,000
$140,000
$155,000
$169,000
$182,000
$194,000
$206,000
$84,000
$106,000
$124,000
$140,000
$155,000
$169,000
$182,000
$194,000
$206,000
$84,000
$106,000
$124,000
5140,000
$155,000
$169,000
$182.000
5194,000
5205.000
Natural
(scfin)
1.5
2.3
3.0
3.8
4.6
5.3
6.1
6.8
7.6
1.2
1.8
2.3
2.9
3.5
4.1
4.7
5.3
5.9
0.7
0.9
1.2
1.5
1.9
2.2
7
-------
TABLE 4-2b. COST OF DEGENERATIVE OXIDATION*
Case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Total Capital
Investment
($)
$197,000
$218,000
$234,000
5248,000
$259,000
$270,000
$279,000
$287,000
$295,000
$197,000
$218,000
$234,000
$248,000
$259,000
$269,000
$279,000
$287,000
$295,000
$197,000
$218,000
$234,000
3248,000
$259,000
$269,000
$279,000
5237,000
$295,000
Natural Gas Usage
(scfin) ($/yr)
4.4
6.6
8.7
10.9
13.1
15.3
17.5
19.7
21.8
4.0
6.0
8.0
10.0
12.1
14.1
16.1
18.1
20.1
3.5
4.4
6.9
3.6
10.4
12.1
13.8
15.5
17.3
$5,200
$7,800
$10,400
$13,000
$15,600
$18,200
$20,700
$23,300
$25,900
$4,800
$7,200
$9,500
$10,300
$14,300
$16,700
$19,100
$21,500
$23,900
$4,100
$6,200
$8,200
$10,300
$12,300
$14,400
$16,400
318,500
520,500
Electricity Usage
(kWh/yr) ($/yr)
10,000
15,100
20,100
25,100
30,100
35,100
40,200
45,200
50,200
10,000
15,100
20,100
25,100
30,100
35,100
40,100
45,200
50,200
10,000
15,000
20,000
25,000
30,100
35,100
40,100
45,100
50,100
$600
$900
$1,200
$1,500
$1,800
$2,100
$2,400
$2,700
$3,000
$600
$900
$1,200
$1,500
$1,800
$2,100
$2,400
52,700
$3,000
$600
$900
51,200
$1,500
$1,800
$2,100
$2,400
$2,700
$3,000
Total
Annual Cost
($/yr)
$72,000
$74,000
$85,000
$91,000
. $96,000
$101,000
$106,000
$110,000
$115,000
$71,000
$78,000
$84,000
$90,000
$95,000
$99,000
$104,000
$108,000
$113,000
$71,000
$77,000
583,000
588,000
$93,000
597,000
5101,000
$105,000
$109,000
Costs in this table are m 1988 dollars. Total Capital Invesiment can be multiplied by 1.06 to reflect 1992
dollars. For updating Total Annual Costs, current utility rates should be verified with utility companies
and the appropriate correction applied. The additional cost for more than one stack has NOT been
used in this calculation. Although this cost would be base i on oven size and other site-specific
characteristics, an increase in capital cost of $40,000 per stick can be used. This would translate to an
annual cost of 540,000 multiplied by a capital recovery factor (CRF) of 0.1628 and would equal 56,512.00.
4-3
-------
TABLE 4-3a. COST EFFECTIVENESS OF CATALYTIC OXIDATION AT BAKERY OVENS
Case VOC Emissions
No. (tons/'yr)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
~*"j
<' *
13
19
25
32
38
44
51
57
63
15*
-23*
31
39
47
55
62
70
78
20
30
40
50
60
70
80
90
100 ,
VOC Reductions
(tons/year)
12
18
25
31
37
43
49
55
62
15
23
30
38
45
53
61
68
76
20
29
39
49
59
69
79
S8
98
Bread Production
(Ib/yr)
11,538,000
17,308,000
23,076,000
28,846,000
34,616,000
40384,000
46,154,000
51,924,000
57,692,000
1
11,538,000
17,308,000
23,076,000
28,846,000
34,616,000
40,384,000
46,154,000
51,924,000
57,692,000
1 1,538,000
17,308,000
23,076,000
28,846,000
34,616,000
40384,000
46,154,000
51.924000
57,692.000
Cost Effectiveness
($/ton VOC) (S/lb bread)
52,945
$2,274
$1,913
$1,684
S 1,524
$1,404
$1,311
$1,236
$1,173
$2,364
$1,819
51,526
$1,340
SU10
51,113
$1,037
$976
5925
51,797
51,372
51,145
51,001
5901
5825
S767
"20
S681
0.0031
0.0024
0.0020
0.0011
0.0016
0.0015
0.0014
0.0013
0.0013
0.003 1
0.0024
0.0020
0.0018
0.0016
0.0015
0.0014
0.0013
0.0012
0.003 1
0.0023
00019
0.0017
0.0015
0.0014
00013
j.oo i:
0.0012
Emissions calculated from predictive formula.
i-9
-------
TABLE 4-3b. COST EFFECTIVENESS OF REGENERATIVE OXIDATION AT BAKERY OVE
Case VOC Emissions
No. (tons/vr) *
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
1 rr_...
13
19
25
32
38
44
51
57
64
16
23
31
39
47
55
62
70
78
20
30
40
50
60
70
80
90
100
VOC Reductions
(tons/year)
12
18
25
31
37
43
49
55
62
15
23
30
38
45
53
61
68
76
20
29
39
49
59
69
79
88
98
Bread
(Prod. Ib/yr)
11,538,000
17,308,000
23,076,000
28,846,000
34,616,000
40,384,000
46,154,000
51,924,000
57,692,000
11,538,000
17,308,000
23,076,000
28,846,000
34,616,000
40,384,000
46,154,000
51,924,000
57,692,000
11,538,000
17,308,000
23,076,000
28,846,000
34.616,000
40,384,000
46,154,000
51,924,000
57,692.000
Cost Effectiveness
(S/ton VOC) fS/lb breads
$5,831
S4,186
$3,457
$2,949
$2,599
$2,342
$2,146
$1,990
$1,863
$4,707
$3,444
$2,780
$2,367
$2,083
$1,875
$1,715
$1,589
$1,486
$3.602
$2,527
52,113
SI, 794
31.J75
$1,414
$1,291
$1,193
31.114
0.0062
0.0045
0.0037
0.0031
0.0028
0.0025
0.0023
0.0021 .
0.0020
0.0062
0.0045
0.0037
0.0031
0.0027
0.0025
0.0023
0.0021
0.0020
0.0061
0.0045
0.0036
0.0031
0.002"
0.0024
0.0022
0.0020
0.0019
Emissions calculated from predictive formula
4-10
-------
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minimum, average, and maximum cost per ton of VOC removed is
labeled on each graph. These cost-effectiveness curves can be
used to evaluate the cost of VOC removal for an individual oven.
Because it is rare that an oven is dedicated exclusively to
the baking of one product, the VOC emissions for each product
typically baked in an individual oven must be estimated. These
individual product estimates are multiplied by their annual
production tonnage and then summed to reflect actual total
emissions from the oven. This sum should then be divided by the
sum of the individual annual production tonnages. This quotient
is in pounds of VOC emissions per ton of bread. For example:
(4.4 Ib/ton) (1000 tons/year) = 4400 Ib/yr
(5.4 Ib/ton) (2000 tons/year) ,= 10800 Ib/yr
(7.0 Ib/ton) (5000 tons/year) = 35000 Ib/vr
(8000 tons/year) 50200 Ib/yr = 25 tons/yr
(50200 Ib/yr)/(8000 tons/yr) =6.3 Ib/ton
4-13
-------
-------
4.5 REFERENCES
1. Vatavuk, W. M. OAQPS Control Cost Manual, Fourth Edition.
EPA 450/3-90-006. U. S. Environmental Protection Agency.
Research Triangle Park, 1990.
2. Stitley, J. W., K. E. Kemp, B. G. Kyle, and K. Kulp. Bakery
Oven Ethanol Emissions - Experimental and Plant Survey
Results. American Institute of Baking. Manhattan, Kansas.
December, 1987. p. 11.
3. Ref. 2, p. 11.
4. Fischer, H., APV Baker, to Giesecke, A., American Bakers
Association. April 22, 1991. Exhaust levels of a multi-stack
oven.
5. American Institute of Baking. Draft: Control of Ethanol
Emissions from Ovens. Manhattan, Kansas. August, 1988. p. 15.
6. Frederiksen Engineering. Study and Conceptual Cost Estimate-
Bakery Oven Ethanol Abatement. Oakland, California. October,
1990. p. 11.
7. Telecon. W. Sanford, Research Triangle Institute (RTI), with
T. Otchy, CSM Environmental Systems, Inc. March 18, 1992.
Oxidation.
8. South Coast Air Quality Management District. Rule 1153 -
Commercial Bakery Ovens. El Monte, California, November, 1990.
p. 32.
9. Perry, R. H. Perry's Chemical Engineer's Handbook. New York.
McGraw-Hill. 1984. pp. 9-38.
10. Pyler, E. J. , Baking Science & Technology, Sosland Publishing
Company. Volume II, 1988. P. 590.
11. Telecon. Sanford, W. , RTI, with Doerry, W. , American Institute
of Baking. August 19, 1992. Flow rates in brsaci baking ovens,
12. Ref. 8. .
13. Ref. 11, p.763.
14. Memorandum from Farmer, J.R., U.S. Environmental Protection
Agency, to NSPS contractors. August 22, 1980. Thermal
Incineration and Flares, p. 1.
4-14
-------
-------
APPENDIX A
TABLES REFERENCED IN SECTION 2.1 - INDUSTRY DESCRIPTION
A-l
-------
A-2
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A-10
-------
Table A-3. Plants By Bakery Type, Region and State'
Region
Wholesale
Grocery
Chain
Multi-Unit
Retail
Cookie &
Cracker/
Frozen Food
Total
NORTHEAST
Connecticut
Dist. of
Columbia
Maine
Massachusetts
New
Hampshire
New Jersey
New York
Pennsylvania
Rhode Island
Vermont
Total
26
6
17
54
7
80
169
123
12
5
455
0
1
0
2
0
0 -
1
1
0
0
5
5
2
0
12
1
8
19
16
0
0
63
7
0
1
17
1
30
29
36
1
2
724
38
9
18
85
9
118
218
176
13
7
691
MIDWEST
Illinois
Indiana
Iowa
Michigan
Minnesota
Missouri
Ohio
Wisconsin
Total
91
31
15
56
31
27
66
38
355
3
3
0
5
3
2
5
5
26
16
4
2
16
7
2
18
10
75
30
18
4
19
9
7
25
10
722
140
56
21
96
50
38
114
63
575
A-ll
-------
Table A-3 (continued)
Region
Wholesale
Grocery
Chain
Multi-Unit
Fletail
Cookie &
Cracker/
Frozen Food
Total
SOUTH ;
Alabama
Arkansas
Delaware
Florida
Georgia
Kentucky
Louisiana
Maryland
Mississippi
North Carolina
South Carolina
Tennessee
Virginia
West Virginia
Total
14
13
2
73
29
6
17
32
6
32
8
28
32
5
297
0
1
0
1
0
0
0
2
2 -
0
0
0
1
0
7
0
0
0
4
3
2
3
8
0
3
1
5
2
1
32
3
6
0
13
19
6
1
4
1
11
4
11
6
2
87
17
20
2
91
51
14
21
46
9
46
13
44
41
8
423 I
SOUTHWEST
Arizona
New Mexico
Oklahoma
Texas
Total
25
6
13
87
737
1
0
o
5
6
0
1
2
6
9
3
3
3
25
34
29
10
18 !
123
780
A-12
-------
Table A-3 (continued)
Region
Wholesale
Grocery
Chain
Multi-Unit
Retail
Cookie &
Cracker/
Frozen Food
Total
PLAINS
Colorado
Kansas
Montana
Nebraska
North Dakota
South Dakota
Utah
Total
21
14
2
10
6
4
17
74
1
2
0
0
0
0
2
5 .
1
0
0
1
1
3
3
5
6
4
1
2
2
1
6
22
29
20
3
13
9
8
28
110
\
WEST
Alaska
California
Hawaii
Idaho
Nevada
Oregon
Washington
Total
5
212
20
4
8
26
32
307
1
9
0
0
0
1
i
12
0
26
3
0
0
4
3
36
0
65
6
0
0
10
8
89
6
312
29
,i
4 i
8
41
44 j
444 \
Region
Puerto Rico
Canada
Total no. of
plants
-
Wholesale .
3
154
7,820
Grocery
Chain
0
2
63
Multi-Unit
Retaii
2
9
235
Cookie &
Cracker/
Frozen Food
6
34
518
Totai j
11 \
199
2,636
i
'Gorman P-joiisning. Gorman 3ed 3ook, 1991. Chicago. February 1992. pp. 24-29
A-13
-------
APPENDIX B
BAKERY OVEN TEST RESULTS
-------
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-------
APPENDIX C
EXAMPLE CALCULATIONS OF COST ANALYSIS
C-l
-------
OAQPS Control Cost Analysis for Catalytic Incinerators
Section 3.4.1 - Steps Common to Regenerative and Catalytic Units
Step 1. Establish Design Specifications
Enter the following data corresponding to the waste gas:
Volumetric Flow Rate, scfm (77 degrees F, 1 atm) 447.00 scfm
Temperature, preheater inlet, Twi 100.00 deg. F
(Assume balance oxygen composition)
Chemical Composition of Combustibles
enter names here > ethanol 1,939.00 ppmv
acataldghyda 19.39 ppmv
please use two most combustible
compounds. If less than two,
please enter 1's to avoid
division by zero errors
Heating Value of Combustibles
ethanol
acetaldehyde
Enter hours per year of operation
2,407.00 neg.del.h sub c, BTU/scf
2,149.00 neg.del.h sub c, BTU/scf
6,000.00 hours/year
Enter the following data specific to the incinerator:*
Desired Control Efficiency /best to assume > 0.90)
Combustion Chamber Outlet Temperature
Desired Percent Energy Recovery, decimal
(choose: 0, 0.35, 0.50, or 0.70)
0.98
700.00 deg. F
0.7
Step 2. Verify that the oxygen content of the waste gas exceeds 20%.
Air Content = 99.80 Vol. %
Oxygen Content = 20.86 percent
Step 3. Calculate the LEL and the Percent of the LEL of the gas mixture
Enter the LEL of tne following compounds:
ethanol 3.25 vol. %
acetaldehyde 3.97 vol. %
sum of x sub i, i equals 1 to n 1,958.39
Lower Explosive Limit of the mixture aquals: 34,997.41 ppmv
Percent LEL of *he mixture equals: 5.SO percent
if greater tnan 25%, ailution air should be added
to avoid fire insurance regulations
Step 4. Calculate the volumetric heat of combustion of the waste gas stream
Teat of r;omoustion.
acataiaenyae
Heat of combustion foe the mixture is
2.407.30 3TU/scf
2.149.CO BTU/scf
4.71 BTU/scf
32,500.00 ppmv
39,700.00 ppmv
Assuming waste gas is principally air (molecular
weight 23.97, denstjy 0.0739 Ib/scf). then
Heat of comousuon per pound of incoming gas is
63.72 BTU/lb
For catalytic applications the hsat of combustion must normally be less
than 10 BTU/scf (for VOC's in air).
C-2
-------
Section 3.4.3 - Steps Specific to Catalytic Units
Step 5o. Establish desired outlet temperature of the catalyst bed, Tfi
Enter catalyst bad outlet temp,
assume 300-900 deg. F for 90-95% destruction efficiency
maximum temp, of 1200 deg. F should not be exceeded
Step 6c. Calculate waste gas temperature at preheater exit
Define the following temperatures:
Two, VOC stream leaving heat exchanger
Twi, waste gas inlet temperature
Tfo, flue temperature after heat exchanger
Tfi, catalyst chamber outlet temperature
x = to be calculated
thermal efficiency of heat exchanger =
Two is therefore calculated to be:
Tfo is therefore calculated to be:
Step 7c. Calculate the auxiliary fuel requirement, Qaf
Enter the auxiliary fuel heat of combustion
for methane, use 21,502 BTU/Ib
also for methane, rho = 0.0408 Ib./scf
Qaf is therefore calculated to be:
this must be a positive number for burner flame stability
Summary of Variable Valuation
900.00 deg. F
Stream
IN - Sensible Heat
Auxiliary Air
Auxiliary Fuel
Waste Gas
subscript j rho sub j Q sub j
Ib/scf scfm
a
af
wo
n/a
0.0408
0.0739
n/a
0.70
447.00
x deg. F
100.00 deg. F
x deg. F
900.00 deg. F
0.70
660.00 deg. F
340.00 deg. F
21,502.00 neg. del. h sub c
sub af, BTU/lb.
0.70 scfm
Cpm sub j T sub j
EITU/#'F deg. F
n/a n/a
not used 77 for methane
0.248 660.00 for air
OUT - Sensible Heat
Waste stream
0.0739 447.70 0.248 900.00 assuming
primarily air
Energy Balance around Combustor
IN - Sensible Heat, rho'Q*Cp'(Ti-Tref)
Auxiliary Air
Waste Gas
OUT - Sensible risat
Waste Stream
OUT - Losses
tan percent of total energy input
GENERATION -Heat of Combustion, rno'Q'Ineg.del.h sub c
Waste Gas
Auxiliary Fuel
Step 8c. Verify that auxiliary fuel requirement will stabilize burner flame
Five percent of Total Energy Input equals:
Auxiliary rue! Energy Input equals:
subscript
a
wo
fi
Jel.h sub c)
wo
af
Value,
BTU/min
0
4.775
6,753
675
2.105
817
338 BTU/min
617 BTU/min
C-3
-------
If Aux. Fuel Energy Input is greater than 5% Total Energy Input,
burner flame should be stable.
Step 9c. Estimate the inlet temperature to the catalyst bed, Tri
Tri is calculated to be: 674.91 deg. F
Delta T (temperature rise across catalyst bed) equals: 225.09 deg. F
Step 10c. Calculate total volumetric flow rate of gas through the incinerator, Qfi
Flue Gas Flow Rate, Qfi, equals:
Step 11c. Calculate the volume of catalyst in the catalyst bed.
Given Qfi and nominal residence time,
catalyst volume can be calculated.
First, adjust Qfi to petro-chemical industry
convention of 60 deg. F, 1 atm.
Qfi(60) =
Input catalyst space velocity in per minute
Precious metal catalysts vary: 166.67 to 1,000 /minute
Volume of catalyst bed therefore equals:
447.70 scfm
433.53 cfm
500 /min
0.87 cubic feet
Section 3.5.1 - Estimating Total Capital Investment
Scope of Cost Correlations
Incinerator Type
Fixed-bed Catalytic
Fluid-bed Catalytic
Total (flue)
flow, scfm
2,000-50,000
2.000-25,000
packaged
packaged
If Qfi is outside these parameters for the specific incinerator type,
this costing formulation may not be used.
Section 3.5.1.1 - Equipment Costs, EC
Catalytic Incinerators
Total flue gas rate, Qfi
heat recovery factor
Fixed-Bad and Monolithic Catalytic incinerators
Heat Recover/ Hauioment Cost , EC
'percent) 1388 dollars
0 531,169
35 $46,727
50 336,513
70 $42,118
Fluid-Bad Catalytic incinerators
Heat Recovery Equipment Cost , EC
(percent) 1988 dollars
0 $90,710
35 $94.936
50 $33,674
70 392.496
447.70 scfm
70 oercant
delta P
,n.
-------
Section 3.5.1.2 - Installation Costs
Choose Equipment Cost based on Catalytic
Incinerator type and Heat Recovery percent
and enter base equipment cost (EC) here >
$44,410
Section 3.5.2 - Estimating Total Annual Cost
Section 3.5.2.1 - Direct Annual Costs
Enter the delta P, fixed-bed catalytic incinerate 16):
Enter the delta P, fluid-bed catalytic incinerator 16-10):
Enter the delta P (based on heat recovery)
(from 3.5.1.1, above)
Number of hours/year of operation:
Enter the combined motor/fan efficiency (decimal):
Enter the cost per kilowatt hour of electricity:
Enter natural gas unit cost in t/scf:
Fixed-Bed:Power (fan), in kilowatts, equals
Fluid-Bed: Power (fan), in kilowatts, equals
Electricity Cost, S/yr, equals
Annual Fuel Cost:
(Methane assumed to be combustor fuel)
Rate of fuel usage
Annual Fuel Cost, in $/yr, equals
6 in. Water
8 in. Water
15 in. Water
6000 hours/year
0.6
0.059 $/kWh
0.0033 $/scf
1.83 kW
2.01 kW
S649 per year
$711 per year
0.70 scfm
$835 per year
Fixed-bed
Fluid-bed
Total Capital Investment
Table 3-8, page 3-52. OAQPS Control Cost Manual (EPA 450/3-90-006, January 1990)
Capital Cost Factors for Catalytic Incinerators
Direct Costs
Purchased Equioment Costs
Incinerator (EC! + auxiliary equipment
Instrumentation
Sales Tax
Freight
Purchased Equioment Cost, PEC
Direct Installation Costs
Foundation and supoorts
Handling and erection
Electrical
Insulation for auctworx
Painting
Direct Installation Cost
Enter Site Preparation Costs
Enter Bui/dings Casts
Total Direct Cost, DC
Indirect Costs (installation)
Engineering
Construction or field expenses
$44,410 as estimated,A
$4,441 A * 0.10
$1,332 A ' 0.03
$2,220 A 0.05
$52.404 B = 1.18 ' A
$4,192
$7,336
32.096
$1.048
$524
$524
$15,721
B
3
B
3
B
B
B
0.08
0.14
' 0.04
* O.C2
" 0.01
0.01
* 0.30
$0 As required, SP
$0 As required, Bldg.
$68,125 8 ' 1.30 + SP -t- Bldg.
$5,240 B ' 0.10
52,520 B ' 0.05
-------
Contractor fees
Start-up
Performance test
Contingencies
Total Indirect Cost, 1C
Total Capital Investment =DC + 1C
$5,240 B * 0.10
$1,048 B 0.02
$524 B * 0.01
$1,572 B * 0.03
$16,245 B * 0.31
$84,370 B * 1.61 + SP + Bldg.
Total Annual Cost
Table 3.10 page 3-54, OAQPS Control Cost Manual (EPA 450/3-90-006, January 1990)
Annual Costs for Catalytic Incinerators
Total Capital Investment (from previous table)
Cost Item
Direct Annual Costs, DC
Operating Labor
Operator
Supervisor
Operating materials
Maintenance
Labor
Material
Catalyst Replacement
Utilities
Natural Gas, $/scf
Electricity, $/kWh
Total Direct Cost. DC
Indirect Annual Costs, 1C
Overhead
Admin, charges
Property taxes
Insurance
Capital recovery
Total Inairect Costs, :C
Total Annual Cost
Suggested
Factor
0.5 firs/shift
15% of operator
0.5 hrs/shift
Equals Maint. Labor
Unit Cost
$12.36/hour
$14.26/hour
Every 5 years $3500/cu.ft. Imetal oxidel
$ 0.0033 per scf
$ 0.059 per kWh
Sixty percent of sum
of op., supv., & maint.
labor & maint. mat'l
TCI * 0.02
TCI ' 0.01
TCI ' 0.01
CRF [TCI - 1.08 ' (Cat. Cost)!
TAC = DC - 1C
$84,370
Catalytic
Fluid-Bed
$4,860
$729
$0
$5,348 *
$5,348
$607
$835
$649 Fixed-bed
$18,375
$14,340
$1,687
$844
$844
$13,522
516,397
335,272 per year
* based on user-orovided hours/vnar of ooeration
CRF: The capital recovery factor, CRF, is a function of the catalyst or equipment life (typically, 5 and 10
years, respectively) and the opportunity cost of the capital (i.e.. interest rate). For example, for a 10 year
equipment life and a 10% interest rate, CRF = 0.1623.
C-6
-------
OAQPS Control Cost Analysis for Regenerative Incinerators
Section 3.4.1 - Steps Common to Regenerative and Catalytic Units
Step 1. Establish Design Specifications
Enter the following data corresponding to the wasta gas:
Volumetric Flow Rate, scfm (77 degrees F, 1 atml
Temperature, preheater inlet, Twi
(Assume balance oxygen composition)
Chemical Composition of Combustibles
enter names here > ethanol
acetaldeh yde
Heating Value of Combustibles
ethanol
acataldehyde
Enter the number of hours/year of operation:
Enter the following data specific to the incinerator:
Desired Control Efficiency /best to assume >0.90)
Combustion Chamber Outlet Temperature
Desired Percent Energy Recovery, decimal
choose 0, 0.35. 0.50, 0.70, or 0.95
Step 2. Verify that the oxygen content of the waste gas exceeds 20%.
Air Content =
Oxygen Content =
Step 3. Calculate the LEL and the Percent of the LEL of the gas mixture
Enter the LEL of the following compounds:
ethanol
aca taideh yds
sum of x suo i, i equals 1 to n
Lower Explosive Limit of the mixture equals:
Percent LEL of the mixture equals:
if greater than 25%, dilution air snoold be added
'o avoid fire insurance regulations
447.00 scfm
100.00 deg. F
1,939.00 ppmv
19.39 ppmv
please use two most combustible
compounds. If less than two,
please enter 1's to avoid
division by zero errors
2,407.00 neg. del. h sub c, BTU/scf
2,149.00 neg. del. h sub c, BTU/scf
6000 hours/year
0.98
1,600.00 deg. F
0.70
99.80 Vol. %
20.86 percent
3.25 vol. %
3.97 vol. %
1,958.39
34,997.41 ppmv
5.60 percent
Step 4. Calculate the volumetric heat of combustion of the wasta gas stream
heat of combustion,
ethanol
acetaiaenyda
neat or comousticn for t?ie mixture is
Assuming waste gas is principally air (molecular
weight C3.37, jensny 0.0739 'b/scf), :hen
2.407,00 BTU/scf
:.:49.00 aTu/scr
4.71 3TU/scf
Heat of combustion per pound of incoming gas is
Section 3.4.2 - Steps Specific to Regenerative Units
Step 5t. Establish incinerator operating temperature, Tfi
operating temperature (comb, chamber sutler 'smn.
Stac 6t. Calculate wasta gas -amperatura at. prsnsatar ax;t
1,300.GO deg. ,-
32500 ppmv
39700 ppmv
-------
Define the following temperatures:
Two, VOC stream leaving heat exchanger
Twi, waste gas inlet temperature
Tfo, flue temperature after heat exchanger
Tfi, incinerator operating temperature
x = to be calculated
thermal efficiency of heat exchanger =
Two is therefore calculated to be:
Tfo is therefore calculated to be:
Step 7t. Calculate the auxiliary fuel requirement, Qaf
Enter auxiliary fuel heat of combustion
for methane, use 21,502 BTU/lb
also for methane, rho = 0.0408 Ib./scf
Qaf is therefore calculated to be:
x deg. F
100.00 deg. F
x deg. F
1,600.00 deg. F
0.7
1,150.00 deg. F
550.00 deg. F
21,502.00 nag. del. h sub c
sub af, BTU/lb.
3.45 scfm
Summary of Variable Valuation
Stream subscript | rho sub j
Ib/scf
IN - Sensible Heat
a n/a
0.0408
0.0739
Auxiliary Air
Auxiliary Fuel
Waste Gas
af
wo
OUT - Sensible Heat
Waste stream
0.0739
Q sub j Cpm sub j T sub j
scfm HTU/#'F deg. F
n/a n/a n/a
3.45 not used 77.00 for methane
447.00 0.255 1,150.00 for air
450.45 0.255 1,500.00 assuming
primarily air
Value,
subscript BTU/min
Energy Balance around Combustor
IN - Sensible Heat, rho'O'Cp "(Ti-Traf)
Auxiliary Air a 0
Waste Gas wo 9,038
OUT - Sensible Heat
Waste Stream fi 12,928
OUT - Losses
ten oercent of total energy input 1,293
GENERATION -Heat of Comdustion. rho *Q'!neg.del.h sub o)
Waste <3as wo 2,105
Auxiliary Fuel af 3,029
Step St. Verify that auxiliary fuel requirement will stabilize burner flame
cive oercant of Total Energy incut ^nuais: 546 3TU/mm
Auxiliary AJBI energy nout aquais: 3,029 3TU/mm
If Aux. Fuel energy input is greater than 5% Total Energy Input,
burner *!ame should be Jtaoia.
Step 9t. Calculate Total Volumetric Flow Rate of gas through incinerator, Qfi
Rue Gas Flow Rate, 2fi, equals: 450.45 scfm
Section 3.5.1 - Estimating Total Caoita! Investment
-------
Scope of Cost Correlations
Incinerator Type
Thermal - regen.
Thermal - recup.
Total (flue)
flow, scfm
500-50,000
10,000-100,000
field-erected
packaged
If Qfi is outside these parameters for the specific incinerator type,
this costing formulation may not be used.
Section 3.5.1.1 - Equipment Costs, EC
Regenerative Incinerators
Total flue gas rate, Qfi
heat recovery factor
Heat Recovery
(percent)
0
35
50
70
95
Section 3.5.1.2 - Installation Costs
Equipment Cost , EC
1988 dollars
$43,403
$64,749
$78,672
$98,321
$225,612
Choose Equipment Cost based on Heat
Recovery percent and
Enter bass equipment cost (EC) here ->
450.45 scfm
0.7
delta P
in. Water
0
4
8
15
35
$103,671
Section 3.5.2 - Estimating Total Annual Cost
Section 3.5.2.1 - Direct Annual Costs
Enter the delta P for a regenerative incinerator (4):
Enter the delta P /based on heat recovery!
/from 3.5.1.1 , above/
Number of hours/year of ooeration:
Enter the combined motor/fan efficiency /decimal):
Enter the cost per kiiowatt hour of electricity:
Enter natural gas unit cost in $/scf:
(fani, in xilowarts.
Saotnciry Cost, */yr. 3duais
Annual Fual Cost:
'Methana assumed ;o ce comoustor fuai)
Rats of fuel usage
Annual Fuel Cost, in S/yr, equals
4 in. Water
15 in. Water
6000 hours/vear
0.6
0.059 $/kWh
0.0033 $/scf
1.57 !
-------
Incinerator (EC) + auxiliary equipment
Instrumentation
Sales Tax
Freight
Purchased Equipment Cost, PEC
Direct Installation Costs
Foundation and supports
Handling and erection
Electrical
Piping
Insulation for ductwork
Painting
Direct Installation Cost
Enter Site Preparation Costs:
Efiter Buildings Costs:
Total Direct Cost, DC
Indirect Costs (installation)
Engineering
Construction or field expenses
Contractor fees
Start-up
Performance test
Contingencies
Total Indirect Cost, 1C
Total Capital Investment = DC -I- 1C
$103.571
$10,367
$3,110
$5,184
$122,332
$9,787
$17,126
$4,393
$2,447
$1,223
$1,223
$36,699
as estimated, A
A
A
A
B
B
B
B
B
B
B
B
0.10
* 0.03
* 0.05
= 1.18 ' A
* 0.08
0.14
0.04
0.02
* 0.01
0.01
0.30
$0 As required, SP
$0 As required, Bldg.
$1 59,031 B ' 1.30 + SP + Bldg.
$12,233
$6,1 17
$12,233
$2,447
$1,223
$3,670
$37,923
8
B
B
B
B
B
B
0.10
0.05
" 0.10
* 0.02
0.01
0.03
0.31
:196,954 B ' 1.61 + SP + Bldg.
Total Annual Cost
Table 3.10 page 3-54, OAQPS Control Cost Manual (EPA 450'3-90-006, January 1990)
Annual Costs for Regenerative and Catalytic incinerators
Total Capital Investment (from previous table)
$196,354
Cost Item
Direct Annual Costs, DC
Operating Laoor
Operator
Supervisor
Ooaratintj materials
Suggested
Factor
0.5 hrs/shift
'. 5% of operator
Unit Cost
$12.96/hour
Regenerative
$4,360
$729
Maintenance
Labor
Material
0.5 hrs/shift
Equal to Mamt. Labor
tJ4.26/hour
55,343
35,348
Utilities
Natural Gas, $/scf
Electricity, $
-------
oaerav.r.g, supv., i mamt.
labor & maint. materials
Administrative charges TCI * 0.02 - $3,939
Property taxes TCI " 0.01 $1,970
Insurance TCI * 0.01 $1,970
Capital recovery CRF *TCI $32,064
Total Indirect Costs, 1C $49,713
Total Annual Cost, TAC TAG = DC + 1C $70,689
* based on user-provided hours/year of operation
CRF: The capital recovery factor, CRF, is a function of the equipment life (typically 10
years) and the opportunity cost of the capital (i.e., interest rate). For example, for a 10 year
equipment life and a 10% interest rate, CRF = 0.1628.
C-il
-------
APPENDIX D
BAY AREA AIR QUALITY MANAGEMENT DISTRICT
REGULATION 8 RULE 42
LARGE COMMERCIAL BREAD BAKERIES
n i
-------
REGULATION 8
ORGANIC COMPOUNDS
RULE 42
LARGE COMMERCIAL BREAD BAKERIES
INDEX
8-42-100 GENERAL
8-42-101 Description
8-42-110 Exemption, Small Bakeries
8-42-111 Exemption, Low Emitting Ovens
8-42-112 Exemption, Existing Ovens
8-42-113 Exemption, Miscellaneous Bakery Products
8-42-114 Exemption, Chemically Leavened Products
8-42-200 DEFINITJONS
8-42-201 Approved Emission Control System
8-42-202 Baseline Emissions
8-42-203 Bread
8-42-204 Fermentation Time
8-42-205 Large Commercial Bread Bakery
8-42-206 Leaven
8-42-207 Yeast Percentage
8-42-300 STANDARDS
8-42-301 New and Modified Bakery Ovens
8-42-302 Emission Control Requirements, New and Modified Ovens
8-42-303 Emission Control Requirements, Existing Ovens
8-42-304 Delayed Compliance, Existing Ovens
8-42-400 ADMINISTRATE REQUIREMENTS
8-42-401 Compliance Schedule
8-42-402 Delayed Compliance Schedule
3-42-500 WCNITCRING AND RECORDS (Not Induced)
3-42-400 ' MANUAL Or PROCEDURES
8-42-601 Determination of Emissions
3-^2-602 Emission Calculation Procedures
3-42-1
Septemoer 20, 1389
-------
REGULATION 8
ORGANIC COMPOUNDS
RULE 42
LARGE COMMERCIAL BREAD BAKERIES
(Adopted September 20, 1989)
8-42-100 GENERAL
8-42-101 Description: The purpose of this rule is to limit the emission of precursor organic
compounds from bread ovens at large ijommercial bread bakeries.
8-42-110 Exemption, Small Bakeries: This rule shall not apply to bakeries whose total
production of bread, buns, and rolls per operating day is less than 45,450 kg
(100,000 pounds), averaged over all oparating days in any one month.
8-42-111 Exemption, Low Emitting Ovens: Ovgns demonstrated to the satisfaction of the
APCO to emit less than 68.2 kg (1£iO pounds) of ethanol per operating day
averaged over a period of one year :>hall be exempt from the requirements of
Section 8-42-301.
8-42-112 Exemption, Existing Ovens: The requ rements of Section 8-42-303 shall not apply
to ovens, which commenced operation prior to January 1, 1988 and which are
demonstrated to the satisfaction of tha APCO to emit less than 113.7 kg (250
pounds) of ethanol per operating day, averaged over a period of one year.
8-42-113 Exemption, Miscellaneous Bakery Products: This rule does not apply to
equipment used exclusively for the ba
-------
8-42-205 Large Commercial Bread Bakery: Any bakery producing more than 45,454 kg
(100,000 pounds) of breads, buns, and rolls per day.
8-42-206 Leaven: To raise a dough by causing gas to thoroughly permeate it.
8-42-207 Yeast Percentage: Pounds of yeast per hundred pouncs of total recipe flour,
expressed as a percentage.
8-42-300 STANDARDS
8-42-301 New and Modified Bakery Ovens: Effective January 1, 1989, a person subject to
this rule shall not operate the following equipment unless the requirements of
Section 8-42-302 are met:
301.1 Any newly constructed oven commencing operation after January 1, 1989.
301.2 Any newly constructed oven replacing an existing oven and commencing
operation after January 1.1989.
301.3 Any existing oven which has been modified, with modifications completed
after January 1, 1989, at a cost exceeding 50% of replacement cost of the
oven.
301.4 Any oven with a change in production after January 1, 1989, resulting in an
emission increase, averaged over a 30 day period, of 68.2 kg (150 pounds)
per operating day above the baseline emissions.
8-42-302 Emission Control Requirements, New and Modified Ovens: Ail new and
modified ovens shall be required to vent all emissions to an approved emission
control system capable of reducing emissions of precursor organic compounds by
90% on a mass basis.
8-42-303 Emission Control Requirements, Existing Ovens: Effective January 1, 1992, all
existing ovens which commenced operation prior to January 1, 1989, shall be
required to vent emissions to a control system meeting the following standards:
303.1 Emission collection system shall capture all emissions of precursor organic
compounds from all oven stacks.
303.2 Collected emissions shall be vented to an approved emission control device
which has a destruction efficiency of at least 90% on a mass basis.
8-42-304 Delayed Compliance, Existing Ovens: In lieu of complying with the requirements
of Section 8-42-303, an applicant may sleet to replace those ovens suoject to
Section 8-42-303 with new ovens meeting the requirements of Section 3-42-302 oy
January 1, 1994. Such ejection must be made by January 1, 1991, subject to
approval of the APCO. In approving such an election, the APCO may require the
posting of a bond and may impose permit conditions on the existing subject ovens
in order to assure compliance with the January 1,1994 installation of new evens.
8-42-400 ADMINISTRATIVE REQUIREMENTS
8-42-401 Compliance Schedule: Any person subject to the requirements of Section 3-42-
303 of this rule shall comply with the following increments of progress:
4G1.1 By January 1, 1S90: Submit a status r-soort tc the APCC stating -,T\a actions
under consideration Jor retrofitting or -gciacng 3xisi;ng ovens.
4Q1.2 3y «anuary 1, 19S1: Submit a oian describing the methods proposed tc oe
used to comply with 8-42-303.
401.3 By March 31, 1991: Submit a completed application for any Authority :o
Construct necessary to comply with these requirements.
401.4 By January 1,1992: Be in full compliance with all applicable requirements.
8-42-402 Delayed Compliance Schedule: Any person seeking to ccmciy with this ruse
under Section 8-42-304 shall comply with the following increments of progress:
402.1 By January 1, 1991: Submit a plan describing the methcds proposed tc be
used to comply with 8-42-302.
8-42-4
September 20. i539
-------
8-42-600
8-42-601
8-42-602
Yt'
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
10.5
14 0
4.5
15.0
15.5
402.2 By January 1, 1992: Submit to the APCO a status report on the purchase of
the new ovens.
402.3 By January 1, 1993: Submit u completed application for any. Authority to
Construct necessary to comply with these requirements.
402.4 By January 1,1994: Be in full compliance with all applicable requirements.
MANUAL OF PROCEDURES
Determination of Emissions: Emissions of oi-ganics shall be measured as
prescribed in the Manual of Procedure;;, Source Test Procedure ST-32.
Emission Calculation Procedures: If emission measurements conducted in
accordance with Section 8-42-601 are not available for a specific bakery product,
oven emissions shall be calculated using the emission factors in Table I.
TABLE I
Pounds VOC/ton
bakery product
.8488
1.0711
1.2934
1.5157
1.7380
1.9603
2.1826
2.4049
2.6272
2.8495
3.0718
3.2941
3.5163
3.7386
3.9609
4.1832
4.4055
4.6278
4.8501
5.0724
5.2947
5.5170
5.7393
5.9616
6.1839
6.4061
6.5284
6.3507
7.0730
7.2953
Yt'
16.0
16.5
17.0
17.5
18.0
18.5
19.0
19.5
20.0
20.5
21.0
21.5
22.0
22.5
23.0
23.5
24.0
24.5
25,0
25.5
26.0
26.5
27.0
27.5
28.0
2S.5
29.0
29.5
30.0
Pounds VOC/ton
bakery product
7.5176
7.7399
7.9622
8.1845
8.4068
8.6291
8.8514
9.0737
9.2959
9.5182
9.7405
9.9628
10.1851
10.4074
10.6297
10.8520
11.0743
11.2966
11.5189
11.7412
115635
12.1857
12.4080
12.6303
12.8526
13.0749
"3.2972
13.5195
13.7413
*Yt = (yeast percentage) * (fermentation time).
If yeast is added in 2 steps, Yt = ((initial yeast percentage) * (total fermentation time)
(remaining yeast percentage) * (remaining fermentation time)].
3-42-5
September 20, 1SS9
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APPENDIX E
SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT
RULE 1153
COMMERCIAL BAKERY OVENS
E-l
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(Adopted January 4, 1991)
RULE 1153. COMMERCIAL BAKERY OVENS
(a) Applicability
This rule controls volatile organic compound (VOC) emissions from commercial
bakery ovens with a rated heat input capacity of 2 million BTU per hour or more
and with an average daily emission of 50 pounds or more of VOC.
(b) Definitions
For the purpose of this rule the following definitions shall apply:
(1) AVERAGE DAILY EMISSIONS is the product of the total calendar
year emissions (in tons/year) divided by the number of days the oven was
employed for production during that year.
(2) BAKERY OVEN is an oven for baking bread or any other yeast leavened
products by convection.
(3) BASE YEAR is the calendar 1989 or any subsequent calendar year in
which the average daily emissions are 50 pounds or more per day.
(4) EMISSIONS are any VOC formed and released from the oven as a result
of the fermentation and baking processes of yeast leavened products.
(5) EXEMPT COMPOUNDS are any of the following compounds which
have been determined to be non-precursors of ozone:
(A) Group I (General)
chlorodifluoromethane (HCFC-22)
dichlorotrifiuoroethane (HCFC-123)
tetrafluoroethaae (HFC-134a)
dichlorofluoroetnane (HCFC-141b)
chlorodifluoroethane (HCFC-142b)
(B) Group II (Under Review)
meihyiene cnionde
1,1,1-trichloroethane (methyl chloroform)
niSuoromethane (FC-23)
trichlorotrifluoroethane (CFC-113)
dichlorodifhioromethane (CFC-12)
trichlorofluoromethane (CFC-11)
dichlorotetralfuoroethane (CFC-114)
chloropentafhioroethane (CFC-115)
1153 -1
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Rule 1153 (Cont.) (Adopted January 4,1991)
The Group n compounds may have restrictions on their use because they
are toxic or potentially toxic, or upper-atmosphere ozone depleters, or
cause other environmental impact*. The District Board has adopted a
policy which states that chlorofluorocarbons (CFC) will be phased out at
the earliest practicable date on or before 1997.
(6) EXISTING OVEN is an oven that was constructed and commenced
operation prior to January 1,1991.
(7) FERMENTATION TIME is the elapsed time between adding yeast to
the dough or sponge and placing it iito the oven, expressed in hours.
(8) LEAVEN is to raise a dough by causing gas to permeate it
(9) VOLATILE ORGANIC COMPOLT^DS (VOC) is any volatile chemical
compound that contains the element of carbon compound, excluding
carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or
carbonates, methane, and exempt ccmpounds.
(10) YEAST PERCENTAGE is the pounds of yeast per hundred pounds of
total recipe flour, expressed as a per:entage.
(c) Requirements
(1) No person shall operate an existing bakery oven unless VOC emissions
are reduced by at least:
(A) 70 percent (by weight) for ar oven with a base year average daily
VOC emissions of 50 pounds or more, but less than 100 pounds.
(B) 95 percent by weight for an oven with a base year average daily
VOC emissions of 100 pound; or more.
(2) No person shall operate a new bakery oven unless VOC emissions are
reduced by at least 95 percent by weight if the uncontrolled average daily
VOC emissions are 50 pounds or more.
(d) Compliance Schedule
No person shall operate a bakery oven subject to this rule unless the following
increments of progress are met:
(1) For bakery ovens subject to subparasraph (c)(l)(A):
(A) By January 1, 1992, submit required applications for permits to
construct and operate.
1153-2
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Rule 1153 (Cont.) (Adopted January 4, 1991)
(B) By July 1, 1993, demonstrate compliance with subparagraph
(2) For bakery ovens subject to subparagraph (c)(l)(B):
(A) By January 1, 1993, submit required applications for permits to
construct and operate.
(B) By July 1, 1994, demonstrate compliance with subparagraph
(3) For bakery ovens subject to subparagraph (c)(2) be in compliance by
July 1, 1992 or by the date of installation, whichever is later.
(e) Alternate Compliance Schedule
The subparagraph (d)(l) and (d)(2) compliance deadlines may be postponed by
one year if the owner of a bakery oven elects to replace the existing oven with a
new one. Such election must be" made by January 1, 1992 via a compliance plan
submitted to, and subject to approval of, the Executive Officer or his designee.
In approving such an election, the Executive Officer may impose interim
conditions or control measures on the existing oven in order to assure
compliance pending the installation or construction of the new, replacement
oven.
(f) Exemptions
The provisions of paragraphs (c) and (d) do not apply to any existing bakery
oven that emits less than 50 pounds of VOC per operating day on an
uncontrolled basis. Daily VOC emissions shall be determined according to the
calculation procedures of Attachment A, or according to any test methods
specified in paragraph (h).
(g) Recorckesping Requirements
Any person operating a bakery oven subject to this rale and claiming an
exemption under paragraph (f) shall maintain a daily record of operations,
including, but not limited to, the amount of raw material processed, yeast
percentage, fermentation time, and the type of product baked. Such records
shall be retained in the owner's or operator's files for a period of not less than
two years.
1153 - 3
-------
Rule 1153 (Cont.) (Adopted Januaiy 4,1991)
(h) Test Methods
EPA Test Method 25, or SCAQMD Test Method 25.1, or any other method
determined to be equivalent and approved by the Executive Officer or his
designee, may be used to determine compliance with this rule.
1153-4
-------
Rule 1153 (Cont.)
(Adopted January 4,1991)
ATTACHMENT A
Yt
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
15.5
Pounds VOC/ton
Bakery Product
0.8488
1.0711
12934
1.5157
1.7380
1.9603
2.1826
2.4049
2.6272
2.8495
3.0718
32941 '
3.5163
3.7386
3.9609
4.1832
4.4055
4.6278
4.8501
5.0724
52947
5.5170
5.7393
5.9616
6.1839
6.4061
6.6284
6.8507
7.0730
72953
Yt'
16.0
16.5
17.0
17.5
18.0
18.5
19.0
19.5
20.0
20.5
21.0
2L5
22.0
22.5
23.0
23.5
24.0
24.5
25.0
25.5
26.0
26.5
27.0
215
28.0
28.5
29,0
29.5
30.0
Pounds VOC/ton
Bakery Product
7.5176
7.7399
7.9622
8.1845
8.4068
8.6291
8.8514
9.0737
92959
9.5182
9.7405
9.9628
10.1851
10.4074
10.6297
10.8520
11.0743
112966
11.5189
11.7412
11.9635
12.1857
12.4080
12.6303
12.8526
13.0749
132972
13.5195
13.7418
Yt = (yeasi percentage) x (fermentation tune)
If yeast is added in 2 steps, Yt = (initial yeast percentage)
^total fermentation time) + (remaining Yeast percentage)
^remaining fermentation time)
1153 - 5
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TECHNICAL REPORT DATA
mid Instructions on
*yt.-:e bffor* c
REPORT NO.
EPA 453/R-92-017
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Alternative Control Technology Document for
Bakery Oven Emissions
5. REPORT DATE
December 1992
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT \Q
C. Wally Sanford
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
Post Office Box 12194
Research Triangle Park, NC 27709-2194
ic. PROGRAM ELEMENT NO.
11 CONTRACT,GRANT NO
68-Dl-Oir8
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Air Quality Planning and Standards
US Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14 SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This document was produced in response to a request by the baking industry for
Federal guidance to assist in providing a more uniform information base for State
decision-making with regard to control of bakery oven emissions. The information !
in the document pertains to bakeries that produce yeast-leavened bread, rolls, buns, !
and similar products but not crackers, sweet goods, or baked foodstuffs that are not !
yeast leavened. Information on the baking processes, equipment, operating parameters,'
potential emissions from baking, and potential emission control options are presented.
Catalytic and regenerative oxidation are identified as the inost appropriate existing
control technologies applicable to VOC emissions from bakery ovens. Cost analyses
for catalytic and regenerative oxidation are included. A predictive formula for use
in estimating oven emissions has been derived from source tests done in junction
with the development of this document. Its use and aoDlicafailitv are described.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b IDENTIFIERS,OPEN ENDED TH3MS U COSATI Field Crou3
Bakery catalytic oxidation
oven regenerative oxidation
emissions dough formula
baker's percent predictive formula
fermentation time
VOC controls
2 thano1
13. 2I3T=H3L,T;CN jr-rS
Release Unlimited
13 jECUSiT'v CLASS
lUnclasaified
10
120 SECLlRlT'-1 CLASS
[Unclassified
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