Envirwimeiilal Protection
Agency
USING BIOREACTORS TO CONTROL
AIR POLLUTION
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EPA-456/R-03-003
September 2003
USING BIOREACTORS TO CONTROL
AIR POLLUTION
Prepared by
The Clean Air Technology Center (CATC)
U.S. Environmental Protection Agency (E143-03)
Research Triangle Park, North Carolina 27711
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Information Transfer and Program Integration Division
Information Transfer Group (E143-03)
Research Triangle Park, North Carolina 27711
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DISCLAIMER
This report has been reviewed by the Information Transfer and Program Integration
Division of the Office of Air Quality Planning and Standards, U.S. Environmental Protection
Agency and approved for publication. Approval does not signify that the contents of this report
reflect the views and policies of the U.S. Environmental Protection Agency. Mention of trade
names or commercial products is not intended to constitute endorsement or recommendation for
use. Copies of this report are available from the National Technical Information Service,
U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Virginia 22161, telephone
number (800) 553-6847.
11
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FOREWORD
The Clean Air Technology Center (CATC) serves as a resource on all areas of
emerging and existing air pollution prevention and control technologies, and provides public
access to data and information on their use, effectiveness and cost. In addition, the CATC will
provide technical support, including access to EPA's knowledge base, to government agencies
and others, as resources allow, related to the technical and economic feasibility, operation and
maintenance of these technologies.
Public Access and Information Transfer
INTERNET / World Wide Web Home Page
http ://www. epa.gov/ttn/catc
Communications
CATC Info-Line: (919) 541-0800 (English)
CATC/CICA Info-Line: (919) 541-1800 (Spanish)
Toil-Free (800) 304-1115 (Spanish)
FAX: (919) 541-0242
E-Mail: catcmail@epa.gov
Data Resources
RACT/BACT/LAER Clearinghouse (RBLC)
Query, view and download data you select on
- Source Specific Technology Applications
- Air Pollution Regulatory Requirements
CATC PRODUCTS
download technical reports, cost information and software
Related Programs and Centers
• CICA - U.S.-Mexico Border Information Center on Air Pollution /
Centra de Information sobre Contamination de Aire Para la Frontera
entreEE.UU. YMexico
• SBAP - Small Business Assistance Program
• International Technology Transfer Center for Global Greenhouse Gasses
in
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ACKNOWLEDGMENTS
This technical bulletin was made possible through the diligent and persistent efforts of
Lyndon Cox and Dexter Russell, Senior Environmental Employees with the Clean Air
Technology Center (CATC). Lyndon and Dexter did an exceptional job identifying information
sources, gathering relative data and putting this bulletin together. The CATC also appreciates
the helpful and timely comments and cooperation of the following peer reviewers:
Charles Darvin
Air Pollution Control Division
National Risk Management Research Laboratory
Office of Research and Development
U.S. EPA
Mohamed Serageldin
Emission Standards Division
Office of Air Quality Planning and Standards
Office of Air and Radiation
U.S. EPA
In addition, the CATC thanks the individuals, companies and institutions who supplied
information on bioreaction technology used to prepare this Technical Bulletin. Contributors are
indicated in the REFERENCES section of this bulletin.
IV
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TABLE OF CONTENTS
TOPIC Page
DISCLAIMER ii
FOREWORD iii
ACKNOWLEDGMENTS iv
TABLE OF CONTENTS v
FIGURES vi
TABLES vii
INTRODUCTION 1
What is Bioreaction? 1
Why is Bioreaction Important? 1
OVERVIEW 2
How do Bioreactors Work? 2
FACTORS AFFECTING PERFORMANCE:
VARIABLES AND LIMITATIONS 3
Temperature 3
Moisture 4
Care and Feeding 5
Acidity 5
Microbe Population 6
BIOREACTOR PROCESSES 7
Biofilters 8
Biotrickling Filter 12
Bioscrubber 15
Other Bioreactor Technologies 18
CONTROL OPTIONS AND COST COMPARISONS 19
Combustion Control Devices 20
Non-Combustion Control Devices 23
Cost Comparisons 23
REGULATORY ISSUES 24
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TABLE OF CONTENTS (continued)
CONCLUSIONS 25
REFERENCES 27
APPENDIX A: CONTROL DEVICE OPERATING COST ASSUMPTIONS 28
FIGURES
1. Basic Biofilter 2
2. Biofilter with Emissions Recycle 9
3. Biofilters in Series, Horizontally 9
4. In-Ground Biofilter 10
5. Photograph of four Biofilters being installed in Arlington, TX
At Central Regional Wastewater System Plant 10
6. Trickling Filter 13
7. Biotrickling Filter 14
8. Bioscrubber 17
9. Regenerative Thermal Oxidizer Operating Modes 21
10. Three-Phase Recuperative Thermal Oxidizer 22
11. Catalytic Oxidizer 22
VI
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TABLE OF CONTENTS (continued)
Tables
1. Bioreactor Re-Acclimation Times After Periods of Non-Use 7
2. Existing Biofilter Design Characteristics Summary 11
3. Biofilter Cost per Unit Volume of Air Flow 12
4. General Characteristics of Biotrickling Filters 15
5. Design Characteristics for Existing Biotrickling Filters 16
6. Cost for Biotrickling Filter per Unit Volume of Air Flow 16
7. Bioscrubber Design Characteristics 18
8. Estimated Control Cost for Thermal and Catalytic Processes 24
9. Control Costs Using Bioreaction 25
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USING BIOREACTORS TO CONTROL
AIR POLLUTION
INTRODUCTION
Bioreactors use a natural process that is as old as life itself. For life to survive, it must
have a source of energy (food) and water (moisture). How these needs are used to remove
pollutants from contaminated air streams is the subject of this report.
What is Bioreaction?
In air pollution, bioreaction is simply the use of microbes to consume pollutants from a
contaminated air stream. Almost any substance, with the help of microbes, will decompose
(decay) given the proper environment. This is especially true for organic compounds. But
certain microbes also can consume inorganic compounds such as hydrogen sulfide and nitrogen
oxides.
Why is Bioreaction Important?
In a word, COST! The capital cost of a bioreaction installation is usually just a fraction
of the cost of a traditional control device installation.3 Operating costs are usually considerably
less than the costs of traditional technology, too. Thermal and catalytic control units consume
large volumes of expensive fuel. Bioreactors only use small amounts of electrical power to drive
two or three small motors. Normally, bioreactors do not require full-time labor and the only
operating supplies needed are small quantities of macronutrients. Biofilters, the most common
type of bioreactor, usually use beds (media on which microbes live) made from naturally
occurring organic materials (yard cuttings, peat, bark, wood chips or compost) that are slowly
consumed by the biomass (i.e., microbes). These organic beds usually can supply most of the
macronutrients needed to sustain the biomass. The beds must be replaced every 2 to 5 years
(Ref. 1), depending on the choice of bed material.
Bioreaction is a "green" process, whereas the traditional approaches are not. Combusting
any fuel will generate oxides of nitrogen (NOX), particulate matter, sulfur dioxide (SO2), and
carbon monoxide (CO). Bioreactors usually do not generate these pollutants or any hazardous
pollutants b. Products of a bioreaction consuming hydrocarbons are water and carbon dioxide
(C02).
Bioreactors do work, but microbes are finicky in what they will eat. Microbes need the
a Traditional Control Devices include thermal and catalytic oxidation, carbon adsorption and absorption (scrubbers).
b Bioreactors in northern states may need to heat emissions to obtain optimum conditions. The source of this heat may
generate combustion pollutants.
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right pollutant concentration, temperature, humidity and pH. There are many opportunities to
make mistakes in design and operations of a bioreaction system. Anyone thinking about
bioreaction would be wise to discuss their situation with a manufacturer's representative or an
expert in the field. If a particular air pollution control situation qualifies, the cost benefits can be
substantial.
OVERVIEW
How do Bioreactors Work?
Microbes have inhabited the Earth since the time that the Earth cooled sufficiently to
allow any form of life to exist. Microbes have a simple life cycle; they are born, eat, grow,
reproduce and die. Their diet is based primarily on carbon-based compounds, water, oxygen (for
aerobic reactions) and macronutrients. Bioreactors use microbes to remove pollutants from
emissions by consuming the pollutants. The concept is simple, but the execution can be quite
complicated.
Bioreactors have been used for hundreds of years to treat sewage and other odoriferous,
water-borne waste. About sixty years ago, Europeans began using bioreactors to treat
contaminated air (odors), particularly emissions from sewage treatment plants and rendering
plants. The initial process used a device called a "biofilter." A biofilter is usually a rectangular
box that contains an enclosed plenum on the bottom, a support rack above the plenum, and
several feet of media (bed) on top of the support rack. See Figure 1.
Decontaminated Air To Atmosphere
Contaminated
Air
Bed Media
Plenum
Fan
Water Drain to
Wastewater
Treatment
Figure 1. Basic Biofilter
A large number of materials are used for bed media such as peat, composted yard waste,
bark, coarse soil, gravel or plastic shapes (Ref 2). Sometimes oyster shells (for neutralizing acid
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build-up) and fertilizer (for macronutrients) are mixed with bed media. The support rack is
perforated to allow air from the plenum to move into the bed media to contact microbes that live
in the bed. The perforations also permit excess, condensed moisture to drain out of the bed to
the plenum.
A fan is used to collect contaminated air from a building or process. If the air is too hot,
too cold, too dry, or too dirty (with suspended solids), it may be necessary to pre-treat the
contaminated air stream to obtain optimum conditions before introducing it into a bioreactor.
Contaminated air is duct to a plenum. As the emissions flow through the bed media, the
pollutants are absorbed by moisture on the bed media and come into contact with microbes.c
Microbes reduce pollutant concentrations by consuming and metabolizing pollutants. During the
digestion process, enzymes in the microbes convert compounds into energy, CO2 and water.
Material that is indigestible is left over and becomes residue.
This is a very simple and brief explanation on how a bioreactor functions. In real-life,
things get a bit complicated. Variables that affect the operation and efficiency of a bioreactor
include: temperature, pH, moisture, pollutant mix, pollutant concentration, macronutrient
feeding, residence time, compacted bed media, and gas channeling. These are crucial variables
for which optimum conditions must be determined, controlled and maintained. In the body of
this report, a complete explanation of these processes is given.
Is a bioreactor right for your situation? This is not an easy question to answer. The
purpose of this report is to provide tools that you can use to determine if a specific contaminated
air stream is a good candidate for bioreaction treatment. Why bother? Bioreactors are far less
expensive than traditional control technologies to install and operate and, in many cases,
bioreactors approach efficiencies achieved by traditional control technologies.
FACTORS AFFECTING PERFORMANCE:
VARIABLES AND LIMITATIONS
Because bioreactors use living cultures, they are affected by many variables in their
environment. Below are variables and limitations that affect the performance of all bioreactors,
regardless of process type.
Temperature
All variables discussed here are important. However, probably the most important
variable affecting bioreactor operations is temperature. A blast of hot air can totally kill a
biomass faster than any other accident. Most microbes can survive and flourish in a temperature
range of 60 to 105 °F (30 to 41°C) (Ref. 3). It is important to monitor bed temperature at least
daily, but every eight hours would be safer. A high temperature alarm on the emissions inlet is
c Compounds not soluble in water are not good candidates for this technology.
3
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also a good safety precaution.
When emissions from a process are too hot, operators often pass hot emissions through a
humidifier that cools gases down by evaporative cooling. This is the most economical method
available for cooling emissions from 200 to 300 °F (93 to 149 °C) to below 105 °F (41 °C).
Besides the cooling effect, this process also increases the moisture content (humidifies emission
stream), a desirable side effect.
Although a blast of really hot air is the most lethal variable for microbes, cold air also
stops, but does not kill, microbes. Cold air can reduce microbe activity to the point that they
stop consuming pollutants and go into a state of suspended animation. Even freezing does not
kill microbes. After thawing, they can be re-acclimated in a relatively short period. For
optimum efficiency during winter months, it may be necessary to heat emissions using direct or
indirect methods. If heating is required, first look for a waste heat source such as excess steam,
boiler blowdown, or product cooling waste heat. As with cooling emissions, analyze your
source carefully to assure nothing is being added to the emission stream that will harm microbes
in the bioreactor, or will add to the overall pollution load. Additionally, some operators,
especially in northern states, insulate the bioreactor's exterior to reduce heat loss.
Moisture
The second most critical variable is bed moisture. Microbes need moisture to survive
and moisture creates the bio-film that removes (absorbs) pollutants from an air stream so that
they can be assimilated by microbes. Low moisture problems can be corrected by passing
emissions through a humidifier. Having emissions close to saturation (100 % relative humidity)
will solve most dry bed problems. Humidifiers need not be fancy, store-bought, stainless steel
process vessels. They can be made from an old FRP (fiber reinforced plastic) tank that is surplus,
or may be constructed from fiberglass panels with a lumber frame. The design should include
several rows of pipes near the top of the vessel with spray heads installed along their length, and
on/off valves on each pipe run to provide some control of humidity.
Biofilters are usually operated damp with no running or standing water. Low moisture,
for short periods, will not kill the microbes, but low moisture will greatly reduce efficiency.
Efficiency will be below optimum while microbes recover (re-acclimate) after a period of dry
bed conditions.
Flooding a reactor with water, on the other hand, will cause increased pressure drop
across the bed (adding additional load on the blower) and could cause a loss of efficiency
because of channeling that by-passes the bio-mass. Channeling could also cause the bed media
to collapse. For smooth operations, both conditions are to be avoided.
It is important to remember that a by-product of a bioreaction is water. If emissions are
saturated entering the process, there will be water condensing in the bed media. Always provide
space in the plenum for water to collect and a method to remove it from the plenum. The
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optimum bed media moisture range is from 40 to 60 percent water (Ref. 3). One way to monitor
bed moisture content continuously is to mount the support rack on load cells with an indicator.
Care and Feeding
In addition to a comfortable temperature and a moist environment, microbes need a diet
of balanced nutrients to survive and propagate. Pollutants provide the main source of food and
energy, but microbes also require macronutrients to sustain life. Decay of an organic bed media
can provide most macronutrients. However, if a bed is deficient in certain nutrients, microbes
will cease to grow and could begin to die.
Nitrogen is an essential nutrient for microbial growth. Microbes use nitrogen to build
cell walls (these walls contain approximately 15 percent nitrogen) and nitrogen is a major
constituent of proteins and nucleic acids. Microbes are capable of utilizing all soluble forms of
nitrogen, but not all nitrogen is available for reuse. Some nitrogen products from digestion
processes are gases (nitrogen oxides and ammonia) and small quantities will exit the process
with emissions. However, most of the nitrogen containing vapors are re-absorbed into the liquid
and are consumed by microbes. Also, some nitrogen products form water-soluble compounds
and are leached out of the system with condensing water.
Other essential macronutrients include phosphorus, potassium, sulfur, magnesium,
calcium, sodium and iron. Nitrogen, phosphorus, potassium (the NPK code on fertilizer labels)
may be added by incorporating agricultural fertilizer into bed media. Lesser soluble
macronutrients such as magnesium, calcium, sodium and iron, may be purchased in small
quantities at feed and seed stores. The nutrient content of a bed should be checked periodically
by submitting samples to a soils lab for analysis.
Acidity
Most bioreactors perform best when the bed pH is near 7, or neutral.d Some pollutants
form acids when they decompose. Examples of these compounds are: hydrogen sulfide, organic
sulfur compounds, and halogens (chlorine, fluoride, bromine and iodine). Production of acids
over time will lower pH and will eventually destroy microbes. If a process emits pollutants that
produce acids, a plan must be developed to neutralize these acids.
There are several techniques available to neutralize beds. Some may be incorporated into
specification for the bed material. One of the simplest techniques is to mix oyster shells with bed
media. The shells will eventually dissolve and have to be replaced (Ref. 5). How long the shells
last depends on how much acid is produced. Another simple technique is to install a garden
soaking hoses in the packing media during construction (Ref. 4). Periodically, a dilute solution
of soda ash (sodium carbonate, Na2 CO3) may be introduced into a bed when pH begins to
d Bioreactors that treat emissions that contain sulfur or sulfur compounds perform best when the pH is in the range 1 to
2 pH (Ref. 4).
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decline. Another technique is to spray dilute soda ash solution over the top of the bed.
However, this will probably be less effective than wetting the core of a bed with soaker hoses.
Microbe Population
Some equipment vendors can simulate a client's emission stream at their laboratory and
run bioreaction tests to determine which microbe strains perform best on a particular mix of
pollutants. They can then inoculate the bed media with those strains and start up with the "right"
microbes in place. Others allow nature to take her course by starting with a bed media that
contains a wide variety of living microbes such as compost, peat, or activated municipal sludge.
The strains that flourish on pollutants in an emission stream will eventually dominate the bed
environment. The natural method will take a little longer to acclimate to optimum efficiency,
but, because of the diversity of the strains of microbes, will be more adaptable in the long run.
Specific microbes that are developed in the lab are more susceptible to changes in the
environment than naturally generated microbes.
Periods of idle time will result in a change in the make-up of a population of microbes.
These changes will affect bioreactor performance and time will be required for the microbes
population to re-acclimate. Martin and Loehr (Ref.5) were concerned about this and conducted
experiments at the University of Texas (1996). They wanted to determine re-acclimation periods
after non-use periods of 1.67 days, 3.73 days and 2 weeks. These periods were intended to
coincide with plant closing for a 2 day weekend, 4 day holiday, and a two week plant shut down.
During periods of non-use, bioreactors were treated two ways: stagnant (no airflow through
them), and humidified (saturated air is passed through them). The time required to acclimate
microbes in the bioreactor initially and re-acclimatee (start-up) and after periods of non-use are
shown in Table 1.
Although results from this investigation are meager, they do provide enough information
to determine useful trends. For example, the time to re-acclimate during toluene testing more
than doubles between 1.67 days and 3.73 days non-use test runs (0.46 day vs. 1.0 day). The time
needed to re-acclimate from a two-week (14-day) non-use period is four and half times longer
than that to re-acclimate from 3.73 days non-use test (1.80 days vs. 0.39 days). Even though it
takes longer to re-acclimate from a 2 weeks non-use period, that time is still shorter than the
original acclimation time (1.80 days vs. 4 days).
Data on effects of humidity are even more meager. Only two direct examples of the
: The authors define "re-acclimation" as the time it takes a system to achieve 98 % removal efficiency.
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Experiment
Non-Use Period"
Humidificationb
Toluene0
Benzened
Testl
(days)
Initial
Start-up
No
4.00
7.25
Test 2
(days)
1.67
No
0.46
0.17
Tests
(days)
3.73
No
1.00
0.21
Test 4
(days)
3.73
Yes
0.39
0.21
Tests
(days)
14.0
Yes
1.80
2.75
a The number of days bioreactor was out of service
b "Yes" indicated humidification system was running during non-use period
c Re-acclimation results when only toluene is sent to the bioreactor, days.
d Re-acclimation results when only benzene is sent to bioreactor, days
Table 1. Bioreactor Re-Acclimation Times After Periods of Non-Use (Ref.4)
effects of humidity are given: 3.73-day non-use period tested with and without humidification
using toluene and benzene. In the humidified idle time, the bed re-acclimated to toluene in 0.39
days. In the test without humidification, it took 1 day (61 percent more time). There was no
difference in re-acclimate periods during benzene trials with and without humidity. Both took
0.21 days.
How does this research compare with other re-acclimation investigations? In the authors'
own words, "Thus, other research has found acclimation periods both shorter and longer than
those found in this research. It is difficult to make comparisons among the acclimation periods,
as the different studies involved several different chemicals, [bed packing] media types, and
operating conditions." (Ref.4) In other words, a pilot plant will probably be a necessity to
determine acclimation and re-acclimation periods and other operating parameters for each
emission stream and bed media combination.
BIOREACTOR PROCESSES
From the basic biofilter design, some new processes have evolved to become
environmentally and commercially viable. These new processes address situations not
adequately dealt with in the basic biofilter design such as the large quantity of space required,
acidic environments (pH control), pollutants requiring longer assimilation times, and nutrient
feeding.
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Biofilters
For a brief discussion of the basic design and operation of biofilters see, "Overview".
Biofilters are ideal for treating emission that have low concentrations of contaminates and high
gas volume, a situation that vexes traditional treatment methods. Other advantages and
disadvantages are shown below.
Biofliter Advantages:
Installation costs are low. Most biofilters are constructed from common materials
locally available such as lumber, fiberglass, and plastic pipe. They can be
assembled using carpenters, plumbers, and earthmovers.
• Depending on the amount of pretreatment the emissions require, operating costs
are usually low. These costs consist of electricity to operate the primary blower
and the humidification pump, part-time labor to check on the process, and small
quantities of macronutrients.
Biofilters have high DREs f for certain compounds such as aldehydes, organic
acids, nitrous oxide, sulfur dioxide, and hydrogen sulfide.
Biof liter Disadvantages:
Large land requirement for traditional design.
No continuous internal liquid flow in which to adjust bed pH or to add nutrients.
• Traditional design does not have a covered top, making it difficult to obtain
representative samples of exhaust emission and to determine DREs.
Natural bed media used in biofilters must be replaced every 2 to 5 years. Bed
replacement can take 2 to 6 weeks, depending on bed size.
Over time, some modifications have been developed to overcome some of the specific
deficiencies in the traditional biofilter design. To increase contact time with microbes, some
facilities recycle a portion of the exhaust back through the bioreactor. This is done by adding a
cover and vent to the biofilter. A slipstream is taken from the vent and is recycled back to the
intake of the primary blower. See Figure 2. Also, if land is available, biofilters modules may be
added horizontally, in series. This configuration is shown in Figure 3.
f Destruction/Removal Efficiencies of pollutants
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Contaminated
Air
Emissions Recycle
Vent
Cover
Bed Media
Plenum
Primary
Blower
Water Drain to
Wastewater
Treatment
Figure 2. Biofilter with Emissions Recycle.
t
Biofilter 1
Biofilter 2
Biofilter 3
Figure 3. Biofilters in Series, Horizontally
To reduce land requirement, some operators have stacked biofilter modules vertically.
As mentioned in Factors Affecting Performance, above, some operators have installed soaking
hoses in the bed media to control pH and to add nutrients. Some have added sealed top covers to
keep rain out and heat in. The cover also provides a vent in which to obtain a representative
sample of the exhaust to calculate a more accurate DRE.
One of the earliest modifications was to install the biofilter in the ground, see Figures 4
and 5. This may be done by: digging a hole in the ground the size of the biofilter; placing a
lining of coarse gravel several inches thick on the bottom; installing an emissions distribution
piping system on top of the gravel; covering the piping system with additional few inches gravel;
and covering the gravel with several feet of packing media.
Biofilter Design Characteristics: Allen Boyette (Ref. 6) did research and wrote a paper
on existing biofilters installations presenting design characteristics and cost information a few
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Emissions
Emissions
Soil
Figure 4 In-Ground Biofilter
Figure 5. Photograph of four Biofilters being installed in Arlington, TX
At Central Regional Wastewater System Plant.
years ago.g The information, unfortunately, is for biofilters engaged solely in odor control.
However, it does provide cost information and limited information on Total Reduced Sulfur
(TRS) compounds and one test on VOC. See Table 2. From the information in Table 2, capital
costs for bioreactors per unit volume of emissions (CFM) were calculated, see Table 3.
gThe paper was not dated, but it appears to have been written around 2000.
10
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Facility3
CMCMUA, NJ
CCCSD, CA
DMUA, IA
EHMSW,NY
EWWWTP, NY
HRRSA, VA
HWQD,MA
RWSA, VA
SBC,TN
UNISYN,HI
WLSSD, MN
Odor
Source
Compost
WWTP
Compost
Compost
WWPT
Compost
Compost
Sewage
Compost
Food
Waste
WWPT
Flow
Rate
CFM
2,400
3,500
210,000
50,000
15,000
3,150
15,000
2,825
80,000
2,500
50,000
Filter
Loading
CFM/ft2
4
5
5
5
2.67
4
3.5 to 5
5
4.5
4
4.2
Area
feet2
600
700
42,000
10,000
5,620
790
3,600
565
19,800
625
11,800
Depth
feet
4
4
4
3
4
4
3
4
2.5 to 3
3.5
4
Volume
feet3
2,400
2,800
168,000
30,000
22,480
3,160
10,800
2,260
54,450
2,188
47,200
Residence
Time, Sec.
60
48
48
36
90
48
40-60
48
30-45
42
57
Media
Blend
CYWC, WCd
CYWC, WCd
CYWC, WCd
CYWC, WCd
Unknown
Bio-Solids, WC
CYWC, WCd
CYWC, WCd
NAf
CYWC, WCd
CYWC, WCd
Removal
Eff, %
NT
NP
86 ordor
NP
NTe
NTe
94 Odor
99TRS
76 Odor
91 Odor
93 VOC
82 Odor
99TRS
NAf
Cost"
$K
$49.8
$129.7
$495.5
$135.4
NAf
$58.0
NAf
$14,3
NAf
$11.4
$387.0
" CMCMUS = Cape May County Municipal Utilities Authority, Cape May, NJ
CCCSD = Central Contra Costa Sanitary District, Martinez, CA
DMUA = Davenport Municipal Utilities Authority, Davenport, IA
EHMSW = East Hampton Municipal Solid Waste, East Hampton, NY
EWWTP = Everett Waste Water Treatment Plant, Everett, WA,
HRRSA = Harrisburg/Rockingham Regional Sewer Authority, Mt. Crawford, VA
HWQD = Hoosac Water Quality District, Hoosac, MA
RWSA = Rivanna Water and Sewer Authority, Charlottesville, VA
SBC = Sevierville Bedminister Corp., Sevierville, TN (MSW)
UNISYN = UNISYN Corporation, Wiamanilo, HI (a firm treats food waste)
WLSSD = Western Lake Superior Sanitary District, Duluth, MN
b Total cost of design, construction and start-up. Does not include duct work.
0 Composted yard waste
dWood chips
' Not tested
f Information Not Available
Table 2. Existing Biofilter Design Characteristics Summary (Ref. 6)
11
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Facility Location
Wiamanillo, HI
Charlottesville, VA
Cape May, NJ
Mt. Crawford, VA
Martinez, CA
E. Hampton, NY
Duluth, MN
Davenport, IA
Air Flow
CFM
2,500
2,825
2,400
3,150
3,500
50,000
50,000
210,000
Cost3
$
$11,400
$14,300
$49,800
$58,000
$129,700
$135,400
$387,000
$494,500
Cost per Air Flow
Rate, S/CFM
$4.56
$5.06
$20.75
$18.41
$37.06
$2.71
$7.74
$2.35
a Cost does not include installation of duct work. It does include engineering, construction and start-up cost.
Table 3. Biofilter Cost per Unit Volume of Air Flow
Resulting costs figures are all over the map, but cost per unit volume, appears to decrease
as the airflow increases, as expected. Cost for the three biofilters with capacities of 50,000 CFM
and over, average just $4.24 per cubic foot per minute. This is probably due to economies of
scale. Mr. Boyette does not include ductwork installation cost in his cost figures. In his words,
"The odorous gas collection system for each case is not included in the capital cost as collection
systems vary from simple duct systems to elaborate ducting and controls. The inclusion of
collection system can significantly increase the cost of installing an odor control system and
would be required with any [other] odor control technology selected. "(Ref.2)
As stated earlier in this section, there are many variations to biofilter design that range
from very elaborate equipment and controls to a simple hole in the ground. Other factors
effecting costs are labor cost in the area and the geo-political situation.
BIOTRICKLING FILTER
As mentioned in the Biofilter section, the basic design of a biofilter makes it difficult to
control pH in the packing. Acid is formed with the biological destruction of many pollutants and
acid build-up creates a serious problem for operators. Many of the early biofilters were used to
deodorize foul emissions from wastewater (sewage) treatment facilities. These emissions often
contain sulfur compounds that produce acid upon degradation. Because of the detrimental effect
of acid on microbes, operators began experimenting with processes to control pH that they had
used and understood. One of the processes they experimented with was the trickling filter.
12
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Trickling filters have been used for many years and are effective treatment for wastewater.
What is a Biotrickling filter? It is probably better to answer the question, "What is a
trickling filter?" first, and then describe the modifications that were made to create the
biotrickling filter. A trickling filter is a wastewater treatment process that is usually a round,
vertical tank that contains a support rack and is filled with aggregate, ceramic or plastic media to
a height of 3 to 15 feet. In the middle of the tank is a vertical pipe that has a rotary connection
on the top end. A spray arm is attached to the rotary connection and this has spray nozzles
installed along its length. The spray nozzles are angled slightly off-center to provide force
necessary to rotate the spraying arm around the top of the trickling filter. A recirculating pump
is used to pump liquid from the reservoir in the bottom to the spray nozzles. Liquid level in the
sump is maintained with an automatic effluent make-up system. A biofilm forms on the packing
surface. This is a biologically active mass that removes the pollutants from the effluent and the
microbes decompose them. See Figure 6.
Rotating Spray Arm
Recycled
Effluent
Treated
Effluent
Un-treated
Effluent
Sludge
Discharge
Recirculation
Pump
Figure 6. Trickling Filter
The biotrickling filter is very similar to the trickling filter. However, the pollutants are
contained in an air phase (emissions), and the pollutants must be dissolved into the liquid phase
to be available to the microbes. As the air phase passes through the packing, the pollutants are
absorbed from the air into the liquid phase to achieve maximum contact with the biomass. This
is the difference from the trickling filter because pollutants that enter the system are already in
the liquid phase (effluent) in the trickling filter. Water is added to the reservoir to make-up for
water that has evaporated. Accumulated bio-sludge is periodically removed from the reservoir
13
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and disposed. See Figure 7.
Rotating Spray Head
Emissions
Out
Recycled
Effluent
Packed
Bed
Sludge
Discharge
Recirculation
Pump
Figure 7. Biotrickling Filter
Emissions may be routed through the biotrickling filter co-current or counter-current to
the effluent flow. Because of the continuous flow of a liquid phase, it is an easy matter to
automatically neutralize acid build-up.
Use of ceramic or plastic packing rings achieve a void space of up to 95 percent, which
greatly reduces pressure drop across the packing. This means that 15 feet of plastic packing in a
biotrickling filter will have about the same pressure drop as 3 feet of natural packing in a
biofilter. In other words, the 15 feet of plastic packing is equivalent to a 5 stage biofilter.
Typical characteristics of biofilters found in the United States are shown in Table 4 (Ref 7) .
Design characteristics of four existing biotrickling filters are shown in Table 5 (Ref. 6). The cost
of three of theses biotrickling filters per unit volume of air flow is presented in Table 6.
14
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Height of Bed Packing, ft
Packing Cross-Sectional Area, ft2
Emissions Flow Rate, CFM
Packing Void Volume, % a
Empty Bed Gas Retention Time, Seconds b
Pressure Drop Across Bed, inches H2O
pH of Recycled Liquid Phase
When Treating VOC
When Treating H2S
VOC Concentrations, grains ft3
Removal Efficiency, %
3 to 6
10 to 32,000
600 to 600,000
90 to 95
2 to 60
0.36 to 2
~7pH
1 to 2 pH
4.57 E-3 to 45. 7
60 to 99.9
a Using packing rings, random dump, or structured packing
Empty bed gas retention (EBGR) time is defined as the packed bed volume/emission flow rate
Table 4. General Characteristics of Biotrickling Filters (Ref. 7)
Cost results in Table 6 require an explanation. The Hyperion unit was designed, built
and operated by chemical engineers from the University of California at Riverside. It was
intended to be used as a multi-use research device and was constructed on a moveable trailer.
Because of this, much more flexibility and instrumentation than normally needed was built into
this application. As a result, the cost per volumetric flow rate for this installation was not used in
this comparison.
Costs per flow rates for the remaining two applications are not very far apart and average
$25.10/CFM. This is almost six times as high as $4.25/CFM, the average cost of the three
largest biofilters. This is to be expected, as trickling filter equipment is closer in design to
industrial process equipment than traditional biofilters.
BIOSCRUBBER
Just as the biotrickling filter is an enhancement of the biofilter, the bioscrubber is an
enhancement to the biotrickling filter. The bioscrubber attempts to solve two problems with the
biotrickling filter: 1. improve the absorption of pollutants into the liquid, and 2. lengthen the time
the microbes have to consume the pollutants. These are accomplished in two ways: the tower
packing is flooded with a liquid phase and the discharge effluent from the bioscrubber is
collected in a storage tank (sump) before being recycled back to the bioscrubber. See Figure 8.
15
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Facility a
Hyperion
Grupo
Reemtsma
US Navy
Operation
WWTP
Resins
Tobacco
Fuel Vents
Packing
Stacked
Stacked
Foam
Random
Filter
Dimension
Diameter
5ft
12ft
NA
10ft
Height
lift
38ft
NA
10ft
Flow
CFM
380
26 K
100 K
1,750
EBRT
Seconds
21
10
11
37
AP
inH2O
0.32
1.0
6.0
5.0
Bed Temp
°F
94
92
104
80
Cost
$K
$175
$525
$3,000
NA
Op. Cost
S/MMCFM
$0.23
$0.68
$0.23
$0.72
Eff.
%
98
85-99
90
1 Hypeiona = Hyperion Wastewater Treatment Plant, Los Angeles, CA
Grupo = Grupo Cydsa, Monterey, Mexico (Cellophane)
Reemtsma = Berlin, Germany (Cigarette Production)
US Navy, North Island, San Diego, CA
Table 5. Design Characteristics for Existing Biotrickling Filters (Ref. 7)
Facility
Hyperion WWTP
Grupo
Reentsma
Flow Rate, CFM
380
26,000
100,000
Cost, $
$175 K
$525 K
$ 3,000 K
S/CFM a
$460.00
$20.20
$30.00
a NOTE: Cost per unit volume of air flow (S/CFM) is calculated from data in Table 5.
Table 6. Cost for Biotrickling Filter per Unit Volume of Air Flow
16
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.Clean Air
Full-Cone —
Contaminat
i
Primarv
Demister
^v^vv^
Bed
Media
sd
,x- Bed Suppoi
Liqui
Recy
Nutrier
t JpHCor
— ^
Sump
d Phase
cle
i
ts
itrol
-^r
To Wastewater
Irgaiment
Blower
Sludge
Figure 8. Bioscrubber
Flooding the bed increases the ability of the liquid phase to absorb pollutants because as
the gas phase (emissions) impacts the bed media it forms tiny bubbles that greatly increases the
surface-area of the interface between the gas and liquid phases. Increasing the interface-area
improves the liquid phase's ability to absorb pollutants.
The sump acts as reservoir for the liquid phase and permits additional reaction time for
the microbes to consume pollutants. Reaction times can be increased to an hour or more,
depending on the recirculation rate of the liquid phase and the size of the sump. This increases
the time available for microbes to attach and destroy pollutants. Below are more advantages and
disadvantages of bioscrubbers.
Bioscrubber Advantages:
• It is not necessary to humidify emissions prior to treating them. This could save
the cost of installing a humidification process.
The bioscrubber has a smaller footprint than other bioreactors. This is an
important consideration in congested facilities with limited available real estate.
Because pH control and nutrient feed can be automated, it requires less attention
than other bioreactors.
• Process is ideal for emissions that produce acids upon treatment.
• Bioscrubber can treat emissions containing particulate matter.
17
-------
Bioscrubber Disadvantages:
Considerably more expensive to install than other bioreactors. It has a chemical
scrubber at the heart of the process and resembles chemical-processing equipment
more so than other bioreactors.
Over feeding can cause excessive biomass growth, which can plug the
bioscrubber.
• Operating cost can be higher than other bioreactor processes.
• Needs expensive and complex feeding and neutralizing systems.
• To control biomass growth, toxic and dangerous compounds must be inventoried
and handled.
Operating characteristics and cost data were scarce on the Internet. However, some
information was found for three installations. This information is presented below in Table 7.
Service
Volumetric Flow Rate
Capital Cost (US $)
Inlet Concentration
Outlet Concentration
Cost/Flow Rate (US $)
Roloflex, UK (Ref. 10)
Dryer Exhaust, Printing
Ink Solvents
8,541 CFM
$284,591
500 mg/m3, C
50-100mg/m3, C
$33/CFM
Trinity River Authority (Ref. 11)
1 Stage, WWTP
300 CFM
$50,000
-200 ppm, H2S
1 ppm, H2S
$170/CFM
3 Stage WWTP
1,200 CFM
$275,000
-400 ppm, H2S
Not Detected
$230/CFM
Table 7. Bioscrubber Design Characteristics
Unfortunately, there is insufficient information on Roloflex's web-site to determine why
their bioscrubber installation cost is an order-of-magnitude less, on a flow rate basis, than the
two Trinity River Authority's (TRA) bioscrubber installations. TRA's site did claim they
estimated the cost of a non-proprietary, home designed bioscrubber using lava rocks as packing
media. They claim the vendor's bids were comparable to their estimated cost, and they selected
the vendor's bids. TRA appears to be satisfied with the performance of their two bioscrubbers.
OTHER BIOREACTION TECHNOLOGIES
During the course of this study, other bioreaction technologies were identified. Because
no reference to commercial applications of these technologies was found, no detailed
information is provided on these processes in this report. These technologies are biomembrane
18
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and self-cleaning activated carbon bioreactors.
The biomembrane uses membranes to concentrate pollutants and as a support structure
for a biofilm. However, problems inherent in membrane technology (low flows and high
pressure drop) seem to have inhibited development of this technology's commercial utilization.
The self-cleaning bioadsorber (formally the rotary bioreactor or filter) is a horizontal
cylinder that is constructed of a granulated active carbon (GAC) bed mounted on a shaft that is
supported on both ends. The bed is one third submerged in a trough of water. Microbes are
embedded in the GAC and the bed rotates through the water bath. The bed is enclosed and
emissions enter from one end and exit the other end. In theory, the GAC adsorbs pollutants
from the emission stream and microbes consume pollutants as the bed rotates through the water
bath and emission stream. It is not clear why this technology has not become commercially
viable.
CONTROL OPTIONS AND COST COMPARISONS
Costs of installing and operating emissions control equipment are very important to the
affected facility. In fact, a number of marginal operations have been forced out of business
because the costs of controls made them unprofitable. To avoid this from happening, a facility
must look at all its options to determine which process technologies are viable and what they
cost.
Unfortunately, it is difficult to obtain consistent, reliable and accurate information on
construction and operating costs for existing bioreaction installations. There are a number of
reasons for this. One reason is that bioreaction is an emerging technology and there are not that
many installations in use by process industries. Another reason is that facilities that are using
bioreactors are reluctant to publish installation and operating costs information for competitive
reasons.
Estimates for bioreaction processes are based on bare bones designs. They do not
include any pretreatment such as humidification or particulate matter (PM) removal. These
additional processes may be required. The estimates also assume that the cost of ductwork and
instrumentation were simple and minimal.
Estimates for processes using incineration (thermal and catalytic processes) were
obtained using U.S. EPA's Air Compliance Advisor. Version 7.0. These estimates, under the
best conditions, are plus or minus thirty percent accurate. Unfortunately, the situation presented
here is out of the equation's range (too low) for emissions flow rate. Therefore, the results
obtained may be even more unreliable. The attempt here was to generate order of magnitude
estimates of bioreactor and traditional technologies for comparison purposes.
For head-to-head comparisons, the model plant technique was used. A hypothetical plant
19
-------
and emission stream were used to design and estimate the costs of various viable technologies.
About a decade ago, EPA issued an alternative control technology (ACT) report on the
bread-baking industry (Ref. 11). That report contained nine model bakeries with capacities
ranging from 5,400 to 19,000 tons bread per year. It was decided to use a model bakery
approximately in the middle of this range, 14,000 tons per year.
The following criteria were used for the specifications for the model bakery:
• The baking oven consumes the equivalent of 5 million BTUs of natural gas per
hour.
• Bakery oven operates 24 hours per day, 7 days a week, and 8,000 hours per year.
The bakery only makes white bread from the sponge-dough process.
The oven is direct-fired with natural gas and has only one stack.
• Emissions contain 10 percent moisture, 2,000 parts per million, volume basis
(ppmv) ethanol and 20 ppmv acetaldehyde.
• Emissions from the baking oven average 1,579 actual cubic feet per minute
(ACFM), and are around 375 °F.
A recent state implementation plan (SIP) now requires the bakery to remove and destroy
98 percent of the pollutants in their emissions. To determine which emission control
technologies are viable for controlling emissions from this bakery, available technologies must
be reviewed. Emission control techniques can be divided into two groups: combustion
(incineration) and non-combustion technologies.
Combustion Control Devices
This category relies on heat to burn VOC molecules in the presence of oxygen. Exhaust
from a bakery oven contains insufficient volatile organic material to support combustion. In this
situation, it is necessary to supply additional fuel (usually natural gas) to bring the emissions
temperature up to the level where the pollutants will combust. EPA has found that emissions
exposed to 1,600 °F for at least 0.75 seconds will destroy at least 98 percent of most VOC.
Combustion technologies include thermal oxidation, regenerative oxidation, recuperative
oxidation, catalytic oxidation and flares.
Thermal Oxidation: In this technology, emissions are mixed in the flame of the
supplemental fuel fire and fed into a refractory-lined furnace that contains sufficient volume to
allow the gas mixture to reside for at least 0.75 seconds before being exhausted. This technology
works very well, and this type of incinerator is simple to operate. The problem with this
technology is that it wastes large quantities of energy. Exhaust gases are 1,600 °F and could be
used to preheat the emissions prior to entering the furnace. Because thermal oxidation is such a
wasteful option, it will not be considered in this analysis.
Regenerative Oxidation: This technology uses two vessels to capture some of the waste
heat from the thermal oxidizer. Each vessel is filled with ceramic packing, which is heated in
20
-------
the first vessel with exhaust gases from the thermal oxidizer. When packing in the first vessel is
hot, exhaust gases are switched to the second vessel and bakery oven emissions are routed
through the first vessel to be preheated by the residual heat in the ceramic packing. See Figure 9.
It is possible to recover as much as 70 percent of the waste heat, which reduces fuel cost by 70
percent (Ref. 12).
In Mode A, emissions from the bakery oven are directed through Vessel One and are
heated by the residual heat contained in the ceramic packing. Exhaust gases from the thermal
oxidizer are directed to Vessel Two to heat its packing.
At a predetermined time the flows are switched to Mode B. In sequence, Furnace
exhaust begins heating the packing in Vessel One, and the residual heat in Vessel Two heats the
Oven emissions. In both Modes, additional natural gas is burned in the thermal oxidizer furnace
to keep its temperature above 1,600 °F. Regenerative Thermal Oxidizer is a viable option for the
treatment of the bakery oven's emissions.
sions
^-
Vessel One
Vessel Two
Furnace
i
m
_ Natural
MODE A
Oven Emission being heated in One
and Furnace Exhaust being cooled in Two
To "*
Atmosphere
/en
Vessel One
Vessel Two
Furnace
J
Natural
Gas
MODEB
Oven Emission being heated in Two
and Furnace Exhaust being cooled in One
Figure 9 Regenerative Thermal Oxidizer Operating Modes
Recuperative Thermal Oxidizer: This technology has somewhat similar to a
Regenerative Thermal Oxidizer. They both recover and use waste heat, but in a different way.
In a Recuperative Thermal Oxidizer, emissions from the oven flow through the tube side of a
shell and tube heat exchanger, and exhaust from the thermal oxidizer is routed through the shell
side. Heat is transported from the hot oxidizer exhaust to the cooler oven emissions. See Figure
10.
21
-------
Oven
Exhaust
t
To
Amosphere
Phase I
n
Phase I
Phase I
Preheated
Three-Phase Recuperative
Heat Exchanger
Oven Exhaust
Thermal
Oxidizer Exhaust
Thermal Oxidizer
Figure 10. Three-Phase Recuperative Thermal Oxidizer
The Recuperative Thermal Oxidizer is a viable option for treating bakery oven exhaust.
Catalytic Oxidation: This technology uses metals that act as catalyst to facilitate the
reaction between oxygen and the pollutants so the oxidation reaction takes place at a much lower
temperature than the thermal oxidation temperature. Typically, catalyst assisted reactions take
place in the range of 600 to 1,200 °F, instead of the 1,600 °F required by thermal oxidation. As a
result, significant fuel savings can be realized by using a catalyst assisted control device. See
Figure 11.
To
Atmosphere
Oven
Catalysis Bed
Economizer
Catalytic Oxidizer
Pre-Heated Oven Emissions
Natural Gas
Figure 11. Catalytic Oxidizer
Disadvantages of using catalyst include higher capital cost. A precious metal catalyst can
cost as high as $600 to $800 a cubic foot. Also, the use of catalyst requires an extremely clean
emissions stream that is low in paniculate matter. Particulate matter can coat catalyst surfaces,
reducing their effectiveness. Catalytic oxidation is a viable option for treating bakery oven
22
-------
emissions and is the preferred choice of bakeries with controls on their ovens (Ref. 11).
Non-Combustion Control Devices
Carbon Adsorption: This technology uses vessels filled with granulated activated
carbon (GAC) to adsorb pollutants onto their surfaces. With continuous operations, at least two
vessels are required. When the first units GAC becomes saturated with pollutants, emissions
must be directed to the second unit while the first unit is re-generated. Re-generation is the
process of removing the pollutants from the GAC and restoring it to capacity. This is usually
done with steam and/or heat. The pollutants are not destroyed in the carbon adsorption process,
they are just transferred to another phase. Ethanol, the primary pollutant in bakery oven
emissions, has a high affinity for carbon and is difficult to remove from the GAC beds. Because
of this problem, carbon adsorption is not considered a viable option in this situation.
Chemical Scrubbers: This technology uses a column packed with ceramic or plastic
rings and is flooded with a liquid phase. The pollutants in the emissions are absorbed by the
liquid and the contaminated liquid requires additional treatment. The pollutants are not
destroyed by the scrubbing process, but report to the liquid phase creating another pollution
problem. Because of this, chemical scrubbing alternative is not an option in this situation.
Condensation:. Condensation of ethanol from bakery emissions would require
refrigerated cooled coils. Because of the low temperatures required, water, fat and oils would
also condense from the emissions. Water would freeze to the coils and the fats and oils would
foul them, inhibit heat transfer and reduce the effectiveness of the condenser. This process
would also create large volumes of wastewater that require additional treatment. This technology
is not considered a viable option.
Process/Formulation Changes: This alternative is not considered an option. All
modified yeast products that lower VOC emissions produce products that have unacceptable
taste.
Bioreaction: During the last decade, significant advances have been made in various
biological processes. More facilities are evaluating various bioreaction processes as viable
options to traditional technologies. Because of large land requirements, biofilters may not be an
option. Other options that are potentially viable are biotrickling filter and bioscrubbers.
Cost Comparisons
Costs of thermal and catalytic destruction of the pollutants emitted from the bakery oven
were calculated using EPA's Air Compliance Advisor. Cost assumptions and emissions stream
data can be found in Appendix A. These costs are shown in Table 8, below.
23
-------
Process
Recuperative
Regenerative
Catalytic
Total
Capital
Cost, $
$227,375
$60,100
$44,100
Annual
Utilities3
Costs, $
$6,300
$2,680
$2,970
Other Direct
Costs", $
$25,700
$26,800
$28,700
Indirect
Costs0, $
$24,760
$18,830
$18,600
Total
Annual
Costs, $
$52,300
$48,257
$50,270
a Annual Utilities Costs include electrical and natural gas costs.
Other Direct Costs include labor, maintenance, supervision and capital recovery.
c Indirect Costs include overhead, insurance, taxes and capital recovery.
Table 8. Estimated Control Cost for Thermal and Catalytic Processes
The estimates range from $48,257 for the regenerative technology to $52,300 for the
recuperative process. Total costs are often expressed as cost per thousand cubic feet treated.
Annual emissions are 758 million cubic feet per year, which results in a control cost of $0.064
per cubic foot when using the regenerative technology.
Bioreaction control costs were estimated from values found in literature and on the
Internet (Ref. 8). Cost elements are shown in Table 9, below.
Total annual cost estimates for bioreaction processes have a much wider range than
estimates for incineration controls. Annual cost estimate for bioreaction processes ranged from
$5,225 for a biofilter, and $54,144 for a bioscrubber. The biofilter's costs in dollars per CFM is
$0.0069 per CFM, which is an order of magnitude less than regenerative incineration
technology. Bioscrubber total annual costs are comparable to the annual costs of the incineration
processes. Thus, it has no financial advantage over thermal technologies.
REGULATORY ISSUES
Very little information was found on how bioreactors are regulated or permitted. One
paint producer that installed a bioreactor system on the west coast was contacted to determine
how they permitted their installation. The environmental manager there said that facility was
granted a pilot plant type permit that allowed them to experiment to determine optimum DRE
and operating conditions. The initial bioreactor installed was later determined to be undersized
and was replaced with a unit thirty percent larger. They are pleased with the new installation,
which they say easily exceeds the vendor guaranty of 75 percent DRE. They are confident they
will eventually achieve 85 to 90 percent DRE. He now feels they can easily qualify as a
24
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Process
Biofilter
Biotrickling
Filter
Bioscrubber
Total
Costs, $
$8,560a
$42,800e
$337,900f
Laborb, $
$1,780
$1,780
$3,420
Nutrients
$640
$640
$1,284
Bed
Cleanings0,
$
$1,605
$1,605
$2,140
Indirect
Costs", $
$1,200
$6,000
$47,300
Total
Annual
Costs, $
$5,225
$10,025
$54,144
a Estimated based on $5 per CFM and a flow rate of 1,579 CFM + CPI adjustment to January 2003.
Includes operations, maintenance and supervision.
c Two per year.
Includes overhead, taxes, insurance and capital recovery.
e $25 per CFM + CPI.
f $200 per CFM + CPI.
Table 9. Control Costs Using Bioreaction
"synthetic minor" designation under new source review permitting procedures instead of a
"major source" designation.
CONCLUSIONS
EPA promulgated a new MACT standard for miscellaneous organic processes in late
summer of 2003. These new regulations will subject over 25 new organic source categories to
MACT standards. A number of smaller operators will now have to meet new emissions
standards. Plant engineers will be scratching their collective heads trying to determine what
must be done and how much it will cost to meet these new standards. A bioreactor system may
be the answer to their prayers. However, this may be a difficult road to go down, and much
research must be done before final decisions are made.
Like many other control technologies, bioreaction works in many cases, but not all. The
trick is knowing when it will work and when it won't. This involves research, testing and talking
to knowledgeable people with experience building and running bioreactors. Your first question
should be: Is bioreaction applicable for my emission stream? If emissions are very acidic or
basic, they must be neutralized before entering a bioreactor. If not at or near 100 percent relative
humidity, they must be humidified if planning to use a biofilter. If the emission stream is too hot
or too cold, it must be cooled or heated. If its too dirty (particulate matter), the emission stream
should be cleaned before going into a biofilter (suspended solids are not a problem in
biotrickling filters or bioscrubbers). If emissions are very concentrated or extremely toxic, they
are probably not suitable for bioreaction.
25
-------
If the emission stream is suitable, or can be pretreated to be suitable, which bioreactor
technology is a right? This answer depends on the characteristics of the emission stream. If the
emission stream contains pollutants that generate acids upon degradation (sulfur compounds or
halogens), a biotrickling filter or bioscrubber may be the correct choice. If emissions do not
generate acids, and space is available, a biofilter may be the answer. If a high DRE is required, a
bioscrubber may be required. However, as shown in the cost section of this report, if a
bioscrubber is required, the high capital cost of a bioscrubber may offset by lower fuel cost when
comparing it to thermal processes. In addition, the environmental advantages of not producing
additional NOx or CO still apply. If a facility is near an emission limit or a threshold for either
of these pollutant, this may be significant.
Yes, bioreaction is a viable, low cost option in some circumstances, for the facilities that
have emissions that qualify for this technology.
26
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REFERENCES
1. Q. Zhang et al, "Odor Production, Evaluation and Control", Department of Biosystems
Engineering, University of Manitoba, October 2002.
2. J. E Burgess, S. A. Parsons, and R. M. Stuetz, "Developments in Odor Control and Waste Gas
Treatment", School of Water Science, Cranfield University, Bedfordshire, UK.
3. Peter L. Voigt; "Biofiltation for Odor and VOC Control"; Clean TeQ Publication,
Dandeneng, Victoria, Australia, 3175.
4. Joseph S. Devinny, "Clearing the Air Biologically", Civil Engineering Magazine. September
1998, pp. 46-49.
5. F. Jason Martin, Rust Environmental, and Raymond C. Loehr, Professor University of Texas,
Austin, "Effects of Periods of Non-Use on Biofilter Performance", Journal of the Air and Waste
Management Association, Vol. 46, pp. 534-554.
6. R. Allen Boyette, PE, "Biofiltration Economics and Performance", E & A Consultants, Gary,
NC, ~ 2000.
7. Marc A. Deshesses and Huub H. J. Cox, "Biotrickling Filter Air Pollution Control",
Department of Chemical & Environmental Engineering, University of California, Riverside, C A,
~ 2000.
8. Huub H. J. Cox and Marc A. Deshusses, "Waste Gas Treatment in Biotrickling Filter",
Chapter 4, University of California, Riverside, CA.
9. Bio-Wise, Company Publication, "Biological System Reduces VOC Emissions", Bio-Wise,
P.O. Box 83, Didcot, Oxfordshire, OX11 OBR, Web Site: www.dti.gov.uybiowise.
10. Mark A. Perkins, PE, William R. Tatem, and James S McMillen, EIT; "Milti-Faceted Odor
Control Program Controls Costs and get results at a Large Regional Wastewater Treatment
Plant"; Trinity River (Texas) Authority; and Alan Plummer and Associates, Inc.
11. C. Wally Sanford, Alternative Control Technology for Bakery Oven Emissions, U.S. EPA
Report Nos. 453/R-92-017, OAQPS, U.S. EPA, December 1992.
12. Air Compliance Advisor, U.S. EPA, OAQPS/ISEG, 2000.
27
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APPENDIX A
CONTROL DEVICE OPERATING
COST ASSUMPTIONS
Interest Rate %
Operating Labor Pay Rate $/hr
Maintenance Labor Rate, $/hr
Electrical Cost, $/kW-hr
Natural Gas Cost, $/M3
Cooling Water Cost, $/M3
Water Disposal Cost, $/M3
Steam Cost, $/kg
Dust Disposal Cost, $/kg
Yearly Operating Hours
Duty Cycle
7%
$16.73
$18.41
$0.06
$0.15
$0.05653
$1.007
$0.01097
$0.02949
8,000 hr
Continuous Operation
Emission Stream Data
Oven Exhaust Temperature, °R
Pressure, Atmospheres
Volumetric Rate - Actual M3/sec
Pollutant: Ethanol, ppmv
Pollutant: Acetaldehyde, ppmv
258.9
1
0.3806
2000
20
28
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TECHNICAL REPORT DATA
(Please read Instructions on reverse before completing)
1. REPORT NO.
EPA-456/R-03-003
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Using Bioreactors to Control Air Pollution
• . REPORT DATE
September 2003
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
Clean Air Technology Center (E 143-03)
Information Transfer and Program Integration Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Office of Air Quality Planning and Standards
Office of Air and Radiation
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Final
14. SPONSORING AGENCY CODE
EPA/200/04
15. SUPPLEMENTARY NOTES
For more information, call the Clean Air Technology Center (CATC) Information Line at (919) 541-0800 or access the CATC
Web page at .
16. ABSTRACT
Because of increasing fuel cost and tightening environmental regulations, alternative air pollution control technologies are
being considered to replace or supplement expensive combustion control technologies. This technical bulletin addresses one
of these technologies, bioreactors. Bioreactors use micro-organisms to destroy pollutants in air emission streams. Using
publicly available data, this report: presents information on commercially available bioreaction processes used to control air
pollution; considers the limitations of bioreactors; assesses the effectiveness of bioreactors for removing pollutants; and
provides information on the capital and operating costs of bioreactors.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Bioreaction
Bioreactor
Biofilter
Trickling Biofilter
Bioscrubber
Air Pollution Control
Volatile Organic Compounds
VOC
Odor Control
Organic Hazardous Air Pollutants
Organic HAP
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Report)
Unclassified
21. NO. OF PAGES
28
20. SECURITY CLASS (Page)
Unclassified
EPA Form 2220-1 (Rev. 4-77)
PREVIOUS EDITION IS OBSOLETE
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United States Office of Air Quality Planning and Standards Publication No. EPA-456/R-03-003
Environmental Protection Information Transfer and Program Integration Division September 2003
Agency Research Triangle Park, NC
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