EPA-450/3-75-054
October 1974
EMISSION FACTOR
DEVELOPMENT FOR THE FEED
AND GRAIN INDUSTRY
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air ami Wasle Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/3-75-054
EMISSION FACTOR
DEVELOPMENT FOR THE FEED
AND GRAIN INDUSTRY
by
P. G. Gorman, M. Schrag, and E. Trompeter
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
Contract No. 68-02-1324
Task No. 22
EPA Project Officer: Thomas F. Lahre
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
October 1974
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors
and grantees, and nonprofit organizations - as supplies permit - from
the Air Pollution Technical Information Center, Environmental Protection
Agency, Research Triangle Park, North Carolina 27711; or, for a fee,
from the National Technical Information Service, 5285 Port Royal.
Road, Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency
by Midwest Research Institute, Kansas City, Missouri 64110, in
fulfillment of Contract No. 68-02-1324. The contents of this report
are reproduced herein as received from Midwest Research Institute.
The opinions, findings, and conclusions expressed are those of the
author and not necessarily those of the Environmental Protection Agency
Mention of company or product names is not to be considered as an
endorsement by the Environmental Protection Agency.
Publication No. EPA-450/3-75-054
11
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ABSTRACT
This report contains an evaluation of available data used to develop
emission factors for alfalfa dehydration plants, grain elevators and
other feed and grain operations.
ill
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CONTENTS
List of Figures . vi
List of Tables „ vi
Acknowledgements, , vii
Sections
I Introduction 1
II Alfalfa Dehydration Plants ........ 2
Emission Factors 2
Background and Support Information for Emission
Factors for Alfalfa Dehydration Plants 7
III Feed and Grain Mills and Elevators 12
Emission Factors 12
Background and Support Information for Emission
Factors for Feed and Grain Mills and Elevators 22
Appendix A - Emission Factors for Grain Dryers at
Grain Elevators 33
Appendix B - Derivation of Emission Factors For Grain Processing
Operations 35
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LIST OF FIGURES
No.
Page
1 Generalized Flow Diagram for Alfalfa Dehydration
Plant. . . 3
LIST OF TABLES
No. Page
1 Particulate Emission Factor Data for Alfalfa
Dehydration Plant Equipment 5
2 Total Emission Factor for Alfalfa Dehydration Plant 5
3 Comparison of Alfalfa Dehydration Plant Emission Factor •
Data o 8
4 Particulate Emission Factors for Grain Elevators 14
5 Particulate Emission Factors for Grain Elevators Based
on Amount of Grain Received or Shipped 15
6 Particulate Emission Factors for Grain Processing
Operations 17
7 Particulate Emission Factors for Grain Elevators 24
8 Best Average Value of Long-Term Composite Emission
Factors 25
9 Particulate Emissions from Grain Handling and Processing ... 25
10 Particulate Emission Factors for Grain Elevators Based on
Amount of Grain Received or Shipped. 26
11 Average Values Used for Ratio of Tons Processed to Tons
Shipped or Received • . 27
12 Particulate Emission Factors for Grain Processing
Operations 29
A-l Summary of Available Emission Factor Data for Grain
Dryers . 34
VI
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ACKNOWLEDGEMENTS
This report was prepared for EPA under Contract No. 68-02-1324. The
work was performed under the direction of Dr. L. J. Shannon, Head,
Environmental Systems Section, Physical Sciences Division. The report
was written by Mr. Paul G." Gorman with assistance from Mr. M. Schrag
and Mr. Ed Trompeter.
Approved for:
H. M. Hubbar , Director
Physical Sciences Divisidn
28 October 1974
VI1
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INTRODUCTION
The work in this report was performed by MRI for EPA as Task Order No. 22
on Contract No. 68-02-1324. The objective of this work was to develop
emission factors for the feed and grain industry by examination and
evaluation of available data. Results of that effort are described in
this report, which is divided into two sections of two parts each. The
major sections are titled
Alfalfa Dehydration Plants
Feed and Grain Plants
The first part of each major section summarizes the emission factors
that were developed, describes the processes and describes control
methods while the second part of each section presents background
and support information for those emission factors.
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ALFALFA DEHYDRATION PLANTS
EMISSION FACTORS
General
The dehydration of alfalfa for the production of alfalfa meal is the
primary objective of an alfalfa dehydration plant. Dehydrated alfalfa
is important for its protein quality, unidentified growth and repro-
ductive factors, pigmenting xanthophylls, and vitamin contributions.
The process carried out at most dehydration plants is essentially that
shown in Figure 1. Standing alfalfa is mowed and chopped in the field a
and is transported by truck to the dehydrating plant which is located
near the field (usually within 10 miles). The truck dumps the chopped
alfalfa onto a self feeder which carries it into a drying drum. The
drying drum, a direct-fired rotary unit, subjects the alfalfa to high
temperature combustion gases (approximately 1800°F at the inlet and
275°F at the outlet) and evaporates the water from about 77% 1^0 in green
chops down to 8% 1^0 in dry chops. From the drying drum, the high
moisture gases and dry chops enter the primary cyclone which separates
the product from the gases. The material separated in the primary
cyclone next enters the grinding machine, normally a hammerraill, which
reduces the dehydrated chops to a powder referred to as "meal." The
meal enters a pneumatic conveyor that discharges into a meal collection
cyclone which separates the meal from the conveying air. The collected
meal is then usually fed to a pelletizing.machine. Product meal or
pellets may be stored prior to shipment or they may be loaded out
directly from the process.
Emissions and Controls
Emissions from alfalfa dehydrating plants are indicated in Figure 1 and
include dust from the primary cyclone, meal collector cyclone, pellet
collector cyclone and pellet cooler. Although these sources are common
to many plants there are several process variations in which secondary
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Note:
Sccondory cyclone collector*
may rx>t be u*ed and in tome
coiei trie cyclone «ff!u«r>M
•nay be ducted bock to the
primary cycio^e -
Fr«h Cut
Alfalfa (Green Chop*)
from tH« Field
leveling
kh
i
Dryer Ofum
r'H" I'I
Cooler I 1
Cyclone
Seconoai
Meal
Collectof
Figure 1. Generalized flow diagram for alfalfa dehydration plant.
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cyclones may or may not be used, (e.g., some sources ducted to a common
secondary cyclone, or some sources are ducted back to the primary cyclone,
etc.). A number of tests have been conducted to measure emissions from
alfalfa dehydration plants and included plants that employ some of process
variations described above. Results of that testing are summarized in
Table 1.
Data shown in Table 1 were obtained from actual source tests at alfalfa
dehydration plants. These data, as well as discussions with plant
operators and others knowledgeable in the field, have led to the con-
clusion that the greatest portion of the particulate emissions comes
from the drying operation, i.e\, the primary cyclone. From this same
information it is estimated that the total plant emission factor for an
alfalfa dehydration facility would be about 20 Ib/ton of product (meal
or pellets) as shown in Table 2. However, much of the data used in
arriving at this figure was based on testing at plants which reportedly
were well "tuned" prior to testing or in some cases operated below
capacity.—' It is therefore possible that the emission factor of 20 Ib/ton
may be below the industry average and an individual plant could be emit-
ting considerably more than 20 Ib/ton of product.
In the past, control of emissions has been directed to the meal collector
cyclone, etc., because of the difficulties involved in controlling the
high moisture content effluent from the primary cyclone. These sources
have primarily been controlled with cyclones but some plants have installed
fabric filters. More recently there has been a concentrated effort by
the American Dehydrators Association and individual plants to investigate
control methods for the effluent from the primary cyclone. Most of the
devices that have been investigated, and full-scale units that have been
installed on a few plants, consisted of some type of low-pressure drop
wet scrubber. References Nos. 1, 2, and 3 contain descriptions and cost
information for some of these control methods.
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Table 1. PARTICULATE EMISSION FACTOR DATA FOR
ALFALFA DEHYDRATION PLANT EQUIPMENT
Emission sources Lb/ton of product Kg/MT of product
Primary cyclone 14.22^7 7. Ill/
(Dryer only)
Primary cyclone 15.02^ 7.5I-/
(Dryer only)
Primary cyclone 14.28£/ 7.14^/
(Dryer and Hammermill)
Primary cyclone 17.46-/ 8.73i/
(Dryer and all other sources)
Meal collection cyclone 2.61L/ 1.3—
Pellet cooler cyclone 3.2—' 1.6—
Pellet regrind cyclone0-/ 8.0^ 4.0-'
a/ Reference No. 1.
b_/ Reference No. 2.
b/ Pellet regrind is a special operation that is not normally a
part of the processing operation.
Table 2. TOTAL EMISSION FACTOR FOR ALFALFA DEHYDRATION PLANT
Type of operation Lb/ton of product-/ Kg/MT of product^./
Total emissions from
uncontrolled plant 20.0-' 10.0
a/ Product consists of meal and/or pellets.
b/ Reference No. 2.
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References
1. Smith, K. D., "Particulate Emissions from AlfaIfa'Dryers - The
Effectiveness and Cost of Control," Interim Report, American
Dehydrators Association, Prepared for Environmental Protection
Agency (Grant No. R801446), April 1973.
2. Shannon, L. J., R. W. Gerstle, P. G. Gorman, D. M. Epp, T. W. Devitt,
and R. Araick, "Emissions Control in the Grain and Feed Industry
Volume I - Engineering and Cost Study," Final Report by Midwest
Research Institute, Prepared for Environmental Protection Agency
Document No. EPA 450/3-73-003a, December 1973.
3. Smith, K. D., "Particulate Emissions from Alfalfa Dehydrating Plants
Control Costs and Effectiveness," Final Report by American Dehy-
.drators Association, Prepared for Environmental Protection Agency,
Document No. EPA-650/2-74-007, January 1974.
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BACKGROUND AND SUPPORT INFORMATION FOR EMISSION FACTORS FOR ALFALFA
DEHYDRATION PLANTS
Air Pollution Emission Rate from Alfalfa Dehydrators
Emissions from alfalfa dehydrating plants include dust from the various
cyclone separators, and odors from the volatile matter driven off the
alfalfa.
In comparison to the other segments of the grain and feed industry, a
significant amount of source testing has been done to characterize the
emissions from dehydration plants.ii±/ Midwest Research Institute has
recently completed two source testing programs for the American Dehydratore
Association (ADA). References 1 and 2 present the results of the testing
programs in detail and a summary is given in the following paragraphs.
Reference 1 describes the field testing program conducted by MRI for the
ADA during the Summer of 1971, at four plants which had been selected
by ADA as representative of this industry. Particulate emissions and
process conditions were measured at the four alfalfa dehydrating mills
for both normal and extreme process operating conditions.
Source tests were performed to determine the particulate emission rate
from a given source. The emission-rate test consisted of the measure-
ment of effluent flowrate and temperature, dust loading, and carrier
gas composition (moisture and Orsat analysis). For these measurements,
EPA Method 5 and the Research Appliance Company Model 2343 "Staksaraplr"
equipment were used. Integrated particulate samples representative of
the entire duct cross-section were collected by sampling for equal
amounts of time over a network of properly distributed points. For
each test the duration of sampling range from 30 to 60 rain so that short-
terra fluctuations in emissions were averaged out.
Process parameters were measured during testing. These parameters have
been classified into three groups: (1) raw materials, (2) product
(pellets), and (3) process operating conditions relating to drying,
grinding and pelleting of the alfalfa. These quantities were measured
periodically during testing.
A comparison of available emission factor data, for the particulate
sources in the dehydrating process, is shown in Table 3. There are
considerable differences in the data from the different information
sources. The emission factors for the primary cyclone (which include
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Table 3. COMPARISON OF ALFALFA DEHYDRATION PLANT EMISSION
FACTOR DATA (lb/ton)£/
Ref. 1
4.4
6.5
Avg.4.65
Primary cyclone
Ref. 2
3.03^
4.99
1.72
1.42
3.12
Avg. 2.86
Ref. 3
2.25
3.25
Avg. 2.75
Ref. 4
4.8—
1.2
Secondary cooling cyclone
Ref. 4
1.25
0.72
Avg. 1.0
Pellet cooler cyclone
Ref. 1
0.65
0.53S/
Ref. 4
0.25
1.5
Avg. 0.8
Avg. 2.0
Meal collection cyclone(s)
Ref. 1 Ref. 4
0.65 2.25
12.0
Avg. 7.1
Pellet regrind
Ref. 1
2.0
Ref. 4
0.5
a/ All emission data expressed as pounds per ton of green chops. This
may be converted to pounds per ton of meal by the following approxi-
mate relationship:— (Ib/ton of chops) x (4) *» Ib/ton of meal.
b_/ Includes discharge from meal collector cyclone and pellet cooler cyclone.
£/ AH sources ducted to primary cyclone.
d/ Includes discharge from meal collector cyclone.
e/ Sura of pellet collector and pellet cooler cyclone discharges.
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other significant sources in some cases) are highest for the data in
Reference 1, and show a range of 2.6 to 6.5 Ib/ton chops and an average
of 4.65 Ib/ton of chops. However, emissions from the. other sources are
lower in Reference 1 than Reference 3, especially from the meal collection
cyclone. These variations may be due to differences in control equip-
ment, measurement techniques or plant operating conditions. Data in
'Reference 1, for emissions from the meal collector, were taken at the
outlet of the secondary cyclone that is in series with the primary
cyclone which should help to reduce the emissions. The emissions from
the primary cyclone reported in References 1 and 2 also include, in
some cases, the effluents from other sources that are ducted to the
primary cyclone. This could add to the effluent from the primary cyclone,
but the total emissions may be less than they would be if the effluent
from other sources were allowed to vent to atmosphere.
Although the data reported in References 1 and 2 represent relatively
well controlled plants, the measurement techniques are significantly
different than those used in References 3 and 4. Measurements in
References 1 and 2 were according to EPA Method 5 and included duct
extensions for the cyclone outlets. At least part of the sampling
reported in Reference 3 was performed right at the cyclone outlet which
makes it difficult to obtain accurate results. While differences in
the emission factors may be partly caused by the type of primary cyclone
and the measurement techniques, it is also known that emissions from
these plants can vary widely due to quality of the alfalfa (moisture
and protein content) and operating conditions (over drying or under
drying, etc.).
Examination of the available data plus many plant visits and discussions
with plant operators and others knowledgeable in the field have led to
the conclusion that the greatest portion of the dust emission from an
alfalfa dehydrating plant comes from the drying operation (i.e., the
primary cyclone). The data in Table 3 show that the average emission
factor for the primary cyclone varies from 2.0 to 4.65 Ib/ton of chops.
The data reported in References 1 and 2 were obtained using EPA Method
5 procedures so these are probably the most accurate value available.
The average of these two values (2.86 and 4.65) indicate that the over-
all average would be 3.75 Ib/ton of green chops. This is approximately
equivalent to 15.0 Ib/ton of meal,— which is much lower than the
emission factor of 60 Ib/ton of meal specified in Reference 6. The
factor in Reference 6 was apparently based on data from Reference 3.
These data were obtained prior to 1960, using techniques that are
probably not as accurate as the recent EPA procedures. It is therefore
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felt that the emission factor of 15 Ib/ton of meal is more representative
for the primary cyclone and that the total plant emission factor probably
does not exceed 20 Ib/ton of meal. More complete information on test
data and evaluation of results is contained in Reference 5.
10
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References
1. Smith, K.D., "Particulate Emissions from Alfalfa Dryers - The Effec-
tiveness and Cost of Control," Interim Report, American Dehydrators
Association, Prepared for Environmental Protection Agency (Grant
No. R801446), April 1973.
2. Cowherd, C., "Particulate Emissions and Process Conditions at
Representative Alfalfa Dehydrating Mills," Final Report, Midwest
Research Institute, Prepared for American Dehydrators Association,
19 November 1971.
3. "Air Pollution from Alfalfa Dehydrating Mills," USDHEW Technical
Report A60-4 (1960).
4. Private Communication, Mr. Kenneth Smith, American Dehydrators
Association, September 1969.
5. Shannon, L. J., et al., "Emissions Control in the Grain and Feed
Industry Volume I - Engineering and Cost Study," Final Report by
Midwest Research Institute for EPA under Contract No. 68-02-0213
(EPA Publication 450/3-73-003a), December 1973.
6. Compilation of Air Pollutant Emission Factors, EPA Publication
AP-42, February 1972.
11
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FEED AND GRAIN MILLS AND ELEVATORS
EMISSION FACTORS
General
Grain elevators are transfer and storage areas for grain and are usually
classified as either country, terminal, or export elevators. Country
elevators generally receive grains as they are harvested 'from fields
within a 10- to 20-mile radius of the elevator. The country elevators
unload, weigh and store grain as it is received from the farmer. In
addition, the country elevator may dry or clean the grain before it is
shipped to the terminal elevators or processors.
Terminal elevators receive most of their grain from country elevators
and ship to processors, other terminals, and exporters. The primary
function of a terminal elevator is to store grain in quantity without
deterioration and to bring it to commercial grade so as to conform to
the needs of buyers. As with country elevators, terminals dry, clean and
sort grain. In addition, they can blend grain to meet buyer specifi-
cations.
Export elevators are similar to terminal elevators with the exception
that they mainly load grain on ships for export.
The other types of operations involved in the processing of grain, in
grain and feed plants, range from very simple mixing steps to complex
processes which are characteristic of industrial processing plants.
Included are such diverse processes as: (a) simple mixing processes
in feed mills; (b) grain milling in flour mills; (c) solvent extracting
in soybean processing plants; and (d) a complex series of processing
steps in a corn wet-milling plant.
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Emissions and Controls
Grain handling, milling and processing include a variety of operations
from the initial receipt of the grain at either a country or terminal
elevator to the delivery of a finished product. Flour, livestock feed,
soybean oil and corn syrup are among the products produced from plants
in the grain and feed industry. Emissions from the feed and grain industry
can be separated into two general areas, those occurring at grain elevators
and those occurring at grain processing operations.
Grain Elevators - Grain elevator emissions can occur from many different
operations in the elevator including unloading (receiving), loading (ship-
ping) , drying, cleaning, headhouse (legs), tunnel belt, and trippers, etc.
Emissions factors for these operations at terminal, country and export
elevators are presented in Table 4. The emission factors for unloading
operations are assumed to be from trucks for country elevators and trucks
and railroad cars for terminal and export elevators. Emission factors for
removal of grain from the storage bins (i.e., tunnel belt drop-points) were
based on a study done at a terminal elevator.1.' The headhouse (legs)
emission factor is also based on the terminal elevator study.-=•' Drying
and cleaning emission factors are based mainly on data reported in
References 1, 2, and 3.
The emission factors shown in Table 4 represent the amount of dust
generated per ton of grain processed through each of the designated
operations (i.e., uncontrolled emission factors). Amounts of grain
processed through each of these operations in a given elevator is de-
pendent on such factors as the amount of grain turned (interbin trans-
fer), amount dryed, and amount cleaned, etc. Because the amount of grain pas-
sing through each operation is of ten difficult to determine,it may be more
useful to express the emission factors in terras of the amount of grain
shipped or received, assuming these amounts are about the same over the
long terra. Emission factors from Table 4 have been modified accordingly
and are shown in Table 5 along with the appropriate multiplier that was
used as representative of typical ratios of- throughput at each operation
to the amount of grain shipped or received. This ratio is an approximate
value based on average values for turning, cleaning, and drying in each
type of elevator. However, operating practices in individual elevators
are different, so these ratios, like the basic emission factors them-
selves, would be more valid for a group of elevators rather than individual
elevators.
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Table 4. PARTICULATE EMISSION FACTORS FOR
GRAIN ELEVATORS!:!/
Type of source
Emission factor (uncontrolled)£/
(Ib/ton) (kg/MT)
Terminal of elevators
Unloaded (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Dryingk/
Cleaning
Headhouse (legs)
Tripper (gallery belt)
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Drying^/
Cleaning
Headhouse (legs)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying^/
Cleaning
Headhouse (legs)
Tripper (gallery belts)
1.00
0.27
.40
.05
.00
.50
1.00
0.64
0.27
1.40
0.68
6.00
1.50
00
00
40
05
6.00
1.50
1.00
0.50
0.14
0.70
0.52
3.00
0.75
0.50
0.32
0.13
0.70
0.34
3.00
0.75
0.50
0.50
0.70
0.52
3.00
0.75
0.50
a_/ Emission factors are in terras of pounds of dust emitted per ton
of grain processed by each source.
b/ Emission factors for drying are based on 1.8 Ib/ton for rack
dryers and 0.3 Ib/ton for column dryers prorated on the basis
of distribution of these two types of dryers in each elevator
category, as discussed in Reference 3.
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Table 5. PARTICULATE EMISSION FACTORS FOR GRAIN ELEVATORS BASED ON
AMOUNT OF GRAIN RECEIVED OR SHIPPED*/
Type of Source
Terminal Elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying-'
Cleaning
Headhouse (legs)
Tripper (gallery belt)
Country Elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Drying^/
Cleaning
Headhouse (legs)
Export Elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying^/
Cleaning
Headhouse (legs)
- Tripper (gallery belt)
Emission Factor
Ib/ton processed
1.00
0.27
1.40
1.05
6.00
1.50
1.00
0.64
0.27
1.40
0.68
6.00
1.50
1.00
1.00
1.40
1.05
6.00
1.50
1.00
Typical Ratio of Tons Processed
to Tons Received or Shipped—
1.00
1.00
2.03
0.10
0.22
3.03
1.71
1.00
1.00
2.08
0.25
0.08
3.08
1.00
1.00
1.23
0.01
0.15
2.23
1.07
Emission Factor
Ib/ton received or shipped
1.00
0.27
2.84
0.11
1.32
4.55
1.71
0.64
0.27
2.91
0.17
0.48
4.62
1.00
1.00
1.72
0.01
0.90
3.35
1.07
.§' Assumed that over the long term the amount received is approximately equal to amount shipped.
]>/ See note l>/ in Table 4.
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In this same regard, the factors in Tables 4 or 5 should not be added to-
gether in an attempt to obtain a single emission factor value for grain
elevators because in most elevators some of the operations are equipped
with control devices and some are not. Therefore, any estimation of
emissions must be directed to each operation and its associated control
device, rather than the elevator as a whole, unless the purpose was to
estimate total potential (i.e., uncontrolled) emissions. An example
of the use of emission factors in making an emission inventory is con-
tained in Reference 3.
Some of the operations listed in the tables, such as the tunnel belt
and tripper, are internal or in-house dust sources which, if uncontrolled,
might show lower than expected atmospheric emissions because of internal
settling of dust. On the other hand, the reduction in emissions via
internal settling is not known and it is quite possible that all of this
dust is eventually emitted due to subsequent external operations, internal
ventilation or other means.
As mentioned above, many elevators utilize control devices on at least
some sources. In the past, cyclones have commonly been applied to such
sources as legs in the headhouse and tunnel belt hooding systems. More
recently, fabric filters have been utilized at many elevators on almost
all types of sources. However, some sources in grain elevators do present
control problems. Control of loadout operations is one source that is
difficult to control because of the problem of containment of the emis-
sions. Probably the most difficult source to control, because of the
large flowrate and high moisture content of the exhaust gases, is the
dryers. Screen-houses or continuously vacuumed screen systems are avail-
able for reducing dryer emissions and have been applied at several
facilities. Detailed descriptions of dust control systems for grain
elevator operations, and their estimated costs, are contained in Reference
2.
Grain Processing Operations - Grain processing operations include many of
the operations performed in a grain elevator in addition to milling and
processing of the grain. Emission factors for different grain milling
and processing operations are presented in Table 6. . Brief discussion of
these different operations and the methods used for arriving at the emis-
sion factor values shown in Table 6 are presented below.
16
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Table 6. PARTICULATE EMISSION FACTORS FOR
GRAIN PROCESSING OPERATIONS
Type of source
Feed Mills
Emission factora.c/
(uncontrolled except where indicated)
(Ib/ton) (kg/MT)
Receiving
Shipping
Handling
Grinding
Pellet coolers
1.30
0.50
3.00
0.65
0.25
1.50
Wheat Mills
Receiving
Precleaning and handling
Cleaning house
Millhouse
1.00
5.00
70.00
0.50
2.50
35.00
Durum Mills
Receiving
Precleaning and handling
Cleaning house
Millhouse
1.00
5.00
0.50
2.50
Rye Milling
Receiving
Precleaning and handling
Cleaning house
Millhouse
1.00
5.00
70.00
0.50
2.50
35.00
Dry Corn Milling
Receiving
Drying
Precleaning
Cleaning house
Degerming and milling
1.00
0.50
5.00
6.00
0.50
0.25
2.50
3.00
b/
Emission factors are expressed in terms of pounds of dust emitted per ton
of grain entering the plant (i.e., received), which is not necessarily
the same as the amount of material processed by each operation.
Controlled emission factors.
£' --Blanks indicate insufficient information.
17
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Table 6. (Concluded)
Emission factor£i£/
(uncontrolled except where indicated)
Type of source (Ib/ton) (kg/MT)
Oat Milling
Total 2-50b/ 1.25*/
Rice Milling
Receiving 0.64 °'32
Handling and precleaning 5.00 2<3°
Drying
Cleaning and millhouse
Soybean Mills
1.60 0.80
Handling 5.00 2.50
Receiving
Handling
Cleaning
Drying 7.20 3.60
Cracking and dehulling 3-30 1>65
Hull grinding 2.00 1.00
Bean conditioning °'10 °'05
Flaking O-57 °'29
Meal dryer i-50 °-75
Meal cooler 1-80 °'90
Bulk loading °-27 °'14
Corn Wet Milling
Receiving ^ °'50
Handling 5.00 2.50
Cleaning 6.00 3.00
Dryers
Bulk loading
18
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Emission factor data for feed mill operations are sparse. This is partly
due to the fact that many ingredients; whole grain and other dusty materials
(bran, dehy alfalfa, etc.) are received by both truck and rail and several
unloading methods are employed. However, some operations (handling, ship-
ping, >and receiving) for a feed mill are similar to operations in a grain
elevator, so an emission factor for each of these different operations
was estimated on this basis. The remaining operations were estimated
from the best information available.—'
Three emission areas for wheat mill processing operations are grain re-
ceiving and handling, cleaning house, and milling operations. Data from
a grain elevator study!/ were used to estimate emission factors for grain
receiving and handling. Data for the cleaning house were insufficient
to estimate an emission factor and information taken from Reference 2
was used to estimate the emission factor for milling operations. The
large emission factor for the milling operation is somewhat misleading
because almost all of the sources involved are equipped with control
devices to prevent product losses and fabric filters are widely used
for this purpose.
Operations for durum mills and rye milling are similar to those of wheat
milling. Therefore, most of these emission factors are equal to those
for wheat mill operations.
The grain unloading, handling and cleaning operations for dry corn milling
are similar to those in other grain mills but the subsequent operations
are somewhat different. Also, some drying of corn received at the mill
may be necessary prior to storage. An estimate of the emission factor for
drying was obtained from Reference 2. Insufficient information was avail-
able to estimate emission factors for degerming and milling.
Information necessary to estimate emissions from oat milling was unavail-
able. It was also felt to be unwise to attempt to use emission factor
data for other grains because handling of oats is reported to be dustier
than many other grains. The only emissions factor data that were avail-
able were for controlled emissions. ~J An overall controlled emission
factor of 2.5 Ib/ton was calculated from this data.
Emission factors for rice milling were based on those for similar opera-
tions in other grain handling facilities. Insufficient information was
available to estimate emission factors for drying, cleaning and mill
house operations.
19
-------
Information taken from Reference 2 was used to estimate emission factors
for soybean mills.
Information on corn wet-milling emission factors was unavailable in most
cases due to the wide variety of products and the diversity of operations.
Receiving, handling and cleaning operations emission factors were assumed
to be similar to those for dry corn milling.
Many of the operations performed in grain milling and processing plants
are the same as those in grain elevators, so the control methods are
similar. As in the case of grain elevators, these plants often use
cyclones or fabric filters to control emissions from the grain handling
operations (e.g., unloading, legs, cleaners, etc.). These same devices
are also often used to control emissions from other processing operations
and a good example of this is the extensive use of fabric filters in
flour mills. However, there are also certain sources within some milling
operations that are not amenable to use of these devices. Therefore,
wet scrubbers have found some application, particularly where the effluent
gas stream has high moisture content. Certain other sources have been
found to be especially difficult to control, and one of these is the
rotary dryers in wet corn mills. Descriptions of the emission control
systems that have been applied to sources within the grain milling and
processing industries are contained in Reference 2.
20
-------
References
1. Gorman, P. G., "Potential Dust Emission From a Gra-in Elevator In
Kansas City, Missouri," Final Report, prepared for Environmental
Protection Agency, May 1974.
2. Shannon, L. J., R. W. Gerstle, P. G. Gorman, D. M. Epp, T. W. Devitt,
and R. Anick, "Emission Control In the Grain and Feed Industry
Volume I - Engineering and Cost Study," Final Report by Midwest
Research Institute prepared Lor Environmental Protection Agency,
Document No. EPA-450/3-73-003a, December 1973.
3. Shannon, L. J., P. G. Gorman, M. P. Schrag, D. Wallace, "Emission
Control in the Grain and Feed Industry Volume II - Emission
Inventory," Final Report by Midwest Research Institute prepared
for Environmental Protection Agency, July 1974.
21
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BACKGROUND AND SUPPORT INFORMATION FOR EMISSION FACTORS FOR FEED AND
GRAIN MILLS AND ELEVATORS
General
Grain elevators are transfer and storage areas for grain and are usually
classified as either country, terminal or export elevators. Country
elevators generally receive grain or soybeans as they are harvested from
fields within a 10- to 20-mile radius of the elevator. The country elevators
unload, weigh and store grain as it is received from the farmer. In
addition, the country elevator may dry or clean the grain before it is
shipped to the terminal elevators or processors.
Terminal elevators receive most of their grain from country elevators
and ship to processors, other terminals, and exporters. The primary
function of a terminal elevator is to store grain in quantity without
deterioration and to bring it to commercial grade so as to conform to
the needs of buyers. As with country elevators, terminals dry, clean
and store grain. In addition, they can blend grain to meet buyer
specificat ions.
Export elevators are similar to terminal elevators with the exception
that they mainly load grain oh ships for export.
The other types of operations involved in the processing of grain in
grain and feed plants range from very simple mixing steps to complex
processes which are characteristic of industrial processing plants.
Included are such diverse processes as: (a) simple mixing processes
in feed mills; (b) grain milling in flour mills; (c) solvent extracting
in soybean processing plants; and (d) a complex series of processing
steps in a corn wet-milling plant.
Emissions and Controls
Grain handling, milling, and processing include a variety of operations
from the initial receipt of the grain at either a country or terminal
elevator to the delivery of a finished product. Flour, livestock feed,
soybean oil and corn syrup are among the products produced from plants
in the grain and feed industry. Emissions from the feed and grain
industry can be separated into .two general areas, those occurring at
grain elevators and those occurring at grain processing operations.
22
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Grain Elevators - Grain elevator emissions can occur from many different
operations in the elevator, including unloading (receiving), loading
(shipping), drying, cleaning, headhouse (legs), tunnel belt, and trip-
pers (primarily for terminal and export elevators). Emissions factors
for several of these operations are presented in Table 7.
Emissions factors for unloading operations are assumed to be from trucks
for country elevators and trucks and railroad cars for terminal and
export elevators. Emission factors for removal of grain from storage
bins were based on a study done on a terminal elevator— and considered
the fact that grain is often turned at a country elevator by returning
it into the receiving pit. The headhouse (legs) emission factor is also
based on the terminal elevator study.±J Drying and cleaning emission
factors are based mainly on data collected from a feed and grain study2»3/
and the previously mentioned elevator study.—'
The emission factors shown in Table 7 represent the amount of dust
generated per ton of grain processed through each of the designated
operations (i.e., uncontrolled emission factors). Amounts of grain pro-
cessed through each of these operations in a given elevator are dependant
on such factors as the amount of grain turned (interbin transfer),
amount dryed, and amount cleaned, etc. Because the amount of grain pas-
sing through each operation is often difficult to determine, it may be
more useful to express the emission factors in terms of the amount of
grain shipped or received, assuming these amounts are about the same
over the long term. Emission factors from Table 7 have been modified
accordingly and are shown in Table 10 along with the appropriate rauliti-
plier that was used as representative of typical ratios of throughput
at each operation to the amount of grain shipped or recieved. This ratio
is an approximate value based on average values for turning, cleaning,
and drying in each type of elevator, as explained in Table 11. However,
operating practices in individual elevators are different, so these
ratios, like the basic emission factors themselves, would be more valid
for a group of elevators rather than individual elevators.
In this same regard, the factors given in the tables should not be added
together in an attempt to obtain a single emission factor value for grain
elevators because in most elevators some of the operations are equipped
with control devices and some are not. Therefore, any estimation of
emissions must be directed to each operation and its associated control
device, rather than to the elevator as a whole, unless the purpose was to
estimate total potential (i.e., uncontrolled) emissions. An example
of the use of emission factors in making an emission inventory is con-
tained in Reference 3.
23
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Table 7. PARTICULATE EMISSION FACTORS FOR GRAIN ELEVATORS
S3
Type of source'
Terminal elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying
Cleaning
Headhouse (legs)
Tripper (gallery 'belt)
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bine (tunnel belt)
Drying
Cleaning
Headhouse (legs)
Export elevators^'
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying
Cleaning
Headhouse (legs)
Tripper (gallery belt)
0.27^
6.00^
Emission factors^
(uncontrolled)
Ob/ton) (kg/MT)
0.50
0.14
0.70
0.52
3.00
0.75
0.50
0.32
0.13
0.70
0.34
3.00
0.75
0.50
0.50
0.70
0.52
3.00
0.75
0.50
°-27k/
0.68—
1.50-/
1.00
1.00E/
1.40
1.05
6.00
1.50
1.00
a/ Emission factors are in terns of pounds of dust emitted per ton of grain processed
by each source.
b/ Emission factor of 1.00 Ib/ton for unloading is based on Kansas City elevator
study.—/ Table 8 shows the values for truck, unloading (0.64) and car unloading
(1.30). These data are supported by data in Table 9 taken from Reference 2.
c/ The emission factor for loading was taken from the Kansas City elevator studyi'
which shows a value of 0.27 Ib/ton for car loading (Table 8). Emission factor
. • for truck loading was not determined but is not expected to be significantly
different.
d/ Emission factor of 1.40 Ib/ton is based on tunnel belt emission factor of 1.40
determined in the Kansas City elevator study (Table 8).i/-
e_l Emission factor of 1.05 Ib/ton for drying was based on dryer emissions, discussed
in Appendix A, of 0.3 Ib/ton for column dryers and 1.8 for rack dryers. Other
survey data indicate ratio of column to rack dryers at terminal elevators la about
1:1, so an average emission factor of 1.05 Ib/ton was used.
f/ An emission factor of 6.00 Ib/ton for cleaning is based on the Kansas City elevator
studyi'' which showed a value of 5.78 Ib/ton (for corn) In Table 8.
g/ An emission factor for 1.5 Ib/ton for the headhouse is from the Kansas City elevator
studyi'' and Is shown by Table 8. This value Includes garner and scale.
h/ The emission factor for the tripper, of 1.00 Ib/ton, Is an estimate based on factors
for other sources and observations of tripper emissions.
_!/ The emission factor of 0.64 Ib/ton for truck unloading was taken from the Kansas
City elevator study (Table 8)i/. This is lower than data In Table 9 and previous
editions of AP-42 but is based on quantitative results that are considered to be
more accurate than those on which the higher values have been based. It Is
possible, however, that emission factors for country elevators could be higher
than similar operations at a terminal elevator because .of field dust, etc., but
definitive test results for country elevators are not available.
J/ An emission factor for loading of 0.27 Ib/ton at country elevators la the same as
that for terminal elevators (see note 1).
k/ An emission factor of 1.40 Ib/ton for turning la based on expected similarity to
the tunnel belt emission factor determined In the Kansas City elevator study
(Table 8).-i/
_!/ Emission factor of 0.68 Ib/ton for drying at country elevators is discussed in
Appendix A, which showed 0.3 Ib/ton for column dryers and 1.8 Ib/ton for rack
dryers. Survey data indicated that 757. of dryers at country elevators were
column type so an emission factor of 0.68 Ib/ton was used.
m/ An emission factor of 6.00 Ib/ton for cleaning is based on the Kansas City terminal
elevator study!/ which showed an emission factor to be 5.78 Ib/ton. A very low
emission factor of 0.43 Ib/ton for a cleaner was reported by a study performed in
North Dakota. However, It Is not known if this cleaner operated with air aspiration
and It Is doubtful that this low value Is representative of cleaning operations.
n/ The emission factor of 1.50 Ib/ton for headhouse (legs) Is based on the assumption
that it will be approximately the same as the value of 1.49 Ib/ton determined in
the Kansas City elevator study (Table 8).!/
o/ Emission factors for all sources are assumed to be Che some as for terminal elevators
except ship loading.
£/ An emission factor of 1.0 Ib/con for ship loading is based on one test on ship loading
as a port elevator in Seattle (EPA Emission Test Kcport 73-CKN-Sl".
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Table 8. BEST AVERAGE VALUE OF LONG-TERM
COMPOSITE EMISSION FACTORS (LB/TON)!/
Emission factor
Operation (Ib/ton of grain processed)
Truck unloading 0.64
Car unloading 1.30
Car loading 0.27
Corn cleaner 5.78
Gallery belt 0.11
Tunnel belt 1.40
Headhouse 1.49
Table 9. PARTICIPATE EMISSIONS FROM GRAIN
HANDLING AND. PROCESSING-/
(Ib/ton of grain processed)
Lb/ton Range of emissions
Emission source Processed (Ib/ton)
Terminal Elevators
Shipping or receiving
Rail 1 (1-3)
Truck 1.4 (0.8 - 3.5)
Barge 1.2 (1 - 3.5)
Transferring, conveying, etc. 2.0 (2 - 2.5)
Screening and cleaning 5.0 (5 - 7)
Drying 5.5 (4 - 8)
Country Elevators
Shipping or receiving
Rail 4 (3-8)
Truck 4.5 (2 - 8)
Barge 5.5 (3 - 8)
Transferring, conveying, etc. 3.5 (2 - 4)
Screening and cleaning 8.5 (7 - 10)
Drying 7.5 (4-8)
25
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Table 10. PARTICULATE EMISSION FACTORS FOR GRAIN ELEVATORS
BASED ON AMOUNT OF GRAIN RECEIVED OR SHIPPED^
Emission Factor „ Typical ratio of Tons Processed
Type of Source
Terminal Elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying
Cleaning
Headhouse (legs)
Tripper (gallery belt)
Country Elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Drying
Cleaning
Headhouse (legs)
Export Elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying
Cleaning
Headhouse (legs)
Tripper (gallery belt)
Ib/ton processed to Tons Received or Shippedf-tE'
1.00
0.27
1.40
1.05
6.00
1.50
1.00
0.64
0.27
1.40
0.68
6.00
1.50
1.00
1.00
1.40
1.05
6.00
1.50
1.00
1.00
1.00
2.03
0.10
0.22
3.03
1.71
1.00
1.00
2.08
0.25
0.08
3.08
1.00
1.00
1.23
0.01
0.15
2.23
1.07
Emission Factor
Ib/ton received or shipped
1.00
0.27
2.84
0.11
1.32
4.55
1.71
0.64
0.27
2.91
0.17
0.48
4.62
1.00
1.00
1.72
0.01
0.90
3.35
1.07
&J Assumed that over the long term the amount received is approximately equal to amount shipped.
b/ See Table 11 for explanation of ratios used.
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Table 11. AVERAGE VALUES USED FOR RATIO OF TONS
PROCESSED TO TONS SHIPPED OR RECEIVED
Ratio of Grain Throughput to Grain Received or Shipped
for basic, elevator functions listed below^'
Emission Sources
Terminal Elevators
Unloading
Loading
Removal from bins
Drying
Cleaning
Headhouse
Tripper
Country Elevators
Unloading
Loading
Removal from bins
Drying
Cleaning
Headhouse
Export Elevators
Unloading
Loading
Removal from bins
Drying
Cleaning
Headhouse
Tripper
Unloading Loading Turning Drying
1.00
1.00
1.00 + 0.71 + 0.10
0.10
1.00 + 1.00 + 0.71 + 0.10
1.00 + 0.71
1.00
1.00
1.00 + 0.75 + 0.25
0.25
1.00 + 1.00 + 0.75 + 0.25
1.00
1.00
1.00 + 0.07 + 0.01
0.01
1.00 + 1.00 + 0.07 + 0.01
1.00 + 0.07
Cleaning
+ 0.22
0.22
+ 0.22
+ 0.08
0.08
+ 0.08
+ 0.15
0.15
+ 0.15
To tall/
1.00
1.00
2.03
0.10
0.22
3.03
1.71
1.00
1.00
2.08
0.25
0.08
3.08
1.00
1.00
1.23
0.01
0.15
2.23
1.07
SL> Values derived from information and data in Reference 3.
- "Total" represents the overall average ratio of grain throughput to grain received or shipped for each
emission source due to all basic elevator functions which involve that source.
-------
Some of the operations listed in the tables, such as the tunnel belt
and tripper, are internal or in-house dust sources which, if uncontrol-
led, might show lower than expected atmospheric emissions because of
internal settling of dust. On the other hand, the reduction in emissions
via internal settling is not known and it is quite possible that all of
this dust is eventually emitted due to subsequent external operations,
internal ventilation or other means.
As mentioned above, many elevators utilize control devices on at least
some sources. In the past, cyclones have commonly been applied to such
sources as legs in the headhouse and tunnel belt hooding systems. More
recently, fabric filters have been utilized at many elevators on almost
all sources. However, some sources in grain elevators do present control
problems. Control of load-out operation is one of the more difficult
sources to control because of the problem of containment of the emissions.
Probably the most difficult source to control, because of the large flow-
rate and high moisture content of the exhaust gases, is the dryers.
Screen houses or continuously vacuumed screen systems are available for
reducing dryer emissions arid have been applied at several facilities.
Detailed description of dust control systems for grain elevator operations,
and their estimated costs, are contained in Reference 2.
Grain Processing Operations - Grain processing operations include many
of the operations performed in a grain elevator in addition to milling
and processing of the grain. Emission factors for different grain rail-
ling and processing operations are presented in Table 12. Brief dis-
cussion of these different operations and the methods used for arriving
at the emission factor values shown in Table 12 are presented below.
More detailed discussion and derivation of the emission factors shown
in Table 12 are presented in Appendix B.
Emission factor data for feed mill operations are sparse. This is partly
due to the fact that many ingredients; whojgrain and other dusty materials
(bran, dehy alfalfa, etc.) are received by both truck and rail and several
unloading methods are employed. However, some operations (handling, ship-
ping and receiving) for a feed mill are similar to operations in a grain
elevator, so an emission factor for each of these different operations
was estimated on this basis. The remaining operations were estimated
from the best information available.—
Three emission areas for wheat mill processing operations are grain re-
ceiving and handling, cleaning house, and milling operations. Data from
a grain elevator studyJL' were used to estimate emission factors for grain
receiving and handling. Data for the cleaning house were insufficient
28
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Table 12. PARTICULATE EMISSION FACTORS FOR
GRAIN PROCESSING OPERATIONS*/
Emission factorsa»b,d/
(uncontrolled except where indicated)
Type of source (Ib/ton) (kg/MT)
Feed Mills
Receiving 1.30 0.65
Shipping 0.50 0.25
Handling 3.00 1.50
Grinding 0.10£/
Pellet coolers O.lOf/
Wheat Mills
Receiving 1.00 0.50
Precleaning and handling 5.00 2.50
Cleaning house
Millhouse 70.00 35.00
Durum Mills
Receiving 1.00 0.50
Precleaning and handling 5.00 2.50
Cleaning house
Millhouse
Rye Milling
Receiving 1.00 0.50
Precleaning and handling 5.00 2.50
Cleaning house
Millhouse 70.00 35.00
Dry Corn Milling
Receiving 1.00 0.50
Drying 0.50 0.25
Precleaning 5.00 2.50
Cleaning house 6.00 3.00
Degerming and milling
SJ See Appendix B.
—' Emission factors are expressed in terms of pounds of dust emitted per ton
of grain entering the plant (i.e.,'received), which is not necessarily
the same as the amount of material processed by each operation.
£/ Controlled emission factor.
^' Blanks indicate insufficient information.
29
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Table 12. (Concluded)
Emission factors a,c/
(uncontrolled except where indicated)
Type of source (jib/ton) (kg/MT)
Oat Milling
Total 2.50S/ 1.25-7
Rice Milling
Receiving 0.64 0.32
Handling and prccleaning 5.00 2.50
Drying
Cleaning and millhouse
Soybean Mills
Receiving 1.60 0.80
Handling 5.00 2.50
Cleaning
Drying 7.20 3.60
Cracking and dehulling 3.30 1.65
Hull grinding 2.00 1.00
Bean conditioning 0.10 0.05
Flaking 0.57 0.29
Meal dryer 1.50 0.75
Meal cooler 1.80 0.90
Bulk loading 0.27 0.14
Corn Wet Milling
Receiving 1.00 0.50
Handling 5.00 2.50
Cleaning 6.00 3.00
Dryers
Bulk loading
30
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to estimate an emission factor and information taken from Reference 2
was used to estimate the emission factor for milling operations. The
large emission factor for the milling operations is somewhat misleading
because almost all of the sources involved are equipped with control
devices to prevent product losses and fabric filters are widely used
for this purpose.
Operations for durum mills and rye milling are similar to those of
wheat milling. Therefore, most of these emission factors are equal to
those for wheat mill operations.
The grain unloading, handling and cleaning operations for dry corn
milling are similar to those in other grain mills but the subsequent
operations are somewhat different. Also, some drying of corn received
at the mill may be necessary prior to storage. An estimate of the
emission factor for drying was obtained from Reference 2. Insufficient
information was available to estimate emission factors for degerming
and milling.
Information necessary to estimate emissions from oat milling was unavail-
able. It was also felt to be unwise to attempt to use emission factor
data for other grains because handling of oats is reported to be dustier
than many other grains. The only emissions factor data that were avail-
able were for controlled emissions.—' An overall controlled emission
factor of 2.5 Ib/ton was calculated from this data.
Emission factors for rice milling were based on those for similar operations
in other grain handling facilities. Insufficient information was avail-
able to estimate emission factors for drying, cleaning and mill house
operations.
Information taken from Reference 2 was used to estimate emission factors
for soybean mills.
Information on corn wet milling emission factors was unavailable in most
cases due to the wide variety of products and the diversity of operations.
Receiving, handling and cleaning operations emission factors were assumed
to be similar to those for dry corn milling.
31
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References
1. Gorman, P. G., "Potential Dust Emission From a Gra'in Elevator In
Kansas City, Missouri," Final Report, prepared for Environmental
Protection Agency, May 1974.
2. Shannon, L. J., R. W. Gerstle, P. G. Gorman, D. M. Epp, T. W. Devitt,
and R. Anick, "Emission Control In the Grain and Feed Industry
Volume I - Engineering and Cost Study," Final Report by Midwest
Research Institute prepared for Environmental Protection Agency,
Document No. EPA-450/3-73-003a, December 1973.
3. Shannon, L.- J., P. G. Gorman, M. P. Schrag, D. Wallace, "Emission
Control in the Grain and Feed Industry Volume II - Emission
Inventory," Final Report by Midwest Research Institute prepared
for Environmental Protection Agency, July 1974.
32
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APPENDIX A
EMISSION FACTORS FOR GRAIN DRYERS AT GRAIN ELEVATORS
GRAIN DRYER EMISSION FACTORS
A quantitative assessment.of emissions from grain dryers is difficult,
primarily because of lack of available data. However, these data and
other information have indicated that the emission rate from any given
installation is dependent upon the dryer configuration, i.e., rack or
column; the type of grain being processed, i.e., |corn, soybeans, wheat;
the foreign material present in the incoming grain, i.e., dust, chaff,
"beeswing" hulls, etc.; and the amount of moisture removed which af-
fects throughput.
The large volumes of air passed through the grain, the large cross-
sectional area through which the air is exhausted and the wide par-
ticle size distribution of the effluent contribute to sampling dif-
ficulties. The absence of an acceptable test method makes comparisons
between reported dryer emission tests highly uncertain.
A compilation of the available data on emissions test for rack and column
type dryers is presented in Table A-l and, based on these data, average
values for the uncontrolled emission factors were selected:
Rack Dryers - 1.8 Ib/ton
Column Dryers - 0.3 Ib/ton
Because of the small amount of available data, spread in these data,in-
adequate information regarding specific test methods, use of different
sampling trains, and the lack of complete information regarding foreign
material and moisture differential, these emission factors should only
be considered as indicative of possible average emissions and not ab-
solute numbers for individual dryers.
33
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Table A-l. SUMMARY OF AVAILABLE EMISSION FACTOR DATA
FOR GRAIN DRYERS (UNCONTROLLED)
Rack
Throughput
(bu/hr)
1,000
2,000
500
1,500
1,800
dryers
Emission factor
(Ib/ton)
3.7S/
2.3S/
i.zfe/
0.9*'
•*•»«•*•"
Avg. =1.8 Ib/ton
Column dryers
Throughput
(bu/hr)
400
1,000
3,000
Avg
Emission factor
(Ib/ton)
0.23i/
0.21^
"*°
. = 0.3 Ib/ton
§_/ Reference 2.
b/ Private communication.
34
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APPENDIX B
DERIVATION OF EMISSION FACTORS FOR GRAIN PROCESSING
OPERATIONS (as shown in Table 12)
FEED MILLS
Receiving
As stated in Reference 2 (p. 159) the ingredient receiving area repre-
sents the most serious dust emission problem in most feed mills. Emis-
sion factor data for this operation are sparse, owing partly to the fact
that many ingredients; whole grain and other more dusty materials (bran,
dehy alfalfa, etc.), are received, by both truck and rail and several
unloading methods are employed. For these reasons, an average emission
factor would be difficult to determine, at least as far as whole
grains are concerned, so an emission factor for the unloading operation
only has been estimated as 1.30 Ib/ton. This was the value determined
in the Kansas City elevator study!/ for car unloading and may be re-
presentative of feed mills and hopefully reflects the fact that some
ingredients tend to be more dusty than whole grains.
Shipping
Most feed mills ship the bulk feed by truck, but some are also shipped in
bags by rail and truck. Reference 2 (p. 166) states that loadout is a
major source of dust emissions but little emission factor data are avail-
able. An emission factor of 0.27 Ib/ton was determined for car loading
of grain in the Kansas City elevator study. —' It is assumed that bulk
loading of feed mill products would tend to be no re dusty than whole
grain loading. Therefore, an emission factor of 0.5 Ib/ton has been
estimated for this operation.
Handling Operations (transfer points, garner and scale, legs)
No data were available for the internal handling operations in feed
mills. However, it would be expected that they are somewhat similar to
35
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those In grain elevators. The Kansas City elevator study—' showed that
the most significant of these operations was the legs, having an emis-
sion factor of 1.49 Ib/ton. The tunnel belt factor of 1.40 Ib/ton is
similar but feed mill operations are such that this may not be a com-
parable operation.. However, all material in a feed mill would be ex-
pected to pass through a leg at least twice from unloading to shipping.
Therefore, an overall average emission factor for feed mill handling
operations has been estimated as 3.0 Ib/ton.
Grinding
Whole grains received at feed mills must be ground and the associated
product recovery cyclone is the major dust source in this grain prep-
aration operation. Because of the wide variation in grains and
grinders used, an average emission factor would be difficult to deter-
mine. A small amount of data presented in Reference 2 (p. 163) in-
dicated that controlled emissions may range from 0.02 to 0.2 Ib/ton.
Considering these facts, and lack of other data, an average controlled
emission factor of 0.1 Ib/ton has been estimated, assuming it is to be
representative of the Industry as a whole.
Pellet Coolers
The only available emission factor data for this operation was contained
in Reference 2 (pp. 164-167) and indicated that the uncontrolled emis-
sion factor was quite high (5 to 50 Ib/ton) but that the cyclones were
very efficient (92 to 99.9%). The data on p. 164 show considerable dif-
ference in controlled emission factors for horizontal coolers and column
coolers. Distribution of these two types of coolers within the industry
is not known but our observations indicate that column coolers are quite
common. For this reason, a controlled emission factor of 0.1 Ib/ton
has been estimated.
WHEAT MILLS
Processing operations were discussed in Reference 2 (p. 207) and identi-
fied three emission areas: grain receiving and handling, cleaning
house, and milling operations. Emission factors and calculation of
emissions for sources within each of these operations is discussed be-
low.
Receiving
It would be expected that receiving of wheat would be similar in emissions
to that for terminal grain elevators (0.64 and 1.30 Ib/ton). —' Data on
36
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p. 182 of Reference 2 for one flour mill presents controlled emission
factors for fabric filters but it is difficult to use these data in
estimating an uncontrolled factor. Therefore, the data from Reference 1
had to be used, and an average factor of 1.0 Ib/ton was selected for
receiving by trucks, cars and barges.
Freeleaning and Handling
Very little data on uncontrolled emissions from precleaning were avail-
able, but it is assumed to consist primarily of scalping type operations,
which should be a minor source in comparison with handling operations.
Handling consists of legs, transfer points, garner and scale and tripper,
etc. Usable data on uncontrolled emission factors for these sources in
flour mills were lacking, so the data from Reference 1 had to be used,
even though it was for a grain elevator and did not include a tripper.
However, it did include a tunnel belt and it is also known that in a
flour mill the grain would pass through the leg twice (once when re-
ceived and once when transferred to cleaning house). Therefore, a
cumulative emission factor of 5.0 Ib/ton was estimated for all pre-
cleaning and handling operations.
Cleaning House
Cleaning is accomplished by a variety of means but often includes air
aspiration to remove lighter impurities (dust) as well as disc separators
and scourers. Each of these can be a source of dust emissions but only
a small amount of emission data on cyclone controlled sources were avail-
able in Reference 2 (p. 210). Therefore, it was not feasible to cal-
culate an emission factor for the cleaning house.
Mill House
Operations in the mill house are complex, and again, very little emission
data are available. Reference 2 (p. 209) cites one report which indicated
that dust generated in roller mills may average 2.1 Ib/bu (70 Ib/ton).
This source and the purifiers might therefore account for more than 70
Ib/ton. This emission factor is larger than the one for precleaning and
handling and may be erroneously high but it was the only data available.
It should be noted that because of the product value these emissions
are controlled, primarily with fabric filters.
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DURUM MILLS
The sources of air pollution in a durum mill parallel those of a flour
mill and fall into the three main categories of receiving and handling
operations, cleaning-house, and milling operations. Rate of emission
for durum mill operations are limited but since the processing operations
are similar to those of a flour mill, the rates are expected to be
similar (Reference 2, p. 215). However, in the mill section one of the
primary purposes is to produce middlings rather than flour so the break
rolls are different. Because of this, it is assumed that the emission
factor of 70 Ib/ton used for the mill house in flour mills may not be
applicable to durum mills. Therefore, the same emission factors for
flour mills were assumed to apply, but the emission factor for milling
operations was not estimated.
RYE MILLING
The milling procedure for rye consists of the same processing steps as
wheat milling (Reference 2, p. 221) and air pollution sources parallel
those in a wheat mill. Very little emission factor data were available
for rye milling. Some data on certain milling operations (Reference 2,
p. 226) indicate a controlled emission factor of about 1 Ib/ton. This
is equivalent to an uncontrolled emission factor of 10 Ib/ton, assuming
cyclone efficiencies of 90%. However, these data do not include break
rolls and other operations so the factor of 70 Ib/ton used for wheat
milling was assumed to be applicable to rye. This factor, and the
others for wheat milling were assumed to be the same for rye milling.
DRY CORN MILLING
The .grain unloading, handling, and cleaning operations are similar to
those in other grain mills but the subsequent operations are somewhat
different (Reference 2, p. 216). Very little emission factor data were
available for dry corn milling, except for some controlled emission
factors tabulated in Reference 2 (pp. 222, 223).
Receiving
As in the case of flour mills, an average emission factor of 1.00 Ib/ton
has been used for the receiving operation.
Some drying of corn received at the mill may be necessary prior to storage.
Types of dryers used (rack or column) is not known, but about 50% use the
38
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Day-Vac" system. For this reason, an emission factor of 0.5 Ib/ton was
used based on .dryer emission factors discussed in Appendix A.
Precleaning and Handling
As explained in the section on flour mills, an average emission factor
of 5.0 Ib/ton was used for the precleaning and handling operations.
Cleaning House
An emission factor of 5.78 Ib/ton was determined for a grain elevator
corn cleaning operation.!./ Also, Reference 2 (p. 222) shows an emis-
sion factor of 0.0015 Ib/bu (0.06 Ib/ton) for a cleaning house control-
led by a fabric filter. If the FF were 99% efficient, the equivalent
uncontrolled factor would be 6.0 Ib/ton, which agrees closely with the
previous factor of 5.78 Ib/ton.
Degerming and Milling
Emission factor data were not available.
OAT MILLING
Most of the information necessary for estimating emission factors was
not available. It was felt to be unwise to attempt to use emission
factor data for other grains because handling of oats is reported to be
dustier than many other grains. The only emission factor data that
were available contained controlled emission factors only (Reference 2,
p. 236) which can be used to calculate an overall factor of 0.04 Ib/bu
or 2.5 Ib/ton. It is not known if these data, for one mill, included
most major dust sources nor is it known if this plant, and the control
devices used, is representative of the industry. However, both of the
above were assumed to be true, and the total controlled emission factor
of 2.5 Ib/ton was used.
RICE MILLING
Emission factor data for rice milling operations are meager. Emission
sources associated with receiving, cleaning and storage are similar
to those involved with all grain processing but it is not known if
rice emits more or less dust than other grains in these operations.
However, emission factors for other grains were used.
39
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Receiving
Data in Reference 2 (p. 471) indicate that most rice is received by
truck. An emission factor for truck unloading of 0.64 Ib/ton was
assumed based on data for a terminal grain elevator.!/
Handling and Freeleaning
As was explained in the section on wheat mills, a cumulative emission
factor of 5.0 Ib/ton has been assumed for the similar operations in
a rice mill.
Drying
Observation of rice dryers indicates that the emission factor may be
considerably higher than for drying of other grains but supporting
data were not available.
Cleaning and Mill House
Because of the lack of data, no estimate of the emission factor could
be made.
SOYBEAN MILLS
Receiving
Data in Reference 2 (p. 251) indicate an average controlled emission
factor for a truck dump pit of 0.017 Ib/ton, or an uncontrolled factor
of 1.-5 Ib/ton assuming 99% efficiency for the fabric filter control
device. This is in good agreement with data in Reference 1 for soybeans
which showed 1.63 Ib/ton for truck unloading and 1.51 Ib/ton for car
unloading. Therefore, an emission factor of 1.6 Ib/ton was used for
soybean receiving.
Handling
No specific information was available on emission factors for soybean
handling operations. Evert though the emissions from soybeans may be
higher than other grains the cumulative factor of 5.00 Ib/ton, as dis-
cussed in the wheat milling section, was used.
40
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Cleaning
No information was available on the cleaning of soybeans although it is
suggested that it would be at least as much as the 6.00 Ib/ton discussed
in the section on dry corn milling.
Soybean plants do dry the feed to the flaking mill and observations have
indicated that the emission factor for drying of soybeans at soybean
mills may be higher than the average factors discussed in Appendix A.
The only data available on soybean dryers are contained in Reference 2
(p. 255) and have been used to calculate uncontrolled emission factors
ranging from 4.2 to 80 Ib/ton. The value of 80 Ib/ton is very high
but even disregarding this value, the average factor is 7.2 Ib/ton.
Cracking (and dehulling)
Data presented in Reference 2 (p. 256) show that the controlled emission
factor for cracking and dehulling operations is on the order of 0.01
Ib/bu, or 0.33 Ib/ton. If one assumes 90% efficiency for the cyclone
control devices, the. uncontrolled emission factor would be 3.3 Ib/ton.
Hull Grinding
Controlled emission factors for hull grinding in Reference 2 (p. 256)
show an average, for three reported values, of 0.0055 Ib/bu or 0.18 Ib/ton.
Again assuming 90% efficiency for the cyclone control devices, the un-
controlled emission factor would be approximately 2.0 Ib/ton.
Bean Conditioning
Reference 2 (p. 256) shows a cyclone controlled emission factor of
0.0003 Ib/bu or 0.01 Ib/ton. Assuming 90% cyclone efficiency, the
uncontrolled emission factor is 0.1 Ib/ton.
Flaking
A total of four controlled emission factors for flaking are presented in
Reference 2 (pp. 252, 256) and show an average of 0.0017 Ib/bu or 0.057
Ib/ton. These were each cyclone controlled, so assuming 90% efficiency,
the uncontrolled emission factor would be 0.57 Ib/ton.
41
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Meal Dryer
Cyclone controlled emission factor for meal dryers was presented in
Reference 2 (pp. 252, 256) and showed a range of 0.003 to 0.0128 Ib/bu
with an average of 0.0045 Ib/bu or 0.15 Ib/ton. Again assuming 90%
efficiency for the cyclones, the uncontrolled factor would be 1.5 Ib/ton.
Meal Cooler
Only one cyclone controlled emission factor was available (Reference 2,
p. 252); 0.0056 Ib/bu or 0.18 Ib/ton. Assuming 90% efficiency for the
cyclone, the uncontrolled factor would be 1.8 Ib/ton.
Bulk Loading
No emission factor data were available for meal loading. However,
observation of these operations indicates that it may be about the
same as loading grain at elevators or about 0.27 lb/ton.i'
CORN WET MILLING
Receiving
Corn is received by cars and trucks and, as was done for dry corn mills,
an average emission factor of 1.0. Ib/ton was used.
Handling
Emission factors specifically applicable to handling of corn at wet corn
mills are not available. However, as was done on dry corn mills, an
average cumulative emission factor of 5.0 Ib/ton was used.
Cleaning
An emission factor of 6.0 Ib/ton for corn cleaning, as developed in the
section on dry corn mills, was used.
Dryers
Feed, gluten and germ dryers are a major source of emissions from wet
corn mills but emission factor d ta are lacking.
Bulk Loading
Bulk loading of products is another potential source of emissions but no
emission factor data are available.
42
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA-450/3-75-054
4. TITLE AND SUBTITLE
Emission Factor Development for the Feed and Grain
Industry
g. AUTHOR(S)
P. G. Gorman, M. Schrag, E. Trompeter
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
15. SUPPLEMENTARY NOTES
3. RECIPIENT'S \CCESSIOWNO.
5. REPORT DATE
October 1974
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-1324
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
16. ABSTRACT
This report contains an evaluation of available data used to develop
emission factors for alfalfa dehydration plants, grain elevators and other
feed and grain operations.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS b.lDENTIFI
Emission Factors
Dehydration
Particulate
18. DISTRIBUTION STATEMENT 19. SECURI
Release Unlimited Uncla;
20. SECURI
Uncla;
ERS/OPEN ENDED TERMS c. COSATI Held/Croup
TY CLASS (This Report) 21. NO. OF PAGES
;sified 48
TY CLASS (This page) 22. PRICE
;sified
EPA Form 2220-1 (9-73)
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