Emission Factor Documentation for AP-42

Section 9.5.3

Meat Rendering Plants

Final Report

For U. S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Emission Factor and Inventory Group

EPA Contract No. 68-D2-0159

Work Assignment No. II-03

MRI Project No. 4602-03

September 1995
Emission Factor Documentation for AP-42

Section 9.5.3

Meat Rendering Plants

Final Report

For U. S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Emission Factor and Inventory Group

Research Triangle Park, NC 27711

Attn: Mr. Dallas Safriet (MD-14)

EPA Contract No. 68-D2-0159

Work Assignment No. II-03

MRI Project No. 4602-03

September 1995
ii

NOTICE

The information in this document has been funded wholly or in part by the United States

Environmental Protection Agency under Contract No. 68-D2-0159 to Midwest Research Institute. It has

been subjected to the Agency's peer and administrative review, and it has been approved for publication as

an EPA document. Mention of trade names or commercial products does not constitute endorsement or

recommendation for use.
iii

PREFACE

This report was prepared by Midwest Research Institute (MRI) for the Office of Air Quality

Planning and Standards (OAQPS), U. S. Environmental Protection Agency (EPA), under EPA Contract

No. 68-D2-0159. The EPA work assignment manager for this project is Mr. Dallas Safriet. 

Approved for:

MIDWEST RESEARCH INSTITUTE

Roy M. Neulicht

Program Manager

Environmental Engineering Department

Jeff Shular

Director, Environmental Engineering

 Department

September 1995
iv
v

CONTENTS

LIST OF FIGURES ......................................................... vi

LIST OF TABLES ......................................................... vi

1. INTRODUCTION ................................................... 1-1

2. INDUSTRY DESCRIPTION ........................................... 2-1

2.1 INDUSTRY CHARACTERIZATION ................................. 2-1

2.2 PROCESS DESCRIPTION ......................................... 2-1

2.2.1 Edible Rendering ............................................ 2-1

2.2.2 Inedible Rendering .......................................... 2-3

2.3 EMISSIONS .................................................... 2-7

2.4 EMISSION CONTROL TECHNOLOGY .............................. 2-8

3. GENERAL DATA REVIEW AND ANALYSIS PROCEDURES ................ 3-1

3.1 LITERATURE SEARCH AND SCREENING .......................... 3-1

3.2 DATA QUALITY RATING SYSTEM ................................ 3-1

3.3 EMISSION FACTOR QUALITY RATING SYSTEM .................... 3-2

4. AP-42 SECTION DEVELOPMENT ...................................... 4-1

4.1 REVIEW OF SPECIFIC DATA SETS ................................ 4-1

4.1.1 Reference 1 ................................................ 4-1

4.1.2 Reference 2 ................................................ 4-1

4.1.3 Reference 3 ................................................ 4-2

4.2 CANDIDATE EMISSION FACTORS ................................ 4-2

5. PROPOSED AP-42 SECTION 9.5.3 ..................................... 5-1
vi

LIST OF FIGURES

Figure Page

2-1 Edible rendering process ............................................... 2-2

2-2 Batch cooker rendering process .......................................... 2-5

2-3 Continuous rendering process ........................................... 2-6

LIST OF TABLES

Table

2-1 COMPOSITION OF RAW MATERIALS FOR INEDIBLE RENDERING ........ 2-4

4-1 EMISSION DATA FOR CONTROLLED EMISSIONS FROM BLOOD 

DRYERS .......................................................... 4-3

4-2 CANDIDATE EMISSION FACTORS FOR CONTROLLED EMISSIONS

FROM BLOOD DRYERS ............................................. 4-3
1-1

EMISSION FACTOR DOCUMENTATION FOR AP-42 SECTION 9.5.3

Meat Rendering Plants

1. INTRODUCTION

The document Compilation of Air Pollutant Emissions Factors (AP-42) has been published by the

U. S. Environmental Protection Agency (EPA) since 1972. Supplements to AP-42 have been issued to add

new emission source categories and to update existing emission factors. The EPA also routinely updates

AP-42 in response to the needs of federal, state, and local air pollution control programs and industry.

An emission factor is a representative value that attempts to relate the quantity of a pollutant

released to the atmosphere with an activity associated with the release of that pollutant. Emission factors

usually are expressed as the weight of pollutant divided by the unit weight, volume, distance, or duration of

the activity that emits the pollutant. The emission factors presented in AP-42 may be appropriate to use in

a number of situations, such as making source-specific emission estimates for areawide inventories for

dispersion modeling, developing control strategies, screening sources for compliance purposes, establishing

operating permit fees, and making permit applicability determinations. The purpose of this background

report is to provide information to support preparation of AP-42 Section 9.5.3, Meat Rendering Plants. 

This report contains five sections. Following this introduction, Section 2 gives a description of the

meat rendering industry including a brief characterization of the industry, an overview of the process, and

the identification of emissions and emission control technology. Section 3 describes the literature search,

screening of emission source data, and the EPA quality ranking system for emission data and emission

factors. Section 4 describes the results of the literature search. Section 5 presents the proposed AP-42

Section 9.5.3, Meat Rendering Plants.
2-1

2. INDUSTRY DESCRIPTION1

This section provides an overview of the U. S. rendering industry for the preparation of products

for human consumption (edible rendering) and products not suitable for human consumption (inedible

rendering). This section is divided into four subsections: industry characterization (2.1), process

description (2.2), emissions (2.3), and emission control technology (2.4). The edible rendering industry is

included in Standard Industrial Classification (SIC) Code 2011 and inedible rendering in SIC Code 2077.

2.1 INDUSTRY CHARACTERIZATION1

Rendering plants process animal by-product materials for the production of tallow, grease, and

high-protein meat and bone meal. Plants that operate in conjunction with animal slaughterhouses or

poultry processing plants are called integrated rendering plants. Plants that collect their raw materials from

a variety of offsite sources are called independent rendering plants. Independent plants obtain animal

by-product materials, including grease, blood, feathers, offal, and entire animal carcasses, from the

following sources: butcher shops, supermarkets, restaurants, fast-food chains, poultry processors,

slaughterhouses, farms, ranches, feedlots, and animal shelters.

The two types of animal rendering processes are edible and inedible rendering. Edible rendering

plants process fatty animal tissue into edible fats and proteins. The plants are normally operated in

conjunction with meat packing plants under U. S. Department of Agriculture, Food Safety and Inspection

Services (USDA/FSIS) inspection and processing standards. Inedible rendering plants are operated by

independent renderers or are part of integrated rendering operations. These plants produce inedible tallow

and grease, which are used in livestock and poultry feed, soap, and production of fatty-acids. The Source

Classification Code (SCC) for animal/poultry rendering is 3-02-038-01 (General).

Since the early 1980's, the number of independent rendering plants has significantly declined

because less raw material is available due to changes in the meat packing industry. Also, a downward

trend in tallow and grease prices has contributed to the declining number of plants. In 1992, an estimated

150 independent rendering plants and 100 integrated plants were operating in the United States.

2.2 PROCESS DESCRIPTION1

2.2.1 Edible Rendering

A typical edible rendering process is shown in Figure 2-1. Fat trimmings, usually consisting of 14

to 16 percent fat, 60 to 64 percent moisture, and 22 to 24 percent protein, are ground and then belt

conveyed to a melt tank. The melt tank heats the materials to about 43EC (110EF), and the melted fatty

tissue is pumped to a disintegrator, which ruptures the fat cells. The proteinaceous solids are separated

from the melted fat and water by a centrifuge. The melted fat and water are then heated with steam to

about 93EC (200EF) by a shell and tube heat exchanger. A second-stage centrifuge then separates the

edible fat from the water, which also contains any remaining protein fines. The water is discharged as

sludge, and the "polished" fat is pumped to storage. Throughout the process, direct heat contact with the

edible fat is minimal and no cooking vapors are directly emitted. Because no vapors are emitted, no

emission points are designated in Figure 2-1. 
2-2

Figure 2-1. Edible rendering process.

Fat Trimmings Grinder Melt Tank Disintegrator

Fat Tank Centrifuge Feed Tank Centrifuge

Storage or

Disposal

Fat and

Water

Steam Protein and Water

Sludge Tank

To Inedible

Rendering or

Wastewater

Treatment

Note: No cooking vapors are directly em

so no emission points are indicated.
2-3

2.2.2 Inedible Rendering

Integrated rendering plants normally process only one type of raw material, whereas independent

rendering plants often handle several raw materials that require either multiple rendering systems or

significant modifications in the operating conditions for a single system. Table 2-1 shows the fat, protein,

and moisture contents for several raw materials processed by inedible rendering plants.

There are two processes for inedible rendering: the wet process and the dry process. Wet

rendering is a process that separates fat from raw material by boiling in water. The process involves

addition of water to the raw material and the use of live steam to cook the raw material and accomplish

separation of the fat. Dry rendering is a batch or continuous process that dehydrates raw material in order

to release fat. Following dehydration in batch or continuous cookers, the melted fat and protein solids are

separated. At present, only dry rendering is used in the United States. The wet rendering process is no

longer used because of the high cost of energy and of an adverse effect on the fat quality. The following

paragraphs describe each stage in the dry rendering process.

2.2.2.1 Batch Rendering Process. Figure 2-2 shows the basic inedible rendering process using

multiple batch cookers. In the batch process, the raw material from the receiving bin is screw conveyed to

a crusher where it is reduced to 2.5 to 5 centimeters (cm) (1 to 2 inches [in.]) in size to improve cooking

efficiency. Cooking normally requires 1.5 to 2.5 hr, but adjustments in the cooking time and temperature

may be required to process the various materials. A typical batch cooker is a horizontal, cylindrical vessel

equipped with a steam jacket and an agitator. To initiate the cooking process, the cooker is charged with

raw material and the material is heated to a final temperature ranging from 121E to 135EC (250E to

275EF). Following the cooking cycle, the contents are discharged to the percolator drain pan. Vapor

emissions from the cooker pass through a condenser, which condenses the water vapor and emits the

noncondensibles as VOC emissions.

The percolator drain pan contains a screen that separates the liquid fat from the protein solids. 

From the percolator drain pan, the protein solids, which still contain about 25 percent fat, are conveyed to

the screw press. The screw press completes the separation of fat from solids, and yields protein solids that

have a residual fat content of about 10 percent. These solids, called cracklings, are then ground and

screened to produce protein meal. The fat from both the screw press and the percolator drain pan is

pumped to the crude animal fat tank, centrifuged or filtered to remove any remaining protein solids, and

stored in the animal fat storage tank.

2.2.2.2 Continuous Rendering Process. Since the 1960's, continuous rendering systems have been

installed to replace batch systems at some plants. A typical continuous rendering process is shown in

Figure 2-3. The system is similar to a batch system except that a single, continuous cooker is used rather

than several parallel batch cookers. A typical continuous cooker is a horizontal, steam-jacketed cylindrical

vessel equipped with a mechanism that continuously moves the material horizontally through the cooker. 

Continuous cookers cook the material faster than batch cookers, and typically produce a higher quality fat

product. From the cooker, the material is discharged to the drainer, which serves the same function as the

percolator drain pan in the batch process. The remaining operations are generally the same as the batch

process operations.

In the 1980's, newer continuous rendering systems were developed to precook the raw material and

to remove moisture from the liquid fat prior to the cooker/drier stage. These systems utilize an evaporator

operated under vacuum and heated by the vapors from the cooker/drier. One system, termed waste-heat
2-4

TABLE 2-1. COMPOSITION OF RAW MATERIALS FOR INEDIBLE RENDERINGa

Source

Tallow/grease,

Wt %

Protein solids

Wt %

Moisture, 

Wt %

Packing house offalb

 and bone

Steers 30-35 15-20 45-55

Cows 10-20 20-30 50-70

Calves 10-15 15-20 65-75

Sheep 25-30 20-25 45-55

Hogs 25-30 10-15 55-65

Poultry offal 10 25 65

Poultry feathers None 33 67

Dead stock (whole animals)

Calves 10 22 68

Sheep 22 25 53

Hogs 30 28 42

Butcher shop fat and bone 31 32 37

Blood None 16-18 82-84

Restaurant grease 65 10 25

a

Reference 1.

b

Waste parts; especially the entrails and similar parts from a butchered animal.
2-5

Figure 2-2. Batch cooker rendering process.

VOC Emissions VOC Emissions VOC Emission

Receiving Bin Crusher Batch Cooker Percolator Drain Pan

Protein

Solids

Screw Press

PM Emissions PM Emissions

Grinder Protein Meal Storage Hopper Screen

Oversize

VOC Emissions

Animal Fat

Storage Tank

Centrifuge or

Filter

Crude Animal

Fat Tank

Fat Fat

P

Water

VOC Emissions

Condenser
2-

6

Figure 2-3. Continuous rendering process.

VOC Emissions VOC Emissions VOC Emission

PM Emissions PM Emission

Receiving Bin Crusher Continuous Cookers Drainer Screw Press

VOC Emissions Fat Fat

P

Animal Fat

Storage Tank

Centrifuge or

Filter

Crude Animal

Fat Tank

Protein Meal

Storage Hopper Screen Grinder

Protein

Solids

Oversize

VOC Emissions

Condenser
2-7

dewatering (WHD), consists of treating the raw material in a preheater followed by a twin-screw press. 

The solids from the press are directed to the cooker/drier. The liquid fat is sent to an evaporator operated

under a vacuum and heated by the hot vapors from the cooker/drier to a temperature of 70E to 90EC (160E

to 200EF). In the evaporator, the moisture evaporates from the liquid fat and passes to a water-cooled

condenser. The dewatered fat is recombined with the solids from the screw press prior to entry into the

cooker/drier. These pretreatment systems may reduce fuel costs by 30 to 40 percent and increase

production throughput by up to 75 percent.

2.2.2.3 Blood Processing and Drying. Blood processing and drying is an auxiliary process in meat

rendering operations. At the present time, less than 10 percent of the independent rendering plants in the

U.S. process whole animal blood. Whole blood from animal slaughterhouses, containing 16 to 18 percent

total protein solids, is processed and dried to recover protein as blood meal. The blood meal is a valuable

ingredient in animal feed because it has a high lysine content. Continuous cookers have replaced batch

cookers that were originally used in the industry because of the improved energy efficiency and product

quality provided by continuous cookers. In the continuous process, whole blood is introduced into a

steam-injected, inclined tubular vessel in which the blood solids coagulate. The coagulated blood solids

and liquid (serum water) are then separated in a centrifuge, and the blood solids dried in either a continuous

gas-fired, direct-contact ring dryer or a steam tube, rotary dryer.

2.2.2.4 Poultry Feathers and Hog Hair Processing. The raw material is introduced into a batch

cooker, and is processed for 30 to 45 minutes (min) at temperatures ranging from 138E to 149EC (280E to

300EF) and pressures ranging from (40 to 50 psig). This process converts keratin, the principal component

of feathers and hog hair, into amino acids. The moist meal product, containing the amino acids, is passed

either through a hot air, ring-type dryer or over steam-heated tubes to remove the moisture from the meal. 

If the hot air dryer is used, the dried product is separated from the exhaust by cyclone collectors. In the

steam-heated tube system, fresh air is passed countercurrent to the flow of the meal to remove the moisture. 

The dried meal is transferred to storage. The exhaust gases are passed through controls prior to discharge

to the atmosphere.

2.2.2.5 Grease Processing. Grease from restaurants is recycled as another raw feed material

processed by rendering plants. The grease is bulk loaded into vehicles, transported to the rendering plant,

and discharged directly to the grease processing system. During processing, the melted grease is first

screened to remove coarse solids, and then heated to about 93EC (200EF) in vertical processing tanks. The

material is then stored in the processing tank for 36 to 48 hr to allow for gravity separation of the grease,

water, and fine solids. Separation normally results in four phases: (1) solids, (2) water, (3) emulsion layer,

and (4) grease product. The solids settle to the bottom and are separated from the water layer above. The

emulsion is then processed through a centrifuge to remove solids and another centrifuge to remove water

and any remaining fines. The grease product is skimmed off the top.

2.3 EMISSIONS1,2

Volatile organic compounds (VOCs) are the primary air pollutants emitted from rendering

operations. The major constituents that have been qualitatively identified as potential emissions include

particulate, ammonia, hydrogen sulfide, organic sulfides, disulfides, C-4 to C-7 aldehydes, trimethylamine,

C-4 amines, quinoline, dimethyl pyrazine, other pyrazines, and C-3 to C-6 organic acids. In addition,

lesser amounts of C-4 to C-7 alcohols, ketones, aliphatic hydrocarbons, and aromatic compounds are

potentially emitted. No quantitative emission data were presented. Historically, the VOCs are considered
2-8

to be an odor nuisance in residential areas in close proximity to rendering plants, and emission controls are

directed toward odor elimination. The odor detection thresholds for many of these compounds are low;

some as low as 1 part per billion (ppb). Of the specific constituents listed, only quinoline is classified as a

hazardous air pollutant (HAP). In addition to emissions from rendering operations, VOCs may be emitted

from the boilers used to generate steam for the operation.

Emissions from the edible rendering process are not considered to be significant because no

cooking vapors are emitted and direct heat contact with the edible fat is minimal. Therefore, these

emissions are not discussed further.

For inedible rendering operations, the primary sources of VOC emissions are the cookers and the

screw press. Other sources of VOC emissions include blood and feather processing operations, dryers,

centrifuges, tallow processing tanks, and percolator pans that are not enclosed. Raw material may also be

a source of VOC emissions, but if the material is processed in a timely manner, these emissions are

minimal.

In addition to VOC emissions, particulate matter (PM) is emitted from grinding and screening of

the solids (cracklings) from the screw press and other rendering operations such as dryers processing blood

and feathers. 

2.4 EMISSION CONTROL TECHNOLOGY1,2

Emission control at rendering plants is primarily based on the elimination of odor. These controls

are divided into two categories: (1) those controlling high intensity odor emissions from the rendering

process, and (2) those controlling plant ventilation air emissions. The control technologies that are

typically used for high intensity odors from rendering plant process emissions are waste heat boilers

(incinerators) and multistage wet scrubbers. 

Boiler incinerators are a common control technology because boilers can be used not only as

control devices but also to generate steam for cooking and drying operations. In waste heat boilers, the

waste stream can be introduced into the boiler as primary or secondary combustion air. Primary

combustion air is mixed with fuel before ignition to allow for complete combustion, and secondary

combustion air is mixed with the burner flame to complete combustion. Gaseous waste streams that

contain noncondensibles are typically "cleaned" in a combination scrubber and entrainment separator

before use as combustion air.

Multistage wet scrubbers using various scrubbing agents are the primary alternative to

incinerators. They can be equally as effective as incinerators for high intensity odor control and are used to

about the same extent as incinerators. Sodium hypochlorite is considered to be the most effective scrubbing

agent for odor removal, although other oxidants can be used. Recently, chlorine dioxide has been used as

an effective scrubbing agent. Venturi scrubbers are often used to remove PM from waste streams before

treatment by the multistage wet scrubbers because large particles tend to deplete the oxidizing agent used in

the multistage scrubbing system. A typical multistage wet scrubber system consists of a venturi scrubber

followed by one or two packed bed scrubbers.

Plants that are located near residential or commercial areas may treat process and fugitive

emissions by ducting the plant ventilation air through a wet scrubbing system to minimize odorous

emissions. Wet scrubbing of plant ventilation air is an effective means of controlling odor emissions. In
2-9

these systems, vents from the buildings that house the various processes are ducted to a single-stage

scrubber, usually a packed bed scrubber using sodium hypochlorite as the scrubbing agent. When used in

conjunction with multistage wet scrubbers controlling process emissions, these systems may provide up to

99 percent control of odor emissions.

In addition to the conventional scrubber control technology, activated carbon adsorption and

catalytic oxidation potentially could be used to control odor; however, no rendering plants currently use

these technologies. Recently, some plants have installed biofilters to control emissions.

References for Section 2

1. W.H. Prokop, "Rendering Plants," in Chapter 13, Food and Agriculture Industry, Air Pollution

Engineering Manual, Van Nostrand Reinhold Press, 1992.

2. H.J. Rafson, "Odor Emission Control for the Food Industry." Food Technology, June 1977.
3-1

3. GENERAL DATA REVIEW AND ANALYSIS PROCEDURES

3.1 LITERATURE SEARCH AND SCREENING

Review of emissions data began with a literature and source test search. First, EPA literature and

data were reviewed including review of the AP-42 background files located in the Emission Factor and

Inventory Group (EFIG) and data base searches on the Crosswalk/Air Toxic Emission Factor Data Base

Management System (XATEF), the VOC/PM Speciation Data Base Management System (SPECIATE),

and the Air Chief CD-ROM. New references were identified primarily through reviews of literature

describing changes in meat rendering technology.

During the review of each document, the following criteria were used to determine the acceptability

of reference documents for emission factor development:

1. The report must be a primary reference:

a. Source testing must be from a referenced study that does not reiterate information from

previous studies.

b. The document must constitute the original source of test data. 

2. The referenced study must contain test results based on more than one test run.

3. The report must contain sufficient data to evaluate the testing procedures and source operating

conditions.

3.2 DATA QUALITY RATING SYSTEM1

Based on OAQPS guidelines, the following data are always excluded from consideration in

developing AP-42 emission factors:

1. Test series averages reported in units that cannot be converted to the selected reporting units;

2. Test series representing incompatible test methods; and

3. Test series in which the production and control processes are not clearly identified and

described.

If there is no reason to exclude a particular data set, data are assigned a quality rating based on an

A to D scale specified by OAQPS as follows:

A—This rating requires that multiple tests be performed on the same source using sound

methodology and reported in enough detail for adequate validation. Tests do not necessarily have to

conform to the methodology specified by EPA reference test methods, although such methods are used as

guides.
 * Source category: A category in the emission factor table for which an emission factor has been calculated.

3-2

B—This rating is given to tests performed by a generally sound methodology but lacking enough

detail for adequate validation.

C—This rating is given to tests that are based on an untested or new methodology or that lack a

significant amount of background data.

D—This rating is given to tests that are based on a generally unacceptable method but may provide

an order-of-magnitude value for the source.

The following are the OAQPS criteria used to evaluate source test reports for sound methodology

and adequate detail:

1. Source operation. The manner in which the source was operated should be well documented in

the report, and the source should be operating within typical parameters during the test.

2. Sampling procedures. The sampling procedures should conform to a generally accepted

methodology. If actual procedures deviate from accepted methods, the deviations must be well

documented. When this occurs, an evaluation should be made of how such alternative procedures could

influence the test results.

3. Sampling and process data. Adequate sampling and process data should be documented in the

report. Many variations can occur without warning during testing and sometimes without being noticed. 

Such variations can induce wide deviations in sampling results. If a large spread between test results

cannot be explained by information contained in the test report, the data are suspect and are given a lower

rating.

4. Analysis and calculations. The test reports should contain original raw data sheets. The

nomenclature and equations used are compared to those specified by EPA (if any) to establish equivalency. 

The depth of review of the calculations is dictated by the reviewer's confidence in the ability and

conscientiousness of the tester, which in turn is based on factors such as consistency of results and

completeness of other areas of the test report.

3.3 EMISSION FACTOR QUALITY RATING SYSTEM1

The EPA guidelines specify that the quality of the emission factors developed from analysis of the

test data be rated utilizing the following general criteria:

A—Excellent: The emission factor was developed only from A-rated test data taken from many

randomly chosen facilities in the industry population. The source category* was specific enough to

minimize variability within the source category population.

B—Above average: The emission factor was developed only from A-rated test data from a

reasonable number of facilities. Although no specific bias was evident, it was not clear if the facilities

tested represented a random sample of the industries. As in the A-rating, the source category was specific

enough to minimize variability within the source category population.
3-3

C—Average: The emission factor was developed only from A- and B-rated test data from a

reasonable number of facilities. Although no specific bias was evident, it was not clear if the facilities

tested represented a random sample of the industry. As in the A-rating, the source category was specific

enough to minimize variability within the source category population.

D—Below average: The emission factor was developed only from A- and B-rated test data from a

small number of facilities, and there was reason to suspect that these facilities did not represent a random

sample of the industry. There also may be evidence of variability within the source category population. 

Limitations on the use of the emission factor are footnoted in the emission factor table.

E—Poor: The emission factor was developed from C- and D-rated test data, and there was reason

to suspect that the facilities tested did not represent a random sample of the industry. There also may be

evidence of variability within the source category population. Limitations on the use of these factors are

footnoted.

The use of the above criteria is somewhat subjective depending to a large extent on the individual

reviewer. Details of how each candidate emission factor was rated are provided in Section 4.

References for Section 3

1. Technical Procedures for Developing AP-42 Emission Factors and Preparing AP-42 Sections,

EPA-454/B-93-050, U. S. Environmental Protection Agency, Office of Air Quality Planning and

Standards, Research Triangle Park, NC, October 1993.
4-1

4. AP-42 SECTION DEVELOPMENT

This section describes the test data and methodology used to develop pollutant emission factors for

the meat rendering industry. Section 9.5.3, Meat Rendering Plants will be new to Chapter 9 of AP-42.

4.1 REVIEW OF SPECIFIC DATA SETS1-2

During the literature search, only three test reports were found and one report was unsuitable for

the calculation of emission factors because of the lack of process data. The other reports characterized

emissions from a natural gas-fired blood dryer. A summary of each of the three references is provided

below but only References 2 and 3 were used to estimate emission factors.

4.1.1 Reference 1

An emissions test was conducted at the Darlings Delaware rendering plant in Fresno, California to

determine if a specific group of compounds were present at selected locations in the emissions control

system. The specific compound and groups of compounds of interest were formaldehyde, trace organics,

mercaptans, amines, organic acids, and C2-C10 hydrocarbons. The four sampling locations were the outlets

of wet scrubbers #1 and #2, and the inlet and outlet of a waste heat incinerator. No process description or

process data were provided. Only a single test run was performed at each sampling location. The results

of this emission test are unsuitable for estimation of emission factors because there are no process data to

form the basis for an emission factor. Portions of this test report are provided in Appendix A.

4.1.2 Reference 2

This test report summarizes the results of emission tests for the blood dryer at the Milwaukee

Tallow Company. The tests were conducted in September 1989 to provide compliance data for

PM/PM-10, hydrogen sulfide, and ammonia. Triplicate tests were conducted in the vent stack for each

pollutant using EPA Method 5 for particulate emissions (both filterable PM-10 and condensible PM were

reported), EPA Method 11 for hydrogen sulfide, and NIOSH P&CAM Method 125 for ammonia. A six

stage in-stack Cascade Impactor was used to collect particle size samples for PM-10 analysis. The test

results are summarized as follows:

Emission Rates (lb/hr)

Particulate

Test run Ammonia Hydrogen sulfide

Filterable

PM-10

Condensible

PM

1

2

3

Average

0.92

1.15

2.51

1.53

1.00

0.90

0.84

0.91

0.94

0.62

0.46

0.67

<0.005

<0.003

0.266

0.091

The raw blood feed rate was 26,300 pounds per hour (lb/hr) during each of the three runs and the

dried blood production rate was 2,275 lb/hr during each of the runs. During a major portion of run 3 of the

particulate test, overloading of the process occurred. The results of the particle sizing indicated that the

particulate sampled was 100 percent PM-10.
4-2

The tests appeared to be conducted using sound methodology with good documentation provided

with respect to the test protocol used, the raw data obtained, and supporting calibration data. No operating

parameters were provided for the venturi or packed-bed scrubbers. Therefore, the filterable PM-10 data

were assigned a quality rating of B. Because the methodology used to obtain condensible PM data was not

specified, those data were assigned a C rating. Applicable portions from the test report are provided in

Appendix B.

4.1.3 Reference 3

This reference presents the results of a particulate emissions test for the blood dryer at the

Farmland Food plant in Iowa Falls, Iowa. The tests were conducted in January, 1987 to provide

compliance data for total particulate. Triplicate tests were conducted in the vent stack after a mechanical

centrifugal separator. Both filterable and condensible PM were obtained using EPA Method 5. The results

of the test are summarized as follows:

Particulate emission rates, lb/hr

Test run Filterable PM Condensible PM

1 0.12 NDa

2 0.051 0.066

3 0.076 0.066

Average 0.082 0.062

aND = no data; data not reported for condensible PM.

The dried blood production rate was 1,030 lb/hr during each of the three runs. No data were

presented for condensible PM in run 1.

The results of this emission test were rated C because no raw data sheets, process diagrams, test

calibration data, or description of the sampling sites and methodology were provided. Applicable portions

from the test report are provided in Appendix C. 

4.2 CANDIDATE EMISSION FACTORS

There were no test reports identified that were suitable for the calculation of emission factors for

the meat rendering operations. The only test reports containing sufficient data for emission factor

estimation were for controlled emissions from a natural gas-direct fired blood dryer. Table 4-1
4-3

TABLE 4-1. EMISSION DATA FOR CONTROLLED EMISSIONS FROM 

BLOOD DRYERS

Pollutant

Emission factor, dried product,

lb/tona Data rating Reference

Filterable PM-10 1.34

0.16

E

E

2

3

Condensible PM 0.80

0.12

E

E

2

3

Hydrogen sulfide 0.08 E 2

Ammonia 0.60 E 2

aExpressed as weight per unit weight of dried blood meal product. 

TABLE 4-2. CANDIDATE EMISSION FACTORS FOR CONTROLLED EMISSIONS 

FROM BLOOD DRYERSa

Pollutant Emission factor range, lb/ton

Emission factor,

lb/ton

Emission factor

data rating Reference

Filterable PM-10 0.16-1.34 0.76 E 2, 3

Condensible PM 0.12-0.80 0.46 E 2, 3

Hydrogen sulfide NAb

0.08 E 2

Ammonia NAb

0.60 E 2

aEmission factor units are weight per unit weight of dried blood meal produced.

bNA = not applicable; only one test.
4-4

 presents the emission data for PM, hydrogen sulfide (H2S), and ammonia (NH3) in terms of weight per

1,000 lb of dried blood meal product. The candidate emission factors based on these data are presented in

Table 4-2.

The emission control system in Reference 2 consisted of a cyclone separator for collection of the

blood meal product followed by a venturi wet scrubber and three packed bed scrubbers in series. The

scrubbing medium for each of the three packed bed scrubbers was a sodium hypochlorite solution. The

emissions testing was conducted 6 feet upstream from the outlet of the vent stack to the atmosphere.

The emission control system in Reference 3 was a mechanical centrifugal separator. No

information was provided for the distance of the testing from the outlet of the separator.

References for Section 4

1. Emission Testing at the Darlings Delaware Rendering Plant, Fresno, CA, prepared for Darlings

Delaware Company, Dallas, TX by Genesis Environmental Services Company, July 1990.

2. Blood Dryer Operation Stack Emission Testing, prepared for Milwaukee Tallow Company, Inc.,

Milwaukee, WI by Environmental Technology and Engineering Corporation, Elm Grove, WI,

September 1989.

3. Blood Dryer Particulate Emission Compliance Test, Interpoll Report No. 7-2325, prepared for

Farmland Foods, Inc., Iowa Falls, IA by Interpoll Laboratories, Inc., Circle Pines, MN, January 1987.
5-1

5. PROPOSED AP-42 SECTION 9.5.3

A proposed AP-42 Section 9.5.3, Meat Rendering Plants, is presented in the following pages as it

would appear in the document.

[Not presented here. See instead final AP-42 Section 9.5.3]