DRAFF
SOURCES
OF
ATMOSPHERIC CADMIUM
I .S. ENVIRONMENTAL PROTECTION" \(,KNCY
Office of Air and Waste Management
Office of Yir Quality Planning and Standards
Rest-arch Triangle Park, North Carolina 2771 1
-------
DRAFT
SOURCES
OF
ATMOSPHERIC CADMIUM
Energy and Environmental Analysis, Inc.
1111 North 19th Street, 6th Floor
Arlington, Virginia 22209
Contract No. 68-02-2836
EPA Project Officer. Richard Johnson
Strategies and Air Pollutant Standards Division
Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
Februar) 27. 1978
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TABLE OF CONTENTS
TITLE PAGE
EXECUTIVE SUMMARY 1
SECTION I: INTRODUCTION 9
SECTION II: CADMIUM IN THE ENVIRONMENT 11
A. Introduction 11
B. Physical and Chemical Characteristics
of Cadmium 11
C. Multi-Media Nature of Cadmium Exposures 12
SECTION III: METHODOLOGY 17
A. Introduction 17
B. Determination of Potential Cadmium Emission -,7
Sources
C. Emission Factor Determination 18
D. Computation of Emission Levels 20
E. Source Screening 20
SECTION IV: USES OF CADMIUM 22
A. Introduction 22
B. Electroplating 22
C . Paint Pigments 24
D. Plastic Stabilizers 24
E. Nickel-Cadmium Batteries 25
F. Miscellaneous 25
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TABLE OF CONTENTS (Continued)
TITLE PAGE
SECTION V: SOURCES OF ATMOSPHERIC CADMIUM
EMISSIONS 27
A. Introduction 27
B. Mining 28
C. Primary Metal Production 29
D. Iron and Steel 4g
E. Secondary Smelting 5g
F. Manufacturing 62
G. Fossil Fuel Combustion 69
H. Miscellaneous 76
I. Incineration 81
J. Summary 85
SECTION VI: SCREENING OF CADMIUM SOURCE TYPES 98
A. Introduction 98
B. Mining 102
C. Primary Metals 104
D. Iron and Steel 105
E. Secondary Smelting 106
F. Manufacturing 107
G. Fossil Fuel Combustion 107
H. Miscellaneous 109
I. Incineration 110
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EXECUTIVE SUMMARY
This report is one of a series of reports which will be
used by EPA in responding to the Congressional request under
section 122 of the Clean Air Act Amendments of 1977 to deter-
mine whether atmospheric emissions of cadmium pose any threat
to public health. This report surveys the uses of cadmium
and potential emission sources to determine which sources are
the most significant both in terms of total emissions and
potential ambient levels.
The basic methodology used in this report is as follows:
• Determination of potential cadmium emission
sources through a literature review;
• Determination of emission factors (Ibs.
cadmium emitted/unit output) for each
source;
• Application of these emission factors to
current and projected production levels
to obtain estimates of total cadmium
emissions;
• Evaluation of control technology for
reducing cadmium emissions;
• Screening of all cadmium sources to
identify those sources potentially able
to cause measurable ambient levels of
cadmium.
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Consumption of cadmium in the U.S. has averaged about
5,000 megagrams/year over the last several years. United
States production is closely tied to zinc production and
has not been adequate to meet demand. In 1975 almost 40 per-
cent of the cadmium used in the U.S. was imported. The prin-
cipal uses of cadmium and their relative share of consumption
is shown in Figure E-l.
It is estimated that about 914 tons of cadmium were
emitted during 1974. The breakdown of emissions by source
category is shown on Table E-2. This table also lists the
anticipated change in cadmium emissions due to growth changes
in technology or the anticipated imposition of higher effi-
ciency control equipment.
As 5able E-l shows, the largest estimated emitter of
cadmium is the production of zinc. This source accounts for
approximately 53 percent of total cadmium emissions. Although
zinc production is expected to increase significantly, emissions
are not expected to increase and very possibly will decrease
due to the increased use of electrolytic processes which have
almost no emissions.
Emissions from other major sources (incinerators, iron
and steel and fossil fuel combustion) are expected to remain
relatively constant as the increased production is balanced
by the increasing levels of control technology.
Data on Table E-l is based on the use of "best judgement"
emission factors developed through a review of the literature
and various stack test results. Table E-2 shows the emission
factors developed in this study. Also shown on Table E-2 is
the minimum and maximum emission factor reported for any of
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PLASTICS
STABILIZATION
20%
ELECTROPLATING
55%
FIGURE E-l
CADMIUM CONSUMPTION IN THE UNITED STATES (1)
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TABLE E-l
AIRBORNE CADMIUM EMISSIONS--1974 . 1985
Source
MINING
Zinc
Copper
Lead
PRIMARY METALS
Zinc
Pyroneta1lurgic
Electrolytic
Lead
Copper
Cadmium
SECONDARY METAL PROCESSING
Iron and Steel
Sinter Windbox Uncontrolled
Sinter Windbox w/Rotoelone
and ESP
Basic Oxygen Furnace
Uncontrolled
BOF v/venturi or ESP
Open Hearth Uncontrolled
Open Hearth w/ESP
Electric Arc Uncontrolled
Electric Arc Controlled
Blast Furnace Controlled
Overall Uncontrolled
Zinc
Lead
Copper
MANUFACTURING
Pigments
Stabilisers
Batteries
FOSSIL FUEL COMBUSTION
Coal-Fired Power Plants
Oil-Fired Power Plants
Beating Oil
Dieael Oil
Gasoline
MISCELLANEOUS
Motor Oil
Rubber Tire Hear
Fungicides
Fertilizers
Cement
INCINERATION
Sewage Sludge Incinerators
Municipal Incinerators
Production Emissions
1974* Estimate
478,
1,414,
603,
423,
121,
866,
1,435,
3,
850 «1
246.8 <1
024 <1
000 529
945 0
095 2
662.4 5
088.2 2
Reference
12
12
12
40
40
40
40
12
Production Emissions
1985 (e) Estimate
845,377 <1
2.563,122 <1
1,169.524 <1
1,000,000 529
-
790,000 2
3,849,844 13.4
1.139 <1
Referer
41
41
41
9
-
9
9
9
21.94x10°
11.35x10"
22
5.4
13
13
991.24
40x10"
19
882.3
13
1.2x10°
78.8X106
7.64xl06
29.06X106
27.3X106
_
95.2x10
12.84x10*
182,665
698,698,
513,308
1,212.1
991.8
628.14
3.913X108
(Btu's)
SOOxlO6
(barrels)
935.1X106
(barrels)
llxlO9
(gallons)
1.330,074xl06
(VHT)
1.028,121xl06
(VHT1
I,330,024xl06
(VMT)
59,800
8,S35xl03
81,210xl03
1,460,000
20,1-43^620
•
< 1
< 1
22
2
46
4.6
0
95
< 1
< 1
38
9
3
< 1
7.04
9
29.2 (1975)
<1
13
< 1
S
< 1
< 1
< 1
< 1
131
13
13
13
13
13
13
13
13
12
12
12
6
6
6
42
42
45
39
43
43
43
9
9
9
36
34
-
1.73X106
_
21.1X106
_
38.8X106
113.6X106
-
223.000
860,000
800,000
1,560
1,179
2,200
530.750xl06
732.2X106
(barrels)
980.9xl06
(barrels)
15.12xl09
(gallons)
I,707,152xl06
(VMT)
1.707,152xl06
(VMT)
1.707.1S2X106
(VMT)
92,769
13,240xl03
94,537xl03
1,551.250
20,143,620
-
< I
_
< 1
_
3.3
0
-
< 1
< 1
60
11.3
3.5
2.2
15.9
19.9
30.5
5.25
17.1
1.7
6.8
* 1
1.3
< 1
< 1
131
13
13
_
13
13-
-
19
9
20
6
6
6
24
46
46
38
44
44
44
9
9
32
35,36
34
tons per year unless otherwise stated.
e • estimated
VMT • vehicle miles -traveled
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TABLE E-2
CADMIUM EMISSION FACTORS
SOURCE
MINIMUM
MAXIMUM
BEST JUDGEMENT
PRIMARY METALS PROCESSING
ZINC
Coking
Sintering w/Cyclone
Sintering w/Cyclone 1 ESP
Roasting
llurirnntal Retort
Vrrtical Retort
Clt-iirnthermie
Oveull (Not Electrolytic)
Electrolytic
IEAD
Overall Smelter
Blast Furnace n/Baghouse
COPPER
Uncontrolled Smelter
Smpl">r w/Baghouse (~95%)
CADMIUM
SECONDARY METALS PROCESSING
IRON '. STEEL
Sinter Wlndbox-Uncontrolled
Sinter Wfndbox
v/Rotoclone 4 ESP
Blast Furnace-Controlled
Open Hearth-Uncontrolled
Open Hearth w/ESP
Basic Oxygen Furnace
Uncontrolled
w/Ventur1 or ESP
Electric Arc Furnace
Overall-Uncontrolled
SECONDARY ZINC-UNCONTROLLED
SECONDARY LEAD
Blast Furnace w/3 Cyclones
1 Baghouse
Reverberatory Furnace w/
Cyclone I Baghouie
Reverberatory Furnace »/
3 Cyclones i Baghouse
SECONDARY COPPER-UNCONTROLLED
MINING OF ZINC-BEARING ORES
Zinc Ore
Lead Ore
Copper Ore
MANUFACTURING
Allays ( Solders-Controlled
Pdliipnts w/Baghouse
SUbillzers (for Plastics)
w/Raghouse
Batteries (lll-Cd)
Miscellaneous (X-Ray Screens
Cathode Ray Tubes. Nuclear
Reactor Components,etc.)
9 04xlO~1/TZnThru (STK.AA
4.06lb/TZnThru (STK.AA)
1152lb/TZnThru (STK.AA)
1.2xlO'21b/TZnThru (EST)
1.43lb/TZnProd (EST)
5.2xlO'Z1b/TPbProd (EST.MB)
7xlO-21b/TCu (EST.MB)
25lb/TCdProd (EST.SURV.MB)
1.35xHT31b/TFeed (STK.ES)
9.33xlO"*lb/TFeed (STK.ES)
4.0»10~31b/TSteel (STK.AA)
2.08xlO'51b/TSteel (EST.CONC)
3.45xlO"61b/TSteel (STK.ES)
Z.7xlO"31b/TSteel (EST.CONC)9/
2.2xlO'61b/TSteel (EST.MB)
8xlO'31b/TZn (SURV.HB)
5.9xlO"71b/TPb (STK.ES)
5.9xlO'71b/TPb (STK.ES)
6.5xlO'91b/TPb (STK.ES)
2.6lb/TCu Scrap (EST.MB)
3.78lb/TZnThru (STK.AA)
8.53lb/TZnThru (STK.AA)
2.B0lb/TZnThru (STK.AA)
8.76xlO'Zlb/TZnThru(STr.AA)
2.961b/TZnProd (STK.AA)
2.6xlO"llb/TPbProd (EST.MAX ,.
CONCr'
2.9xlO"llb/TCu (EST.MB)
30.51b/TCdProd (EST.MB)
2.63xlO"3'b/TFeed (STK.ES)
9.76xlO"41b/TFeed (STK.ES)
7.49xlO"31b/TSteel (STK.AA)
1.33xlO'41b/TSteel (STK.AA)
2.79xlO'Slb/TSteel (STK.ES)
2 34lb/TZnThru
6 321b/TZnThru (STK.AA)
2.161b/TZnThru (STK.AA)
-0 (EST)
6xlO"31b/TZnProd (EST)
G.5xlO"Zlb/TZnThru (S'K.AA1
l.lxlO"11b/TPbProd
AVE C?
,r\V
5.25xlO"31b/TZn (STK.ES)
7«1001b/TCu (EST)
28lb/TCd5'
-0 (ESTT'
5.78xlO'31b/TSteel (S'V.A."
l.lxlO'41b/TSteel (SH.A/H
4.1xlO'51b/TSteel (CQiC)7/
1.2xlO-51b/TSteelB/
5xlO"3lb/TSteel (EST.STK.CONC)10/ 3.4xlO"31b/TSteel
3.SxlO'31b/TSteel (EST.MB)
1.4xlO'21b/nn Prod (MB)
3.5xlO"S1b/TPb (STK.ES)
4xlO"*1b/TPb (STK.ES)
2xlO'*1b/TPb (STK.ES)
41b/TCu Scrap (EST.HB)
1 7xlO-51b/TSteel1?/
lxlO-21b/TZn Prod13'
r-Ci
2xlO-61b/TPbI4/
1.6xlO-6Ib/TPb15/
SxlO-71b/TPb16/
31b/TCu Scrap17/
2xlO"Ilb/TCd 1n Ore (E5T.>"'
lx!0"31b/TZn in Ore (E5T."!t)
IxlO"*lb/TPb m Ore !E:* «i
3.2xlO~5l!>/TCu o frr. •
101b/Kd CNi-cec- IS1.1"1.11
15lb/TCd Charue-f (IS*.1-1
61b/TCd Charged (EST.SITF)
2Ib/TCd Charged (SL'HV
2lb/TCd Chargprf (EST)
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TABLE E-2 (Continued)
CADMI.IM EMISSION FACTORS
SOURCE
MINIMUM
MAXIMUM
BEST
rOSSIL FUEL COMBUSTION
Coal-Fired Power Plants
Uncontrolled
Controlled (ESP)
OH-Fired Power Plants
Controlled ( - ESP)
Heating Oil (Residual; 16
Fun! Oil)
Diesel Oil
Gasoline (for IS npg, til
Cd Emitted)
11WAC.L SLUDGE INCINERATORS
Multiple Hearth w/Scrubber
Fluldlzed Bed -/Scrubber
MUNICIPAL INCINERATORS
Uncontrolled
Controlled (Scrubbers or ESP)
LUBRICATING OIL INCINERATORS
Uncontrolled
MISCELLANEOUS
Motor Oil Consumption
_,,•-> (Vehicles)
•Rubber Tire Wear
Fungicides Application
Fertilizers Application
Superphosphate Fertilizers
Application
CtHtHT PLANTS
OUT PROCESS
Kiln w/Baghouse or ESP
Raw N111 Feed w/Baghouse
Raw Mill w/Baghouse
Raw Mill Air Separator w/
Baghouse
Finish Hill Feed w/
Baghouse
Finish Mill w/Baghouse
Finish Mill Air Separator
H/Bcinhouse
wcr rnorrss
Kiln u/CSP
Raw Mill w/Baghouse
Clinker Cooler w/ESP
or Oaghouse
I IHE KILN (PULVERIZED COAL)
Kiln w/Spray, Settle ft
Baghouse
lx!0'*1b/TCoal (STK.AA)
lxlO'61b/TCoal (STK.AA)
7.1xlO"71b/gal (STK.ES)
1.5xlO-61b/gal (EST.CONC)"'
6xlO"71b/gil (EST.CONC.ES)Z6/
6.3xlO'111b/veh-m1 (EST. „.
CONC)Z9/
lxlo-61b/Tslu(jge
ES)
4xlO'71b/TSludge (DRY)
(STK.ES)
3xlO"31b/TRefuse (EST)
6xlO""b/TRefuse (FLAA)
Ixl0'101b/veh-m1 (EST.CONC)37/
1.8xlO'61b/gal (EST.MB)*0'
1.7xlO'"b/T (EST.MB)
3xlO"7'b/TFeed (STK.ES)
lx!0'71b/TFe-d (STK.ES)
7.6xlO*71b/TFeed (STK.ES)
SxlO'71b/TFeed (STK.ES)
7.4xUT61b/TFeed (STK.ES)
1.7xlO'61b/TFeed (STK.ES)
4.6xlO~51b/TFeed (STK.ES)
lxlO'11b/TCoal (STK.ES)
7xlO'*1b/TCoal ISTK.AA)19'
4.4xlO'61b/gal (STK.CONC.ES)21'
4xlO"51b/gal (EST.CONC.NA)"'
2xlO'61b/gal (EST)27/
4.5xlO'81b/veh-m1 (EST.CONC)30/
2xlO'51b/TSludge (DRY) (STK.ES)
3xlO'61b/TSludge (ORYJ(STK.ES)
1.8xlO'21b/TRefuse (STK.ES)M/
1.0xlO"llb/TRefuse (EST.HB)
5xlO'81b/veh-m1 (EST.CONC)38/
5xlO'51b/g»l (EST)
SxlO'm/T (EST.MB)
4.1xlO*71b/TFeed (STK.ES)
4.3xlO"71b/TFeed (STK.ES)
9xlO"71b/TFeed (STK.ES)
1.6xlO"61b/TFeed (STK.ES)
1.3xlO'71b/TFeed (STK.ES)
2xlO'*1b/TFeed (STK.ES)
lx!0'*lb/TFeed (STK.ES)
6.9xlO"51b/TFeed (STK.ES)
l«1001b/TCoal18/
6xlO-51b/TCoalZO/
9xlO'71b/gal (STK.ES)"'
3xlO-61b/gal"/
7xlO'71b/gal (EST.CONC.ES)ZB/
2xlO'81b/veh-mi31/
7xlO"61b/TSludoe (DRVl (SI',
!.3xlO'61b/TSludge (DRY)(1U.
ES'
6xlO'31b/TRefuse (STK,ES!3V
1.3xlO"21b/TRefuse (S-'..AA)3t
2xlO'61b/gal (UNK)
2xlO'91b/veh-ml (UNK)
BxlO-9lb/veh-m139>
3xlO"*1b/TFeed (STK.ES)
3.6xlO'71b/TFeed
2.7xlO"71b/TFeed
8.5xlO'7'b/TFeed
lxW61b/TFeed
lxlO'71b/TFeed
2.6xlO'61b/TFeed
2xlO-5Ib/TFee
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the sources. It is clear that significant differences can
exist among tests on different sources. As such, although
the emission factors are probably adequate for the purpose of
evaluating differences among source categories, care must be
taken in the application of these factors to any particular
source.
After emission factors and emission levels were deter-
mined for particular source categories, sources were evaluated
to determine if an individual source had the potential to
cause a measurable level of cadmium (assumed to be 0.1 ng/m
on an annual average). Screening was accomplished by modeling
a very large plant in each category under very astringent
assumptions of stack height, flow rate, temperature and meteor-
ology. The evaluation procedure was not designed to determine
what expected levels of cadmium might be, but to determine if
any possibility existed that the source could cause a measur-
able level. A more detailed modeling effort was undertaken
during the cadmium exposure analysis.
Table E-3 lists the source categories which were deter-
mined to be potentially able to cause a measurable level of
cadmium. These sources were further evaluated in the second
phase of this study to evaluate the population potentially
exposed.
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TABLE E-3
SOURCE CATEGORIES POTENTIALLY ABLE TO
CAUSE A MEASURABLE LEVEL OF CADMIUM
Primary Zinc Smelters
Primary Copper Smelters
Primary Lead Smelters
Primary Cadmium Smelters
Secondary Zinc Smelters
Secondary Copper Smelters
Municipal Incinerators
Iron and Steel Mills
a' Assumed to be 0.1 ng/m on an annual average.
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SECTION I
INTRODUCTION
This report is one in a series of reports which will be
used to help EPA respond to the Congressional mandate under
Section 122 of the Clean Air Act Amendments of 1977. Under this
section, EPA is required to review the health and welfare ef-
fects of cadmium (as well as other substances) and determine
"...whether or not emissions of...cadmium...into the ambient air
will cause, or contribute to, air pollution which may reasonably
be anticipated to endanger public health."
This report focuses on three of the areas of information
required to make this determination—identification of the uses
and sources of cadmium, development of emission factors for
cadmium from industrial sources, and the screening of cadmium
sources to determine which sources are potentially "significant"
sources of ambient cadmium. For screening purposes of this
report, a "significant" source is one which, by itself, can
cause a measurable ambient level of cadmium.
A companion study takes information from this study to
provide an estimate of the population exposed to measurable
levels of cadmium. Neither this report, nor the companion re-
port on population exposure, draws any conclusions as to the
health consequences of ambient cadmium levels. Rather, the pur-
pose of the two reports is to provide a relative ranking of
sources, both by the magnitude of emissions and the population
exposed, and to provide information in such a way so as to allow
EPA to make informed estimates of any health implications of the
reported emissions and exposures.
-------
The report is organized into several sections summarized
below:
• Section II provides an overview of the physi-
cal and chemical properties of cadmium, as
well as the routes through which cadmium ex-
posure could occur.
• Section III provides an overview of the metho-
dology used in preparing this report.
• Section IV discusses the current and expected
uses of cadmium.
• Section V discusses the potential emission
sources for cadmium. For each source, a
brief description of the process, cadmium
emission points, and the emission factors
are described. Total current and expected
cadmium emissions and available control tech-
nology are also discussed.
• SECTION VI discusses the screening of
the various cadmium sources which was used
to determine which cadmium sources can
cause a measurable level of cadmium
(0.1 ng/m on an annual average).
10
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SECTION II
CADMIUM IN THE ENVIRONMENT
A. Introduction
This section discusses the physical and chemical properties
of cadmium and the multi-media nature of cadmium exposures. Al-
though this report focuses only on atmospheric exposures to cad-
mium, it is important to keep in mind that there are many other
types of human exposure to cadmium.
B. Physical and Chemical Characteristics of Cadmium
Cadmium is a relatively rare element in the earth's crust.
It occurs at a concentration of 0.1 to 0.5 ppm, ranking in
abundance between mercury and silver, and thus, not in sufficient
2/
quantities to be mined as an ore. ' Table III-l shows the physi-
cal properties of cadmium. Cadmium is always associated with
4 /
zinc and is usually present as a sulfide. '
The most important characteristic of cadmium, from an air
pollution viewpoint, is its high volatility. This is evidenced
by its low melting (312° C) and boiling (765° C) points. Thus, any
high temperature process, such as metalurgical processes (steel-
making, sintering) or incineration, are likely to release what-
ever cadmium is present in the feed.
Vaporized cadmium metal is quite reactive and should react
very quickly to form an oxide, sulfate or other compound. In these
forms, cadmium is quite stable and of very low solubility in water.
11
-------
Cadmium metal is ductible, easily soldered can and can be
readily electroplated and maintains a lustrous finish in air. '
These properties lead to the use of cadmium as a protective coat-
ing on iron and steel products.
C. Multi-Media Nature of Cadmium Exposures
While this report is focused on the atmospheric emissions of
cadmium, it is important to recognize the overall cycle of cadmium
in the environment. Measurable levels of cadmium occur in all
phases of environmental concern (air, water, food, solid waste),
and in almost all areas. One author ' refers to cadmium as the
"dissipated element." EPA in 1975 ' estimated that about 1,800
Mg/year of cadmium was lost to the environment. Of this, about 18
percent was in atmospheric emissions, 75 percent in solid waste,
and the remainder in water-borne emissions.
Measurable cadmium levels have been found in air, water, soil
and food. Atmospheric concentrations generally have been measured
in the center of urban areas and generally range from 0.1 /ag/m
down to below the detectable limit. Typical urban concentrations
are in the range of 0.003 jig/m . Due to the low solubility of
cadmium compounds, levels of cadmium in water supplies are gen-
erally low. Main sources of cadmium are discharges from mining
operations, leaching from soil disposal of wastes and rain-out
from atmospheric emissions.
Cadmium in food results from a wide variety of sources.
>d in
they are:
8/
Listed in order of importance from a recent Battelle Report, '
(1) Direct contact by plants or uptake from soils
by plant roots. Cadmium may occur in soil:
a. Naturally as a normal constituent of
soils of marine origin.
12
-------
b. As an impurity (cadmium oxide) in
phosphate-treated soils, especially in
those treated with "superphosphate."
c. By fertilization with sludge con-
taining cadmium.
d. By desposition of cadmium-containing
pesticides or as a contaminant of
zinc-containing pesticides.
e. From run-off of mine tailings or from
electroplating washing process.
(2) Accumulation in animal tissues due to:
a. Feeding on crops which have absorbed
cadmium. (The organs of such animals
may have very high cadmium concentrations.)
b. Treatment with cadmium-containing hel-
minth kilers, used especially in swine.
(3) Concentrations of cadmium by molluscs and
crustaceans and most other aquatic organisms
from ambient waters.
(4) Use of zinc-galvanized containers, cans, cook-
ing implements or vessels; or utensils used in
food preparation, particularly grinders, press-
ing machines, or galvanized netting used to dry
fish and gelatin.
(5) Adsorption of cadmium contained in wrapping
and packaging materials such as paper, plastic
bags, and tin cans.
'13
-------
(6) Use of cadmium-contaminated water in cook-
ing or processing operations.
Table II-2 lists the average cadmium concentration of se-
lected adult foods.
Cigarette smoking also provides a large contribution to total
cadmium exposure. The estimated intake from two packs per day
ranges from four to six micrograms. This amounts to about 20
times the exposure due to atmospheric levels in large urban areas.
Even for smokers, food provides the greatest overall exposure
to cadmium, and based on a 6.4 percent retention rate, the greatest
daily input (except for three packs-per-day-smokers). Table II-3
summarizes the sources of cadmium exposure.
14
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TABLE II-2
CADMIUM CONTENT OF SELECTED ADULT FOODS
a/
Standard
Commodity
Carrots, roots fresh
Lettuce, raw crisp head
Potatoes, raw white
Butter
Margarine
Eggs, whole fresh
Chicken fryer, raw
whole or whole cut up
Bacon, cured raw, sliced
Frankfurters
Liver, raw beef
Hamburger, raw ground beef
Roast, chick beef
Wheat flour, white
Sugar refined, beet or cane
Bread, white
Orange juice, canned frozen concentrate
Green beans, canned
Beans, canned with pork and tomato sauce
Peas, canned
Tomatoes, canned
Diluted fruit drinks, canned
Peaches, canned
Pineapple, canned
Applesauce, canned
No. of
Samples
69
69
71
71
71
71
71
71
69
71
71
71
71
71
70
71
71
71
71
71
71
71
71
71
Average
ppm
0.051
0.062
0.057
0.032
0.027
0.067
0.039
0.040
0.042
0.183
0.075
0.035
0.064
0.100
0.036
0.029
0.018
0.009
0.042
0.042
0.017
0.036
0.059
0.020
Deviation,
ppm
0.077
0.124
0.139
0.071
0.048
0.072
0.088
0.160
0.111
0.228
0.122
0.034
0.150
0.709
0.063
0.095
0.072
0.000
0.113
0.113
0.052
0.061
0.153
0.027
a/
Source: Reference 8
15
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TABLE II-3
MEDIA CONTRIBUTIONS TO NORMAL RETENTION
OF CADMIUMa//
Medium Exposure Level Daily Retention
(ug)
Ambient air 0.03 ug/m 0.15
Water 1 ppb 0.09
Cigaretts:
Packs/Day ug/day '
1/2 1.1 0.70C/
1 2.2 1.41C/
2 4.4 2.82C/
3 6.6 4.22C/
Food 50 ug/day 3.0
a' Source: Reference 8.
Based on 0.11 jug per cigarette.
c/
Assumes a 6.4 percent retention rate.
16
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SECTION III
METHODOLOGY
A. Introduction
This section describes the general methodology used in
evaluating sources of cadmium emissions and in determining the
magnitude and significance of these sources. In simplest
terms, the methodology can be viewed as having five components:
• Determination of potential cadmium emission
sources;
• Determination of emission factors for these
sources;
• Estimation of current and future emissions
of cadmium;
• Evaluation of control technology for re-
ducing cadmium emissions from these
sources; and
• Screening of all potential cadmium sources
to identify the sources most likely to cause
measurable ambient levels.
B. Determination of Potential Cadmium Emission Sources
A literature search and a review of previous EPA studies
was carried out to determine the sources most likely to emit
cadmium. The basic procedure followed in this study, as well as
17
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in previous studies, was to concentrate on the production and
uses of cadmium, and then to follow cadmium through to its
ultimate disposal.
Once the potential sources were identified, trade litera-
ture and other references were used to develop process descrip-
tions, identify potential emission sources, and estimate total
current and projected production. Special emphasis was placed
on determining changes in production patterns which could lead
to changes in emission characteristics. The sub-sections of
Section V which discusses each industry identify the data used
to develop the above information.
C. Emission Factor Determination
For each source identified as potentially emitting cadmium,
the literature was surveyed to determine the amount of cadmium
emitted per unit of product produced. For most sources, several
types of data were available and a ranking system was estab-
lished in determining the final emission factor. The data were
ranked in the following order:
• Actual Stack Tests—Stack tests conducted on
several sources, or even one source, and ana-
lyzed by a quantitative analytic technique
such as atomic apsorbtion (AA). Stack tests
conducted using a semi-quantitative technique
such as emission spectroscopy (ES) were given
a somewhat lower ranking. The primary source
of stack tests using ES came from EPA tests
in support of particulate new source perfor-
mance standards.
18
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• Concentration of Cadmium in Feed—For fuel
burning sources, data on incoming cadmium
levels can be used to determine cadmium
emissions relatively accurately if 100
percent loss of cadmium is assumed. This
assumption is reasonable because of the
high volatility of cadmium.
• Mass Balances—For several sources, the only
data available came from an estimate of the
losses of cadmium during processing. Data
comes from site visits carried out by EPA
during earlier emission factor development
and engineering judgement on process operations.
For each source type, several emission factors were de-
veloped:
• Minimum Emission—Lowest emission factor
reported by any study.
• Maximum Emission—The highest emission
factor reported by any study.
• Best Judgement—The best estimate of emis-
sions when the quality of all the data is
considered and the ranking system described
above is used.
As with any substance, cadmium emissions can vary greatly from
source to source, and the accuracy of any specific emission
factor for a specific plant is questionable. The emission fac-
tors developed here are probably sufficiently accurate for the
purposes intended (relative evaluation among source categories),
19
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but care should be taken in applying the factors to any specific
plant.
D. Computation of Emission Levels
The production levels for each source category and the
emission factors previously developed were combined to provide
an estimate of total current cadmium emissions. The emission
factors were modified (where necessary) to reflect the appli-
cation of typical control technology.
E. Source Screening
To determine which source types are capable of causing a
measurable level of cadmium (assumed to be an annual average of
0.1 ng/m ), a screening procedure was developed. While the de-
tailed procedure for screening varied from source type to
source type (each is discussed in Section VI), the general
procedure is as follows:
• For each source type, an expected largest
or very large source in each type was de-
termined from the literature.
• A very conservative combination of stack
conditions was then determined. These
conditions (stack height, temperature,
flow, etc.) were based on engineering
judgement, coupled with limited data
available in the literature. Every as-
sumption was made such that ground level
concentrations would be maximized.
•20
-------
• Emissions were based on maximum emission
factors and plants were assumed to produce
their rated capacity in only eight hours
of operation.
• Ambient concentrations (for point sources)
were determined using the EPA "PTMAX" model.
If these concentrations exceeded the detect-
able limit C.lng/m ), further analysis was
required. This criterion is extremely con-
servative because the PTMAX estimates one-
hour concentrations, which are typically at
least ten times higher than annual averages.
It is recognized that the above approach is extremely
conservative and the results are much higher than would nor-
mally be estimated. However, the purpose of the screening is
to determine what sources have almost no potential for causing
measurable levels of cadmium. Further analysis of the sources
which passed this screening was carried out using the EPA
CRSTER model and more reasonable stack assumptions. The
results of this analysis are discussed in the companion study
to this report.
21
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SECTION IV
USES OF CADMIUM
A. Introduction
Consumption of cadmium in the United States has averaged
approximately 5,000 metric tons a year over the past several
years. In 1975, almost 40 percent of the cadmium used in the
U.S. was imported.
There are four major uses of cadmium, all of which are
dissipative (Figure 1). In 1974, approximately 46 percent
(2,700 metric tons) of the cadmium consumed in the U.S. was used
by the electroplating industry. Paint pigment manufacturing
required close to 1,000 metric tons of cadmium in 1974, and 900
metric tons were used to produce plastic stabilizers. ' The
fourth major use of cadmium in 1974 was the nickel-cadmium
battery, for which 550 metric tons of the metal were used. '
Cadmium is also used in nuclear reactor controls, fluorescent
phosphors, and in alloys.
B. Electroplating
Electroplating a metal with cadmium inhibits corrosion and
enhances solderability. Products made of iron and steel are
most frequently coated with cadmium, including motor vehicle
parts, industrial machinery parts, aircraft parts, marine equip-
ment , and hardware.
There are several reasons why cadmium is preferred as a
coating material. Only a thin coating is necessary to provide
22
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to
Ul
PLASTICS
STABILIZATION
20%
ELECTROPLATING
55X
FIGURE 1
CADMIUM CONSUMPTION IN THE UNITED STATES (1)
-------
adequate protection from corrosive elements, especially salt
water and alkalies. It is possible to obtain a uniform deposi-
tion on objects of intricate design, and luster is maintained
for a long period of time. Although several substitutes exist,
cadmium is believed to be superior.
C. Paint Pigments
Paint pigment production accounts for approximately 20
percent of the U.S. consumption of cadmium. The cadmium-
sulfide compounds are used to obtain colors ranging from yellow
to orange, while the cadmium-sulfoselenide compounds produce
colors ranging from orange to light red and deep maroon.
It has been estimated that approximately 75 percent of the
pigments are used to color plastic. Other uses for cadmium
pigments include water-base paints, rubber, artists' colors,
printing inks, glass, textiles, enamels, and ceramic glazes.
Cadmium pigments have certain properties which render them
difficult to replace. Because they are totally non-bleeding
and alkalai-resistant, they are particularly suitable for
plastic automobile interior parts. The pigments provide very
bright colors and a high degree of opacity. Their high temper-
ature properties contribute to the unique character of the
pigment.
D. Plastic Stabilizers
The third major consumer of cadmium is the plastic stabil-
izer industry. Heat stabilizers containing cadmium have been
found to halt or slow discoloration caused by the breakdown of
polyvinyl chloride resin during molding. The stabilizers are
found in almost every plastic material with the exception of
food packaging, where use is prohibited by FDA regulations.
24
-------
Substitutes for the cadmium plastic stabilizers may be
forthcoming in light of FDA regulations. Stabilizers of
calcium-zinc composition have been found to be competitive in
both performance and cost, and are expected to replace the cad-
mium stabilizer in some items sometime in the future.
E. Nickel-Cadmium Batteries
The nickel-cadmium battery is the fourth major product com-
posed of cadmium. Demand for cadmium in this segment of the in-
dustry tripled between 1968 and 1973. Batteries range in size
from small button cells (614 mm in diameter) to large rectangular
cells (113 mm high by 91 mm long by 38 mm wide).
The nickel-cadmium battery is used in a variety of systems
and products including alarm systems, pacemakers, and portable
appliances and tools. Calculators presently are the largest
market for the battery. The nickel-cadmium battery is prefer-
rable to others if long-life is important.
F. Miscellaneous
Cadmium is also used to produce alloys, primarily low tem-
perature solders, silver bronzes, and a copper alloy used in
automobile radiators. Nuclear reactor rods are often made of
silver-cadmium. Cadmium phosphates are used for television and
fluorescent tubes; silver-cadmium oxide is used in motor starting
switches, relays, and circuit breakers.
25
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REFERENCES
1. , Determination and Evaluation of En-
vironmental Levels of Cadmium, EPA 68-01-1983, Battelle-
Columbus Laboratories, Columbus, Ohio, 1977.
2. Sargent, D.J. and Metz, J.R., Technical and Microeconomic
Analysis of Cadmium and Its Compounds, Environmental Protec-
tion Agency, 560/3-75-005, June 1975.
26
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SECTION V
SOURCES OF ATMOSPHERIC CADMIUM EMISSIONS
A. Introduction
Cadmium, a relatively rare element in the earth's crust,
does not occur alone naturally. It is a metal found only in
conjunction with other metallic ores, principally zinc, lead,
and copper. Released into the environment, cadmium can be
absorbed, ingested or inhaled by biological systems, causing
subsequent damage to these systems. This study focuses upon
one form of environmental release—emission to the atmosphere.
Airborne cadmium emissions result from the production of
cadmium, its use (primarily dissipative), and the use of other
substances which are contaminated with cadmium. Cadmium is
produced commercially as a by-product of the primary production
of zinc, and is found in the ores of lead and copper also. As
a result, the mining and primary smelting of these three metal
ores produce approximately 56 percent of the cadmium emitted to
the air. Cadmium is a major constituent in the production of
paint pigments, metal alloys, plastic stabilizers, and nickel-
cadmium batteries. Metals are often electroplated with cadmi-
um. Substances which contain cadmium as a contaminant include
phosphatic fertilizers, sewage sludge, fossil fuels, cement, and
fungicides. All of these materials contribute to the emission
of cadmium into the environment.
Each process which contributes to the amount of cadmium in
the air is described in the following sections, together with
27
-------
control devices used, and national production trends for the
near future.
B. Mining
The mining of zinc, lead, and copper is a source of
airborne cadmium emissions, though the quantities emitted are
small—less than one ton a year.
1. Process
The process of preparing each metal ore for shipment to a
primary smelter involves two steps, mining and beneficiation.
First, the large chunks of ore are removed from the ground,
crushed, and ground to fine, sand-sized particles. The concen-
tration process which follows is most often done using a com-
bination of gravity and flotation mechanisms or using flotation
alone; however, some plants use only gravity settling. At this
point, any cadmium in the ore is present in the zinc concen-
trate. Ore beneficiation is usually conducted in close proxi-
mity to the mine, particularly in the western states.
2. Emissions Source and Control
The major emissions from this phase of the metal produc-
tion are a result of the dust which escapes during mining and
crushing. Because beneficiation is a wet process, air emissions
from this phase are minimal. Control methods are rarely needed
or used during the ore-crushing procedures due to the effective
design of the equipment; however, in any raw material handling,
a hood and a cyclone, baghouse, or the electrostatic precipitator
(ESP) is used.1/
28
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3. Emission Estimate
Emission factors used in this estimate were 1x10 pounds/
2 3/ -4
ton of zinc in the ore, ' ' 1x10 pounds/ton of lead in the
2 3/ -5 2 3/
ore, ' ' and 3.2x10 pounds/ton ' ' of copper in the ore.*
From these emission factors and production figures, the emissions
estimate of less than one ton of cadmium per year was develop-
ed. Estimates from other organizations are in agreement with
EEA's, as similar emission factors were used (GCA—<1 ton ;
Mitre—41 ton11/; Davis—
-------
are two basic methods used to obtain the desired output—
pyrometallurgical and electrolytic extraction. The first step
in each process is the roasting of the zinc concentrate,
during which zinc sulfide is converted to zinc oxide. The
sulfur which escapes from this process is often converted to
sulfuric acid in a contact process acid plant.
In the pyrolytic reduction of the ore, the next step is
sintering, which renders the material better to handle and use
as feed. Smelting of the zinc oxide follows the sintering.
Smelting is conducted in batches in horizontal retorts or con-
tinuously in vertical retorts, electrothermic furnaces, or blast
furnaces. Addition of carbon to the zinc oxide at this point
indirectly aids reduction of the oxide to the zinc metal, as it
reacts more readily with oxygen than does the zinc. The metal
is then vaporized, transferred from smelter to condensers,
converted to molten zinc, and cast into slab zinc. Slab zinc is
frequently purified further by redistillation.
Electrolytic zinc recovery was developed chiefly for the
processing of low-grade or mixed ore concentrates. As high
grade zinc deposits are depleted, this process will assume an
increasingly important role in the processing of zinc (and other
metals).
Any likeness of the electrolytic process to the pyro-
metallurgical processes ends with roasting. In electrolytic
recovery, the roasted zinc ore is leached with sulfuric acid
to produce soluble zinc sulfates. Filtration to remove insoluble
impurities (including cadmium) is followed by treatment of the
solution with zinc dust. This treatment is done twice—the
first time to remove copper impurities, and the second to
produce a zinc-cadmium residue. It is possible to continue
further processing of these residues to recover the copper and
cadmium contained in them.
30
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In the next step, zinc metal is produced by processing of
the zinc sulfate solution in electrolytic cells. The zinc is
then electrodeposited onto aluminum cathodes. At regular
intervals, the cathodes are removed from the electrolytic
cells, the zinc is- stripped from the aluminum, and then melted
to produce slab zinc. Slab zinc produced in this manner does
not usually require any additional refining, as it is of very
high purity. It is not possible to process scrap in this manner
as it contains too many impurities.
Figure 1 illustrates the primary zinc smelting process.
(b) Emission Sources
The processes which contribute most to the release of air-
borne cadmium emissions are thermal processes, as cadmium has
very low melting and boiling points (321° C and 767° C, respec-
tively) . Therefore, roasting, sintering, and reduction in the
pyrometallurgical process would warrant the closest attention,
as they probably would be responsible for most of the airborne
cadmium emissions.
The roasting procedure, part of both the pyrometallurgic
and electrolytic processes, is not considered a source of large
cadmium emissions. Control technology used at roasting facili-
ties is highly effective and allows almost no emission of cad-
mium into the air. '
Sintering is considered the major potential source of cad-
mium, and is done at all pyrometallurgical plants. Reduction
of the sintered ore is considered a source of airborne cadmium
only if the externally-fired horizontal retort is used, as this
configuration is not conducive to particulate control. Only one
31
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FIGURE 1
PRIMARY SMELTING PROCESS OF ZINC AND LEAD
2/
ATMOSPHERE
SULFURIC ACID TO ROASTED
ZINC' ORE LEACHING OR SALES
ATMOSPHERE
CO
ISJ
ZINC VAPOR
CONDENSATION
Cd
OR
SLA
CADMIUM OXIDE
T° Cd RECOVERY
SOZ
RECOVERY
SLAB ZINC
•PURIFICATION
OR SALES
ZnO TO Zn
ORE ROASTING
&-
LEAD ORE
CONCENTRATE
t~
LEAD ORE
ROASTING
INCREASINGLY
BYPASSED
LEAD
SMEL
ORE
TING
I
LEAD
BULLION
•CADMIUK
AND AR
RECOVE
UNFl
SL
A
SENIC
RY
JMEO
AC
t
SLAG
FUMING
1
FUMED
SLAG
-------
domestic plant (National Zinc) employs the horizontal retort,
and it is expected that in the near future this retort will be
replaced.
Electrolytic processing is considered to be relatively
free of airborne emissions. A minor potential source of air-
borne cadmium emissions does exist in the filtration which fol-
lows leaching.
(c) Control
High efficiency control devices are employed at all zinc
smelters. Roaster facilities at all smelters use fabric filters
or electrostatic precipitators (ESP). Sintering emissions are
also controlled with fabric filters or ESPs.
(d) Emissions Estimates
Estimates of the cadmium released into the air through pri-
mary zinc production made by EEA have been compared with esti-
mates from other sources. EEA's emission factors, with assumed
control technologies, were derived from several sources and
expressed in pounds per ton of zinc produced. Yost (1974), and
Jacko and Nuendorf (1977) measured coking emissions of 2.34
4 5/
pounds/ton of zinc throughput using stack sampling ' ' and atomic
absorption (AA) analysis. Sintering with a cyclone produces
emissions at a rate of 6.32 pounds/ton of zinc produced, while
sintering with controls of a cyclone and an ESP releases 2.16
pounds/ton of zinc throughput. The vertical retort, at the
particular plant where the stack tests were conducted, emitted
_2
6.50x10 pounds/ton of zinc throughput. It should be noted
that these particular test results, though highly accurate in
both sampling and analysis, may not be typical. Vertical re-
torts, which produce high emissions, are uncommon in the U.S.;
33
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in addition, high zinc losses were a problem at the plant,
largely due to the high temperatures in the coking operation
which was volatizing zinc and thus, cadmium also. The Sargent
(1975) study concluded that roasting emits negligible amounts
of cadmium into the air. Sargent's other estimated emissions
factors which EEA used include: 6x10 pounds/ton of zinc
_2
produced in a horizontal retort; 1.2x10 pounds/ton of zinc
produced by the electrothermic process; and negligible emissions
.ed
3,7,8/
from electrolytic processes. ' Overall emissions rates varied
between 1.43 pounds/ton of zinc and 2.96 pounds/ton of zinc.
To calculate an emissions estimate, a factor of 2.5 pounds/ton
of zinc produced for nonelectrolytic processes was estimated by
weighting the atomic absorption stack sampling results more
heavily than previous mass balances.
Production figures (1974) of 423,000 tons of zinc processed
pyrometallurgically and 121,945 tons of zinc processed electro-
lytically were combined with the overall emissions factor to
obtain EEA's emissions estimate of 529 tons yearly.
The above estimate compared favorably with others made
previously and was very close to the GCA estimate of 500 tons/
year. ' Mitre found that 619 tons of cadmium were released in
primary zinc smelting, EPA estimates 644 tons of cadmium,
and Sargent estimates 112 tons. ' The Sargent estimate is
lower than others made because it assumes 95 percent or better
cadmium collection efficiencies which are presently attainable.
The production at primary zinc smelters increased in 1976
9/
for the first time since 1972. ' In the years between 1972 and
1976, production had steadily decreased. This may account for
the variety of emissions estimates obtained. Both the Mitre
and EPA estimates were made before the decline in production
34
-------
occurred. GCA's was made during a low point and EEA's, based
on 1974 data, illustrates the effect of more recent emission
factors.
(e) Future Trends
Future emissions are expected to decrease over the next
eight years in spite of an anticipated substantial increase in
capacity. Between 1967 and 1975, the zinc industry lost nearly
50 percent of its capacity due to environmenal problems, rising
9/
costs, and scarce capital. In 1976, however, there was a
small increase in zinc production (4.6 percent) over 1975 and
projections for
tion over 1976.
9/
costs, and scarce capital. In 1976, however, there was a
small increase in zinc production (4.6 percent) over 1975 a
projections for 1977 indicate a 9.6 percent increase in produc-
9/
The zinc market is expected to remain stable. No large
decrease in use is anticipated. There is a possibility of
increased use of zinc by the steel industry, as the use of
thinner gauge steel will create the need for increased corrosion
protection (zinc-coated steel).
Domestic smelter capacity is expected to increase steadily
through 1985. For example, ASARCO has planned to open 180,000
9/
ton/year electrolytic plant in Kentucky during 1979. If
present industry expansion plans continue, 1,000,000 tons of
g /
zinc would be produced in the United States in 1985. '
Increased construction of electrolytic zinc-processing
plants has led EEA to conclude that cadmium emissions from this
source is estimated to remain constant at 529 tons/year. This
is a high estimate, as the nonelectrolytic plants now in opera-
tion will probably be phased out and replaced by electrolytic
plants.
35
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2. Primary Lead
Primary lead is a source of cadmium emissions, but does
not contribute greatly to the production of commercial cadmium
metal. Lead is produced in much the same way as zinc, there-
fore, only a brief discussion of the process follows.
(a) Process
Roasting is usually the first step which the ore concen-
trate undergoes in the process of purification and metal pro-
duction. However, this is not always done with the lead concen-
trate. More often, the sintering machine or electric furnace
receives the lead sulfide ore concentrate directly. During the
sintering process, the concentrates are combined with coal,
lime and silica flux, then reduced to the lead metal. At a
blast furnace, the ore is initially reduced to molten metallic
lead and then removed as lead bullion at specific intervals.
Slag processing is more common in primary lead smelting
than in zinc smelting. The slags are placed in a fuming furnace,
brought to the proper temperature and mixed with powdered coal
which burns and volatilizes most of the zinc remaining in the
slag. Any residual lead is also collected.
Figure 1 illustrates the processing of primary lead.
(b) Emission Sources
As in zinc smelting, thermal processes are the cause of
most emissions from lead smelting.
Roasting is not considered a pollution source, as it is
often deleted, and when used, employs as good control technology.
Sintering operations create most of the airborne cadmium emissions
36
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in lead ore concentrate processing. With the exception of one
plant, all use updraft sintering which is considered superior
to other types. Reduction blast furnaces are also a source of
cadmium emissions; however, all plants use extremely efficient
particulate collection apparatus on the sinters and blast furnaces.
(c) Control Technology
In attempting to control the emission of cadmium to the
atmosphere, several collection devices are employed in primary
lead processing. Emissions from sintering and blast furnaces
are usually controlled with a cyclone plus a baghouse or an
ESP. A waste heat boiler plus baghouse or ESP is used with the
reverberatory furnace. In handling material from any of the
steps of the processes, a hood and a settling chamber, cyclone,
ESP, or baghouse is used to control emissions. '
(d) Emissions Estimate
The emissions of cadmium from lead processing are estimated
to equal two tons/year. Using data from several sources, ' ' ' °'1:L/
an emissions factor of 1.1x10" pounds/ton of lead produced was
obtained, assuming 3.0 percent cadmium in the particulate emis-
sions. With a 95 percent control efficiency, the factor was
g /
used with a production figure of 866,095 tons (1974) ' to
arrive at the above figure. The estimate is lower than those
previously made (Mitre—55; ' EPA—163; ' GCA—652') , as the
previous estimates were based on mass balances of the amount of
cadmium in the feed material, assuming no control or, at most,
a 50 percent control efficiency.
(e) Future Trends
At present, the primary lead industry is slowly recovering
from the depressed level of 1975 with a growth rate of approxi-
g/
mately 1.6 percent (compounded annually) expected through 1985.
37
-------
The major uses of lead include storage batteries, gasoline
anti-knock additives, and pigments. The battery market is con-
sidered strong. A substantial increase in demand is due to the
desire on the part of the consumer for a longer-lasting battery,
which requires 20-30 percent more lead for each unit. There is
a possibility that batteries with longer lives may lead to a
9/
depresesed market by 1985. '
The demand for lead by the gasoline industry is expected to
drop sharply. This market, which usually accounts for 17-18
percent of the lead consumed, faces a reduction potential of 70
9/
percent in demand over the next few years.
Modifications of the catalytic converter and internal com-
bustion engines which would allow use of leaded gasoline are
still under study. This could bring about increased demand for
lead, but the feasibility still remains unclear. Lead in paint
pigments accounts for approximately six percent of total lead
production, an increase over the last several years.
At present, producers are hesitant to increase capacity be-
cause of environmental regulation uncertainty and, at this
9/
point, production equals only 87 percent capacity. Therefore,
growth is expected in a steady, slow manner. NSPS regulations
are not likely to affect the lead industry, as no new construc-
tion is being considered for the near future. EEA projects that
a total of two tons/year of cadmium will be released into the
air as a result of primary lead processing by 1985.
3. Primary Copper
Copper production constitutes a source of cadmium emissions
into the atmosphere, but the concentration of the cadmium in the
38
-------
ore is too low for an economical recovery. Emissions from this
source are generated in much the same manner as those from lead
and zinc.
(a) Process
Ores which contain low percentages of copper are first sub-
jected to a grinding and flotation process to produce a high
percentage copper concentrate. The concentrate is then
roasted to remove excess sulfur, and is placed in the reverbera-
tory furnace. Here, a slag is formed through a combination of
iron oxide and siliceous flux; a matte of copper, iron, and
some sulfur is left. The convertor then reduces the matte to
copper metal. To accomplish this, a stream of blowing air
first eliminates sulfur. Then, a second stream of air reduces
the copper sulfide to metal. At this point, the blister
copper is refined further by fire-refining to reduce sulfur
and oxygen, and the refined metal is then cast. (Figure 2.)
(b) Emission Sources and Control
The thermal processes are again responsible for cadmium
emissions. Roasting is considered a source of emissions in the
copper production, and is usually controlled with a settling
chamber, water spray, and some use of the ESP. Reverberatory
furnace emissions are controlled with the ESP; converter emis-
sions are controlled with settling chamber plus cyclones, and,
at times, with an ESP. The settling chamber with cyclone is
only good for larger particulates; therefore, control is not as
efficient as possible at some smelting plants.
39
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FIGURE 2
PRIMARY SMELTING PROCESS OF COPPER
2/
*>.
o
COPPER
CONCENTRATES
FLUID-BED
ROASTER
3 EACH
(3 PLANTS)
ELECTRIC FURNACE
I EACH
(I PLANT)
GREEN FEED
(6 PLANTS)
REVERBERATORY
FURNACE
26 EACH
(14 PLANTS)
BLISTER
COPPER
MULTIPLE-HEARTH
ROASTERS
33 EACH
(4 PLANTS)
-------
(c) Emission Estimates
Primary copper production is a major source of atmospheric
cadmium emissions. Two sets of emissions factors have been
found, one for emissions from uncontrolled facilities, and one
for facilities with the baghouse filter. In an uncontrolled
smelter, emission factors range from a possible 7x10 pounds/
ton of copper to 2.9xlO~ pounds/ton of copper. ' ' ' ' A
best judgement figure of 1.5xlO~ pounds/ton of copper was de-
veloped from an average of five mass balance estimates. If all
copper is produced without the use of control devices, 108 tons
of cadmium would be released yearly. However, copper smelters
employing baghouse control devices release only 7xlO~ pounds
2/
for every ton of copper produced. ' Five tons per year are
emitted from these smelters. EEA's estimate for uncontrolled
copper smelter emissions is very closely aligned to GCA's of 110
tons/ year, ' while EPA ' and Mitre ' estimates equal 234 tons
and 388 tons, respectively. Both these emissions estimates were
made at earlier dates before certain data were available.
(d) Future Trends
There are several possible applications which would create
an increased demand for copper, and some technologies which will
cause a decrease in copper consumption. The factors should
combine to increase copper production by 4.8 percent annually
through 1985.9/
The recent energy shortages have encouraged the development
of solar energy applications and electric cars. In comparison
to the conventional 1975 model car with 41 pounds of copper, the
electric car is expected to contain about 200 pounds per car.
Desalinization technology, which employs copper alloy tube, has
become an industry of significance in countries such as Saudi
41
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Arabia. Fire sprinkler systems are becoming a required part of
any new inhabited building, and this is expected to increase
copper demand and production. An increasing use of electronics
in the telephone industry has reduced the use of copper conduc-
tors, and glass fiber optics will produce the same effect.
Therefore, emissions of cadmium from primary copper'production
are expected to increase to 13.4 tons/year by 1985 in control-
led smelters.
4. Cadmium
Unlike the other three metals discussed, cadmium is not
mined, but rather is a by-product of other metal productions—
primarily zinc. "Blue Powder," a part of the volatile product
from zinc distillation, was at one time the major source of
cadmium metal for commercial production. Most of the cadmium
which is present in zinc and lead ore is now removed in earlier
stages of processing.
There are several major sources of cadmium. Dust and
fumes collected in the bag filters and ESP during roasting and
sintering of the ores, and the cadmium and zinc filter cakes
resulting from the purification of zinc sulfate solutions are
two important sources.
Additional flue dusts, primarily from Mexico, are imported
to meet consumption demands.
(a) Process
There are two basic methods used to recover cadmium; one
which serves to extract the metal from zinc ore roasting and
sintering flue dusts, the other which extracts the metal from
42
-------
any leaching residues. Other processes are used to remove the
metal from other flue dusts and slab zinc redistillation.
It is first necessary to insure that as much cadmium as
possible is incorporated into the roasting and sintering flue
dusts. This is done in one of two ways. In one, after roaster
flue dusts have been returned to the roasted zinc ore concen-
trates, zinc chloride or sodium chloride is added. Sinter-
scalping, the second method used to concentrate cadmium in flue
dusts, involves releasing the "top" part of the sinter to zinc
smelting, and recycling the bottom part (where most cadmium is
collected) through sintering.
These dusts are then usually processed for cadmium recovery,
which entails several steps. First, the cadmium is treated
with sulfuric acid to become cadmium sulfate. During this
treatment, lead is precipitated, filtered, and sent to a lead
smelter in the form of lead sulfate. Next, a sponge is formed
by addition of acid and zinc dust to the cadmium sulfate solu-
tion. The sponge is then washed and dried, mixed with coke and
distilled. The resultant vapor is condensed and cast into
metal balls or ingots. Any distillation residues are directed
back to the sintering process. The sponge can also be purified
through treatment with a high-grade zinc dust and converted to
molten cadmium metal by adding molten caustic soda. This pro-
cess decreases airborne emissions when compared to the direct
melting of sponge.
In electrolytic production, the cadmium loss to flue dust
is not as great, so that the dusts must be returned to the
roasted zinc ore before sulfuric acid treatment in order to
ensure sufficient cadmium concentration. The resulting solu-
tion is then mixed with zinc dust to remove any copper and to
43
-------
produce a zinc-cadmium cake. This cake is often subjected to
an air or steam treatment preceeding a sulfuric acid and elec-
trolytic treatment. The final cadmium sulfate solution is ob-
tained by adding zinc dust to the cake to produce a cadmium
metal sponge which, in turn, is redissolved in the electrolyte.
This solution is then electrolyzed to metal, deposited onto
aluminum cathodes, stripped from the cathodes, and melted to
cast ignots.
Cadmium is also recovered from lead and copper ores,
though this is not usually done. Generally, it is not an econ-
omical practice.
It is also possible to obtain cadmium from the redistilla-
tion of contaminated zinc slab. The distillation is a two-step
process. First, the impure zinc is placed in a still at a tem-
perature which distills the zinc and cadmium to be condensed in
a second still, while the lead remains behind. The zinc-
cadmium mixture is then distilled at a temperature such that
the cadmium is vaporized, while the zinc remains in a molten
form. The cadmium is then condensed and cast.
See Figure 3 for a flow diagram of cadmium recovery from
the above processes.
(b) Emissions Sources and Control
Emissions are again a result of the high temperature pro-
cesses involved in the production of cadmium metal. Cadmium
distillation and vapor condensation are major sources of cadmi-
um emissions. Most cadmium purification processes are wet, so
that many steps do not contribute to airborne cadmium. Most
smelters employ high efficiency bag filters or ESPs as control
devices to prevent cadmium emissions. '
44
-------
FIGURE 3
#•
PRIMARY SMELTING PROCESS OF CADMIUM''
INCOIS
TO SiLES
OUSTS
INSOLUOLC P»SC4
TO LEAD SMELTERS
'ZnCl, TO Zn
ORE SINTERING
. RESIOUfS TO Zn
! ORE SINTERING
OR Pb SMELTERS
RESIDUES TO In
ORE SINTERING
(1 &-6%Cd)
THALLIUM
CHLORIDE
BYPRODUCT
LEA(j AND ZINC
FUMING '-NO
LEAD AND
COPPER
LAG
U1
CHIIOMATE OR
OlCHRCMATE
• •.•EL TING
FLUE OUSTS
<5%Cd
COPPEH-LEftD PESIDUE
TO LEAD SMELTERS
THALLIUM CMROMATE
BYPRODUCT
RESIDUES TO
LEAD SMELTERS
AHSfMiC TO
LEAD SMElURS
AGIO
AND ZINC OUST
Zinc TO
ROASTING
ZnSO. TO In
ELECTROLYSES
SPENT ELECTROLYTE
CADMIUM-{INC
MCCTIFlCATlON
ZINC/
-------
(c) Emissions Estimate
EEA's emissions estimate is lower than estimates by the
EPA and GCA due to EEA's use of current data on control technology,
Emission factors ranged from 25 to 30.5 pounds/ton cadmium
produced. ' ' ' A "best judgement" (the average of three
mass balance estimates) of 28 pounds of cadmium produced was
12/
used, together with a 1974 production figure of 3,088.2 tons '
to reach the estimated emissions of two tons of cadmium emitted
2/
from facilities with a 95 percent control efficiency. EPA '
estimated that cadmium production resulted in 60 tons/year and
GCA estimate equals 50 tons.
(d) Future Trends
Cadmium production has decreased quite steadily in the
past five years, resulting in a drop from 3,760 tons in 1972 to
127
702 tons in 1976. This is due, in part, to the decreased
use resulting from environmental regulations and is closely
associated with the drop in production of zinc. However, cad-
mium production is not expected to continue its downward trend,
but rather to increase along with zinc production in the near
future. At present, cadmium is used for a variety of items
which will be discussed in the following sections. However, it
is possible that the producers of solar energy equipment could
become large consumers of the metal. Cadmium production is
linked to zinc production and, therefore, is expected to in-
crease at a similar rate. Emissions are projected at less than
one ton/year by 1985.
D. Iron and Steel
The iron and steel industry contributes a large amount of
cadmium into the air. These emissions are a result of the
46
-------
melting of cadmium-coated scrap, usually number two steel scrap.*
Descriptions of the four major types of plants, including the
sintering strand, the open hearth, the basic oxygen furnace,
and the electric arc, are included with current industry trends.
The blast furnace, which emits almost no cadmium, is excluded.
1. Sintering
The sintering plant receives two different materials which
require processing. Beneficiation of very fine iron ore and
flue dusts is accomplished at the sinter plant and different
iron-bearing materials become agglomerated at the plant.
Sintering of the above materials ensures a higher iron content,
lessens moisture, and often removes some sulfur. This renders
the resultant product a more suitable feed for the blast
furnace.
(a) Process
To accomplish the sintering, a mixture of fine ore and
powders of carbon sources, such as anthracite and coke breeze,
are placed on a traveling grate. The grate moves over a series
of windboxes where the mixture is lit with a burner. As air is
pulled down through the ore with fans, the ore mixture burns,
agglomerating the ore particles. The use of sinter aides the
performance and productivity of blast furnaces.
(b) Emission Sources
During the heating of the mixture of fine ore and other
materials (blast furnace and other flue dusts), cadmium escapes
*Steel is often galvanized with cadmium to protect it from
corrosion. When the scrap is melted, cadmium is emitted.
47
-------
into the atmosphere. Because the flue dust, and other such
materials contain amounts of cadmium, any heating of this
material causes cadmium to volatilize.
(c) Control
Sinter strands employ one or more of three types of con-
trol devices. The cyclone is employed alone, or more often
with a baghouse or ESP. In 1976, approximately 66 percent of
the sinters used little or no control, while 34 percent em-
ployed at least one of the above methods. '
(d) Emissions Estimate
The estimate of airborne cadmium emissions emanating from
the sintering process was developed from two sets of EPA stack
sampling tests for which a semi-quantitative analysis technique,
emission spectroscopy (ES), was used. Sampling runs had been
taken for both controlled and uncontrolled sinter plants, so
emission factors were developed for both. The uncontrolled
-3 14/
emissions factor of 2x10 pounds/ton ' of feed indicates that
approximately 22 tons of cadmium result from the production of
21.94x10 tons of sinter. ' With a rotoclone plus ESP control,
the sinter windbox tested had an average emission factor for
—4 14/
two runs of 9.5x10 pounds/ton of feed. ' Assuming this
emission factor is representative of all sintering operations,
the total annual emissions of cadmium from these sintering op-
erations equal 5.4 tons yearly (11.35x10 tons of sinter ').
Total emissions from sintering equal 29.4 tons yearly.
Comparative emissions estimates will be discussed at the con
elusion of the iron and steel section, as other estimates are
not broken down by process.
48
-------
(e) Future Trends
Sinter strand production is expected to increase slightly
between 1974 and 1985. A decrease in production occurred be-
tween 1974 and 1975. However, by 1977, a recovery had been
made and production increased slightly over 1974 (33.3 MM tons
in 1974; 34.0 MM tons in 1977). Based on the historic growth
rate, it is expected that sinter production will reach 40 mil-
lion tons/year by 1985. ' However, sinter capacity will re-
main constant at 46.9 million tons through at least 1983.
By 1985, it is expected that all facilities will be in compli-
ance with control regulations, and all will employ some control
device. On this basis, cadmium emissions from sintering are
expected to equal 19 tons/year by 1985.
2. Basic Oxygen
The basic oxygen process was developed and first used in
the early 1950's. It has become a highly competitive form of
producing steel and has replaced much of the open hearth pro-
duction.
(a) Process
The basic oxygen furnace is a cylindrical steel furnace,
lined with refractory material, which has an opening at only
one end. For charging and tapping, the furnace vessel rotates
around a lateral axis. Slag is retained in the furnace and is
then tapped off by way of a tap-hole near the mouth of the fur-
ance. The charge materials used in the basic oxygen furnace
include hot metal from blast furnaces (70-80 percent), scrap,
cold pig iron, and iron oxide.
49
-------
In the process, the furnace is first tilted for the addi-
tion of scrap and hot metal. It is then brought to a vertical
position. Next, an oxygen injection lance is placed in the
furnace producing a reaction flame which is visible along the
furnace mouth. Through an overhead chute, fluxes of lime and
fluorspar are funnelled into the furnace causing the reaction
flame to rapidly decrease. Temperature readings are taken and
the refined metal and slag samples are analyzed after the car-
bon content reaches the desired level. Lastly, the furnace is
tilted to tap steel into a ladle.
(b) Emission Source and Control
Emissions of cadmium result from the melting of scrap in
the furnace. From the time the furnace is charged with the
scrap, cadmium contained in the scrap is volatilized in the
furnace.
The emissions from the basic oxygen furance are controlled
primarily by ESPs. However, approximately 40 percent of all
controlled basic oxygen furnaces use high energy venturi scrub-
bers to aid in the abatement of airborne cadmium emissions. '
Approximately 98.5 percent of all existing basic oxygen fur-
naces employ some type of air pollution control device.
(c) Emission Estimate
To determine emissions resulting from the basic oxygen
process, emissions factors were developed. For uncontrolled
furnaces, an emission factor of 4.1x10 pounds/ton of steel
was developed by assuming a reported concentration of cadmium
in the particulate of 80 ppm and the AP-42 particulate emission
factor of 51 pounds/ ton of steel. ' Production of steel in
50
-------
these facilities equaled 1.2x10 tons. ' The emission factor
of 1.2xlO~5 pounds/ton of steel for furnaces controlled by a
venturi scrubber or ESP is the average for six EPA stack tests
14/
using analysis by emission spectroscopy. ' Production of
steel at these facilities equaled 78.8x10 tons. ^ Emissions
from this source are estimated by EEA to be less than one ton/
year.
(d) Future Trends
The basic oxygen furnace is considered to have a substan-
tial growth potential through 1985. It is thought that as much
as 75 percent of the 1985 steel production in the U.S. will be
done by this process. ' Obviously, emissions will increase
(to .7 tons/year); however, the source will remain one which
does not produce over one ton of cadmium emissions each year.
3. Open Hearth
Open hearth production of steel has been decreasing stead-
ily over the past ten years due to economic and environmental
concerns. However, the process does account for 25 percent of
the steel produced and is a source of cadmium emissions.
(a) Process
A reverberatory type hearth furnace is heated alternately
by a combustion flame from either end of the hearth. At regular
intervals, the gas flow is reversed in order to recover sensi-
ble heat from the exhaust gases. This is accomplished by pas-
sing them through brick checkers which are at either end of
the furnace. At each reversal, the brick checkers are hot
enough to heat the incoming combustion air so that the high
51
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flame temperatures needed to melt and refine raw materials are
reached more readily. The furnace is charged with scrap and
heated to incipient melting by oil, gas, or tar flames which
move across the top of the hearth. Hot metal is added to the
furnace at this point. The next step involves addition of the
necessary flux and oxidizing materials to refine the mix while
it boils.
(b) Emission Source
The cadmium is volatilized when the scrap is melted.
(c) Control
An ESP is used to control about 80 percent of the existing
open hearth furnaces, while the other 20 percent are without
any kind of control. '
(d) Emissions Estimate
Open hearth emission factors have been made for both the
controlled and uncontrolled operations. A "best judgement" es-
timate of 5.78xlO~ pounds/ton of steel ' is determined to best
represent estimates between 4.07xlO~ pounds/ton of steel and
7.49xlO~ pounds/ton of steel. ' The ESP control reduces emis-
-5 -4
sions to between 2.08x10 pounds/ton of steel and 1.33x10
pounds/ton of steel. ' ' ' This recent series of stack tests
—4
using AA analysis has produced a "best estimate" of 1.1x10
pounds of steel. From this, and a production figure of
29.06x10 tons, ' it was determined that controlled open
hearth facilities contribute two tons of cadmium into the
atmosphere each year. Uncontrolled emissions, with a production
level of 7.64x10 tons, ' equal approximately 22 tons/year,
resulting in a total of 24 tons of cadmium emissions yearly.
52
-------
(e) Future Trends
As has been stated, the open hearth is not environmentally
and economically competitive with other steel-making processes.
Since 1965, open hearth steel production capacity has dropped
from 110.82 MM tons/year to 37 MM tons/year. ' It is expected
to continue declining through 1985 to 21.1 MM tons/year. ' No
new open hearth facilities are planned, therefore, NSPS will
have no bearing upon the control of the open hearth facilities
or amount of their emissions. Emissions, assuming that 100
percent of the open hearths will use some control device, are
estimated to be about one ton/year by 1985.
4. Electric Arc
The electric arc furnace, the fourth method by which steel
is produced, has enjoyed steady growth since its initial install-
ment in 1906. At present, it accounts for the production of
approximately 27.3 MM tons of steel each year. The process
allows for the production of a large variety of objects and is
flexible in operation, which accounts for its growing popular-
ity.
(a) Process
Steel scrap is the principal material used for feed in
electric arc steel-making, while iron sponge is occasionally
used as a portion of the feed. Scrap is processed in a furnace
which is shaped like a cylindrical shell, shallow in depth,
with a large diameter. A removable roof on the shell allows
for the insertion of three graphite electrodes. High perfor-
mance refractories completely line the shell and roof.
53
-------
Steel-making is accomplished in a series of heats, each
producing a certain tonnage of some form of steel. Each cycle
begins when a partial charge is loaded into the top of the fur-
nace, the roof is closed, and the electrodes are lowered into
the furnace. The electrodes are placed so that the electric
current produces an arc between them and the charge. After
the melting of the partial charge, the remainder is added and
melting continues to the end of the heat. The entire process
usually requires three to four hours for completion. When the
process is completed, the heat is placed in a transfer or
teeming ladle, while the slag is dumped into a slag pit.
The process is used to produce a large number of different
steel products such as structural steel, specialty alloys, tool
steels, super alloys, and stainless steels.
(b) Emissions Sources and Control
The melting process which the steel scrap undergoes in the
electric arc produces the resulting cadmium emissions. Because
the primary feed for the arc furnace is steel scrap, this pro-
cess produces the largest amount of cadmium emissions of any of
the steel production operation. (Sintering, with a slightly
higher amount of cadmium emissions, is a raw materials process-
ing operation.) Control is accomplished with the use of a bag-
house and the occasional use of a scrubber or ESP. Approxi-
mately 90 percent of all electric arc furnaces employ some
14/
method of control. '
(c) Emissions Estimate
It is estimated that the electric arc furnace emits
3.4xlO~ pounds of cadmium/ton of steel. This ''best judgement"
estimate was developed from estimates between 2.7xlO~ pounds/
54
-------
ton of steel and 5xlO~ pounds/ton of steel by assuming a par-
ticulate cadmium concentration of 735 ppm from EPA ES stack
test results, '' and the AP-42 particulate emission factor
of 4.6 pounds of particulate/ton of steel. Using this emission
factor, and a production figure of 27.3x10 tons, EEA estimated
that at a 90 percent control efficiency, cadmium emissions from
this process equal approximately 4.6 tons/year.
(d) Future Trends
The electric arc furnace is a steadily growing method of
producing steel. The increase in the electric arc is a result
of several factors which include the viability of the "mini-
mill" concept, the applications possible for high-intensity arc
furnace technology, larger amounts of scrap available due to
growth of the basic oxygen furnace coupled with decline of the
open hearth, and increasing economic viability of direct ore-
reduction processes. Therefore, an historic growth rate was
used to project that there will be an increase of about 11 MM
tons produced by the electric arc through 1985. Emissions will
increase somewhat; however, all electric arcs will be control-
led in some way. NSPS standards will have some effect upon the
process, as expansion seems of existing plants quite likely.
5. Total Iron and Steel Emissions
To compare EEA's iron and steel emission estimates with
estimates of other studies, it was necessary to total all pro-
cesses.
6. Total
EEA's emissions estimate of 190 tons/year is not in agree-
ment with most others (Davis—1,000; ' Mitre—IjOOO;11' EPA—
78; ' GCA—400;2// and Sargent—H.56^). Control technology
' 55
-------
assumed was based on the Temple, Barker, and Sloane steel study
(1976) , which was unavailable at the time previous estimates
were made. Several emission factors were also based upon data
previously unavailable. It is possible that a higher degree
of control technology was assumed here. Production figures
could also vary among the sources. However, the cause of the
wide variation in estimates is not fully understood.
E. Secondary Smelting
Secondary smelting processes involving zinc, lead, and cop-
per are not viewed as large emitters of cadmium when each is
viewed as an aggregate (all zinc smelters; all copper; all lead).
Each metal will be dealt with individually in the following
discussion.
1. Secondary Zinc
(a) Process
Of the three secondary smelting processes, the zinc pro-
cess releases the largest amount of cadmium into the air. Zinc
can be melted, "sweated," or vaporized in processing. To re-
cover the zinc from scrap, sweating is the most common proce-
dure. The furnaces employed to carry out this process include
rotary, reverberatory, or muffle furnaces. In zinc melting,
the scrap is combined with ingot and rejects, and is melted to
create a molten bath. After light scrap is added to the bath,
it is heated to the correct pouring temperature and poured.
The zinc vaporization is carried out in retort furnaces to re-
claim zinc from alloys and to recover zinc from its oxide
(among other processes). Distillation and muffle furnaces are
56
-------
used to separate zinc from the alloy which is then processed
and converted to zinc metal.
(b) Capacity
A total production figure for the industry (182,665 tons in
1974, ') is possible to obtain but no figures of individual
plant capacity or production are available.
(c) Source and Control
The source of cadmium emissions from all three processes is
the melting of the material at high temperatures. In preparing
the scrap material for charging, no control device is used or
needed. Sweating furnaces are equipped with an afterburner and
a baghouse, while distillation furnaces are equipped with bag--
houses. Only 20 percent of the sweating furnaces use control
devices, while almost all distillation furnaces employ devices.
(d) Emissions Estimate
Cadmium emissions from zinc secondary smelting operations
are small. This is due to the fact that most of the cadmium has
already been volatilized during primary smelting.
Uncontrolled emission estimates between 8xlO~ pounds/ton
_O O 1 Q 1 Q /
of zinc and 1.4x10 pounds/ton of zinc produced ' ' were
_2
found in the literature. A "best judgement" factor of 1x10
pounds/ton of zinc produced was then derived from the mass
balances. The 1974 production figure was used to compute an
emissions estimate of less than one ton of atmospheric cadmium
resulting from the process yearly. EPA ' estimated emissions
2/
from this process to be two tons/year, as did GCA. ' Sargent
combined all secondary non-ferrous metal processing to obtain
an emissions estimate of 2.4 tons yearly. '
57
-------
(e) Future Trends
Production of zinc through secondary smelting is expected to
increase slightly through 1985 to 223,000 tons according to
197
the Bureau of Mines forecast. ' There is no reason to assume
a dramatic increase or decrease in production. Cadmium emissions
would thus increase slightly to over one ton/year, but emission
control will improve so that the increased production as a
whole should not cause a large net increase in emissions.
2. Secondary Lead
(a) Process
Secondary lead smelting is a process from which cadmium
emissions are derived. Lead automobile storage batteries, lead-
sheathed cable and wire, aircraft tooling dies, type-metal
drosses, and lead dross and skims are the materials most common-
ly sweated to obtain lead. To process materials with a small
percent of the metal, a rotary furnace, or sweating tube, is
usually employed. A reverberatory-box type furnace is used when
dealing with material of high lead content.
Blast furnaces are also used frequently in secondary smelt-
ing of lead storage batteries. Lead is charged into the furnace
at the beginning of the operation in order to provide molten
metal to fill the crucible. Limestone and iron flux float on
the top of the lead to inhibit its oxidation. The molten metal
is poured when proper conditions are reached.
(b) Capacity
As with zinc, capacity of individual plants could not be
otained for this study. However, 1974 total production was
698,698 tons.12/
58
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(c) Emissions Source and Control
Airborne cadmium emissions emanate from the melting
process during which cadmium is volatilized. The control
measure used with both reverberatory and blast furnaces is
generally a baghouse, occasionally in combination with an
ESP.1/
(d) Emissions Estimates
The amount of cadmium produced by secondary lead smelters
has not previously been estimated. Emission factors for this
process were developed from EPA stack testing results. Three
factors for three different combinations of furnace type and
control technology were used to compute emissions estimates.
However, because of difficulty in obtaining production data,
the most conservative emissions factor of 2xlO~ pounds/ton of
14/
lead was used. ' Combined with the production figure for
secondary smelters, the emission factors produce a relatively
low estimate of total emissions very low (less than one ton).
(e) Future Trends
The production of secondary lead is expected to increase
through 1985. It is felt that the growth of this sector of
the lead industry will largely account for the growth of the
entire industry. However, until the long-term effects of both
the OSHA regulations and EPA rulings are determined, secondary
producers will be reluctant to increase capital expenditures
for new plants and equipment. This indicates that the impact
of NSPS will be minimal at best. At a growth in production of
3.26 percent per year, ' emissions are expected to increase
but remain under one ton/year.
59
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3. Secondary Copper
Scrap serves as the primary feed for most secondary
copper operations. The scrap received usually contains many
impurities including cadmium. During the processing, which is
discussed below, these impurities are removed and copper metal
is cast for re-use. *''/*'''
(a) Process
Scrap can be processed mechanically or by a pyrometallurgi-
cal process. At medium temperatures, sweating is done to remove
metals which have a low melting point. Burning removes insula-
tion which was not removed mechanically from copper wires. To
remove excess cutting fluids from machine shop chips and borings,
vaporization occurs in a heated rotary kiln. The blast furnace
produces a product called "black copper" which is a concentrated
material. Concentration is produced by taking scrap and charging
it at the top of a vertical furnace, together with coke, a reduc-
ing agent and a fluxing material. The concentrated material
plus some slag are drawn out at the bottom of the furnace.
After the scrap is processed, it undergoes smelting and re-
fining, melting, and alloying in a variety of furnaces, including
the reverberatory, the rotary, or the crucible. The choice of
one over the other is dependent upon the quantity of scrap to be
melted and the type of alloy to be produced. The reverberatory
and rotary furnaces are direct-fired furnaces in which the hot,
high-velocity combustion gases are in direct contact with the
metals in the charge. It is thus difficult to effectively
capture the emissions from these types of furnace with a hood.
60
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During charging, all the scrap material is usually not
placed in the furnace at one time due to the large quantities
involved. After charging, the melting process occurs. The
burners are set to ensure a very rapid melt-down, and additional
oxygen may be added at this time. Refining, the next process
which the metal undergoes, involves fluxing the molten bath of
metal to cause selective oxidation. In alloying, virgin metal
or specialized scrap may be added to modify the final product
of the melt. The last step is the pouring of the molten metal
from the furnace into a mold. This can be done by tapping the
furnace directly to an automated mold line, or into a ladle
from which it is transferred to a mold line.
(b) Source of Emission and Control
Almost all processes in secondary copper smelting produce
some emissions of cadmium. Sweating involves a very small loss
of metal fume, as does burning. However, the rotary kiln which
vaporizes copper and cadmium can cause a large amount of emis-
sions. Usually, afterburners are employed to complete combustion
and decrease emissions. The processes which result in combustion
leading to air-borne cadmium emissions include those involving
the blast furnaces, direct fire furnaces, charging, melting, re-
fining, and alloying. During wire burning, no control devices
are employed. However, in sweating, an afterburner and baghouse
are used. The blast furnace is equipped with a baghouse, while
the reverberatory and rotary furnaces both are equipped with a
hood and baghouse.
(c) Emission Estimate
Approximately 38 tons of cadmium emissions result each
year from secondary copper processing. Emission factors estimates
range from a minimum of 2.6 pounds/ton of copper scrap to a
61
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28/
maximum of 4.0 pounds/ ton of copper scrap. ' The factor
used (three pounds/ton of copper) is the average of two mass
balances. A 1974 production figure of 513,308 tons of copper
12/
was also used. ' EEA's estimate is lower that all others
which have been made up to this point (Davis—125; Mitre--
125;11/' EPA—65; 2/ GCA—702/') . This is because a greater
number of control devices and a greater efficiency of control
were assumed by EEA (90 percent particulate control efficiency
for the nearly universally employed baghouse). The Sargent
figure of 2.4 tons of cadmium released per year from secondary
non-ferrous metal processing is lower than any of the others.
(d) Future Trends
The Bureau of Mines predicts that production of secondary
copper will increase five percent each year to 1985. ' Using
1975 as a base, this would mean 800,000 tons of secondary copper
would be produced by the industry in 1985. Emissions would also
increase substantially through 1985 to 60 tons.
F. Manufacturing
The production of paint pigments, plastic stabilizers, and
nickel-cadmium batteries result in cadmium emissions into the
air.
1. Cadmium Pigments
Cadmium compounds, principally the sulfides and sulfoselen-
ides, are used as coloring agents in paints and plastics. The
sulfide compounds are used to impart colors of yellow to orange,
while sulfoselonide colors range from light red to dark maroon.
62
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In order to "stretch" the pure cadmium pigments, white barium
sulfite is often mixed with the pure pigments to create "cadmium
lithopones."
(a) Process
The use of these pigments is widespread due to their
stability in light at relatively high temperatures in various
chemicals, in various weather conditions, and in moisture.
This makes use of the cadmium pigments in plastics which require
high temperature molding extremely practical. Other uses
include artist's colors, rubber, and printing inks.
The preparation of these pigments does cause release of
airborne cadmium emissions. By heating cadmium and sulfur (Cd
HG3.t
+ S > CdS) , cadmium sulfide is produced. It can also be
made by precipitating an aqueous solution of soluble cadmium
salts and soluble sulfides or H2S. Color variations (yellow to
orange) are produced when the temperature of the H_S solution
is altered (a cold acid solution yielding yellow, and the hot
solution producing orange). In preparing cadmium sulfoselenide
pigments, selenium is added to solutions of barium salts. This
solution is, in turn, reacted with CdSO4. To remove any unre-
acted selenium, the final product is calcined with excess sul-
fur. In all of the above processes each must contain a calcin-
ation or drying step. Without calcination, the pigments would
not be dry and would be impossible to compound.
(b) Emissions Source and Control
Any loss of cadmium to the environment during the manufac-
ture of cadmium pigments originates from the dust which is
63
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produced during calcination. However, all facilities which are
involved in pigment production have installed baghouses to
minimize emissions.
(c) Emissions Estimate
The emissions factor used to calculate cadmium emissions
was the mass balance estimate developed by Davis and cited by
8/
Anderson. A factor of 15 Ibs/ton of cadmium charged is sug-
gested as the emission factor for this process. With production
of 1,212 tons in 1974, ' nine tons of cadmium/year are released
into the air. Davis, Mitre, and GCA all estimate emissions from
this process to be 11 tons/year. The estimates of seven tons/
year by the EPA and 9.5 tons/year by Sargent are in closer
agreement with EEA's than other figures.
(d) Future Trends
The use of cadmium pigments is expected to increase slowly
during the near future to 1,560 tons, which will slightly increase
emissions from this source (11.3 tons). Substitutes for cadmium
pigments are available (zinc, lead, and barium chromates). The
yellow cadmium-based dye used in printing inks has proven extreme-
ly difficult to bleach on paper recycling operations. However,
it is expected that cadmium pigment production will steadily
increase (two percent growth rate). '
2. Plastic Stabilizers
In order to protect plastics from degradation by heat and
light, it is necessary to add stabilizers to them, especially to
PVC and related polymers. Most plastics which are destined for
use outdoors are stabilized in this manner.
64
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(a) Process
Stabilizers must counteract the loss of acid, usually HC1,
by the PVC because this is usually the first step in degradation
of the plastic. Cadmium stearates, which are long, straight-chain
organic esters, will react with the HCl to produce weak organic
acids and ionized cadmium chloride. When used with no other
additives, this stearate successfully lends the desired heat
and light stability to the plastics. When combined with
barium compounds, epoxides, or organic phosphates, the stearate
is even more effective. Because it is the least expensive of
the available cadmium plastic stabilizers, it is also the most
popular. Other compounds used include cadmium laurate and
cadmium recinoleate.
(b) Emission Sources and Control
Any airborne cadmium emissions which result from the pro-
cessing of plastic stabilizers originate from the handling of
pulverized cadmium oxide. The cadmium oxide is used to prepare
cadmium soap or other organic stabilizers. The procedure in-
volving the mixing of the prepared compound with the plastic is
not believed to produce any appreciable emissions. All cadmium
stabilizer producers use baghouses to control the emissions
resulting from the process. '
(c) Emissions Estimate
It is believed that the stabilizer industry is responsible
for very little of the total cadmium in the air. Using an
7 8/
emissions factor of six pounds/ton of cadmium charged '
developed by EPA from a mass balance analysis and a production
figure of 991.8 tons, EEA estimates that three tons of cadmium/
year are released into the air in the production of stabilizers.
Other estimates, including those made by Davis, Mitre, and GCA
65
-------
2/
agree with that of EEA, while EPA ' estimates one ton of
cadmium a year from the stabilizer process and Sargent
estimates a release of 2.9 tons yearly.
(d) Future
Because of ever-increasing FDA bans on the use of the cad-
mium compound plastic stabilizers, particularly for use in
plastic food wrappings, a constant annual production is pro-
21/
jected for this product. ' Although figures show a slight
increase (due to a small market recovery after 1973-1974),
emissions are estimated to remain constant through 1985. The
development of a calcium-zinc stabilizer, which can equal cad-
mium stabilizers in performance and cost, has also caused a
decrease in the use and production of the stabilizer.
3. Batteries
The nickel-cadmium battery is perhaps the only product from
which cadmium can be recovered. Developed prior to 1900 by
Jungar, it is superior to other batteries in efficiency and
longevity. However, during processing, relatively small amounts
of the material are released into the air.
(a) Process
The "pocket" electrode is used most frequently in the
nickel-cadmium battery to form the cadmium plate. This elec-
trode is produced by pulling active materials (cadmium sponge)
into perforated pockets on a nickel steel frame. Active ma-
terials, such as the cadmium sponge, react with the electrolyte
solution of the battery to produce a charge.
There are two methods used to prepare the active materials.
In one, powdered cadmium or a cadmium compound is dry-mixed with
66
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an expander, often iron, and then inserted into the pockets.
Electrolytic coprecipitation of cadmium and iron from an acid
electrolyte also produces an active material to be inserted into
the electrode. This process requires filtering, washing, dry-
ing, ball-milling, and blending of the precipitate to produce
the final product. The electrodes are then filled with one of
the mixtures by insertion of machine-made brickettes or loose
dust. To prevent dusting during this process, petroleum oil is
often added in small amounts.
Recently, plates which have the cadmium deposited into them
have been used successfully in cadmium-nickel batteries. The
production of the plate can occur in four ways, all of which in-
volve depositing cadmium, cadmium oxide, or cadmium hydroxide
onto a nickel screen or onto a pourous nickel plaque. The
methods to accomplish this include:
• Soaking the plate in cadmium formate solution
prior to thermal decomposition in air;
• Electro-deposition from a solution of a
soluble cadmium salt, most often nitrate;
• Soaking in cadmium nitrate solution prior
to reduction in an atmosphere of hydrogen;
and
• Forcing a paste of active material into the
nickel support.
At some point, either after or before the battery is assem-
bled, the electrodes are subjected to the "formation" treatment.
This entails submitting the electrodes to several charge-dis-
charge cycles. This serves to remove impurities and loose par-
ticles.
67
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(b) Emissions Source and Control
There are several potential sources of airborne cadmium
emissions from the production of the nickel-cadmium battery.
All procedures which involve dry powdered cadmium and cadmium
compounds, and the reduction and thermal decomposition steps
which require high temperatures contribute to the emissions.
During production of active materials, cadmium is released into
the air. With adequate control, however, this industry should
not prove to be a source of a large amount of airborne cadmium.
Controls used by this industry are unknown at this point, both
in kind and number. ' Adequate techniques, such as baghouses or
ESPs, are available to the industry but are considered to be
extremely expensive.
(c) Emissions Estimate
EEA estimates that, based upon a mass balance emission
7 8/
factor of two pounds/ton of cadmium charged, ' and a produc-
tion figure of 628.14 tons, ' less than one ton of emissions
per year are released by the process. With the exception of
Sargent (0.7 tons/year), ' all others did not report a specific
emissions estimate from battery production.
(d) Future Trends
The EPA estimates that the amount of cadmium used in bat-
teries in 1985 will increase between 15-20 percent, ' while the
Bureau of Mines predicts only small increases. ' The large in-
crease predicted by EPA is based upon several factors. These
batteries are also used in calculators and portable garden,
power, and hobby tools, all of which are expected to increase in
demand due to relatively low prices and increasing popularity.
68
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EEA's estimated future emissions from the production of nickel-
cadmium batteries are based on EPA's estimated emission factors
and indicate that approximately two tons/year may be released
from this industry.
G. Fossil Fuel Combustion
Cadmium is found in fossil fuels, and therefore, these
fuels are a potential source of cadmium emissions. It has been
determined that coal-fired and oil-fired power plants, fuel oil,
diesel oil, and gasoline are all responsible for some airborne
cadmium.
1. Coal-Fired Power Plants
The coal-fired power plant represents a source of cadmium
;mi:
lected.
(a) Process
air emissions which is small unless the fly ash is not col-
21/
To produce power, steam is generated using a fossil fuel.
The fuel and a stream of air which has been preheated are di-
rected to a furnace or a series of burners where combustion
occurs. Because the process is not carried out under perfect
conditions, incomplete combustion usually results. Incomplete
combustion and the incombustible nature of some fuel constitu-
ents cause pollutants, such as fly ash, to be generated by the
process. The heat from the combustion chamber heats water which
is contained in a series of pipes in a boiler and generates
steam.
(b) Source of Emissions and Control
Emissions of cadmium particulates from coal-fired power
plants originate from the combustion of the coal. Impurities,
69
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such as cadmium, which exist in the coal, are volatilized, and
condense on the particulate matter or fly ash. Devices used
to control the emission of fly ash include ESPs and fabric
filters. ' Approximately 97 percent of the coal-fired power
plants employ one of the above control devices. /
(c) Emissions Estimate
The emissions from coal-fired power plants were estimated
using emission factors developed from stack test results re-
ported in several sources and the total coal consumed by such
plants. These stack tests resulted in factors ranging from
lxlO~4 to IxlO1 pounds/ton of coal (uncontrolled)14'22'23/ and
from lxlO~ to 7xlO~ pounds/ton of coal (controlled with
ESP).2'8'10'14/ Best estimate factors were then developed by
taking geometric means of the stack test. It was found that
the emissions due to uncontrolled coal-fired power plants
buring 3.913x10 tons of coal, ' with an emissions factor of
lxlO~ pounds/ton of coal equals approximately 196 tons. If
all facilities were controlled with an ESP or its equivalent,
an emission factor of 6xlO~ pounds/ ton of coal would be used
together with the tonnage to estimate that 12 tons of cadmium
would be released yearly. The controlled estimate is much
more likely, as nearly all coal-fired power plants employ high
efficiency particulate control equipment. Other emissions
estimates have treated fossil fuel combustion in total, thus,
a comparison will be made on the basis of total emissions.
It was found that the emissions due to power plants (if all
were uncontrolled), with an emission factor of 1x10 pounds/ton
of coal,14'22'23/ would be 196 tons yearly. If all facilities
were controlled with an ESP or its equivalent, and an emission
factor of 6x10 pounds/ton of coal, ' ' ' / is assumed, they
would emit seven tons of cadmium yearly. The controlled
70
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estimate is much more likely, as nearly all coal-fired power
plants employ high efficiency particulate control equipment.
(d) Future Emissions
Studies indicate that coal will become a more important
source of power in the near future, and its use will increase,
especially if the National Energy Plan is implemented. There-
fore, uncontrolled emissions from this source will become great-
er. However, with increased control and improved technology,
24/
emissions will increase only slightly.
2. Oil-Fired Power Plants
Oil-fired power plants are similar to coal-fired power
plants in terms of process and emissions. These plants produce
a slightly smaller amount of cadmium air emissions than the
coal-fired variety.
(a) Process
For a description of the steam generation process, refer to
coal-fired power plants. The major difference between coal-
and oil-fired plants is that the firing mechanism and equipment
required for oil are greatly simplified.
(b) Emissions Source and Control
Thermal processes are responsible for the cadmium emissions
in almost every source, and oil-fired power plants are no excep-
tion. The combustion of oil to create steam releases small
amounts of cadmium impurities into the air. Ninety-nine percent
of the power plants are controlled with cyclones.
71
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(c) Emissions Estimate
The emission factor derived from EPA's emission test re-
sults using ES analysis is 9xlO~ pounds/gallon for a plant
147
with ESP control. ' The range of estimates fell between
7.1xlO~ and 4_4xlO~ pounds/gallon. Combined with an oil
usage figure of 2.072x10 /gallon, ' this produces an estimated
nine tons of cadmium a year resulting from oil-fired power
plants.
(d) Future Trends
Although oil is expected to increase in price and become
increasingly difficult to obtain, usage in the next few years is
54 /
expected to continue to rise. ' Emissions are projected to
rise to approximately 20 tons/year.
3. Other Fuel Oil Combustors
Fuel oil, including residual and distillate fuels, are used
in various boilers or burners to supply heat to the residential,
commercial, and industrial sectors. The process of operation
is similar to the combustion which occurs in the boiler of an
oil-fired power plant, but usually on a much smaller scale.
(a) Emission Source and Control
The incomplete combustion of the oil and the impurities in
the oil result in emissions of various kinds, including cadmium.
There are no controls on these sources of cadmium emissions.
(b) Emissions Estimate
Estimates of cadmium emissions indicate that heating oil is
not a large source. An emissions factor of 3xlO~ pounds/gallon '
for residual fuels was developed from an average of six reported
cadmium concentrations in the fuel, assuming that all cadmium
72
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was emitted. Distillate fuel emissions were calculated using
the diesel oil emissions factor of 7x10 pounds/gallon of oil
consumed, which is a best judgement figure based upon factors
ranging from 6xlO~ pounds/gallon to 2x10 pounds/gallon. ' ' ' '
Residual fuel consumption equaled 321.2x10 barrels, and dis-
tillate fuel consumption equaled 613.9x10 barrels. '
(c) Future Trends
The future consumption of heating oil will rise slowly
through 1985 to 900x10 barrels. To determine residual and dis-
tillate usage, proportions were assumed to be equal to that of
1974. Of total fuel consumed, residual fuel accounted for 60
percent and distillate for 40 percent. Emissions are 30.5
tons/year based on consumption figures of 644.6x10 barrels of
distillate fuel and 336.3x10 barrels of residual fuel in 1985.
4. Diesel Oil
(a) Process
Diesel oil, which is burned in the diesel engine, is used
by some automobiles, trucks, and other motor vehicles. An un-
regulated flow of air is fed into the engine and mixed with the
fuel. This mixture reaches the cylinder or combustion chamber,
is compressed, and ignited. The injection of the highly-pres-
surized gases into the cylinder causes a sudden reduction in
pressure, in turn, creating air temperatures which cause the
ignition. The energy of the burning mixture moves the pistons,
As a result, cadmium emissions from residual combustion
equaled 23.1 tons in 1974, emissions from distillate com-
bustion equaled 8.4 tons in 1974, bringing 1974 emissions
to a total of 31.5 tons.
73
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and the pistons' motion is transmitted to the crankshaft that
drives the vehicle. The burned mixture then leaves the car
through the exhaust pipe.
(b) Emission Source and Control
The emission source is the thermal process which causes
combustion of the oil itself. The emissions are actually re-
leased through the exhaust pipe, which accounts for almost 100
percent of the diesel engine's emissions. Control of cadmium
emissions from this source is not practiced.
(c) Emission Estimate
Diesel fuel oil emits cadmium at a rate of between 6xlO~
pounds/gallon and 2xlO~6 pounds/gallon.8'10'18'21/ A best
judgement figure, which assumes the emission of all the cadmium
in the fuel (as measured by ES), is 7xlO~ pounds/gallon. With
3 397
a consumption figure of 11,179,686x10 gallon, ' and the "best
judgement" factor, EEA estimates that less than one ton yearly
is emitted.
(d) Future Trends
Diesel oil consumption is expected to rise by approximately
38/
four percent each year to 1985. ' Emissions from the combus-
tion of the fuel are estimated to increase somewhat to 5.25
tons/year.
5. Gasoline
To complete the discussion of fossil fuels which release
cadmium emissions during combustion, gasoline must be considered.
The process which actually releases the cadmium is the combus-
tion of gasoline within the engine. Therefore, a brief discus-
sion of this will be included.
74
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(a) Process
In the conventional automobile engine, a mixture of fuel
and air is fed into a combustion chamber, or cylinder, by the
carburetor, compressed, and ignited by a spark from a spark
plug. The pistons are put into motion by the energy released
from the burning mixture. Also released are certain particulates,
including cadmium. The emissions pass out of the car through
the exhaust system.
(b) Source of Emissions and Control
The source of emissions, as noted above, is the actual
burning of the fuel which causes the volatilization of cadmium.
(c) Emissions Estimate
The emission estimate for gasoline is based on an emission
—8
factor of 2x10 pounds/vehicle mile traveled in one year.
This factor assumes that all the cadmium in the fuel is emitted
and that the vehicle operates at 15 miles/gallon. This best
judgement factor was obtained from literature which listed
—11 -8
emission factors between 6.3x10 pounds/VMT to 4.5x10
pounds/VMT.25'26'27'28'29/ Total vehicle miles traveled by
6 39/
cars and motorcycles is estimated at 1,330,074x10 , ' producing
estimated aggregate cadmium emissions of 13 tons/year.
(d) Future Trends
It is expected that vehicle miles traveled will steadily
increase in the coming years. Even though the vehicle
miles traveled is expected to rise, emissions are not projected
to increase substantially.
75
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6. Summary
EEA estimates that the five fossil fuel combustion processes
release a total of 40 tons of cadmium into the atmosphere each
year, assuming controlled coal-fired power plants. This figure
2/
is lower than estimates by GCA (250 tons/year); ' EPA (198
tons/year); ' and Sargent (130 tons/year), ' due to more stringent
control technology assumptions.
H. Miscellaneous
Several cadmium emission sources contain very small amounts
of cadmium which are not intentionally part of the product.
Fungicides, phosphate fertilizers, rubber tires, and cement all
contain cadmium. Release of cadmium emissions from these
sources occurs in the production and in the use of the product.
1. Fungicides
The type of fungicide which is used primarily on golf
courses contains a small amount of cadmium. When the fungicides
are applied to the courses, usually in liquid form, some cadmium
loss is experienced. This loss is dependent upon several
factors, including spray particle size and atmospheric conditions.
(a) Emissions Estimate and Control
Emissions from this source are minimal (less than one ton/
year). In order to develop this estimate, a production figure
9/
of 59,800 tons was combined with an estimated emission factor
—5 8/
of 1x10 pounds/ gallon. No control devices are used in
application of the fungicides.
76
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(b) Future Trends
Future growth in production of this product is difficult,
9/
if not impossible, to project. ' Many factors enter into the
future of fungicide production. Leisure time is increasing, and
"planned" communities which include recreation facilities are
becoming a popular place in which to live and recreate. This
would indicate that production would increase as more golf
courses would require fungicides. Fungi may become immune to
cadmium-containing fungicides, which would force a change in
type of fungicide used. This would cause a decrease in emis-
sions. Each year many variables, including weather conditions
and infestation rate, also affect the use of the fungicides.
EEA has used an historic growth rate to determine that emissions
from fungicides will not increase greatly through 1985.
2. Fertilizers
Phosphate and superphosphate fertilizers also contain a
small amount of cadmium. Associated with phosphate rock are a
small number of impurities, one of which is cadmium. The cad-
mium remains with the phosphorus in processing and becomes a
contaminant in both phosphate and superphosphate fertilizers.
(a) Emissions Source, Control and Estimate
The cadmium emissions are released during application of
the fertilizer, but not during processing of the material.
There are no control methods employed, as there is an inadver-
tent loss of the material. The emissions estimate is based upon
—4
an emissions factor of 2x10 pounds/ton for superphosphate
fertilizer (from an EPA esimtate), ' ' ' coupled with the
production figure of phosphate and superphosphate fertilizers
77
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3 9/
which equals 85.35x10 tons. The cadmium emissions from both
phosphate and super-phosphate fertilizers are a small portion
of the total emissions (less than one ton). Other estimates
include those by Davis, ' GCA, ' and Sargent, ' which are all
under one ton.
(b) Future Trends
The future of phosphate and superphosphate fertilizers is
uncertain in much the same way as that of fungicides. The
industry experienced moderate increases in 1977 after lows in
g/
1974-1975. ' In 1974, phosphate fertilizers were unavailable
due to low production, while in 1975, pricing prevented farmers
from making use of the fertilizer. Farmers who had done without
the fertilizer in the previous years because of high prices
found that a decreased use of fertilizer did not decrease crop
9/
yield. ' In 1976, production decreased due to oversupply in
1975 (addition of 1.5 million ton capacity plant) and decreasing
9/
use. Growth of the industry will be slow to moderate, with a
projected four to five percent increase in production through
1985.9/
3. Rubber Tire Wear
Rubber tire wear is believed to be a source of several
types of gaseous emissions and particulate matter emissions,
including cadmium. The curing process in the rubber industry
employs zinc oxide as an activator through which the cadmium
enters rubber processing. As the tires are worn down during use,
cadmium is released into the air. There are no controls employed,
Several sources were used to estimate an emission factor of
_Q
8x10 pounds/VMT, assuming a mix of the types of rubber with
various cadmium contents in the tire population. ' ' ' '
78
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39/
Using total vehicle miles traveled per year, ' it was determined
that rubber tire wear contributes a small amount of cadmium to
the atmosphere (five tons/year). As mentioned in the discussion
concerning gasoline, vehicle miles traveled will increase,
causing emissions from rubber tires to also increase. '
4. Motor Oil Consumption
Motor oil combustion also contributes to cadmium emissions.
Some oil is burned in the engine causing volatilization of
cadmium and its release into the air. No emissions control is
_Q
practiced. The emission factor of 2x10 pounds/VMT, reported
by Anderson (1973) ' and Deane (1976), ' coupled with vehicle
miles traveled for passenger cars only (1,028,121x10 ), '
indicates that the combustion of motor oil does not contribute
large amounts of cadmium into the air (one ton/year). In es-
timating future cadmium emissions from this source, the same
projection used for gasoline and rubber tire wear was employed
and indicates that through 1985, emissions from this source will
increase only slightly.
5. Cement Plants
In the manufacture of cement, cadmium is released though ir.
rather small amounts. Cement is a non-metallic mineral product
composed principally of lime and silica, with alumina and ferric
oxide acting as fluxing materials.
(a) Process
Cement is produced in one of two ways, either by the wet.
process or the dry process. The four basic steps in the
79
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production process include quarrying and crushing, grinding and
blending, clinker production, and finish grinding and packaging.
The materials which enter the kiln at the top end are dried
by combustion gases which are passed through the kiln counter-
current to the materials. The revolving of the kiln causes the
raw materials to fall toward the clinkering zone as the carbon
dioxide is removed from the calcerous material (the material
containing cadmium carbonate which is the major constituent of
limestone). After the partially-fused production clinker is
cooled in the clinker cooler, gypsum or water is added and the
mixture is ground in a ball and tube mill to the necessary
fineness.
(b) Emission Source and Control
Limestone, which serves as a raw material in cement produc-
tion, contains a small amount of cadmium. When it is processed,
cadmium is released. Control measures used to prevent cadmium
from becoming an airborne pollutant include cyclones, with or
without ESPs, and baghouses. '
(c) Emissions Estimate
There are many emission factors which apply to the various
methods and steps of producing cement as determined by EPA ES
stack testing. In estimating emissions, the most conservative
dry process factor was used by EEA because an increasing number
of plants are using the dry process. An emission rate of
2.6xlO~ pounds/ton of feed, ' together with the appropriate
3 9/
production figure of 81,210x10 , indicated that less than one
ton of cadmium a year is released from the cement process.
Previous studies have not estimated emissions from this process.
80
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(d) Future Trends
The production of cement decreased between 1974 and 1975
due to several plant closings and slow housing starts. However,
in 1976, home construction increased. Although there has been
little plant expansion, or construction of new plants, it is
felt that an annual (compounded) rate of 3.2 percent growth will
continue through 1985. Because no new plants are planned,
NSPS will not affect emissions, which, notwithstanding the
increased production, will remain well below one ton.
I. Incineration
Incineration is a source of cadmium emissions due to the
cadmium in the materials burned. These materials include
plastics which contain cadmium stabilizers, objects painted
with a cadmium-pigmented paint, and scrap metal coated with
cadmium. Both municipal incinerators and sewage sludge incinerators
emit cadmium into the air.
1. Municipal Incinerators
The municipal incinerator is a major source of airborne
cadmium emissions, emitting approximately 131 tons of cadmium
per year. The following description of the process of the muni-
cipal incinerator assumes that there is no resource recovery and
that volume reduction is the prime motivation.
(a) Process
First, the refuse is deposited in a receiving area which is
essentially a pit up to 30 feet deep, 100 feet long, and 20 feet
wide. From there, overhead cranes remove the refuse from the
pit and deposit it in a feed hopper, which delivers refuse onto
the combustion grates at a constant rate.
81
-------
The most expensive part of the combustion plant, the grates,
serve to transport refuse through the primary combustion chamber
and simultaneously insure that the maximum refuse surface is
directly in contact with fire. Many types of grates are used to
accomplish this; among the most popular are moving belts, reci-
procating grates, and drum-type rollers.
The refuse is carried into the primary combustion chamber
and is burned. Here, in a conventional refractory furnace, 150
to 200 percent excess air is supplied in order to prevent refrac-
tory materials from erosion by high temperatures. A result of
this process is a large amount of exhaust gas production. This
necessitates the use of a secondary chamber, in which the exhaust
gases are subjected to additional combustion. The gaseous emis-
sions are then discharged through the chimney stacks.
The resultant solid material and all material which remains
unburned is deposited into a residue bin which empties directly
into trucks. The trucks then carry the waste to a landfill.
(b) Source of Emissions and Control
Emissions result from the combustion of plastics, paint
pigments, and metal scrap which subsequently causes the volatil-
ization of cadmium in the three items. Control devices most
commonly used to combat the particulate emissions are wet scrub-
bers. Bag filters, or ESP's, are used occassionally. Approxi-
mately 83 percent of the municipal incinerators use some sort of
emission control, while 17 percent employ none. '
(c) Emissions Estimate
EEA's emissions estimate was made using an emissions
factor from some very recent source testing (AA analysis) and
82
-------
the average rate of processing for a municipal incinerator.
With the use of a scrubber or ESP, municipal incinerators
-4 -1
release between 6x10 and 1.0x10 pounds of cadmium/ton of
refuse.2'8'10'14'17'33/ A best judgement factor of 1.3xlO~2
pounds/ton of refuse was a result of the reported mean of
-2 -3
1.8x10 pounds minus the standard deviation of 5x10 pounds
of cadmium/ton of refuse for the above recent stack test
analysis. / With a refuse figure of 20,143,620 tons / and
the best judgement emission factor, EEA estimates emissions to
be 131 tons/year. EEA's emission estimate is higher than that
of Davis (95 tons),7/ Mitre (95 tons),11/ EPA (48 tons),2/ and
Sargent (16 tons), but is in close agreement with that of
2 /
GCA (150 tons). Because other estimates are fairly close to
that made by EEA, one can surmise that the volume of municipal
trash has increased since the others were made.
(d) Future Trends
It is difficult to project future emissions resulting from
municipal incineration. Control device use is expected to reach
100 percent before 1985. The number of municipal incinerators
34/
has decreased five percent annually over the last several years.
However, those incinerators which have begun operation recently
have capacities much greater than those which are closing.
Therefore, existing capacity does not accurately reflect an in-
crease or decrease in the number of municipal incinerators.
Predictions call for 49 additional incinerators by 1979. / As
a result of the decreases in number, but increase in capacity, it
is concluded that emissions through 1985 will remain constant.
The effect of NSPS upon these new plants, and the use of high
efficiency control devices by all municipal incinerators,
should support the above assumption.
83
-------
2. Sewage Sludge Incinerators
(a) Process
The steps in the sewage sludge process differ in some ways
from those in the municipal incineration. First, the temperature
of the feed sludge is raised to 212° F to evaporate water from
the sludge. The vaporization and increase in temperature combine
to raise the water vapor and air temperature of the gas, which in
turn, serves to bring the volatiles of the sludge to ignition.
End products are water, sulfur dioxide, carbon dioxide, and inert
ash.
The multiple hearth is the most common incineration unit. A
number of solid refractory hearths with a central rotating shaft
are encompassed by a circular steel shell. "Rabble" arms,
connected to the rotating shaft, serve to agitate the sludge
which drops from one hearth to another through openings in each
hearth. An inner cold air tube, which cools the rabble arms,
runs through the central shaft. The shaft has an outer tube
which serves a similar function for hot air. Continuous feeding
can be accomplished in this manner.
(b) Emissions Source and Control
As sludge is volatilized, cadmium is released into the air.
Sewage sludge contains only a small amount of cadmium, origin-
ating from plastics or pigments, plus contaminants which may have
become incorporated into the sludge from industrial or domestic
wastewater. Until recently, it was possible to meet current
emissions standards with the use of afterburners. However,
present control of sewage sludge incineration emissions includes
wet scrubbers.
84
-------
(c) Emission Estimate
Multiple hearth sewage sludge incinerators controlled by a
scrubber are estimated by EPA to emit 7xlO~ pounds of cadmium/
8/
ton of dry sludge. ' EEA estimates that less than one ton re-
sults from incineration of 1,460,000 tons of sludge ' each year.
(d) Future Trends
Sewage sludge production may increase to 17,000 tons/day '
by 1985, and assuming that 25 percent of this amount is incin-
erated, ' the emission of cadmium will increase along with
the amount incinerated. However, exist several condition these
conclusions. The fact that control devices are now becoming
commonplace supports may lower the rate of cadmium emission
increases. On the other hand, recent bans on off-shore dumping
and continually decreasing land-fill space may increase the
amount of sludge incinerated. Because these factors will
probably serve to counteract each other, EEA assumed that 25
percent of all sewage sludge would be incinerated, so that
less than one ton of cadmium a year is expected to be emitted
through 1985.
J. Summary
To determine the population affected by various concentra-
tions of airborne cadmium, it was necessary first to determine
sources of airborne emissions. Next, the specific part of each
process from which emissions emanate was discerned and emission
estimates were calculated. The emission estimates (Table V-2)
were based upon emission factors (Table V-l) and production
figures (Table V-2). Future emission estimates were also dis-
cussed (Table V-2).
85
-------
TABLE V-2
CADMIUM EMISSION FACTORS
SOURCE
MINIMUM
MAXIMUM
BEST JUDGEMENT
PRIMARY METALS PROCESSING
ZINC
Coking
Sintering w/Cyclone
Sintering w/Cyclone * ESP
Roasting
Horizontal Retort
Vertical Retort
Electrothermic
Overall (Not Electrolytic)
Electrolytic
LEAD
Overall Smelter
Blast Furnace w/Baghouse
COPPER
Uncontrolled Smelter
Snelter w/Baghouse (~95S)
,. CADMIUM
SECONDARY METALS PROCESSING
IRON a STEEL
Sinter Wlndbox-Uncontrolled
Sinter Ulndbox
w/Rotoclone a ESP
Blast Furnace-Controlled
-- .Open Hearth-Uncontrolled
Cpen Hearth w/ESP
3
-------
TABLE V-2 (Continued)
CADMIUM EMISSION FACTORS
SOURCE
F OSS 11 FUEL COMBUSTION
Coal-fired Power Plants
Uncontrolled
COMUU lied (ESP)
Oil -Fired Power Plants
Controlled ( ~ ESP)
I'eatlng Oil (Residual; 16
Fuel Oil)
' Diesel Oil
Gasoline (for IS mpg. all
' Cd Emitted)
SEWAGE SLUDGE INCINERATORS
Multiple Hearth w/Scrubber
Fluidlzed Bed w/Scrubber
WNICIOAL INCINERATORS
Unnni' rolled
Con I. rolled (Scrubbers or ESP)
lURRi'iTING OIL INCINERATORS
Uncontrolled
MISCELLANEOUS
Motor 011 Consumption
(Vehicles)
Rubber Tire Wear
Fungicides Application
Fertilizers Application
Superphosphate Fertilizers
Ani'H cation
CIMEHl PLANTS
DRY PROCESS
Kiln w/Baghouse or ESP
Raw Mill Feed w/Baghouse
Raw Mill w/Baghouse
Raw Mill Air Separator w/
Baghouse
Finish Mill Feed w/
Baghouse
Finish Mill w/Baghouse
Finish Mill Air Separator
w/Baghouse
WET PROCESS
Kiln w/ESP
Raw Hill w/Baghouse
Clinker Cooler w/ESP
or llaghouse
1 IME K'LN (PULVERIZED COAL)
Kiln w/Spray. Settle *
Baghouie
MINIMUM
lx!0'41b/TCoal (STK.AA)
lx!0'61b/TCoal (STK.AA)
7.1xlO"71l>/gal (STK.ES)
1.5xlO'61b/gal (EST.CONC)23'
6xlO'71b/gal (EST.CONC.ES)26'
6.3xlO'lllb/veh-n1 (EST. ...
CONC)Z9/
lxlO~61b/TSludge (DRY)(STK.
ES)
4xlO"71b/TSludge (DRY)
(STK.ES)
3xlO'31b/TRefuse (EST)
6xlO'*lb/TRefuse (FLAA)
Ixl0'101b/veh-m1 (EST.CONC)37/
1.8xlO-61b/gal (EST.M8)40/
1.7xlO'*1b/T (EST .MB)
3xlO'71b/TFeed (STK.ES)
lx!0'71b/TFeed (STK.ES)
7.6xlO'71b/TFeed (STK.ES)
5xlO'71b/TFeed (STK.ES)
7.4xlO'61b/TFeed (STK.ES)
1.7xlO"61b/TFeed (STK.ES)
4.6xlO"5Ib/TFeed (STK.ES)
MAXIMUM
lxlO"11b/TCoal (STK.ES)
7xlO'41b/TCoal ISTK.AA)19'
4.4xl(T61b/gal (STK.CONC,ES)Z1/
4xlO'51b/gal (EST,CONC.NA)24/
ZxUTS1b/gal CEST)27'
4.5xlO"81b/veh-m1 (EST.CONC)30/
2xlO'51b/TSludge (DRY) (STK.ES)
3xlO~61b/TSludge (DRY)(STK,ES)
1.8xlO'21b/TRefuse (STK.ES)34/
1.0xlO*11b/TRefuse (EST .MB)
5xlO'81b/veh-ra1 (EST.CONC)38/
SxlO'51b/gal (EST)
5xUT21b/T (EST.MB)
4.1xlO'71b/TFeed (STK.ES)
4.3xlO'71b/TFeed (STK.ES)
9xlO'71b/TFeed (STK.ES)
1.6xlO*61b/TFeed (STK.ES)
1.3xlO"71b/TFeed (STK.ES)
2xlO'41b/TFeed (STK.ES)
lx!0'41b/TFeed (STK.ES)
6.9xlO'51b/TFeed (STK.ES)
BEST JUDGEMF.V
lx!0'3lb/TCoai:5/
6xlO-5'Vc=a'2?/
9xlO-71b/ga: 'S^.ES)"'
3xlO-61b'galjr'
7xlO'71b/ga' 'EST.CO-.'C.ES)2"''
2xlO-81b/v.^131/
7xlO"61b/TSludge (DRY) (ST^f
•V
1.3x!0'61b/TS'.(;ge (riY.fi".'
'Si
6xlO'31b/TRefuse (STK.ES}'"'1'
1.3xlO'21b/TRefuse (S7K.AA)36/
2xUT61b/gal (UNK)
2xlO"9lb/veh-m1 (UNK)
8»10-91b/»eh-n,W
I*10-51b'9al41>
6»10-31b'T42'
2xlO-4Ib/T
3xlO'41b/TFeed (STK.ES)
3.6xlO'71b/TFeed '
2.7xlO'71b/TFeed
8 5xlO"71b/TFeed
lxlO-61b/TFeed
lx!0-71b/TFeed
2.6xlO'61b/TFeed (STK.ES)
2xlO-51b/TFeed43/
ZxlO'51b/TFeed
lxlO-51b/TFeedM/
5.7xlO'51b/TFeed
a/ EST • Estimate; MB - Mass Balance; SITE • Site Visits; SURV • Survey of Companies. UNK • Unknown
(1n literature); STK • Stack Sampling Results; CONC • Concentration of Cd In feed, fu«J. or missions
(w/STK); ES • Emission Spectroscopy; AA • Atomic Absorption (FL-Flane); NA -
-------
TABLE V-2
AIRBORNE CADMIUM EMISSIONS—1974 , 198S
Source
MINING
Zinc
Copper
Lead
PRIMARY METALS
Zinc
Pyronetallurgic
Electrolytic
Lead
Copper
Production
1974*
478,850
1,414,246.8
603,024
423,000
121,945
866,095
1,435,662.4
Emissions
Estimate
<1
<1
<1
529
0
2
5
Reference
12
12
12
40
40
40
40
Production Emissions
1985 (e) Estimate
845,377 <1
2,563,122 <1
1,169,524 <1
1,000,000 529
-
790,000 2
3,849,844 13.4
Referei
41
41
41
9
-
9
9
Cadmium
SECONDARY METAL PROCESSING
Iron and Steel
Sinter Windbox Uncontrolled
Sinter Windbox w/Rotoelone
and ESP
Basic Oxygen Furnace
Uncontrolled
BOF w/Venturi or ESP
Open Hearth Uncontrolled
Open Hearth w/ESP
Electric Are Uncontrolled
Electric Arc Controlled
Blast Furnace Controlled
Overall Uncontrolled
Zinc
Lead
Copper
MANUFACTURING
Pigments
Stabilizers
Batteries
FOSSIL FUEL COMBUSTION
Coal-Fired Power Plants
Oil-Fired Power Plants
Heating Oil
Diesel Oil
Gasoline
MISCELLANEOUS
Motor Oil
Rubber Tire Hear
Fungicides
Fertilizers
Cement
INCINERATION
Sewage Sludge Incinerators
Municipal Incinerators
3,088.2
12
991.24
1,139
<1
21.94x10° 22
11.35x10° 5.4
1.2X106 <1
78.8x10* <1
7.64x10° 22
29.06x10° 2
27.3x10* 46
4.6
95.2x10 0
12.84x10" 95
182,665 <1
698,698 <1
513,308 38
1,212.1 9
991.8 3
628.14 <1
3.913xl08 7.04
(Btu's)
500x10° 9
(barrels)
935.1x10* 29.2 (1975)
(barrels)
llxlO9 <1
(gallons)
1,330,074x10* 13
(VMT)
1,028,121x10° «1
(VMT)
1,330,024x10° 5
(VMT)
59,800 <1
8,535xl03 <1
Bl,210xl03 <1
1,460,000 <1
20,143,620 131
13
13
13
13
13
13
13
13
13
13
12
12
12
6
6
£
42
42
45
39
43
43
43
9
9
9
36
34
-
40x10*
.
1.73x10*
_
21.1x10°
_
38.8x10*
113.6x10*
-
223,000
860,000
800.000
1,560
1,179
2,200
530.750x10*
732.2x10*
(barrels)
980.9x10°
(barrels)
15.12xl09
(gallons)
1,707,152x10*
(VMT)
1,707,152x10*
(VMT)
1,707,152x10*
(VMT)
92,769
13,240xl03
94.537X103
1,551.250
20,143,620
-
19
.
-------
Airborne cadmium emissions derive from many sources includ-
ing: primary metal processes, production of items which contain
cadmium (such as cadmium paint pigments), fossil fuel combustion,
incineration, secondary metal processing, and the use of items
which inadvertantly contain cadmium (e.g., rubber tires).
Emission factors were obtained through an extensive search
of current data sources. Minimum, Maximum, and "Best Judgement"
figures were developed using methods and data reported below,
tested in what is believed to be the order of decreasing accuracy:
1. DATA; Stack tests usually conducted at only
one location with multiple tests; samples analyzed
by atomic absorption (AA) and results reported
as cadmium emission factors or rates, or as
cadmium concentrations in particulate matter
and particulate emission rates or factors.
METHOD; Emission factors for cadmium taken
directly or calculated with reported or
assumed values of process parameters (e.g.,
uncontrolled open hearth).
2. DATA; Stack tests conducted at one or more
location usually with one test per process;
sampling train samples analyzed by emission
spectroscopy, a semi-quantitative method, and
reported as detected amounts or concentrations.
METHOD; Emission factors calculated with
reported particulate emission factors or rates
as above (e.g., uncontrolled sinter windbox).
89
-------
3. DATA; Concentration of cadmium in particulate
emissions, usually analyzed by emission spec-
troscopy (ES), but no particulate factors or
rates reported (for a stack) .
METHOD; Cadmium emission factor calculated from
the particulate emission factor or NSPS standard
for the source type (e.g., maximum and best judge-
ment factors for electric arc furnace) .
4. DATA: Concentration of cadmium in fuel or feed
reported for analysis by AA or ES.
METHOD; Emission factor computed assuming 100
percent emission and typical fuel characteristics
(e.g., heating oil). Primarily used for liquid
fuels.
5. DATA; Survey of industrial plants or site visits
conducted by EPA during development of original
cadmium emission factors (e.g., minimum factor
for cadmium processing).
METHOD; Mass balances for specific processes.
Emission factor determined from unaccounted-for
cadmium or by expected emissions for typical
process and control equipment relative to total
production or raw materials (e.g., overall
uncontrolled iron and steel).
6. DATA AND METHOD; Engineering estimates made when
no other data is available (e.g., zinc roasting).
Table V-l provides a listing of emission factors which were used
in the EEA study (1974). Production figures were obtained for
use with emission factors to determine the emissions from each
90
-------
process (Table V-2). A comparison of emission estimates, including
those of EEA, can be seen in Table V-3. Assuming various control
technologies and use of them by a percentage of operating facil-
ities, yearly cadmium emissions total 914 tons. EEA's projections
to 1985 indicate that total airborne cadmium emissions, assuming
all facilities employ some type of control technology, will
approximate 972 tons.
91
-------
TABLE V-3
COMPARISON OF CADMIUM EMISSION ESTIMATES 1968-1977
EMISSION ESTIMATES TONS/YEAR
NJ
Source
Mining
(Zn + Pb + Cu)
Primary Metals
Zinc
Lead
Copper
Cadmium
Secondary Metals
Steel Scrap
Zinc
Copper
Manufacturing
Pigments
Stabilizers
Miscellaneous
Incineration
Fossil Fuel
Davis ORNL
1968 1968 MITRE
-------
Source
TABLE V 3 (Continued)
COMPARISON OF CADMIUM EMISSION ESTIMATES 1968-1977
EMISSION ESTIMATES TONS/YEAR
Davis
1968
ORNL
1968
MITRE
EPA GCA EPA EEA 1974-77 w/ /
1971 1974 1975 Comparable Est. Control'
vo
U)
Sewage Sludge Inc.
Miscellaneous
Motor Oil
Rubber Tires
Gasoline
Forest & Agr. Burning
Other
TOTAL =
138
12
20
2294 1425-2380 2305
1650
300
1100.2
.005
1
6
-
-
-
1 - <1
6 - 6 6 5.2
- - 50
50
<2
-------
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Up in 1976," Department of the Interior News Release/
Bureau of Mines, March 14, 1977.
46. , Market-Oriented Program Planning Study
(MOPPS), U.S. Energy Research and Development Administration,
Washington, D.C., September 1977.
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SECTION VI
SCREENING OF CADMIUM SOURCE TYPES
A. Introduction
The ambient concentrations produced by the various indivi-
dual cadmium emitters were estimated very conservatively in
order to determine which source types could potentially produce
significant levels of cadmium (<0.1 ng/m annual average) in
the ambient air. The average, "typical," and/or maximum plant
capacity or production rates for each source type was collected
from the industrial literature. For area sources, an area of
emission was taken from the literature or estimated. For point
sources, the stack characteristics in terms of ranges or "typi-
cal" values were compiled when available. The stack character-
istics required were flow rate per production rate, stack tem-
perature, and stack height. The primary references for this
data were:
1. Vandegrift, A.E., Shannon, L.J., et.al.,
Handbook of Emissions, Effluents, and Control
Practices for Stationary Particulate Pollutant
Sources, Report for NAPCA Contract No. CPA-22-
69-104, November 1970.
2. Deane, G.L., Lynn, D.A., and Suprenant, N.F.,
Cadmium: Control Strategy Analysis, GCA-TR-
75-36-G, Final Report for EPA Contract No.
68-02-1331, Task No. 2, April 1976.
3. Katari, V., Isaacs, G., and Devitt, T.W.,
Trace Pollutant Emissions From Processing
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Metallic Ores (Final Report), EPA-650/2-
74-115, PB 238 655, October 1974.
4. Environmental Protection Agency Emission
Test Results, Environmental Measurement
Branch, OAQPS, Environmental Protection
Agency, Durham, North Carolina.
5. Arthur D. Little, Inc., Steel and the Environ-
ment; A Cost Impact Analysis, a report to the
Iron and Steel Institute, May 1975.
Often, little, if any, specific information was available
for a given plant characteristic of a source type, so that an
estimate had to be made. Such estimates were based on available
information about the process, control equipment, and standard
industrial practice.
The information on plant sizes in terms of capacity or
production rate were extracted from the following sources:
1. Deane, G.L., Lynn, D.A., and Suprenant, N.F.,
Cadmium; Control Strategy Analysis, GCA-TR-
75-36-G, Final Report for EPA Contract No.
68-02-1337, Task No. 2, April 1976.
2. International Directory of Mining and Mineral
Operations, Engineering and Mining Journal, Mc-
Graw-Hill, New York, New York, 1976.
3. Arthur D. Little, Inc., Steel and the Environ-
ment: A Cost Impact Analysis, a report to the
American Iron and Steel Institute, May 1975.
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4. Metal Statistics 1977, American Metal Market,
Fairchild Publications, New York, New York, 1977.
5. Sargent, D.J. and Metz, J.R., Technical and Micro-
economic Analysis of Cadmium and Its Compounds,
EPA-560/3-75-005, June 1975.
6. Fenton, R., "Present Status of Municipal Incin-
erators ," Incinerator and Solid Waste Technology,
J.W. Stephanson, et.al., Eds. ASME, New York, New
York, 1975.
7. Jones, J.L., et.al., "Municipal Sludge Disposal
Economics," Environmental Science and Technology,
October 1977.
8. Weinstein, N.J., Waste Oil Recycling and Disposal,
EPA-670/2-74-052, August 1974.
Most of the preliminary information, such as industry production
figures, and some detailed information, such as the size of
units for primary smelting and some of the miscellaneous sources,
were taken from the first reference. The remaining references
were the sources of maximum or "typical" plant size information
for mining and primary smelting, iron and steel plants, second-
ary smelting, manufacturing using cadmium, municipal incinerators,
sewage sludge incinerators, and lubricating oil incinerators,
respectively.
Fossil fuel consumption was estimated for a typical plant
size in the case of power plants and derived from the following
government publications for fuel oil and gasoline:
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1. "Sales of Fuel Oil and Kerosene in 1975,"
Mineral Industry Surveys, U.S. Department of
Mines, Washington, D.C., 1976.
2. National Functional System Mileage and Travel
Summary from the 1976 National Highway Inventory
and Performance Study, U.S. Department of Trans-
portation, Federal Highway Administration, June
1977.
The first document gives fuel consumption by state for residual,
distillate, and diesel fuel. The diesel fuel consumption is
further broken down by on-highway and off-highway uses. The
second report gives the density of vehicle miles traveled in the
urbanized area for the major metropolitan areas and the states.
The compiled plant characteristics for the various source
types were then used to make "realistic," but very conservative,
estimates of the effect of a "typical" or maximum size plant of
each type on the concentration of cadmium in the ambient air.
The effects of the area sources were estimated for screening
purposes by using the Hannah-Gifford urban air pollution model,
assuming a very conservative (especially for an annual average)
wind speed of two m/s, or the Miller Holzworth urban model for
cities for which it had been calibrated. The effects of indi-
vidual plants of the various point source types were estimated
for screening purposes by using EPA's PTMAX dispersion model
using generally conservative emission rates, stack heights,
temperatures, and flow rates. The PTMAX model is, in itself,
conservative as it estimates hourly average ambient concentra-
tions given an emission rate and set of stack concentrations,
while the ambient concentration of interest is the annual aver-
age. An annual average is generally a factor of three to four
lower than a 24-hour average concentration, which is, in turn,
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generally a factor of two to three lower than an hourly average.
In addition, the maximum concentration considered was the maxi-
mum for any wind speed and stability conditions. Thus, condi-
tions which might occur for a short time, but which are unlikely
to represent the annual average meteorological conditions, and
which would occur very near to the plant, are often used to con-
servatively represent the worst realistic case. The emission
rates (the products of the emission factors and production capa-
cities or rates, expressed in grams per second) used were con-
servative in that it was generally assumed that a plant operated
only 220 days per year and eight hours per day. If available,
both the maximum and a "typical" plant size were considered for
both the maximum and best judgement estimates of cadmium emis-
sion factors in order to assess the likelihood of the estimated
concentrations. For some source types, the two different esti-
mates of plant size or of emission factors were nearly equal, so
only the more conservative case was calculated. The stack
characteristics for which PTMAX was run were generally chosen to
be the ones in the realistic range of characteristics for the
plant type which would generate the most conservative (highest)
maximum ambient concentration for a given emission rate (of one
g/s)(i.e., low flow rate, low stack height, and low stack tem-
perature) . The following sections briefly outline the estimated
conditions and the results of the screening of the various
cadmium source types.
B. Mining
The cadmium emissions from the mining of cadmium-bearing
ores were very conservatively estimated using the area source
approach. For the largest zinc mine of one million tons per
year, it was assumed that the concentration of zinc in the ore
was 2.6 percent and that the area of the mine was one square
mile. For a wind speed of two m/s at these conditions, the
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Hannah-Gifford model estimates a concentration of 16 ng/m .
However, the Hannah-Gifford model was developed for urban areas
by assuming a series of line sources which is not the case for
an isolated source such as mine. A wind speed of five m/s is
more generally typical; the average mine produces 500,000 tons/
year; and a mine's property, if not its active area, is usually
at least ten square miles. Therefore, it was presumed that a
more realistic estimate of ambient concentration beyond the mine
property would be at least two orders of magnitude lower and
that even the largest mine would generate concentrations that
were at most marginally significant (-4.0.1 ng/m ). Since most
zinc mines are underground mines, emissions released to the
atmosphere would be expected to be much lower, as they would on-
ly be the dust containing cadmium which is picked up, carried,
and exhausted by the ventilation system, or which is picked up
from storage piles by the wind or during movement of the ore.
If the ventilation stack is assumed to be 20 m tall and to
exhaust only 0.90 m /s at 340° K, the maximum concentration at
any meteorological conditions (A stability, 0.3 m/s wind) would
be about 60 ng/m . However, less stable conditions or higher
wind speeds reduce this estimate by at least an order of magni-
tude. Therefore, for an annual average with more realistic
conditions of stack, meteorology, and operation, ambient concen-
trations of cadmium generated by emissions from zinc mining
should be below significant levels.
The treatment and conclusions were similar for the other
types of mining which handle significant amounts of cadmium.
The largest lead mine produces 1.6 million tons/year and the
lead concentration in ore is estimated at 1.6 percent, so the
ambient concentration for a one mile square area source would be
1.6 ng/ m . Since most lead mines are underground and the
average production is only 350,000 tons/year, it is even more
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unlikely that significant concentrations would be generated.
The average lead-zinc ore in the U.S. contains 2.6 percent zinc
and 1.6 percent lead, so that the very conservative application
of the Hannah-Gifford model predicts a concentration of about 28
ng/m for a 1.6 million ton/year mine. Again, the same charac-
teristics of this estimate, as those for zinc mining noted
above, make this high a concentration extremely unlikely, so
that levels below significant are presumed. Copper mines gen-
erally are surface mines producing as much as 19.6 million tons
of ore per year. Assuming the maximum U.S. concentration in ore
of 0.6 percent, and a rather conservative working area of ten
square miles, an ambient concentration of 0.09 ng/m is pre-
dicted, disregarding the fact that the pit may be several hun-
dred meters deep.
C. Primary Metals
The primary metal smelters were treated as point sources
using very conservative plant and stack characteristics for
screening purposes. The largest zinc smelter produces 250,000
tons/year, so this was used to calculate an emission rate for
the various processes and the overall plant using the maximum
emission factor. Assuming stack characteristics ranging from a
ten m stack emitting about 20 m /s at ambient temperature for
coke ovens, to a 120 m stack emitting 235 m /s at 370 to 615° K
for most of the processes, the range of estimated maximum con-
centrations ranged from 96 ng/m to about 60 ng/m for a hori-
zontal retort and the overall process, respectively. Most of
the individual processes would produce maximum ambient (hourly
average) concentrations on the order of ten ng/m , so that even
for an average plant size of 100,000 tons/year, it is unlikely
that concentrations lower than the significant level (0.1 ng/m )
would be produced. This is so even for the "best judgement"
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emission factors, as they are no more than a factor of two
smaller than the maximum estimate emission factor.
Similarly the largest primary lead smelter produces 350,000
tons/year. Therefore, assuming a 60 m stack with a flow rate
of 160 m /s at 340° K for the overall smelter, and a flow rate
of 4.8 m /s at 330° K for a baghouse controlled smelter, the
ambient concentrations produced by the two model plants would
3 3
be 8.7 ng/m and 520 ng/m , respectively. Again, the average
plant size is 52,000 tons/year and the "best judgement" emission
factor is less than a factor of three lower, so it is unlikely
that lower than significant levels would be produced. As the
stack characteristics are similar for copper and cadmium smelters,
the emission factors are at least as high, and the production
rates are in the area of 200,000 tons/year, there is no question
that these facilities also produce ambient concentrations far
above the significant level (in the range of ng/m for copper
and mg/m for cadmium).
D. Iron and Steel
The individual iron and steel processes were screened using
representative sizes for that process, while the overall plant
was screened using the maximum production rate of three million
tons of steel per year. All of stacks were approximated as 40 m
and the temperatures at 310-340° K. The estimated concentra-
tions range from 8.3/ig/m for a 13,055 ton/day controlled basic
oxygen furnace (using the "best judgement" emission factor and
95 m /s at 340° K), to 4.5 yug/m for a 6,504 ton/day uncon-
trolled open hearth (using the maximum emission factor and the
same stack conditions). The overall plant estimate (using a
flow rate of 220 m /s and 310° K) ranged from 1.6/ug/m3 to 13
/ug/m using the maximum or best judgement emission factor. For
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the other processes (3,787 ton/day interstrand, 1,440 ton/day
blast furnace, and a 1,344 ton/day electric arc), the estimated
concentrations were generally on the order of 0.1-0.1 >ag/m .
Since the controlled estimates for the conservative screening
technique were as low as ten's of nanograms per cubic meter, it
was possible that some plants, particularly small ones, might
prove to produce insignificant concentrations. In the later
analysis, it was found that some plants did produce very low,
but generally significant, concentrations, but that iron and
steel plants with sinter strands, which are difficult to con-
trol efficiently, or with very large capacity, are estimated to
produce maximum annual average concentrations of as much as
100's of nanograms per cubic meter.
E. Secondary Smelting
The uncontrolled emissions of secondary zinc and copper
smelters were found to produce significant ambient cadmium
levels, while the controlled emission factors for secondary lead
smelters were found to produce at most, marginally-significant
concentrations even for the conservative screening procedure.
The 45,000 ton/year maximum size plant with an assumed stack of
40 m emitting 7.5 m /s at 340° K would generate a maximum con-
centrate of 0.9 Aig/ m . A secondary copper smelter producing 52
tons is a seven-hour-day and using a 20 m stack with a flow rate
of 17.5 m /s at 370° K would generate concentrations which are
another order of magnitude higher. Secondary lead plants with
a "typical" production rate of 2,500 Ib/hr with high efficiency
control equipment were estimated to produce ambient concentra-
tions less than six jug/m , even for the maximum emission factor,
and a 20 m stack with a flow of 0.9 m /s at 340° K. Using the
"best judgement" emission factors, the highest maximum concen-
tration generated by PTMAX, even for these very conservative
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stack characteristics, was less than 0.6 jug/m . Therefore,
since the range of sizes of secondary smelters is generally
small, and PTMAX estimates hourly, rather than annual averages,
secondary lead smelters were eliminated from further consider-
ation as a significant source of emissions.
F. Manufacturing
Very little information could be found about individual
plants which manufacture products containing cadmium. Using the
GCA estimates of the total production, the number of known
plants, and the very conservative mass balance or survey esti-
mates of emission factors, concentrations in the microgram per
cubic meter range were estimated for very conservative stack
conditions (20 m and 0.90 m /s at 340° K). Since there are
probably many more, and thus smaller, plants with increased
control efficiency and larger stacks, it was assumed that the
emissions of individual manufacturing plants would not produce
significant annual average concentrations of cadmium.
t5. Fossil Fuel Combustion
The only point source that was considered that burns fossil
fuel is power plants. Assuming a 300 MW(e) power plant (with
ten million Btu/hr power MW(e) and 82 percent boiler efficien-
cy) , and a 130 m stack with a flow of 285 m /s at 440° K, a
coal-fired power plant would produce ambient concentrations of
5 ng/m with the "best judgement" emission factor and - 700
/ug/m with the maximum emission factor. Assuming a 60 m stack
with a flow of 140 m /s at 440° K, the controlled coal- and oil-
fired power plants were estimated to produce concentrations
ranging from 0.8 /ig/m to 40 >ug/m for best judgement and maxi-
mum estimate emission factors. Thus, for more realistic condi-
tions, power plants were generally thought to be marginally
significant since some plants could probably produce significant
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concentrations. Therefore, an annual average CRSTER run (using
Dallas/Fort Worth meteorological conditions and a very conser-
vative 40 m stack with a flow of =105 m /s at 1,360° K) was
used to determine the critical emission rate which could cause a
significant maximum annual average ambient concentration (<0.1
/ug/m ) for each fuel type. The emission factors for each fuel
type were then assumed to follow a log-normal distribution (with
a probability of being exceeded of 90 percent for the minimum,
50 percent for the "best judgement" and ten percent for the
maximum emission factor), and multiplied by the capacities in
the Energy Data System (EDS) file to calculate the emission
rates for uncontrolled and controlled power plants (assuming a
24-hour operation). Plotting these emission rates of log-
probability, paper showed that only three plants had a probabil-
ity greater than ten percent of exceeding the significant am-
bient cadmium concentrations. These three plants were the three
largest plants listed in the EDS with no control equipment.
Since all power plants have some particulate control equipment
(generally of greater than 90 percent efficiency), individual
power plants were thus eliminated as a significant source of
cadmium.
The other fossil fuel combustion sources of heating oil,
diesel oil, and gasoline were treated as area sources. For
heating oil, the total distillate (including off-highway diesel)
and residual used in New York State in 1975 (the highest state
consumption in the nation) of 159 million barrels, was assumed
to be burned in the urbanized area of Metropolitan New York City
within New York State (1,634 mi) during a three-month period (24
hours per day). The ambient concentration, using the maximum
emission factor and the Hannah-Gifford model with a wind speed
of two m/s, was only 0.09 /ug/m , so heating oil was eliminated
as an individually-significant source. Similarly, the on-
highway diesel fuel consumption of California (17.9 million
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barrels) was assumed to be used in Metropolitan Los Angeles
(1,724 mi) over the entire year. Using the maximum emission
factor, the concentration generated by the Hannah-Gifford model
for a two m/s wind is 1.2 pg/m . The Miller-Holzworth model
for Los Angeles (city size 60 km) confirms this with a concen-
tration of 0.59 pg/m for a mixing height of 300 m and ore of
3.1 pg/m for a mixing height of 100 m and a wind speed of one
m/s. The Miller-Holzworth model for Los Angeles was also used
for gasoline consumption. The daily vehicle miles traveled per
square mile (DVMT density) of 61.342 and an assumed mixing
height of 300 m and wind speed of two m/s generated an estimated
3 3
0.3 /ug/m for the maximum and 0.15 Aig/m for the "best judge-
ment" emission factor. For the Washington, D.C. Metropolitan
area, the area with second highest DVMT density, the estimates
are 0.17 /ug/m and 0.08/ig/m . Therefore, because of the ac-
curacy of the estimates and the conservative meteorological
assumptions for the areas with the most usage, gasoline consump-
tion was concluded not be an individually-significant source of
ambient cadmium.
H. Miscellaneous
The miscellaneous sources of cadmium emissions are motor
oil consumption, rubber tire wear, fungicides, and fertilizers
with the exception of fungicides, for which no information or
application rates was available, and which may be learned in the
near future, these sources were treated by the area source
methodology. The same analysis was used for motor oil consump-
tion and rubber tire wear as was used for gasoline (i.e., the
Miller-Holzworth model using DVMT density). For motor oil
consumption, the calculated ambient concentrations are 13 pg/m
for Los Angeles and eight pg/m for Washington, D.C. For rubber
tire wear, the ambient concentrations are 0.3 ng/m and 0.2
/ug/m using the "best judgement" emission factor for the two
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cities, respectively. Thus, the individual automotive sources
of cadmium do not produce significant ambient levels of cadmium,
even in the cities with the highest DVMT density. When a high
2
fertilizer application rate of 20 g/m -year was assumed, the
ambient concentration using the Hannah-Gifford urban area model
with a wind speed of two m/s was calculated as 18 and 0.2 ng/m ,
with the maximum and "best judgement" emission factors, respec-
tively. As the maximum emission factor assumes that all the
cadmium in the fertilizer is emitted into the air, and a high
fertilizer application rate and conservative dispersion model
for rural locations was used, it was concluded that fertilizers
would not produce significant ambient concentrations of cadmium.
Cement plants are another source of cadmium emissions that
was found to produce ambient levels of cadmium even when very
conservatively modelled as a point source. Assuming the emis-
sions from the entire cement production of 31 million pounds/
year of the Lehigh Valley of Pennsylvania came out of one stack
(60 m with a flow of 115 m /s at 340° K) , the maximum ambient
(hourly average) concentration would only be 0.8/ug/m . With
the same production rate, and even more conservative stack
characteristics (as low as 20 m with a flow of 16 m /s and 295°
K), only a few of the individual processes would produce signi-
ficant ambient (hourly average) concentrations. Therefore, for
any individual cement plant, it was concluded that annual aver-
age ambient concentrations would be well below significant
levels.
I. Incineration
The incineration cadmium sources of municipal, sewage
sludge, and lube oil incinerators, were screened by using PTMAX
and a point source treatment. Using a 35 m stack with a flow of
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9.4 m /s at 310 K, and the maximum or "best judgement" emission
factor, the maximum and average capacities of 1,600 and 300
tons/24-hour day are estimated to generate ambient concentra-
tions on the order of micrograms per cubic meter. Since the
control equipment on incinerators is generally not of high
efficiency, municipal incinerators were considered to be a
significant source.
The maximum capacity sewage sludge incinerator of 7.5 tons/
hour, which operates only three days a week, would generate an
ambient concentration of less than three /ug/m even for a 20 m
stack with a flow of 2.5 m /s at 310° K. With a 35 m stack and
the same flow rate, the maximum hourly average concentration is
1.7 ng/m for the controlled multiple hearth maximum emission
factor, but only 0.6 ng/m for the "best judgement" emission
factor for the same process (0.12/ig/m for the controlled flui-
dized bed). It was, therefore, concluded that the annual average
emissions would not produce significant annual average ambient
concentrations of cadmium.
The only information that was available on lubricating oil
incinerators was that the total amount incinerated was estimated
to be 389 million gallons per year by a multitude of small
sources. Assuming that the uncontrolled emissions from incinerat-
ing all the lubricating oil in the nation all came out of a 20 m
stack with a flow rate of 0.9 m /s at 340° K, an ambient concen-
tration on the order of micrograms per cubic meter is estimated
by PTMAX. Since there are probably thousands of such inciner-
ators in the country, it is presumed that the annual average
ambient cadmium concentrations generated by any one of them
would be below significant levels.
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