United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-93/063 June 1993
Project Summary
Methodologies for Estimating
Air Emissions From Three
Non-Traditional Source
Categories: Oil Spills, Petroleum
Vessel Loading and Unloading,
And Cooling Towers
W. Ramadan, S. Sleva, K. Dufner, S. Snow, and S. Kersteter
Area source emissions of particulate
matter (PM or TSP), sulfur dioxide (SO2),
oxides of nitrogen (NO ), reactive vola-
tile organic compounds (VOCs), and
carbon monoxide (CO) are estimated
annually by EPA's National Air Data
Branch (NADB). Area sources are typi-
cally aggregations of individual
sources that are too small to be de-
fined as point sources in a specific
geographic area. Area sources usually
include all mobile sources and any sta-
tionary sources that are too small, dif-
ficult, or numerous to be inventoried
as point sources. EPA's National Emis-
sions Data System (NEDS) is the data
management and processing system
that has historically been used to main-
tain these annual emissions data. NEDS
defines an area source as an anthropo-
genic mobile or stationary source that
emits less than 100 tons* per year (tpy)
of TSP, SO2, NO , or VOCs or 1,000 tpy
of CO.
The original NEDS area source meth-
odology and algorithms were developed
in 1973 and 1974 using 1960 census
data (e.g., population, housing, manu-
facturing). The NEDS methodology has
remained relatively unchanged over the
past 15 years and is the basis for EPA's
Aerometric Information Retrieval Sys-
tem/Area and Mobile Source Subsystem
(AIRS/AMS) data. EPA's Joint Emis-
sions Inventory Oversight Group
(*) 1 ton = 0.907 metric ton.
(JEIOG) is currently updating and re-
vising emission estimation and alloca-
tion methods using more recent data.
In addition, JEIOG is involved in the
development of new emission estima-
tion methodologies. This report de-
scribes one such JEIOG activity.
While emissions sources included in
current inventory methodologies cover
a large portion of anthropogenic emis-
sions, many small source categories
are not included in the inventory. Iden-
tification, characterization, and inclu-
sion of these categories and their
emissions in the inventory will result in
a more thorough and complete emis-
sions inventory.
This report discusses work to iden-
tify and characterize emissions source
not accounted for in the NEDS and
AIRS/AMS area source methodology.
These missing or nontraditional
sources (sources that do not explicitly
appear on the NEDS area source cat-
egory list) were assessed as to their
importance and how their emissions
can be included in the inventory. Three
source categories were selected for
methodology and emission factor de-
velopment: oil spills, petroleum vessel
loading and unloading, and cooling tow-
ers.
This Project Summaty was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
~ Printed on Recycled Paper
-------
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
A missing or unaccounted for source
category is defined as a category that
does not explicitly appear on the EPA's
area source category list. Exceptions to
this definition include residential liquefied
petroleum gas (LPG) consumption, light
duty diesel passenger cars, and light duty
diesel trucks. Examples of true missing or
unaccounted for source categories include
cooling towers, street sweeping, street
sanding, oil spills, and vessel loading and
unloading operations.
Three previous EPA work assignments
identified, characterized, and prioritized
emissions sources not currently accounted
for by either the existing NEDS or SIP
area source methodologies. Of the ap-
proximately 200 source categories identi-
fied, 70 were characterized and prioritized.
This project was intended to identify
and characterize selected emissions
sources currently unaccounted for in the
NEDS and AIRS/AMS area source meth-
odology. A ranking process was devel-
oped to identify the sources to be
characterized, and the implementation of
that process resulted in the following
source categories being selected: oil spills,
petroleum vessel loading and unloading,
and cooling towers. The findings for the
three selected source categories follow.
Oil Spills
Background
Oil spills are accidental spills occurring
on land and water (both coastal and in-
land). Such spills may arise from incidents
involving ground transportation such as
tanker trucks or railroad cars; marine trans-
port such as barges or oil tankers; spills
or blowouts from pipelines, wells, or oil
rigs; and releases from spills or accidents
at point source facilities such as refineries
or petrochemical plants. Oil spills may in-
clude a variety of oil or petroleum prod-
ucts ranging from thick unrefined crude
oils and sludges, to oil refuse, industrial
process oils, gasoline, jet fuel, diesel fuel,
kerosene, and waste oils.
Emissions Generation
The types of activities that can lead to
oil spills include oil tanker accidents, pipe-
line ruptures, oil well accidents, process
operation accidents, storage tank leaks,
and operator errors.
The pollutants emitted from an acciden-
tal oil spill depend on several factors and,
in general, are limited to VOCs for evapo-
rative spills and blowouts. Emissions of
sulfur oxides, particulates, NOx, carbon
dioxide (CO?), CO, and VOCs may result
from combustion of spilled material. In ad-
dition, other potentially toxic compounds,
such as polycyclic aromatic hydrocarbons
(PAHs), dioxins, furans, heavy metals, and
hydrochloric acid, may be released as
combustion products or as a result of the
chemical cleanup of spills.
Sources Of Data
A national computer database and re-
trieval system exists for the storage and
retrieval of information and data on re-
leases of oil and hazardous substances.
This system, the Emergency Response
Notification System (ERNS), is managed
and supported by EPA, the U.S. Coast
Guard (USCG), the National Response
Center (NRC), and the Department of
Transportation's (DOT's) Transportation
Systems Center. Data and information are
entered into ERNS through telephone calls
or written notifications to the federal gov-
ernment to report oil or hazardous sub-
stance releases. Another major database
for oil spill releases is the NRC, which is
managed and operated by the USCG (in
conjunction with the EPA) at Coast Guard
Headquarters in Washington, DC. The
NRC is the national communications cen-
ter for activities related to discharges of oil
spills and hazardous substances. The NRC
compiles data and information on oil spill
and hazardous substances discharges and
makes these data available to requestors.
The Comprehensive Environmental Re-
sponse, Compensation and Liability Act
(CERCLA) and the Clean Water Act (CWA)
require that these discharges be reported.
The discharge reporting compliance rate
is estimated by the NRC to be around
90%. The NRC and the ERNS have the
following major advantages as sources of
activity data: (1)they are national data-
bases, (2) they have a low cutoff for size
of spills, and (3) they are relatively com-
plete databases. Other existing oil spill
databases include one maintained by the
Minerals Management Service, many
maintained by state agencies, and a few
maintained by private firms. Since there
are no major incentives for reporting dis-
charges to these other databases, how-
ever, there are concerns about their
comprehensiveness. However, some state
agency databases may be as accurate as
the NRC database for estimating oil spill
activity within the state boundaries. At a
minimum, state databases can serve a
comparative role to validate NRC data.
Potential Methodologies
Three methods for estimating emissions
are proposed: Methods I and II are for
current or past years, and Method III is for
estimating spills in future years. For
Methods I and II, ambient air emissions
estimates will depend on particular results
of some variation of the following general
procedure, which uses data from oil spill
incident reports: (1) determine the activity
indicator level (i.e., the number of inci-
dents and amount of material spilled);
(2) estimate the amount of material lost to
various media (i.e., soil, water); and (3) cal-
culate emissions.
Method III, which is proposed for future
year estimates, is a probabilistic approach,
involving historical data summarization,
trend-detection procedures, and short-term
forecasts.
The historical information on oil spills
associated with production, transport, stor-
age, and use of crude oils, fuels, and
other petroleum products, as noted ear-
lier, is available from several sources, in-
cluding the NRC and ERNS. These data
sources can be used to determine the
national, state, or local trends in oil spills
by oil product type and by oil spill source.
Trends in historical oil-spill volumes over
time can then be compared with historical
petroleum industry production and activity
indicators such as those found in the Oil
& Gas Journal and Predicasts' Basebook.
The Predicasts' Basebook has a variety of
indicators for the years 1976 through 1989.
If the oil-spill volume and petroleum in-
dustry trends coincide, forecasts may be
possible.
The last step in the method is to esti-
mate emission factors for volatilization,
combustion, and chemical treatment of
spills. The emission factors, coupled with
the quantity of oil spilled and the loss
factors, will provide an estimate of the oil
spill emissions released to the ambient
air. The report provides techniques for
estimating emissions due to volatilization
and combustion; however, no data asso-
ciated with emissions due to chemical
treatment were uncovered in the literature
search.
Stiver and Mackay present a method
for calculating the evaporation from crude
oil spills that accounts for the fact that the
oil's vapor pressure decreases as the
lighter fractions evaporate more quickly
than the heavier fractions. This method
requires experimental data specific to the
liquid spilled. Assuming that the vapor
pressure is constant can lead to large
errors, particularly for large elapsed times.
Stiver and Mackay also indicate that the
liquid-phase mass transfer coefficient can
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be assumed to be infinite under certain
conditions.
Measurements of CO, CO2, NO, NOx,
particulates, and PAH emissions from
crude controlled oil spill fires have been
identified. These measurements may pro-
vide the basis for estimating emissions
from such fires. Recent data from uncon-
trolled fires in Kuwait show significantly
less particulate production than the data
from controlled fires. Accurate estimation
of emissions from oil pool fires may re-
quire resolution of the differences between
the controlled and uncontrolled measure-
ments. Methods have also been identified
for use in estimating the burn rate and
pool area of oil spills.
Petroleum Vessel Loading And
Unloading
Background
In 1989, 52.4% of the crude oil and
35% of the refined petroleum products
were transported in the U.S. by water
carriers. This waterborne traffic consists
of both foreign and domestic carriers. For-
eign traffic consists mainly of imports of
foreign crude oil carried by oceangoing
tankers. Domestic traffic includes all com-
mercial traffic between points in the U.S.
(including Alaska, Hawaii, Puerto Rico, Vir-
gin Islands, and Guam).
Emissions Generation
Evaporative emissions from marine ves-
sels result from three processes: loading,
ballasting, and transit. Loading loss emis-
sions occur as organic vapors in empty
cargo tanks are displaced to the atmo-
sphere by the liquid being loaded into the
tanks. Ballasting loss emissions occur as
organic vapors in empty cargo tanks are
displaced to the atmosphere by the water
pumped into the tank. Transit losses oc-
cur while vessels are underway or are
fleeted.
Emissions from loading and unloading
petroleum products and crude oil from
marine vessels are concentrated in coastal
areas-surrounding the Great Lakes and
adjacent to ports on inland waterways.
Few seasonal variations are expected ex-
cept where wintertime frozen waters make
ports inaccessible, such as in Alaska and
the Great Lakes area.
The 1985 NAPAP inventory estimated
that 29,564 tpy of VOCs, 245 tpy of SO2,
and 98 tpy of NO were emitted from ma-
rine vessels handling petroleum products
and crude oil. AP-42 reports that
nonmethane-nonethane VOC emission
factors for crude oil vapors have been
found to range from approximately 55 to
100 weight percent of the total organic
factors. AP-42 also recommends that,
when specific vapor composition informa-
tion is not available, the VOC emission
factor can be estimated by taking 85% of
the total organic factor. Methane and
ethane have been found to constitute a
negligible weight fraction of the evapora-
tive emissions from gasoline.
The Marine Board estimates that va-
pors displaced by filling vessel tanks to-
taled 56,600 metric tons in the United
States in 1985 (about 0.2 percent of na-
tional VOC emissions). About 95 percent
of the emissions were from crude oil and
gasoline cargoes, with approximately
66 percent of those emissions coming from
inland barges, and the remainder from
oceangoing barges and tankers.
Sources Of Data
Several data sources are available on
movement of crude oil and other petro-
leum products, tonnage shipped and re-
ceived, and refinery and bulk terminal
capacities at the national, regional, Petro-
leum Administration for Defense (PAD)
district, state, and local levels. These data
sources are briefly described in the follow-
ing sections.
Waterborne Commerce of the United
States is a five-part annual publication
obtained through the U.S. Department of
the Army, Corps of Engineers' Water Re-
sources Support Center. It contains the
most detailed statistics available to the
public on the movement and throughput
of foreign and domestic cargo and ves-
sels at U.S. ports and harbors. The Water
Resources Support Center also handles
special requests for waterborne commerce
statistics through the Data Request Of-
fice.
Energy Information Administration
The Petroleum Supply Annual is an an-
nual report published by the U.S. Depart-
ment of Energy, Energy Information
Administration. The report includes statis-
tics on imports and exports of crude oil
and other petroleum products by PAD dis-
trict, and imports of residual fuel oil by
state of entry. In addition, it provides sta-
tistics on waterborne movements of crude
oil and petroleum products between PAD
districts and statistics on number and ca-
pacity of operable petroleum refineries by
PAD district and state. Finally, the report
includes data on refinery receipts of crude
oil by method of shipment (barge versus
tanker, domestic versus foreign) by PAD
district.
National Petroleum Council
As part of the federal government's over-
all review of emergency preparedness
planning, the National Petroleum Council
(NPC) completed a study in April 1989 to
determine the capacities of the nation's
petroleum and gas storage and transpor-
tation facilities. The results of the NPC
study were presented in a five-volume
comprehensive report titled Petroleum
Storage and Transportation. Appendix G
of the full report includes statistics on stor-
age capacity of petroleum terminals lo-
cated on the U.S. inland waterway system
and in the U.S. Coastal and Great Lakes
ports. Petroleum products considered in-
clude crude petroleum, fuel oil, asphalt
and mixed products (i.e., all other petro-
leum products combined).
U.S. Maritime Administration
The U.S. Maritime Administration
(MARAD) reports national estimates of
principal commodities carried between U.S.
ports by non-self-propelled tank barges.
According to MARAD, in 1985 41.4% of
the barges carried gasoline (including ad-
ditives), 18.5% carried distillate oil, 17.6%
carried residual oil, 6.4% carried crude
petroleum, 4.9% carried jet fuel, and 11.2%
carried all other commodities. In addition,
MARAD provides regional estimates of
barge activity.
Stalsby/Wilson Press
The Stalsby/Wilson Press publishes the
Stalsby's Petroleum Terminal Encyclope-
dia, a listing of the major oil company
terminals and independent terminal op-
erators in the U.S. and Canada, as well
as selected major ports throughout the
world. The encyclopedia provides infor-
mation on terminal characteristics includ-
ing location, terminal receiving capabilities
(e.g., barge, tanker), method for out-load-
ing at the terminal storage capacity listed
by product, high and low water depths,
berth length, and products handled at the
facility. The encyclopedia is published ev-
ery year and a half.
Emission Factors
AP-42
Emission factors for transportation and
marketing of petroleum liquids are avail-
able in Section 4.4 of AP-42. In AP-42,
evaporative emissions from marine ves-
sels are separated into three categories:
loading losses, transit losses, and
ballasting losses. Two classes of marine
vessels are considered: (1) ships and
ocean barges with tank compartment
depths of about 40 ft* and (2) shallow
draft barges with compartment depths of
10 to 12 ft. Petroleum products are sepa-
{*) 1 ft = 0.305 m.
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rated into the following classes: gasoline,
RVP 13; gasoline, RVP 10; gasoline, RVP
7: distillate fuel No. 2; residual oil No. 6;
crude oil, RVP 5; jet naphtha; and jet
kerosene.
AP-42 provides an equation that esti-
mates emissions from loading petroleum
liquids other than gasoline and crude oil
as a function of the physical and chemical
characteristics of the liquid being loaded.
For gasoline, AP-42 provides emission fac-
tors specific to loading operation type. An-
other equation has been developed
specifically for estimating emissions from
loading of crude oil.
Ballasting emissions occur as vapor in
the empty cargo tank is displaced to the
atmosphere by the water pumped into the
tank, thereby reducing the quantity of va-
pors emitted during subsequent tanker
loading. Tabulated emission factors, based
on average conditions, are available.
Finally, transit losses are estimated us-
ing the same equation for barges and
tankers. AP-42 also provides emission fac-
tors based on average conditions that can
be used when physical and chemical char-
acteristics of the fuel are unknown.
California Air Resources Board
The California Air Resources Board
(GARB) developed a methodology to esti-
mate hydrocarbon emissions associated
with loading crude oil, residual oil, gaso-
line, and jet fuel into marine tankers and
barges. Emission factors used in this meth-
odology are included in the report.
Potential Methodologies
Two potential methodologies for esti-
mating emissions from petroleum vessel
loading and unloading are presented in
this report. The key factor in these meth-
ods is to estimate the share of crude and
petroleum products carried by tankers as
compared to barges for each port and
harbor in the U.S. Such information must
be estimated at the state level and then
allocated to the harbor and port level.
In the first method, state-level estimates
of crude oil and the different problem prod-
ucts shipped (and received) in tankers
versus barges can be obtained from the
Data Request Office of the Water Re-
sources Support Center. In some in-
stances, where only a small number of
petroleum companies and refineries oper-
ate, not all the activity data may be dis-
closed because confidentiality may be
compromised. An alternative for estimat-
ing these data would be to develop a
national estimate of the activities and then
allocate the national estimate to different
states based on state-level total capacity
of refineries obtained from the Stalsby's
Petroleum Terminal Encyclopedia. State-
level emissions are estimated using the
equations presented in the full report.
Once state-level pollutant estimates are
obtained for crude oil and each of the
petroleum products, the estimates can be
allocated to refineries and petroleum ter-
minals based on storage capacities listed
in the Petroleum Terminal Encyclopedia.
After loading a river barge, a Coast
Guard-certified "tankman" places a load-
ing manifest aboard that includes informa-
tion on the product loaded, the loading
port, the quantity loaded, and the destina-
tion port. These cargo handling arrange-
ments also apply to oceangoing barges.
For tanker loadings, additional information
collected during the loading operation will
include ullage and cargo temperature.
Thus, if state agencies can obtain those
data from individual ports and harbors,
emissions can be estimated directly at the
local level. By using these data, more
accurate estimates of emissions can be
computed because the equations in AP-
42 can be applied instead of using the
overall typical evaporative emission fac-
tors. County-level estimates of pollutants
emitted are obtained by summing emis-
sions from all facilities located within a
county.
CARB Methodology
GARB has developed a methodology to
estimate hydrocarbon emissions associ-
ated with loading crude oil, residual oil,
gasoline, and jet fuel into marine tankers
and barges. Potential emissions resulting
from vessel unloading were not estimated.
Data on the amounts of the crude oil,
gasoline, jet fuel, and residual oil shipped
from California ports were obtained from
the 1988 Waterborne Commerce of the
United States. To use the data for the
other inventory years, the 1986 data are
scaled to the appropriate years using ra-
tios that CARB developed based on 1986
and 1987 California Energy Commission
data.
Cooling Towers
Background
Cooling towers are heat exchangers
which are used to dissipate large heat
loads to the atmosphere. They are used
in a variety of settings, including power
generation cycles, process cooling, and
air conditioning cycles. Cooling towers may
range in size from less than 5 x 106 Btu/hr
(5.3 x 106 kJ/hour) for small air condition-
ing cooling towers to over 5,000 x 106 Btu/
hour (5,275 x 106 kJ/hour) for large power
plant cooling towers. All cooling towers
that are used to remove heat from an
industrial process of chemical reaction are
referred to as industrial process cooling
towers (IPCTs). Towers that are used to
cool heating, ventilation and air condition-
ing (HVAC) and refrigeration systems are
referred to as comfort cooling towers
(CCTs).
Cooling towers are classified primarily
as either wet towers or dry towers (al-
though some hybrid wet-dry combinations
exist) and can be further subclassified by
type of draft and/or location of draft rela-
tive to the heat transfer medium, type of
heat transfer medium, relative direction of
air movement, and type of distribution sys-
tem.
Some industrial cooling towers for refin-
eries have been included in the point
source inventory; however, a review of
the AIRS/Facility Subsystem (AFS) Source
Classification Code (SCC) listing showed
cooling tower SCCs for refineries only.
Cooling tower SCCs for other industries
were not found. No methodologies exist
for including cooling tower emissions in
the area source inventory. This report dis-
cusses only wet cooling towers as sources
of emissions and focuses on CCTs, al-
though industrial cooling towers are ad-
dressed.
Emissions Generation
The two types of emissions from cool-
ing towers are drift and evaporative. Drift
emissions are water droplets containing
dissolved and suspended solids. Evapo-
rative emissions are made up of water.
The dissolved and suspended solids in
drift droplets are the result of various
chemical treatment programs. The magni-
tude and formation of drift depend on tower
design, operation, and maintenance.
Chemicals are added to the recirculat-
ing cooling water to inhibit the corrosive
effects of water, control the rate of scaling
and fouling, and control the growth of mi-
croorganisms in the cooling tower water
and the heat exchangers. The quality of
the cooling tower water supply directly
affects the type and quantity of chemicals
required to maintain satisfactory protec-
tion. Water quality also affects the num-
ber of cycles of concentration that can be
maintained.
Water droplets are formed as the water
splashes down through the fill material
and from the shearing action of the airflow
along the water surfaces within the tower.
These water droplets, containing sus-
pended and dissolved solids, become en-
trained in the air and are emitted from the
cooling tower. These emissions, known
as drift, are independent of the water lost
by evaporation. Evaporation rates are typi-
cally 1 to 2% of the circulating water flow
-------
rate, with drift rates ranging from less than
0.0001 to 0.01%.
The magnitude of drift loss is influenced
by the number and size of droplets pro-
duced within the cooling tower, which in
turn are influenced by the fill design, air
and water patterns, and other interrelated
factors. Tower maintenance and opera-
tion also influence the formation of drift
droplets. Excessive water flow, excessive
airflow, and water bypassing the tower
drift eliminators can promote and/or in-
crease drift emissions.
Large drift droplets settle out of the tower
exhaust air stream and deposit near the
tower. This deposition can result in wet-
ting, icing, salt deposition, and damage to
equipment and vegetation. Other drift drop-
lets may evaporate before being depos-
ited in the area surrounding the tower and
may result in PM-10 emissions. PM-10 is
generated when the drift droplets evapo-
rate leaving fine particulate matter formed
by crystallization of dissolved solids.
Drift droplets have the same water
chemistry as the water circulating through
the tower. VOCs, particulate matter, and
air toxic compounds are emitted from cool-
ing towers due to process contaminants
in the cooling water; anti-corrosion, anti-
scaling, anti-fouling, and other water con-
ditioning additives; biocides; and
suspended and entrained organics and
particulate matter carried in the water va-
por.
Sources Of Data
Detailed information on CCTs and model
CCT systems may be obtained from the
EPA report, Chromium Emissions from
Comfort Cooling Towers - Background In-
formation for Proposed Standards (EPA-
450/3-87-01 Oa). Data on commercial
building characteristics are available in the
U.S. Department of Energy publication,
Commercial Buildings Characteristics.
County-specific data on commercial, insti-
tutional, and industrial building space and
characteristics can be obtained from
county or community economic commis-
sions and Chambers of Commerce.
Section 11.4 of AP-42 provides particu-
late emission factors for wet cooling tow-
ers. Separate emission factors are given
for induced draft and natural draft cooling
towers. References are cited for chloro-
form and chromium emission factors and
industrial emission factors.
The Cooling Tower Institute list of publi-
cations and bibliography of technical pa-
pers were reviewed for references to emis-
sion factors. From the titles alone, no emis-
sions factor data were identified. In a brief
discussion concerning cooling tower emis-
sion factors for pollutants other than chro-
mium and particulate matter, EPA person-
nel indicated that it may be reasonable to
assume that emission factors for other
pollutants would have the same ratio of
pollutant to water as does particulate mat-
ter.
Methodologies
Several methodologies for estimating
emissions from cooling towers are pre-
sented. The majority of the discussion fo-
cuses on CCTs, although a short section
on industrial cooling towers is presented.
The most difficult part of the proposed
methodologies will be developing the emis-
sion factors, since the emission factors
will have to account for various tower de-
signs and drift eliminators, how and when
additives are used, and differences in cool-
ing requirements.
Industrial Cooling Towers
It is estimated that IPCTs are used at
approximately 190 petroleum refineries,
1,800 chemical manufacturing plants, 240
primary metals plants, and 730 plants in
the miscellaneous industries. The miscel-
laneous industries include utilities, tobacco,
tire and rubber, textiles, and glass manu-
facturing. Most, if not all, of the facilities
having IPCTs should be included in the
point source inventory. An IPCT at one of
these facilities should be coded as a point
within the facility. Since SCCs exist only
for cooling towers at refineries, additional
SCCs for cooling towers at other types of
facilities will need to be developed. AP-42
provides guidance for estimating particu-
late emissions for wet cooling towers.
Refinery cooling tower emission factors
are 6 Ib* VOC/MG cooling water and 10 Ib
VOC/1,000 bbl** refinery feed. No other
emission factors were identified for VOC
and air toxic emissions (other than chro-
mium) associated with cooling towers.
Comfort Cooling Towers
Over 250,000 CCTs are used through-
out the U.S., primarily in urban areas.
Major users of CCTs with HVAC systems
include hospitals, hotels, schools, office
buildings, and shopping malls. Refrigera-
tion systems that may use CCTs include
ice skating rinks, cold storage warehouses,
and other commercial operations.
Three methodologies for estimating
emissions from CCTs are presented.
These methodologies treat CCTs as area
sources of emissions and vary in level of
detail of information needed to use the
methodologies.
(*) 1lb = 0.45kg.
("} 1 bbl = 42 gal. = 159L.
Method I
This method is based on data on model
CCTs, including building size, tower cool-
ing requirements, flow rates (recirculation
rate, evaporation rate, and blowdown rate),
and chromium emissions per tower. Using
these data and the corresponding assump-
tions, this method would assume a direct,
static relationship between square feet of
space to be cooled and number of gallons
or tons of air conditioning needed. Next,
factors would be developed relating the
amount of various additives to gallons of
water. Finally, an algorithm would be de-
veloped that requires only limited informa-
tion from the inventorying agency. This
algorithm may take the form:
Total Commerical Space (sq ft)
x Gallons Water per sq ft per hr
x Utilization Rate
x Emission Factor (Ib additive/gal.)
Ibs Additive Emitted/yr
This method makes many assumptions
about cooling tower design and use of
additives. Regional testing of CCT opera-
tions and emissions and development of
regional emission factors may reduce
some of the uncertainty.
Method II
Using many of the assumptions from
Method I and procedures cited in Analysis
of Air Toxic Emissions, Exposures, Can-
cer Risks and Controllability in Five Urban
Areas, Volume /(EPA-450/2-89-012a), re-
gional or state per capita or per employee
emission factors could be developed for
each pollutant. This would require knowl-
edge of regional or state use of various
additives and would account for difference
in cooling seasons and other variables.
Employment in Standard Industrial Classi-
fications (SICs) 50 through 99 would be
used with the per employee factors, pro-
viding the following general algorithm:
County Employment SICs 50 through
99
x Per Employee Emission Factor
= Emissions per Year
Additional information is required to de-
velop these emission factors. Some data
may be available from the Cooling Tower
Institute. These data may include informa-
tion on the distribution of types of towers
and drift eliminators and use of various
anti-corrosive, anti-fouling, anti-scaling, and
biocide additives.
Method III
This method assumes that some data
may be available to make more detailed
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estimates of cooling tower emissions. Such
data include information on building size,
weekly operating schedules, percent of
buildings cooled, cooling equipment, and
exterior wall and roof materials. These
data are only available at the census re-
gion level, however, and would need to
be allocated to the state and county lev-
els. Once allocated, this information can
be used to estimate specific cooling re-
quirements and chiller and cooling tower
size and characteristics. Emission factors
would need to be developed for each set
of characteristics and pollutants. A method
based on using these data may not be
practical to use on a county-level basis.
Data Issues
For oil spills, the report presents three
methods. The first two methods are for
current or past years and consist of deter-
mining oil spill incident report retrieval,
which when coupled with emission equa-
tions or emission factors can provide esti-
mates of air emissions associated with oil
spills. The third method consists of prob-
ability analysis based on historical records
of oil spill frequency. Before the methods
can be successfully developed, however,
several areas need additional study. These
areas include such work as finding sources
of information on the area of oil spills; the
type of cleanup; and the amount of mate-
rial recovered. Additional work is also
needed to clarify the differences between
the smoke/particulate production rates of
other hydrocarbons besides crude oil, and
the evaporation rates for temperature other
than 22°C. Further research to enhance
the probabilistic approach for projecting
future air emissions is also suggested.
Policy issues to be resolved include the
handling of oil spills at point sources and
the development of guidance on the treat-
ment of offshore oil spill air emissions.
Three methods for estimating emissions
from vessel loading and unloading are
provided. A further study area is the need
for information on the physical and chemi-
cal characteristics of the products being
shipped (vapor molecular weight, true va-
por pressure of liquid loaded, temperature
of the bulk liquid, and density of the con-
densed vapors). The need for information
on the vessel condition (uncleaned,
ballasted, gas free) was also pointed out
as well as the need for data on the time
vessels spend in transit.
For cooling tower emissions estimation,
three potential methodologies are identi-
fied. For Method I, further investigation is
needed concerning clarification of the
many assumptions about cooling tower
design and the use of additives. In addi-
tion, it is suggested that further informa-
tion and data be acquired to develop
emission factors for the Method II algo-
rithm. For Method III, additional work is
needed to determine the feasibility of ob-
taining state- and county-level data on a
wide variety of factors that will affect the
levels of emissions from cooling towers.
GOVERNMENT PRINTING OFFICE: I9»3 - 750-071/110004
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W. Ramadan, S. Sleva, K. Dufner, andS. Snow are with TRC Environmental Corp.,
WOEuropa Dr., Suite 150, Chapel Hill, NC27541;andS. Kersteteris with Science
Applications international Corp., 206 University Tower, 3101 Petty Rd., Durham,
NC 27707.
S. Sue Kimbrough is the EPA Project Officer (see below).
The complete report, entitled "Methodologies for Estimating Air Emissions from
Three Non-Traditional Source Categories: Oil Spills, Petroleum Vessel Loading
and Unloading, and Cooling Towers, " (Order No. PB93-181592/AS; Cost:
$27.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/SR-93/063
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