1

Attachment

Technical Support Document for Potential to Emit 

Guidance Memo. Documentation of Emission Calculations.

Tim Smith, USEPA/OAQPS. April 1998
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Section 1. Introduction

This document provides the background calculations for the specific values for that appear

in EPA’s policy guidance memo, “Potential to Emit Guidance for Specific Source Categories,”

released in April 1998. In the guidance memo, the EPA calculated cutoffs that States can use to

establish prohibitory rule or general permit cutoffs that sources could use as enforceable

limitations on their operations, thereby achieving minor source status. 

This document covers calculations made for the following categories:

-- Gasoline Service Stations and Bulk Plants (Section 2)

-- Oil and Natural Gas Combustion in Industrial Boilers Having Capacity of 100

million BTU/hour or less (Section 3)

-- Cotton Gins (Section 4)

-- Coating Sources (Section 5)

-- Printing, publishing and packaging operations (Section 6)

-- Degreasers Using Volatile Organic Solvents (Section 7)

-- Hot Mix Asphalt Plants (Section 8)

The EPA author appreciates and acknowledges all of the technical contributions made by

EPA and State and local agency staff who assisted with this effort. In particular, the author

acknowledges the help from Steve Shedd, Jeff Herring, Mike Sewell, Dave Salman, Ron Myers

and Dallas Safriet of EPA/OAQPS, Martha Larson of EPA Region 9, Barbara Cook (California),

Mary Jean Fenske (Minnesota), Wayne Anderson and Randy Wolfe (Mississippi), Susan Fields

(Nebraska), Dick Everhart (Jefferson County, Kentucky) Jim Current and Neeraj Verma

(Georgia), Kevin Wood (New York), Richard Rasmussen (Virginia) and Edythe McKinney

(North Carolina). In addition, special thanks to Gary Jones of the Graphic Arts Technical

Foundation and Marci Kinter of the Screenprinting and Graphic Imaging Association

International. Finally, thanks to Reese Howle and staff of Alpha-Gamma technologies, Inc., who

were of great assistance in early brainstorming efforts on this project. If I forgot anybody, rest

assured, I didn’t mean to. 
3

Section 2. Gasoline Service Stations and Bulk Plants.

2.1. Gasoline Service Stations 

A. Pertinent Data and Calculations

The EPA agrees with findings of industry comments and the California Air Pollution

Control Officers Association (CAPCOA) that the major source determination for service stations

will always have volatile organic compounds (VOC) as the limiting case. (Ref: Fax with

attachments from John Huber, Petroleum Marketers Association of America to Tim Smith, EPA,

January 10, 1997). (Ref: Fax with attachments from Judy Yee, California Air Resources Board,

February 10, 1997.) This is because each individual hazardous air pollutant (HAP) contributes

less than 10% of the organic emission total, and the total across all HAP contributes less than

25%. The highest individual HAP percentage would be roughly 10% for MTBE for an area that

is nonattainment for ozone and CO. Accordingly, in an ozone attainment area (or moderate

ozone nonattainment area) with a 100 ton/yr VOC major source cutoff, that 100 ton/yr cutoff

would be reached before any individual HAP would reach 10 ton/yr, and before any combination

of HAP would reach 25 tons/yr. VOC would, of course, also be limiting for ozone nonattainment

areas for which the VOC cutoff was 50, 25 or 10 tons per year because HAPs would be a

proportionally smaller fraction of the major source cutoff when the major source VOC cutoff was

reached.

The EPA has calculated the number of “refueling stations” at a gasoline service station

that could result in emissions greater than major source amounts. The term “refueling position” is

used rather than the more ambiguous terms “pump” or “nozzle.” The number of “refueling

positions” is the number of vehicles that could be pumping simultaneously. For example, a

typical service station island with two dispensers has three nozzles on each side of both

dispensers. Such a two-dispenser design would yield four “refueling positions,” because a

maximum of four vehicles could be refueling at any given time. The results of these calculations

are presented in Table 1. 

The EPA has also calculated the number of gallons of gas pumped that would correspond

to the major source cutoff based upon the available emissions factors in Table 3. This value will

vary depending on the VOC major source cutoff, and depending on whether vapor recovery

during tank loading (Stage I vapor recovery) and vapor recovery during vehicle fueling (Stage II)

is required. These values are summarized in Table 2.

Finally, to put these values in perspective, the EPA reviewed data related to throughputs

at average-sized and large gasoline dispensing facilities. Data from broad surveys indicate

average gasoline sales of about 65,000 to 100,000 gallons/month [780,000 to 1.2 million

gallons/year] for “service stations,” while “pumpers” averaged 110,000 to 145,000 gallons/month

[1.3 to 1.7 million gallons/year]. (Ref: Market Facts ‘96. Facts, Figures and Trends.) Data for

the New Jersey Turnpike Authority facilities, judged to be among the largest in the nation,
4

indicated average gasoline sales of 264,000 to 550,000 gallons/month [3.2 to 6.9 million gallons

per year]. (Ref: December 10, 1996 letter and attachments from Edward Gross, Acting Director,

New Jersey Turnpike Authority to Eric DeGesero, Associate Director, Fuel Merchants

Association of New Jersey). According to the California Air Resources Board, there are only a

few gasoline stations that would approach or exceed the 7 million gallon per year cutoff in the

CAPCOA model rule. (Ref: Judy Yee, California Air Resources Board, personal communication

with Tim Smith, EPA. February 1997). It also may be useful to note that a gasoline tank truck’s

capacity is about 8000 gallons, and 240,000 gallons per month would represent a station with a

full tank truck unloading every day.

B. Recommended Approaches for Screening Cutoffs

For sources where gasoline dispensing operations account for more than 90% of all emissions, the

EPA recommends the following guidelines for a State or local prohibitory rule or general permit:

(A) The source’s total sales of gasoline in gallons/month must not exceed the following limits in

any calendar month: (the cutoff level varies depending on VOC major source cutoff and on the

type of vapor recovery required): (These values represent 50% of the values in table 2, and are

converted to a monthly basis to make the cutoffs correspond to records already being kept).

VOC Major Type of Control Gallons/Month

Source Level Required At 50% of

tons/yr) Major Source

100 No controls 380,000

100 Stage I 630,000

100 Stage I and Stage II 2,900,000

50 No controls 190,000

50 Stage I 310,000 

50 Stage I and Stage II 1,500,000 

25 No controls 95,000

25 Stage I 160,000

25 Stage I and Stage II 740,000

10 No controls 38,000

10 Stage I 63,000

10 Stage II 290,000
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(B) to demonstrate compliance with this limit, monthly records of throughput. [Records for many

if not most should be already available due to the EPA underground storage tank inventory

control requirements]. 

(C) A source may be considered low priority (no need for formal notification) if it contains less

than or equal to the number of refueling positions identified in table 1. 

2.2. Bulk Plants

A. Pertinent Data and Calculations

A “bulk plant” generally means a bulk gasoline loading facility that is smaller than a “bulk

terminal.” Air quality regulations define of “bulk terminals” as those with a capacity greater than

20,000 gallons per day, and define “bulk plants” as those less than or equal to 20,000 gallons per

day. (See 40 CFR 60.111b). In terms of emission characteristics, there are three types of bulk

plants, as follows:

(1) uncontrolled facilities,

(2) facilities with vapor balancing of storage tank and incoming tank trucks, and 

(3) facilities with vapor balancing of storage tank and incoming and outgoing tank trucks.

Emission factors for each of these three types are contained below in Table 4. The EPA believes

that all bulk plants in VOC nonattainment areas will have vapor balancing controls. In states with

regulations that mirror the CTG, facilities less than 4000 gallons per day require vapor balancing

of storage tank and incoming tank trucks, and facilities greater than 4000 gallons per day require

vapor balancing of outgoing tank trucks as well. 

A bulk plant (i.e., gasoline loading facility with a capacity of 20,000 gallons per day)

operating 365 days per year would have a maximum possible annual throughput of 7,300,000

gallons per year. Typical bulk plants operate at less than 20,000 gallons per day for 300 days per

year or fewer. Assuming the highest theoretical operation of 7.3 million gallons per year, and

using the emission factors in table 4, the maximum theoretical emissions from an uncontrolled

facility would be:

7,300,000 X 1/1000 thousand gallons X 2460 mg/l

 X 0.0083 [conversion from mg/l to lb/1000 gallon] X 1 ton/ 2000 lb = 75 tons VOC/year

Assuming that 4000 gallons per day is the maximum throughput for a facility for which

vapor balancing would not be required in a nonattainment area for outgoing trucks, then the

maximum possible annual throughput for such facilities is 4000 X 365 = 1.5 million gallons. The
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maximum possible emissions from such facilities, using the emission factor of 830 mg/l in table 4,

are as follows:

1,500,000 X 1/1000 X 830 X 0.0083 X 1/2000 = 5.2 tons/year

Finally, assuming the maximum theoretical throughput of 7,300,00 gallons per year, and

using the emission factor of 130 mg/l in table 4, are as follows:

7,300,000 X 1/1000 X 130 X 0.0083 X 1/2000 = 4 tons per year.

The results of the above three calculations illustrate that, even in a worst-possible case, no

facility whose actual throughput is less than 20,000 gallon per day definition of “bulk plant” will

be emitting major amounts of pollutants. 

B. Recommended Approach for Screening Cutoffs

For this category, it does not appear necessary to calculate a throughput level as a

“screening cutoff” because any source which meets the basic 20,000 gallons per day definition

would not be a major source. The basic definition itself should serve adequately as the basis for a

“limitation.”
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Table 2.1. Low priority gas stations

Type of

service station

Refueling positions

Attainment Marginal or Serious Severe Extreme

100 tpy 100 tpy 50 tpy 25 tpy 10 tpy

Moderate

Uncontrolled 17 17 9 4 2

Stage I 29 29 14 7 3

Stage I & II 134 134 67 34 13

Notes:

These calculations assume:

-- the average vehicle dispenses 10 gallons in one minute time period

-- each vehicle is replaced by another vehicle at every refueling position at the the service station

every 10 minutes over the entire year.

-- as a result, each refueling position pumps 10 gallons six times and hour, which is equivalent to

one gallon/minute at each position

These assumptions are based upon EPA’s technical judgment rather than actual data. The EPA

believes they represent very conservative upper bounds. The following calculation demonstrates

the conservative nature of the assumption:

1 gallon/minute X 60 minutes/hour X 24 hours/day X 30 days month = 43,200

gallons/month

Thus, the worst-case assumptions would result in a configuration with 10 refueling positions [5

2-sided pumps], pumping 432,000 gallons per month. This is a volume equivalent to the pumping

rates at a very large station on the New Jersey turnpike. In reality, such a small station would not

pump as much as a New Jersey turnpike station. The EPA believes, therefore, that this

calculation suggests that gasoline stations having no more refueling positions than indicated in the

above table would be unlikely to emit major source amounts, even if for some a physical

possibility may exist. Accordingly, the EPA believes that State prohibitory rules and general

permits may treat such stations as low priority sources: that is, the sources would be covered by

the prohibitory rule or general permit even if no formal notification was required. 
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Table 2.2. Gallons/year at major source threshold using EPA emission factors

Type of

service

station

Gallons/year of gasoline at the major source threshold

Attainment Marginal or Serious Severe Extreme

100 tpy 100 tpy 50 tpy 25 tpy 10 tpy

Moderate

Uncontrolled 9.1 million 9.1 million 4.5 million 2.3 million 0.91 million

Stage I 15 million 15 million 7.5 million 3.8 million 1.5 million

Stage II 71 million 71 million 35 million 18 million 7.1 million
 US EPA, “Gasoline Distribution Industry (Stage I) -Background Information for 1

Proposed Standards”, EPA 453/R-94-002a, January 1994, page 3-35 unless otherwise noted.

 Assuming 50% splash loading (1556 mg/l) and 50% submerged fill (1556 mg/l x 41%) 2

 US EPA, “Technical Guidance - Stage I Vapor Recovery Systems for Control of Vehicle 3

Refueling Emissions at Gasoline Dispensing Facilities, Volume I Chapters”, EPA 450/3-91-022a,

November 1991, page 4-50. pg 4-35.

 US EPA, “Technical Guidance - Stage I Vapor Recovery Systems for Control of Vehicle 4

Refueling Emissions at Gasoline Dispensing Facilities, Volume I Chapters”, EPA 450/3-91-022a,

November 1991, page 4-50.

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Table 2.3. Service Station VOC Emissions 

from Gasoline Storage and Handling Operations

[Milligrams of VOC per Liter of Gasoline Transferred (mg/l)]

Source Uncontrolled STAGE I: Vapor STAGE I & I: Vapor

Emissions Balancing of Tank Balancing of Tank Truck, 1

Truck and UST UST, & Vehicle Refueling

% Red. Emissions % Red. Applied Emissions

Applied

UNDERGROUND STORAGE TANKS (UST) LOSSES:

 Truck Unloading/ 1100 95% 55 95% 55

UST Filling Loss

2 3 3

Breathing/Emptying 120 0% 120 86% 17 4

VEHICLE REFUELING LOSSES:

Displacement 1340 0% 1340 86% 188 4

Spillage 80 0% 80 0% 80

TOTAL: 2640 40% 1600 87% 340
 US EPA, “Gasoline Distrbution Industry (Stage I) -Background Information for 5

Proposed Standards”, EPA 453/R-94-002a, January 1994, page 3-33 unless otherwise noted.

Reference 8, pg 4-34. 6

 Calculated using footnote a from reference 1 above, plus new emission factors in US 7

EPA, “Gasoline Distribution Industry (Stage I) -Background Information for Promulgated

Standards”, EPA 453/R-94-002b, November 1994, page C-9. [ 5.3x10-4 lb./hr x 300d/yr x

24hr/d x 4 pumps x 0.454 kg/lb x 10*6 mg/kg / (5,000 gal/day x 300d/yr x 3.785 l/gal)] and same

calculation for valves except 9.2*10-5 lbs/hr and 50 valves. 

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Table 2.4. Bulk Plant VOC Emissions 

from Gasoline Storage and Handling Operations

[Milligrams of VOC per Liter of Gasoline Transferred (mg/l)]

Source Uncontrolled Vapor Balancing of Vapor Balancing of

Emissions Storage Tank and Storage Tank and 5

Incoming Tank Truck Incoming and Outgoing 

Tank Truck

% Red. Emissions % Red. Emissions

Applied Applied

STORAGE TANKS:

 Emptying losses 432 22 22

95%695%2

 Breathing losses 203 10 10

 Filling losses 1081 54 54

TRUCK LOADING :

 Submerged fill 738 0% 738 95% 37 2

EQUIPMENT LEAKS :

7

 Pumps: 1.2 0% 1.2 0% 1.2

 Valves: 2.6 0% 2.6 0% 2.6

TOTAL: 2,460 66% 830 95% 130
Two major categories of fuel oil are burned by combustion sources: distillate and residual 8

oils. These oils are further distinguished by grade numbers, with Nos. 1 and 2 being distillate oils;

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Section 3. Oil and Natural Gas Combustion

in Industrial Boilers Having Capacity of 100 million BTU/hour or less

The purpose of this section is to document the calculations leading to guidance for

establishing general limitations for small industrial and commercial boilers combusting natural gas

and/or fuel oil. This section does not address emissions from boilers with capacity greater than

100 million BTU/hour, nor does it address emissions from solid fuels such as coal and wood, or

liquid petroleum gas (LPG). In addition, this section does not address emissions from other types

of combustion devices such as gas turbines, pumps, compressor or internal combustion engines. 

The calculations contained in this section are support for EPA guidance aimed at creating

streamlined approaches for limiting the potential to emit for low-emitting small businesses.

3.1. Pertinent Data and Calculations

A. Emission Factors for Natural Gas combustion. 

For natural gas combustion, NOx is the primary pollutant of concern for major source

determination. The emission factor for industrial boilers that are 100 million BTU/hour or less is

140 lb of NO per million cubic foot of natural gas combusted, while the emission factor for X

“large industrial and utility boilers” greater than 100 million BTU/hour is 550 lb of NO per X

million cubic foot. (Ref: AP-42, Section 1.4). For “small industrial boilers” (10-100

MMBTU/hr) the emission factors listed in AP-42, table 1.4-1 are as follows:

Pollutant Emission factor (lb/million cubic feet)

SO2 0.6

NOX (uncontrolled) 140

CO 35

PM 14 [filterable + condensible]

VOC < 5.8 [total organics = 5.8]

B. Fuel Oil Emission Factors

For fuel oil combustion, sulfur dioxide is usually the pollutant most likely to trigger major

source status, but NO can be important in some cases, particularly where stringent fuel sulfur X

regulations are in place. Emissions factors for SO and NO tend to be greater for residual oil 2 X

than for distillate oil. 

The emission factors for distillate oil are as follows: 8
Nos. 5 and 6 being residual oils; and No. 4 being either distillate oil or a mixture of distillate and

residual oils. No. 6 fuel oil is sometimes referred to as Bunker C. Distillate oils are more volatile

and less viscous than residual oils. They have negligible nitrogen and ash contents and usually

contain less than 0.3 percent sulfur (by weight). Distillate oils are used mainly in domestic and

small commercial applications, and include kerosene and diesel fuels. Being more viscous and less

volatile than distillate oils, the heavier residual oils (Nos. 5 and 6) may need to be heated for ease

of handling and to facilitate proper atomization. Because residual oils are produced from the

residue remaining after the lighter fractions (gasoline, kerosene, and distillate oils) have been

removed from the crude oil, they contain significant quantities of ash, nitrogen, and sulfur.

12

Pollutant Emission factor (lb/1000 gallons)

SO 142 times S [where S= weight percent of suflur in fuel. For 2

example, for 0.5% sulfur, S=0.5 and the emission factor is

71]

NOX (uncontrolled) 20

CO 5

PM 2 [filterable]

VOC 0.2 [non-methane organics]

For residual oil, the emission factors are:

Pollutant Emission factor (lb/1000 gallons)

SO2 157 times S

NOX (uncontrolled) 55

CO 5

PM 9.19(S) + 3.22 [filterable]

VOC 0.28 [non-methane organics]

OAQPS emission factor staff have indicated that 4% sulfur for residual oil, and 1 % sulfur for

distillate oil, represent the highest values from the top of the range of data on fuel sulfur. These

would equate to emission factors of (157)(4), or 628 lb/1000 gallon for sulfur dioxide for residual

oil, and (142)(1), or 142 lb/1000 gallon for distillate oil.

Based upon reviewing the above emission factors, and based upon review of calculations

for State programs outlined below, the EPA has concluded that for the major source

determination for natural gas, distillate and residual oil combustion in industrial boilers, sulfur

dioxide and nitrogen dioxide are the pollutants that would trigger the major source status first. 

Any fuel use that would result in minor emissions for these two pollutants will result in minor
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amounts for all other pollutants as well. Accordingly, the discussion that follows contains

calculations for these two pollutants only.

C. Combined emission factors for facilities capable of burning both natural gas and fuel oil

Many facilities have the capability of burning both fuel oil and natural gas. As discussed

above, in determining whether a given amount of fuel burned will exceed the major source

threshold, it is necessary to address NO and SO emissions. X 2

For facilities with the capability of burning natural gas and distillate oil, for a given amount

of fuel burned , emissions of NO and SO are the following: X 2

NO : X

[----- 1000 gallons distillate oil X 20 lb/1000 gallons + ----- million cubic feet natural gas

X 140 lb/million cubic foot ] X 1 ton/2000 lb

SO : 2

[----- 1000 gallons distillate oil X 142S lb/1000 gallons + ----- million cubic feet natural

gas X 0.6 lb/million cubic foot ] X 1 ton/2000 lb

For facilities with the capability of burning natural gas and bot h distillate and residual oil, for a

given amount of fuel burned , emissions of NO and SO are the following: X 2

NO : X

[----- 1000 gallons distillate oil X 20 lb/1000 gallons + ---- 1000 gallons residual oil X 55

lb/1000 gallons + ----- million cubic feet natural gas X 140 lb/million cubic foot ]

 X 1 ton/2000 lb

SO : 2

[----- 1000 gallons distillate oil X 142S lb/1000 gallons + ----- 1000 gallons residual oil X

157S lb/1000 gallons + ----- million cubic feet natural gas X 0.6 lb/million cubic foot ]

 X 1 ton/2000 lb

Because SO2 emissions tend to be greater for residual oil, and NOX tends to be greater

for natural gas, it is possible to devise prohibitory rule/general permit type limitations that allow

significant amounts of both natural gas and fuel oil to be combusted. 

3.2. Review of State and Local Approaches to Addressing Oil and Natural Gas Combustion in

Industrial Boilers
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In structuring guidance for use in general permits and prohibitory rules, it is useful to

review the approaches State and local agencies have already taken. All use very similar

calculations, but no two prohibitory rules are structured the same, and all address slightly different

fuel usage scenarios. 

Georgia. The Georgia “permit-by-rule”system addresses two scenarios for combustion of

natural gas and fuel oil (a) facilities with capability of burning distillate oil and natural gas

or (b) facilities with capability of burning residual oil and natural gas. The rule only

applies to boilers with capacity less than or equal to 100 million BTU/hour. As indicated

in documentation provided by the Georgia Air Protection Branch, values are calculated

based upon 80% of the major source threshold. The residual oil calculations assume 2.5%

sulfur. The calculations address 100 ton and 50 ton NOX areas, but do not address 10 and

25 ton areas because such areas do not exist in Georgia. Cutoffs in the rule, which

sources may qualify for by sending in a written certification, are as follows:

Distillate and Natural Gas:

100 ton NO areas: 900 million cubic feet natural gas X

1.6 million gallons distillate oil

 50 ton NO areas: 450 million cubic feet natural gas X

800,000 gallons distillate oil

Residual Oil and Natural Gas:

100 ton NO areas: 1000 million cubic feet natural gas X

400,000 million gallons residual oil

 50 ton NO areas: 400 million cubic feet natural gas X

400,000 gallons residual oil

New York. New York’s regulation 201.7.3 is a system for “emissions capping by rule”

which is designed to provide sources with a streamlined approach to limiting their

emissions to 50% of the major source threshold. The New York “capping” approach

provides specific values for use by facilities burning (a) distillate oil exclusively (b) residual

oil exclusively, and (c) natural gas exclusively. In addition, there is a paragraph for “dualfueled units” allowing sources to document that total use of the “dual fuels” would not

lead to annual emission greater than 50% of the major source threshold for every twelve

month period. The New York program differs from Georgia in that no attempt was made

to provide specific cutoffs that could be used for dual-fuel situations. Another difference

to note is that the New York program does not appear to disallow utility-sized boilers

from being covered, and consequently uses larger emission factors for NO for natural gas X

(550 lb/million cubic foot rather than 140 lb/million cubic foot). In New York, sulfur in
15

fuel limits exist for both distillate oil (weight percent 0.2, 0.37, 1.0, 1.1 and 1.5, depending

on the location within the State) and residual oil (weight percent 0.3, 0.37, 1, 1.1 and 1.5,

depending on the location). In evaluating NOX, it was necessary for the State to make

calculations for both severe ozone nonattainment areas (where the 50% cap equates to

NOX emissions of 12.5 tons/year) and attainment and “marginal” areas (where the 50%

cap equates to 50 tons/year NOX). Because the sulfur weight percentages vary among the

various “severe” areas, it was necessary for the residual oil to perform calculations for

each area to ascertain whether NOX or SO2 was the limiting case. The following is a

summary of the cutoffs in the New York program, and the basis for those cutoffs:

Fuel Cutoff Basis

Distillate 1,250,000 gal/yr 12.5 tons of NO . X

Emission factor: 20 lb/1000 gal

704,000 50 tons SO2

Weight limit: 1.0 %

Distillate (cont) 640,000 50 tons SO2

Weight limit: 1.1 %

469,000 50 tons SO2

Weight limit: 1.5%

Residual 333,000 gal/yr 12.5 tons of NO . X

Emission factor: 75 lb/1000 gal

579,000 50 tons SO2

Weight limit: 1.1 %

424,000 50 tons SO2

Weight limit: 1.5 %

Natural Gas 45 million cubic ft 12.5 tons of NOX

Emission factor: 550 lb/million cu ft

181 50 tons of NO X

Emission factor: 550 lb/million cu ft

California. The CAPCOA model prohibitory rule includes generally applicable “de

minimis” values for natural gas combustion (71,400,000 cubic feet) and distillate oil
16

(500,000 gallons). Sources may take advantage of these de minimis values if either

distillate oil or natural gas combustion comprises 90% of that stationary source’s

emissions. These values were calculated based upon 5 tons per year NO . A substantial X

fraction of the industrial boilers taking advantage of the CAPCOA model rule in any

District where it was adopted would probably take advantage of the generally applicable

provisions requiring monthly fuel usage and content records sufficient to show that for all

12-month periods, emissions are less than 50% of the major source threshold.

Wisconsin. The Wisconsin program does not contain a prohibitory rule or general permit

approach for boilers, but it does contain exemptions based upon capacity cutoffs. EPA

believes these cutoffs are intended to identify size cutoffs for boilers that could operate

continously at the maximum capacity and not emit major amounts. In Wisconsin

regulation 407.03, boilers are exempted from consideration if they burn the following fuels

and have a combined total capacity (sum of all boilers present) less than the indicated

amount:

Fuel Cutoff

Residual oil 5 million BTU/hour

Distillate 10 million BTU/hour

Natural gas 25 million BTU/hour

Other agencies. Doubtless, there are other prohibitory rules, general permits, etc., that

exist that have made similar calculations. For example, Knox County, Tennessee appears

to have adopted an approach very similar to the Georgia permit-by-rule. The above

discussion is not intended to be exhaustive. Rather, it is intended to illustrate the various

approaches that have been used.

3.3. Recommended Approach for Screening Cutoffs

A. Natural Minor Cutoffs

The exemption levels (5 MMBTU per hour for residual oil, 10 MMBTU/hour for

distillate, and 25 MMBTU/hour for natural gas) used by the State of Wisconsin appear to be

useful values to use to identify natural minors. These would appear to be reasonable values for

wider application, except in extreme ozone nonattainment areas. For extreme ozone

nonattainment areas, the 25 million BTU/hour cutoff for natural gas should be replaced by a value

of 10 million BTU/hour.
17

The following calculations document that total boiler capacities less than the cutoffs could

not result in major emissions. (Reference for all emission factors: AP-42, sections 1.3 and 1.4).

(Please note: these values are appropriate only for boilers less than 100 MMBTU/hr, and do not

apply to other types of combustion devices such as gas turbines and engines). The value of 5

million BTU/hour for residual oil, even assuming a conservative worst-case of 4% sulfur, yields

an annual sulfur dioxide total for a continuously operating boiler of less than 100 tons/year,

calculated as follows:

157S = (157)(4) = 628 lb/1000 gallon

Converting to lb/million BTU ----> (628 lb/1000 gallon) / 150 MMBTU/1000 gallon

= 4.2 lb/million BTU

4.2 lb/million BTU X 5 million BTU/hr X 8760 hours/yr X 1 ton/2000 lb = 92 tons/yr

Other criteria pollutants, including NO , would be emitted in lesser quantities. A residual oil X

capacity of 5 million BTU/hour would yield the following NOX emission rate if continously

operated:

Emission factor = 55 lb/1000 gallon

Converting to lb/million BTU -----> 55/150 = 0.37 lb/million BTU

0.37 lb/million BTU X 5 million BTU/hr X 8760/2000 = 8 tons/year

For distillate oil, using 1% sulfur, similar calculations can be used to document that a capacity of

10 million BTU/hour would result in non-major amounts:

142S = 142 (1) 142 lb/1000 gallon

Converting to lb/million BTU --> (142 lb/1000 gallon) / 140 MMBTU/1000 gallon = 1.01

lb/million BTU

1.01 lb/million BTU X 10 million BTU/hr X 8760 /2000 = 44 tons/year

Other pollutants would be emitted at lesser quantities than 44 tons/year. NOX emissions would be

as follows:

Emission factor = 20 lb/1000 gallon

Converting to lb/million BTU ----> 20/140 = 0.14 lb/million BTU

0.14 X 10 X 8760/2000 = 6.2 tons/year

For natural gas-firing , where NO is the pollutant with greatest emissions per unit fuel burned, X

the following demonstrates that a combined capacity of 25 lb/MMBTU yields non-major

emissions in all except extreme ozone nonattainment areas:

Emission factor = 140 lb/million cubic foot

Converting to lb/million BTU ---> 140/1000 = 0.14 lb/million BTU

0.14 X 25 X 8760/2000 = 15 tons per year
18

B. Guidance for Prohibitory Rules. Emissions < 50% Approach.

It would also be relatively straightforward to establish an approach in a prohibitory rule

under which a source would commit to demonstrating that actual fuel use resulted in emissions

less than 50% of the major source threshold. The source would merely need to plug the actual

fuel use values into the blanks in the equations in section I.C. above. The equations could be

listed in the rule, and sources could be required to keep records of fuel use necessary to plug into

the equations. 

C. Guidance for Prohibitory Rule Cutoffs. Simplified screening cutoffs.

To make it even easier on source owners, prohibitory rules could include a screening

approach in which the rule would include fuel usage caps. Rather than requiring sources to

calculate emissions, sources would merely be required to demonstrate that fuel usage is below the

cap. This is basically the approach used in the New York and Georgia rules. As illustrated by

these two rules, there are various forms these caps could take. In the New York rule, the cap

addresses boilers which burn natural gas exclusively, residual oil exclusively, or distillate oil

exclusively. For sources capable of burning more than one fuel, the system reverts to

demonstrating that emissions are less than 50 percent of the threshold. In the Georgia rule, the

cap addresses combined use of oil and natural gas, because it was judged that many facilities

opting into this cap would probably have dual fuel capbility. 

In order to calculate the screening fuel usage caps, the following questions must be answered:

(1) what fraction of the major source cutoff should serve as the basis for the calculation?

(2) should the cap approach include utility and large industrial boilers (for which the

calculations must take into account larger emission factors for NOX?

(3) what combination of fuels should be addressed?

(4) in designing a cap for a specific jurisdication for a given fuel combination:

-- what is the major source cutoff for NOX?

-- what is the fuel sulfur limit?

The EPA believes that this guidance is intended primarily for low-emitting small business emitting

well under the major source threshold. Accordingly, the guidance does not address large

industrial and utility boilers greater than 100 MMBTU/hr in the guidance. 
19

It appears that many agencies have used the 50% level as the demarcation for identifying the lowemitting small bsinesses for whom this guidance is primarily targeted. The following cutoffs

represent “tier 1" fuel use values that would ensure that emissions are less than 50% of the major

source threshold, and they are based upon fuel sulfur weight percentages of 1% for distillate, and

4% for residual oil. Separate values are calculated for each discrete possible fuel combination. 

Values listed in italics are based upon SO2 as the limiting pollutant, and hence the values could

increase if a State or local sulfur-in-fuel limitation is taken into account. 

It should be noted that equivalent numbers can be calculated for addressing dual-fuel capabilities,

and that for any given tons/yr amount, there is no unique “correct” answer. For example, for the

“natural gas and distillate oil” scenario listed below for 100 tpy areas, the values listed are 320

million cubic feet and 260,000 gallons. One could increase the natural gas value, while decreasing

the value for oil. So long as the fuel usage caps, when plugged into the equations in Section I.C.

above, yield values less than 50% of the major source cutoff, that would be an acceptable set of

values to use.

Fuel Capability Major Source 12-month

Cutoff for NOX Throughput Limit

Natural Gas Only 100 tpy 710 million cubic feet

 50 tpy 360 million cubic feet

 25 tpy 180 million cubic feet

 10 tpy 71 million cubic feet

Distillate only 100 tpy 700,000 gallons

 50 tpy 700,000 gallons

 25 tpy 700,000 gallons

 10 tpy 500,000 gallons

Residual only 100 tpy 160,000 gallons

 50 tpy 160,000 gallons

 25 tpy 160,000 gallons

 10 tpy 160,000 gallons

Natural Gas or 100 tpy 630 million cubic feet AND

Distillate Oil 600,000 gallons distillate

 50 tpy 320 million cubic feet and 

260,000 gallons distillate

 25 tpy 160 million cubic feet and

130,000 gallons distillate
20

 10 tpy 65 million cubic feet and

52,000 gallons distillate

Natural Gas or 100 tpy 650 million cubic feet and

Residual 160,000 gallons residual

 50 typ 300 million cubic feet and 

160,000 gallons residual 

 25 tpy 150 million cubic feet and

160,000 gallons residual

 10 tpy 51 million cubic feet and

51,000 gallons residual

Natural gas, residual [For this situation, the worst-case would

and distillate Be 100% use of residual oil. So EPA suggests

assigning the same values as the “natural gas or

residual” scenario, as “total oil burned” caps]

 

3.4. Hazardous Air Pollutants

Hazardous air pollutants do not appear to be at issue relative to the major source cutoff for oil or

natural gas-fired industrial boilers. The major source threshold for nitrogen oxides and sulfur

dioxide will be reached at a fuel usage amount much less than that which would trigger the major

source threshold for any individual HAP or for total HAPs.
21

Section 4. Cotton Gins

4.1 Pertinent Data and Calculations

AP-42 emission factors for PM-10 were revised during 1996. (Reference: AP-42 Section

9.7. Cotton Ginning. Revision July 1996). Two cotton gin configurations are listed in AP-42,

with different total emssion factors. Configuration “No. 1" is for cotton gins with all exhaust

streams controlled with high-efficiency cyclones. The “total No. 1" emission factor is 0.82 lbs

PM-10 per bale. Configuration “No. 2" is for cotton gins with screened drums or cages

controlling the lint cleaner and battery condenser exhausts, with cyclones on the remaining

exhaust streams. The total PM-10 emission factor for the “total no. 2" configuration is 1.2

pounds per bale. 

Another source of information on PM-10 emission factors was developed by the San

Joaquin Valley Unified Air Pollution Control District and the California Cotton Ginners

Association (CCGA). The San Joaquin Valley District and the CCGA maintain a complilation of

PM and PM10 source tests, referred to as the Cotton Gin Emission Factor Handbook. The

largest emission factor suggested based upon the California emission factor handbook is for

certain sources controlled by older cylones, and for “configuration” two described above. For

these cotton gins, the Handbook recommends, and the San Joaquin Air Pollution Control District

has accepted, an emission factor of 2.45 lb/bale (PM-10). This 2.45 lb/bale (PM-10) figure was

used for purposes of calculating emission reduction credits. 

4.2 Recommended Approach for Screening Cutoffs

The EPA believes that the 2.45 lb/bale value represents the most conservative value that

has been used (worst than the typical “worst-case”) for the gin configurations listed above. Note

that this value is about three times the AP-42 emission factor. Using this value, and based upon

90% of the major source threshold, the EPA calculates the following guidelines for prohibitory

rules:

200,000 pounds PM10 X 0.90 = N bales per year X 2.5 pounds per bale

N = 72,000 bales.

Similar calculations for a 70 ton “serious” PM-10 nonattainment area yield a guideline of 50,000

bales for those areas. [The EPA believes that the only serious PM10 areas containing cotton gins

are in California and Arizona.]

For cotton gins having cyclones on all exhausts (“configuration 1"), the EPA, based upon

discussions with the San Joaquin Air Pollution Control District and reviewing the California

guidelines, a very conservative upper-bound for these gins is 2 pounds per bale. This value is very

conservative (the AP-42 average value is 0.82 pounds per bale), but takes into account tests in
22

California for certain older 2D-2D designs. Using this 2 pound per bale figure, the EPA

calculates the following guidelines:

180,000 pounds = N bales per year X 2 pound/bale

N = 90,000 bales

For 70 ton/year serious PM-10 areas, this value becomes 0.7 times 90,000, or 63,000 bales.

The EPA notes that the practical effect of the guideline is not terribly sensitive to the

precise level selected. The great majority of existing cotton gins produce 40,000 bales or fewer. 

Thus, for any prohibitory value selected in the 50,000 to 100,000 bale range, almost all cotton

gins would have the opportunity to become subject to the prohibitory rule. 

Finally, the EPA notes that, consistent with current EPA regulation and policy, the above

calculations do not include fugitive emissions. Were EPA regulation or policy to change to

include such fugitives, these values may need to be re-calculated. 

4.3 Hazardous air pollutants. 

The EPA believes that hazardous air pollutants are not at issue for cotton gins. The only

pollutant emitted in any appreciable quantity is PM-10. Arsenic is no longer used in the industry,

and the EPA has concluded that there is not toxic component in the PM-10 that would approach

the HAP threshold.. 
23

Section 5. Surface Coating Sources

5.1 Pertinent Data and Calculations

Emission calculations for these sources are somewhat more straightforward than other

types of emitting sources. For purposes of major source applicability, the amount of VOC or

HAP solvents used in coating sources can be assumed to be emitted on-site. The VOC content

of coatings for many types of source categories, especially in ozone nonattainment areas, will be

subject to RACT limits. Many of the individual organic solvents are also on the HAP list, and so

it is necessary to consider both VOC and HAP in identifying whether a given plantsite is a major

source.

For the wood furniture NESHAP, the EPA determined that 3000 gallons per year was a

conservative estimate of the coatings usage that could trigger the 10 ton/year major source

threshold. This calculation was based on 9 tons/yr [90% of the major source threshold] and

assumed a worst case HAP content of 6 lb/gallon for any individual HAP constituent. 

For coatings, if the same 6 lb/gallon assumption is used, EPA has concluded that HAPs

are the limiting case for computing a screening value. This is clearly the case where the VOC

major source threshold is 25 tons/yr and greater. (For example, at 3000 gallons per 12-month

peirod, 25 tons ( 50,000 pounds), would require nearly 17 pounds VOC per gallon to reach the

major source threshold, a level that is probably not physically possible). The only possible

exception where VOC might be limiting is for extreme ozone nonattainment areas, where it may

be possible in some very limited cases for coatings to exceed 6 pounds of VOC per gallon. 

5.2 Recommended Approach for Screening Cutoffs

For sources where VOC in coatings, dilution solvent and cleaning solvent acount for more than

90% of all emissions, multi-tier approach

Tier 1: Screening approach. Usage records only.

-- Sources that commit to using less than 3000 gallons per each 12-month period are

presumed to be nonmajor sources regardless of material content. 3000 gallons includes

coating, dilution solvent and cleaning solvent. Records must be kept demonstrating usage

less than this value. 

Tier 2: Demonstrate that emissions remain below 50% of all applicable thresholds (without addon controls). 

Prohibitory rules can readily establish a second tier of coating sources using amounts

greater than the 3000 gallons screening cutoff, but agree to a limitation of less than 50% of the
24

major source threshold, and agree to keeping CONTENT and USAGE records showing < 50 %

of all applicable thresholds.. [Note that even under Tier 2, add-on controls are not considered]. 

An example worksheet for providing this documentation is included in “Guidance for State Rules

for Optional Federally-Enforceable Emissions Limits Based on Volatile Organic Compound Use,"

memo from D. Kent Berry, OAQPS, to EPA Regional Offices, October 15, 1993. [The EPA is

considering incorporating this worksheet, or a similar one, into user-friendly computer software

that could prompt the source owner with readily-answerable questions that could facility

compliance with the limit].

5.3 Considerations for Auto Refinishing Shops

The EPA believes that for one important surface coating category, automobile body and

repainting facilities, that many if not most of the sources in the source category have a very low

likekihood of emitting major amounts,

A. Background Information on the Industry

There are about 50,000 auto body shops in the United States. (Ref: Personal

communication with Mark Morris, EPA/OAQPS, 1997). The average number of jobs performed

by these facilities is 12 jobs per week, with the following distribution: (Ref: Body Shop Business . 

1993 Annual Industry Report.):

Table 5.1 NUMBER OF JOBS PERFORMED PER WEEK:

JOB RANGE ALL

SHOPS

< $100K - $ 150K - $250K - 350K - $750K +

$100,000 150K 250K 350 K 750K

1 - 25 jobs 89.8% 100% 100% 95.7% 93.9% 84.6% 62.2%

26- 50 jobs 8.7% 6.1% 13.9% 35.6%

51- 75 jobs 1.2% 4.3% 1.5%

76 - 100 jobs 0.3% 2.2%

TOTAL 100% 100% 100% 100% 100% 100% 100%

Average 11.6 3.7 jobs 7.3 jobs 9.7 jobs 10.2 jobs 15.1 jobs 25.4 jobs

jobs

EPA believes that for purposes of assessing the “potential” of an automobile re-painting

facility, it is necessary to address as separate cases two general types of facilities. The first type

includes auto body shop facilities that perform collision repair as their primary business, and must

get an exact color match with the original color. The second type of facility, which includes

facilities such as Earl Scheib, are primarily involved in repainting entire vehicles, but do not need

an exact color match with the existing color. It appears that the amount of paint used per job for
25

the two types of facilities may not differ greatly. For facilities which tend to paint entire cars,

primers do not tend to be used, fewer coats are applied, and followup for color matching is not

required. The time to complete a job, however, is greater on average for an auto body shop

because additional steps are needed to repair the vehicle before repainting. 

B. Considerations for Auto Body/Repair Shops

The EPA estimates, for auto body shops, that a conservative value unlikely to be

exceeded, is 9 pounds of VOCs are emitted for an average job. (Ref: calculations by Mark

Morris, EPA/OAQPS. December 1997. This estimation was made by reviewing information on

paint coverage, transfer efficiency, and VOC content; additional, the calculation assumes that

primer is used plus several additional coats). For screening purposes, the EPA assumed that

100% of the VOCs could be one of the HAPs, but that only 50% of the VOC total would be

contributed from any individual HAP. Note that this estimate is for facilities involved in

automobile repair, and is not appropriate for facilities capable of painting much larger surfaces

such as buses or earth-moving equipment. In addressing “extreme” ozone nonattainment areas,

the EPA considered the South Coast’s regulation of 3.5 lb/gallon in the calculations. For facilities

meeting this regulation, the EPA estimates that no more than 4.8 pounds of VOCs could be

emitted per average job. 

Using the these conservative assumptions, the EPA calculated the number of jobs that

would equate to the major source threshold as follows:

Table 5.2 

Major source threshold Emission Factor # of Jobs/Week

100 tons VOC 9 lb/job 427

50 tons VOC 9 lb/job 214

25 tons VOC 9 lb/job 107

10 tons VOC 4.8 lb/job 80

25 tons total HAP 9 lb/job 107

10 tons single HAP 4.5 lb/job 85

Example calculation:

100 tons VOC X 2000 lb/ton = 9 lb/job X ----- average jobs/week X 52 weeks/yr

------ = 100 X 2000 / (9X 52)

 = 427 jobs/week
26

The EPA believes that this table indicates that a facility with a potential to conduct 75 or

fewer jobs per week can be considered as a minor source.

Actual operations at almost all auto body shops are well below this level. The following

table, reproduced from the 1993 Body Shop Business report, displays the types of operations

typically present at an auto body shop.

Table 5.3 AVERAGE NUMBER OF BAYS DEVOTED TO SPECIFIC DUTIES

DUTY ALL

SHOPS

< $100K - $ 150K - $250K - 350K - $750K +

$100,000 150K 250K 350 K 750K

Body Work 4.5 1.7 2.9 3.6 4.6 5.3 9.8

Painting 2.0 0.9 1.5 1.6 1.8 2.6 4.2

Detailing 0.5 0.2 0.2 0.4 0.6 0.6 1.3

Prep Work 0.8 0.2 0.5 0.6 0.8 0.8 2.1

Mechanical 0.6 0.2 0.2 0.7 1.2 0.5 0.8

Work

Combination 1.4 1.1 1.6 2.2 1.6 1.1 1.2

of Duties

AVG TOTAL 9.8 4.5 6.8 9.1 10.7 11.0 19.4

BAYS

The EPA believes that the data in table 5.1 and 5.3, when viewed together, suggests that a

reasonable probability exists that the number of jobs performed per week by a single painting area

spray booth or spray area at an auto body/repair shop would not exceed 25 jobs per painting

station per week. Table 5.1 shows that only 1.5% of shops perform more than 50 jobs per week. 

Table 5.3 strongly suggests that those 1.5% of the total are performed at shops with several spray

paint booths-- the average number of “bays devoted to painting”, for the far right-hand column

(“>$750,000 in business) is more than 4. 

Using the 25 jobs/week/spray booth estimate, and the estimates of jobs/week that would

equate to major source amounts as indicated in table 5.2, the EPA calculates that no collision

damage repair facility with 2 or fewer paint booths, or is otherwise capable of painting 2 or fewer

automobiles at any one time, has any reasonable likelikhood of emitting major amounts, even if

for some facilities a physical capability may exist. Accordingly, the EPA believes that such

sources could be treated as low priority sources by State and local agency general permits and

prohibitory rules. 

The only type of shop where this estimate could have a reasonable probability of

underestimating the number of jobs per week would be those facilities for which collision repair,
27

and the associated extra preparation steps, are not present, and the facility is primarily involved in

repainting entire vehicles. For example, Earl Scheib facilities contain one spray booth, and are

designed for a capacity of 40-50 cars per week, although actual operations are about half of this

value. (Ref: personal communication with Jeffrey Pearl, Earl Scheib. December 1997). The

VOC and HAP contents of paint for such facilities appear to be less than the amount assumed for

table 5.2 above. The EPA recommends a more conservative approach for these repainting

facilities. That is, repainting facilities having only 1 paint booth could be treated as sources not

requiring notifications.
28

Section 6. Printing, Publishing and Packaging Operations 

6.1 Pertinent Data and Calculations

The printing, publishing and packaging industry is comprised of a number of production

process categories, including sheetfeed offset lithography, web offset lithography (heatset and

nonheatset), screen printing, flexography, and rotogravure printing. Process descriptions of these

various types of printers can be found in Profile of the Printing Industry, EPA/310-R-95-014.

The EPA agrees with the printing industry that the following equations represent a

conservative approach to emission calculations for the printing, publishing and packaging

industry: 

VOC Calculations For Nonheatset Web And Sheetfed Offset Lithographic Printing 

VOC Emissions = Amt of Ink* (lbs) x VOC Content (weight %) x 0.05** + 

 Amt of Hand Cleaning Solvent (gal) x VOC Content (lbs/gal) x 0.50***+

 Amt of Automatic Blanket Wash (gal) x VOC Content (lbs/gal) +

 Amt of Fountain Solution Concentrate (gal) x VOC Content (lbs/gal) +

 Amt of Fountain Solution Additive (gal) X VOC Content (lbs/gal)+

 Amt of Adhesive (lb) X VOC content (wt %)  +

 Amt of Coating (lb) X VOC content (wt %) ** **

* Include any conventional varnish used in the “amt of ink” total. 

** The 0.05 factor reflects 95% ink oil retention as documented in the draft CTG document

Control of Volatile Organic Compound Emissions from Offset Lithographic Printing, EPA453/D-95-001, page 5-2.

*** Use the 0.50 multiplier only if the VOC Composite Vapor Pressure Is Less Than 10 mm Hg

at 20 C, and only if the source owner is required to store shop towels in closed containers. o

**** If adhesives and coatings are purchased by the gallon, then use: 

Amt (gal) X VOC content (lb/gal)
29

HAP Calculations For Nonheatset Web And Sheetfed Offset Lithographic Printing 

Single HAP:

HAP Emissions =

Amt of Ink* (lbs) x HAP Content (weight %) x 0.05+ 

 Amt of Hand Cleaning Solvent (gal) x HAP Content (lbs/gal)** x 0.50***+

 Amt of Fountain Solution Concentrate (gal) x HAP Content (lbs/gal) +

Amt of Fountain Solution Additive (gal) X HAP Content (lbs/gal) +

Amt of Automatic Blanket Wash (gal) X HAP Content (lbs/gal)+ 

 Amt of Adhesive (lb) X HAP Content (wt %)  +

 Amt of Coating (lb) X HAP Content (wt %) ** **

* Include any conventional varnish used in the “amt of ink” total. There should be no HAPs in

lithographic inks -- confirm with supplier

** HAP Content (lbs/gallon) = wt. % HAP X product density.

*** Use the 0.50 multiplier only if the VOC Composite Vapor Pressure Is Less Than 10 mm Hg

at 20 C, and only if the source owner is required to store shop towels in closed containers. o

**** If adhesives and coatings are purchased by the gallon, then use use:

Amt (gal) X HAP Content (lb/gal)

Multiple HAPs:

HAP Emissions =

Amt of Ink* (lbs) x HAP Content (weight %) x 0.05 

 Amt of Hand Cleaning Solvent (gal) x HAP Content** (lbs/gal) x 0.50***+

 Amt of Fountain Solution Concentrate (gal) x HAP Content (lbs/gal) +

Amt of Fountain Solution Additive (gal) X HAP Content (lbs/gal) +

Amt of Automatic Blanket Wash (gal) X HAP content (lbs/gal)+

Amt of Adhesive (lb) X HAP content (wt %) +

 Amt of Coating (lb) X HAP content (wt %) ** **

* Include any conventional varnish used in the “amt of ink” total

** HAP Content (lbs/gallon) = wt. % HAP X product density.

*** Use the 0.50 multiplier only if the VOC Composite Vapor Pressure Is Less Than 10 mm Hg

at 20 C, and only if the source owner is required to store shop towels in closed containers. o
30

**** If adhesives and coatings are purchased by the gallon, then use: 

Amt (gal) X HAP Content (lb/gal)

VOC Calculations For Heatset Web Offset Lithographic Printing (uncontrolled) 

VOC Emissions =Amt of Ink* (lbs) x VOC Content (weight %) x 0.80 +

 Amt of Hand Cleaning Solvent (gal) x VOC Content (lbs/gal) x .50**+

 Amt of Automatic Blanket Wash (gal) x VOC Content (lbs/gal) + 

 Amt of Fountain Solution concentrate (gal) x VOC Content (lbs/gal) +

 Amt of Adhesive (lb) X VOC content (wt %)*** +

 Amt of Coating (lb) X VOC content (wt %) ***

 

* Include any conventional varnish used in the “amt of ink” total. The 0.80 factor reflects 20%

ink oil retention as documented in the draft CTG document Control of Volatile Organic

Compound Emissions from Offset Lithographic Printing, EPA-453/D-95-001, page 5-2.

** Use the 0.50 multiplier only if the VOC Composite Vapor Pressure Is Less Than 10 mm Hg at

20 C, and only if the source owner is required to store shop towels in closed containers. o

*** If adhesives and coatings are purchased by the gallon, then use:

Amt (gal) X VOC content (lb/gal)

HAP Calculations For Heatset Web Offset Lithographic Printing (uncontrolled)

Single HAP:

HAP Emissions = 

Amt of Ink* (lbs) x HAP Content (weight %) x 0.80 + 

 Amt of Hand Cleaning Solvent (gal) x HAP Content (lbs/gal) x 0.50**+

 Amt of Automatic Blanket Wash (gal) x HAP Content**lbs/gal) + 

 Amt of Fountain Solution concentrate (gal) x HAP Content**(lbs/gal) + 

 Amt of Adhesive (lb) X HAP content (wt %)*** +

 Amt of Coating (lb) X HAP content (wt %) ***

* Include any conventional varnish used in the “amt of ink” total. There should be no HAPs in

lithographic inks -- confirm with supplier
31

** HAP content (lbs/gallon) = wt. % HAP X product density. Use the 0.50 multiplier only if the

VOC Composite Vapor Pressure Is Less Than 10 mm Hg at 20 C, and only if the source owner is o

required to store shop towels in closed containers. 

*** If adhesives and coatings are purchased by the gallon, then use: 

Amt (gal) X HAP content (lb/gal)

Multiple HAPs:

HAP Emissions =

Amt of Ink* (lbs) x HAP Content (weight %) x 0.80 + 

 Amt of Hand Cleaning Solvent (gal) x HAP Content** (lbs/gal) x 0.50***+ 

 Amt of Automatic Blanket Wash (gal) x HAP Content (lbs/gal) + 

 Amt of Fountain Solution (gal) x HAP Content (lbs/gal) + 

 Amt of Adhesive (lb) X HAP content (wt %)  +

 Amt of Coating (lb) X HAP content (wt %) ** **

* Include any conventional varnish used in the “amt of ink” total. 

** There should be no HAPs in lithographic inks -- confirm with supplier

*** HAP content (lbs/gallon) = wt. % HAP X product density. Use the 0.50 multiplier only if

the VOC Composite Vapor Pressure Is Less Than 10 mm Hg at 20 C, and only if the source o

owner is required to store shop towels in closed containers. 

  If adhesives and coatings are purchased by the gallon, then use:

Amt (gal) X HAP content (lb/gal)

VOC Calculations For Screen Printing Operations 

VOC Emissions = Amt of Ink (gal) x VOC Content (lbs/gal) +

 Amt of Coating (gal) x VOC Content (lbs/gal) +

 Amt of Adhesive (gal) x VOC Content (lbs/gal) +

 Amt of Cleaning Solvent (gal) x VOC Content (lbs/gal)

 

HAP Calculations For Screen Printing Operations 

HAP Emissions = Amt of Ink (gal) x HAP Content (lbs/gal) +

 Amt of Coating (gal) x HAP Content (lbs/gal) +

 Amt of Adhesive (gal) x HAP Content (lbs/gal) +

 Amt of Cleaning Solvent (gal) x HAP Content (lbs/gal)
32

Note: HAP content (lbs/gal) = wt. % X product density

VOC Calculations For Solvent-Based Flexographic and Rotogravure Operations

(uncontrolled)

VOC Emissions = Amt of Ink (lbs) x VOC Content (weight %) +

 Amt of Coating (lbs) x VOC Content (weight %) +

 Amt of Adhesive (lbs) x VOC Content (weight %) +

 Amt of Diluents (gallons) x VOC Content (lbs/gal) +

 Amt of Cleaning Solvent (gal) x VOC Content (lbs/gal)+

 

[“Diluents” means ink, coating, and adhesive dilution solvents]

HAP Calculations For Solvent-Based Flexographic and Rotogravure Operations

(uncontrolled) 

HAP Emissions = Amt of Ink (lbs) x HAP Content (weight %) +

 Amt of Coating (lbs) x HAP Content (weight %) +

 Amt of Adhesive (lbs) x HAP Content (weight %) +

 Amt of Diluents (gallons) x VOC Content (lbs/gal) +

 Amt of Cleaning Solvent (gal) x HAP Content (lbs/gal) 

VOC Calculations For Water-Based Flexographic and Rotogravure Operations 

VOC Emissions = Amt of Ink (lbs) x VOC Content (weight %) +

 Amt of Coating (lbs) x VOC Content (weight %) +

 Amt of Adhesive (lbs) x VOC Content (weight %) +

 Amt of Diluents (lbs) x VOC Content (weight %) +

 Amt of Cleaning Solvent (gal) x VOC Content (lbs/gal)

HAP Calculations For Water-Based Flexographic and Rotogravure Operations 

HAP Emissions = Amt of Ink (lbs) x HAP Content (weight %) +

 Amt of Coating (lbs) x HAP Content (weight %) +

 Amt of Adhesive (lbs) x HAP Content (weight %) +

 Amt of Diluents (lbs) x VOC Content (weight %) +

 Amt of Cleaning Solvent (gal) x HAP Content (lbs/gal)
33

6.2 Recommended Approach for Screening Cutoffs

 The EPA recommends a two-tiered system for the various printing, publishing and

packaging categories. The EPA intends to develop software that would help small business

owners implement one of these two approaches, for use in States that have set up a prohibitory

rule or general permit system for printers.

Tier 1: Screening approach. Usage records only.

As shown in table 6.1, a list of indicator chemicals can be used to devise a tier one

screening level. This table takes into account both HAPs and VOCs. Sources who commit to

staying beneath these levels would need to maintain records of the total material use, and would

not need to provide records of material contents.

Tier 2: Demonstrate that emissions remain below 50% of all applicable thresholds.

The above equations can be used to demonstrate that a source is less than 50% of the

major source threshold. Sources exceeding the “tier 1" screening threshold would need to keep

records of material content and amounts to make use of the equations, and would need to

formally commit to keeping those records and maintaining emissions below the 50% cutoff.
34

Table 6.1 Input Material Indicators Associated with a “Cap” of 50% of the Major Source Threshold

[Amounts list ed are 12-month amounts]

Printing Process Extreme Severe Serious and OTR Moderate and Marginal Hazardous Air Pollutants

 10 TPY VOC 25 TPY VOC 50 TPY VOC 100 TPY VOC 10 TPY Single HAP

25 TPY HAPs Total

Sheetfed 1,425 gallons of 3,550 gallons of cleaning 7,125 gallons of 14,275 gallons of cleaning 1,333 gallons of material

(nonheatset) Offset cleaning solvent and solvent and fountain cleaning solvent and solvent and fountain containing single HAP.

Lithography fountain solution solution additives fountain solution solution additives 3,333 gallons of all HAP

additives ] additives containing materials

Nonheatset Web 1,425 gallons of 3,550 gallons of cleaning 7,125 gallons of 14,275 gallons of cleaning 1,333 gallons of material

Offset Lithography cleaning solvent and solvent and fountain cleaning solvent and solvent and fountain containing single HAP.

fountain solution solution additives fountain solution solution additives 3,333 gallons of all HAP

additives additives containing materials

Heatset Web Offset 10,000 pounds of ink, 25,000 pounds of ink, 50,000 pounds of ink, 100,000 pounds of ink, 1,333 gallons of material

Lithography -- cleaning solvent, and cleaning solvent, and cleaning solvent, and cleaning solvent, and containing single HAP.

uncontrolled fountain solution fountain solution fountain solution fountain solution additives 3,333 gallons of all HAP

additives additives additives containing materials

Screen 1,425 gallons of solvent 3,550 gallons of solvent 7,125 gallons of solvent 14,275 gallons of solvent 1,333 gallons of material

from the sum of: (a) from the sum of: (a) from the sum of: (a) from the sum of: (a) containing single HAP.

solvent based inks, (b) solvent based inks, (b) solvent based inks, (b) solvent based inks, (b) 3,333 gallons of all HAP

cleaning solvent, (c) cleaning solvent, (c) cleaning solvent, (c) cleaning solvent, (c) containing materials

adhesives and (d) adhesives and (d) adhesives and (d) adhesives and (d) coatings

coatings coatings coatings

Flexography-- 40,000 pounds of the 100,000 pounds of the 200,000 pounds of the 400,000 pounds of the 1,333 gallons of material

Waterbased or sum of: (a) inks, (b) sum of: (a) inks, (b) sum of: (a) inks, (b) sum of: (a) inks, (b) containing single HAP.

UV-cured inks, coatings and (c) coatings and (c) coatings and (c) coatings and (c) adhesives 3,333 gallons of all HAP

coatings and adhesives adhesives adhesives containing materials

adhesives
Printing Process Extreme Severe Serious and OTR Moderate and Marginal Hazardous Air Pollutants

 10 TPY VOC 25 TPY VOC 50 TPY VOC 100 TPY VOC 10 TPY Single HAP

25 TPY HAPs Total

35

Flexography -- 10,000 pounds of the 25,000 pounds of the 50,000 pounds of the 100,000 pounds of the 1,333 gallons of material

Solvent Inks -- sum of (a) ink, (b) sum of (a) ink, (b) sum of (a) ink, (b) sum of (a) ink, (b) containing single HAP.

uncontrolled coatings, (c) adhesives, coatings, (c) adhesives, coatings, (c) adhesives, coatings, (c) adhesives, (d) 3,333 gallons of all HAP

(d) dilution solvents and (d) dilution solvents and (d) dilution solvents and dilution solvents and (e) containing materials

(e) cleaning solvents (e) cleaning solvents (e) cleaning solvents cleaning solvents

Rotogravure -- 40,000 pounds of the 100,000 pounds of the 200,000 pounds of the 400,000 pounds of the 1,333 gallons of material

Waterbased or sum of: (a) inks, (b) sum of: (a) inks, (b) sum of: (a) inks, (b) sum of: (a) inks, (b) containing single HAP.

UV-cured inks, coatings and (c) coatings and (c) coatings and (c) coatings and (c) adhesives 3,333 gallons of all HAP

coatings and adhesives adhesives adhesives containing materials

adhesives

Rotogravure -- 10,000 pounds of the 25,000 pounds of the 50,000 pounds of the 100,000 pounds of the 1,333 gallons of material

Solvent Inks -- sum of (a) ink, (b) sum of (a) ink, (b) sum of (a) ink, (b) sum of (a) ink, (b) containing single HAP.

Uncontrolled coatings, (c) adhesives, coatings, (c) adhesives, coatings, (c) adhesives, coatings, (c) adhesives, (d) 3,333 gallons of all HAP

(d) dilution solvents and (d) dilution solvents and (d) dilution solvents and dilution solvents and (e) containing materials

(e) cleaning solvents (e) cleaning solvents (e) cleaning solvents cleaning solvents

Notes on assumptions made in constructing this table:

1. For purposes of these calculations, where the term “cleaning solvent” appears, the weight of the cleaning solvent is assumed

to be 7.0 lbs/gallon, 100% VOC and all evaporated. 

2. “ Fountain solution additives” include isopropyl alcohol, n-propyl alcohol, n-butanol, and alcohol substitutes. The weight of

isopropyl alcohol is 6.6 lbs/gallon, but for purposes of this table, the density is assumed to be 7.0 lbs/gallon, the density of

EGBE (alcohol substitute), 7.5 lbs/gal, 100% VOC and all evaporated.

3. Where “adhesives” are listed for solvent-based operations, the weight of the solvent in the adhesive is assumed to be 7.0

lbs/gallon, 100% VOC and all evaporated.
36

[Example calculation based upon footnotes 1, 2 and 3: 1425 gallons of “cleaning solvent and fountain solution additive” times

the assumed 7.0 lbs/gallon density equates to 10,000 pounds (5 tons) VOC, or 50% of the major source threshold for VOC in

extreme ozone nonattainment areas. Similarly, 1425 gallons of “solvent based inks, cleaning solvent and adhesives” for

screening printing X 7 lb/gallon equates to 10,000 pounds].

4. The waterbased inks, coatings and adhesives are assumed to contain no more than 25% of the volatile fraction as VOC and

all is assumed to evaporate. (Reference: Control Techniques Guidelines for Graphic Arts--Rotogravure and Flexography. 

EPA-450/2-78-033). [Example calculation: 40,000 pounds of inks, coatings and adhesives for flexography-waterbased inks

times 25% is 10,000 pounds].

5. In calculating the gallons of HAP-containing materials, the screening values in this table are based upon 2-butoxyethanol as

the representative HAP, which weighs 7.5 lbs/gallon, all evaporated. [Example calculation: 10,000 pounds VOC divided by 7.5

lbs/gallon = 1333 gallons of single HAP-containing material. 25,000 pounds of VOC divided by 7.5 lbs/gallon = 3333 gallons of

total HAP-containing material]. 
37

Section 7. Degreasers Using Organic Solvents

7.1 Pertinent Data and Calculations

Emission calculations for degreasers are very straightforward. Basically, net usage of the

degreasing solvent equals the amount emitted. 

The number of gallons of degreasing solvent usage that equates to the major source

threshold will depend on the density of the degreasing material used. Non-halogenated solvents

tend to have relatively low densities, typically on the order of 7 pounds per gallon, while

halogenated solvents such as methyl chloroform, trichloroethane (TCE), methylene chloride have

relatively greater densities on the order of 11-12 pounds per gallon. In addition, all of the

halogenated solvents are on the HAPs list. For purposes of the values appearing in the CAPCOA

model rule, non-halogenated densities were assumed to have an average density of 7.36 pounds

VOC per gallon. The density of TCE, 12.3 pounds per gallon, was used in the CAPCOA model

rule for purposes of establishing usage limits for halogenated solvents relative to the 10 and 25

ton/year HAP thresholds. 

Using the CAPCOA density assumption of 7.36 lb/gallon, the following amounts of nonhalogenated solvents equate to the major source thresholds for VOC:

Major source cutoff Gallons per 12-month rolling period

for VOC Non-halogenated degreasing solvent

10 tons per year 2700

25 tons/year 6800

50 tons/year 14,000

100 tons/year 27,000

Using the CAPCOA assumption (i.e., density = 12.3 lb/gallon), the following amounts of

halogenated solvents equate to the HAPs thresholds:

Major source threshold Gallons per 12-month rolling period

Halogenated degreasing solvent

10 tons/yr, single HAP 1600

25 tons/yr, all HAPs 4100
38

7.2 Recommended approach to screening cutoffs

The CAPCOA model rule uses the following values as prohibitory rule cutoffs. These

values are designed to ensure that single HAP emissions are less than about 8 tons per year and

total HAP emissions are less than 17.5 tons per year.

-- Non-halogenated solvents: 2200 gallons of any one solvent-containing material (if no

halogenated solvents), and 5400 gallons of any combination of solvent-containing materials

-- Halogenated solvents used: 1200 gallons of any one solvent-containing material, and

2900 gallons of any combination of solvent-containing materials. 

[Note: these values would also ensure compliance with major source VOC threshold, except for

the 5400 gallon amount which would not be protective of the major source threshold for extreme

ozone nonattainment areas. Hence, adjustments should be made in applying these cutoffs in

extreme ozone nonattainment areas.] 

The EPA believes that the cutoffs in the CAPCOA model rule would be useful in other

jurisdictions as well. EPA believes that the great majority of small business sources with

degreasers will fall well below these cutoffs.

7.3 Emission-Based Approaches

Another approach, similar to that for coating and printing sources would be useful for

sources using amounts exceeding the screening levels, but able to document emissions less than

50% of the major source threshold. Such an approach would involve keeping records of

degreaser solvent usage and content sufficient to demonstrate that emissions are less than 50% of

the major source threshold. This “tiered” approach could also be used for sources for which

contributions to emission totals occur from both surface coating and degreasing. 
39

Section 8. Hot-Mix Asphalt Plants

8.1 Pertinent Data and Calculations

Hot-mix asphalt plants are described well in AP-42, section 11.1, and in a document

prepared by the National Asphalt Paving Association entitled Dealing with Title V Operating

Permits--the Synthetic Minor Alternative. There are about 3600 active asphalt plants in the

United States, of which 2,300 are batch plants, 1,000 are parallel flow drum mix plants, and 300

are counterflow drum mix plants. 

For purposes of major source applicability, the pollutants of greatest interest are PM-10,

CO, and SO2. Emission factors for other criteria pollutants, such as NOx and VOC, are much

less than those for these three pollutants. Hazardous air pollutants (metals, PAHs, benzene,

ethylbenzene, toluene xylene, and formaldehyde) are emitted in relatively small quantities relative

to criteria pollutants. 

8.1.A. PM10 Emission Calculations

In addressing particulate emissions, both stack and fugitive emissions must be addressed. 

The New Source Performance Standard (NSPS) for hot mix asphalt plants, codified in subpart I

of 40 CFR part 60, was promulgated during the 1970s. For major source identification purposes,

fugitive emissions must be addressed for any “ ... stationary source category which, as of August

7, 1980, is being regulated under section 111 or 112 of the Act...” It should be noted that for

such stationary source categories, fugitive emissions must be calculated for any source in the

category, and not just those subject to the NSPS. 

The State of Minnesota calculated fugitive emissions from material handling and

stockpiles, using the equation in section 13.2.4 of AP-42:

E = k (0.0032)[(U/5)** 1.3]/[(M/2)**1.4]

where: E = emission factor (lb/ton of material transferred)

k = particle size multiplier (0.35 for PM10)

U= mean wind spead (10 miles/hr was used for Minnesota)

M = material moisture content (1.5% assumed as worst case)

Using this equation a PM-10 factor of 0.00413 lb/ton of aggregate transferred was

derived. This factor was multiplied by two, based upon a conservative assumption that each ton

of aggregate is transferred twice, to yield an emission factor for material handling of 0.00816

lb/ton of hot mix asphalt produced.
40

Minnesota also calculated PM-10 emission from roads, using a conversative assumption

that there would be 1/2 mile of unpaved roads at the site. The unpaved road calculations, used

the following equation in AP-42, section 13.2.2:

Emission factor (lb PM-10 per vehicle mile traveled) = 

k (5.9) X (s/12) X (S/30) X (W/3)**0.7 X (w/4)**0.5 X (365-p)/365

where: k = 0.36 for PM-10

s = silt content (%). (Minnesota calculations assumed 4.8%)

S = mean vehicle speed (miles per hour). (Minnesota calcuations assumed 20 mph)

W = mean vehicle weight (tons). (Minnesota assumed 15 tons)

w = number of wheels. (Minnesota assumed 10 wheels)

p = number of days with $ -.-1" rain (Minnesota used 111)

As a result of these calculations, Minnesota derived an emission factor of 1.92 pounds of

PM10 per vehicle mile travel. Note that this emission factor is an uncontrolled factor which does

not take credit for measures such as road watering. This was then converted to units of pounds

PM10 per ton of hot mix asphalt, assuming 15 tons of asphalt per vehicle, and asuming each ton

of asphalt travels twice on all unpaved roads at the site, and assuming 1/2 mile of unpaved road,

as follows:

1.92 lb PM10/vehicle mile X 1vehicle/ 15 tons X 2 X 1/2 = 

0.128 lb PM10/(ton asphalt produced)

In addition to the fugitive emissions there are also stack emissions from hot mix asphalt

production, generally from a particulate control device controlling emissions from the dryer and

other emission points. Uncontrolled PM10 emission from batch mix plants, as indicated in table

11.1-2 of AP-42, are 4.5 lbs PM10 per ton of hot mix asphalt produced, while controlled

emissions are less than 0.1 lb PM10 per ton. 

For PM10 emissions from sources subject to the NSPS (that is, those for which

construction or modification commenced after June 11, 1973), the EPA believes that the NSPS

will assure that allowable PM10 emissions will be consistent with the “controlled emission” values

listed in AP-42. For sources not subject to the NSPS, the required PM10 emission rate will vary

from State to State. For example, in Minnesota, a process rate equation yields a required lb/ton

for PM (total PM, not PM10) for a non-NSPS plant operating at 200 tons per hour of 40 pounds

per hour, or 0.2 pounds PM per ton. In Mississippi, the process weight calculation for a similarlysized facility of 200 tons/hour would be as follows:

Allowable emissions = 4.1 X[ (200 tons/hr)**0.67] = 142 pounds/hour
41

Expressed as a lb ton figure, this value would be 142/200, or about 0.7 lb/ton.

In Georgia, the process rate equation is as follows:

E = 10 X P**0.4

For a process rate, P of 200 tons per hour, the Georgia allowable emission rate would be about 83

pounds per hour. Expressed as a lb/ton figure, this would equate to 83/200, or about 0.4 lb/ton.

8.1.B Sulfur Dioxide Calculations

Sulfur dioxide becomes an important pollutant to consider for hot mix asphalt plants with

fuel oil-fired dryers, particularly those with residual fuel capability. The sulfur dioxide emission

factor in AP-42, table 11.1-8, is 0.24 pounds per ton of asphalt produced, based upon a test for

which firing was with #6 fuel oil. Footnote (e) to table 11.1-7 states that dryers fired with other

fuel oils will have different emission factors. 

The Minnesota calculations for sulfur dioxide assumed that a batch plant burning #6

residual oil with a sulfur content of 1.8% sulfur. Based upon source test results in the State, a

further assumption was made that there would be a 20 percent reduction in sulfur dioxide

emissions due to adsorption by the aggregate in the dryer. The result of these assumptions was

an emission factor of 226.8 pounds SO per 1000 gallons of fuel burned. Finally, the calculations 2

assumed that 1.5 gallons of fuel oil must be burned for every ton of asphalt produced. For

purposes of comparison with AP-42, the EPA converted this emission factor to a lb/ton basis and

obtained an emission factor of (226.8/1000) X 1.5, or 0.34 lbs SO per ton asphalt produced. 2

Calculations provided to the EPA by the State of Mississippi were also reviewed. For the

Mississippi calculations, the SO emissions were calculated based upon the fuel capacity of several 2

example sized units. Example 1 in the calculations was a small batch plant with production

capacity of 60 tons/hour and fuel capacity of 50 MMBTU/hr. Example 2 was a larger batch plant

with production capacity of 190 tons per hour and fuel capacity of 86.3 MMBTU/hour. The

Mississippi calculations are more conservative than for Minnesota, in that a much higher % sulfur

is assumed (4.8 lb/MMBTU, or roughly 4.8% sulfur). The end result of the Minnesota

calculations is 1814 tons sulfur dioxide per year for a plan with a capacity of 190 tons per hour. 

The effective emission factor of these calculations, is, therefore

1814 tons/yr X 2000 lb/ton X 1 year/8760 hours = 414 lb/hour

414 lb/hour/ 190 tons/hour = 2.1 lb SO2 per ton
42

8.1.C. Carbon Monoxide Calculations

Carbon monoxide emission factors are listed in table 11.1-7 and 11.1-8 of AP-42. The

listed emission factors are larger for natural gas-fired dryers than for oil-fired dryers. The

emission factor listed for natural gas-fired dryers at batch plants is 0.34 lb CO per ton of hot mix

asphalt produced. For drum mix plants, the natural gas emission factor for CO is 0.056 lb/ton. A

draft revision to AP-42 is currently under review that would raise the value for batch mix plants to

0.50 pounds per ton. Although CO emission factors are less for drum mix, the EPA for purposes

of this guidance used the 0.50 value as a conservative case, rather than to develop guidance that

differentiate between the various types of plants. 

8.2 Recommended Approach for Screening Cutoffs

The EPA believes that 250,000 tons per 12-month rolling period is a possible demarcation

between hot mix asphalt plants that would achieve synthetic minor status by general permit or

prohibitory rule, while it may be reasonable to require those above 250,000 tons to seek synthetic

minor status by case-by-case permit. A high percentage of asphalt plants operate at less than this

level. (Ref: Personnel communication with Gary Fore, National Asphalt Paving Association). 

The calculations below suggest this to be a reasonable cutoff for prohibitory rules, with a few

possible exceptions.

Based upon the above assumptions, CO is generally the limiting case for purposes of

prohibitory rule or general permit limitations. Even with the draft CO emission factor of 0.5

lbs/ton, CO emission would be 250,000 tons X 0.5 lbs/ton X 1 ton/2000 lb, or 62.5 tons per year. 

This amount is considerably less than the major source threshold of 100 tons per year. For drum

mix plants, CO emissions would be an even lesser fraction of the major source threshold.

For PM-10, a production rate of 250,000 tons per year would yield:

-- (based upon the Minnesota emission factors above), there would be fugitive emissions

of 0.00826 lb/ton for material handling and 0.128 lb/ton for unpaved roads. Hence, fugitive

emissions are (0.00826 + 0.128) lb/ton X 250,000 tons/year X 1 ton/2000 lb, or about 17 tons per

year. 

-- for NSPS sources, potential stack emissions of PM10 would be less than 0.1 lb/ton, and

hence annual emissions would be less than 250,000 X 0.1/2000, or less than 12.5 tons per year.

-- for non-NSPS sources, allowable emissions are more difficult to assess, because it is

beyond the scope of this effort to explore any possible process weight table or other SIP limit that

may exist. It appears, however, that in most cases a limit of 250,000 tons per year would like

ensure nonmajor amounts even for non-NSPS sources. For example, the Mississippi SIP limit

which equates to roughly 0.7 pounds per ton of PM, would equate to 250,000 X 0.7/2000, or

about 82.5 tons per year of PM. Because some fraction of the total particulate emissions from an
43

asphalt plant dryer is likely to contain particles greater than 10 microns, 82.5 tons per year of PM

is likely to equate to a value of PM that is sufficient to be protective of the major source

threshold, even if fugitive emissions on the order of 17 tons per year are considered. The EPA

emphasizes, however, that before using the 250,000 tons per year value, the control agency must

conduct an assessment of the allowable PM10 emissions for pre-NSPS sources before concluding

that a 250,000 ton/year limit is adequate for a prohibitory rule. A comprehensive statement on

this issue is beyond the scope of EPA’s guidance effort.

For SO2, 250,000 tons of hot mix asphalt production would yield annual emissions, using

the 0.24 lb/ton figure in AP-42, of 30 tons per year. Using Minnesota’s emission factor (as noted

above, the 226.8 lb/1000 gallon emission factor is equivalent to 0.34 lb/ton), 250,000 tons of hot

mix asphalt production would equate to 43 tons per year. These calculations suggest that even

with residual oil firing capability, this level of production would be very unlikely to exceed 100

tons per year at this level of production. 

8.3 Observation about Minor NSR

Asphalt plants provide an excellent example as to why guidance for cutoffs for synthetic

minor limitations should NOT be construed as guidance for sources that do not need minor NSR

permits. Conversations with State and local agency personnel indicate that at nonmajor emission

levels, asphalt plants can be of concern for ambient concentrations of criteria pollutants such as

sulfur dioxide. For example, Minnesota requires demonstration of compliance with sulfur dioxide

ambient air quality standards through the use of EPA’s SCREEN3 model if fule exceeding 0.70

percent sulfur is burned by the asphalt dryer burner. If compliance is not demonstrated with

SCREEN3, the source has two options: (1) to limit the sulfur content to 0.7% or (2) obtain a

permit reflecting refined dispersion calculations.

In addition, the fact that control equipment is required by SIP regulations makes these

plants a source for which any new plant would logically be reviewed by a permit engineer before a

plant is constructed.