Boiler and heaters emissions calculator: guide to reporting

Use the calculator to help you when reporting emissions from boilers and heaters – both distillate oil-fired and residual oil-fired – to the National Pollutant Release Inventory (NPRI).

Reporting to the National Pollutant Release Inventory

If your facility meets the NPRI reporting requirements, you must report the total quantities of NPRI substances released (to air, water or land), disposed of, or transferred for recycling. Keep in mind that you must consider releases from all sources when reporting to the NPRI, not just those that result from the combustion of fuel oil. For more information about NPRI reporting requirements, refer to the guide for reporting to the NPRI.

General information about boilers and heaters

Boilers and heaters are typically used for supplying large amounts of heat or steam to processes, generating portable power and providing space heat for industrial facilities.The two major categories of fuel oil burned by combustion sources are distillate oils and residual oils, which can then be further differentiated by fuel grade.

Distillate oils are comprised of fuel oil Nos. 1 and 2, which include kerosene and diesel fuels.  Distillate oils are less viscous, but more volatile, than residual oils and are for the most part used in domestic and small commercial applications or as alternate fuel in industrial or large-scale commercial combustion sources.

Residual oils are comprised of fuel oils Nos. 5 and 6 (Bunker C). Residual oils are produced from the residue remaining after the lighter fractions (gasoline, kerosene and distillate oils) have been removed from crude oil and may need to be heated for ease of handling and to facilitate proper atomization. Residual oils are typically used in utility, industrial and large-scale commercial applications.

Fuel oil No. 4 is considered to be either distillate oil or a mixture of distillate and residual oils.

Categories of boilers and heaters by industrial sector

The below table lists the categories of boilers and heaters that may use fuel oil as the primary combustion fuel.

Table 1: Categories of boilers and heaters by industrial sector
Sector Capacity,MW (MMBtu/hr) Boiler or heater type Application
Utility > 29 (>100) Watertube Electricity generation
Industrial 2.9 - 29 (10 - 100) Watertube Electricity generation
Industrial 2.9 - 29 (10 - 100) Watertube Process steam
Industrial 2.9 - 29 (10 - 100) Watertube Space heat
Industrial 2.9 - 29 (10 - 100) Firetube Process steam
Industrial 2.9 - 29 (10 - 100) Firetube Space heat
Commercial / institutional 0.1 - 2.9 (0.5 - 10) Watertube Space heat
Commercial / institutional 0.1 - 2.9 (0.5 - 10) Firetube Space heat

Published emission factors

While there are many acceptable methods for estimating emissions when you report to the NPRI, the Boilers and heaters emissions calculator uses published emission factors. Published emission factors are those that have been published by government agencies and industry associations for use in their particular application or industry sector. These factors are commonly used and accepted by regulatory agencies and represent average or typical rates with recognized data quality parameters.

A review was conducted of the available emission factors related to air contaminants emitted from the combustion of fuel oils, specifically for boilers and heaters. The emission factors published by the United States Environmental Protection Agency (EPA), AP-42, were selected to be included in the emissions calculator. The Boilers and heaters emissions calculator includes a compilation of two sets of emission factor tables:

The AP‑42 emission factors are presented together with their respective data quality ratings in Appendices A and B. The data quality ratings, based on AP-42 documentation, are presented in Table 2.

Table 2: US EPA AP-42 emission factor data quality ratings
Rating Description
A: Excellent Factor derived from sound test data taken from many randomly selected facilities.
B: Above average Factor derived from sound test data taken from a “reasonable” number of facilities.
C: Average Factor developed from test data collected using unproven or new methods, or lacking background information, from a reasonable number of facilities.
D: Below average Factor developed from test data as above, from a small number of facilities.
E: Poor Factor developed from test data based on poor or new methodology, and from a small number of facilities that do not represent a random sample of the industry.

Calculate emissions for distillate and residual oil-fired boilers and heaters

EPA AP-42 Section 1.3 (9/98, revised 4/00) includes published emission factors for distillate oil- and residual oil-fired boilers and heaters. Most of the emission factors are presented in units of lb/10³ U.S. gallon.  

The emissions from external combustion equipment are calculated as follows in the Boilers and heaters emissions calculator:

Annual emissions (kg/year)
= fuel oil usage (m3/year) x EF (lb/103 U.S.gal) x 264.172 (U.S.gal/m3) x 0.454 (kg/lb)

The Boilers and heaters emissions calculator allows you to select the type of fuel oil (distillate and residual fuel oil grades) and the type of boiler or heater (industrial, commercial/institutional/residential or utility).

Distillate oil-fired boilers and heaters

Appendix A provides the published emission factors for boilers and heaters used in the Boilers and heaters emissions calculator. For some of the Criteria Air Contaminants (CACs), the emission factors vary based on the type of boiler or heater. This is consistent with the emission factors published in AP-42.

In cases where AP-42 provides a range of emission factors, such as for formaldehyde, the average value is used for the Boilers and heaters emissions calculator.

The emissions of Part 1 core substances, Part 2 polycyclic aromatic hydrocarbons (PAHs), Part 3 (dioxins/furans and hexachlorobenzene), and Part 5 speciated volatile organic compounds (VOCs) from distillate oil-fired boilers and heaters are based on the emission factors in Table 1.3-9 of AP-42 Section 1.3. Although the testing was based on No.6 residual oil-fired boilers, the table heading “Emission factors for speciated organic compounds from fuel oil combustion” indicates that the emission factors may be applied to calculate emissions from boilers or heaters fueled by all types of fuel oils, including distillate fuel oils.

Additionally, for some Part 1A and 1B releases, the emission factors are in units of lb/1012 Btu and require a heating value to determine the total release based on fuel consumption data. You should input a site-specific heating value where available. A default average high heating value (HHV) of 39 GJ/m3 is used in the Boilers and heaters emissions calculator.

There are no published emission factors for particulate matter less than or equal to 10 (PM10), particulate matter less than or equal to 2.5 (PM2.5) or VOCs for utility boilers that use distillate oil. As such, the emission factors for industrial boilers are used for these NPRI substances. This is a reasonable approach as the emission factors for other parameters, such as total particulate matter (TPM) and oxides of nitrogen (NOx), from utility and industrial boilers, are comparable.

Residual oil-fired boilers and heaters

Appendix B provides the published emission factors used in the Boilers and heaters emissions calculator for boilers and heaters that use residual oil as fuel.

For some of the contaminants, the emission factors vary based upon the type of boiler or heater. This is consistent with the emission factors published in AP-42.  An example is formaldehyde, where the emission factor for utility boilers using No.6 oil differs from the emission factor from other industrial, commercial and utility boilers.

Pollution control devices and estimated control efficiencies

If you use an emission control device and the default emission factor is uncontrolled, the emission factor equation may be adjusted to take the control efficiency into account, as follows:

E = A x EF x ((100 – control efficiency)/100)

where:

The Boilers and heaters emissions calculator gives you the ability to incorporate control efficiencies in the input tab. Common pollution control devices or measures, and the default control efficiencies used in the emissions calculator, are provided in Appendix C.

Where available, you should use site-specific control efficiencies that reflect the pollution control measures at your facility rather than the default values provided.

Sulphur content of fuel oils

The Boilers and heaters emissions calculator requires the sulphur content of the distillate and residual oils to calculate the sulphur dioxide (SO2) emissions.

If you know the sulphur content of the fuel, you should use that site-specific value. In the absence of site-specific data, sulphur content data downloaded from Open Canada are used to establish default values by region.

Although there are sulphur data available up to 2016, the 2003-2012 data are more robust and include data from several regions. The average value in each region for this 10-year period was carried forward as the default sulphur content for the Boilers and heaters emissions calculator.

Table 3 shows the default sulphur content for four fuel types that were used in the Boilers and heaters emissions calculator.

Table 3: Average sulphur content (%) of fuel oils;10 year average (2003-2012)
Type of fuel National Atlantic Quebec Ontario West
Light fuel oil 0.11967 0.1355 0.10567 0.1549 0.12055
Heavy fuel oil 1.50614 1.59612 1.11223 1.8921 1.61679
Ultra-low sulphur diesel 0.00043 0.00049 0.00033 0.00045 0.00051
Low-sulphur diesel 0.02539 0.02734 0.01434 0.03209 0.02173

Appendix A: Published emission factors for distillate oil-fired boilers and heaters

The data summarized in Tables A.1 to A.3 are published in the US EPA Compilation of Air Pollutant Emission Factors AP-42, Fifth Edition, Volume I:  Stationary Point and Area Sources, Section 1.3 – Fuel Oil Combustion, 9/98, revised 4/00 (Errata).

Table A.1: Non-metal emission factors for distillate oil-fired boilers and heaters
Contaminant CAS Number Uncontrolled emission factor lb/103 US gal Emission factor rating Reference
Sulphur dioxide (SO2) 7446-09-5 142 x % Sulphur A AP-42, Table 1.3-1
Oxides of nitrogen, expressed as NO2 (NOX) 11104-93-1 20.0 A AP-42, Table 1.3-1
Carbon monoxide (CO) 630-08-0 5.00 A AP-42, Table 1.3-1
Total particulate matter (TPM) NA - M08 2.00 A AP-42, Table 1.3-1
Acenaphthene 83-32-9 2.11E-05 C AP-42, Table 1.3-9
Acenaphthylene 208-96-8 2.53E-07 D AP-42, Table 1.3-9
Anthracene 120-12-7 1.22E-06 C AP-42, Table 1.3-9
Benzene 71-43-2 2.14E-04 C AP-42, Table 1.3-9
Benzo(a)anthracene 56-55-3 4.01E-06 C AP-42, Table 1.3-9
Chrysene 218-01-9 2.38E-06 C AP-42, Table 1.3-9
Benzo(b)fluoranthene 205-99-2 1.48E-06 C AP-42, Table 1.3-9
Benzo(g,h,i)perylene 191-24-2 2.26E-06 C AP-42, Table 1.3-9
Benzo(k)fluoranthene 207-08-9 1.48E-06 C AP-42, Table 1.3-9
Dibenzo(a,h)anthracene 53-70-3 1.67E-06 D AP-42, Table 1.3-9
Ethylbenzene 100-41-4 6.36E-05 E AP-42, Table 1.3-9
Fluoranthene 206-44-0 4.84E-06 C AP-42, Table 1.3-9
Fluorene 86-73-7 4.47E-06 C AP-42, Table 1.3-9
Formaldehyde 50-00-0 0.0480 E AP-42, Table 1.3-8
Indo(1,2,3-c,d)pyrene 193-39-5 2.14E-06 C AP-42, Table 1.3-9
Naphthalene 91-20-3 1.13E-03 C AP-42, Table 1.3-9
Octachlorodibenzo-P-Dioxin (OCDD) 3268-87-9 3.10E-09 E AP-42, Table 1.3-9
Phenanthrene 85-01-8 1.05E-05 E AP-42, Table 1.3-9
Pyrene 129-00-0 4.25E-06 C AP-42, Table 1.3-9
Toluene 108-88-3 6.20E-03 D AP-42, Table 1.3-9
Xylene (all isomers) 1330-20-7 1.09E-04 E AP-42, Table 1.3-9

 

Table A.2: Metal emission factors for distillate oil-fired boilers and heaters
Contaminant CAS Number Uncontrolled emission factor lb/1012 Btu Emission factor rating Reference
Arsenic NA - 02 4 E AP-42, Table 1.3-10
Cadmium NA - 03 3 E AP-42, Table 1.3-10
Chromium NA - 04 3 E AP-42, Table 1.3-10
Copper NA - 06 6 E AP-42, Table 1.3-10
Lead NA - 08 9 E AP-42, Table 1.3-10
Manganese NA - 09 6 E AP-42, Table 1.3-10
Mercury NA - 10 3 E AP-42, Table 1.3-10
Nickel NA - 11 3 E AP-42, Table 1.3-10
Selenium NA - 12 15 E AP-42, Table 1.3-10
Zinc NA - 14 4 E AP-42, Table 1.3-10

 

Table A.3: Emission factors for distillate oil-fired boilers and heaters for PM10, PM2.5 and VOCs
Contaminant CAS Number Boiler heater type Uncontrolled emission factor lb/103 US gal Emission factor rating Reference
PM10 NA - M09 Industrial 1.00 E AP-42, Table 1.3-6
PM10 NA - 09 Commercial 1.08 D AP-42, Table 1.3-7
PM2.5 NA - 10 Industrial 0.250 E AP-42, Table 1.3-6
PM2.5 NA - 10 Commercial 0.830 D AP-42, Table 1.3-7
Volatile organic compounds (VOCs) NA - M16 Industrial 0.200 A AP-42, Table 1.3-3
Volatile organic compounds (VOCs) NA - M16 Commercial 0.340 A AP-42, Table 1.3-3

Appendix B: Published emission factors for residual oil-fired boilers and heaters

 

The data summarized in Tables B.1 to B.6 are published in the US EPA Compilation of Air Pollutant Emission Factors AP-42, Fifth Edition, Volume I:  Stationary Point and Area Sources, Section 1.3 – Fuel Oil Combustion, 9/98, revised 4/00 (Errata).

Table B.1: Metal, PAHs, dioxin and speciated VOCs emission factors for residual oil-fired boilers and heaters
Contaminant CAS Number Uncontrolled emission
factor lb/103 US gal
Emission factor
rating
Reference
Acenaphthene 83-32-9 2.11E-05 C AP-42, Table 1.3-9
Acenaphthylene 208-96-8 2.53E-07 D AP-42, Table 1.3-9
Anthracene 120-12-7 1.22E-06 C AP-42, Table 1.3-9
Antimony NA - 01 5.25E-03 E AP-42, Table 1.3-11
Arsenic NA - 02 1.32E-03 C AP-42, Table 1.3-11
Benzene 71-43-2 2.14E-04 C AP-42, Table 1.3-9
Benzo(a)anthracene 56-55-3 4.01E-06 C AP-42, Table 1.3-9
Chrysene 218-01-9 2.38E-06 C AP-42, Table 1.3-9
Benzo(b)fluoranthene 205-99-2 1.48E-06 C AP-42, Table 1.3-9
Benzo(g,h,i)perylene 191-24-2 2.26E-06 C AP-42, Table 1.3-9
Benzo(K)fluoranthene 207-08-9 1.48E-06 C AP-42, Table 1.3-9
Cadmium NA - 03 3.98E-04 C AP-42, Table 1.3-11
Chromium NA - 04 8.45E-04 C AP-42, Table 1.3-11
Cobalt NA - 05 6.02E-03 D AP-42, Table 1.3-11
Copper NA - 06 1.76E-03 C AP-42, Table 1.3-11
Dibenzo(a,h)anthracene 53-70-3 1.67E-06 D AP-42, Table 1.3-9
Ethylbenzene 100-41-4 6.36E-05 E AP-42, Table 1.3-9
Fluoranthene 206-44-0 4.84E-06 C AP-42, Table 1.3-9
Fluorene 86-73-7 4.47E-06 C AP-42, Table 1.3-9
Formaldehyde 50-00-0 3.30E-02 C AP-42, Table 1.3-9
Hexavalent chromium NA - 19 2.48E-04 C AP-42, Table 1.3-11
Indo(1,2,3-c,d)Pyrene 193-39-5 2.14E-06 C AP-42, Table 1.3-9
Lead NA - 08 1.51E-03 C AP-42, Table 1.3-11
Manganese NA - 09 3.00E-03 C AP-42, Table 1.3-11
Mercury NA - 10 1.13E-04 C AP-42, Table 1.3-11
Naphthalene 91-20-3 1.13E-03 C AP-42, Table 1.3-9
Nickel NA - 11 8.45E-02 C AP-42, Table 1.3-11
Octachlorodibenzo-P-Dioxin (OCDD) 3268-87-9 3.10E-09 E AP-42, Table 1.3-9
Phenanthrene 85-01-8 1.05E-05 C AP-42, Table 1.3-9
Phosphorus NA - 22 9.46E-03 D AP-42, Table 1.3-11
Pyrene 129-00-0 4.25E-06 C AP-42, Table 1.3-9
Selenium NA - 12 6.83E-04 C AP-42, Table 1.3-11
Toluene 108-88-3 6.20E-03 D AP-42, Table 1.3-9
Xylene (all isomers) 1330-20-7 1.09E-04 E AP-42, Table 1.3-9
Vanadium NA - 40 3.18E-02 D AP-42, Table 1.3-11
Zinc NA - 14 2.91E-02 D AP-42, Table 1.3-11

 

Table B.2: Some CAC emission factors for residual oil-fired boilers and heaters (AP-42, Table 1.3-1)
Contaminant CAS Number Fuel grade Uncontrolled emission factor lb/103 US gal Emission factor rating
Sulphur dioxide (SO2) 7446-09-5 No. 6 157 x % Sulphur A
Sulphur dioxide (SO2) 7446-09-5 No. 5 157 x % sulphur A
Sulphur dioxide (SO2) 7446-09-5 No. 4 150 x % sulphur A
Oxides of nitrogen, expressed as NO2 (NOX) 11104-93-1 No. 6 55 A
Oxides of nitrogen, expressed as NO2 (NOX) 11104-93-1 No. 5 55 A
Oxides of nitrogen, expressed as NO2 (NOX) 11104-93-1 No. 4 20 A
Carbon monoxide (CO) 630-08-0 No. 6 5 A
Carbon monoxide (CO) 630-08-0 No. 5 5 A
Carbon monoxide (CO) 630-08-0 No. 4 5 A
Total particulate matter (TPM) NA - M08 No. 6 9.19 x % sulphur + 3.22 C
Total particulate matter (TPM) NA - M08 No. 5 10 C
Total particulate matter (TPM) NA - M08 No. 4 7 D

 

Table B.3: Fuel grade factors (A) for residual oil-fired boilers and heaters
Residual oil A - Fuel grade factor for tables B.4 and B.5
No.6 1.12 x % sulphur + 0.37
No.5 1.2
No.4 0.84

 

Table B.4: PM10 emission factors for residual oil-fired boilers and heaters
Type of boiler or heater Fuel grade Uncontrolled emission
factor lb/103 US gal
Emission factor
rating
Reference
Industrial No. 6 7.17 x A D AP-42, Table1.3-5
Industrial No. 5 7.17 x A D AP-42, Table1.3-5
Industrial No. 4 7.17 x A D AP-42, Table1.3-5
Commercial, institutional, residential No. 6 5.17 x A D AP-42, Table1.3-7
Commercial, institutional, residential No. 5 5.17 x A D AP-42, Table 1.3-7
Commercial, institutional, residential No. 4 5.17 x A D AP-42, Table 1.3-7
Utility No. 6 5.9 x A C AP-42, Table 1.3-4
Utility No. 5 5.9 x A C AP-42, Table 1.3-4
Utility No. 4 5.9 x A C AP-42, Table 1.3-4

 

Table B.5: PM2.5 emission factors for residual oil-fired boilers and heaters
Type of boiler or heater Fuel grade Uncontrolled emission
factor lb/103 US gal
Emission factor
rating
Reference
Industrial No. 6 4.67 x A D AP-42, Table1.3-5
Industrial No. 5 4.67 x A D AP-42, Table1.3-5
Industrial No. 4 4.67 x A D AP-42, Table1.3-5
Commercial, institutional, residential No. 6 1.92 x A D AP-42, Table1.3-7
Commercial, institutional, residential No. 5 1.92 x A D AP-42, Table 1.3-7
Commercial, institutional, residential No. 4 1.92 x A D AP-42, Table 1.3-7
Utility No. 6 4.3 x A C AP-42, Table 1.3-4
Utility No. 5 4.3 x A C AP-42, Table 1.3-4
Utility No. 4 4.3 x A C AP-42, Table 1.3-4

 

Table B.6: VOCs* emission factors for residual oil-fired boilers and heaters
Type of boiler or heater Fuel grade Uncontrolled emission
factor lb/103 US gal
Emission factor
rating
Reference
Industrial No. 6 0.28 A AP-42, Table1.3-3
Industrial No. 5 0.28 A AP-42, Table1.3-3
Industrial No. 4 0.20 A AP-42, Table1.3-3
Commercial, institutional, residential No. 6 1.13 A AP-42, Table1.3-3
Commercial, institutional, residential No. 5 1.13 A AP-42, Table 1.3-3
Commercial, institutional, residential No. 4 0.34 A AP-42, Table 1.3-3
Utility No. 6 0.76 A AP-42, Table 1.3-3
Utility No. 5 0.76 A AP-42, Table 1.3-3
Utility No. 4 0.76 A AP-42, Table 1.3-3

(*) These emission factors are given as “non-methane total organic compounds” in AP-42

Appendix C: Summary of published control efficiencies for boilers and heaters

The data summarized in Tables C.1 to C.4 are published in the US EPA Compilation of Air Pollutant Emission Factors AP-42, Fifth Edition, Volume I:  Stationary Point and Area Sources, Section 1.3 – Fuel Oil Combustion, 9/98, revised 4/00 (Errata).

 

Table C.1: NOX control efficiency for boilers and heaters
Control technique Control efficiency %
- Residual oil
Control efficiency %
- Distillate oil
Reference
Low excess air (LEA) Range: 0 – 28
Median: 14
Range: 0 – 24
Median: 12
AP-42, Table1.3-14
Low NOx burners (LNB) Range: 20 – 50
Median: 35
Range: 20 – 50
Median: 35
AP-42, Table1.3-14
Staged combustion (SC) Range: 20 – 50
Median: 35
Range: 17 – 44
Median: 31
AP-42, Table1.3-14
Flue gas recirculation (FGR) Range: 15 – 30
Median: 23
Range: 58 – 73
Median: 66
AP-42, Table1.3-14
Flue gas recirculation plus staged combustion Range: 25 – 53
Median: 39
Range: 73 – 77
Median: 75
AP-42, Table 1.3-14
Selective noncatalytic reduction (SNCR) Range: 40 – 70
Median: 55
Range: 40 – 70
Median: 55
AP-42, Table 1.3-14
Fuel alteration - water emulsion 41 no data AP-42, Table 1.3-14

 

Table C.2: Sulphur dioxide (SO2) control efficiency for boilers and heaters
Control technique Control efficiency % (residual and distillate oil) Reference
Spray drying Range: 70 – 90
Median: 80
AP-42, Table1.3-13
Furnace injection or duct injection Range: 25 – 50
Median: 38
AP-42, Table1.3-13
Wet scrubber (dual alkali) Range: 90 – 96
Median: 93
AP-42, Table1.3-13
Wet scrubber lime/limestone; sodium carbonate; magnesium oxide/hydroxide Range: 80 – 98
Median: 89
AP-42, Table1.3-13

 

Table C.3: Carbon monoxide (CO) control efficiency for boilers and heaters
Control technique Control efficiency% - 
Residual oil
Control efficiency % -
Distillate oil
Reference
Fuel alteration - water emulsion 33 No data AP-42, Table1.3-15

 

Table C.4: PM control efficiency for residual oil-fired boilers and heaters
Control technique Control efficiency % for boiler type -Industrial Control efficiency % for boiler type -
Commercial
Control efficiency % for boiler type -
Utility
Reference
Scrubber ND ND 94 AP-42, Table1.3-4, note “e”
Electrostatic precipitator (ESP) ND ND 99.2 AP-42, Table1.3-4, note “d”
Multiple cyclone 80 ND ND AP-42, Table1.3-5, note “d”
Fuel alteration - water emulsion 45 45 45 AP-42, Table1.3-15

 

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