September 8, 2008 

TECHNICAL SUPPORT DOCUMENT FOR THE 

PETROLEUM REFINING SECTOR: PROPOSED 

RULE FOR MANDATORY REPORTING OF 

GREENHOUSE GASES 

Office of Air and Radiation 

U.S. Environmental Protection Agency 

September 8, 2008
2

CONTENTS 

1. Industry Description...............................................................................................................3 

2. Total Emissions....................................................................................................................11 

3. Emission Sources.................................................................................................................12 

3.1 Stationary Combustion Sources..................................................................................12 

3.2 Flares .........................................................................................................................13 

3.3 Catalytic Cracking Units.............................................................................................14 

3.4 Catalytic Reforming Units..........................................................................................14 

3.5 Fluid Coking Units.....................................................................................................15 

3.6 Sulfur Recovery Vents................................................................................................15 

3.7 Hydrogen Plants.........................................................................................................15 

3.8 Fugitive Emission Sources..........................................................................................15 

4. Review of Existing Programs and Methodologies ................................................................16 

5. Types of Information to be Reported....................................................................................16 

5.1 Types of Emissions to be Reported.............................................................................16 

5.2 Other Information to be Reported ...............................................................................18 

6. Options for Reporting Threshold..........................................................................................19 

7. Options for Monitoring Methods..........................................................................................19 

7.1 Stationary Combustion Sources..................................................................................19 

7.2 Flares .........................................................................................................................20 

7.3 Process Emissions ......................................................................................................20 

7.4 Fugitive Emission Sources..........................................................................................21 

8. Options for Estimating Missing Data....................................................................................22 

9. QA/QC Requirements..........................................................................................................22 

10. References .........................................................................................................................23 

Appendix A. Derivation of Calculation Methods......................................................................25 

A.1 Equipment Leaks.......................................................................................................25 

A.2 Storage Tanks............................................................................................................29 

A.3 Delayed Coking Unit Coke Cutting ...........................................................................31 
3

1. Industry Description 

Petroleum refineries are facilities that are engaged in producing liquefied petroleum gases 

(LPG), motor gasoline, jet fuels, kerosene, distillate fuel oils, residual fuel oils, lubricants, 

asphalt (bitumen), and other products through distillation of crude oil or through redistillation, 

cracking, or reforming of unfinished petroleum derivatives. There are three basic types of 

refineries: topping, hydroskimming, and upgrading (also referred to as “conversion” or 

“complex”). Topping refineries have a crude distillation column and produce naphtha and other 

intermediate products, but not gasoline. There are only a few topping refineries in the U.S., 

predominately in Alaska. Hydroskimming refineries have mild conversion units such as 

hydrotreating units and/or reforming units to produce finished gasoline products, but they do not 

upgrade heavier components of the crude oil that exit near the bottom of the crude distillation 

column. Some topping/hydroskimming refineries specialize in processing heavy crude oils to 

produce asphalt. There are 8 operating asphalt plants and approximately 20 other 

hydroskimming refineries operating in the U.S. as of January 2006 (EIA, 2006a). The vast 

majority (approximately 75 to 80 percent) of U.S. refineries are upgrading/conversion refineries. 

Upgrading/conversion refineries have cracking or coking operations to convert long-chain, high 

molecular weight hydrocarbons (“heavy distillates”) into smaller hydrocarbons that can be used 

to produce gasoline product (“light distillates”) and other higher value products and 

petrochemical feedstocks. The U.S., Western Europe, and Asia are the largest and most 

sophisticated producers of refined petroleum products. The U.S. produced 23 percent of the 

world’s refinery products in 2003 (U.S. DOE, 2007). 

There are 150 petroleum refineries in 35 States and 2 U.S. territories, eight of which are 

considered asphalt refineries. The majority of oil distillation capacity in the U.S. is at large, 

integrated companies with multiple refining facilities. About 30 percent of all facilities are small 

operations producing fewer than 50,000 barrels per day, representing about 5 percent of the total 

output of petroleum products annually. As of January 2006, the combined operating crude 

capacity for the 150 U.S. refineries (including those in U.S. territories) was 17.9-million barrels 

per calendar day (bbls/cd). The combined operating crude capacity for the 148 refineries within 

the U.S. States is just over 17.3-million bbls/cd; the 2 refineries located in U.S. territories had a 

combined capacity of 572,900 bbls/cd (EIA, 2006b). The average crude capacity utilization rate 

for U.S refineries was 90.6 percent in 2005. In 2005, the U.S. refineries (not including U.S. 

territories) produced 2,225 million barrels (MMbbl) of motor gasoline, 1,443 MMbbl of diesel 

fuel oil, 564 MMbbl of jet fuel, 305 MMbbl of petroleum coke, 229 MMbl of residual fuel oil, 

and 209 MMbbl of LPG, as well as other products (EIA, 2006a). Table 1 includes a list of the 

150 refineries within the U.S. and its territories along with crude oil distillation capacities and 

process charge or production capacities for various process units as of January 2006. 

Petroleum refining is a very energy-intensive industry. In 2002, it accounted for about 7 percent 

of the total U.S. energy consumption, making it the nation’s second-highest industrial consumer 

(U.S. DOE, 2007). 
4

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

BP Prudhoe Bay AK 12,500 0 0 0 0 0 0

ConocoPhillips Alaska Kuparuk AK 14,000 0 0 0 0 0 0

Flint Hills Resources North Pole AK 210,000 0 0 0 0 0 0

Petro Star Inc. North Pole AK 17,000 0 0 0 0 0 0

Petro Star Inc. Valdez AK 48,000 0 0 0 0 0 0

Tesoro Petroleum Corp. Kenai AK 72,000 0 13,000 0 0 13 20

Goodway Refining LLC Atmore AL 4,100 0 0 0 0 0 0

Gulf Atlantic Operations LLC Mobile Bay AL 16,700 0 0 0 0 0 0

Hunt Refining Co. Tuscaloosa AL 34,500 0 7,200 0 14,000 6 80

Shell Chemical LP Saraland AL 80,000 0 20,000 0 0 0 35

Cross Oil & Refining Co. Inc. Smackover AR 7,200 0 0 0 0 3 0

Lion Oil Co. El Dorado AR 70,000 19,900 14,800 0 0 0 157

Big West of CA Bakersfield CA 66,000 0 16,300 0 22,000 25 105

BP Carson CA 260,000 102,500 52,000 0 65,000 105 350

Chevron USA Inc. El Segundo CA 260,000 74,000 49,000 0 66,000 77 600

Chevron USA Inc. Richmond CA 242,901 90,000 71,300 0 0 181 789

ConocoPhillips 

LA - Carson/ 

Wilmington 

CA 139,000 50,280 36,750 0 52,200 105 370

ConocoPhillips SF - Rodeo CA 76,000 0 32,000 0 27,000 84 310

ConocoPhillips 

Arroyo Grande 

(Santa Maria) CA 44,200 0 0 0 23,400 0 120

Edgington Oil Co. Long Beach CA 26,000 0 0 0 0 0 0

ExxonMobil Corp. Torrance CA 149,500 100,000 20,000 0 54,600 138 400

Greka Energy Santa Maria CA 9,500 0 0 0 0 0 0
5

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

Kern Oil & Refining Co. Bakersfield CA 26,000 0 3,300 0 0 0 5

Lunday-Thagard Co. (aka World 

Oil Co.) South Gate CA 8,500 0 0 0 0 0 0

Paramount Petroleum Corp. Paramount CA 50,000 0 8,500 0 0 0 40

San Joaquin Refining Co., Inc. Bakersfield CA 15,000 0 0 0 0 4 3

Shell Oil Products US Martinez CA 155,600 73,000 31,000 22,500 27,500 107 364

Shell Oil Products US Wilmington CA 98,500 36,000 34,000 0 40,000 15 280

Ten By Inc. Oxnard CA 2,800 0 0 0 0 0 0

Tesoro Golden Eagle CA 166,000 71,000 42,000 48,000 0 82 200

Valero Energy (Ultramar, Inc.) Wilmington CA 80,887 52,000 17,000 0 29,000 0 230

Valero Energy Corp. Benicia CA 144,000 75,300 37,200 29,500 0 141 303

Valero Energy Corp. Wilmington CA 6,200 0 0 0 0 0 0

Suncor Energy Commerce City CO 62,000 20,000 10,500 0 0 0 106

Suncor Energy Denver CO 32,000 10,000 10,000 0 0 0 2

Valero Energy Corp. Delaware City DE 181,500 87,000 43,800 53,000 0 40 596

Citgo Petroleum Savannah GA 28,000 0 0 0 0 0 0

Chevron USA Inc. 

Honolulu 

(Barber's Point) HI 54,000 22,000 0 0 0 3 0

Tesoro Hawaii Petrol. Kapolei HI 93,500 0 13,000 0 0 18 34

ConocoPhillips Wood River IL 306,000 101,000 96,500 0 18,000 57 504

ExxonMobil Corp. Joliet IL 238,500 98,000 52,200 0 59,100 0 660

Marathon Petroleum Co. LLC Robinson IL 192,000 49,000 74,500 0 29,400 0 202

PDV Midwest Refining Lemont IL 167,000 70,000 31,200 0 44,000 12 400

BP Whiting IN 410,000 169,000 90,000 0 36,000 31 550
6

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

Countrymark Cooperative, Inc. Mt. Vernon IN 23,000 8,400 6,500 0 0 0 9

Coffeyville Refining Coffeyville KS 112,000 32,500 17,000 0 19,500 0 146

Frontier Oil Corp. El Dorado KS 106,000 39,000 30,000 0 19,000 6 230

National Cooperative Refinery 

Association 

McPherson KS 81,200 24,500 23,500 0 22,000 0 81

Marathon Petroleum Co. LLC Catlettsburg KY 222,000 99,000 50,000 0 0 0 448

Somerset Refinery Inc. Somerset KY 5,500 0 1,000 0 0 0 0

Calcasieu Refining Co. Lake Charles LA 30,000 0 0 0 0 0 0

Calumet Lubricants Co. Shreveport LA 42,000 10,500 8,000 0 0 6 10

Calumet Lubricants Co. Cotton Valley LA 13,020 0 0 0 0 2 0

Calumet Lubricants Co. Princeton LA 8,300 0 0 0 0 5 3

Citgo Petroleum Corp. Lake Charles LA 429,500 150,000 110,800 0 104,000 0 640

ConocoPhillips Westlake LA 239,400 50,000 44,000 0 64,000 0 860

ConocoPhillips Belle Chasse LA 247,000 104,000 44,600 0 27,000 0 125

ExxonMobil Corp. Baton Rouge LA 501,000 241,000 78,000 0 118,500 0 800

ExxonMobil Corp.- Chalmette Chalmette LA 188,160 71,600 49,400 0 35,000 0 935

Marathon Petroleum Co. LLC Garyville LA 245,000 131,000 48,500 0 37,400 0 790

Motiva Enterprises Norco LA 226,500 114,000 62,000 0 23,600 60 169

Motiva Enterprises Convent LA 235,000 92,000 40,000 0 0 63 728

Murphy Oil USA Inc. Meraux LA 120,000 37,000 32,000 0 0 0 31

Pelican Refining Co. LLC Lake Charles LA 0 0 0 0 0 0 0

Placid Refining Inc. Port Allen LA 56,000 20,500 11,000 0 0 0 28

Shell Chemical Co. St. Rose LA 55,000 0 0 0 0 0 0

Valero Energy Corp. Krotz Springs LA 80,000 34,000 13,000 0 0 0 0
7

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

Valero Energy Corp. Norco LA 185,003 105,380 25,000 0 70,400 0 393

Marathon Petroleum Co. LLC Detroit MI 100,000 30,000 20,000 0 0 0 147

Flint Hills Resources Rosemount MN 279,300 86,500 51,300 0 70,800 115 999

Marathon Petroleum Co. LLC St. Paul Park MN 70,000 26,000 20,500 0 0 9 112

Chevron USA Inc. Pascagoula MS 330,000 67,000 96,000 0 105,000 230 1,300

Ergon Refining Inc. Vicksburg MS 23,000 0 0 0 0 8 0

Hunt Southland Refining Sandersville MS 11,000 0 0 0 0 0 0

Cenex Harvest States Laurel MT 55,000 13,500 12,000 0 0 30 130

ConocoPhillips Billings MT 58,000 21,490 13,550 0 19,950 20 246

ExxonMobil Corp. Billings MT 60,000 23,500 12,500 10,400 24 0

Montana Refining Co. Great Falls MT 8,200 2,500 1,030 0 0 2 0

Tesoro Mandan ND 58,000 30,600 12,100 0 0 0 17

Chevron USA Perth Amboy NJ 80,000 0 0 0 0 0 0

Citgo Asphalt Refining Co. Paulsboro NJ 32,000 0 0 0 0 0 0

ConocoPhillips Linden NJ 238,000 145,000 32,000 0 0 10 180

Hess Corporation Port Reading NJ 0 65,000 0 0 0 0 10

Sunoco, Inc. Westville NJ 145,000 57,000 30,000 0 0 0 80

Valero Energy Corp. Paulsboro NJ 160,000 55,000 30,000 0 27,000 9 206

Giant Refining Co. Bloomfield NM 16,800 6,500 4,000 0 0 0 3

Giant Refining Co. Gallup NM 20,800 11,500 6,800 0 0 0 2

Navajo Refining Co. 

Artesia + 

Lovington 

NM 75,000 27,000 18,000 0 0 0 130

Foreland Refining Co. 

Tonopah/ Eagle 

Springs 

NV 2,000 0 0 0 0 0 0
8

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

BP PLC Toledo OH 131,000 55,000 43,000 0 34,000 33 340

Marathon Petroleum Co. LLC Canton OH 73,000 25,000 19,000 0 0 0 110

Sunoco, Inc. Toledo OH 160,000 79,000 48,000 0 0 45 62

Valero Energy Corp. Lima OH 146,900 40,000 55,000 0 23,000 58 110

ConocoPhillips Ponca City OK 194,000 69,802 54,190 0 27,660 35 34

Sinclair Oil Corp. Tulsa OK 70,300 27,750 16,800 0 0 0 28

Sunoco, Inc. Tulsa OK 85,000 0 24,000 0 11,000 0 0

Valero Energy Corp. Ardmore OK 83,640 30,000 21,350 0 0 26 243

Wynnewood Refining Co. Wynnewood OK 54,000 21,000 15,000 0 0 0 36

Chevron USA Portland OR 0 0 0 0 0 0 0

American Refining Group Bradford PA 10,000 0 1800 0 0 0 0

ConocoPhillips 

Trainer 

(Marcus Hook) PA 185,000 53,000 50,000 0 0 0 41

Sunoco, Inc. Marcus Hook PA 175,000 105,000 20,000 0 0 0 33

Sunoco, Inc. (combined Sun & 

Chevron) 

Phil. (Girard Pt 

& Pt Breeze) PA 335,000 123,500 86,000 0 0 0 260

United Refining Co. Warren PA 65,000 26,000 14,000 0 0 0 70

Valero Energy Corp. Memphis TN 180,000 70,000 36,000 0 0 0 116

AGE Refining & Manufacturing San Antonio TX 12,200 0 0 0 0 0 0

Alon USA Energy Inc. Big Spring TX 67,000 25,000 21,000 0 0 0 150

BP Texas City TX 437,000 189,300 138,000 0 43,000 0 1,400

Citgo Corpus Christi TX 156,000 81,800 52,500 0 43,500 0 357

ConocoPhillips Borger TX 146,000 72,300 26,900 0 0 91 340

ConocoPhillips Sweeny TX 247,000 119,000 37,500 0 74,100 155 595
9

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

Delek Refining Ltd Tyler TX 58,000 20,250 17,500 0 6,000 0 15

ExxonMobil Corp. Beaumont TX 348,500 117,700 155,000 0 50,700 55 636

ExxonMobil Corp. Baytown TX 562,500 221,000 126,000 42,000 46,500 0 1,796

Flint Hills Resources Corpus Christi TX 288,126 106,700 71,600 0 14,000 0 237

Lyondell-Citgo Refining Co. Houston TX 270,200 100,000 37,000 0 105,000 0 803

Marathon Petroleum Co. LLC Texas City TX 72,000 55,000 11,000 0 0 0 0

Motiva Enterprises Port Arthur TX 285,000 90,000 48,000 0 57,500 0 711

Pasadena Refining Systems Inc. Pasadena TX 100,000 56,000 23,000 0 12,500 0 28

Shell Oil Products US - Deer Park 

Refining Limited Partnership 

Deer Park TX 333,700 75,000 72,000 0 88,000 108 1,150

South Hampton Resources Inc. Silsbee TX 0 0 1,500 0 0 2 0

Total SA Port Arthur TX 232,000 75,000 39,600 0 0 0 300

Trigeant Ltd. Corpus Christi TX 0 0 0 0 0 0 0

Valero Energy Corp. Corpus Christi TX 142,000 114,500 69,000 0 18,500 195 1,288

Valero Energy Corp. Houston TX 83,000 65,000 11,500 0 0 0 110

Valero Energy Corp. Texas City TX 213,750 83,000 16,500 0 50,000 0 924

Valero Energy Corp. Three Rivers TX 90,000 24,000 33,000 0 0 12 62

Valero Energy Corp. Sunray TX 158,327 54,465 47,400 0 0 0 60

Valero Energy Corp. Port Arthur TX 260,000 78,600 53,800 0 103,000 0 1,197

Western Refining El Paso TX 116,000 34,000 25,000 0 0 0 40

Big West Oil Co. Salt Lake City UT 29,400 11,000 7,300 0 0 0 4

Chevron USA Salt Lake City UT 45,000 14,000 8,000 0 8,500 0 21

Holly Corp. Woods Cross UT 24,700 8,900 7,700 0 0 0 10
10

Table 1. Petroleum Refineries in the United States.a

Charge capacity (bbl/sd) Production capacity 

Facility Name City State 

Crude 

Capacity 

(bbl/cd) FCCU CRU 

Fluid 

Coking 

Delayed 

Coking 

Hydrogen 

(MMcfd) 

Sulfur 

(short 

tons/d) 

Silver Eagle Refining Inc. Woods Cross UT 10,250 0 2,200 0 0 1 0

Tesoro Salt Lake City UT 58,000 25,200 12,600 0 0 0 18

Giant Refining Yorktown VA 58,600 30,200 12,100 0 19,000 0 39

BP Ferndale WA 225,000 0 63,000 0 64,000 128 242

ConocoPhillips Ferndale WA 96,000 33,500 17,400 0 0 0 55

Shell Oil Products US Anacortes WA 145,000 57,900 32,700 0 25,700 0 350

Tesoro Anacortes WA 120,000 48,000 26,000 0 0 0 0

US Oil & Refining Co. Tacoma WA 37,850 0 6,500 0 0 0 10

Murphy Oil USA Inc. Superior WI 34,300 11,000 8,000 0 0 0 34

Ergon-West Virginia Inc. Newell (Congo) WV 20,000 0 3,400 0 0 1 1

Frontier Oil & Refining Co. Cheyenne WY 47,000 12,000 9,200 0 10,000 6 101

Little America Refining Co. 

Evansville 

(Casper) WY 24,500 11,000 6,000 0 0 0 0

Silver Eagle Refining Inc. Evanston WY 3,000 0 2,150 0 0 0 0

Sinclair Oil Corp. Sinclair WY 66,000 21,806 12,500 0 0 26 47

Wyoming Refining Co. Newcastle WY 12,500 5,500 2,750 0 0 0 4

Total in US States 17,333,014 6,275,123 3,859,070 205,400 2,305,510 2,823 32,421

Shell Chemical Yabucoa Inc. Yabucoa P.Rico 77,900 0 20,000 0 0 0 22

Hovensa LLC Kingshill 

(St. Croix) V.Isl 495,000 150,000 115,000 0 61,000 0 550

Grand Total 17,905,914 6,425,123 3,994,070 205,400 2,366,510 2,823 32,993

a EIA, 2006. Tables 3 and 4. Abbreviation for capacity units are: bbl/cd = barrel per calendar day = maximum capacity considering scheduled maintenance over 

365 calendar days; bbl/cd = barrel per stream day = maximum capacity for a single, operating day; MMcfd = million cubic feet per day. 
11

2. Total Emissions 

The petroleum refining industry is the nation’s second-highest industrial consumer of energy. 

Nearly all of the energy consumed is fossil fuel for combustion; therefore, the petroleum refining 

industry is a significant source of greenhouse gas (GHG) emissions. In addition to the 

combustion-related sources (e.g., process heaters and boilers), there are certain processes, such 

as fluid catalytic cracking units (FCCU), hydrogen production units, and sulfur recovery plants, 

that have significant process emissions of carbon dioxide (CO2). Methane (CH4) emissions from 

a typical petroleum refinery arise from process equipment leaks, crude oil storage tanks, asphalt 

blowing, and delayed coking units. System blow down and flaring of waste gas also contributes 

to the overall CO2 and CH4 emissions at the refinery. Additional detail on process-specific 

sources of GHG emissions is provided in Section 3. 

Because much of the GHG emissions from petroleum refineries are characterized as fossil fuel 

combustion in the overall energy sector of the Inventory of U.S. Greenhouse Gas Emissions and 

Sinks, it is difficult to obtain a clear GHG emission estimate for petroleum refineries from the 

U.S. Inventory (EPA, 2008). Therefore, a separate industry profile was used to estimate the total 

GHG emissions from petroleum refineries (Coburn, 2007). This profile included estimates of 

CO2, CH4, and nitrous oxide (N2O) from combustion sources (including coke combustion in 

FCCU), flares, and fugitive emission sources (equipment leaks, storage tanks, and wastewater 

treatment). The profile was updated to include GHG emissions from hydrogen production units, 

sulfur recovery units, asphalt blowing operations, and blowdown systems using the following 

emission factors: 

¡ Hydrogen production: 6.05 metric tons CO2/million cubic feet hydrogen produced 

¡ Sulfur production: 0.366 metric tons CO2/short ton sulfur produced 

¡ Asphalt blowing: 2,555 standard cubic feet CH4/thousand barrels asphalt blown 

¡ Blow down systems: 137 standard cubic feet CH4/thousand barrels crude throughput 

The hydrogen production emission factor was based on the mass of CO2 produced being 2.5 

times the mass on hydrogen produced as reported in the “Hydrogen Fact Sheet” (see: 

http://www.getenergysmart.org/Files/HydrogenEducation/6HydrogenProductionSteamMethaneR

eforming.pdf). The sulfur production emission factor was based on engineering estimate after 

evaluating tail gas flow rates for sulfur recovery plants reported in EPA, 1998. The asphalt and 

blow down system emission factors were taken from the U.S. Inventory (EPA, 2008). Based on 

the updated industry profile, U.S. petroleum refineries have onsite GHG emissions of 204.75 

million metric tons (mmt) of CO2 equivalents (CO2e). When accounting for electricity and 

steam purchases, petroleum refineries are also responsible for indirect GHG emissions of 26.0 

mmt CO2e. 

Figure 1 presents the breakdown of onsite GHG emissions by source. As seen in Figure 1, 

combustion sources, direct process emissions, and flaring account for 99 percent of the onsite 

GHG emissions (on a CO2e basis). 
12

Other

0.8%

Combustion

67.7%

Flaring

1.6%

H2 Plant

2.7%

Sulfur Plant

1.9%

Wastewater 

Treatment

0.43%

Storage Tanks

0.007%

Equipment Leaks

0.014%

Delayed Coking

0.058%

Cat Coke

25.2%

Asphalt Blowing

0.10%

Blowdown

0.18%

Cooling Towers

0.003%

Figure 1. Relative importance of refinery GHG emission sources evaluated on CO2e basis. 

3. Emission Sources 

This section includes brief descriptions of the sources and process units that generate significant 

greenhouse gases at a refinery. More complete descriptions of the entire refining process are 

available in other locations (U.S. EPA, 1995; U.S. EPA, 1998; U.S. DOE, 2007). 

3.1 Stationary Combustion Sources 

As seen in Figure 1, the combustion of fuels in stationary combustion sources is a significant 

source of GHG emissions at petroleum refineries. Combustion sources include process heaters, 

boilers, combustion turbines, and similar devices. Nearly all refinery process units use process 

heaters. In addition to direct process heat, many refinery processes also have steam and 

electricity requirements. Some refineries purchase steam to meet their process’s steam 

requirements; others use dedicated on-site boilers to meet their steam needs. Similarly, some 

refineries purchase electricity from the grid to run their pumps and other electrical equipment; 

other refineries have co-generation facilities to meet their electricity needs and may produce 

excess electricity to sell to the grid. Refineries that produce their own steam or electricity will 

have higher on-site fuel usage, all other factors being equal, than refineries that purchase these 
13

utilities. Combustion sources primarily emit CO2, but they also emit small amounts of CH4 and 

N2O. 

The predominant fuel used at petroleum refineries is refinery fuel gas (RFG), which is also 

known as still gas. RFG is a mixture of light C1 to C4 hydrocarbons, hydrogen, hydrogen 

sulfide (H2S), and other gases that exit the top (overhead) of the distillation column and remain 

uncondensed as they pass through the overhead condenser. RFG produced at different locations 

within the refinery is typically compressed, treated to remove H2S (if necessary), and routed to a 

common, centralized location (i.e., mix drum) to supply fuel to the various process heaters at the 

refinery. This RFG collection and distribution system is referred to as the fuel gas system. 

The fuel gas generated at the refinery is typically augmented with natural gas to supply the full 

energy needs of the refinery. Depending on the types of crude oil processed and the process 

units in operation, the amount of supplemental natural gas needed can change significantly. 

Topping and hydroskimming refineries that process heavier crude oils generate limited amounts 

of RFG and may use natural gas for 70 percent or more of their energy needs. 

Upgrading/conversion refineries, especially those processing lighter crude oils, may need very 

little supplemental natural gas or may even produce more fuel gas than needed for basic 

operations. Depending on the quantities of propane and butane (C3 and C4 hydrocarbons) 

produced and local market conditions, upgrading/conversion refineries will typically have light 

gas plant to recover propane and butane for sale as products or for use as petrochemical or gas 

blending feedstocks. In these refineries, the hydrocarbon content of the RFG will be dominated 

by C1 or C2 hydrocarbons. Consequently, there may be significant variability in the fuel gas 

composition between different refineries. Within a given refinery, the variability in the refinery 

fuel gas composition should be somewhat less because most refinery process units are 

continuous. However, delayed coking units, which are significant fuel gas producers, are batch 

processes, so refineries with these units may have more variability in RFG composition than 

other refineries. Additionally, certain process units may cycle operations (notably hydrotreating 

units and catalytic reforming units) and other units are occasionally taken off-line for 

maintenance so that occasional variability in fuel gas composition within a refinery is inevitable. 

` 

3.2 Flares 

Flares are commonly used in refineries as safety devices to receive gases during periods of 

process upsets, equipment malfunctions, and unit start-up and shutdowns. “Emergency” flares 

receive only low flows of “sweep” gas to prevent air (oxygen) from entering the flare header and 

possibly the fuel gas system while maintaining the readiness of the flare in the event of a 

significant malfunction or process upset. Some flares may receive excess process gas on a 

frequent or routine basis; these flares act as pressure relief systems for the refinery’s fuel gas 

system and may also be used to combust other low pressure gas streams generated at the 

refinery. Some flares may be used solely as control devices for regulatory purposes. As with 

stationary combustion sources, the combustion of gas in a flare results predominately in 

emissions of CO2 along with small amounts of CH4 and N2O. In the 2002 National Emissions 

Inventory (NEI), emissions were reported for 252 flares at 77 refineries (EPA, 2006). Based on 

these data, each refinery is expected to have 3 flares on average. 
14

3.3 Catalytic Cracking Units 

In the catalytic cracking process, heat and pressure are used with a catalyst to break large 

hydrocarbons into smaller molecules. The fluid catalytic cracking unit (FCCU) is the most 

common type of catalytic cracking unit currently in use. Based on process-specific data 

collected in the development of emission standards for petroleum refineries, there are 

approximately 125 FCCU in the petroleum refining industry. In this type of reactor, the feed is 

pre-heated to between 500 and 800 degrees Fahrenheit (oF) and contacted with fine catalyst 

particles from the regenerator section, which are at about 1,300oF in the feed line (“riser”). The 

feed vapor, which is heavy distillate oil from the crude or vacuum distillation column, reacts 

when contacted with the hot catalyst to break (or crack) the large hydrocarbon compounds into a 

variety of lighter hydrocarbons. During this cracking process, coke is deposited on the catalyst 

particles, which deactivates the catalyst. The catalyst separates from the reacted (“cracked”) 

vapors in the reactor; the vapors continue to a fractionation tower and the catalyst is recycled to 

the regenerator portion of the FCCU to burn-off the coke deposits and prepare the catalyst for 

reuse in the FCCU riser/reactor (U.S. EPA, 1998). 

The FCCU catalyst regenerator generates GHG through the combustion of coke, which is 

essentially solid carbon with small amounts of hydrogen and various impurities that were 

deposited on the catalyst particles during the cracking process. CO2 is the primary GHG emitted; 

small quantities of CH4 and N2O are also emitted during “coke burn-off.” An FCCU catalyst 

regenerator can be designed for complete or partial combustion. A complete-combustion FCCU 

operates with sufficient air to convert most of the carbon to CO2 rather than carbon monoxide 

(CO). A partial-combustion FCCU generates CO as well as CO2, so most partial-combustion 

FCCUs are typically followed by a CO boiler to convert the CO to CO2. Most refineries that 

operate an FCCU recover useful heat generated from the combustion of catalyst coke during 

catalyst regeneration; the heat recovered from catalyst coke combustion offsets some of the 

refinery’s ancillary energy needs. 

Thermal catalytic cracking units (TCCU) are similar to FCCUs except that the catalyst particles 

are much bigger and the system uses a moving bed reactor rather than a fluidized system. The 

generation of GHG, however, is the same. Specifically, GHG are generated in the regenerator 

section of the TCCU when coke deposited on the catalyst particles is burned-off in order to 

restore catalyst activity. 

3.4 Catalytic Reforming Units 

In the catalytic reforming unit (CRU), low-octane heavy hydrocarbons, generally gasoline and 

naptha are reacted with a catalyst to produce aromatic compounds such as benzene. The feed to 

the CRU is usually treated with hydrogen to remove sulfur, nitrogen and metallic contaminants. 

The CRU usually has a series of three to six fixed-bed or moving bed reactors and may be 

operated continuously or as a semi-regenerative unit. As in the FCCU, coke is deposited on 

catalyst particles during the processing reaction, and this “catalyst coke” must be burned-off to 

reactivate the catalyst, generating CO2, along with small amounts of CH4 and N2O. In a 

continuous CRU, the catalyst can be regenerated one reactor at a time, which avoids disrupting 
15

the process. In a semi-regenerative CRU, all the reactors are shut down at one time for catalyst 

regeneration, usually after no more than 2 years of operation (U.S. EPA, 1998). 

3.5 Fluid Coking Units 

Coking is another cracking process, usually used at a refinery to generate transportation fuels, 

such as gasoline and diesel, from lower-value fuel oils. A desired by-product of the coking 

reaction is petroleum coke, which can be used as a fuel for power plants as well as a raw material 

for carbon and graphite products. The fluid coking process is continuous and occurs in a reactor 

rather than a coke drum like the delayed coking process. Fluid coking units produce a higher 

grade of petroleum coke than delayed coking units; however, unlike delayed coking units that 

use large process preheaters, fluid coking units burn 15 to 25 percent of the coke produced to 

provide the heat needed for the coking reactions (U.S. DOE, 2007). Like the FCCU and CRU, 

the combustion of the petroleum coke generates CO2 along with small amounts of CH4 and N2O. 

3.6 Sulfur Recovery Vents 

Hydrogen sulfide is removed from the refinery fuel gas system through the use of amine 

scrubbers. While the selectivity of hydrogen sulfide removal is dependent on the type of amine 

solution used, these scrubbers also tend to extract CO2 from the fuel gas. The concentrated sour 

gas is then processed in a sulfur recovery plant to convert the hydrogen sulfide into elemental 

sulfur or sulfuric acid. CO2 in the sour gas will pass through the sulfur recovery plant and be 

released in the final sulfur plant vent. Additionally, small amounts of hydrocarbons may also be 

present in the sour gas stream. These hydrocarbons will eventually be converted to CO2 in the 

sulfur recovery plant or via tail gas incineration. The most common type of sulfur recovery plant 

is the Claus unit, which produces elemental sulfur. The first step in a Claus unit is a burner to 

convert one-third of the sour gas into sulfur dioxide prior to the Claus catalytic reactors. GHG 

emissions from the fuel fired to the Claus burner are expected to be accounted for as a 

combustion source. After that, the sulfur dioxide and unburned hydrogen sulfide are reacted in 

the presence of a bauxite catalyst to produce elemental sulfur. Based on process-specific data 

collected in the development of emission standards for petroleum refineries, there are 195 sulfur 

recovery trains in the petroleum refining industry (U.S. EPA, 1998). 

3.7 Hydrogen Plants 

The most common method of producing hydrogen at a refinery is the steam methane reforming 

(SMR) process. Methane, other light hydrocarbons, and steam are reacted via a nickel catalyst to 

produce hydrogen and CO. Excess CH4 is added and combusted to provide the heat needed for 

this endothermic reaction. The CO generated by the initial reaction further reacts with the steam 

to generate hydrogen and CO2 (U.S. DOE, 2007). According to EIA’s Refinery Capacity Report 

2006 (EIA, 2006), 54 of the 150 petroleum refineries have hydrogen production capacity. 

3.8 Fugitive Emission Sources 

Fugitive CH4 emission sources are projected to only contribute 0.8 percent of a typical refinery’s 

total GHG emissions. The largest four fugitive emission sources are projected to be blow down 

systems, delayed coking unit depressurization and coke cutting, asphalt blowing, and wastewater 

treatment (including sludge digestion). Methane emissions from process equipment leaks are 

expected to be small compared to other GHG emission sources at a typical refinery. Unless the 
16

refinery receives unstabilized crude, CH4 emissions from crude oil loading and storage are 

expected to be negligible, as are CH4 emissions from cooling towers. These processes are 

described in further detail in Appendix A. 

4. Review of Existing Programs and Methodologies 

In developing GHG monitoring and reporting options for petroleum refineries, a number 

of existing programs and guideline methodologies were reviewed. Specifically, the following 

resources were examined: 

1. 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National 

Greenhouse Gas Inventories. Volume 2, Chapters 2 and 4. 

2. European Union (EU) Emissions Trading Scheme (2007). 2007/589/EC: Commission 

Decision of 18 July 2007 Establishing Guidelines for the Monitoring and Reporting of 

Greenhouse Gas EmissionsPpursuant to Directive 2003/87/EC of the European 

Parliament and of the Council. Available at: 

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32007D0589:EN:NOT. 

 

3. U.S. Department of Energy (DOE). 2007. Technical Guidelines: Voluntary Reporting Of 

Greenhouse Gases (1605(B)) Program. 

4. API (American Petroleum Institute). 2004. Compendium of Greenhouse Gas Emissions 

Methodologies for the Oil and Gas Industry. February. 

5. CARB (California Air Resource Board). 2008. Regulation For The Mandatory 

Reporting of Greenhouse Gas Emissions: Second 15-Day Modified Regulatory 

Language For Public Comment. May 15. 

6. Environment Canada (2006). Technical Guidance Manual on Reporting Greenhouse Gas 

Emissions. http://www.ghgreporting.gc.ca/GHGInfo/Pages/page15.aspx?lang=E. 

Each of these sources was reviewed to determine the types of emissions to be reported, the 

facility reporting thresholds, and the monitoring methodologies recommended. The reporting 

and monitoring options presented in Sections 5, 6, and 7 are commensurate with the 

methodologies used in these existing programs and guidelines. 

5. Types of Information to be Reported 

5.1 Types of Emissions to be Reported 

Based on the existing programs and the emission sources at petroleum refineries, GHG reporting 

for refineries are limited to CO2, CH4, and N2O. Table 2 summarizes the refinery emission 

sources expected to have appreciable GHG emissions and the GHG expected to be emitted for 

each refinery emission source. 
17

Figure 2 presents the breakdown of onsite GHG emissions by pollutant. Figure 2 indicates that 

CH4 and N2O emissions from petroleum refineries account for less than 1 percent of the total 

GHG emissions (evaluated on a CO2e basis). 

Table 2. Summary of Refinery GHG Emission Sources Considered for Reporting 

Emission Source GHG Emitted 

Stationary combustion sources CO2, CH4, and N2O 

Coke burn-off emissions from catalytic cracking units, fluid 

coking units, catalytic reforming units, and coke calcining units CO2, CH4, and N2O 

Flares CO2, CH4, and N2O 

Hydrogen plant vent CO2 and CH4

Sulfur recovery plant CO2

On-site wastewater treatment system CO2 and CH4

On-site land disposal unit CH4

Asphalt blowing CO2 or CH4

Uncontrolled blowdown systems CH4

Process vents not otherwise specified CO2, CH4, and N2O 

Delayed coking units CH4

Process equipment leaks CH4

Storage tanks CH4

Loading operations CH4
18

CO2

99.04%

N2O

0.09%

CH4

0.87%

Figure 2. Relative importance of CO2, CH4, and N2O in the total nationwide refinery GHG 

emissions inventory (evaluated on a CO2e basis). 

5.2 Other Information to be Reported 

In order to check the reported GHG emissions for reasonableness and for other data quality 

considerations, additional information about the emission sources is needed. Although the exact 

information required is somewhat source dependent, the following is a general list of additional 

information that must be reported. 

(1) The unit identification number (if applicable); 

(2) A description of the type of unit (RFG-fired process heater, flare, FCCU, TCCU, sulfur 

recovery plant, etc.); 

(3) Maximum rated throughput of the unit (MMBtu/hr; bbl/stream day, tons sulfur 

produced/stream day, etc.); 

(4) The calculated CO2, CH4, and N2O emissions for each unit (as applicable), expressed in both 

metric tons of pollutant emitted and metric tons of CO2e; and 

(5) A description of the method used to measure and/or calculate the GHG emissions for each 

unit. 
19

6. Options for Reporting Threshold 

Several options were evaluated as potential reporting thresholds. These options include: 

Option 1. All refineries with facility-wide GHG emissions exceeding 1,000 metric tons of 

CO2e (mtCO2e) must report. 

Option 2. All refineries with facility-wide GHG emissions exceeding 10,000 mtCO2e must 

report. 

Option 3. All refineries with facility-wide GHG emissions exceeding 25,000 mtCO2e must 

report. 

Option 4. All refineries with facility-wide GHG emissions exceeding 100,000 mtCO2e must 

report. 

Table 3 presents the number of refineries and the GHG emissions included for each threshold 

option. The analysis presented in Table 3 only considers the direct (on-site) GHG emissions at 

the refineries. Essentially all refineries are expected to have direct emissions exceeding a 

10,000 mtCO2e threshold. If indirect GHG emissions are included, all U.S. petroleum refineries 

are expected to exceed a 25,000 mtCO2e emission threshold. 

Table 3. Evaluation of Alternative Threshold Options (considering direct emissions only) 

Emissions Covered Facilities Covered 

Option/Threshold Level mmt CO2e/year Percent Number Percent 

Option 1: >1,000 mtCO2e 204.75 100 150 100 

Option 2: >10,000 mtCO2e 204.74 99.995 149 99.3 

Option 3: >25,000 mtCO2e 204.69 99.97 146 97.3 

Option 4: >100,000 mtCO2e 203.75 99.51 128 85.3 

7. Options for Monitoring Methods 

7.1 Stationary Combustion Sources 

There are four basic monitoring options for combustion units. Option 1 is to use annual fuel 

consumption (based on company records), default higher heating value (HHV) for the fuel, and a 

fuel-specific emission factor. Because of the variability in refinery fuel gas composition, this 

method has high uncertainty when applied to a specific refinery. The carbon content or HHV of 

other fuel products used at a refinery, such as diesel fuel or directly purchased and used natural 

gas, will have much less variability both within the refinery and across different refineries than 

refinery fuel gas. As such, Option 1 can yield reasonably accurate CO2 emission estimates for 

these non-RFG fuel types. However, these are expected to be only a small portion of a refinery’s 

total fuel combustion. Option 2 is similar to Option 1, but the HHV is measured periodically 

(daily or weekly measurement frequencies were evaluated) and fuel consumption quantities 

(based on company records) are estimated over the same intervals as the HHV measurements. 

This option should reduce the uncertainty associated with Option 1 since a higher sampling 

frequency yields lower uncertainties. However, since hydrogen combustion does not produce 
20

CO2, it is important to note that a measure of HHV does not necessarily improve the estimation 

of CO2 emissions since some of the heat content of RFG is from hydrogen and only carbon 

content measurements can accurately estimate carbon dioxide emissions for fuel gas streams 

with significant hydrogen content. Option 3 uses direct volumetric flow measurements and 

routine carbon content measurements (daily or weekly) to estimate CO2 emissions. Like Option 

2, this option will have less uncertainty than Option 1 since a higher sampling frequency yields 

lower uncertainties. Option 3 is preferred to Option 2 in that some of the heat content of refinery 

fuel gas is from hydrogen (again, only carbon content measurements can accurately estimate CO2

emissions for fuel gas streams with significant hydrogen content). Therefore, routine 

measurement of the carbon content provides a better correlation to the resulting CO2 emissions 

than HHV. Also, in Option 3 direct fuel flow measurements are made using calibrated flow 

meters, whereas Option 2 allows less rigorous estimates of fuel consumption. As a variant to 

Option 3, the use of a continuous carbon content monitor was also evaluated. Option 4 uses a 

continuous emission monitoring system (CEMS) for CO2 and exhaust flow rate. These options 

(or Tiers) are described in more detail in the Stationary Combustion TSD (EPA-HQ-OAR-2008-

0508-004). 

7.2 Flares 

Three general options were considered for flares, which follow Options 1 through 3 for 

stationary combustion sources; as flares do not have enclosed exhaust stacks, an exhaust CEMS 

(Option 4) is not technically feasible for flares. Stationary combustion source Options 1 and 2 

can provide reasonable estimates of the “sweep” gas or routine flare gas GHG emissions but 

cannot be used to provide accurate estimates of the GHG emissions released during periods of 

start-up, shutdown, or malfunction (SSM) because the flow rate and composition of the gases 

released to the flare during SSM events can vary so widely. As such, Options 1 and 2 for flares 

require separate engineering calculation of the GHG emissions from flares that occur during 

SSM events. Due to the variability in flow rates and potential gas composition for flares, Option 

3, especially the variant of Option 3 that requires both continuous flow and continuous 

composition monitoring, provides significantly more accurate emission estimates than Options 1 

or 2; however, this variability places additional requirements on the types of monitors that can be 

used for Option 3. Dual range monitors will generally be required to monitor the low flow rates 

associated with maintaining the readiness of the flare and the high flow rates that can occur 

during periods of process upsets, which adds additional costs to the monitoring system. 

7.3 Process Emissions 

Four processes are considered in this section; a fifth process, hydrogen production by steam 

reforming, is considered in a separate Hydrogen Production TSD (EPA-HQ-OAR-2008-0508-

016). Three of the processes considered here, the FCCU, the catalytic reforming unit (CRU), 

and the fluid coking unit vents, are all associated with petroleum coke combustion. As described 

previously, the emissions generated from these processes are the result of coke combustion, so 

the monitoring methods are similar to those in the combustion section, but they are tailored by 

process considering the relative quantity of coke burned by each process and the typical 

measurement locations and controls used for each type of process. 
21

Three monitoring options were considered for these process emissions sources. Option 1 is to 

use process feed rates and default coke burn-off factors and coke carbon content to estimate CO2

emissions. This option does not account for differences in coke deposition rates by type of crude 

or severity of the cracking conditions used by a given unit, and therefore is expected to have high 

uncertainties. Option 2 is to monitor coke burn-off rates using gas composition analyzers and to 

estimate flow rate by air blast rates and flow correlations. This option is required for many 

FCCU to comply with Part 60 and Part 63 standards and provides accurate estimates of the CO2

emissions rate from the FCCU regenerator. Due to these regulatory requirements, it is estimated 

that approximately 90 percent of FCCUs already have gas compositional monitors in-place. 

Option 3 is the use of a CEMS for CO2 and exhaust gas flow rate. For partial combustion units, 

this may lead to additional monitoring needs to prevent double counting the GHG process 

emissions from the FCCU and GHG combustion emissions from RFG fired in the CO boiler. 

A fourth process vent source is the sulfur recovery vent. As described previously, some CO2 and 

trace amount of hydrocarbons will enter the sulfur recovery plant in the sour gas. It is expected 

that the total sour gas flow rate is metered at the plant as it is necessary for proper operation of 

the sulfur recovery plant. Option 1 entails periodic sampling of the sour gas for carbon content 

at the inlet to the sulfur recovery plant. Option 2 is the use of a CEMS capable of measuring the 

carbon content and flow rate in the sour gas feed stream at the inlet to the sulfur recovery plant. 

Option 2 would have less uncertainty than Option 1 due to the higher measurement frequency. 

Option 3 is the use of a CEMS for measuring the CO2 and flow rate of the final sulfur recovery 

plant tail gas stack. Option 3 has the advantage of including the CO2 emissions from the firststage Claus burner as well as the tail gas incinerator, if one is used. However, this option could 

result in double counting because fuel used in the Claus burner would also contribute to the CO2

emissions in the final tail gas stack. If a refinery is using “common-pipe” fuel gas consumption 

measurements, it will have no way of knowing how much of the exhaust CO2 is from the 

combustion of fuel gas in the Claus burner. In this case, the refinery would have to measure fuel 

flow and composition directly at the Claus burner in addition to the stack CEMS measurements. 

Given the issues related in properly accounting for the sulfur plant process emissions and 

combustion emissions, Option 3 may not provide any improvement in the overall accuracy of the 

process-related GHG emissions estimate for sulfur recovery plants. 

7.4 Fugitive Emission Sources 

There are a variety of GHG emission sources at the refinery, which include: asphalt blowing, 

delayed coking unit depressurization and coke cutting, coke calcining, blowdown systems, 

process vents, process equipment leaks, storage tanks, loading operations, wastewater treatment, 

and waste disposal. To fully account for the refinery’s GHG emissions, the emissions from these 

sources should be reported; however, the emissions from these sources are expected to be only 

about 1 percent of the refinery’s total GHG emissions. Therefore, Option 1 – use of default 

emission factors – is appropriate for these sources. Where applicable, more stringent options 

(such as using Method 21 monitoring for process equipment leaks, using the TANKS model and 

compositional data for storage tanks, and using the number of delayed coking unit vessel size 

and cycle activity data) were also considered. If a refinery is already monitoring high CH4-

containing process lines, or is already using the TANKS model to estimate methane emissions 

from storage tanks, etc., then these options can be used. For purposes of the current regulatory 
22

activity, additional monitoring of these fugitive CH4 emission sources is not specified given the 

high cost and high uncertainty associated with the fugitive monitoring or estimation methods and 

the small contribution these emissions make to the total GHG emissions from the refinery. 

8. Options for Estimating Missing Data 

A complete record of all measured parameters used in the GHG emissions calculations is 

required (e.g., concentrations, flow rates, fuel heating values, carbon content values, etc.). 

Therefore, whenever a quality-assured value of a required parameter is unavailable (e.g., if a 

CEMS malfunctions during unit operation or if a required fuel sample is not taken), a substitute 

data value for the missing parameter shall be used in the calculations. 

In general, it is recommended that the average of the data measurements before and after the 

missing data period be used to calculate the emissions during the missing data period. If, for a 

particular parameter, no quality-assured data are available prior to the missing data incident, the 

substitute data value should be the first quality-assured value obtained after the missing data 

period. Missing data procedures are applicable for heat content, carbon content, gas and liquid 

fuel flow rates, stack gas or air blast flow rates, and compositional analysis data (CO2, CO, O2, 

CH4, N2O, and H2O content, as applicable). 

9. QA/QC Requirements 

To ensure the quality of the reported GHG emissions, the following quality assurance/quality 

control (QA/QC) activities are considered important: 

(1) Developing and maintaining a Quality Assurance Project Plan (QAPP) that documents the 

measurements made, their accuracy, and explains the quality assurance procedures applied 

for each measurement used to quantify GHG emissions. The QAPP and the appropriate 

records of quality assurance checks should be retained on-site for a minimum of 5 years. 

(2) All fuel flow meters, gas composition monitors, and/or heating value monitors that are used 

to provide data for the GHG emissions calculations should be calibrated prior to the first 

reporting year, using a suitable method published by a consensus standards organization 

(e.g., ASTM, ASME, API, AGA, etc.). Alternatively, calibration procedures specified by 

the flow meter manufacturer may be used. Fuel flow meters, gas composition monitors, 

and/or heating value monitors shall be recalibrated either annually or at the minimum 

frequency specified by the manufacturer. 

(3) Documentation of the procedures used to ensure the accuracy of the estimates of fuel usage, 

gas composition, and/or heating value including, but not limited to, calibration of weighing 

equipment, fuel flow meters, and other measurement devices should maintained. The 

estimated accuracy of measurements made with these devices should also be recorded, and 

the technical basis for the estimates should be provided. 

(4) All CO2 CEMS and flow rate monitors used for direct measurement of GHG emissions 

should comply with QA procedures for daily calibration drift checks and quarterly or annual 
23

accuracy assessments, such as those provided in Appendix F to Part 60 or similar QA 

procedures. 

10. References 

API (American Petroleum Institute). 2004. Compendium of Greenhouse Gas Emissions 

Methodologies for the Oil and Gas Industry. February. 

CARB (California Air Resource Board). 2008. Regulation For The Mandatory Reporting of 

Greenhouse Gas Emissions: Second 15-Day Modified Regulatory Language For Public 

Comment. Available at: http://www.arb.ca.gov/regact/2007/ghg2007/ghgattachment1.pdf. 

May 15. 

Coburn, J., 2007. Greenhouse Gas Industry Profile for the Petroleum Refining Industry. 

Prepared for Lisa Hanle, U.S. Environmental Protection Agency, Washington. June 11. 

EIA (Energy Information Administration). 2006a. Petroleum Supply Annual 2005. Prepared by 

the Energy Information Administration, Washington, DC. October 23. 

EIA (Energy Information Administration). 2006b. Refinery Capacity Report 2006. Prepared by 

the Energy Information Administration, Washington, DC. June 15. 

Environment Canada (2006). Greenhouse Gas Emissions Reporting: Technical Guidance on 

Reporting Greenhouse Gas Emissions. Available at: 

http://www.ghgreporting.gc.ca/GHGInfo/Pages/page15.aspx?lang=E. 

European Union (EU) Emissions Trading Scheme. 2007. 2007/589/EC: Commission Decision 

of 18 July 2007 Establishing Guidelines for the Monitoring and Reporting of Greenhouse 

Gas Emissions Pursuant to Directive 2003/87/EC of the European Parliament and of the 

Council. Available at: http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32007D0589:EN:NOT. July.

IPCC. 2006. 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National 

Greenhouse Gas Inventories. Volume 2, Energy; Chapters 2 and 4. Available at: 

http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html. 

U.S. Department of Energy (DOE). Technical Guidelines: Voluntary Reporting Of Greenhouse 

Gases (1605(B)) Program. January 2007. 

U.S. Department of Energy. 2007. Energy and Environmental Profile of the U.S. Petroleum 

Refining Industry. Prepared by Energetics, Inc., Columbia, MD. November. 

U.S. Environmental Protection Agency. 1995. EPA Office of Compliance Sector Notebook 

Project: Profile of the Petroleum Refining Industry. EPA/310-R-95-013. Washington, 

DC, September. 
24

U.S. Environmental Protection Agency. 1998. Petroleum Refineries—Background Information 

for Proposed Standards, Catalytic Cracking (Fluid and Other) Units, Catalytic Reforming 

Units, and Sulfur Recovery Units. EPA-453/R-98-003. Washington, DC: Government 

Printing Office. 

U.S. Environmental Protection Agency. 2006. Documentation for the Final 2002 Point Source 

National Emissions Inventory. Research Triangle Park, NC. February 10. Report and 

data available at: http://www.epa.gov/ttn/chief/net/2002inventory.html. 

U.S. Environmental Protection Agency. 2008. Inventory of Greenhouse Gas Emissions and 

Sinks: 1990-2006. EPA-430-R-08-005. Office of Atmospheric Programs, Washington, 

DC. April 15. 
25

Appendix A. Derivation of Calculation Methods 

Most of the calculation methods being considered for the reporting of GHG emissions from 

refineries are fairly straight-forward and are documented elsewhere.

1, 2 This section provides 

additional information for a few of the methods being evaluated and were specifically developed 

to reduce the burden for estimating fugitive emission from sources that are not expected to 

contribute significantly to the overall GHG inventory for U.S. petroleum refineries. 

A.1 Equipment Leaks 

The Equipment Leaks Protocol Document contains a variety of methods that may be used to 

estimate fugitive emissions from leaking process equipment.3 To use these methods for 

estimating methane emissions, the average methane concentration of the various refinery process 

streams would need to be measured or estimated, and the number of equipment components 

would need to be determined. Many refineries already have these data, and can use the methods 

in the Protocol Document directly. For refineries that do not have these data readily available, a 

simple method of estimating these emissions was developed. First, methane emissions from 

fugitive equipment leaks were estimated using: 

¡ A set leak fraction of 2 percent (1.4 percent with leaks greater than 10,000 ppmv but less 

than 100,000 ppmv, and 0.6 percent with leaks greater than 10,000 ppmv). 

¡ The zero and pegged value leak equations from the Protocol Document as provided in 

Table A-1 of this report. 

¡ Model refinery equipment component counts from EPA’s Locating and Estimating 

Emission of Benzene document as well as estimated component counts for fuel gas 

systems as provided in Tables A-2 and A-3 of this report.4

¡ An estimated methane composition for each model process unit as provided in Table A-4. 

Table A-4 also summarizes the methane emissions per model process unit. 

 

1 EPA, 2008. Inventory of Greenhouse Gas Emissions and Sinks: 1990-2006. EPA-430-R-08-005. Office of 

Atmospheric Programs, Washington, DC. April 15. 

2 API, 2004. Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Gas Industry. February. 

3 U.S. EPA (Environmental Protection Agency). 1995. Protocol for Equipment Leak Emission Estimates. EPA453/R-95-017. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

4 U.S. EPA (Environmental Protection Agency). 1998a. Locating and Estimating Air Emissions from Sources of 

Benzene. EPA-454/R-98-011. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 
26

Table A-1. Fugitive Equipment Leak Rate for Refinery Equipment Components.a

Equ Pegged Emission Rates (kg/hr/source) ipment Type (All 

Services)

Default Zero Emission 

Rate (kg/hr/source) 10,000 ppmv 100,000 ppmv

Valve 7.8E-06 0.064 0.140 

Pump 2.4E-05 0.074 0.160 

Otherb4.0E-06 0.073 0.110 

Connector 7.5E-06 0.028 0.030 

Flange 3.1E-07 0.085 0.084 

Open-Ended Line 2.0E-06 0.030 0.079 

a As reported in U.S. EPA (1995, see footnote 3) 

b

The “other” equipment type was developed from instruments, loading arms, pressure relief devices, stuffing boxes, 

vents, compressors, dump lever arms, diaphragms, drains, hatches, meters, and polished rods. This “other” 

equipment type should be applied to any equipment other than connectors, flanges, open-ended lines, pumps, or 

valves. 

As seen by the estimated emissions for the model process units in Table A-4, the fuel gas system 

and the hydrogen plant are expected to produce the majority of the refinery’s methane emissions. 

From the results presented in Table A-4, the average methane emissions between the small and 

large model plants for fuel gas systems and hydrogen plants is 6.0 and 4.3 mt/yr, respectively. 

For crude oil distillation columns, the average methane emissions rate is approximately 0.4 

mt/yr. Several process units in Table A-4 were projected to have average emission rates of 

approximately 0.2 mt/yr, and several other process units were projected to have average emission 

rates of approximately 0.1 mt/yr. 

Based on this analysis, Equation 1 was developed to provide a very quick and simple method for 

estimating methane emissions from fugitive equipment leaks at a refinery. 

( ) CH NCD NPU NPU N H NFGS 0.4* 0.2 * 0.1* 4.3* 6 *

4 = + 1 + 2 + 2 + (Equation 1) 

Where: 

CH4 = annual methane emissions from fugitive equipment leaks (mtCH4/yr) 

 NCD = number of atmospheric crude oil distillation columns at the facility 

 NPU1 = cumulative number of catalytic cracking units, coking units (delayed or fluid), 

hydrocracking, and full-range distillation columns (including depropanizer and 

debutanizer distillation columns) at the facility 

 NPU2 = cumulative number of hydrotreating/hydrorefining units, catalytic reforming units, and 

visbreaking units at the facility 

 NH2 = total number of hydrogen plants at the facility 

 NFGS = total number of fuel gas systems at the facility 
27

Table A-2. Median Equipment Leak Component Counts for Small Model Processes.a

Valves Pumps

Pressure Relief 

Valves Flanges

Process Unit Gas 

Light 

Liquid

Heavy 

Liquid

Light 

Liquid

Heavy 

Liquid

Compressors Gas 

Light 

Liquid

Heavy 

Liquid Gas 

Light 

Liquid

Heavy 

Liquid

OpenEnded 

Lines

Sampling 

Connections

Crude Distillation 75 251 216 8 8 2 6 6 5 164 555 454 39 10

Alkylation (sulfuric acid) 278 582 34 18 10 1 12 15 4 705 1296 785 20 16

Alkylation (HF) 102 402 62 13 3 2 12 13 0 300 1200 468 26 8

Catalytic Reforming 138 234 293 8 5 3 5 3 3 345 566 732 27 6

Hydrocracking 300 375 306 12 9 2 9 4 4 1038 892 623 25 10

Hydrotreating/Hydrorefining 100 208 218 5 5 2 5 3 5 290 456 538 20 6

Catalytic Cracking 186 375 450 13 14 2 8 8 7 490 943 938 8 8

Thermal Cracking 

(visbreaking) 206 197 0 7 0 0 4 0 0 515 405 0 0 4

Thermal Cracking (coking) 148 174 277 9 8 2 7 16 13 260 322 459 13 8

Hydrogen Plant 168 41 0 3 0 2 4 2 0 304 78 0 8 4

Asphalt Plant 120 334 250 5 8 2 5 10 9 187 476 900 16 6

Product Blending 67 205 202 6 11 1 10 6 22 230 398 341 33 14

Sulfur Plant 58 96 127 6 6 3 3 88 15 165 240 345 50 3

Vacuum Distillation 54 26 84 6 6 2 2 5 2 105 121 230 16 4

Full-Range Distillation 157 313 118 7 4 2 5 4 6 171 481 210 20 6

Isomerization 270 352 64 9 2 2 7 10 1 432 971 243 7 8

Polymerization 224 563 15 12 0 1 10 5 3 150 450 27 5 7

MEK Dewaxing 145 1208 200 35 39 3 10 14 4 452 1486 2645 19 17

Other Lube Oil Processes 153 242 201 7 5 2 5 5 5 167 307 249 60 6

Fuel Gas Systemb 120 0 0 0 0 2 5 0 0 300 0 0 20 5

a Process component counts (except for fuel gas system) as presented in the Benzene L&E document (U.S. EPA, 1998; see footnote 4) for refineries with crude 

capacities less than 50,000 bbl/cd 

b

Fuel gas system component counts estimated using engineering judgment. 
28

Table A-3. Median Equipment Leak Component Counts for Large Model Processes.a

Valves Pumps

Pressure Relief 

Valves Flanges

Process Unit Gas 

Light 

Liquid

Heavy 

Liquid

Light 

Liquid

Heavy 

Liquid

Compressors Gas

Light 

Liquid

Heavy 

Liquid Gas 

Light 

Liquid

Heavy 

Liquid

OpenEnded 

Lines

Sampling 

Connections

Crude Distillation 204 440 498 15 14 2 7 5 12 549 982 1046 75 9

Alkylation (sulfuric acid) 192 597 0 21 0 2 13 4 0 491 1328 600 35 6

Alkylation (HF) 104 624 128 13 8 1 9 11 1 330 1300 180 40 14

Catalytic Reforming 310 383 84 12 2 3 8 11 0 653 842 132 48 9

Hydrocracking 290 651 308 22 12 2 10 12 0 418 1361 507 329 28

Hydrotreating/Hydrorefining 224 253 200 7 6 2 9 4 8 439 581 481 49 8

Catalytic Cracking 277 282 445 12 12 2 11 9 13 593 747 890 59 15

Thermal Cracking 

(visbreaking) 110 246 130 7 6 1 6 3 15 277 563 468 30 7

Thermal Cracking (coking) 190 309 250 12 11 1 8 5 10 627 748 791 100 10

Hydrogen Plant 301 58 0 7 360 3 4 139 0 162 148 0 59 21

Asphalt Plant 76 43 0 4 0 0 3 7 0 90 90 0 24 24

Product Blending 75 419 186 10 10 2 9 16 6 227 664 473 24 8

Sulfur Plant 100 125 110 8 3 1 4 4 4 280 460 179 22 7

Vacuum Distillation 229 108 447 2 12 1 5 1 4 473 136 1072 0 7

Full-Range Distillation 160 561 73 14 2 2 7 8 2 562 1386 288 54 6

Isomerization 164 300 78 9 5 2 15 5 2 300 540 265 36 7

Polymerization 129 351 82 6 2 0 7 12 28 404 575 170 17 9

MEK Dewaxing 419 1075 130 29 10 4 33 6 18 1676 3870 468 0 7

Other Lube Oil Processes 109 188 375 5 16 3 8 6 20 180 187 1260 18 9

Fuel Gas Systemb 120 0 0 0 0 2 5 0 0 300 0 0 20 5

a Process component counts (except for fuel gas system) as presented in the Benzene L&E document (U..S. EPA, 1998; see footnote 4) for refineries with crude 

capacities of 50,000 bbl/cd of greater. 

b

Fuel gas system component counts estimated using engineering judgment. 
29

Table A-4. Estimated Methane Concentration and Fugitive Emission Rates for Model 

Refinery Process Units. 

Concentration of Methane 

(weight fraction)a

Methane Emission Rate 

(tonnes CH4/yr) 

Process Unit Gas Stream 

Light Liquid 

Stream 

Small Model 

Plant 

Large Model 

Plant 

Crude Distillation 0.05 0.000005 0.185 0.570

Alkylation (sulfuric acid) 0 0 0 0

Alkylation (HF) 0 0 0 0

Catalytic Reforming 0.01 0 0.074 0.146

Hydrocracking 0.02 0 0.403 0.216

Hydrotreating/hydrorefining 0.01 0 0.059 0.101

Catalytic Cracking 0.02 0 0.205 0.265

Thermal Cracking (visbreaking) 0.01 0 0.109 0.059

Thermal Cracking (coking) 0.02 0 0.125 0.247

Hydrogen Plant 0.6 0.0001 4.300 4.264

Asphalt Plant 0 0 0 0

Product Blending 0 0 0 0

Sulfur Plant 0.001 0 0.003 0.006

Vacuum Distillation 0.001 0 0.002 0.011

Full-Range Distillation 0.02 0 0.101 0.218

Isomerizaiton 0 0 0 0

Polymerization 0 0 0 0

MEK Dewaxing 0 0 0 0

Other Lube Oil Processing 0 0 0 0

Aromatics 0 0 0 0

Fuel Gas System 0.7 0 4.472 7.468

a Methane concentrations for heavy liquids were assumed to be negligible. 

A.2 Storage Tanks 

Methane (CH4) emissions can occur from petroleum refinery storage tanks. Crude oil storage 

tanks are expected to be the primary contributor to the GHG emissions from storage tanks. Most 

other intermediate and final product storage tanks are expected to have negligible CH4 emissions 

as the stored liquids typically do not contain any CH4. When crude oil is initially pumped from 

the well, the crude oil can contain significant amounts of CH4 because the crude is stored under 

pressure within the oil reservoir. When the oil is first stored at atmospheric conditions at the 

well site, significant amounts of light organics, including CH4, are released from the crude oil, 

commonly referred to as flashing losses. After the light volatiles have flashed from the crude oil, 

the “stabilized” crude oil is then transported to the refineries for further processing. As such, 

most of the CH4 emissions from crude oil storage typically occur upstream of the petroleum 
30

refinery. If the crude oil is transported under pressure (e.g., via pipeline) before the crude oil is 

stabilized, significant CH4 emissions can occur at the refinery from flashing losses in the crude 

oil storage tanks. 

The TANKS model is a tool that implements the AP-42 emission estimation methods (developed 

by API) for organic liquid storage.5 The TANKS model is not applicable for estimating the 

emissions from unstabilized crude oil. The API Compendium of Greenhouse Gas Emissions 

Methodologies for the Oil and Gas Industry contains a variety of methods that may be used to 

estimate flashing losses from storage tanks.6 One of the simpler correlation equation methods 

presented in the API Compendium and one of the few that is applicable to refinery storage tanks 

is referred to as the EUB (Energy and Utilities Board) Rule-of-Thumb approach. The EUB 

Rule-of-Thumb correlation equation estimates the volume of gas released. Using the molar 

volume of gas at standard conditions and the CH4 content of the gas, the EUB Rule-of-Thumb 

approach can be used to calculate flashing losses from storage tanks as follows: 

( ) * 0.001 16 0.995* * * *

4 4 MVC

CH = Qun ΔP MFCH (Equation 2) 

Where: 

CH4 = emission rate of methane from storage tanks (mtCH4/yr) 

Qun = quantity of unstabilized crude oil received at the facility (bbl/yr) 

ΔP = pressure differential from the previous storage pressure to atmospheric pressure 

(pounds per square inch) 

MFCH4 = mole fraction of CH4 in vent gas from the unstabilized crude oil storage tank from 

facility measurements; use 0.27 as a default if measurement data are not available. 

0.995 = correlation equation factor (scf gas per bbl per psi) 

16 = molecular weight of CH4 (kg/kg-mole). 

MVC = molar volume conversion factor (849.5 scf/kg-mole). 

0.001 = conversion factor (mt/kg). 

For stabilized crude oil, the TANKS model (current version is 4.09D) can be used to estimate 

CH4 emissions from crude oil storage tanks. The TANKS model generally outputs total 

hydrocarbon losses, so the CH4 content of the released vapor must be determined. It is important 

not to use the liquid phase composition for this estimate as the vapors will have much higher 

relative CH4 concentrations than in the liquid phase. The TANKS model was used to estimate 

the hydrocarbon losses for crude oil using the default crude oil properties pre-loaded in the 

TANKS model (Crude oil with a Reid vapor pressure of 5 psi and average molecular weight of 

vapor of 50 g/mol). Concentrations of C5 through C8 hydrocarbons in the crude oil were 

estimated based on average crude oil compositions reported in Potter and Simmons.7 

 

5 U.S. EPA (Environmental Protection Agency). 1995a. Compilation of Air Pollutant Emission Factors. 

Sections 7. AP-42. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

6 API, 2004. Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Gas Industry. February. 

7

Potter, T.L., and K.E. Simmons. 1998. Composition of Petroleum Mixtures. Total Petroleum Hydrocarbon Criteria 

Working Group Series, Volume 2. May. 
31

Concentrations of C1 through C4 hydrocarbons in the crude oil were estimated based on best 

engineering judgment and adjusted so that the average molecular weight of the equilibrium gas 

mixture was 50 g/mol (to match the TANKS model assumption). Although the estimated CH4

concentration in the crude oil was only 5 parts per million by weight (ppmw), the vapor phase 

was projected to contain just under 8 percent CH4. Therefore the total hydrocarbon emissions 

rates estimated using the TANKS model were multiplied by 8 percent to estimate a CH4

emissions factor for crude oil storage tanks. Several crude oil storage tanks with different 

floating roof seal designs and component fittings were evaluated. All of the tanks were 200 ft 

diameter, 7.5-million gallon capacity tanks, with an estimated throughput of 20,000 to 

25,000 bbls per day (40 to 50 turnovers per year). The tanks were evaluated at a number of 

meteorological locations. Based on this evaluation, an emission factor of 0.1 Mg CH4/million 

bbls of crude throughput was developed. The uncertainty of this default emission factor is large, 

roughly factor of 2 or 3, based on the results for different tank runs. Nonetheless, it provides a 

very simple means of estimating CH4 emissions from crude oil storage tanks, and presumably all 

storage tanks at the refinery, and is appropriate given the small contribution of storage tank 

emissions in the overall GHG emissions inventory for a petroleum refinery. 

A.3 Delayed Coking Unit Coke Cutting 

Methane emissions have been found in recent delayed coking vessel depressurization vent tests, 

and the tests noted that significant emissions appeared to occur when the coke vessel was 

opened.8, 9, 10, 11 Additionally, other test data indicate that significant emissions continue to occur 

during the coke cutting operations.

12

 From the delayed coking vessel depressurization vent tests, 

methane is approximately 30 percent of the gas volume on a dry basis. However, water is added 

to the coking drum to cool the coke, and the water vaporizes. Consequently, the coker 

depressurization vent stream is 90 percent or more water vapor. It is unknown how much of the 

void space within the coke drum is well purged with steam and what fraction is trapped and only 

released to the atmosphere during the coke cutting operations. Any trapped gas is expected to 

have high concentrations of methane (roughly 30 percent by volume). 

 

8

South Coast Air Quality Management District. 2004a. Source Test Report 03-194 Conducted at Chevron / Texaco 

Refinery, El Segundo, California—Volatile Organic Compound (VOC), Carbon Monoxide (CO), and Particulate 

Matter (PM) Emissions From a Coke Drum Steam Vent. May 14. 

9

South Coast Air Quality Management District. 2004b. Source Test Report 03-197 Conducted at Conoco-Phillips 

Refinery, Carson, California—Volatile Organic Compound (VOC), Carbon Monoxide (CO), and 

Particulate Matter (PM) Emissions From a Coke Drum Steam Vent. July 23. 

10 South Coast Air Quality Management District. 2004c. Source Test Report 03-198 Conducted at Exxon Mobil 

Refinery, Torrance, California—Volatile Organic Compound (VOC), Carbon Monoxide (CO), and Particulate 

Matter (PM) Emissions From a Coke Drum Steam Vent. March 4. 

11 South Coast Air Quality Management District. 2004d. Source Test Report 03-200 Conducted at Shell Oil 

Refinery, Wilmington, California—Volatile Organic Compound (VOC), Carbon Monoxide (CO), and 

Particulate Matter (PM) Emissions From a Coke Drum Steam Vent. July 1. 

12 Chambers, A., and M. Strosher. 2006. Refinery Demonstration of Optical Technologies for Measurement of 

Fugitive Emissions and for Leak Detection. Prepared for Environment Canada, Ontario Ministry of the 

Environment, and Alberta Environment. Project No. CEM 9643-2006. March 31. 
32

Although some of the coke drum is filled with coke, the coke is quite porous, so a rough estimate 

of the gas within the coke drum can be estimated by the dimensions of the coke drum vessel 

itself. A default methane concentration of 3 percent by volume is recommended based on the 

typical methane dry composition of 30 percent by volume and the lower range of water content 

in the depressurization purge vent. If a facility has data for the coker drum purge vent (but not 

during periods of active steaming), then that concentration can be used to estimate the vaporphase concentration within the coker drum. While using the direct volume of the coke drum 

vessel will over-estimate the amount of gas released, the actual concentration of the gas within 

the vessel is expected to be somewhat higher than the purge vent concentrations because of the 

likelihood of trapped gas pockets. Thus, the combination of the purge vent concentration 

combined with the entire vessel volume assumption is expected to provide a reasonable estimate 

of the methane emissions when the coke drum vessel is opened and subsequently de-coked. 

Consequently, Equation 3 was developed to estimate the methane emissions from opening the 

coke drum vessel and subsequent coke cutting operations. 

 

















= * *0.001 16 *

4

*

* *

4

2

4 MFCH MVC

D

CH N H

p

(Equation 3) 

Where: 

CH4 = annual CH4 emissions from the delayed coking unit vessel opening (mtCH4/yr) 

N = total number of vessel openings for all delayed coking unit vessels of the same 

dimensions during the year 

H = height of coking unit vessel (ft) 

D = diameter of coking unit vessel (ft) 

16 = molecular weight of CH4 (kg/kg-mole) 

MVC = molar volume conversion (849.5 scf/ kg-mole) 

MFCH4 = mole fraction of methane in coking vessel gas; default value is 0.03 

0.001 = conversion factor – kg to metric tonnes.