A-1

Annexes to the Inventory of U.S. GHG Emissions and Sinks 

The following seven annexes provide additional information related to the material presented in the main body of 

this report as directed in the UNFCCC Guidelines on Reporting and Review (GE.03-60887). Annex 1 contains an analysis 

of the key categories of emissions discussed in this report and a review of the methodology used to identify those key 

categories. Annex 2 describes the methodologies used to estimate CO2 emissions from fossil fuel combustion, the carbon 

content of fossil fuels, and the amount of carbon stored in products from non-energy uses of fossil fuels. Annex 3 

discusses the methodologies used for a number of individual source categories in greater detail than was presented in the 

main body of the report and includes explicit activity data and emission factor tables. Annex 4 presents the IPCC 

reference approach for estimating CO2 emissions from fossil fuel combustion. Annex 5 addresses the criteria for the 

inclusion of an emission source category and discusses some of the sources that are excluded from U.S. estimates. Annex 

6 provides a range of additional information that is relevant to the contents of this report. Annex 7 provides data on the 

uncertainty of the emission estimates included in this report. Finally, Annex 8 provides information on the QA/QC 

methods and procedures used in the development of the Inventory. 

ANNEX 1 Key Category Analysis ................................................................................................................................................................ 2

ANNEX 2 Methodology and Data for Estimating CO2 Emissions from Fossil Fuel Combustion ............................................................... 27

2.1. Methodology for Estimating Emissions of CO2 from Fossil Fuel Combustion ..................................................................... 27

2.2. Methodology for Estimating the Carbon Content of Fossil Fuels......................................................................................... 59

2.3. Methodology for Estimating Carbon Emitted from Non-Energy Uses of Fossil Fuels ......................................................... 98

ANNEX 3 Methodological Descriptions for Additional Source or Sink Categories................................................................................... 125

3.1. Methodology for Estimating Emissions of CH4, N2O, and Indirect Greenhouse Gases from Stationary Combustion....... 125

3.2. Methodology for Estimating Emissions of CH4, N2O, and Indirect Greenhouse Gases from Mobile Combustion and 

Methodology for and Supplemental Information on Transportation-Related GHG Emissions................................................................. 132

3.3. Methodology for Estimating Emissions from Commercial Aircraft Jet Fuel Consumption................................................. 164

3.4. Methodology for Estimating CH4 Emissions from Coal Mining .......................................................................................... 168

3.5. Methodology for Estimating CH4 and CO2 Emissions from Natural Gas Systems............................................................. 175

3.6. Methodology for Estimating CH4 and CO2 Emissions from Petroleum Systems ............................................................... 202

3.7. Methodology for Estimating CO2, N2O and CH4 Emissions from the Incineration of Waste .............................................. 209

3.8. Methodology for Estimating Emissions from International Bunker Fuels used by the U.S. Military .................................. 214

3.9. Methodology for Estimating HFC and PFC Emissions from Substitution of Ozone Depleting Substances ...................... 219

3.10. Methodology for Estimating CH4 Emissions from Enteric Fermentation............................................................................ 240

3.11. Methodology for Estimating CH4 and N2O Emissions from Manure Management ............................................................ 258

3.12. Methodology for Estimating N2O Emissions and Soil Organic C Stock Changes from Agricultural Soil Management 

(Cropland and Grassland)........................................................................................................................................................................ 287

3.13. Methodology for Estimating Net Carbon Stock Changes in Forest Lands Remaining Forest Lands ................................ 338

3.14. Methodology for Estimating CH4 Emissions from Landfills................................................................................................ 367

ANNEX 4 IPCC Reference Approach for Estimating CO2 Emissions from Fossil Fuel Combustion ....................................................... 385

ANNEX 5 Assessment of the Sources and Sinks of Greenhouse Gas Emissions Not Included............................................................. 395

ANNEX 6 Additional Information.............................................................................................................................................................. 397

6.1. Global Warming Potential Values ...................................................................................................................................... 397

6.2. Ozone Depleting Substance Emissions............................................................................................................................. 406

6.3. Sulfur Dioxide Emissions ................................................................................................................................................... 407

6.4. Complete List of Source Categories .................................................................................................................................. 409

6.5. Constants, Units, and Conversions ................................................................................................................................... 410

6.6. Abbreviations ..................................................................................................................................................................... 412

6.7. Chemical Formulas............................................................................................................................................................ 417

ANNEX 7 Uncertainty............................................................................................................................................................................... 421

7.1. Overview............................................................................................................................................................................ 421

7.2. Methodology and Results .................................................................................................................................................. 421

7.3. Planned Improvements...................................................................................................................................................... 428

7.4. Additional Information on Uncertainty Analyses by Source ............................................................................................... 429

ANNEX 8 QA/QC Procedures.................................................................................................................................................................. 450

8.1. Background........................................................................................................................................................................ 450

8.2. Purpose.............................................................................................................................................................................. 450

8.3. Assessment Factors .......................................................................................................................................................... 451
A-202 Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012

3.6. Methodology for Estimating CH4 and CO2 Emissions from Petroleum Systems

The methodology for estimating CH4 and non-combustion CO2 emissions from petroleum systems is based on 

the 1999 EPA draft report, Estimates of Methane Emissions from the U.S. Oil Industry (EPA 1999) and the study, Methane 

Emissions from the U.S. Petroleum Industry (EPA/GRI 1996). Sixty-four activities that emit CH4 and thirty activities that 

emit non-combustion CO2 from petroleum systems were examined from these reports. Most of the activities analyzed 

involve crude oil production field operations, which accounted for over 98 percent of total oil industry CH4 emissions. 

Crude transportation and refining accounted for the remaining CH4 emissions of less than 0.4 and less than 1.3 percent, 

respectively. Non-combustion CO2 emissions were analyzed for production operations and asphalt blowing in refining 

operations. Non-combustion CO2 emissions from transportation operations are not included because they are negligible. 

The following steps were taken to estimate CH4 and CO2 emissions from petroleum systems.

Step 1: Calculate Potential Methane and Carbon Dioxide

Activity Data

Activity levels change from year to year. Some data changes in proportion to crude oil rates: production, 

transportation, refinery runs. Some change in proportion to the number of facilities: oil wells, petroleum refineries. Some

factors change proportional to both the rate and number of facilities.

For most sources, activity data for 1995 found in EPA/GRI 1996 are extrapolated to other years using publiclyavailable data sources. For the remaining sources, the activity data are obtained directly from publicly available data.

For both sets of data, a determination was made on a case-by-case basis as to which measure of petroleum 

industry activity best reflects the change in annual activity. Publicly-reported data from the Bureau of Ocean Energy 

Management (BOEM), Energy Information Administration (EIA), American Petroleum Institute (API), the Oil & Gas 

Journal (O&GJ), the Interstate Oil and Gas Compact Commission (IOGCC), and the U.S Army Corps of Engineers 

(USACE) were used to extrapolate the activity data from the base year to each year between 1990 and 2012. Data used 

include total domestic crude oil production, number of domestic crude oil wells, total imports and exports of crude oil, 

total petroleum refinery crude runs, and number of oil-producing offshore platforms. The activity data for the total crude 

transported in the transportation sector is not available. In this case, all the crude oil that was transported was assumed to 

go to refineries. Therefore, the activity data for the refining sector was used also for the transportation sector. In the few 

cases where no data was located, oil industry data based on expert judgment was used. In the case of non-combustion CO2 

emission sources, the activity factors are the same as for CH4 emission sources.

Potential methane factors and emission factors

The CH4 emission factors for the majority of the activities are taken from the 1999 EPA draft report, which 

contained the most recent and comprehensive determination of CH4 emission factors for the 64 CH4-emitting activities in 

the oil industry at that time. Emission factors for pneumatic devices in the production sector were recalculated in 2002 

using emissions data in the EPA/GRI 1996c study. The gas engine emission factor is taken from the EPA/GRI 1996b 

study. The oil tank venting emission factor is taken from the API E&P Tank Calc weighted average for API gravity less 

than 45 API degrees with the distribution of gravities taken from a sample of production data from the HPDI database. 

Offshore emissions from shallow water and deep water oil platforms are taken from analysis of the Gulf-wide Offshore 

Activity Data System (GOADS) report (EPA 2005, BOEMRE 2004). The emission factors were assumed to be 

representative of emissions from each source type over the period 1990 through 2012. Therefore, the same emission 

factors are used for each year throughout this period.

The CO2 emission factors were derived from the corresponding source CH4 emission factors. The amount of CO2

in the crude oil stream changes as it passes through various equipment in petroleum production operations. As a result, 

four distinct stages/streams with varying CO2 contents exist. The four streams that are used to estimate the emissions 

factors are the associated gas stream separated from crude oil, hydrocarbons flashed out from crude oil (such as in storage 

tanks), whole crude oil itself when it leaks downstream, and gas emissions from offshore oil platforms. The standard 

approach used to estimate CO2 emission factors was to use the existing CH4 emissions factors and multiply them by a 

conversion factor, which is the ratio of CO2 content to methane content for the particular stream. Ratios of CO2 to CH4

volume in emissions are presented in Table A-151. The two exceptions are the emissions factor for storage tanks, which is 

estimated using API E&P Tank Calc simulation runs of tank emissions for crude oil of different gravities less than 45 API 

degrees; and the emissions factor for uncontrolled asphalt blowing, which is estimated using the data and methods 

provided by API (2009).
A-203

Step 2: Compile Reductions Data

The methane emissions calculated in Step 1 above generally represent expected emissions from an activity in the 

absence of emissions controls, and do not take into account any use of technologies or practices that reduce emissions. To 

take into account use of such technologies, data were collected on voluntary reductions. Voluntary reductions included in 

the Petroleum Sector calculations were those reported to Gas STAR for the following activities: Artificial lift: gas lift, 

Artificial lift: use compression, Artificial lift: use pumping unit, Consolidate crude oil prod and water storage tanks, Lower 

heater-treater temperature, Re-inject gas for enhanced oil recovery, Re-inject gas into crude, and Route casinghead gas to 

VRU or compressor. 

Industry partners report CH4 emission reductions by project to the Natural Gas STAR Program. The reductions 

from the implementation of specific technologies and practices are calculated by the reporting partners using actual 

measurement data or equipment-specific emission factors. The reductions undergo quality assurance and quality control 

checks to identify errors, inconsistencies, or irregular data before being incorporated into the Inventory. The Inventory 

uses aggregated Gas STAR reductions for the petroleum sector. 

Step 3: Calculate Net Methane and Carbon Dioxide Emissions for Each Activity for Each Year

Annual CH4 emissions from each of the 64 petroleum system activities and CO2 emissions from the 30 petroleum 

system activities were estimated by multiplying the activity data for each year by the corresponding emission factor. 

These annual emissions for each activity were then summed to estimate the total annual CH4 and CO2 emissions, 

respectively. Gas Star reductions data is summed for each year and deducted from the potential CH4 calculated in Step 1 

to estimate net CH4 emissions for the Inventory. 

Table A-147, Table A-148, Table A-149, and Table A-152 provide 2012 activity data, emission factors, and 

emission estimates and Table A-150 and Table A-153 provide a summary of emission estimates for the years 1990, 1995, 

2000, and 2005 through 2012. Table A-151 provides the CO2 content in natural gas for equipment in different crude 

streams to estimate CO2 emission factors using CH4 emission factors.

The tables provide references for emission factors and activity data in footnotes (the lettered footnotes). The 

tables also provide information on which method was used for supplying activity data for 2012 (the numbered footnotes). 

Key to table notations on methods for supplying activity data for 2012 for all tables:

1. Ratios relating other factors for which activity data are available. For example, EPA (1996) found that the 

number of heater treaters (a source of CH4 emissions) is related to both number of producing wells and 

annual production. To estimate the activity data for heater treaters, reported statistics for wells and 

production were used, along with the ratios developed for EPA (1996).

2. Activity data for 2012 available from source.

3. Activity data was held constant from 1990 through 2012 based on EPA (1999).

4. 2009, 2010, or 2011 activity data are used to determine some or all of the 2012 activity data.

Table A-147: 2012 CH4 Emissions from Petroleum Production Field Operations 

Activity/Equipment

2012 EPA Inventory Values

Emission Factor Activity Data Emissions

(Bcf/yr)

Emissions

(Gg/yr)

Vented Emissions 71.623 1,377.373

Oil Tanks

7.39 scf of CH4/bbl crudea 1,878

MMbbl/yr (non stripper 

wells)b,c,d,1,4 13.890 267.121

Pneumatic Devices, High Bleed

330 scfd CH4/devicef 145,179 

No. of high-bleed 

devicesc,e,g,1 17.508 336.692

Pneumatic Devices, Low Bleed

52 scfd CH4/devicef 269,618 

No. of low-bleed 

devicesc,e,g,1 5.117 98.411

Chemical Injection Pumps 248 scfd CH4/pumph 28,702 No. of pumpsg,i,p1 2.599 49.973

Vessel Blowdowns 78 scfy CH4/vesselh 189,710 No. of vesselsc,g,i,1 0.015 0.285

Compressor Blowdowns 3,775 scf/yr of CH4/compressorh 2,582 No. of compressorsc,g,i,1 0.010 0.187

Compressor Starts 8,443 scf/yr of CH4/compressorh 2,582 No. of compressorsc,g,i,1 0.022 0.419

Stripper wells

2,345 scf/yr of CH4/stripper wellf 315,213 

No. of stripper wells 

ventedf,1,4 0.739 14.21
A-204 Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012

Activity/Equipment

2012 EPA Inventory Values

Emission Factor Activity Data Emissions

(Bcf/yr)

Emissions

(Gg/yr)

Well Completion Venting 733 scf/completionh 15,753 Oil well completionsc,2 0.012 0.222

Well Workovers 96 scf CH4/workoveri 40,200 Oil well workoversg,i,1 0.004 0.074

Pipeline Pigging 2.40 scfd of CH4/pig stationj 0 No. of crude pig stationse,3 - -

Offshore Platforms, Shallow water Oil, 

fugitive, vented and combusted 54,795 scfd CH4/platformk 1,447

No. of shallow water oil 

platformsl,4 28.930 556.353

Offshore Platforms, Deepwater oil, 

fugitive, vented and combusted 260,274 scfd CH4/platformk 29 

No. of deep water oil 

platformsl,4 2.778 53.419

Fugitive Emissions 2.669 51.330

Oil Wellheads (heavy crude)

0.13 scfd/welle,m 15,565

No. of hvy. crude 

wellsd,g,i,1,4 0.001 0.014

Oil Wellheads (light crude) 16.6 scfd/welle,m 205,222 No. of lt. crude wellsd,g,i,1,4 1.246 23.956

Separators (heavy crude)

0.15 scfd CH4/separatore,m 11,142 

No. of hvy. crude 

seps.c,g,i,1 0.001 0.012

Separators (light crude) 14 scfd CH4/separatore,m 101,402 No. of lt. crude seps.c,g,i,1 0.513 9.860

Heater/Treaters (light crude) 19 scfd CH4/heatere,m 77,166 No. of heater treatersc,g,i,1 0.541 10.396

Headers (heavy crude) 0.08 scfd CH4/headere,m 13,982 No. of hvy. crude hdrs.g,i,1 0.000* 0.008

Headers (light crude) 11 scfd CH4/headere,m 43,344 No. of lt. crude hdrs.g,i,1 0.172 3.303

Floating Roof Tanks 338,306 scf CH4/floating roof tank/yrm,n 24 No. of floating roof tankse,3 0.008 0.159

Compressors 100 scfd CH4/compressore 2,582 No. of compressorsc,g,i,1 0.094 1.812

Large Compressors 16,360 scfd CH4/compressore 0 No. of large comprs.e,3 - -

Sales Areas 41 scf CH4/loadinge 1,974,334 Loadings/yearc,1 0.080 1.540

Pipelines NE scfd of CH4/mile of pipeline 14,077 Miles of gathering lineo,2 NE NE

Well Drilling NE scfd of CH4/oil well drilled 17,774 No. of oil wells drilledc,2 NE NE

Battery Pumps 0.24 scfd of CH4/pumpm 160,800 No. of battery pumpsg,e,1 0.014 0.271

Combustion Emissions 5.188 99.765

Gas Engines 0.24 scf CH4/HP-hrh 16,264 MMHP-hrc,g,i,1 3.903 75.063

Heaters 0.52 scf CH4/bbln 2,369.6 MMbbl/yrc,2 1.235 23.746

Well Drilling 2,453 scf CH4/well drilledm 17,774 Oil wells drilledc,2 0.044 0.838

Flares 20 scf CH4/Mcf flaredj 305,587 Mcf flared/yr b,c,d,1,4 0.006 0.118

Process Upset Emissions 0.155 2.980

Pressure Relief Valves 35 scf/yr/PR valve 197,931 No. of PR valves 0.007 0.132

Well Blowouts Onshore 2.5 MMscf/blowout 59.2 No. of blowouts/yr 0.148 2.848

Voluntary Reductions 2.34 45

Total Potential Emissions 79.64 1,531.447

Total Net Emissions 77.29 1,486

a TankCALC

b EPA / ICF International (1999)

c Energy Information Administration (EIA) Monthly Energy Review

d Interstate Oil & Gas Compact Commission (IOGCC) Marginal Wells Report

e Consensus of Industrial Review Panel

f Expert Judgment

g EIA Annual Energy Review

h Gas Research Institute (GRI) / EPA (1996)

i Radian (1999)

j Canadian Association of Petroleum Producers (CAPP) (1992)

k Adapted from the Minerals Management Service (MMS) Gulfwide Offshore Activities Data System (GOADS) by ICF (2005)

l Bureau of Ocean Energy Management (BOEM)

m American Petroleum Institute (API) (1996)

n EPA, AP 42 Compilation of Air Pollutant Emission Factors

o Oil and Gas Journal (OGJ) Petroleum Economics Issue

p Percentage of chemical injection pumps (CIPs) that are gas-driven was determined through based on an estimate provided in 1997 by Ron Rayman. From Dresser 

Texsteam, a major manufacturer of CIPs at the time. 

- Zero Emissions

* Emissions are not actually 0, but too small to show at this level of precision.
A-205

Table A-148: 2012 CH4 Emissions from Petroleum Transportation

Activity/Equipment

Emission

Factor Units

Activity

Factor Units

Emissions

(Bcf/yr)

Emissions

(Gg/yr)

Vented Emissions 0.256 4.928

Tanks 0.021 scf CH4/yr/bbl of crude delivered to refineriesa 5,490 MMbbl crude feed/yrb,2 0.113 2.175

Truck Loading 

0.520 scf CH4/yr/bbl of crude transported by truckc 131.3

MMbbl crude trans. by 

truckd,2 0.068 1.313

Marine Loading 2.544 scf CH4/1000 gal crude marine loadingsc 17,518,599 1,000 gal/yr loadede,1,4 0.045 0.857

Rail Loading

0.520 scf CH4/yr/bbl of crude transported by railc 30.1

MMbbl Crude by 

rail/yrd,2 0.016 0.301

Pump Station Maintenance 36.80 scf CH4/station/yrf 513 No. of pump stationsg,1 0.000* 0.000*

Pipeline Pigging 39 scfd of CH4/pig stationh 1,027 No. of pig stationsg,1 0.015 0.281

Fugitive Emissions 0.050 0.959

Pump Stations

25 scf CH4/mile/yrf 51,349

No. of miles of crude 

p/lg,2 0.001 0.025

Pipelines NE scf CH4/bbl crude transported by pipelinef 7,471 MMbbl crude pipedg,2 NE NE

Floating Roof Tanks

58,965 scf CH4/floating roof tank/yri 824

No. of floating roof 

tanks3 0.049 0.934

Combustion Emissions NE NE

Pump Engine Drivers 0.24 scf CH4/hp-hrj NE No. of hp-hrs NE NE

Heaters 0.521 scf CH4/bbl burnedk NE No. of bbl Burned NE NE

Total 0.306 5.887

a API (1992)

b Energy Information Administration (EIA) Petroleum Supply Annual, Volume 1.

c EPA, AP 42 Compilation of Air Pollutant Emission Factors

d EIA Refinery Capacity Report

e EIA Monthly Energy Review

f Radian (1996)

g OGJ Petroleum Economics Issue

h CAPP (1992)

i API TANK

j GRI / EPA (1996)

k EPA / ICF International (1999)

* Emissions are not actually 0, but too small to show at this level of precision.

NE: Not estimated for lack of data

Table A-149: 2012 CH4 Emissions from Petroleum Refining

Activity/Equipment

2012 EPA Inventory Values

Emission Factor Activity Factor Emissions

(Bcf/yr)

Emissions

(Gg/yr)

Vented Emissions 0.798 15.349

 Tanks

20.6 scf CH4/Mbbla 1,930

Mbbl/calendar day heavy crude 

feedb,c,1 0.015 0.279

 System Blowdowns

137 scf CH4/Mbblc 15,040

Mbbl/calendar day refinery 

feedb,2 0.751 14.443

 Asphalt Blowing 2,555 scf CH4/Mbblc 35 Mbbl/calendar day productionb,2 0.033 0.627

Fugitive Emissions 0.087 1.672

 Fuel Gas System 439 Mscf CH4/refinery/yra 144 Refineriesd,2 0.063 1.216

 Floating Roof Tanks 587 scf CH4/floating roof tank/yre 767 No. of floating roof tanks3 0.000* 0.009

 Wastewater Treating 1.88 scf CH4/Mbblc 15,040

Mbbl/calendar day refinery 

feedb,2 0.010 0.199

 Cooling Towers 2.36 scf CH4/Mbblc 15,040

Mbbl/calendar day refinery 

feedb,2 0.013 0.249

Combustion Emissions 0.096 1.842

 Atmospheric Distillation 3.61 scf CH4/Mbblc 15,362 Mbbl/calendar day refinery 0.020 0.389
A-206 Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012

Activity/Equipment

2012 EPA Inventory Values

Emission Factor Activity Factor Emissions

(Bcf/yr)

Emissions

(Gg/yr)

feedd,2

 Vacuum Distillation 3.61 scf CH4/Mbblc 7,133 Mbbl/calendar day feedf,1 0.009 0.181

 Thermal Operations 6.01 scf CH4/Mbblc 2,295 Mbbl/calendar day feed f,1 0.005 0.097

 Catalytic Cracking 5.17 scf CH4/Mbblc 5,034 Mbbl/calendar day feed f,1 0.010 0.183

 Catalytic Reforming 7.22 scf CH4/Mbblc 3,112 Mbbl/calendar day feed f,1 0.008 0.158

 Catalytic Hydrocracking 7.22 scf CH4/Mbblc 1,548 Mbbl/calendar day feed f,1 0.004 0.078

 Hydrorefining 2.17 scf CH4/Mbblc 2,268 Mbbl/calendar day feed f,1 0.002 0.034

 Hydrotreating 6.50 scf CH4/Mbblc 10,401 Mbbl/calendar day feed f,1 0.025 0.474

 Alkylation/Polymerization 12.6 scf CH4/Mbblc 1,088 Mbbl/calendar day feed f,1 0.005 0.096

 Aromatics/Isomeration 1.80 scf CH4/Mbblc 1,011 Mbbl/calendar day feed f,1 0.001 0.013

 Lube Oil Processing 0.00 scf CH4/Mbblc 171 Mbbl/calendar day feed f,1 0.000 0.000

 Engines 0.006 scf CH4/hp-hrg 1,084 MMhp-hr/yrf,1 0.006 0.119

 Flares

0.189 scf CH4/Mbblc,e 15,040

Mbbl/calendar day refinery 

feedb,2 0.001 0.020

Total 0.981 18.864

a API (1992)

b EIA Petroleum Supply Annual, Volume 1.

c Radian (1996)

d EIA Petroleum Navigator

e EPA, AP 42 Compilation of Air Pollutant Emission Factors

f OGJ Refinery Worldwide Report

g GRI / EPA (1996)

* Emissions are not actually 0, but too small to show at this level of precision.

Table A-150: Summary of CH4 Emissions from Petroleum Systems (Gg)

Activity 1990 1995 2000 2007 2008 2009 2010 2011 2012

Production Field Operations 1,680 1,581 1,488 1,415 1,425 1,432 1,443 1,474 1,531

Pneumatic device venting 489 463 428 398 416 419 416 428 435

Tank venting 250 226 214 193 185 202 211 222 267

Combustion & process upsets 115 106 97 90 94 94 95 98 103

Misc. venting & fugitives 799 762 726 714 706 694 700 702 703

Wellhead fugitives 26 25 22 20 24 23 22 24 24

Crude Oil Transportation 7 6 5 5 5 5 5 5 6

Refining 18 18 19 19 19 18 19 19 19

Voluntary Reductions 0.2 1.4 17 64 77 67 60 45 45

Total Potential Emissions 1,704 1,605 1,513 1,439 1,449 1,455 1,467 1,498 1,556

Total Net Emissions 1,704 1,604 1,496 1,376 1,372 1,388 1,407 1,453 1,511

Note: Totals may not sum due to independent rounding.

Table A-151: Ratios of CO2 to CH4 Volume in Emissions from Petroleum Production Field Operations

Whole Crude,

Post-Separator Associated Gas Tank Flash Gas Offshore

Ratio %CO2 / %CH4 0.052 0.020 0.017 0.004

Table A-152: 2012 CO2 Emissions from Petroleum Production Field Operations and Petroleum Refining

Activity/Equipment

2012 EPA Inventory Values

Emission Factor Activity Factor Emissions

(Bcf/yr)

Emissions

(Gg/yr)

Vented Emissions 7.363 389.364

Oil Tanks 3.53 scf of CO2/bbl crudea 1,878 MMbbl/yr (non stripper 

wells)b,c,d,1,4

6.627 350.477

Pneumatic Devices, High Bleed 6.704 scfd CO2/devicef 145,179 No. of high-bleed 

devicesc,e,g,1

0.355 18.787
A-207

Activity/Equipment

2012 EPA Inventory Values

Emission Factor Activity Factor Emissions

(Bcf/yr)

Emissions

(Gg/yr)

Pneumatic Devices, Low Bleed 1.055 scfd CO2/devicef 269,618 No. of low-bleed 

devicesc,e,g,1

0.104 5.491

Chemical Injection Pumps 5.033 scfd CO2/pumph 28,702 No. of pumpsg,i,1 0.053 2.788

Vessel Blowdowns 1.583 scfy CO2/vesselh 189,710 No. of vesselsc,g,i,1 0.000* 0.016

Compressor Blowdowns 77 scf/yr of CO2/compressorh 2,582 No. of compressorsc,g,i,1 0.000* 0.010

Compressor Starts 171 scf/yr of CO2/compressorh 2,582 No. of compressorsc,g,i,1 0.000* 0.023

Stripper wells 48 scf/yr of CO2/stripper wellf 315,213 No. of stripper wells 

ventedf,1,4

0.015 0.793

Well Completion Venting 14.87 scf/completionh 15,753 Oil well completionsc,2 0.000* 0.012

Well Workovers 1.95 scf CO2/workoveri 40,200 Oil well workoversg,i,1 0.000* 0.004

Pipeline Pigging NE scfd of CO2/pig station NE No. of crude pig stations NE NE

Offshore Platforms, Shallow water Oil, 

fugitive, vented and combusted

358 scfd CO2/platformk 1,447 No. of shallow water oil 

platformsl,4

0.189 10.00

Offshore Platforms, Deepwater oil, 

fugitive, vented and combusted

1,701 scfd CO2/platformk 29 No. of deep water oil 

platformsl,4

0.018 0.960

Fugitive Emissions 0.055 2.929

Oil Wellheads (heavy crude) 0.003 scfd/welle,m 15,565 No. of hvy. crude wellsd,g,i,1,4 0.000* 0.001

Oil Wellheads (light crude) 0.337 scfd/welle,m 205,222 No. of lt. crude wellsd,g,i,1,4 0.025 1.337

Separators (heavy crude) 0.003 scfd CO2/separatore,m 11,142 No. of hvy. crude seps.c,g,i,1 0.000* 0.001

Separators (light crude) 0.281 scfd CO2/separatore,m 101,402 No. of lt. crude seps.c,g,i,1 0.010 0.550

Heater/Treaters (light crude) 0.319 scfd CO2/heatere,m 77,166 No. of heater treatersc,g,i,1 0.009 0.475

Headers (heavy crude) 0.002 scfd CO2/headere,m 13,982 No. of hvy. crude hdrs.g,i,1 0.000* 0.000*

Headers (light crude) 0.220 scfd CO2/headere,m 43,344 No. of lt. crude hdrs.g,i,1 0.003 0.184

Floating Roof Tanks 17,490 scf CO2/floating roof 

tank/yrm,n

24 No. of floating roof tankse,3

0.000* 

0.023

Compressors 2.029 scfd CO2/compressore 2,582 No. of compressorsc,g,i,1 0.002 0.101

Large Compressors 332 scfd CO2/compressore 0 No. of large comprs.e,3 0.000 0.000

Sales Areas 2.096 scf CO2/loadinge 1,974,334 Loadings/yearc,1 0.004 0.219

Pipelines NE scfd of CO2/mile of 

pipeline

14,077 Miles of gathering lineo,2 NE NE

Well Drilling NE scfd of CO2/oil well drilled 17,774 No. of oil wells drilledc,2 NE NE

Battery Pumps 0.012 scfd of CO2/pumpm 160,800 No. of battery pumpsg,e,1 0.001 0.039

Process Upset Emissions 0.003 0.178

Pressure Relief Valves 1.794 scf/yr/PR valveh 197,931 No. of PR valvesc,e,1 0.000* 0.019

Well Blowouts Onshore 0.051 MMscf/blowoute 59.0 No. of blowouts/yrc,e,1 0.003 0.159

Refining Emissions 0.265 14.00

 Asphalt Blowing† 20,736 scf CO2/Mbblm 35 Mbbl/calendar day 

productionp,2

0.265 13.998

Total 7.686 406.468

a TankCALC

b EPA / ICF International (1999)

c EIA Monthly Energy Review

d IOGCC Marginal Wells Report

e Consensus of Industrial Review Panel

f Expert Judgement

g EIA Annual Energy Review

h GRI / EPA (1996)

i Radian (1996)

j CAPP (1992)

k Adapted from the MMS GOADS by ICF (2005)

l BOEM

m API (1996)
A-208 Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2012

n EPA, AP 42 Compilation of Air Pollutant Emission Factors

o OGJ Petroleum Economics Issue

p EIA Petroleum Supply Annual, Volume 1

* Emissions are not actually 0, but too small to show at this level of precision.

† Asphalt Blowing emissions are the only significant vented emissions from the refining sector; other sources are too small to show at this level of precision.

NE: Not estimated for lack of data

Energy use CO2 emissions not estimated to avoid double counting with fossil fuel combustion

Table A-153: Summary of CO2 Emissions from Petroleum Systems (Gg)

Activity 1990 1995 2000 2007 2008 2009 2010 2011 2012

Production Field Operations 376 341 323 293 284 306 317 332 392

Pneumatic device venting 27 26 24 22 23 23 23 24 24

Tank venting 328 296 281 253 243 265 276 291 350

Misc. venting & fugitives 18 18 17 16 16 16 16 16 16

Wellhead fugitives 1 1 1 1 1 1 1 1 1

Refining 18 19 21 18 16 14 15 15 14

Asphalt Blowing 18 19 21 18 16 14 15 15 14

Total 394 360 344 311 300 320 332 347 406