Please note that these references are outdated and apply to the 2017 and 2018 version of emission factors only. See the Carbon References Page and Nitrogen References Page for current emission factor information.
| Direct transportation services | ||||||
| Mode | Name | Unit | Source | URL | Calculations | Notes |
| University fleet | Gasoline Fleet | kg NOx / Gallon | U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-93 (fuel consumption) and Table A-111 (NOx emissions) | https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (kt NOx * (1,000,000 kg/kt)) / (gallons) | Weighted average of gasoline passenger cars (96.5%) and gasoline light duty trucks (4.5%). |
| Diesel Fleet | kg NOx / Gallon | U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-93 (fuel consumption) and Table A-111 (NOx emissions) | https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (kt NOx * (1,000,000 kg/kt)) / (gallons) | Summed NOx emissions and fuel consumption for the following types of diesel: Passenger cars, light-duty trucks, buses, medium- and heavy-duty trucks. The resulting emissions factor was a weighted by fuel consumption and emissions. | |
| Natural Gas Fleet | kg NOx / MMBtu |
[1] GREET 1.5 - Transportation Fuel-Cycle Model. Volume 2: Appendics of Data and Results. Table BI-1 (NOx emission factors). 2] U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-94 (energy consumption) and Table A-99 (vehicle miles traveled for alternative fuel vehicles). |
https://www.anl.gov/energy-systems/publication/greet-15-transportation-f..., https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (g NOx/mi) * (1 kg/1000 g) / (MMBtu/mi) | Assumed passenger cars for emissions factors. Only included vehicle operation emissions. NOx emissions factor is an average of two near-term technologies for passenger cars: CNG bi-fuel and CNG dedicated (g/mi). Converted from g/mi to kg NOx/MMBtu using fuel economy in units MMBtu/mile. Fuel economy was calculated as the energy consumption of natural gas passenger cars divided by the vehicle miles traveled by light-duty cars (CNG ICE and CNG Bi-fuel). Used average emission factor across all years. | |
| E85 Fleet | kg NOx / Gallon | U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-93 (fuel consumption) and Table A-111 (NOx emissions) | https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (kt NOx * (1,000,000 kg/kt)) / (gallons) = kg NOx/gallon | Assumed to be equal to gasoline fleet emissions factor. | |
| B5 Fleet | kg NOx / Gallon | U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-93 (fuel consumption) and Table A-111 (NOx emissions) | https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (kt NOx * (1,000,000 kg/kt)) / (gallons) = kg NOx/gallon | Assumed to be equal to diesel fleet emissions factor. | |
| B20 Fleet | kg NOx / Gallon | U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-93 (fuel consumption) and Table A-111 (NOx emissions) | https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (kt NOx * (1,000,000 kg/kt)) / (gallons) = kg NOx/gallon | Assumed to be equal to diesel fleet emissions factor. | |
| B100 | kg NOx / Gallon | U.S. EPA. Inventory of U.S. Greenhouse Emissions and Sinks: 1990 - 2014. Released April 15, 2016. Annex 3, Section 3.1, Table A-93 (fuel consumption) and Table A-111 (NOx emissions) | https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-a... | (kt NOx * (1,000,000 kg/kt)) / (gallons) = kg NOx/gallon | Assumed to be equal to diesel fleet emissions factor. | |
| Hydrogen | kg NOx / MMBtu | GREET 1.5 - Transportation Fuel-Cycle Model. Volume 2: Appendics of Data and Results. Table BII-1 (NOx emission factors). | https://www.anl.gov/energy-systems/publication/greet-15-transportation-f... | n/a | Vehicle operation emissions from hydrogen vehicles are 0. | |
| Other Fleet Fuel | kg NOx / MMBtu | n/a | n/a | n/a | Customized by users. No data entry here. | |
| Commuting // Directly financed outsourced travel // Travel Abroad | ||||||
| Vehicle/mode | Unit | Source | URL | Calculations | Notes | |
| Faculty, staff, and student commuting | Automobile | kg NOx / Mile | [1] Gasoline fleet emissions factor (see above) and [2] U.S. Department of Transportation, Bureau of Transportation Statistics, National Transportation Statistics July 2013 (fuel efficiencies). |
https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/n... | (kg NOx/gal) / (miles/gal) | Gasoline fleet NOx emissions factor (kg NOx / gal) divided by an average annual fuel economy. Average fuel efficiency is from Table 4-11 and includes passenger cars, light trucks and motorcycles. |
| Carpool | kg NOx / Mile | Automobile commuting emissions factor (see above) | n/a | (Automobile kg NOx/mi) / (2 people per car) | Assumed 2 people per car. Calculated as gasoline automobile emissions factor divided by 2. | |
| Bus | kg NOx / Mile | [1] Diesel fleet emissions factor (see above) and [2] U.S. Department of Transportation, Bureau of Transportation Statistics, National Transportation Statistics July 2013 (fuel efficiencies). |
https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/n... | (kg NOx/gal) / (miles/gal) | Diesel fleet NOx emissions factor (kg NOx / gal) divided by an average annual fuel economy. Average fuel efficiency is from Table 4-11 for buses. | |
| Light Rail | kg NOx / Mile | [1] US EPA. Emissions & Generation Resource Integrated Database (eGRID) 2014. and [2] U.S. Department of Energy Trasportation Energy Data Book, Edition 32 (July 31, 2013), Chapter 9 Tables 9.10-9.12 and Appendix A Tables A.14-A.16. | https://www.epa.gov/energy/emissions-generation-resource-integrated-data..., http://cta.ornl.gov/data/index.shtml | (kg NOx/kWh) / (passenger-mile/kWh) | eGrid US average NOx emissions factors per kWh used for light rail electricity. Divided by average fuel efficiency (passenger-mi per kWh). Electricity use for electricity use by commuter from Appendix A tables. Passenger miles traveled from Chapter 9 tables. | |
| Commuter Rail | kg NOx / Mile | [1] Diesel fleet emissions factor (see above), [2] US EPA. Emissions & Generation Resource Integrated Database (eGRID) 2014. and [3] U.S. Department of Energy Trasportation Energy Data Book, Edition 32 (July 31, 2013), Chapter 9 Tables 9.10-9.12 and Appendix A Tables A.14-A.16. |
https://www.epa.gov/energy/emissions-generation-resource-integrated-data..., http://cta.ornl.gov/data/index.shtml | [ (electric kg NOx/kWh) / (passenger-mile/kWh) ] + [ (diesel kg NOx/gal) / (passenger-mile/gal) ] | Sum of electricity use and diesel for commuter rail. Diesel emission factor from fleet vehicle calculation above. eGrid US average NOx emissions factors per kWh used for commuter rail electricity. Divided by average fuel efficiency (passenger-mi per kWh). Electricity use for electricity use by commuter from Appendix A tables. Passenger miles traveled from Chapter 9 tables. | |
| Air travel | Faculty / Staff | kg NOx / Mile | [1] US EPA. 2014 National Emissions Inventory (NEI) Data (US total mobile aircraft NOx emissions). [2] US Bureau of Transportation Statistics. Table I-40: US Passenger-Miles (aircraft passenger-miles). |
https://www.epa.gov/air-emissions-inventories/2014-national-emissions-in..., https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/n... | [(ton NOx)*(2000 lb/ton)*(0.453592 kg/lb)] / (passenger-miles) | Calculated NOx emissions factor for years with US total NOx aircraft emissions factors available from NEI (2008, 2011, 2014) and took an average. NOx emissions including landing and take-off. Passenger miles include all air carrier, certified, domestic, and all services. Used average emission factor across all years. |
| Students | kg NOx / Mile | Air travel emissions factor (see above) | n/a | n/a | Assumed to be equal to air travel emissions factor | |
| Other | Train | kg NOx / Mile | [1] Diesel fleet emissions factor (see above), [2] Distillate oil heating value (see CCC), [3] Train fuel efficiency (see CCC) |
n/a | (kg NOx/gal) / (MMBtu/gal) * (MMBtu/mi) | Diesel fleet emissions factor (kg NOx/gal) was converted to kg NOx/mi using distillate oil heating value from CCC (MMBtu/gal from EF_Heating values tab) and fuel efficiency for trains from CCC (MMBtu/mi from EF_Transportation tab). |
| Taxi / Ferry / Rental Car | kg NOx / Mile | Automobile commuting emissions factor (see above) | n/a | (Automobile kg NOx/mi) | Assumed to be equal to automobile commuting emissions factor | |
| Public Bus | kg NOx / Mile | Diesel bus commuting emissions factor (see above) | n/a | (Bus kg NOx/mi) | Assumed to be equal to diesel bus commuting emissions factor | |
| Charter bus - Diesel | kg NOx / Mile | |||||
| Charter bus - CNG | kg NOx / Mile | |||||
| Charter bus - Other | kg NOx / Mile | n/a | n/a | n/a | Customized by users. No data entry here. | |
| Alternative Fuel Bus | kg NOx / Mile | n/a | n/a | n/a | Assumed to be 0. | |
| Personal Mileage Reimbursement | kg NOx / Mile | Automobile commuting emissions factor (see above) | n/a | (Automobile kg NOx/mi) | Assumed to be equal to automobile commuting emissions factor | |
| Air travel | Air Travel | kg NOx / Mile | Air travel emissions factor (see above) | n/a | n/a | Assumed to be equal to air travel emissions factor |