Individual Calculator Explained
Introduction
Calculating an individual’s or household’s impact on the climate is not an exact science. The calculations below, therefore, try to incorporate the most up-to-date references and data available. The most prudent assumptions have been made, and objective sources of information have been used for citation purposes. Where they are applicable, conservative estimates have been made.
The scope of the individual\household calculator addresses carbon dioxide (CO2) emissions resulting from household energy use, automobile use, and airplane travel.
Household Energy Use
The calculator determines home emissions resulting from electricity and heating use. The carbon footprint is estimated using one of two options.
Option 1: Household Size
This approach estimates emissions using average electricity and heating fuel usage based on the square footage of a residence. The averages are:
- 8.41 kilowatt-hours (kWh) per square foot per year and 12.86 pounds of CO2 per square foot per year for electricity;1
- 0.748 hundred cubic feet (CCF) per square foot per year and 8.52 pounds of CO2 per square foot per year for heating fuel.2
The emissions are converted into metric tons using the pounds to metric tons conversion factor of 2205 pounds per metric ton.
Option 2: Household Consumption
This approach estimates emissions using annual electricity and heating fuel consumption. The factors used are:
- 1.986 pounds of CO2 per kWh for electricity;3
- 11.394 pounds of CO2 per CCF for natural gas;4
- 12.718 pounds of CO2 per CCF for propane.5
The emissions are converted into metric tons using the pounds to metric tons conversion factor of 2205 pounds per metric ton.
Automobile Emissions
The calculator determines automobile emissions as a function of distance (miles traveled), fuel efficiency (miles per gallon) and an emissions factor specific to the type of fuel used by your vehicle.
The equation used to estimate CO2 emissions from auto travel is:
Metric tons of CO2 = [(miles/mpg)*emissions factor]/2205 .
The user enters fuel economy figures6 and fuel type used.7 The emission factors by fuel type are8:
- gasoline= 19.54 pounds of CO2 per gallon;
- diesel= 22.37 pounds of CO2 per gallon;
- b20= 17.89 pounds of CO2 per gallon; and
- e85= 2.93 pounds of CO2 per gallon
Airplane Emissions
The calculator determines airline emissions as a function of the miles traveled throughout the year. The formula used to estimate airplane CO2 emissions is:
Metric tons of CO2 = (1.41 pounds of CO2 per mile flown x miles)/2205.
The emission factor of 1.41 pounds of CO2 per mile9 flown is determined using aviation emission calculations from the United Kingdom’s Department of Environment and Rural Affairs (DEFRA) and the United Nations International Panel on Climate Change (IPCC). The IPCC source is used to take into account the Radiative Forcing Index of flying, which accounts for the greater impact an airplane has on the climate when it is traveling at flight altitude.
Endnotes
1 City of Aspen, Canary Tags Calculator, http://www.aspenzgreen.com/moreinfo.cfm?infoID=5
2 Ibid.
3 US Environmental Protection Agency, “eGRID2006 Version 2.1: Year 2004 Summary Tables (State Emissions),” April 2007, p.3, http://www.epa.gov/cleanenergy/energy-resources/egrid/index.html
4 City of Aspen, Canary Tags Calculator, http://www.aspenzgreen.com/moreinfo.cfm?infoID=5
5 Ibid.
6 Fuel economy information can be found at: http://www.fueleconomy.gov/feg/feg2000.htm
7 Fuel emission factors can be found at: http://www.fueleconomy.gov/
8 Emissions factors calculated from data in: (1) Energy Information Administration, Documentation for Emissions of Greenhouse Gases in the U.S. 2005, DOE/EIA-0638 (2005), October 2007, Tables 6-1, 6-4, and 6-5. (Non-biogenic carbon content and gross heat of combustion for motor gasoline and diesel (distillate fuel)). (2) U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Alternative Fuels & Advanced Vehicles Data Center, Fuel Properties web page (http://www.eere.energy.gov/afdc/fuels/properties.html). (Biodiesel gross heat of combustion). (3) Energy Information Administration, Annual Energy Review 2006, DOE/EIA-0384(2006), June 2007, Table A3, p. 361. (Gross heat of combustion for ethanol). (4) Stacy C. Davis and Susan W. Diegel, Transportation Energy Data Book, Edition 26, Oak Ridge National Laboratory, ORNL-6978, 2007, Table B.7 Tables 6.7 and B.4. (Density and gross heat of combustion of methanol.)
9 DEFRA, 2007, Passenger Transport Emission Factors, http://www.defra.gov.uk/environment/business/envrp/pdf/passenger-transport.pdf and IPCC, 1999, Aviation and the Global Atmosphere, http://www.grida.no/Climate/ipcc/aviation/index.htm.