How Your Pollution is Calculated
This calculator requires a minimum of information from you because it relies on state and national averages. Here are the averages and conversion rates used.
Your Home
First, total energy use (in million Btu) for different housing types (in million Btu) is taken from the U.S. Energy Information Administration's 2001 Residential Energy Consumption Survey.
Second, the calculator assumes that total energy use is from electricity and natural gas only, with the ratio between the two energy sources calculated, for different housing types, from the Energy Information Administration's 2001 Residential Energy Consumption Survey.
For total electricity use, the resulting estimate (kWh) is multiplied by 1.072 to account for transmission losses.
Corrected total electrical use is then converted to CO2 based on regional average CO2 emissions per kWh, with data from the U.S Energy Information Administration.
For natural gas use, the estimate is converted to CO2 emissions based on data from the U.S. Energy Information Administration.
Your Driving
Gas mileage data are from the U.S. Environmental Protection Agency and the U.S. Energy Information Administration.
The average U.S. vehicle is driven 11,900 miles per year according to the Energy Information Administration.
Gallons are converted to CO2 using 25.3371 lbs CO2/gallon gas - 19.2898 lbs of CO2/gallon in direct emissions and 6.0473 lbs of CO2/gallon in upstream CO2 emissions - from the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model.
Your Flying
We assume that each short domestic, cross-country and overseas round-trip is 1200, 4000 and 8000 miles, respectively.
A domestic flight originating in the U.S. averages approximately 42 passenger-miles per gallon and international flights average 21 passenger-miles per gallon, according to the Bureau of Transportation Statistics.
Burning a gallon of jet fuel produces 21.1 lbs of CO2 (U.S. Department of Energy and the Energy Information Administration, Instructions for Form EIA 1605B, Voluntary Reporting of Greenhouse Gas Emissions, Appendix B). The result is that each domestic passenger-mile creates about half a pound of CO2 and each international passenger-mile creates one pound of CO2. However, the Climate Neutral Network estimates that non-CO2 greenhouse gas emissions from air travel are at least as significant as the CO2 impacts (doubling the emissions as expressed in CO2-equivalents) and upstream processes add an additional 8 percent, bringing the total to 1.1 lbs. of CO2-equivalent emissions per passenger-mile traveled domestically and 2.1 pounds of CO2-equivalent emissions per passenger-mile internationally.
Your Comparisons
Calculations from housing, driving and flying are coverted from pounds to metric tons (2204.6 lbs = 1 metric ton).
The conversion of tons of carbon to football fields of trees is done by assuming one ton CO2 equals all the rainforest trees in an area the size of 0.12 football fields (in the Brazilian Amazon), or 8 Mg C of roundwood per hectare (Asner, GP, DE Knapp, EN Broadbent, PJC Oliveira, M Keller & JN Silva. 2005. Selective logging in the Brazilian Amazon. Science 310: 480-482).
According to the U.S. Environmental Protection Agency's latest inventory [PDF] of national greenhouse gas emissions, CO2 emissions from residential energy use averaged 4.0 tons CO2 per person and personal vehicle use accounted for 3.8 tons CO2 per person in 2005, assuming a U.S. population of 300 million Americans. According to the Bureau of Transportation Statistics' data for jet fuel consumed in 2005 and assuming a U.S. population of 300 million, aviation was responsible for approximately 1.64 tons CO2-equivalents per person in 2005. In all, emissions from residential sector energy use, household vehicles and equipment, and commercial aviation is 9.44 metric tons CO2-equivalents/year/person.
According to the U.S. Environmental Protection Agency's latest inventory [PDF] of national greenhouse gas emissions, if emissions from all commercial and industrial activities were taken into account, the per capita CO2-equivalent emissions in the United States would be about 24.2 metric tons/person, assuming a U.S. population of 300 million Americans.
Sources
Total energy use (in million Btu) for different housing types (in million Btu) is from U.S. Energy Information Administration's 2001 Residential Energy Consumption Survey: Household Energy Consumption and Expenditures Tables, Table CE1-6.2u "Total Energy Consumption and Expenditures by Square Feet and Usage Indicators, 2001".
Energy Information Administration's 2001 Residential Energy Consumption Survey: Household Energy Consumption and Expenditures Tables, Table CE1-4c "Total Energy Consumption in U.S. Households by Type of Housing Unit, 2001".
Multiplication by 1.072 to account for transmission losses, based on 1995 data from the U.S. Climate Change Technology Program [PDF].
Conversion to CO2 based on data from the U.S Energy Information Administration's March 2002 Updated State-and Regional-level Greenhouse Gas Emission Factors for Electricity (for the U.S.) and from the Government of Canada.
Estimated natural gas use conversion to CO2 emissions based on data from the U.S. Energy Information Administration's Instructions for Form EIA 1605B, Voluntary Reporting of Greenhouse Gas Emissions, Appendix B. (Natural gas = 12.0593 lbs. of CO2/CCF).
Gas mileage data from U.S. Environmental Protection Agency and U.S. Energy Information Administration's Household Vehicles Energy Use: Latest and Trends, Table A1: U.S. Number of Vehicles, Vehicle-Miles, Motor Fuel Consumption and Expenditures, 2001.
Average mileage of 11,900 from Energy Information Administration - Monthly Energy Review - February 2001, using the average of car miles driven and SUV miles driven.
Gasoline to CO2 conversion figures from Wang, M.Q. GREET 1.5a Spreadsheet Model. Argonne, IL: Argonne National Laboratory. http://www.transportation.anl.gov/software/GREET/
According to Transportation, Energy, and the Environment, Section A - U.S. Energy Consumption and Transportation Sector Energy Consumption, Table 4-21, a domestic or international trip originating in the U.S. averages 33.4 passenger miles per gallon.
The Bonneville Environmental Foundation and the Climate Neutral Network have agreed that the appropriate approach is to double the 0.63 lbs. of CO2, with a result of 1.26 lbs. of total CO2 equivalent per passenger mile (CO2 + non-CO2 greenhouse gasses).