Carbon Calculator Assumptions and Sources
Click the categories below to be taken directly to the assumptions and sources for the each type of calculation.
- Fuel Oil
- Natural Gas
- Vehicle Travel
- Airplane Travel
- Food Consumption
- Trees’ Carbon Sequestration
The average annual electricity consumption for a U.S. residential utility customer was 10,896 kWh, an average of 908 kilowatt-hours (kWh) per month. U.S. Energy Information Administration, Table 5: Residential Average Monthly Bill by Census Division, and State, available at http://www.eia.doe.gov/tools/faqs/faq.cfm?id=97&t=3. On average, electricity sources emit 1.341 pounds (lbs) of carbon dioxide (CO2) per kWh. U.S. Energy Information Administration (U.S. Department of Energy and U.S. Environmental Protection Agency), Carbon Dioxide Emissions from the Generation of Electric Power in the United States, 2000, available at http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2report.html.
On average, each single-family home consumed 58.0 gallons of fuel oil a month. U.S. Environmental Protection Agency, Calculations and References: Home Energy Use, available at http://www.epa.gov/cleanenergy/energy-resources/refs.html. The average carbon dioxide coefficient of distillate fuel oil is 429.61 kg CO2 per 42-gallon barrel (EPA 2010b). U.S. Environmental Protection Agency, Calculations and References: Home Energy Use, available at http://www.epa.gov/cleanenergy/energy-resources/refs.html. This means it is it is 10.228809 kgs of CO2 per gallon and using 1 kilogram = 2.20462262 pounds, this is approximately 22.55 pounds of CO2 per gallon of oil.
On average, each single-family home consumed 47,453 cubic feet of natural gas. U.S. Environmental Protection Agency, Calculations and References: Home Heat, available at http://www.epa.gov/cleanenergy/energy-resources/refs.html. Using the conversion of 1.027 therms = 1 cubic foot. The average single-family home uses 48,734 therms a year. The U.S. EPA estimates that 0.005 metric tons CO2 are emitted per therms of natural gas burned.
Using the conversion of 1 metric ton per 2204.62262 pounds, this equals approximately 2.268 pounds per therm burned. U.S. Environmental Protection Agency, Calculations and References: Therms of Natural Gas, available at http://www.epa.gov/cleanenergy/energy-resources/refs.html.
The average passenger car gets 27.5 miles per gallon and the average light truck gets 23.5 mpg. Research and Innovative Technology Administration: Bureau of Transportation Statistics, Table 4-23: Average Fuel Efficiency of U.S. Passenger Cars and Light Trucks, available at http://www.bts.gov/publications/national_transportation_statistics/html/table_04_23.html. The number of miles driven per year is assumed to be 12,000 miles for all passenger vehicles. This number is based on several sources. Calculations from EPA’s MOBILE6 model show an average annual mileage of roughly 10,500 miles per year for passenger cars and over 12,400 miles per year for light trucks across all vehicles in the fleet. U.S. Environmental Protection Agency, Emission Facts: Greenhouse Gas Emissions from a Typical Passenger Vehicle, 2005, available at http://www.epa.gov/oms/climate/420f05004.htm. The U.S. Energy Information Administration estimates 17.68 pounds of CO2 are emitted per gallon of gas and 22.38 lbs of CO2 per gallon of diesel. U.S. Energy Information Administration, Frequently Asked Questions, available at http://www.eia.doe.gov/tools/faqs/faq.cfm?id=307&t=9.
On average, Americans fly 17.2 hours per year. We approximated this to be 7,500 miles a year with 17.2 hours at 500 mph = 8,600 miles with some miles subtracted for ascending and descending time. Major U.S. airlines average about 64 mpg. Scott McCartney, A Prius with Wings vs a Guzzler in the Clouds, Wall Street Journal, 08/12/2010, available at http://online.wsj.com/article/SB10001424052748704901104575423261677748380.html, which sources Department of Transportation data for 2009. The Energy Information Administration determined that burning jet fuel generates 9.57 kilograms of CO2 per gallon. Using the conversion of 1 kg = 2.20463363 pounds, this is 21.098 pounds of CO2 per gallon of jet fuel. Energy Information Administration, Voluntary Reporting of Greenhouse Gases Program Fuel Emission Coefficients Table 2 (2011), available at http://www.eia.doe.gov/oiaf/1605/coefficients.html#tbl2.
It is estimated that the average American eats 195 pounds of meat a year: 108.269 lbs of red meat; 72.640 lbs of poultry; 15.965 lbs fish and shell fish. U.S. Department of Agriculture: Economic Research Service, U.S. per capita Food Availability: Total Meat, available at http://www.ers.usda.gov/Data/FoodConsumption/app/reports/displayCommodities.aspx?reportName=Total meat&id=38#startForm. As this is a complex topic not only for CO2 equivalent calculating, for more information on U.S. food consumption, you can visit http://www.ers.usda.gov/data/foodconsumption/ or http://www.usda.gov/factbook/chapter2.htm. To calculate the CO2 equivalent (CO2e) of American’s diet, we used 14.8 pounds of CO2e per pound of beef; 3.98 lbs of CO2e per pound for pork; and 1.1 lbs of CO2e per pound for chicken; and 1 pound of CO2e per pound for fish. As this is a hard number to calculate, we used several resources including, but not limited to, Nathan Fiala, The Greenhouse Hamburger, Scientific American, February 2009 (72 – 75), available at http://www.scientificamerican.com/article.cfm?id=the-greenhouse-hamburger or http://vegetarian.procon.org/sourcefiles/the_greenhouse_hamburger.pdf, which sourced Henning Steinfeld: Food and Agriculture Organization of the United Nations, Livestock’s Long Shadow, 2006, available at http://www.fao.org/docrep/010/a0701e/a0701e00.HTM and ftp://ftp.fao.org/docrep/fao/010/a0701e/A0701E00.pdf.
In 2009, the per capita generation of waste was 4.34 pounds per person per day and total waste generation was 243.0 million tons. U.S. Environmental Protection Agency, Municipal Waste, available at http://www.epa.gov/epawaste/nonhaz/municipal/index.htm and U.S. Environmental Protection Agency, Waste Facts, available at http://www.epa.gov/epawaste/facts-text.htm#chart1. However, EPA estimates that 1.46 lbs per day are recovered for recycling. U.S. Environmental Protection Agency, Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2009, available at http://www.epa.gov/waste/nonhaz/municipal/pubs/msw2009-fs.pdf. This means the average American produces – after recycling – 2.88 lbs of waste a day, 1051.2 lbs a year, and 87.6 lbs per month. Each pound of trash thrown away will emit approximately 0.94 pounds of CO2e in the form of methane. U.S. Environmental Protection Agency, Climate Change Emissions, available at http://www.epa.gov/climatechange/emissions/ind_home.html.
The Environmental Protection Agency estimates that Americans recycle 1.46 pounds each day or 532.9 lbs a year and 44.41 lbs each month. U.S. Environmental Protection Agency, Municipal Solid Waste Generation, Recycling, and Disposal in the United States: facts and Figures for 2009, available at http://www.epa.gov/waste/nonhaz/municipal/pubs/msw2009-fs.pdf. According to WARM, the net emission reduction from recycling mixed recyclables (e.g., paper, metals, plastics), compared to a baseline in which the materials are landfilled 2.87 metric tons CO2e per short ton of waste recycled instead of landfilled. U.S. Environmental Protection Agency, Calculations and References: Tons of Waste Recycled instead of Landfilled, available at http://www.epa.gov/cleanenergy/energy-resources/refs.html. Using the savings of 2.87 metric tons of CO2e per 2,000 pounds of trash recycled (1 short ton = 2,000 pounds) or 0.001435 metric tons of CO2e per pound of recycled material. Then to produce the number of pounds of CO2e produced per pound of waste, I used 1 pound = 0.00045359237 metric tons determining that 0.3164 lbs of CO2e are save are saved per 1 lbs of trash recycled instead of landfilled. U.S. Environmental Protection Agency, Calculations and References: Tons of Waste Recycled instead of Landfilled, available at http://www.epa.gov/cleanenergy/energy-resources/refs.html using U.S. Environmental Protection Agency, WARM (2010), available at Waste Reduction Model (WARM). U.S. Environmental Protection Agency. As trash produces 0.94 pounds of CO2e per pound, we subtracted 0.3164 lbs showing that though it is better to recycle, it still produces 0.6236 pounds of CO2e per pound of recycled material.
Trees’ Carbon Sequestration
The first step in determining how much carbon is sequestered by a single tree is to convert carbon to carbon dioxide (CO2) or carbon dioxide equivalent (CO2e). For our calculations, we used the common conversion of:
1 ton of carbon = 3.666 tons of CO2
This represents the weight of carbon dioxide (44) divided by the atomic mass of carbon (12). Next, it is estimated that one acre of trees stores 50.8 metric tons of carbon, so…
50.8 metric tons of carbon X 3.666 tons of CO2 = ~186 metric tons of CO2 per acre of forest
Since we don’t use metric tons as a common measurement in the U.S., we next need to convert tons to pounds:
1 metric ton = 2204.62262 pounds
186 metric tons X 2204.62262 pounds = ~410,060 pounds of CO2 sequestered per acre of trees
American Forests has estimated that our tree planting projects average 450 trees per acre, which leaves us with one final calculation:
410060 pounds of CO2/450 trees per acre = ~911 pounds of CO2 sequestered per tree planted
As you may be able to surmise from the above, to get this calculation, we did need to make a few assumptions. For instance, we choose 55 years as the age for estimating carbon sequestration and storage, and we started with the U.S. Forest Service’s averages for carbon stored by trees (58.8 tons per acre) and made slight alterations for significant outliners, which gave us 50.8 metric tons per acre. Additional sources include, the United States Department of Agriculture: Forest Service, Methods for Calculating Forest Ecosystem and harvest Carbon with Standard Estimates for Forest Types of the United States, 2006, available at http://www.treesearch.fs.fed.us/pubs/22954. We also utilized United States Department of Agriculture: Forest Service, Carbon Storage and Accumulation in United States Forest Ecosystems, 1992, available at http://www.nrs.fs.fed.us/pubs/gtr/gtr_wo059.pdf.