Calculations and References

This page describes the calculations used to convert greenhouse gas emission numbers into different types of equivalent units. Go to the equivalency calculator page for more information.

Electricity use (kilowatt-hours)

The Clean Energy Equivalencies Calculator uses the Emissions & Generation Resource Integrated Database (eGRID) U.S. annual non-baseload CO₂ output emission rate when converting reductions of kilowatt-hours into avoided units of carbon dioxide emissions.

The Clean Energy Equivalencies Calculator uses an eGRID (Emissions & Generation Resource Integrated Database) non-baseload national average emissions rate when converting kilowatt-hours into avoided units of carbon dioxide emissions.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

7.18 x 10^-4 metric tons CO₂ / kWh
(eGRID2007 Version 1.1, U.S. annual non-baseload CO₂ output emission rate, year 2005 data)

Note: Individual subregion non-baseload emissions rates are also available on the eGRID Web site.

Sources

(EPA 2009) eGRID2007 Version 1.1, U.S. annual non-baseload CO₂ output emission rate, year 2005 data U.S. Environmental Protection Agency, Washington, DC.

Passenger vehicles per year

Passenger vehicles are defined as 2-axle 4-tire vehicles, including passenger cars, vans, pickup trucks, and sport/utility vehicles.

In 2005, the weighted average combined fuel economy of cars and light trucks combined was 19.7 miles per gallon (FHWA 2006). The average vehicle miles traveled in 2005 was 11,856 miles per year.

In 2005, the ratio of carbon dioxide emissions to total emissions (including carbon dioxide, methane, and nitrous oxide, all expressed as carbon dioxide equivalents) for passenger vehicles was 0.971 (EPA 2007).

The amount of carbon dioxide emitted per gallon of motor gasoline burned is 8.81*10^-3 metric tons, as calculated in the "Gallons of gasoline consumed" section.

To determine annual GHG emissions per passenger vehicle, the following methodology was used: vehicle miles traveled (VMT) was divided by average gas mileage to determine gallons of gasoline consumed per vehicle per year. Gallons of gasoline consumed was multiplied by carbon dioxide per gallon of gasoline to determine carbon dioxide emitted per vehicle per year. Carbon dioxide emissions were then divided by the ratio of carbon dioxide emissions to total vehicle greenhouse gas emissions to account for vehicle methane and nitrous oxide emissions.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

8.81*10^-3 metric tons CO₂/gallon gasoline * 11,856 VMT _{car/truck average} * 1/19.7 miles per gallon _{car/truck average} * 1 CO₂, CH₄, and N₂O/0.971 CO₂ = 5.46 metric tons CO₂E /vehicle/year

Sources

EPA (2007). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2005. U.S. Environmental Protection Agency, Washington, DC. USEPA, Table 3-7 (p.3-9) (PDF) (59 pp, 1.47MB, About PDF) and Table A-108 (p.A-127) (PDF) (169 pp, 1.27MB, About PDF)
FHWA (2006). Highway Statistics 2005. Office of Highway Policy Information, Federal Highway Administration. Table VM-1.

Gallons of gasoline consumed

Average heat content of conventional motor gasoline is 5.22 million btu per barrel (EPA 2007). Average carbon coefficient of motor gasoline is 19.33 kg carbon per million btu (EPA 2007). Fraction oxidized to CO₂ is 100 percent (IPCC 2006).

Carbon dioxide emissions per barrel of gasoline were determined by multiplying heat content times the carbon coefficient time the fraction oxidized times the ratio of the molecular weight ratio of carbon dioxide to carbon (44/12). A barrel equals 42 gallons.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

5.22 mmbtu/barrel * 19.33 kg C/mmbtu * 1 barrel/42 gallons * 44 g CO₂/12 g C * 1 metric ton/1000 kg = 8.81*10^-3 metric tons CO₂/gallon

Sources

Therms of natural gas

Average heat content of natural gas is 0.1 mmbtus per therm (EPA 2007). Average carbon coefficient of natural gas is 14.47 kg carbon per million btu (EPA 2007). Fraction oxidized to CO₂ is 100 percent (IPCC 2006).

Carbon dioxide emissions per therm were determined by multiplying heat content times the carbon coefficient time the fraction oxidized times the ratio of the molecular weight ratio of carbon dioxide to carbon (44/12).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

0.1 mmbtu/1 therm * 14.47 kg C/mmbtu * 44 g CO₂/12 g C * 1 metric ton/1000 kg = 0.005 metric tons CO₂/therm

Sources

Barrels of oil consumed

Average heat content of crude oil is 5.80 million btu per barrel (EPA 2007). Average carbon coefficient of crude oil is 20.33 kg carbon per million btu (EPA 2007). Fraction oxidized is 100 percent (IPCC 2006).

Carbon dioxide emissions per barrel of crude oil were determined by multiplying heat content times the carbon coefficient times the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that of carbon (44/12).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

5.80 mmbtu/barrel * 20.33 kg C/mmbtu * 44 g CO₂/12 g C * 1 metric ton/1000 kg = 0.43 metric tons CO₂/barrel

Sources

Tanker trucks filled with gasoline

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

5.22 mmbtu/barrel * 19.33 kg C/mmbtu * 1 barrel/42 gallons * 44 g CO₂/12 g C * 1 metric ton/1000 kg = 8.81*10^-3 metric tons CO₂/gallon

8.81*10^-3 metric tons CO₂/gallon * 8,500 gallons/tanker truck = 74.88 metric tons CO₂/tanker truck

Sources

Home electricity use

In 2001, there were 107 million homes in the United States; of those, 73.7 million were single-family homes* (EIA, 2003). On average, each single-family home consumed 11,965 kWh of delivered electricity (EIA 2003). The national average carbon dioxide output rate for electricity in 2005 was 1,329 lbs CO₂ per megawatt-hour (EPA 2009).

Annual single-family home electricity consumption was multiplied by the carbon dioxide emission rate (per unit of electricity delivered) to determine annual carbon dioxide emissions per home.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

11,965 kWh per home * 1,329.35 lbs CO₂ per megawatt-hour delivered * 1 mWh/1000 kWh * 1 metric ton/2204.6 lb = 7.21 metric tons CO₂/home.

*A single-family home is defined in the U.S. Department of Energy’s Residential Energy Consumption Survey as follows: A housing unit, detached or attached, that provides living space for one home or family. Attached houses are considered single-family houses as long as they are not divided into more than one housing unit and they have independent outside entrance. A single-family house is contained within walls extending from the basement (or the ground floor, if there is no basement) to the roof. A mobile home with one or more rooms added is classified as a single-family home. Townhouses, rowhouses, and duplexes are considered single-family attached housing units, as long as there is no home living above another one within the walls extending from the basement to the roof to separate the units.

Sources

EIA (2003). A Look at Residential Energy Consumption in 2001. Table CE1-4c, Total Energy Consumption in U.S. Households by Type of Housing Unit, 2001, Physical Units of Total Consumption per Household, Fuels Used (PDF) (2 pp, 12K, About PDF).
EPA (2009). eGRID2007 Version 1.1. U.S. Environmental Protection Agency, Washington, DC.

Home energy use

In 2001, there were 107 million homes in the United States; of those, 73.7 million were single-family homes* (EIA, 2003). On average, each single-family home consumed 11,965 kWh of delivered electricity, 52,429 cubic feet of natural gas, 57.3 gallons of fuel oil, 46.6 gallons of liquid petroleum gas, and 2.6 gallons of kerosene. (EIA 2003).

The national average carbon dioxide output rate for electricity in 2005 was 1,329 lbs CO₂ per megawatt-hour (EPA 2009).

The average carbon dioxide coefficient of natural gas is 0.0546 kg CO₂ per cubic foot (EPA 2007). Fraction oxidized to CO₂ is 100 percent (IPCC 2006).

The average carbon dioxide coefficient of distillate fuel oil is 462.1 kg CO₂ per 42-gallon barrel (EPA 2007a). Fraction oxidized to CO₂ is 100 percent (IPCC 2006).

The average carbon dioxide coefficient of liquefied petroleum gases is 231.9 kg CO₂ per 42-gallon barrel (EPA 2007). Fraction oxidized is 100 percent (IPCC 2006).

The average carbon dioxide coefficient of kerosene is 410.0 kg CO₂ per 42-gallon barrel (EPA 2007). Fraction oxidized to CO₂ is 100 percent (IPCC 2006).

Total single-family home electricity, natural gas, distillate fuel oil, and liquefied petroleum gas consumption figures were converted from their various units to metric tons of CO₂ and added together to obtain total CO₂ emissions per home.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

1. Delivered electricity: 11,965 kWh per home * 1,329.35 lbs CO₂ per megawatt-hour delivered * 1 mWh/1000 kWh * 1 metric ton/2204.6 lb = 7.21 metric tons CO₂/home.

2. Natural gas: 52,429 cubic feet per home * 0.0546 kg CO₂/cubic foot * 1/1000 kg/metric ton = 2.86 metric tons CO₂/home

3. Fuel oil: 57.3 gallons per home * 1/42 barrels/gallon * 462.1 kg CO₂/barrel = 0.63 metric tons CO₂/home

4. Liquid petroleum gas: 46.6 gallons per home * 1/42 barrels/gallon * 231.9 kg CO₂/barrel = 0.26 metric tons CO₂/home

5. Kerosene: 2.6 gallons per home * 1/42 barrels/gallon * 410 kg CO₂/barrel = 0.03 metric tons CO₂/home

Total CO₂ emissions for energy use per single-family home: 7.21 metric tons CO₂ for electricity + 2.86 metric tons CO₂ for natural gas + 0.63 metric tons CO₂ for fuel oil + 0.26 metric tons CO₂ for liquid petroleum gas + 0.03 metric tons CO₂ for kerosene = 10.99 metric tons CO₂ per home per year.

Sources

EIA (2003). A Look at Residential Energy Consumption in 2001. Table CE1-4c, Total Energy Consumption in U.S. Households by Type of Housing Unit, 2001, Physical Units of Total Consumption per Household, Fuels Used (PDF) (2 pp, 12K, About PDF). Per-home averages were obtained by dividing the physical units of total consumption for each fuel used by the total number of single-family homes.
EPA (2009). eGRID2007 Version 1.1. U.S. Environmental Protection Agency, Washington, DC.
EPA (2007). Inventory of U.S. Greenhouse Gas Emissions and Sinks: Fast Facts 1990-2005. Conversion Factors to Energy Units (Heat Equivalents) Heat Contents and Carbon Content Coefficients of Various Fuel Types. U.S. Environmental Protection Agency, Washington, DC. USEPA #430-R-07-002 (PDF) (2 pp, 216K, About PDF).
IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change, Geneva, Switzerland.

Number of tree seedlings grown for 10 years

A medium growth coniferous tree, planted in an urban setting and allowed to grow for 10 years, sequesters 23.2 lbs of carbon. This estimate is based on the following assumptions:

The medium growth coniferous trees are raised in a nursery for one year until they become 1 inch in diameter at 4.5 feet above the ground (the size of tree purchased in a 15-gallon container).
The nursery-grown trees are then planted in a suburban/urban setting; the trees are not densely planted.
The calculation takes into account "survival factors" developed by U.S. DOE (1998). For example, after 5 years (one year in the nursery and 9 in the urban setting), the probability of survival is 68 percent; after 10 years, the probability declines to 59 percent. For each year, the sequestration rate (in lb per tree) is multiplied by the survival factor to yield a probability-weighted sequestration rate. These values are summed for the 10-year period, beginning from the time of planting, to derive the estimate of 23.2 lbs of carbon per tree.

Please note the following caveats to these assumptions:

Seedlings may require more than 1 year to reach 1 inch diameter; it may take 4-5 years or longer depending on species and conditions.
Average survival rates in urban areas are unknown, and the rates will vary significantly depending upon site conditions.
Carbon sequestration is dependent on growth rate, which varies by location and other conditions.

To convert to units of metric tons CO₂ per tree, we multiplied by the ratio of the molecular weight of carbon dioxide to that of carbon (44/12) and the ratio of metric tons per pound (1/2204.6).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

23.2 lbs C/tree * (44 units CO₂ / 12 units C) * 1 metric ton / 2204.6 lbs = 0.039 metric ton CO₂ per urban tree planted

Sources

U.S. DOE (1998). Method for Calculating Carbon Sequestration by Trees in Urban and Suburban Settings. Voluntary Reporting of Greenhouse Gases, U.S. Department of Energy, Energy Information Administration.

Acres of pine or fir forests storing carbon for one year

Growing forests store carbon. Through the process of photosynthesis, trees remove CO₂ from the atmosphere and store it as cellulose, lignin, and other compounds. The rate of accumulation is equal to growth minus removals (i.e., harvest for the production of paper and wood) minus decomposition. In most US forests, growth exceeds removals and decomposition, so there has been an overall increase in the amount of carbon stored nationally.

The estimate of the annual average rate of carbon accumulation is based on two studies, one on Douglas fir in the Pacific Northwest (Nabuurs and Mohren, 1995), and the other on slash pine in Florida (Shan et al. (2001)). These two studies represent commercially important species from different regions and with different rotation periods (i.e., time between planting and harvesting). The calculation addresses only aboveground carbon; although carbon accumulates in roots, leaf litter, and soils, these belowground carbon pools are not included.

For each of the two studies, the average annual rate accumulation is calculated as (a) the total carbon production (per acre) at the end of the rotation period divided by (b) the number of years in the period, as shown in the table below. Shan et al. (2001) reported total biomass production, rather than carbon production; the calculation assumes that carbon comprises 50 percent of biomass.

Tree/Plantation Type	Place	(a) Aboveground C Production During a Single Rotation (MT C/acre)	(b) Rotation Period (years)	(c) (=a/b) Average Annual C Accumulation (MT C/acre/yr)
Average value	*1.2*
Douglas fir (Pseudotsuga menziesii)	Pacific Northwest	136	100	1.4
Slash pine (Pinus elliottii)	Florida	17	17	1.0

The calculator uses the average of the two values from the studies, i.e., an annual rate of 1.2 metric tons of carbon per acre, which translates to 4.4 metric tons of carbon dioxide.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

((1.4 tons C accumulation / acre pine) + (1.0 tons C accumulation / acre fir)) 0.5 * 44 units CO₂/ 12 units C = 4.4 metric tons CO₂ / acre of pine or fir forests per year

Sources

Nabuurs, G.J., and G.M.J. Mohren. 1995. Modelling analysis of potential carbon sequestration in selected forest types. Canadian Journal of Forest Research 25(7):1157-1172.
Shan, J.P., L.A. Morris, and R.L. Hendrick. 2001. The effects of management on soil and plant carbon sequestration in slash pine plantations. Journal of Applied Ecology 38(5):932-941.

Acres of forest preserved from deforestation

In 2005, there were 25,815,000,000 metric tons of forest carbon (excluding soil organic carbon in forests) and 254,684,000 hectares of forested land (EPA 2007). There are 2.471 acres in one hectare. Thus the average carbon density of US forestland is 40.9 metric tons per acre.

For crop or pasture land, IPCC guidance on characterizing land use change suggests that an average value of aboveground dry biomass is 10 metric tons per hectare (IPCC/UNEP/OECD/IEA 1997). We assumed that the carbon content of dry biomass is 45 percent. Therefore, the carbon content of cropland was calculated to be 4.5 metric tons of carbon per hectare, or 1.8 metric tons per acre.

The change in carbon density from converting forested land to crop or pasture land would thus be 40.9 MT carbon/acre – 1.8 MT carbon/ acre, or 39.1 carbon MT/acre. To convert to a carbon dioxide basis, we multiplied by the ratio of the molecular weight of carbon dioxide to that of carbon (44/12), yielding a value of 122 MT CO₂/acre.

This method assumes that all of the forest biomass is oxidized during burning (i.e. none of the burned biomass remains as charcoal or ash).

Note: The conversion provided may be an underestimate due to the omission of soil C in the calculation. Forest soil C stocks will likely decline with conversion. If the forests exist on organic soils, conversion would cause C stocks to decline, unless they are converting to wetland agriculture. However, most US forests in the contiguous US are growing on mineral soils. In the case of mineral soils forests, soil C stocks could be replenished or even increased, depending on the starting stocks, how the agricultural lands are managed, and the time frame over which lands are managed.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

25,815,000,000 metric tons C/254684000 ha = 101.3 metric tons C/ha

(101.3 metric tons C/acre)/(2.471 acres per ha) = 40.9 metric tons C/acre

4.5 metric tons C biomass/ hectare * 1 hectare/ 2.47 acres = 1.8 metric tons C/acre of cropland

40.9 metric tons C/ acre forest - 1.8 metric ton CO₂/acre of cropland = 39.1 metric tons C/acre converted * 44 units CO₂/ 12 units C = 143.37 metric tons CO₂/ acre converted

Sources

EPA (2007). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2005. U.S. Environmental Protection Agency, Washington, DC. USEPA #430-R-07-002. Table A-189, Annex 3 (p. 220) (PDF) (169 pp, 1.27MB, About PDF).
IPCC/UNEP/OECD/IEA (1997). Revised 1996 IPCC Guidelines for National Greenhouse Inventories. Paris: Intergovernmental Panel on Climate Change, United Nations Environment Programme, Organization for Economic Cooperation and Development, International Energy Agency. Paris, France.

Propane cylinders used for home barbeques

Average heat content of liquefied petroleum gas is 21,591 btu per pound (EPA 2007). Average carbon coefficient of liquefied petroleum gases is 16.99 kg carbon per million btu (EPA 2007). Fraction oxidized is 100 percent (IPCC 2006).

Carbon dioxide emissions per pound of propane were determined by multiplying heat content times the carbon coefficient times the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that of carbon (44/12). Propane cylinders vary with respect to size - for the purpose of this equivalency calculation, a typical cylinder for home use was assumed to contain 18 pounds of propane.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

21,591 btu/pound * 1 mmbtu/10⁶ btu * 16.99 kg C/mmbtu * 44 g CO₂/12 g C * 18 pounds/1 canister * 1 metric ton/1000 kg = 0.024 metric tons CO₂/canister

Sources

Railcars of coal burned

Average heat content of coal in 2005 was 22.68 million btu per metric ton (EPA 2007). Average carbon coefficient of coal in 2005 was 25.34 kilograms carbon per million btu (EPA 2007). Fraction oxidized is 100 percent (IPCC 2006).

Carbon dioxide emissions per ton of coal were determined by multiplying heat content times the carbon coefficient times the fraction oxidized times the ratio of the molecular weight of carbon dioxide to that of carbon (44/12). The amount of coal in an average railcar was assumed to be 100.19 short tons, or 90.89 metric tons (Hancock 2001).

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

22.68 mmbtu/metric ton coal * 25.34 kg C/mmbtu * 44g CO₂/12g C * 90.89 metric tons coal/railcar * 1 metric ton/1000 kg = 191.5 metric tons CO₂/railcar

Sources

EPA (2007). Inventory of U.S. Greenhouse Gas Emissions and Sinks: Fast Facts 1990-2005. Conversion Factors to Energy Units (Heat Equivalents) Heat Contents and Carbon Content Coefficients of Various Fuel Types. U.S. Environmental Protection Agency, Washington, DC. USEPA #430-R-07-002 (PDF) (2 pp, 216K, About PDF).
Hancock (2001). Hancock, Kathleen and Sreekanth, Ande. Conversion of Weight of Freight to Number of Railcars. Transportation Research Board, Paper 01-2056, 2001.
IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change, Geneva, Switzerland.

Tons of waste recycled instead of landfilled

To develop the conversion factor for recycling rather than landfilling waste, emission factors from EPA's WAste Reduction Model (WARM) were used (EPA 2006). These emission factors were developed following a life-cycle assessment methodology using estimation techniques developed for national inventories of greenhouse gas (GHG) emissions. 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, is 0.79 MTCE per short ton. This factor was then converted to metric tons of carbon dioxide equivalent (MTCO₂E) by multiplying by 44/12, the molecular weight ratio of carbon dioxide to carbon.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

0.79 MTCE/ton * 44 g CO₂/12 g C = 2.90 metric tons CO₂E/ton of waste recycled instead of landfilled

Sources

EPA (2006). WAste Reduction Model (WARM). U.S. Environmental Protection Agency.
[note: click "view emission factors" at bottom of form to see recycling and landfilling emission factors]

Coal fired power plant for one year

In 2005 there were 2,134,520,641 tons of CO₂emitted from power plants whose primary source of fuel was coal (CAMD, 2005).

In 2005 there were a total of 417 power plants whose primary source of fuel was coal (CAMD, 2005).

Carbon dioxide emissions per power plant were calculated by dividing the number of power plants by the total emissions from power plants whose primary source of fuel was coal. The quotient was then converted from tons to metric tons.

Calculation

Note: Due to rounding, performing the calculations given in the equations below may not return the exact results shown.

2,134,520,641 tons of CO₂ * 1/417_{power plants}* 0.9072 metric tons / 1 short ton = 4,643,734 metric tons CO₂/power plant

Sources

CAMD (2007): EPA Clean Air Markets Division Data and Maps Web site.

Calculations and References

Electricity use (kilowatt-hours)

Calculation

Sources

Passenger vehicles per year

Calculation

Sources

Gallons of gasoline consumed

Calculation

Sources

Therms of natural gas

Calculation

Sources

Barrels of oil consumed

Calculation

Sources

Tanker trucks filled with gasoline

Calculation

Sources

Home electricity use

Calculation

Sources

Home energy use

Calculation

Sources

Number of tree seedlings grown for 10 years

Calculation

Sources

Acres of pine or fir forests storing carbon for one year

Calculation

Sources

Acres of forest preserved from deforestation

Calculation

Sources

Propane cylinders used for home barbeques

Calculation

Sources

Railcars of coal burned

Calculation

Sources

Tons of waste recycled instead of landfilled

Calculation

Sources

Coal fired power plant for one year

Calculation

Sources

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