Basic Units of Measurement and Conversions - Basic Mathematics for Water and Wastewater Operators - page 79

Emission Factor
7.0555 × 10 -4 metric tons CO 2 /kWh
Note: This calculation does not include any greenhouse gases other than CO 2 ,
and it does not include line losses.
Passenger Vehicles per Year
Passenger vehicles are defined as two-axle, four-tire vehicles, including passenger
cars, vans, pickup trucks, and sport/utility vehicles. In 2010, the weighted aver-
age combined fuel economy of cars and light trucks was 21.6 miles per gallon
(FHWA, 2010). The average number of vehicle miles traveled in 2010 was 11,489
miles per year. In 2010, the ratio of carbon dioxide emissions to total greenhouse
gas emissions (including carbon dioxide, methane, and nitrous oxide, all expressed
as carbon dioxide equivalents) for passenger vehicles was 0.985 (USEPA, 2013b).
The amount of carbon dioxide emitted per gallon of motor gasoline burned was
8.92 × 10 -3 metric tons.
To determine annual greenhouse gas emissions per passenger vehicle, the fol-
lowing methodology was used: The amount of vehicle miles traveled (VMT) was
divided by average gas mileage to determine gallons of gasoline consumed per
vehicle per year. The number of 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 car-
bon dioxide emissions to total vehicle greenhouse gas emissions to account for
vehicle methane and nitrous oxide emissions.
Calculation
Due to rounding, performing the calculations given in the equations below may not
return the exact results shown.
(8.92 × 10 -3 metric tons CO 2 per gal gasoline) × (11,489 VMT car/truck average) ×
(1/21.6 miles per gal car/truck average) × [(1 CO 2 , CH 4 , and N 2 O)/0.985 CO 2 ] = 4.8
metric tons CO 2 emissions per vehicle per year.
Gallons of Gasoline Consumed
To obt a i n the number of grams of CO 2 emitted per gallon of gasoline combusted,
the heat content of the fuel per gallon is multiplied by the kg CO 2 per heat content
of the fuel. The average heat content per gallon of gasoline is 0.125 mmBtu/gal and
the average emissions per heat content of gasoline is 71.35 kg CO 2 /mmBtu (USEPA,
2012b). The fraction oxidized to CO 2 is 100% (IPCC, 2006).
Calculation
Due to rounding, performing the calculations given in the equations below may not
return the exact results shown.
(0.125 mmBtu/gal) × (71.35 kg CO 2 per mmBtu) × (1 metric ton/1000 kg) = 8.92 ×
10 -3 metric tons CO 2 per gal of gasoline.