Geoscience Reference
In-Depth Information
1.7.2.1 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.
1.7.3 g
allons
oF
g
asoline
C
onsumed
To obtain 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/gallon 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).
1.7.3.1 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.
1.7.4 t
herms
oF
n
atural
g
as
Carbon dioxide emissions per therm are 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 average heat content of natural gas is 0.1 mmbtu per therm, and the aver-
age carbon coefficient of natural gas is 14.47 kg carbon per mmbtu (USEPA, 2013a). The fraction
oxidized to CO
2
is 100% (IPCC, 2006).
Note:
When using this equivalency, please keep in mind that it represents the CO
2
equivalency
for natural gas burned as a fuel, not natural gas released to the atmosphere. Direct methane
emissions released to the atmosphere (without burning) are about 21 times more powerful
than CO
2
in terms of their warming effect on the atmosphere.
1.7.4.1 Calculation
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 per mmbtu) × (44 g CO
2
per 12 g C)
× (1 metric ton/1000 kg)
= 0.005 metric tons CO
2
per therm.
1.7.5 b
arrels
oF
o
il
C
onsumed
Carbon dioxide emissions per barrel of crude oil are 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 average heat content of crude oil is 5.80 mmbtu per barrel,
and the average carbon coefficient of crude oil is 20.31 kg carbon per mmbtu (USEPA, 2013a). The
fraction oxidized to CO
2
is 100% (IPCC, 2006).
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