Basic Units of Measurement and Conversions - Basic Mathematics for Water and Wastewater Operators - page 80

Therms of Natural Gas
Carbon dioxide emissions per therm are determined by multiplying heat content
times the carbon coefficient times the fraction oxidized times the ratio of the molec-
ular 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 average carbon coefficient of natural
gas is 14.47 kg carbon per mmBtu (USEPA, 2012b). 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 burn-
ing) are about 21 times more powerful than CO 2 in terms of their warming effect
on the atmosphere.
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.
Barrels of Oil Consumed
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, 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.
(5.80 mmBtu/barrel) × (20.31 kg C per mmBtu) × (44 g CO 2 per 12 g C) × (1 metric
ton/1000 kg) = 0.43 metric tons CO 2 per barrel.
Tanker Trucks Filled with Gasoline
Carbon dioxide emissions per barrel of gasoline are determined by multiplying the
heat content times the carbon dioxide coefficient times the fraction oxidized times
the ratio of the molecular weight of carbon dioxide to that of carbon (44/12). A barrel
equals 42 gallons. A typical gasoline tanker truck contains 8500 gallons. The aver-
age heat content of conventional motor gasoline is 0.125 mmBtu/gal, and the average
carbon coefficient of motor gasoline is 71.35 kg CO 2 (USEPA, 2012a). The fraction
oxidized to CO 2 is 100% (IPCC, 2006).