Vehicle CO2 Emissions
Overview
According to the "Emissions of Greenhouse Gases in the United States 2006" prepared by the Energy Information Administration (EIA), the transportation sector is the largest contributor to greenhouse gas emissions in the United States. This sector accounted for more than 32% of the 5,825,500,000 metric tons of energy-related carbon dioxide emitted by US in 2006. This is a 23% increase over 1990 total carbon dioxide CO2 emissions from the transportation sector.
The combustion of motor gasoline in the US accounts for 60%, or 1,186,200,000 metric tons, of the total transportation energy-related CO2 emissions. In other words, the carbon dioxide coming out our tailpipes each year is approaching the total amount of ALL the greenhouse gases emitted annually by Canada, Mexico, and Australia combined.
Vehicle ratings in Miles Per Gallon
The mileage conversions used in the NETZERO calculator are based on data collected each year by the US Department of Energy (DOE) and the US Environmental Protection Agency (EPA).
Calculating Metric Tons of CO2 from the combustion of gasoline
To calculate the emissions using our NETZERO vehicle calculator, we have to make several assumptions related to the conversion of 1 gallon of motor gasoline into pounds of CO2 emitted:
- Gasoline Weight - Although there are variations in weight due to temperature and actual chemical composition, we assume for the NETZERO calculator that the weight of a gallon of standard motor gasoline is 6.25 pounds.
- Gasoline Composition - The calculator also assumes that 100% of our theoretical gallon of motor gasoline is octane with 8 carbon atoms and 18 hydrogen atoms. For the NETZERO calculator, the atomic weight is rounded down from 114.22 grams per mole (8 carbon x 12.0107 g/mol) + (18 hydrogen x 1.00794 g/mol) to 114 g/mol.
- Weight of Carbon Dioxide - The calculator is also uses an atomic weight of 44.0095 for carbon dioxide (1 Carbon x 12.0107 g/mol) + ( 2 Oxygen x 15.9994) rounded down to 44 g/mol.
- Gasoline Combustion - The calculator also assumes a 100% combustion of the motor gasoline. A 100% combustion of each molecule of motor gasoline (100% octane) will yield 8 molecules of CO2 having a cumulative atomic weight of 352 g/mol (8 CO2 molecules x 44 g/mol.)
Now that we have: a) the weight of a gallon of gasoline (6.25 lbs.); b) its composition (100% Octane) and atomic weight (114/g/mol); c) the atomic weight of carbon dioxide (44g/mol), and; d) an assumption of 100% combustion, we can establish a conversion factor that we use to convert our theoretical gallon of standard motor gasoline directly into lbs. of CO2:
6.25 lbs. per gallon of gasoline x (352/114) x 100% combustion rate = 19.29812 lbs. of CO2 from 1 gallon of motor gasoline (rounded up to 19.3 lbs).
To get to total CO2, the calculator multiplies the total number of gallons combusted x 19.3 lbs. of CO2 per gallon of gasoline = Total Lbs. of CO2.
The international reporting standard for CO2 emissions in always Metric Tons. We can finish calculation in total Metric Tons (MT) of CO2, by dividing the total number of lbs. of CO2 from our last calculation by 2,204.62 lbs. per MT.
