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Ground Travel Terms Explained...

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Gasoline is derived from petroleum and is primarily used as fuel for internal combustion engines. It is also used a solvent, mainly to dilute paints. The bulk of gasoline is made up of hydrocarbons, with between 4 and 12 carbon atoms per molecule. It is this carbon that combines with oxygen during combustion, thus forming carbon dioxide, a gas that can trap heat in the earth's atmosphere. A gallon of gasoline contains about 85.5% carbon, which weighs a bit over 5.2 lbs. When combined with oxygen, it weighs more, and the 5.2 lbs of carbon turns into 19.37 lbs of CO2.

The CO2 emission factor of gasoline is 19.37 lbs per gallon, or 70.88 kgCO2 per MMBtu.

Note: In Florida, retail gasoline may contain up to 10% ethanol. Though ethanol has a lower carbon impact, per volume, than gasoline, for the purposes of this calculator, the ethanol component was deemed negligible and not factored into the gasoline CO2 emission factor.


Diesel is derived from petroleum and a variety of other sources. Diesel derived from crude oil is heavier than gasoline, often containing between 8 and 21 carbon atoms per molecule. Because it delivers more energy per gallon, it produces more carbon dioxide, but since the vehicle can go farther on that gallon, on a per mile basis it is more carbon efficient than gasoline. The high energy content also lends itself to heavy duty applications, and diesel is typically found in work equipment such as trucks, bulldozers, trains and cargo ships.

The CO2 emission factor of diesel is 22.23 lbs per gallon, or 73.51 kgCO2 per MMBtu.


Bio-diesel is produced from a natural sources, such vegetable oil or animal fat, and is used as a substitute for conventional diesel. Bio-diesel is typically made by chemically reacting lipids, the structural parts of cell membranes, which are found oils, animal fats and waxes, with an alcohol. Bio-diesel can be used alone, or blended with conventional diesel, which is actually more common.

The blend ratio is indicated by use of a B factor, where the B stands for the amount of bio blended into a conventional hydrocarbon-based diesel. B100, for example, stands for 100% bio-diesel, B20 indicates 20% bio-diesel. Though the emission factor of the bio-portion of bio-diesel depends on the type of bio and how it was processed among others, bio-diesel typically contributes to a lower carbon footprint overall.

As B20 is a very popular blend, it was used for this calculator, with a CO2 emission factor of 17.97 lbs per gallon, or 59.44 kg CO2 per MMBtu.


CNG stands for Compressed Natural Gas, and is a growing alternative fuel source for cars, trucks and buses. Consisting of mostly methane (CH4), it is produced and recovered alongside oil production, from coal beds, and frequently from landfills. To make use of it in vehicles, the natural gas is compressed and stored in a tank. A clean burning fuel, CNG delivers approximately the same energy as gasoline, but often with 20 to 25% fewer greenhouse gas emissions, making it attractive to users who want to lower their carbon footprint. CNG does require a conversion to run in a conventional gasoline or diesel engine, but popular vehicle manufacturers are adding dedicated CNG vehicles to their products, and currently, around 10 millions vehicles worldwide run on compressed natural gas.

CNG is sold in gasoline gallon equivalents (it normally is a gas) and has a CO2 emission factor of 15.2 lbs per gallon equivalent, or 53.06 kgCO2 per MMBtu.

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