Combustion of Fossil Fuel – A Global Impact

May 18, 2015

Environmental Enlightenment #184

My colleague, Jim Jacobs, a renowned environmental scientist with Environmental Bio-Systems of northern California, enlightened me on that every gallon of gasoline when burned generates 20 pounds of carbon dioxide (CO2) that is released to the atmosphere.

Gasoline is a complex mixture of over 500 hydrocarbons that may have between 5 to 12 carbons.  Given below are illustrations of three molecules of the gasoline family.

 

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Take propylbenzene for example:

9 carbons (C) and 12 hydrogens (H)
Thus: C9H12

Upon combustion, hydrocarbon molecules convert to carbon dioxide (CO2) and water (H2O)

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Every carbon atom engages two oxygens.

Every two hydrogen atoms capture one oxygen.

Thus, one propylbenzene molecule will become:

C9H12      9 CO2 +      6 H2O

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One (1) molecule of propylbenzene
  Converts to:
    Nine (9) molecules of Carbon Dioxide
      Plus
        Six (6) molecules of Water

Mass is amount of matter.

Atoms are little particles of matter.

Every atom has its own characteristic mass.

You can measure the atomic mass in any unit of your choice: be it gram, pound or kernels of olives.

For our purpose we select a system where hydrogen atom represents one (1) unit of mass.

In this system:

  • The mass of the hydrogen atom is 1
  • The mass of the carbon atom is (approx) 12
  • The mass of the oxygen atom is (approx) 16

The mass of the C9H12 molecule will be:

 

C9H12 Mass   =    9 x 12    +   12 x 1   =    120

The mass of a CO2 molecule will be:

 

CO2 Mass   =    1 x 12    +   2 x 16   =    44

We now see that

 

the combustion of 1 molecule of propylbenzene

 

 

that has 120 units of mass

 

 

 

yields

 

 

 

 

9 molecules of carbon dioxide

 

 

 

 

 

with a combined mass of 9 x 44  =  396 mass units.

 

 

 

 

 

 

The ratio is:

 

 

396 / 120    =   3.3

 

It means:

 

 

Burning of one (1) pound of propylbenzene generates three and three-tenths (3.3) pounds of carbon dioxide

One gallon of gasoline weighs (approx) 6.7 pounds.

If gasoline was all propylbenzene:

 

For every gallon of gasoline (6.7 pounds) combusted 
we would generate 3.3 x 6.7 = 22.1 pounds of CO2

 

Another fact to note is that all fossil fuel, be it petroleum, coal or natural gas, is hydrocarbons, and that in the burning of hydrocarbons we tie free oxygen to the products of the combustion.

In the above example, combustion of one molecule of propylbenzene (120 atomic mass units) ties 24 atoms of oxygen (having 16 atomic mass units each).

Thus a total of 24 x 16 = 384 atomic mass units of oxygen get tied up in the CO2 and H2O generated by the combustion.

The ratio is:
       384 / 120 = 3.2

We get that for every gallon of gasoline (6.7 pounds) combusted there’s 3.2 x 6.7 = 21.4 pounds of free oxygen eliminated from the air and engaged in bondage with water and carbon dioxide.

Nature can break down the CO2 and water back to their elemental components and release the captured oxygen to the atmosphere. HOWEVER, Nature never equipped itself to free up the oxygen at the rate that we are now tying it up.

One can therefore conclude that before the rest of the world starts mass driving of cars, building power plants and heating homes with gas it would behoove its more advanced societies to strive hard in the quest after non-hydrocarbon-based fuels.

As the old way is leading into cul de sac, we see global efforts accelerating to solve this fast-becoming acute problem of survival for the inhabitants of Earth.

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