How can emissions outweigh fuel?

Question

So, epa.gov says that, based on the annual passenger car mileage of 12,500 miles & fuel economy of 21.5 mpg, we release 11,450 pound of carbon dioxide.

So, let's estimate 585 gallons of gas. At 6.2 pounds per gallon, that's 3650 pounds of fuel.

So... how can 3650 pounds of fuel turn into 11,450 pounds of carbon dioxide... plus 575 pounds of carbon monoxide, 75 pounds of hydrocarbons, 40 pounds of oxides of nitrogen... in other words, over 12,000 pounds in emissions?

Where does 75% of the mass come from? Is it pulled out of the atmosphere? If so, then what's the big deal? It was already in the atmosphere in the first place. I'm definitely environmentally conscious, but am wary of the statistics spat out at me by some of the websites I visit.

Answer 1

IF YOU LIVED UP IN THE ATMOSPHERE AT 1000 FEET AND NOT NEAR ANY LAND AND COULD BREATHE THE ICE COLD THINNED AIR, YOU WOULD'NT SMELL ANYTHING FROM BELOW THE FIRST 100 FEET. BECAUSE IT ALL DECIPATES, LIKE HAVING A FIRE WITH BLACK SMOKE FROM GROUND LEVEL YOU ACTUALLY WATCH IT WITH YOUR EYES DECIPATE. LIKE ALL GASES, CARBONS, EXHAUST,ETC.

Answer 2

The gasoline doesn't contain much oxygen.  It is primarily carbon and hydrogen.  A carbon atom weighs 12 times more than a hydrogen atom, and there are roughly 1.5 times as many hydrogen atoms as carbon atoms, so gasoline is about

100% * 12 / (12 + 1.5) = 89%

carbon.  Carbon dioxide is one carbon atom (12 amu) and 2 oxygen atoms (16 amu each), so carbon dioxide is

100% * 12 / (12+32) = 27%

carbon, and about 73% oxygen.  Using the values you have provided above, the

3650 lbs * 0.89 = 3250 lbs

of carbon in fuel should become

3250 lbs / 0.27 = 12,000 lbs

of carbon dioxide.  Of course, it doesn't all become CO2.  Some of it becomes CO.  But that's how there's more mass in the products than in the gasoline, you need to include the mass of the oxygen which comes from the air.

And as another application, think about a rocket.  If you are using kerosene to fuel a scram jet and getting oxygen from the atmosphere, you might only need 10,000 lbs of fuel.  But, if you are in space (no atmosphere), you also need to carry around about 30,000 lbs of LOX.

Answer 3

Problem is, the oxygen from the air is combined during combustion into CO, CO2, NO, NOx, and whatever else shows up on your emmissions test. Sure, O2 is safe. But CO isn't.