Carbon Footprint Calculators Make No Sense

According to Carbon Calculators a 5-hour flight produces the following TONS of carbon per person:

Green.yahoo.com 2.0 Tons p/person (20 times the weight of the fuel)

CarbonNeutral.com 0.5 Tons p/person (2.5 times the weight of the fuel)

ZeroFootPrint.com 2.71 Tons p/ person (24 times the weight of the fuel)

CarbonFootPrint.com .496 Tons p/person (2.5 times the weight of the fuel)

How can this possibly be? Certainly the vast majority of the fuel is converted to energy. How is it possible that the jet fuel produces many more times as much carbon as the weight of the fuel itself? Never mind the question as to why every carbon calculator gives you a wildly different answer.

What to check my calculations? See Carbon Footprint Calculators Make No Sense

At

[font=&quot]http://EcoPreservationSociety.wordpress.com[/font]

 

The whole thing with the buying and sellin of carbon credit is a farce. Unless I am just daft it just makes no sense.

What can possibly be straight forward about buying or selling something as intangible as carbon credits and just why do the sites in the OP vary so much?

 

In part the efficiency depends on the aircraft used. That may be where some of the variation comes in.

As for how one gets more mass of CO2 coming out than the mass of fuel going in: by mass, jet fuel is mostly carbon. It is a mixture of various hydrocarbons, and since hydrogen is extremly light most of the mass of the fuel comes from the carbon in it. When you burn those hydrocarbons to produce CO2 and water (and traces of other things) you are taking in a large mass of O2. While the mass of a hydrocarbon comes almost entirely from the carbon, the mass of CO2 is less than 1/3 from the carbon. Thus for a given mass of fuel you can end up with nearly 3x that mass of CO2.

 

How about the variations between the carbon calculators?

 

I'd have to see how the calculators are performing the calculation to know precisely what is causing the variation.

 

[font=&quot]I have learned that the answer lies with chemistry.

Jet fuel is made up of One atom of Carbon and One atom of Hydrogen. The Hydrogen atom is the lightest of all atoms and has virtually no weight.

A chemical reaction takes place when the fuel is burned. The One atom Carbon is separated from the Hydrogen, and it then combines with 2 Atoms of Oxygen from the atmosphere, making CO2. The Oxygen Atom is heavier than the Carbon, the total weight of the emissions end up being 3 times the weight of the original jet fuel.

Interestingly, the reverse happens in the photosynthesis process. A tree (or plant) will take in the Molecule of CO2. In photosynthesis, the Carbon and Oxygen are separated. The Carbon is stored in the tree and the Oxygen is released back into the atmosphere. Thus for every ton of Carbon stored in a tree, 3 tons of CO2 have been removed from the atmosphere.

I found this little carbon calculator that estimates the amount of Carbon in a tree and it bears this out.[/font]

http://www.greenhouse.crc.org.au/tools/calculators/treecarbon/treecarbonresults.cfm

 

That is more or less what I said above...

Jet fuel is not made of one atom of carbon bonded to one atom of hydrogen, however, because such a compound is not stable and can't be created (at least for more than a few milliseconds). A hydrogen atom has about 1/12th the weight of a carbon atom--much less, but far from nothing.

 

Suppose jet fuel is C12H26. One molecule needs 18.5 molecules of O2 for oxidation. This produces 12 molecules of C02 and 13 molecules of DHMO, often called "water". A rough calculation in ounces, grams ... choose your unit, is:

170 of C12H26 + 592 of O2 = 528 of CO2 + 234 of DHMO + heat

then, the ratio between the CO2 in the exhaust and the fuel is:

528/170 = 3.11

Jet fuel is a complex mix, but all the ratios from methane to mined coal vary between 2.7 and 3.6

Another reason for de deviation is taking a plane full passage, average passage or worst passage. A 747 with 300 people an their luggage on board maybe will waste 45 metric tons during a 5 hours flight. The very same 747 with 20 people on board and their luggage maybe would spend 37 metric tons because of the plane and the fuel itself won't become any lighter because the aircraft is almost empty.

There are lots of considerations to make about different aircraft models but the kind of flight is really important. When I flew from Buenos Aires to Montevideo (110 miles) the plane reached only 14000 feet, because of the short distance. But the plane spent about a third of fuel it would spend later in the Montevideo-Rio de Janeiro stage (about 1200 miles I think, more than 10 times) because of the take-off is which most fuel wastes.

All this kind of ruminations and the place where the very heart of the author is put, make the figures of CO2 go up and down, but be sure that half a ton of CO2 for a 3000 miles air trip is rather conservative. If the figure is 2.71 Tons per person with this oil barrel price, I'd recommend you not to buy shares of that airline as it'll soon go bankrupt.

[You're welcome to correct my English]

 

You got plenty of answers that explain the chemistry already, so I won't go into that. It's really, really basic chemistry. The problem that I have with your post is that you state that carbon calculators make no sense, but you appear to have absolutely no knowledge of chemistry. I get so sick of people with no scientific background running around saying that they know all about global climate change and that it's not man made.