On 9/23/05, Appal Energy <[EMAIL PROTECTED]> wrote:
Ray,
> so it uses around 26 tons of fuel in 800
> miles but they say they put out 28 tons
> of co2 in the same distance?????
This is a the short version of a long-winded explanation as to why the
weight of carbon dioxide appears to be so disproportionate after burning
jet fuel (or any fuel).
Jet fuel is a mixture of long, carbon-chain and carbon-ring molecules,
including paraffinic, olefinic, naphthenic and aromatic hydrocarbons. So
there is no overly simple method of calculating how many carbon
molecules are in liter of fuel (at least not without a sample of it and
a lab).
However, just for mind candy, take a look at a biodiesel molecule with
sixteen carbons lined up in a chain. Each has one hydrogen molecule
attached above and below it (two). One end carbon also has a hydrogen
attached to the side of it. The other end carbon has a hydroxyl group
(an oxygen and hydrogen molecule) attached to it. That essentially means
that there are 33 plus 1 hydrogen atoms, 1 oxygen atom and 16 carbon
atoms for every biodiesel molecule that ha 16 carbons in its chain.
(Some have a few more carbons and some have less, depending upon the
type of fatty acid (oil) they were formed from.)
Hydrogen has a molecular weight of one. Oxygen has a molecular weight of
sixteen, which means it's sixteen times heavier than hydrogen. Carbon
has a molecular weight of twelve. For every hydrogen burned off the
biodiesel (or jet fuel) molecule, at least one oxygen molecule
re-attaches. If carbon monoxide is produced, then only one oxygen
attaches. If carbon dioxide is made then two oxygen molecules attach.
So, for simplicity's sake, when two hydrogens are burnt off one carbon
(C+H+H=14), one or two oxygens take the hydrogen's place (C+O=28) or
(C+O+O=44). That makes each post combustion molecule with a carbon in it
two or three times heavier after combustion than before.
If a person wanted to get more precise, some fuel isn't completely burnt
in the turbine, meaning that handfuls of hydrogen and carbon molecules
exit the combustion process partially intact. That means that the
hydrogen-oxygen exchange isn't exactly one or two to one
But very roughly put and depending on the efficiency of combustion, it's
not too difficult to see that one pound of a specific type of fuel going
into a turbine or engine (a long carbon chain) can turn into two or
three plus pounds of CO2 coming out.
Todd Swearingen
>Specs on the current model Boeing 747-400, 57,000 U.S. gallons fuel
>capacity with 8,000 mile range so it gets something like 6-9 gallons a
>mile. so lets say 8 gallons/mile, at around 8 pounds per gallon,= 65
>pounds of fuel per mile... so it uses around 26 tons of fuel in 800
>miles but they say they put out 28 tons of co2 in the same distance?????
>
>thats interesting...
>
>Ray J
>
>
>
>
>>Just seen this on our BBC TV channel " every 800 miles travelled by a jumbo
>>jet dumps 28 tons of CO2 into the atmosphere." Chris
>>
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