[alhw]

Jet fuel is comprised mostly of hydrocarbons with 8 to 16 C atoms, and a large fraction of these hydrocarbons are straight-chain alkanes.

Combustion of dodecane (a C12 straight-chain alkane) makes 12 CO2 molecules. A 747 jet consumes about 4 L of jet fuel per second when in flight. Based on the density and molecular weight of dodecane and the stoichiometry of its combustion reaction, you'd arrive at something like 0.01 ton of CO2 emitted per second of flight time.

4000 tons is a good estimate.

Back of the envelope...

[mabbo]

Ah, so you're saying (if I'm reading this correctly) that the plane only carries the carbon portion of the CO2, and the oxygen comes from the air itself. That's how it's emitting more CO2 then it's fuel mass.

Is that right?

[Tuxer]

Correct. Fuel is around 16/36th of the CO2 mass it emit when being burnt. A 777 carries around 120 tons of fuel for a SF/LON flight, so that's around 300 tons of emissions per flight.