Aircraft and CO2

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Are planes so polluting?

We recently read this on the Nouvel Observateur website:

"I would like a round trip Paris-Bangkok in a plane of recent and well filled invoice". This is what a traveler very concerned about fighting the greenhouse effect could ask his travel agency. By plane, a passenger emits on average 140 grams of CO2 per kilometer, against 100 on average by car, recalls the French Institute of the Environment (Ifen) in a summary on the contribution of air transport to the greenhouse effect. Even taking into account emissions from car manufacturing and petroleum refining, the aircraft rejects 16% more carbon dioxide per passenger.

Even in the best conditions of filling, type charter flight, a return Paris-New York corresponds to the rejection of a tonne of CO2 per passenger, says Ifen in the latest issue of Environmental Data. The most polluting flights are the shortest.

CO releases2 are not the only contribution of air transport to the greenhouse effect, Ifen continues. The planes also reject nitrogen oxides and water vapor which promotes the formation of contrails.
The work of Patrick Minnis at NASA's Langley Research Center has shown that these trails form cirrus that retain heat.

Global air transport accounts for 2,5% of global CO emissions2 related to fossil energy consumption. The room for maneuver to improve the energy efficiency of the aircraft is very limited, underlines the Ifen article. As a result, with increasing traffic, the impact on the climate will intensify. "

And here is our reaction:

This news is however completely erased here is the proof by calculations.


I recently calculated the mass rejects starting from the complete (and ideal) combustion equation.

The following figures result: An engine consuming 1 L gasoline will therefore reject a little more than a kilo of water and 2.3 kg of CO2.

But kerosene, jet fuel, is heavier than gasoline (see its properties here: properties of petroleum fuels ). Take a number of carbon atoms of 12, a forumthe average chemical level of C12H26.

According to the combustion formulas, it comes:

Application to kerosene. n = 12
[C12H26] = 12 12 * + = 26 1 170 * g / mol.
The mass of CO2 released per mole of kerosene consumed is: 44 * 12 = 528 g.
The mass consumption ratio of kerosene on CO2 releases is 528 / 170 = 3.10

This means that for 1 kilo of kerosene consumed 3.1 kilogram of CO2 are emitted.

The details of the combustion calculations are on this page: combustion equations and CO2 hydrocarbon emissions

Let's go back to the article.

According to this one: a round trip Paris-New York rejects 1 ton of CO2 per passenger.

This means that 1000 / 3.1 = 322 kilogram of kerosene have been consumed, ie 322 / 0.8 = 402 L because the density of kerosene is of the order of 0.8.

The distance Paris New York is 5850 km approximately 5850 * 2 = 11700 km for a round trip.

402 L to make 11 700 km ... this gives us an average consumption per passenger from 3.43 L to 100 km.

What current mainstream car is capable of such low consumption? None without hesitation!

And yet the article still pushes a little nail:

"An airplane traveler emits approximately 140 grams of CO2 per kilometer, compared to 100g / km for a motorist."

Here then ? Assuming that the driver is alone in his vehicle and in the same opposite way, a gasoline car emitting 100 g CO2 / km will consume 100 * 100 / 2.3 = 4.3 L / 100 ... Very little gasoline vehicle are capable of a Such consumption .. I do not speak obviously of urban traffic! The reality is rather close to double ...

Another reasoning would be that the plane consumes 40% more than the car, or conversely that the car consumes 28% less than the plane ...

A small digital application with the 3.43 L digit at the 100 km for airplane consumption gives a 3.43 * 0.72 = 2.46 L / 100 vehicle consumption.

Again: What current car is capable of such consumption? None (bis)!

Note: The average filling rate of European cars is between 1.2 and 1.6 person / car, a calculation correction is possible thanks to these figures to obtain the rejections or average consumption for cars in g of CO2 per km.passager or L / 100km.passager. In any case, and according to the initial figure of 1 tonne of CO2 for a round trip Paris / New York, the plane remains less consumer than the cars.


Here I stop to say that it seems to me that the figures announced in this article are either erroned or that air transport, mass long distance, is less polluting than road transport ...Yet the authors of the article have not really stated that.

The major problem of the future is indeed land transport and the growth of the world car fleet.


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