Math! CO2 emission by short-distance vs long-distance flight

A reader (apparently very well knowledge in aviation) reminded me of some very crude assumption I made when calculating CO2 emission for different type of aircraft/aeroplane in the previous post. I must admit that it was not a very detailed math work. I made very bold assumptions such as taking out plane take-off phase out from whole fuel burn/CO2 emission from calculation because firstly these numbers are not readily available to me (from the plane maker/manufacturing site) and secondly I assume that the plane take-off time is relatively short compared to whole cruising time. This could be true for the long-distance (may be more than 600km above?) or cross-continental flight, but the take-off period will be significantly mean something for shorter distance. And the calculation below might show you how…

Scandinavian Airlines (SAS) has this webpage which can be used to calculate your CO2 emission for the flight you take and offer you to buy carbon offset. Well, the latter part is not my point here, and I am just conveniently borrowing their readily available calculator to show that how short distance flight emit more CO2 than the long-distance flight.

Here, I am using Helsinki (HEL) as my base. The places I choose are: Oslo (OSL), Stockhol (ARN), Kuopio (KUO), JFK Airport, New York (JFK), Jyväskylä (JYV) and London Heathrow Airport (LHR). The table below here shows the cabin factor [CF] (%), distance (km) and CO2 produced in kg. Since the cabin factor and type of aircraft is same in each class, CO2 per km is easily calculated:

In the first group (Avro RJ85-small plane), a person who take the trip from Helsinki to Oslo with a CF 71% produced 147kg CO2 while flying from Helsinki to Kuopio (a shorter distance) on the same plane and CF will emit 89kg CO2. By comparing CO2 per km factor, trip to Oslo is emitting only 0.193 kg CO2 per km while 0.266 kg CO2 per km to Kuopio, an almost 1.38 times higher than Oslo trip.

Another example is taking KF average aircraft group. A flight to Heathrow London emits 0.133 kg CO2 per km for long distance, but on shorter distance like flying from Helsinki to Jyväskylä emit 0.272 kg CO2 per km distance travelled, which is 2x the number for Hel-London trip!

Now, it is quite obvious to note the relationship of distance travelled is inverse with CO2 emission kg per km. What if I want to fly to New York from Helsinki? That is 6602km away. SAS gave a different average CF for this flight: 88%. That is higher than the other flight in compared here (71%). To make it an apple-to-apple comparison:

Total CO2 emission for flight with 88% CF (or let’s say 88 persons):

          Total CO2 = 88 x 462 kg = 40 656 kg 

Total CO2 emission is the same for flight with 88% CF or 71% CF, therefore CO2 emission person in 71% CF (or 71 persons) flight:

          CO2 per person = 40 656 kg ÷ 71 = 572.6 kg

Therefore the CO2 emission per km is: 572.6 kg ÷ 6602 km = 0.087 kg CO2 per km for flying from Helsinki to New York.

In terms of absolute number, long distance flight inevitably produces more CO2 compared to the short one. However, if we take the CO2 emission per km as a fair comparison, short distance flight is shown to be less CO2 environmentally friendly. And my great suspect would be that the plane take off phase as I mentioned earlier in the beginning of this post, becomes significant especially for short-distance flight (e.g. 10 minutes take-off in 40 min. vs 400 min. flight). Could the altitude which the plane fly influence on the fuel efficiency as well? (short flight -> low altitude -> higher air density-> higher friction -> higher fuel consumption?)

P/S: SAS webpage says something about the accuracy in their CO2 calculator – The estimation of aircraft emissions is still not a perfect science and is subject to debate. Actual emission levels for each flight are dependent on operating parameters like load onboard, flight profile, temperature, winds, fuel and engine/aircraft characteristics. Assumed flight average and calculation method can vary from operator to operator, making comparisons difficult.

4 Comments

  1. Paul said,

    May 21, 2007 at 8:26 pm

    Hello again.

    Firstly, kudos because as I said, your calculations (both first lot and these) are well-presented, and as accurate as the information you had available really allowed you to be. Many people do far worse. There was a scornful letter in a pilot union magazine ridiculing the claim that a tonne of fuel produced three tonnes of CO2 – but it didn’t take very long to work out that the claim was indeed correct.

    By loco I did indeed mean low cost – and yes, the claim they make that they fill up their aircraft with high-density passengers and generally use newer aircraft (by doing big orders in bulk) does make them “greener” per passenger than the traditional carriers – particularly ones like Alitalia who are not only not green but not making profits either.

    Fuel burn is at a peak at take-off power, obviously, but rather than dropping to cruise levels straight away decreases in the climb. But actual fuel burn is dependent upon routes, cruise levels, deviation from ISA temperatures …. and all sorts of things. The caveats on the SAS website that actual calculation of CO2 emissions is definitely not a perfect science – and this is certainly true!

    One more thing. A ballpark figure is that carrying an extra tonne of weight in an airliner increases the fuel burn by 35 kg per hour. That corresponds roughly to 10 passengers and their bags. And that is, of course, around 100 kg of CO2 per hour – or 10 kg of CO2 per hour per passenger. But that assumes that the aircraft will travel anyway, and doesn’t take into consideration the CO2 produced just for the aircraft to fly empty ….. How complicated it all is!

  2. Sabeena said,

    May 19, 2008 at 11:58 am

    can u put a lil more details into the CO2 emission during climb and descent phase?

  3. hermione uchiha said,

    October 6, 2008 at 1:31 pm

    love how it helped me out!!!
    hermione

  4. November 9, 2010 at 3:00 pm

    Hi , can u put a mathematical equation(s) for the calculation of the co2
    e,mmitted by different jet airplanes.
    The calculation you mentioned ,does it include the engines emmission?
    or both passengers and engines.


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