hold on, what kind of emissions attribution is happening to make business class travel less CO2-efficient than economy class travel?? your ass weighs the same no matter which chair you sit in
@whitequark they are larger to you can have less people per flight?
@whitequark It's about the volume, not the weight.
@whitequark my guess would be that they're basing it on the total emissions of the plane for the journey divided by the relative space taken up by the passengers.
to everyone who responds with "it's proportional to square footage": nobody flies planes configured for business class only. "if the moon was made of cheese we couldn't mine 3He from it" but in reality it isn't so why should I accept this assumption?
@whitequark my guess would be that it’s because you can fit more economy passengers on the same plane, and while each passenger is going to take fuel either way you’ve still got to account for getting the plane itself in the air.
@whitequark it *should* be about the weight rather than the volume because thrust overcomes drag, and induced drag originates from the lift vector being in slightly the wrong direction, which must counteract the total wet and dry mass of the plane
this was also the rationale given for trying to overcharge overweight passengers. it was a more woke time though, so as far as i remember those kinds of surcharges fell out of favor (?)
@whitequark If you follow the breadcrumbs, it leads to IATA RP 1726 by way of https://github.com/google/travel-impact-model , which prescribes a cabin class factor with very little justification. Despite the lack of concrete justification, this is an industry publication, and I don't think it's unreasonable to use their own best practices in lieu of a better model.
I don't see how you can argue that business/first is equally efficient to economy, so on what basis would you prefer to reconcile that? Are you trying to argue that because business seats exist on the plane, you shouldn't be responsible for their contribution to reduced per-pax efficiency if you use one...?
@whitequark not to make this even more complicated, but a lot of routes are heavily subsidized by cargo, which probably has to figure into the calculation somehow if you're trying to apportion the CO2 of the whole flight
@whitequark I'm not entirely clear on how these things are computed, but I kinda assume they have to be assigning everyone some amortized portion of the cost to fly the plane empty? and like, if there was less demand for a given class, they'd fly planes with less of that class, which potentially means smaller planes
@whitequark and removing a row of business gets you a lot closer to the next-size-smaller plane (with lighter fuselage, lower fuel burn per mile, etc) than removing a row of economy, and it also potentially allows you to fly more people on the same fuselage by adding more economy, which reduces the per-passenger fuel burn…
@rcombs hm, is it actually the case that smaller planes have lower fuel burn per mile? that doesn't make sense to me. why even have big planes if so
@whitequark @rcombs Presumably larger planes have higher fuel burn per mile and lower fuel burn per mile per passenger.
@whitequark if it wasn't true, why even have small planes? any given plane is most efficient per-passenger-mile when flown close to 100% load-factor
a smaller version of the same plane (same engines, avionics, etc) has lower dry weight and will cost less to fly empty
on the other hand, flying 1 big plane is usually more efficient than flying 2 planes that are half the size, because the 1 big plane has less dry weight than the 2 small ones (and costs that are fixed regardless of size, related to eg drag and takeoff/landing, would be increased in the 2-small-planes case)
@whitequark @rcombs it's going to depend a lot on what engines are on the plane, but in general bigger airframes have bigger engines and bigger engines use more fuel
they don't necessarily use proportionately more fuel, though; in absolute terms a bigger engine uses more fuel, but it produces more thrust, that additional thrust means it can carry more weight, and that means more passengers and cargo. if the increase in revenue from passengers and cargo outweighs the increase in costs from fuel, it makes sense to use the larger plane
or in other words, if both a larger plane and smaller plane can carry your passenger and cargo load, the smaller one is likely to be more economical (but this is a really complicated discussion because it needs to consider things like flight time, fuel burn per hour, what cruising altitude each plane has...)
@demize @whitequark I'm largely setting aside differences in the engines themselves in favor of assuming they're mostly going to be similarly efficient in their design deployments these days, but compare eg: a 737 MAX 10 carries ~33% more passengers than a MAX 7, has ~12% more MTOW, and has 72% more cargo space, but weighs ~13% more empty; same engines
those numbers pretty clearly add up to "the bigger one is more efficient on more-popular routes, while the smaller one is more efficient on less-popular ones"
@whitequark @mcc I mean, if the counterfactuals are "fly 2 planes" and "fly the big plane half-empty" respectively, then they absolutely can both be true, just in different situations
@ktims no, I argue that you shouldn't pull causal attribution out of your ass if you want your statistics to appear trustworthy and not undermine your cause
@ktims thank you for tracking this down, I didn't realize IATA publishes this document. I agree that this is not on the author of the inforgraphic in this case
@estelle yeah i don't think anybody tried it since, and even at the time it was probably a publicity stunt? wasn't it done by ryanair
@whitequark i had to look it up, it appears to have been started by samoa airlines in around 2013 (has it been that long?), and cnn circa 2023 says united airlines and others require buying two seats, but may refund it if empty seats are available
fox news (ugh) outright states in their article that "1% reduction in weight would save 0.75% the fuel consumption"
canada appears to have a "one person, one fare" law for airliners
(i have not flown in an airliner for a very long time)
@whitequark as we all know planes burn fuel based on floor space, and not on some other unit
@whitequark square footage is not the correct metric, obviously. But first class seats are heavy. A brief web search not only gives me figures of 135kg to over 200kg for the luxury variant which already nearly doubles to triples the weight pp, in some cases airlines even need to add counter weights to the back of the plane. Add things like showers and the additional water for those.
These are extremes, of course, but this can add all up.
i stand corrected, your ass does weigh more in a first class seat (if you add the weight of the seat in) https://ruby.social/@halfbyte/117118864402458450
@whitequark compared to how much the plane and fuel weighs, the total uhm, biomass in the plane is really not that much
interestingly, the infographic above doesn't look like a very close match to IATA class factors (below; which i didn't know about) but is a pretty close match to "going from economy to business class seat effectively doubles passenger weight"
for a B737-600, it's 36 t of plane and 13 t of pax (and then fuel)
fuel load significantly varies with passenger count
@whitequark the max weight is 65.5t so only ~20% flesh 😅
@thomasfuchs 737-600 is a regional jet, you wouldn't normally load it to the brim with fuel
@whitequark apparently that specific plane isn't popular with airlines because of passenger count and routes for that sort of range, and flying shorter trips isn't as efficient as with some other planes.
we live super close to an airliner graveyard (they park unused planes there), can see it from my house... should try to go there some time and make some photos
@whitequark that being said, I find your argument about how airlines don't fly economy only a bit disingenuous. "These flights would not exist without the business class seats" is probably correct, but that should not affect an attempt to properly attribute emissions to different seatings, should it?
@halfbyte I think it is intellectually dishonest to make attributions like that when no clear causal link exists
@halfbyte now I'm not saying there's no link. the fact that business seats subsidize the existence of some flights is a link, and a pretty important one! but that doesn't justify distilling it into an infographic with opaque assumptions that imply a clear and immediate causal link where there isn't one
@whitequark to be honest, in the grand scheme of things, it probably doesn't even matter. People who fly business or business plus or whatever are (with the obvious exceptions, see my other post, haha) probably frequent flyers, so their CO2 emissions are off the charts anyway, so a one digit factor is probably ending up as a rounding error.
@halfbyte ... which would have been a much better statistic to highlight in terms of impact
@whitequark that said, one last tidbit from the article that mentioned the counter weights (a refitting of a Swiss A330 btw.), they ended up with an emission factor of ~5 due to the 1,5t counter weight. Guess which seats actually got lighter in the refitting. Also the counter weight obviously means higher overall emissions for the flight.
That's just completely bananas.
@gsuberland right so the next question is "why is this an intellectually honest way to calculate per-passenger emissions"
@whitequark so the value judgement they're making there would be that if business class wasn't there then you could move more people per flight, thus making it more carbon efficient. I don't know if that's the *best* way to think about it, but it is one way.
@gsuberland right, but as far as i know airlines barely (if at all) break even on economy class seats, so it's just as easy to argue that if business class seats weren't there we'd just see fewer flights. (which would probably be even more carbon efficient?)
@whitequark yeah it's not very coherent
@whitequark it does rather gloss over externalities doesn't it
@whitequark @gsuberland if the plane would have flown empty, it's not.