hmmm ... interesting

(1) what about the QE2 travelling at sea level and the 747 at some 13km 
above?  I think should be considered when you ask whether emissions are 
"better or worse"  (notably not more or less).
(2) why don't you take the crew into account (~920 on QE2, 20...30 on a 
747)
(3) are you actually comparing means of transport or are you comparing 
different lifestyles, i.e. luxury cruiser vs economy flight and then 
telling us that a luxury lifestyle produces more CO2 emission?  now 
that's a surprise ;-)

/ Peter

On Jul 18, 2005, at 13:42, George Marshall wrote:

>  Dear friends,
>
> I have been distracted by a question which has been puzzling me for a 
> long time: are emissions from a ship actually better or worse than 
> flying? In materials and discussions we often assume uncritically that 
> ships are technologically superior to ships in emissions terms.
>
> So I have done a simple and undoubtedly conjectural comparison between 
> a transatlantic journey by 747 and by the QE2- and it doesn't look 
> good for ships.
>
> 747s and the QE2 are of similar age in technology. The QE2 had the 
> then most efficient engines  installed when refitted 15 years ago. 
> Because I am comparing technologies,not actual emissions  I have 
> assumed 100% occupancy of both 747 and QE2
>
> OK the figures:
>
> The QE2 holds maximum 1,800 passengers. It burns 433 tonnes of oil per 
> day at sea, says Cunard,  and takes 6 days for the southhampton to new 
> york trip. This is 2.88 tonnes of oil per person for a return trip. 1 
> tonne of marine fuel contains 0.85 tonnes carbon, or converted to Co2 
> (x3.72) this is 3.16 tonnes co2/tonne. So, a return atlantic trip on a 
> full QE2 will be 9.1 tonnes of CO2 per passenger.
>
> This is at the highest end of the  estimates I have seen, a full 747 
> will emit up to 800 tonnes CO2 on the same return route. If we assume 
> a further 'uplift' due to contrails, nitrous oxides etc and multiply 
> by 2.7 (the IPCC's reckoning) that is 2160 tonnes of CO2 equivalent. A 
> 100% full jet with 1st, business and economy classes has 406 seats. So 
> a return atlantic trip on a full 747 will have a climate impact of 5.3 
> tonnes of CO2 per passenger. But, here's the crunch, this is high 
> because it allows a lot of space for the first and business 
> passengers. If all passengers were in economy seating, there would be 
> 600 seats, which would be 3.6 tonnes per person.
> The emissions per passenger of the QE2 are therefore 2.5 times greater 
> than economy passengers flying.
>
> Of course, one could argue that the QE2 is a luxury vessel and 
> wasteful of space etc. However, it is also relevant that it is an 
> extremely large vessel, carrying 5 times more passengers that a 747 
> (not to mention all the support staff), so it should be able to 
> achieve far higher economies of scale than a small vessel like a 747. 
> If we wanted to compare luxury with luxury, we can consider that first 
> class passengers on a 747 take twice the space of economy passengers. 
> So, even if the 747 were totally first class, passenger emissions 
> would still be lower than the QE2 at 7.2 tonnes CO2 per person.
>
> And there is reason to believe QE2 emissions may be higher still. 
> Whilst the 747 has been penalised for the 'uplift' caused by 
> contrails, nitrous oxides etc, the QE2 has only been judged for CO2. I 
> have charitably assumed 100% conversion of fuel, but if any of the 
> carbon is released as particulates that too will have a powerful 
> multiplier effect. Marine engines are usually extremely dirty,although 
> the CO2 will be at the cleaner end I imagine.
>
> This is not the end of the comparison. There is the matter of embodied 
> energy. The aluminium (80% of the total weight) of jumbo is 75 tonnes 
> (embodied emissions- assuming not HEP powered, are 27kgco2 per kg 
> aluminium). So the embodied emissions in a 747 are 2,025 tonnes CO2, 
> or 5 tonnes per passenger place.
>
> Now the QE2 on the other hand, weighs 70,327 tonnes. I have no idea 
> what percentage is steel, but to be charitable, I will assume 80% 
> again. The embodied emissions of steel are 3.2 kg CO2/kg steel. So the 
> embodied emissions of the QE2 are 180,037 tonnes CO2, or 100 tonnes 
> per passenger place.
>
> All in all I think there are grounds to seriously question whether we 
> can say that boats have lower emissions for intercontinental travel. 
> What we can say is that people will not be popping over to New York 
> for a shopping weekend if they had to take 2 weeks to get there and 
> back and pay through the nose, but are there not ways to discourage 
> flying which have a similar effect?
>
> Any thoughts or challenges to my figures?
>
> Love
>
> George
>  
>
> --
>
> George Marshall
> Co-Executive Director
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