Thanks for the replies!
I have to say, Mad (Flt) Scientist's reply gave me a chuckle - more so than the wealth of Michael Jackson jokes doing the rounds at the moment!
Seriously, though, at 296 - 298 gallons per tonne, that's not doing much for the carbon footprint.
At today's price of 601 USD per tonne, that is an extra cost to Emirates of between 2704 USD to 3906 USD, but of course as Mad (Flt) Scientist said, a tiny fraction of the cost of not going around!