29 June 2010

And the clouds would catch the colours everywhere

This year I have been making an extended effort to travel as ecologically as possible. Of course the most environmentally-friendly way to travel is not to travel at all, but as I have mentioned before I am something of a travel junkie, and though I love Dublin like a childhood friend that still remains close despite you having pretty much nothing in common now that you are in your thirties except the fact that you have a ridiculously long shared history, to survive in the city for any length of time whilst remaining fairly mentally stable requires frequent periods of being Elsewhere.

Thus throughout the year I have been frequently Elsewhere, but have gone to great efforts to travel there by train, boat and the occasional bicycle. There are sometimes, however, when you have to fly, and this weekend due to time constrains I was forced to fly part-way to Glastonbury (unlike Burning Man, Glastonbury does not, as of yet, have its own airfield, thus train journeys to and from the event are always a delightful, if cramped and smelly, feature). Rather than travel to London this year we chose to fly to glamourous Cardiff, and take a 2 hour or so journey from Cardiff Central to Castle Cary by train, and a significant factor in choosing to do so was the Aer Lingus Regional flight from Dublin to Cardiff, operated by Aer Arann.

Aer Arann run a fleet of ATR 72-500s, a turboprop rather than a jet-engined plane. According to Aer Arann these use less fuel (up to 70% less fuel than a jet on the same route), emit less CO2 and other climate-impacting gasses, and (again according to Aer Arann) have the same carbon-impact per passenger as a train. I took all these figures with a healthy dose of salt, but it was enough of a fig leaf to allow me to hide my carbon shame and book a flight.

Upon my return I decided to do a little bit of digging into these green claims. In "Sustainable Energy - without the hot air" David MacKay calculates the energy per unit of fuel as 10 kilowatt hours (kWh) per litre (he thinks in terms of the calorific value of fuel). If you take Aer Arann's figure of fuel consumption per passenger for a journey of 370 km for an ATR 72 of 16 litres, this works out at about 4.3 litres per 100 km travelled by a single passenger, or an energy cost of 43 kWh per 100 p-km. MacKay calculates that the energy cost of a fully loaded 737-400 works out at 42 kWh per 100 p-km. So the turboprop seems about as efficient as a fully laden jumbo jet, and also works out as being about as efficient as an average European car (which is the classic benchmark of environmental inefficiency, especially when travelling at anything less than full occupancy), which MacKay concludes uses around 40 kWh per 100 p-km when carrying two people.

However according to Garry Cullen, Managing Director at Aer Arran:
“The ATR operates more efficiently than jet aircraft on short-haul routes – up to 70% less fuel is required than a 737 on a typical Aer Arann sector. On a 370km sector, the ATR 72 – 500 fuel consumption per passenger is up to 15% lower than a typical European car. The associated ATR gaseous emissions per pax in terms of CO are 15 times less than a car and comparable to a train”
I am, of course, more inclined to go with MacKay's numbers, he is an academic expert in this field and was hired by the UK's Department of Energy and Climate Change last October as Chief Scientific Advisor (though I don't know if the appointment still stands with the recent change in management), but all of this goes to show that a) there are lies, damn lies and statistics, and b) I really don't know enough about the actual levels and impact of my carbon production.

What I take from all this is that a turbo-prop plane is as efficient as a half-full car (boo), but carries less passengers than a jet and has a lower impact per flight, so as long as less people fly in total on the route (ie they don't replace a single 747 flight with 10 turbo-prop flights) the environmental impact of a turbo-prop is less than that of a jet. However my own personal impact on the environment appears to be the same whether I fly by jet or turbo-prop, which is poo.

So it looks like its back to the trains for me, which MacKay calculates as having an energy cost of between 3 kWh per 100 p-km for a fully occupied high-speed electric train (like the TGV) and 9 kWh for a diesel train. Unfortunately doing so will rob me of the opportunity to take rather nice photos of clouds, like these on approach to Dublin at about 19,000 ft.

Links

Aer Arann's "greenest aircraft"
David MacKay's homepage
'Sustainable Energy - without the hot air' by David MacKay
A few more cloud photos

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4 Comments:

At 11:32 pm, Anonymous steve said...

good post.

 
At 1:52 pm, Blogger Snag Breac said...

I want to understand. I try to understand...but I like the cloud photos best instead....

Yes, I also tried to work out the carbon cost of driving to Devon last year and found it a very complicated affair. I would like to know more though. Interesting link to MacKay's stuff. Where is the numbers you found for cars and planes?

 
At 9:32 pm, Anonymous Sarah said...

In case of interest:

For the UK Defra produce pretty comprehensive conversion factors to calculate emissions from energy, travel, waste etc. They're more interesting than they at first look...

http://www.defra.gov.uk/environment/business/reporting/pdf/20090928-guidelines-ghg-conversion-factors.pdf

The instructions are fairly user friendly and I think you can get it as an excel based file on the website to help calculations.

The Irish conversion factors are slightly different due to the different energy mix and are listed on p38 (alongside many other countries).

Have fun...

 
At 11:10 am, Blogger Unkie Dave said...

@steve - cheers!

@Snag_Breac - the figures are from a few chapters in the book and based a lot on his own calculations, but he is an expert in the filed so I trsuts his numbers. That said the info Sarah linked too is far more comprehensive

@Sarah - thanks for the links, really comprehensive info, a lot to be looking at. I will do a deep dive and follow up in another post later on.

 

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