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February 07, 2007
Carbon Math

In a multiply-updated post, Glenn Reynolds talks global warming and the effect thereupon of congressional "private" air travel.

In the course of the post, Reynolds cites this statistic from Tourjet (which, as the name implies, is an aircraft chartering agency catering to celebrities):

The typical American is responsible for 10 tons of CO2 emissions annually through their direct energy use of home, cars and air travel, and about 24 tons of CO2 including their purchases, activities and the other services we all share throughout the economy.

By comparison, a Gulf Stream III business jet (10-12 passenger) from New York to Los Angeles will emit around 31 tons of CO2 during the 6 hour flight.

I'm no airplane expert (merely a well-informed hobbyist, you could say) but it seems to me that if a cross-country fight produces 31 tones of CO2, this means the aircraft would have to carry well over 31 tons of fuel, as not all the consumed fuel would be exhausted as CO2. I have a hard time believing that.

Turning to airliners.net we can see a bit of info on the weight of the Gulfstream III:

Empty 14,515kg (32,000lb), operating empty 17,235kg (38,000lb), max takeoff 31,615kg (69,700lb)

Quick math.... OK, so at the very most, the plane can carry 37,700 pounds (18.85 tons) of non-airplane weight.* That's passengers, luggage, cargo, and fuel. While that is a lot, it's not 31 tons, it's not all fuel weight, and not all of of the fuel would be used on a NY-LA flight, since the aircraft's range is something over 4,000 miles.

Unless, of course, there's more than one airplane called the Gulfstream III....**

It is hypocritical for "jet set" celebrities and politicians to blather about reducing greenhouse gas emissions while burning fuel by the ton, but accuracy counts, too. In this case, it's not quite as bad as it appears at first glance.

(So, I hope I got the numbers right....)

* It's just a guess on my part, but I think the difference between the "empty" weight and the "operating empty" weight might be the airplane plus a full fuel load, which would make the fuel capacity 6,000 pounds.

** Update: Errr... nevermind. I forgot all about the oxygen input into the chemical reaction, which would indeed boost the output CO2 mass to something rather higher than the carbon input into the equation. Good thing I don't make my living as a chemist.

Posted by Russ at 09:07 PM, February 7, 2007 in Geekery & Politics

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Max fuel for the GSIII is around 28,000lbs. That's 14 tons. Not all of it is carbon. Even allowing for oxygen renders Tourjets figures questionable if not down-right false.

Posted by: Skul at February 9, 2007 12:15 PM

Actually, on further reflection, I think their numbers are pretty close. But if they do err, they err on the high side... which would be an "argument against interest" in their case.

Posted by: Russ at February 9, 2007 12:26 PM