Carbon Confusion

Even though I suppose I’m an engineer of some description, I still consider myself to be more of a scientist than the average bloke in the street.  I feel sort of entitled to think this having sat through 2 years of the most mind-numbingly boring A-level chemistry lessons which would have made watching paint dry seem like an adrenaline sport.

At any rate, I consider myself clued up enough to spot glaring errors in Guardian articles on the environment: 

Yesterday the holiday company Airtours launched what it claims is Britain’s first round the world package holiday: a 23-day whistlestop tour of 10 countries at a cost of £4,499. Scheduled to take off from Manchester airport on February 27 next year, the Airbus will carry 329 passengers, three pilots, 10 cabin crew, 10 holiday reps and a doctor.

As environmentalists were quick to point out, they will also emit a staggering 2,289 tonnes of carbon – equivalent to the weight of 286 double-decker buses.

Sorry?  They’ll emit carbon?  As in soot?  Product of unburnt fuel?  I never knew aeroplane engines burned so rich.  Maybe they should get under the engine cowlings and play with the mixture screw a bit.

Or maybe they are on about carbon dioxide, the greenhouse gas they are all so worried about, too much of which is going to cause the earth to heat up a bit.  Sitting on Sakhalin Island watching the thermometer plumb to minus six this morning I fail to see what the problem is.  But whatever my meteorological preferences, the terms “carbon” and “carbon dioxide” are not interchangeable any more than “hydrogen” and “water” are. 

Not only are they very different substances, but the manner in which these terms are used are completely arse about face.  Contrary to the article quoted, no carbon is emitted during an aeroplane flight (a miniscule quantity of partially burned fuel notwithstanding).  The carbon is locked inside the fuel combined with other elements, chiefly hydrogen.  When the fuel is burned, the carbon and hydrogen separate and join with the oxygen in the air to form carbon dioxide and water respectively.  Carbon as a substance on its own doesn’t come into it.

So all this talk of “carbon credits”, “carbon sinks”, and “weights of carbon emitted” leaves me all rather confused.  If people are going to able to sell carbon credits, then the Yanks must be laughing all the way to the bank because they have greater coal reserves than anyone else.  And when environmentalists talk of aircraft emitting 2,289 tonnes of carbon, are they talking about large piles of graphite or are they talking about carbon dioxide gas?  Because if they cannot manage to get even the basic terminology right, why should we bother listening to anything else they say?

(via J.F.Beck)


6 thoughts on “Carbon Confusion

  1. ” Because if they cannot manage to get even the basic terminology right, why should we bother listening to anything else they say?”

    Tim, you’re just being a pedant. The carbon here is the carbon content of the CO2: about 26% of the mass of CO2 emitted.

    This is a commonly used translation.

    The problem here is that journos get confused and don’t realise the 26% conversion to from CO2 to carbon, which is quite probably what has happened here.

    Going backwards to the fuel, and for simplicity using pure octane (I know – can’t be bothered to do the maths for JET-A1), carbon is 84% of the molecular weight so this corresponds to 2,700 tonnes of Octane.

    Given that the A340 (which they are going to need if they want to carry that number of people and, more to the point, get across the Pacific…) with a max fuel load of ~120 tonnes, this corresponds to around 23 full fuel loads. Sounds a bit high to me…


  2. This is a commonly used translation.

    Amongst whom? Journalists and environmentalists? I can’t believe that any serious scientist worthy ofthe name would simply use carbon as shorthand for carbon dioxide.

    If this is indeed widespread practice, it smacks of dumbing down the language for an audience who doesn’t understand the basic concepts of what is under discussion – hardly a basis for discussing what is supposedly the greatest threat to mankind.

  3. Tim,

    I’m neither climate scientist nor environazi dogooder, but I think this is actually quite simple.

    The use of “carbon” as the measure makes it that much easier to compare the impact of different fuels: 1 ton of coal burned equates neatly to 1 ton of carbon into the atmosphere (well, pretty largely). The higher the molecular weight of hydrocarbons, the closer the approximation becomes in this case also (assuming Cn H 2n+2, the carbon content approaches 12 out of 14 parts by weight as n increases).


  4. PG,

    I understand. Thanks for explaining the reasoning behind the terminology.

    I still don’t like it though. Frankly, if people can’t be bothered to make the calculation from mass of carbon burned to mass of resulting carbon dioxide, they shouldn’t be quoting numbers.

    I guess it just annoys me, just like it annoys me when people talk about Volts running through things.

  5. Alas, I wouldn’t know a carbon from a lardon (during my fry-up attempts the one becomes the other) but I can spot an overcrowded political bandwagon when it runs me down and the occupants help themselves from wallet!

    Off subject, I note your interest in Russian WWII history and would recommend “Grand Illusion” by Gabriel Gorodetsky, Yale University Press, 1999 (try for an excellent and scholarly overview of Stalin’s grand strategy. In fact, now that I’ve dug it out, I must re-read it!

  6. There is a distinctive lack of posting on this blog, does Sakhalin lack electricity or will this be refuted by the appearance of a White Dwarf in the near future?
    You owe it to your audience to come clean.

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