Why I Think The Kyoto Rules Treat New Zealand Sheep, Beef And Dairy Farmers Unfairly

At least one reader of Kiwiblog appears not to have understood the point I was trying to make about the rules around methane production so I will try and explain myself more clearly.  Yes, I know methane is a potent GHG and that it is probably one of the worst GHGs because of its half life being so long.  I also know that the carbon atoms in methane molecules that are produced in the gut of a ruminant come from carbon stored in the grass not from the atmosphere (I actually thought that was pretty clear from my post).

The point I was trying to make was that farmers are being penalised for the amount of methane produced without adjusting for the fact that to produce the methane their pasture has absorbed close to an equal amount of carbon.  I really only know wine making chemistry so can’t comment definitively about the relative bulk of a tonne of methane as compared to a tonne of carbon dioxide but I can tell you that a molecule of CO2 has as much carbon as a molecule of CH4.  Each contains one atom of carbon.  My guess is that it is almost a one to one conversion.  If one looks at the latest edition of the Ministry of Economic Development’s publication New Zealand Energy Green House Gas Emissions you can see that in one of the tables  (1.1) all gases are converted to CO2 equivalent.  Agriculture produced 37,668 Kilotonnesof CO2 equivalent.  This is made up of 24,866 kt of methane and 12,802 kt of nitrous oxide N2O.   

From the above we know that to produce the 24,866 kt of methane (CO2 equivalent) New Zealand farmers have had to absorb roughly 24,866 kt of CO2.  Why do the rules not give credit for this?  I have seen some argue that it is impossible at this time to tell how much CO2 is absorbed by a New Zealand farm.  This may be true, but a chemist can tell you exactly how much CO2 must have been absorbed by pasture to produce the methane which the Government says it knows each farm is producing.  I think it is unfair that our farmers are not being given credit for this CO2 absorption.

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6 Responses to “Why I Think The Kyoto Rules Treat New Zealand Sheep, Beef And Dairy Farmers Unfairly”

  1. Andrew D Says:

    I believe you have a couple of points wrong.

    1/ Methane is a nasty GHG because it is so effective at scattering infrared light, which is the physical mechanism that leads to the greenhouse effect. This is greatly mitigated by its SHORT halflife in the atmosphere. CO2 is a much less effective but has a very LONG halflife in the atmosphere. Kyoto weighs these two factors by means of a 100 year average and charges each molecule of methane as being worth 25 molecules of carbon dioxide. (Sadly N2O is both an effective GHG and longlived in the atmosphere, which is why the very small N2O emissions from agriculture contribute about a third of New Zealand’s overall CO2 equivalent GHG emissions.)

    2/ If we do as you suggest and give farmers credit for the fact that the carbon comes from grass that recently absorbed the carbon from the atmosphere then they should perhaps be charged only 24 molecules of CO2 for every molecule of methane emitted. I don’t know whether this small discount would be worth the effort required to obtain it.

    If I understand the data right and New Zealand farmers have emitted roughly 24,866 kt of methane (CO2 equivalent) and so they have had to absorb ONLY about 24, 866/25 = 1,000 kt of CO2 to produce that much methane. And we still have to pay for the nitrous oxide.

    So rather than a overall liability of 37,668 kt CO2 equivalent, we might by this argument have a liability of around 36, 668 kt CO2 equivalent. Now would Kyoto as written allow us to claim that 1,000 kt? I don’t know, but yes perhaps it should and perhaps a successor agreement should more fully account for the effects of agriculture.

    (If I have not been clear about why the CO2 absorbed is only 1,000 kt let me know and I will try again.)

    • charlesf Says:

      Thanks for this. Can you explain a bit more fully how 1 tonne of stored CO2 is all that is needed to produce 25 tonnes of methane?

  2. Andrew D Says:

    Lets suppose we agree that Kyoto has many well known flaws. Shouldn’t we just accept its deficiencies at this point and attempt to get into the best position to positively influence the successor agreement?

    I would think the main issues for agricultural emissions in the successor agreement (some of them raised in your earlier post) are

    a/ shouldn’t this question of whether to charge producing nations or consuming nations be treated consistently between fossil fuels and agriculture? and wouldn’t it be simpler to charge the producing nation and have those costs passed on the consumer in the usual way?

    b/ do we know enough about the carbon cycle in agriculture to regulate agricultural emissions fairly and accurately?

    c/ would it be easier to bring all nations into a Kyoto successor agreement if agricultural emissions were left out until some later point?

    d/ given methane’s very short lifetime in the atmosphere, is the 100 year average the right way to treat methane in the first place?

  3. Andrew D Says:

    OK here goes. And it turns out I am slightly wrong above so I should in any case correct myself.

    The first thing to note is that one kilotonne CO2 equivalent for a given GHG is not the same as the number of tonnes of that gas. Take a look at http://en.wikipedia.org/wiki/Co2e.

    The mass of each gas is multiplied by a weighted average of how effective it is at scattering infrared light and how long it remains in the atmosphere.This factor is apparently known as the “global warming potential” and is chosen to convert the masses of all gases into some effective mass of CO2. For methane it is 25. I’ll leave aside any explanation of exactly how this number is arrived at but as I say methane is a very effective GHG that is shortlived in the atmosphere.

    I had this slightly wrong above when I said “Kyoto… charges each molecule of methane as being worth 25 molecules of carbon dioxide”, I should have said “Kyoto charges each tonne of methane as being worth 25 tonnes of carbon dioxide”

    So if we emit roughly 25, 000 kt CO2 equivalent of methane, that is only about 1, 000 actual kt of methane. Likewise the roughly 12, 802 kt CO2 equivalent of N2O is only about 43 kt of actual N2O since the GWP for N2O is 298.

    Now by your argument each molecule of methane emitted NZ farmers should get a credit of one molecule of CO2 since there is one carbon atom in each and we are supposing that that carbon atom came from recently absorbed atmospheric CO2.

    So if we take an amount of CO2 with the same number of molecules as 1,000 kt of methane how much would it weigh? It turns out that a CO2 molecule weighs 44/16 times as much as a methane molecule. (I’ve looked up the various atomic weights to get this.) So I make that 2,750 kt of CO2.

    So I should have said above that our overall liability would be around 37,668 – 2, 7500 = 34, 918 kt CO2 equivalent. Still a fairly modest reduction.

  4. Is 2,750 KT of Credit A Big Issue For New Zealand Agriculture « Dear John Says:

    […] Andrew D of the Physics Department at the University of Queensland has put much effort into his comments on my earlier post (please read them all).  He concedes that I have a point about the Kyoto rules but reckons I am […]

  5. Owen McShane Says:

    Presently carbon dioxide is at a concentration of 384 ppm by volume in our atmosphere.
    Methane is present at a concentration of only 1.7 ppm by volume.
    In other words there is 225 times as much CO2 in the atmosphere as CH4.
    If CH4 is indeed 25 times as potent a ghg as carbon dioxide then it is an equivalent concentration of 42.5 ppmv.
    Which means there is 9 times much CO2 as CH4.
    AS far as I know no one knows how many tonnes of increased CO2 it takes to increase global ave temp by 1 degree.
    But an equal number of tonnes of CH4 released will only have a tenth of the effect as CO2 but many keep suggesting it will have 25 times the effect. But this would be true only if both gases were at the same concentration, surely.
    Or am I missing something here?

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