Any carbon emissions tax charged or credit given should be on the net balance of an activity not just one side of it. To tax only emissions with no credit given for carbon sequestered is unfair.

All policy decisions seem to be based on the emissions and not the net contribution to total greenhouse gases by pastoral farming.

A milking cow each day eats 7kgs of carbon in the grass. 25kgs of CO2 were removed from the atmosphere to produce that carbon – CO2 is 28% carbon.

Each day, she emits, as a byproduct, 300 to 500gms of methane. Methane breaks down to CO2 and water after eight to 10 years, so the methane a cow emits does not add to the methane in the atmosphere, it simply replaces it. The methane becomes CO2, which becomes grass which the cow eats. It all goes around and around, so there should be no tax to pay.

Even if we follow the Kyoto Rules and assign a value to methane emissions of 20 times CO2 then the 300 to 500gms of methane equate to 6 to 10kgs CO2. The cow has removed 25kgs of CO2 from the atmosphere and emits 6 to 10kgs CO2 equivalents in methane. She is in credit between 15 - 19kgs.

In order to quantify the cow’s effect on greenhouse gases we need answer these questions:

* What happens to the 25kgs of CO2 the cow removes each day from the atmosphere in the grass she eats?

* How much is returned as CO2 to the atmosphere in respiration?

* How much is returned as methane to the atmosphere?

* How much is sent overseas in milk products? This carbon is a credit to the cow and the New Zealand farmer. If the carbon is eventually released to the atmosphere from an overseas country then that country should pay. In the same way, we in New Zealand will pay for emissions from a product produced overseas, namely oil.

* How much of the carbon in the cow’s faeces is absorbed by the soil and therefore removed from the atmosphere (a credit to the cow) and how much is returned to the atmosphere?

Present policy presumes it is all returned to the atmosphere simply because no one knows how much is incorporated in the soil. Ignorance is no excuse here; a fair tax cannot be imposed until this research is done. Who is doing that?

Before we can know the role pastoral farming plays in greenhouse gas emissions we need to know the answers to these questions.

If all the research has not yet been done then no one can know these answers.

Such research may eventually find that soil carbon levels increase in a pastoral farming situation for a number of reasons, including animal faeces becoming incorporated into the soil.

With that sequestration of carbon, and the carbon sent overseas in milk products taken into account, it may well be that farmers could be entitled to huge payments in carbon credits.

My rough estimation based on all the carbon in faeces returning to the soil (I know I said ignorance is no excuse but if it is good for the goose it is good for the gander) is that nearly one tonne of carbon is sequestered each year per cow.

On the issue of nitrous oxide emissions there also needs to be an accounting of the nitrogen taken from the atmosphere by clover etc.

Because N2O stays in the atmosphere for 300 years it is not as straightforward and much research needs to be done to quantify emissions before a tax can be fairly levied.

Some research in New Zealand quantifies that less than 1% of nitrogen from urine is emitted as N2O. Some overseas research quantifies it closer to 2%. This will need to be determined before a tax can be levied. Who is doing that and when will it be done?

Any breakdown of vegetation can produce N2O and all activity that causes this should be taxed, not just pastoral farming. Eg, some biofuel production, forestry, native bush, wetlands and composting all produce N2O emissions as, indeed, do we humans.