The methane issue is far from settled

Big methane decisions lie ahead that will affect all New Zealanders

In late May, the eleven rural-industry partners in He Waka Eke Noa (HWEN) reached internal compromises that were sufficient for all to sign-up to a joint greenhouse gas (GHG) document, which laid out the bones of how they think agriculture’s greenhouse gases should be priced.

It went right down to the wire before Federated Farmers agreed to add their logo.  Some of the other partners to the document were also less than happy, but the alternative of failing to come up with an agreement at all was even less palatable.

Now it will be up to the Government, taking account of forthcoming advice from the Climate Change Commission (CCC), to make some calls as to the path forward.

The Government does not have to accept the HWEN recommendations. Nor does it have to accept the advice of the CCC. But if it does not accept CCC advice, it is required by legislation to give reasons.

My bet is that there will be robust discussions within Government. There are some within Government, including senior members, who understand very clearly that they must not destroy agriculture. But there are also elements within the Government who are fundamentally antagonistic to New Zealand agriculture as currently structured.

One of the key reasons for antagonism towards New Zealand’s agriculture is serious misunderstanding as to the importance of primary industries in general, and pastoral agriculture in particular.

This lack of understanding is fed by the crazy way that we measure the importance of the agricultural sector in New Zealand. This starts with the measure of GDP, whereby agriculture supposedly makes up in the order of five percent of the economy.

This GDP measure is limited not only to what happens on-farm, ignoring everything before and past the farm gate, but it also includes only part of what happens on-farm.  For example, shearers are not part of the sector. Nor is any contractor that comes onto the farm to plant a crop, make hay, make silage, or apply fertiliser. Nor are veterinarians or other farm-related professionals such as accountants. They are all part of the service sector outside agriculture.

Given the way the statistics are published, the only way to understand the importance to New Zealand of the land-based primary industries is to look at exports. More than 80 percent of New Zealand’s merchandise exports come from the primary industries. According to MPIs latest SOPI document, the pastoral industries by themselves are expected to earn $33.8 billion of export income for the 2021/22 year just ending. Where else can those earnings come from to pay for all the imports?

Unfortunately, most of the urban community does not understand that there are good ecological reasons why so much of New Zealand’s farming lands are pastoral. The combination of topography, soils and maritime climate determines that situation. If it were more profitable and ecologically sustainable to grow a lot more crops, then farmers would already be doing so.

The ‘bottom line’ arising from this situation is that New Zealand has responsibilities to itself, and also to others through the Paris Agreement, to protect food production.  However, that does not let New Zealand ‘off the hook’ from having to minimise greenhouse gas emissions whenever it can do so consistent with its food obligations.

Returning to the HWEN issues, I expect there will be relative quiet in the media for the next few months. In part this will be because of the economic storm now descending upon the country and taking everyone’s attention. Beneath the surface, there will still be lots going on. It will only be a pregnant pause as the Government figures out how to proceed.  Every Government member will be aware that the months are ticking by to the next election.

It has long been clear that many people on both sides of the farm gate hold fixed positions as to how agriculture should or should not be charged for its emissions. However, few people have a genuine understanding across the issues. Given the fixed views, it is very hard to hold a rational discussion and deal with some of the mis-information.

Here I will step back to try and put some structure around those issues.

There are two gases of major concern within agricultural systems. One of these is methane which is produced in the rumen of cattle, sheep, deer and goats. This methane is burped out as a natural by-product of grass digestion. The other gas is nitrous oxide, formed in the soil from the dung and urine these animals excrete from their other end.

Here I focus on methane, which gets most of the media attention. However, nitrous oxide is also important. That will have to wait for another article.

When human society first started thinking seriously about greenhouse gas emissions some 30 years ago, there was an almost total focus on carbon dioxide. Accordingly, when the focus subsequently widened to include methane, it seemed convenient to express this in so-called units of ‘carbon dioxide equivalence’. We have been stuck with that convention ever since.

The problem with carbon dioxide equivalence, written as CO2e, is that it is like trying to compare apples to oranges, or lemons to peaches. How many apples does it take to be equivalent to an orange? Do we mean by weight? Or by sugar content? Or by Vitamin C? Or some other unit.  Each criterion provides a different answer.

Well, it is the same when comparing methane to carbon dioxide.  Except that the key question there is the time period of the comparison.  This is because of the very different length of time that carbon dioxide and methane remain in the atmosphere.   Should we use 20 years, 100 years or 500 years as the basis for comparison?  The focus to be placed on methane within climate-change policy is very much dependant on the answer to that question.

If we say that a 100-year time frame is important, then the warming caused by a tonne of methane is equivalent to approximately 25 tonnes of carbon dioxide.

Conversely, if the focus on the warming created over the next 20-years, then the so-called damage caused by a tonne of methane equates to about 85 tonnes of carbon dioxide. This is the period when methane does most of its damage.

However, if we extend our time horizon to 500 years, then the warming created by emission of a tonne of methane is equivalent to emission of about ten tonnes of carbon dioxide.

Scientists refer to the average time that methane remains in the atmosphere as its ‘atmospheric residence time’. Scientists are still refining their knowledge of this, but the latest IPCC figure is 11.8 years.   That means that approximately half of the warming effect of methane emissions occurs in the first 12 years with the remainder occurring thereafter. By 100 years, well under one percent of the original molecules will be present. For those who are mathematically inclined, it can be approximated by a first order decay function.

In contrast, the scientific consensus is that carbon dioxide emission entering the atmosphere now will still be causing elevated levels of carbon dioxide in the atmosphere many hundreds of years and possibly thousands of years from now. The maths of carbon dioxide removal from the atmosphere is particularly complex and there is still lots to learn.

One of the features of New Zealand agriculture is that methane emissions have been approximately constant for more than 20 years. This means that the cloud of NZ-sourced methane is approximately in balance, with newly released methane approximately balancing methane decay.  There are some who therefore argue, and do so vociferously, that farmers should not be charged for their emissions as long as this balance is maintained.

When I started writing this article, I had planned to say a lot more about the above argument, including both its strengths and weaknesses. But that will have to wait for another time. What I will say here is that although the ‘atmospheric balance’ argument can be and should be an important part of the debate, there are also important counter arguments that need to be acknowledged as to why it does not let agriculture ‘off the hook’. I can see another article coming up on that issue alone.

A key point about converting methane to carbon dioxide equivalence is that it depends not only on science. It requires a value judgement as to how we weight the importance of the very long-term future compared to the nearer term. And should New Zealand farmers be ‘grandfathered’ and therefore allowed to continue the farming of methane-emitting animals as they have always done?

Well, that is indeed enough for this article. But alas, I have only scratched the surface. A final point that I do want to emphasise is that methane debates must start with a basic understanding of the science. But that is just the start. The debate also requires value judgments as to what is important, what is fair and what is reasonable. Within that framework, there is no absolute right and wrong.

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