Photo: Getty Images
Photo: Getty Images

ScienceMarch 3, 2018

The two things you should know about methane

Photo: Getty Images
Photo: Getty Images

In New Zealand, as in the rest of the world, the climate change conversation tends to focus on fossil fuels and renewable energy. But, asks Kieran Martin, when methane in the atmosphere can do far more damage than carbon dioxide, shouldn’t we thinking harder about cows?

When it comes to fossil fuels we know what to do: stop extracting the stuff from the ground and use renewable energy. We will argue about the implementation of different solutions, but we understand what they are. Less coal and oil, more wind and solar, and lots of electric vehicles.

But when it comes to cows and sheep, things are less clear. Since Shane Ardern and Myrtle the tractor mounted the steps of parliament in 2003 to protest the idea that a cow’s wind could contribute to global warming, the ‘fart tax’ has been a running joke in New Zealand. And that’s not really surprising – emissions from cows seem to make no sense. Where does the cow get the carbon? She doesn’t extract it herself. We don’t feed her coal or oil. She is part of a cycle. So why should we include her in our list of emissions?

Now, 15 years since Shane and Myrtle’s protest, methane emissions from livestock make up one third all New Zealand’s carbon output. By now, everyone should know the answer to these questions. Just in case you don’t, let me fill you in.

Cows don’t add more carbon to the air; they amplify the effect of the carbon that is already there

Grass-eating mammals cause a transfer of carbon from carbon dioxide (CO2) to methane (CH4). Methane traps far more heat than carbon dioxide.

Methane breaks down in a human timeframe – and that’s a huge opportunity for change.

In the first 20 years, methane is 80 times more potent than carbon dioxide. Over 100 years that drops to 28 times. If the volume of livestock were to remain stable for long enough, the rate of methane leaving our atmosphere would match the pace of methane arriving.


These two facts about methane are not controversial. There are around two kilos of livestock for every kilo of human on this overcrowded planet, and we’ve measured their emissions for years now. We have a reasonable idea of the volume that goes into the air, and we can observe its behaviour.

The climate change discussion sticks mostly to carbon dioxide because the issue with fossil fuels is more urgent. The attention will shift to livestock though, because while the diminishing returns of methane make it less urgent, the warming is very significant. Globally, the impact of livestock on global warming could be as high as 23%. Transportation is around 14%.

And so the arguments begin. Since, as noted by the research institute Motu in their report for the Parliamentary Commissioner for the Environment (PCE) [PDF], the warming effect of methane stops increasing if livestock numbers remain stable for long enough, there is a case for keeping cows around. You wind up with a quota of sorts; too many cows and you’ve consumed more than your share of the carbon budget. Fewer cows, and warming could decrease.

Once you know this the thought experiments can get started. What happens if the world agrees that it’s too hot and something drastic needs to be done to lower temperatures? Trees help a little, but they have to remain where there are (when wood burns or decomposes the carbon returns into the air). Stopping CO2 emissions can’t lower temperatures since CO2 is stable for hundreds of years. Carbon sequestration technology doesn’t work at scale. Geo-engineering is crazy. But reducing livestock causes methane levels to drop.

In New Zealand the focus has been not on reducing livestock, but on finding ways to reduce their emissions. This is much needed work; there will always be a market for the genuine product. But it’s a terrifically tough nut to crack since it attempts to alter the very thing that make grass-eating mammals what they are: the rumen. The fermentation process in the stomach’s first compartment evolved to create methane. The reverse-engineering required to stop that process sounds as complex as coming up with a way to ferment milk from plants yourself. Which is also happening.

What happens when synthetic meat and milk appear at scale and of quality to replace hamburger meat and milk powder? If those products also compete well on price or emissions (it is likely they will do so on both), then the food revolution has just taken another leap. A market for the real thing will remain, like the market for paper books, vinyl records and cigarettes you can light. But it won’t be like this market. The voices that claim people will never accept these new foreign substitutes sound eerily like the ones that dismissed the Toyota Corolla in the 1970s.

Of course the pressures on this industry largely depend on one accepting the global consensus about methane’s effect as a greenhouse gas and the volume of emissions from ruminants (grass-eating mammals). But why would you, when the National government didn’t include it at Paris and was still making fart jokes at the end of the last election campaign? Politicians, talk show hosts, journalist and broadcasters are frequently dismissive about climate change in New Zealand media. The occasional scientist can be expected to chip in with their own misgivings. Methane is seldom discussed, even in media coverage that supports climate change.

One person who responded to the PCE report is farmer and writer Robin Grieve. His site, contains an analysis of the PCE report which concludes that its authors had made errors, and that methane does not contribute to global warming. Of course he is wrong; one of the report’s co-authors wrote a Herald article to let him know that. Still the story persists.

Grieve is by no means alone in his petitions to the agricultural sector. Soil scientist Doug Edmeades is a popular speaker and writer in that field, and he too disputes the global warming effect of livestock. His views go a little further: he claims that climate change itself is a hoax. His paper, much like Grieve’s, carries a scientific bearing. Still it is just a blog post; neither article was subjected to the scrutiny of climate scientists.

For anyone wanting a reason to not worry about climate change, ‘un-information’ often serves just as well as misinformation. What I call ‘un-information’ is the old real estate tactic which can be summarised as “since I’m obliged to tell you what I know about this subject I will learn as little as possible”. Media pundits Leighton Smith, Mike Hosking and John Roughan have informed us that CO2 is not toxic, people who can be bothered should simply plant a few trees to fix the problem, and that 2017’s extreme weather wasn’t too bad.

Half an hour is probably enough for someone with internet access to learn the basics about the carbon cycle or the extreme weather events in 2017. That would be enough time to see how hopelessly uninformed these pundits are when it comes to the most significant change humans have ever made to their environment. Their take on the subject is so superficial it resembles a cricket commentary performed by someone who does not realise the game requires a ball.

The commentary is bad, but where are the howls of disbelief? We voted for our generation’s nuclear free moment, yet while uranium is alien and hard to like, oil is quite the reverse. Think of an event you’re saving for now and see whether it doesn’t involve a sudden increase in carbon emissions. People don’t want to think about this crisis, yet, unlike Y2K, the Cold War and the ozone layer, this one implicates them directly; it won’t happen on their terms.

Globally the issue is about fossil fuels, transport, industry and electricity. These things apply to us too, but here nothing is more intractable than livestock. If we allow ourselves to misunderstand the basics of methane we won’t be able to plan. If we discard the facts we won’t even be able to discuss the problem. We’ll end up wondering why the scientists are wasting their time on climate change, leaving no one to find out what happened to the weather.

Kieran Martin is the host of Imagine My Relief, a podcast conversation with New Zealanders trying to address climate change both here and around the world.

The Spinoff’s science content is made possible thanks to the support of The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.

The Spinoff’s science content is made possible thanks to the support of The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.

Mad Chapman, Editor
Aotearoa continues to adapt to a new reality and The Spinoff is right there, sorting fact from fiction to bring you the latest updates and biggest stories. Help us continue this coverage, and so much more, by supporting The Spinoff Members.Madeleine Chapman, EditorJoin Members

Get The Spinoff
in your inbox