Methane - it’s all sorted, isn’t it?

Anyone who has a vague interest in climate change knows all about the methane story! Methane is a potent greenhouse gas, one of the worst and it’s all produced by burping ruminants - get rid of those and the problem is sorted, isn’t it? Except of course, it isn’t that simple; the devil, as ever, is in the detail.

Methane is undeniably a very potent greenhouse gas, approximately 25 X as potent as carbon dioxide (CO₂) in its warming potential, when using one common metric. It is not the most potent of the common greenhouse gases, nitrous oxide wears that crown; and it doesn’t last that long: half the methane produced in any one year will have been broken down in 8 years or so, whereas CO₂ persists for hundreds of years. And that introduces the first element of confusion. How do you compare two very different molecules?

The standard methodology of measuring the equivalent amount, compared to the CO₂ Global Warming Potential on a 100 year period, (GWP 100 CO₂ e ) isn’t very fair on methane with its shorter half life. So alternatives are suggested, the most prominent of which is GWP*, with GWP20, based on a 20 year period, also a strong contender.  But it is clear that methane measurement is not yet sorted: the technical debate continues.

Farming systems vary considerably throughout the world and it is undeniable that cattle account for a significant proportion of man-made methane outputs, about 7% from one recent estimate¹. The average dairy cow in Africa produces nearly 20 times less milk than her equivalent in the USA. They won’t be producing the same amount of methane of course; they will be consuming very different diets, in that both quantity and quality will differ, and their body weight, rumen microflora and genetics will be similarly variable. But they will both be producing methane. How do we best compare their outputs? 

Some of the methane will relate to body maintenance requirements, the remainder links to production. Scientists commonly compare them on the basis of intensity of production i.e. methane produced per litre of milk (or per kilo of beef) and then makesweeping, and usually unfavourable comparisons, to rice or soya beans. But they are hardly comparing apples with apples and should they not be considering more than the methane output?  Maybe the impact on biodiversity, or social aspects, or the nutrient density or the total life cycle contribution would be a more valid basis? The recent publication from the Sustainable Food Trust² provides an alternative view on this complex area. The interspecies comparison of methane output is not totally sorted.

Diets fed to cattle will vary in their digestibility but what is certain is that a significant percentage, at least 30%, will pass through and be excreted as faeces. What happens next will depend on the intensity of the farming system. Are the cattle housed or free range? How is the manure stored? Can it be captured and used as biogas?  How and when is it returned to the soil, thus providing valuable nutrients? To what degree are the faeces sequestered into the soil, which is itself a complex biological system. There are many variables here, and there is much left to understand about the impact of various farming systems upon the carbon footprint of the farm. So this aspect of the carbon cycle, of which methane is an important component, is not sorted yet. 

And of course more intensive systems, relying as they do on the feeding of grains and by-products, which are generally not fit for human consumption, will produce more milk (or beef) but carry a higher carbon footprint. The intensity of methane production will differ- which is best? I’m sorry, that argument is not totally sorted yet!

So maybe the world should just get rid of cattle? In the western world animal agriculture, thanks to some powerful lobbying from other interested parties, enjoys a fairly negative press. But this comfortable view undervalues the growing need for quality animal protein in a world population which is projected  to grow: the UN estimates that milk consumption will rise by 17% over the next 8 years.¹

Global cow populations will probably grow to meet this demand - can we reduce their methane output per head or per litre? Raising the level of production, by improved feeding and genetics, will certainly help here. There is much potential for cattle in poorer countries to increase yields to volumes much nearer that of their richer neighbours. 

In addition, much scientific endeavour currently aims to mitigate methane production, whether by genetic selection or the introduction of compounds which reduce methane output. Trials of boluses and feed additives show considerable promise but will their impacts be sustainable long term, and what will be their individual carbon footprints? You’ve got it - not sorted yet! 

But when it is sorted, because of the potency of methane as a greenhouse gas, there is considerable potential for a small drop in methane emissions to start having a net cooling effect. Imagine how that story will run in the popular press ; “Cows Cool Climate!"

This simple review of a complex situation has surely established a few certain, sorted facts? 

• Every farm, every production system, will be a little different. 

• Every molecule of methane, no matter how measured, will be important?

• Every study, every opportunity to learn something, will contribute to the ultimate solution. 

• Every approach matters!

At VetSalus we remain convinced that, while the methane situation is far from sorted, there is a lot of positive progress being made and that our consultants and educational programmes have an important role to play.