Opinion: Ruminants are no ‘bete noire’ for greenhouse gases

One abiding memory of finance lectures at university was that, despite more than two centuries of trial and error, accountants still regularly disagree on how best to deal with the relatively straightforward concept of financial accounting.

Given that the carbon cycle, with its legion of sinks, sources and byzantine biological systems, is vastly more complex than mere money, should we therefore not resign ourselves to the prospect that the planet will probably have been incinerated in a fireball of our own making, long before we get close to arriving at how best to account for who or what is responsible?

See also: Meat eaters or vegetarians – who has the better arguments?

At the moment the culprit is pretty clear to many of us… it’s cows of course; those uber-flatulent methane-belching machines, incessantly pumping their invisible, superheating evil into the atmosphere, while the rest of society neuroses over whether a Tesla or a Porsche Taycan better equips them to save the planet when negotiating the school run or the weekly trip to Waitrose.

Or is it? It is well understood that a molecule of methane, at any given point in time, has a significantly greater greenhouse effect than a molecule of common or garden carbon dioxide (although the latter, by dint of sheer volume of emissions, remains by far the most significant of the greenhouse gases).

The current calculation methodology used by the Intergovernmental Panel on Climate Change, known as GWP100, calculates the estimated global warming potential of different greenhouse gases over a 100-year timeframe, expressed as carbon dioxide equivalents or “CO2e”. This has led to cattle and other ruminants, a major source of methane emissions globally, being cast as the villain of the global warming piece.

However, while carbon dioxide persists in the atmosphere for centuries or even millennia, methane breaks down into carbon dioxide over a few decades, with a half-life of a little over 10 years, and so has a much less severe impact over time.

Furthermore the carbon dioxide into which the methane breaks down is effectively reabsorbed by the plants that provide food for ruminants, essentially creating a closed loop, as opposed to carbon dioxide from fossil fuels which remains in the atmosphere, simmering away indefinitely.

GWP100 does not fairly account for this and, as such, the demonisation of ruminants as the harbingers of environmental Armageddon persists.

But help is at hand in the shape of Professor Myles Allen and his team at the Oxford Martin School, who have proposed a more accurate treatment of methane and other short-lived climate pollutants, known as GWP*.

Recalculating the impact of greenhouse gas emissions using this more sophisticated yet fairer methodology fundamentally changes the global warming landscape and ruminant agriculture’s role within it.

If it is adopted as a credible alternative to GWP100, then UK agriculture, with its significant grassland and ruminant sector, can finally, by means of reduced emissions and consequently increased net sequestration potential, fulfil its role as part of the solution to climate change, rather than a major cause. This would help massively with the delivery of the nation’s “net zero” ambition.

This has potential major trade and economic, as well as environmental, consequences for the whole industry, so it is crucial, as the UK prepares to host the UN COP 26 climate change conference a year from now, that we rally behind GWP* and lobby for its adoption as a more equitable and rational approach to measuring emissions.