Meat, greenhouse gas emissions, and the grass-fed fallacy

In this edition of the BBC Radio 4 programme Inside Science - first broadcast BBC Radio 4 on 17th November 2016 - the question of meat's contribution to climate change is discussed after in the previous week's broadcast a climate change scientist confirmed that being vegan would reduce your carbon footprint by 50% compared to eating meat, and people wrote in to question this (even though the scientist did explain why it is so).

The questioning comments suggest that grass-fed meat is better in terms of greenhouse gases - this is disproved in this programme, as well as how relying exclusively on grass-fed meat would effectively ration meat to unacceptable levels (see inhumanitarian).

The full programme is available to listen to here: https://www.bbc.co.uk/programmes/b08296jm

This transcript picks up at 15m51s into the broadcast:

Adam Rutherford (presenter):
"More on the continuing theme of climate change now.
- we had a whole bunch of emails from your lot, particularly on the suggestion that going vegan vegan radically reduced your carbon footprint. I spoke to Oxford's Pete Scarborough last week - he told us a meat-heavy diet resulted in twice as much warming emissions as a vegan one.

"But a number of you challenged this, saying that it surely only applied to animals given feed based on soy and maize, crops grown specifically for animals.

"Esther Clark wrote in and asked "Is it OK to eat meat as long as its grass-fed?".

"Andrew Cook from Bristol University suggested that the global figures might be misleading locally as most cattle in the UK are grass-fed, unlike in the US, and that maybe eating different meats should be encouraged rather than simply eating less meat.

"I asked Dr Tara Garnett, a food sustainability scientist from Oxford University to paint us a more details picture."

Dr Tara Garnett:
"The big picture is that livestock as a whole are approximatley 15% of global greenhouse gas emissions, and ruminants contribute to about 80% of that total. So that's the starting point, and the reason those emissions arise are largely from methane emissions, nitrous oxide, and those are present in the atmosphere in much smaller concentrations, but they're much more potent so they kind of hit harder. And then carbon dioxide and that arises from livestock-induced land-use change. So every time you clear a forest in order to rear livestock that contributes to livestock emissions total.

"So then you start to think about, okay, so how are different ruminents..how do they have different impacts? And, put very very simply, animals reared on grass, because they grow more slowly, but they're still busy "living", as it were, they emit more methane per unit of weight gain or per unit of milk produced. And because methane is very potent, their overall greenhouse gas footprint, which is a composite of all those different gases, is going to be higher per kilo of meat or milk produced, than animals in intensive systems that are fattened up on grains - its more digestible it helps them be reared more quickly."

AR:
"So animals in the UK for example that are raised in pastures, on grass, are actually producing *more* methane as a greenhouse gas than intensively farmed ones that are fed on maizes and soya?"

TG:
"Yes, but that's not the only consideration. That's the starting point. The starting point is that livestock in intensive systems per unit of meat or milk produced tend to have a lower footprint.

"Now that leaves aside all sorts of issues around animal welfare that are extremely important, but that I'm not going to go into now because that's not the focus of the discussion.

"However, we also have to take into account the fact that animals that eat grains are eating foods that could concievably be eaten more efficiently and more directly by human beings; that the production of those grains can have negative environmental consequences, which tends to be factored in to the overall carbon footprint of the livestock product, so that tends to be included; and most importantly I think is the argument that grass-fed animals can make use of land that can't be used for other forms of food production, and also that they can consume coarse agricultural by-products that you pass them through an animal and you get something out of nothing, effectively. And those are the traditional functions of ruminants."

AR:
"OK, so, I'm going to try to simplify this a bit, because obviously its an immensly complicated story, and so far we've just kind of scraped the surface, but is the bottom line that if as a society or individuals we just eat less meat then sticking with grass-fed, pasture ruminants would be better for greenhouse gases even though on average those cows produce more methane than those fed on maize and soya?"

TG:
"Yes, you could probably say that. To give you an example there has been some research that's actually considered the world of nine billion people which is where we're heading in 2050 and looked at what would happen if we just reared animals on grassland and just fed them byproducts that weren't linked to soy, maize or anything else. And what it finds is that you get about 26 grams of meat per person per day. That's meat of all kinds: if its ruminents' meat its about 19 grams. Now I'm not sure if you can imagine 19 grams of meat, but its very very little."

AR:
"It's not much. It's smaller than a burger isn't it?"

TG:
"A kind of meesly bought burger is something like a 100 grams, and that's the really small ones. Um, also milk, we have to remember milk, that's 138 grams of milk per person per day. That's the milk you put in four cups of tea. It's a lot less than a capuccino or a latte. And that's before you've had your cereal.

AR:
"OK, so we're talking about one meat ball and four cups of tea. How do we encourage people to adopt this radically different anti-British lifestyle?

TG:
"I think that's a whole different programme! It would be fascinating to do.

AR:
"Tara Garnett from the Environmental Change Institute in Oxford. Thank you for all your emails, do keep them coming."

(21:34)