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Let me be straight up. I'm a physicist, I've no doubt about climate change and the part we play in it. I had been reading about cattle being one of the alleged main causes of climate change.

I get that they make methane, and we have a LOT of them, So I ran some numbers:

Roughly 93 million cattle in the United states in 2017 (some sources claim lower, but I'm going with the higher one).

Prior to humans killing the Buffalo off, there were approximately 50-100 million of them across the united states.

A quick Wiki search, estimates that buffalo (bison) produce significantly more methane than domestic cattle (though I don't know for sure that this is true).

These numbers seem to match up pretty well insofar as they're greenhouse gas contributions, so now I'm wondering if the argument is viable? I know there were other herds around the world too, so I just found myself rather curious. Has anyone run the numbers thoroughly?

On the flip side, I could see the sheer number of humans being an issue, I'll try and run that later.

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  • $\begingroup$ it is mosly the type of food cows get that is to blame for the extra methane they produce,for cows to keep on producing milk they get more than only grass and water.tests where i live have shown it is possible to reduce the release of methane by up to 30% by feeding a salt water algae to the cows to replace the soy and grain they gets now. $\endgroup$ – trond hansen Feb 28 at 5:56
  • $\begingroup$ This Twitter thread is very relevant. $\endgroup$ – Gimelist Feb 28 at 11:39
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    $\begingroup$ It is not only the methane. The cattle have to eat something. In Germany, where I live, a lot of soy is imported from other regions of the world -- e.g. South America. There, rain forest is destroyed in order to obtain land for soy production. Additionally, most of the soy is produced by modern farming techniques (e.g. by industrial fertilizer production), which cause higher CO2 emissions than organic farming. Moreover, one needs more than 3 kg of feed to get out 1 kg of meat (there are numbers of 8:1 floating around; not sure if they are correct). Hence, we get a lot of secondary emissions. $\endgroup$ – daniel.neumann Feb 28 at 15:08
  • $\begingroup$ Please be aware, that there are a lot _wiki_s available via the internet. Neither in this wiki (foswiki.org/System/WebHome) nor in that wiki (jedipedia.net/wiki) I found any information on bisons ;-) . $\endgroup$ – daniel.neumann Feb 28 at 15:11
  • $\begingroup$ But the fact that buffalo did contribute to warming in the past doesn't mean that cattle's contribution today should be dismissed. $\endgroup$ – Camilo Rada Feb 28 at 20:42
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Let's just talk about cattle here and ignore other factors related to cattle production for now.

The current cattle number (93 million) you found is probably the total number of dairy cow and beef cattle. In your argument, it is possible that bison has much more emission than cattle on pasture. But the emission from cattle in feedlot and dairy farm is much larger than the cattle on pasture because of their diet chosen by us (human).

Typical beef cattle (steers and heifers) in the U.S. spend one year on pasture, and 5-6 month in feedlot before slaughter (unlike Argentina beef cattle which are fully raised on pasture). In feedlot, these young cattle (yearlings) are intensively fed with high protein feed in order to get them fatten up in a very short time. The U.S. dairy cows spent most of their time on dairy farm (unlike the Swiss cows who are raised on pasture). They live for about 5 years and are continuously fed with high protein forage to ensure their milk production. Both beef cattle and dairy cows have a high protein diet that result in high emission of methane (the impact of methane is 25 times worse than co2 in terms of warming).

The closest comparable cattle to bison is beef cow which spend most of its life time (about 10 years) on pasture and are only occasionally fed with low quality hay when there is a shortage on pasture. But again, the life span of a beef cow may be different from the buffalo and beef cows may eat more because they are basically pregnant very year(!).

California has this new policy that tries to cope with dairy cow methane emission from their manure. If you are interested, there is a recent study done by University of California Agricultural Issue Center here (https://aic.ucdavis.edu/wp-content/uploads/2019/01/DairyManure-1.pdf).

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  • $\begingroup$ Thank you! I have also come across an article about Canadian beef producers looking into genetically modified stomach flora to reduce emissions. I suppose we could fit each cow with some kind of catalytic converter (: $\endgroup$ – R. Rankin Mar 2 at 22:24
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There have been a few papers published on that topic. Johnsons & Johnson, 1995 for example estimate the amount of methane produced in a ruminant livestock to be 250 - 500 L/day. They conclude that cattle will contribute to little less than 2% of the global warming that we might face in 50 - 100 years time.

In contrast in a paper by Oliver et al., 2010 the authors looked at the per person CO2 emission of cruise ships traveling from and to New Zealand. The found that:

Emissions factors for individual journeys by cruise ships to or from New Zealand in 2007 ranged between 250 and 2200 g of CO2 per passenger-kilometre (g CO2 per p-km), with a weighted mean of 390 g CO2 per p-km. The weighted mean energy use per passenger night for the “hotel” function of these cruise vessels was estimated as 1600 MJ per visitor night, 12 times larger than the value for a land-based hotel.

As you can see cruise ships are probably far more of a „global warming machine“ than cattle - but serve only very few people. I personally think (and I might be wrong with this) that methane production in cattle can and is easily used by political groups to fight against the conditions in which the cattle are held and against the massive consumption of meat.

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    $\begingroup$ When it comes to answering the question, you're right. Still, the methan contribution to climate change isn't the only factor steming from cattle, you'd have to take into account the production of fodder, transportation, etc. Plus, yeah, the ramifications for human health, which ain't that great. $\endgroup$ – Erik Feb 28 at 13:07
  • $\begingroup$ I don't see how you can compare cattle and cruise ships, based on the figures that you have used. $\endgroup$ – Semidiurnal Simon Mar 1 at 10:30

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