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Comment by ravenstine | Hacker News Reader

Or we can just have plants capture the CO2, give those plants to large ruminants which will feed those plants to the microbiota in their cecum, digest the microbiota and converting it into the kind of nutritious protein and fat that hominids have adapted to digest almost exclusively for millions of years.

If one is worried about the methane emissions of cattle, it's not really clear that this is even a secondary concern. The carbon that cows produce, whether it be methane or CO2, came from the atmosphere and is returned to the atmosphere. That is because cows are eating plants which derive their carbon primarily from the atmosphere. This is different from fossil sources of methane, which isn't atmospheric unless it's released. The isotope of carbon isn't even the same between bio-methane and fossil methane. The methane that cows release is oxidized after several years.

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Meat farming takes in CO2 (photosynthesis), and produces CO2 (cows breathing) and CH4 (cows farting). CH4 is a much more potent greenhouse gas than CO2, so, even by your flawed simplified model, farming cows has a net negative greenhouse effect.

So what if methane is more "potent"? How potent and in relation to what, and in what amount?

Large ruminants and other animals that produce methane roamed the Earth in greater numbers long before humans came up with the concept of livestock. Stable isotopes of carbon in atmospheric methane don't support livestock being a contributor to rising methane at all. Because livestock methane is part of the carbon cycle, and livestock aren't in greater numbers, problematic increases in atmospheric methane have to be coming from somewhere else, most likely things such as fracking. Carbon-14 would be increasing in the atmosphere if cows were responsible.

Even if we eliminated meat consumption, hypothetically speaking, it's totally unclear and unfounded that any meaningful difference would be made. According to the United States EPA, agriculture as a whole makes up 11% of greenhouse gas emissions in the United States. That percentage includes everything from farm to table, meaning that cows in particular make up a fraction of that since most of the greenhouse gas will inevitably come from transportation and processing. Methane itself makes up ~11% of greenhouse gas. Show me any evidence whatsoever that correcting for the greenhouse gas from animals bred for food will make any appreciable difference in changing the climate in the favor of humans.

By the way, most of the methane from cows comes from their burping, not farting.

> So what if methane is more "potent"?

If you are concerned about global warming, swapping one thing for something else that has a greater negative impact is bad.

Having a process or animal that converts CO2 to methane is not neutral just because the CO2 was already in the atmosphere.

> How potent

25x more.

> and in relation to what,

CO2 over a period of 100 years usually.

> and in what amount?

Any amount, it's a relative figure.

Doesn't methane break down much more rapidly than CO2?

Yes. And it turns into, guess what, CO2. And heat.

The 25x number already includes this effect. Methane is much much more potent than CO2, but since it breaks down rapidly then over the course of a 100 years the average effect is 25x.

So: if you first say "25x" then you cannot say "break down" afterwards because that is included in the 25x, you are then mentally including the breakdown twice.

There are also higher numbers in use than 25x that is used for the effect over shorter horizons. But 100 years seems like a good horizon for the humanity getting through the crisis or not.

Total emissions of 100% is made up contributions of 1%+1%+1%+...

By that logic there exists nothing that can help climate change...even if we are causing it.

A bit like saying "shooting this one plane down out of 1000 enemy planes does not win the war; may as well not shoot it and give up".

Yes, obviously if we had never touched fossil fuels, having even more lifestock than today would probably be fine too, but that is not very relevant.

CH4 has a half life of like 10 years or so, so even if you deleted all cows from the world right now, in 20-40 years you'd be back to "only fossil fuel CO2 causing climate change".

Furthermore, has CH4 from cows even increased historically? There are 30m cows in the US, compared to 60m bison 150 years ago.

2 things:

A common error about CH4 is misunderstanding half-life vs CO2e calculations. The half life is 10 years but that does not make it a non-problem; a commonly used number is that CH4 is 25 more potent that CO2 -- but that number 25x is OVER A 100 YEAR LIFESPAN that already INCLUDES the decay over those 100 years. So if you mention that half year is 10 years you also throw the number 25x out the window, then the multiplier is much much larger (forgot how much). Because of this scientists use different potebtial multiplier for CH4 for different time horizons. Anyway it IS a problem to have CH4 instead of CO2, how big a problem depends on your time horizon and over 100 years CH4 is 25x worse than CO2 INCLUDING decay.

You touch on the second point already. As long as lifestock is constant, CH4 is constant at a certain level. Still: Reducing lifestock will reduce CH4 to a lower constant level which will reduce greenhouse effects as CH4 decays to a lower stable level where emission and decay balance.

In a sense, reducing lifestock is the same as CO2 capture -- not the same as stopping to burn fossils.

My understanding is that CH4 breakdown in the atmosphere isn’t a matter of exponential decay either but is (or could become) rate limited by OH radical availability. Such that the half life increases as more is in the atmosphere and it’s possible to totally outpace the breakdown even at constant emissions.

https://en.m.wikipedia.org/wiki/Atmospheric_methane

It's not farting, it's belching. Can be ameliorated adding algae to the feed.

It's not very relevant to the point you're making in this case, but it's good to be precise and also might help you revisit your sources if you just didn't misspeak. https://climate.nasa.gov/faq/33/which-is-a-bigger-methane-so...

https://www.industry.gov.au/data-and-publications/from-beach...

Also poop.

> Or we can just have plants capture the CO2, give those plants to large ruminants which will feed those plants to the microbiota in their cecum, digest the microbiota and converting it into the kind of nutritious protein and fat that hominids have adapted to digest almost exclusively for millions of years.

The time involved, from capture by plants to a grown up mammal are very long. The space this very elegant self-replicating organic machines take is also enormous. You can cut the process in half and get proteins and carbs directly from plants, but we have known that for ages and, even with the future of our species at stake (no pun intended) we still haven’t changed our diets.

That's right that cow farts don't contribute anything to climate change. Some sources quote the methane cattle emit as if it was significant but it isn't because the environment can handle it. In truth, the emissions from farming that the environment can't handle come from "land use change". That's the land that's deforested and turned into cropland to feed cattle.

But that's a big problem and not one to be underestimated. We are tearing down the ability of the environment to capture carbon, one hectare of forest, let alone rainforest, at a time. That has to stop. And that means cutting down on meat production.

That's not to say we should stop producing and eating meat. That'd be just risking malnutrition on a planetary scale.

I'm also not sure about the bit where you say "hominids have adapted to digest almost exlusively for millions of years", where you mean meat. We're omnivorers and we are "adapted" to an omnivore diet: a little bit of everything. Eating only meat is as braindead as eating only plants. We need a balanced diet to stay healthy.

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