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Comment by retrac98 | Hacker News Reader

How does animal agriculture affect this? Are there any authorities on the subject on HN? Everything I've heard suggests the greenhouse gas emissions in support of animal agriculture far outstrip those of pretty much anything else, but nobody seems to really talk about it.

Pre-empting a couple of replies here - I already don't eat meat, and yes I've seen "Cowspiracy". :)

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As far as I know, this issue is not comparable to our carbon economy, I.e. Natural gas extraction, coal mining, oil, etc. Key difference is that agriculture is a closed cycle, animals produce a lot of green house gas, but it's gas that's already a part of our ecosystem. When we did stuff from the ground we add new carbon to the ecosystem, and this feat is what's destabilizing the environment. I heard this argument from an interview Elon Musk did about agriculture after someone posted a tweet at him about the documentary "Cowspiracy".

> Key difference is that agriculture is a closed cycle, animals produce a lot of green house gas, but it's gas that's already a part of our ecosystem.

How is it a closed cycle? They require a lot of food and water to be grown, all of which has its own greenhouse gas cost to produce, and then they fart methane while they're alive and require more fuel to process/transport. All the while the world demand for meat is increasing pretty quickly, right?

But we do dig stuff from the ground for agriculture. Massive amounts of forestland are cleared, plowed, and massive amounts of inorganic NPK inputs are added. This releases enormous amounts of previously entrapped CO2 to the atmosphere.

It is comparable, and thinking about agriculture as a closed system is not even close to correct. We're mowing down natural carbon sinks to an insane degree to grow crops to feed animals, one of the major reasons of deforestation and land use change in South America, for instance.

And not only that, we grow slow-acting carbon and turn it into fast-acting methane.

I strongly doubt Musk would have such a simplistic view of agricultural emissions, they're a big concern for a reason.

Modern agriculture is part of the carbon economy, especially since the Green Revolution. Inorganic fertilizers are produced using coal and natural gas, and nitrogen-enriched fertilizers emit nitrous oxide, a greenhouse gas. These inputs were previously mostly sequestered.

This UN site says 5% of actual CO2 and 14% of CO2-equivalent emissions. Cow and pig production emit mostly methane and nitrogen oxide.

http://www.fao.org/news/story/en/item/197623/icode/

Doesn't methane have a much more powerful greenhouse effect than CO2 though?

Yeah, that's how the 5% becomes 14% equivalent in @jessriedel's numbers.

Yes but it breaks down into CO2 very quickly.

Pigs are actually a lot better than cows because they are monogastric. So we can cut CO2 emissions by eating more pork and less beef.

https://en.wikipedia.org/wiki/Ruminant#Ruminants_and_climate...

Even better, kangaroos (I know, I know, poor skippy...). Their digestive systems don't produce methane: https://en.wikipedia.org/wiki/Kangaroo#Absence_of_digestive_...

And I'm less sure of this, but I've heard that they cause far less soil erosion compared to cows, as their weight is spread out over a much larger area (i.e. they have big feet). Their populations in some parts of Australia have also reached unsustainable starvation levels, to the point where some State-level governments have initiated culling (i.e. licensed shooting of kangaroos, in a country with very tight gun-control laws).

Or how about not eating animals at all, since it's cruel and unnecessary altogether? Difficult mental and emotional leap for most people, I know.

Or at least, we should teach butchery to kids. That way, they'd know what it means to actually kill to eat. The only thing I've ever killed is a lobster, and it helps a lot to relate to what you have on your plate...

How about dropping the holier than thou attitude. I'm going to skip my vegetarian lunch today, just to spite you.

Animal ag can both be a carbon sink and a carbon source depending on management. Ruminant animals play an important role in grassland ecosystems for nutrient cycling, which can affect the carbon cycle and potentially sequester carbon in soil. Whether we eat the animals is another question. Check out Carbon Farming or Holistic Management for more details.

https://en.wikipedia.org/wiki/Environmental_impact_of_meat_p...

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