It's more complex than that since if we're talking about land use or calorie production since most livestock is grazed on marginal crop land and would need to be compared to that of the palm trees.

The appropriate way to calculate efficiency might to be separate out the rendered tallow from a nutrient-weighted food output (today, we don't actually have a calorie shortage, but we are definitely nutrient deficient) and an life cycle analysis of all the inputs.

In terms of other aspects of environmental footprint, it also depends a lot on how the animal was raised. While conventional beef might be 30+ kg CO2eq/kg, full LCA has shown regenerative beef can be net negative (due to soil carbon sequestration): https://blog.whiteoakpastures.com/hubfs/WOP-LCA-Quantis-2019... Water footprint also is similarly nuanced and needs to be split into green/blue/grey water.

> most livestock is grazed on marginal crop land

There's a lot to unpack there. What is "marginal crop land"?

It conjures images of scrubland in the North American west or the African savanna. But more than half the cattle in the world live in Brazil and India. My understanding is that rainforests take up so many nutrients that the soil is actually very poor and unsuitable for most kinds of agriculture. So one could easily say that recently burned Amazon rainforest is "marginal crop land", and that would make this statement technically true while still being no consolation at all.

The next biggest chunk of the earth's cattle live in China, where my understanding is that they're effectively creating their own "marginal crop land" - they graze, they take up the nutrients in the soil, then they're slaughtered and their meat is shipped overseas, taking those nutrients along with them. So the soil keeps getting less fertile. Grazing is supposedly a major factor in the expansion of the Gobi desert.

The USA? I don't know. Perhaps all the biggest CAFOs are located in marginal crop land, but the grain they're feeding to the cattle is all grown on prime crop land.

Perhaps some specialty farms are creating eddies in the current, but it's hard to see much evidence that they're changing the overall flow unless we're very careful about how we frame the conversation.

In North America, cattle are grazed on grasslands which have a long-term symbiotic relationship with grazing ungulates (the buffalo, now mostly gone, an immense tragedy). Cattle are only grain-fed for the last few weeks of their lives. There's this standing myth that cattle spend their lives in feedlots and that's simply false, as a visit to any ranch will tell you. And even that feed is largely inedible by humans[0].

The analogy between modern cattle and the wild grazing of buffalo isn't perfect. There are problems with modern grazing that need to be addressed. The North American grasslands are prone to desertification if over- or under-grazed. The work of the Savory Institute is largely about promoting "regenerative grazing", not just in North America but also eg Africa[1].

Anyway, if you live in North America and eat/utilise relatively local beef, then you aren't a participant in some kind of misuse of "prime crop land".

[0]: https://www.cgiar.org/news-events/news/fao-sets-the-record-s...

[1]: https://savory.global

It's even more complicated than that, because large parts of Brazil are pampas or other dry lands, where grazing cattle is the most suitable form of food production.

I suspect at this point that former rainforest land accounts for most of the grazing heads, but it's difficult to find numbers.

No idea what the GP means by marginal crop land, but yes, people tend to grow cattle on land that isn't very good for crop, for one reason or another (the most common reasons being a rocky terrain or a non-plane surface, poor soil is usually not such a reason as soil is always fixed anyway).

> My understanding is that rainforests take up so many nutrients that the soil is actually very poor and unsuitable for most kinds of agriculture.

That's a characteristic of the Amazon forest specifically (and not even all of it). The soil is poor because it's an old land with a lot of raining, that carries the nutrients away, it's not a fault of the forest. Other rain forests have different characteristics.

Brazil, India and China are big countries by land area. Different parts of each country have different soils and even climates.

> But more than half the cattle in the world live in Brazil and India.

Not true.

https://beef2live.com/story-world-beef-production-ranking-co...

> So one could easily say that recently burned Amazon rainforest is "marginal crop land", and that would make this statement technically true while still being no consolation at all.

The point is that cattle can be raised in marginal crop land. Palm trees cannot. Yes, we should stop cutting down rainforest for cattle and palm oil. The difference is that we can raise cattle in the tons of marginal crop land we have around the world.

> The next biggest chunk of the earth's cattle live in China

Not true.

https://beef2live.com/story-world-beef-production-ranking-co...

> Grazing is supposedly a major factor in the expansion of the Gobi desert.

Supposedly? Care to provide a source for that?

> Perhaps all the biggest CAFOs are located in marginal crop land, but the grain they're feeding to the cattle is all grown on prime crop land.

Care to provide source for that?

If you really are concerned about the rain forests, then you should be against palm oil and raising cattle in the amazon rainforest. But it seems like you are just against raising cattle.

The confounding variable is that the cows would have been produced anyway for food, so using leftover tallow, bone, etc is ecologically virtuous

Unless you pay for it.

The cows are produced for money. Muscle meat is one of the most lucrative products, but demand for any part of the cow incentivizes more cows.

It's possible that it would still be ecologically the lesser evil because the market value is low and what you might choose as an alternative isn't necessarily better, but it's not so clear cut as you make it sound.

And as many people have discovered, once you try to commercialize use of a 'free' resource it stops being free real quick.

Does anyone making biofuel still get their feedstock for free?

Yeah, that was my thought. Having local farms supplying local butchers and using every single bit of the animal.

If we could consume the exact same plant calories, that would be an apt comparison. However, I'm loathe to consume such plant matter like corn cob, stalk, leaf, and other plant matter that is indigestible to humans.

I though cattle were more like 1/10.

10% is the average-ish trophic efficiency in the wild. In industrialized farming we have optimized feed, antibiotic growth promotion, and lack of exercise that brings that down to 1/6 or so for cattle