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.
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.
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...
I suspect at this point that former rainforest land accounts for most of the grazing heads, but it's difficult to find numbers.
> 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.
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 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.
Does anyone making biofuel still get their feedstock for free?