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Comment by vfc1 | Hacker News Reader

Soy crops are a good example, the majority of them are to feed livestock but they are a great crop to feed humans instead, and without all the waste involved in having to feed a cow first and then eat parts of it.

You can make plant milk with soy too, its a very versatile crop. With it, you can feed the same amount of people with a fraction of the land, water, and pollution.

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Barley crops are a good counter-example. There are three main purposes: malting, milling & animal feed. A good chunk of the feed barley on the market is barley grown for malting or milling but wasn't good enough for those purposes and is fed to chickens. The alternative to feeding it to chickens is to throw it away. That's hardly environmentally friendly.

Some barley is purposefully grown for feed rather than aiming for the higher price that malting or milling will get. Yields on such variants can be as much as 3 times that of a nice malting or milling variant.

Given that a chicken can convert 1.5 grams of barley protein into 1 gram of meat protein, you can see how it be more environmentally efficient to "eat" barley by running it through a chicken first.

Well then lets no plant Barley to feed humans, let's use something else. The thing is a good portion of the surface of the Earth is covered with agricultural fields, most of them aimed at feeding cattle, not humans.

It's a bit insane if we think about it. I doubt that conversion from barley to chicken is so efficient. There is more nutrition in barley than the protein, there are carbs as well and fiber and micro nutrients that would be good for humans, besides only the protein.

A better comparison would be in calories, considering the waste of slaughtering the chicken and all the parts with don't eat, plus all the waste produced by the chicken and the water used.

Not plant Barley? Hate to tell you, but when they said 'malting' that means 'malted barley' as in the primary ingredient in beer. We are not going to stop planting that any time soon.

Feed barley also yields almost 2X that milling wheat does on dryland Canadian prairie, so switching species rather than variants doesn't change the argument.

And if you want to use calories instead of grams of protein, be my guest. It'll just help my argument. Chickens eat unhulled barley; the hull is almost half the weight of the kernel. Humans eat hulled barley and still a good chunk of its calories are indigestible fiber. That may help your digestive system but you're not extracting any energy from it.

You didn't address, and I don't know: what is the relative environmental impact of growing human-grade soy vs. livestock-grade soy? Is there even necessarily a distinction?

As far as I know it's all just beans, they are all eatable by humans. The difference between resource consumption of different types of soy crops, if any, is not comparable to the difference between eating the soy directly or feeding it first to an animal, the second is a much more wasteful and environmentally impactful as you can imagine.

AFAIK there is no human-grade soy vs. livestock-grade soy. But the soy grown for livestock can usually be fed in the ratio of <soy for one animal>:<soy for many humans> (this ratio varies based on which animal and farming practice you consider).

You won't need to grow livestock-grade soy if you don't have livestock to feed. But we will always have humans to feed (because we're humans).

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