We can eat soy - I had a tasty tofu bowl for lunch. The land used for growing soy animal feed can be also used to grow other plants we can eat directly or after preparation. That requires less land and less resources per calorie which lets us reforest and prevent further rainforest destruction. The carbon opportunity cost of meat is huge, https://ourworldindata.org/carbon-opportunity-costs-food
They are not saying that humans cannot eat soybeans. They are saying that some soybeans are not of high enough quality to be suitable for humans to eat.
90% of the soy that is grown is not fit for human consumption? I'm having a hard time buying that. If they stopped feeding soy to cattle, I find it very unlikely that they would continue producing the same amount in order to get soy that is fit for human consumption. As though what we've been feeding cattle is simply the portion that was already going to be wasted.
I am not the person who wrote that comment above, but they did not say "90% of soy" -- they said "90% of that soy", referring to soy grown in areas of tropical deforestation.
I have no clue if the assertion is correct.
Edit: FWIW, it appears that US soy is mostly used for livestock:
> Just over 70 percent of the soybeans grown in the United States are used for animal feed
I didn’t say soy, I said “plants”. This includes everything we can’t eat - grass, and perhaps low quality soy.
There’s an immense amount of green things growing we can’t digest that cows, sheep, goats, and chickens will happily chomp on or peck at. The idea is that we then eat the cows, etc. It’s simple really.
As an aside, I’ve been on a fat-loss diet all lockdown long, and if it wasn’t for animal products, it simply wouldn’t have worked as well as it did. I need high protein within a limited calorie budget. Hello, chicken breasts and whey powder.
Anyway, if cows are not a good enough system to feed 7 billion people, we should grow fake cow parts in vats, also neatly eliminating the need to kill the animals. I’d be the first to sign up for a fake steak, if it was chemically identical to a grass-fed one (the taste of which is fantastic, absolutely beyond description)