““Why don’t we just get our protein from fruits, vegetables, legumes, and grains instead?””
1. fruits, veggies, legumes, and grains require the consumption of 10-20 times as many carbs compared to eating meat products to obtain the daily required protein ...
2. it’s nearly impossible to obtain the necessary iron from fruits, veggies, legumes, and grains compared to meat products because fruits, veggies, legumes, and grains are very low in iron compared to meat products, AND the iron they do contain is very difficult to assimilate compared to the heme form of iron in meat products ...
3. fruits, veggies, legumes, and grains contain zero vitamin B12 ... period ...
Precision fermentation can produce chemically identical molecules to what you are asking about. They DNA is transferred to yeast, fungi or bacteria and they will happily crank out whatever molecules you programmed them too.
Here are some prime examples.
Identical fatty acids to cow butter down to the molecular level.
https://newatlas.com/technology/savor-butter-bill-gates/
Complete chicken tissue and in Israel they are banned for using immortal cell lines so no this is not cancer cells they use growth hormone also from precision fermentation sources.
https://newatlas.com/science/lab-grown-chicken-approval-restaurant/
Grouper cells and meat again DNA cannot tell the difference from the two they both would test and show that species of grouper.
https://newatlas.com/science/steakholder-foods-cultivated-fish-fillets-grouper/
Egg whites down the the molecules chicken product.
https://newatlas.com/science/world-first-chicken-free-egg-white-every-company-macarons/
More egg whites
https://newatlas.com/environment/fungus-ovalbumin-alternative-egg-whites/
Steak from Angus or Kobe beef DNA
https://newatlas.com/science/world-first-lab-grown-rib-eye-steak-3d-bioprinting-aleph-farms/
Another Israeli chicken meat group. Israel is a tiny country with limited water and more limited arable land they are the world leaders in biotech, desalination and drip irrigation with recycled water 95% of every drop of water in Israel is recycled only Las Vegas comes close.
https://newatlas.com/science/future-meats-lab-gown-chicken-breast-costs/
Then you have raw ingredients fermentation for the production of sugars ,starches and proteins which monogastrics call food without any plants ,using only air,water and electrons.
https://newatlas.com/science/artificial-synthesis-starch-from-co2/
https://newatlas.com/science/microbe-protein-food-security/
https://newatlas.com/protein-food-from-electricity/50557/
Of course you can also add protein directly to the grain carbohydrate source as a complete ration, given that artificial photosynthesis can be used to grow the rice on acetate or glucose from air water and electrons. They are correct this is space food too as humans are never taking livestock to space the mass balance is such that is nearly impossible.
https://newatlas.com/science/beef-cells-rice-hybrid-new-protein-rich-food/
There will be 9 billion humans soon enough and there is no mathematical way to let them all have a western meat based diet our planet simply doesn’t have the land, water and fertilizer resources for that, synthetic biology and biotech is the only way or 7 billion need to be removed. This planet can support two billion at EU levels of energy and KCals it’s just cold hard math and it well universal.