> Where do you think the nutrients for cultivated meat are going to come from? Where do you think the byproducts are going to go?

Most likely the same places they already do.

Ideally, GM the cell lines and make them photovores or electrovores, have them synthesise their own nutrients from air and rock — but that's a way off.

> Sustainably raised meat is the most environmentally friendly way to feed people.

Not even today.

Right now, a lot of livestock is a middle-man between plants and us, and we could feed more people for less money just by eating a fraction of the crops that are used to feed the animals.

Meat is a preference, widely chosen as people get richer, it's not a "best option" in terms of health or economics.

I'm pretty certain the current processes require a growth medium that comes, partially, from other animals. That's not a hard requirement, however, and the answer "farmed algae" is a reasonable target as the process is refined.

For that you need sustainably grown plants, which are even more environnemental friendly if directly fed to human. They are possible at scale of present humanity, witch grass fed meat is not.

The most environmentally friendly is to not eat meat.