> Our current habit of disposing of crap sight unseen in ways that flush all those essential nutrients into the oceans

Is that the standard way of handling sewage?

I have only toured one sewage-processing plant, and I am sure that there are many different types, but that one had huge (as I recall, building-sized) machines pulling all of the solids out of the sewage; this sludge was then loaded on trucks. I do not remember, now, if it was carted to landfills or composted, but of course it could be composted.

Before using it for agriculture one would want to consider whether the medications and other contaminants are a problem.

One cool thing about that plant I remember is that the water it produced was well within drinking-water standards: it could be connected straight to the water system.