[strait]

Composting a humanure mix in sealed enclosures with a regulated exhaust would produce relatively high nitrogen compost. Deliver this locally to growing crops in a just-in-time manner for less nitrogen loss. However, it's hard to see this happening on any meaningful scale, with regard to the current trajectory of modern civilization, especially in the cities.

[rapjr9]

See Milorganite:

https://en.wikipedia.org/wiki/Milorganite

At scale, in Milwaukee. There have been concerns about contaminants though. Still production and sales have been ongoing since 1926.