they would use their sewage to fertilize the gardens.
as im sure youre aware: absolutely terrible idea, anyone says this to you: run.
You have to maintain human waste at a 10:1 poop:notpoop mixture, and then a 3:1 poop-mixture:greenery ratio at 135°F and 6.5pH for at least 30 days with regular turning and mixing before you can use it.