I was astonished by the fertility of the ground.  Then I realised that there had never been a septic tank and the waste had been dug straight into the ground.

Composting is safer if you allow a couple of years for pathogens to die off, before adding it the vegetable patch.  Sawdust and faeces don't smell at all bad if you separate the urine and keep them in a sealed box.

I'm not sure how this would work in a city, but it's tragic how much energy and water go into water-based sanitation.