That's one thread I had skipped, there's only so much time in the day. Well, composting works, except when it fails - failure of composted fecal matter, a badly designed compost pile, will attract rodents, leading to the spread of disease, leading to the kinds of issues that are addressed and mitigated by a working sanitation system. The idea that all 3 million urban dwellers could compost as an alternative to a sanitation system is a big stretch, I would say impossible - that they might all do it without creating a disease risk is downright wrong. And as for the compost material of choice, sawdust - plentiful in the Pacific Northwest, we have lots of it; in deforested Haiti and urban Port au Prince, not so much.