The original note, as written at the time
This involves the use of nano particle enabled compost and dust to ease cleaning, especially of toilets, without the use of water.
Ongoing development
Nanoparticle-enabled compost and dust, to make cleaning easier — especially of toilets — without using water.
The waterless part is the serious engineering. A toilet is the largest water use in a household after bathing, and in a city where supply is intermittent the toilet is where the shortage is felt first. Everything about the way we clean assumes a flow of water, and the assumption is the constraint.
A dry medium that lifts and carries rather than dissolves changes the mechanics. Water works by dissolving and flushing; a fine particle works by adhering to the soil and being removed with it, which means the cleaning action happens at the surface rather than in the drain.
The compost part of the note is the more interesting material. A composted, structured particle has a large surface area and a slightly acidic chemistry, both of which do useful work on the films that form in a wet room. It is also, by definition, something a household could make rather than buy.
The honest question is pathogen control. A dry cleaning method that spreads material around a toilet is a method that risks moving contamination rather than removing it, so any product here has to be tested against that specifically, not just against visible cleanliness.
The prize is a toilet that can be cleaned in a drought, in a school with no running water, in a settlement with a shared latrine.
Water is not the only solvent. It is just the one we stopped questioning.