... When I first wrote about it I was rather negative about the idea, writing Gates Foundation Throwing $42 Million Into The Toilet. I have rarely received so many nasty comments, calling me every name in the book for criticizing the Gates Foundation, they are geniuses and I am just a...blogger! What did I know? Fortunately for me all those comments were flushed away when we changed commenting systems, so everyone will have to start from scratch. Now that a winner has been declared, I think it confirms everything I was worried about.
The winning design, from Caltech, "uses the sun to power an electrochemical reactor. The reactor breaks down water and human waste into fertilizer and hydrogen, which can be stored in hydrogen fuel cells as energy. The treated water can then be reused to flush the toilet or for irrigation."
I have watched the video twice and there is a lot of serious technology here, none of which is cheap. It uses water flushing fixtures, which flushes the poop and pee into a septic holding tank below. Solids sink to the bottom, and the liquid on top goes to the electrochemical reactor, where the waste is oxidized and the water is electrolyzed to hydrogen. Table salt is oxidized to make chlorine, which is used to disinfect the water, which then goes to a tank and can be used for flushing the toilet. The sediment can be removed and used for fertilizer. The power for all this comes from a tracking solar panel.
Where do you start? First of all, by using a flush system that mixes water with the poop and urine. I have written about how the flush toilet evolved, it was an accident of history. Almost all of this toilet's technology is about cleaning and reusing that water; the poop is treated through anaerobic processes not much different than a traditional septic tank. By adding water you lose the valuable urine and you create a need to dry the poop. This toilet isn't dealing with waste, it is dealing with the medium that is moving the waste, the flushing water.
Also, it is hugely complicated. The idea that this could be maintained and operated in some of the poorest countries in the world is a serious stretch. Oh, and it generates deadly chlorine gas. It would need an engineer to run.