We have been saying it for years; we are reaching a phosphorus crisis and should be separating poo from pee and recovering the nutrients from both.
We keep pointing to the Swedish example where they used NoMix urine separating toilets, where as Mike noted a few years ago, "NoMix-technology is well accepted; around 80% of users liked the idea, 75−85% were satisfied with design, hygiene, smell, and seating comfort of NoMix-toilets."
Except it wasn't actually true. According to Tove Larsen, a chemical engineer who has been studying the implementation of NoMix toilets in apartments, a school and a library, what seemed like a good idea at the time didn't pan out in practice. She tells the BBC:
“Although 80-85% of the people thought that it was really a good idea, the more they had to live with the toilets themselves, the more critical they were towards this technology, which is not really mature,” says Larsen.
In Larsen's study, a number of problems become apparent; men have to sit down for it to work, or there have to be separate urinals. The urine can cause scale buildup in the pipes and need to be cleaned regularly. In public washrooms they were rarely used properly:
Women, for their part, are reluctant to sit on public toilets for hygiene-related reasons. Some users find it difficult to adopt the required sitting position. Children in particular have problems targeting the right compartment, which increases the need for cleaning.
Because of all the problems, the company producing the toilets has stopped making them, deeming the technology to be too much of a commercial risk. On top of last year's failure of the world's biggest urine-separating and composting toilet scheme in China, the alternative toilet scene is not looking so positive these days.
Is it a design problem or a people problem? Leslie Evans Ogden writes in the BBC :
Perhaps part of the reason is that any change that makes us urinate or defecate in a new way make the process a little less invisible, desanitising it enough to make us uncomfortable. Today’s loo offers an out-of-sight-out-of-mind experience.
Perhaps. The NoMix didn't seem to be that radical an innovation, which is why I thought it would be adopted without much fuss. It's not like everyone was sitting on a composting toilet. As far as the process being invisible, Germans are perfectly happy to poop onto shelf toilets so that the goods can be inspected, originally for worms and now, for I don't know what. But they do it and visitors adapt.
Design failure or human failure? I don't know, but the problems we face in terms of water use and peak phosphorus are huge, and people are going to have to get used to change.
See also Core77: A great product idea undone by human factors