A Swiss and Austrian team has won $40,000 from the Bill and Melinda Gates Foundation for coming up with a better toilet.
The brief was to produce a toilet that wouldn't need a sewer or outside energy source, could be part of a recycling and treatment system for wastes and cost no more than five cents per day per person.
"It was obvious that separation technology should also be part of the competition model," says Tove Larsen of Eawag. "Only thus can the valuable raw materials and the water in urine and feces be recovered efficiently."
The team's design is a squat toilet that uses very little water - just a liter to a liter and a half per use.
"This is absolutely decisive for cleaning the toilet, hand washing and the anal hygiene with water practiced by Muslims and Hindus," says Larsen.
It's not connected to a water supply, though: a user operates a foot pedal to make water flow into a small reservoir, with already-used water pumped upwards behind the toilet.
Cleansed by means of a membrane filter, the used water is free of germs, says the team, thanks to electrolysis by a solar powered electrode.
Importantly, the winning submission also includes a transport system, with self-sealing containers. The end product can be processed in treatment plants into saleable products like fertilizer and biogas, making the whole system a sustainable business proposition.
"Whether our system can really become established depends on the quality of our business model," says Larsen. "No system that depends permanently on subsidies can function over the long term."