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The Gates Foundation has committed $370m (£235m) to its future toilet initiative and hopes to field test the prototypes within three years.
At the Reinvent the Toilet fair, hosted at its Seattle campus this week, designs included a lavatory that used microwave energy to turn poo into electricity.
Another turned excrement into charcoal, while a third used urine for flushing.
In total 28 designs were shown off at the fair and the winner was a team from the California Institute of Technology.
Led by Prof Michael Hoffman, the toilet they designed was solar-powered and generated hydrogen gas and electricity. They won a $100,000 prize.
The project challenged inventors to come up with a toilet that operated without running water, electricity or a septic system. It needed to operate at a cost of no more than five cents (3p) a day and would ideally capture energy or other resources.
The project challenged inventors to come up with a toilet that operated without running water, electricity or a septic system. It needed to operate at a cost of no more than five cents (3p) a day and would ideally capture energy or other resources.