Just consider some of the parameters of the Gates Foundation’s first Reinvent the Toilet Challenge: Create a “practical” toilet that is suitable for a single-family residence in the developing world. Make sure it takes in the bodily waste of an entire family and outputs drinkable water and condiments, like salt. And while you’re at it, make sure that the toilet is microprocessor-supervised and converts feces into energy. And all this has to cost just pennies per person per day. That’s some toilet.
The winner of last year’s contest invented a solar-powered toilet that converts poop into energy for cooking. Impressive — but each one costs $1,000.