So if you are a smart investor, you know where the next big money will come from.
US billionaire and philanthropist Bill Gates is investing in a solar-powered toilet for the developing world that will use little or no water.
The need for a new type of toilet is an important part of the Bill & Melinda Gates Foundation's push to improve health in the developing world, officials familiar with the project said.
Last year the foundation, named after the Microsoft co-founder and his wife, gave grants to eight universities around the world to help create a hygienic toilet that is safe and affordable and can transform waste into energy.
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 a day and would ideally capture energy or other resources.
Open defecation leads to sanitation problems that cause 1.5 million children under five to die each year.
The eight universities, led by Professor Michael Hoffman, designed a toilet that generated hydrogen gas and electricity. They won a $100,000 prize.
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