They are part of a Bill & Melinda Gates Foundation competition to reinvent the toilet for the 2.5 billion people around the world who don't have access to modern sanitation.

Scientists from around the world have taken up the challenge, and the foundation announced some projects Tuesday that will be getting more money to take their ideas from the lab to cities.

There, local entrepreneurs will use the new technology to turn pollution into cash.

"We couldn't be happier with the response that we've gotten," Bill Gates said.

To pass the foundation's threshold for the world's next toilet, it must operate without running water, electricity or a septic system, not discharge pollutants, preferably capture energy or other resources, and operate at a cost of 5 cents a day.

The United Nations estimates disease caused by unsafe sanitation results in about half the hospitalizations in the developing world. About 1.5 million children die each year from diarrheal disease.

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