The Bill and Melinda Gates Foundation recently held a competition that asked some of today's brightest inventors to help solve a problem plaguing more than 2.6 billion people worldwide. The task was to reinvent the toilet without using running water, electricity or a septic tank and it must not expel any pollutants, preferably capture energy and operate at a cost of only 5 cents per day.

The "Reinventing the Toilet" fair was held at the foundation's Seattle headquarters where scientists and experts from around the world displayed their inventions. The whole idea to reinvent the toilet started just over a year ago and there's already $370 million in grants and foundation dollars that have been put aside for the project.

Several of the designs on hand were extremely high-tech with one using microwaves to transform human waste into electricity. Another unit is able to turn waste into charcoal while a third device captures urine and is able to use it for flushing. Many of the projects are able to recycle waste into other usable resources such as water for irrigation, animal feed or to power other systems.

But not every device looks like a machine from the future. The London School of Hygiene and Tropical Medicine showcased a system that uses soldier fly larvae to process waste. This method produces animal friendly feed and only cost one penny a day to operate.

Prototypes from the fair are expected to enter field testing within the next three years. "If we do it right, there's every possibility that some of these designs would also be solutions for rich and middle-income countries," Gates noted.