Bill Gates, Microsoft co-founder and billionaire philanthropist, wants to talk poop. Literally. The Bill and Melinda Gates Foundation, which is hosting a "Reinvent the Toilet Fair" on August 14 and 15, is on a mission to build a better crapper. Why? Poop is a worldwide problem.

Here are the dirty details: Four out of every 10 people around the globe have no where to "go." That adds up, says the foundation, to 2.5 billion people doing their business any place but in a toilet.

According to the foundation's website, poor sanitation leads to food and water tainted with fecal matter, which causes 2.5 billion cases of diarrhea in children under five and 1.5 million child deaths a year. The United Nation estimates that half of the world's hospitalizations result from bad sanitation.

The good news is that better sanitation could prevent most of those child deaths, provide safe drinking water and improve lives.

Foundation co-chair Bill Gates, who announced cash prizes at the fair today for the best designs, said in a statement, "Innovative solutions change people's lives for the better. If we apply creative thinking to everyday challenges, such as dealing with human waste, we can fix some of the world's toughest problems."

The foundation has committed $370 million to the Water, Sanitation & Hygiene (WSH) initiative, which includes devising a 21st-century toilet.

What the Gates Foundation calls the toilet revolution could turn crap into stuff like fuel, fertilizer and fresh water. In October 2011, the challenge gave grants to researchers to come up with a better spin on the 18th-century porcelain toilet design. A year later, the fair is showing how far the teams have come.

Some of the ingenious ideas at the toilet fair include a Swiss system for diverting some urine and recovering water for flushing, and a design from Stanford researchers that turns human waste into charcoal. And a team from the Delft University of Technology in the the Netherlands invented a toilet that turns human waste into fuel through microwave technology.

Of course, we want to know, did any of these ideas come while sitting on the pot? Sorry, we couldn't resist a little bathroom humor.