Sanitation: it’s not the sexiest issue, but it’s a big problem in much of the world. A staggering 2.5 billion people don’t have access to proper sanitation, and open defecation leads to the deaths of 1.5 million children under age five every year. The Bill and Melinda Gates Foundation is a major funder of sanitation-related initiatives. Last week, the Gates Foundation showed off its 2011 grantees that are working to reinvent the toilet, in what can safely be called the world’s most interesting toilet fair (the foundation hauled in 50 gallons of fake poop made out of rice and soybeans for demonstrations at the event).

As part of its Reinvent the Toilet Challenge, the Gates Foundation doled out $400,000 grants to eight universities to create safe, affordable, and hygienic waterless toilets. The toilet fair held in Seattle this past week showcased those toilets and offered three new Reinvent the Toilet Challenge awards for the most promising innovations–and they are, as far as toilets go, incredible.

First prize ($100,000) went to Caltech’s solar-powered bathroom, which consists of a toilet and a solar panel that powers an electrochemical reactor. A reactor in the bathroom turns water and human waste into hydrogen and fertilizer. The hydrogen can be stored in fuel cells for energy, and the water can either be reused in the toilet or for irrigation. All of the toilet’s inner workings can be buried underground.

The $60,000 second place prize went to the Loughborough University’s “toilet that produces biological charcoal, minerals, and clean water.” The toilet uses a process called continuous thermal hydrocarbonization–decomposition in water without oxygen at high temperatures–to turn feces into biochar. The system, designed to be completely off the grid, is powered by heat created from the biochar’s combustion.

The $40,000 third place prize went to the University of Toronto’s project: “A toilet that sanitizes feces and urine to recover resources and energy.” The toilet features a hand crank that processes waste through a sand filter and an ultraviolet light disinfecting chamber. A smolder chamber incinerates the waste so it doesn’t pose harm to the surrounding community.

Other exhibitors at the toilet fair–challenge entrants as well as foundation grantees and partners outside of the Reinvent the Toilet Challenge–included Hattery Labs’ Poop Games (mobile games that promote sanitation), a toilet that uses microbes to turn poop into power, a small-scale device to sterilize fecal sludge, a wind-powered sanitation system, and a solar steam sterilizer for human waste.

Check out the fair in the slide show above.