By Ariel Schwartz

Today is World Toilet Day. That's not as silly as it sounds. Two and a half billion people around the world don't have access to clean toilets, which means they are at risk for a number of diseases--diarrhoeal diseases, in fact, kill someone every 20 seconds. More people die from poor sanitation than measles, malaria, and HIV/AIDS combined.

There is some hope. The Bill and Melinda Gates Foundation has been steadily offering grants to sanitation initiatives, including some focused on creating better toilets for the developing world. Caltech won the Gates Foundation's Reinvent the Toilet Challenge (a call to create cheap, safe, and hygienic waterless toilets) with a solar-powered, self-cleaning toilet that converts urine and waste into hydrogen and fertilizer.

The seeds of Caltech's toilet were planted 17 years ago when Caltech engineer (and toilet team leader) Michael Hoffmann patented a design for "multilayered nanostructures doing electrochemical degradation," according to team member Asghar Aryanfar. "He was looking for any kind of application until Bill Gates announced the competition," says Aryanfar.

The toilet features a solar panel that powers an electrochemical reactor, which in turn breaks down waste into sanitized solids (a useful fertilizer) and hydrogen that can be stored in fuel cells to power the reactor on cloudy days. A pump sends treated water to a reservoir on the top of the toilet, where it can be used for irrigation or other purposes.

Aside from the electrodes, which have an estimated lifetime of a decade, all the mechanical parts in the toilet are easily reparable--a key feature in remote areas. "Making the comprehensive prototype is a little challenging. We're looking at different shipping containers so we can ship easily," says Aryanfar. "The good thing is we know the technology works. What remains is the prototyping."

Caltech's solar toilet team now has $1.6 million in funding from the Gates Foundation; they expect to have a prototype ready to ship to Africa--with a price tag of approximately $2,200--by December 2013.

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