Restroom Renaissance

Solar-powered toilet wins big for innovative design
Restroom Renaissance
Caltech's solar-powered toilet and wastewater system prototype on display at the Reinvent the Toilet Fair hosted by the Gates Foundation.

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Michael Hoffman, engineer and professor of environmental science at Caltech, and his colleagues were awarded $100,000 for their solar-powered toilet at the Reinvent the Toilet Fair, sponsored by the Bill & Melinda Gates Foundation.

“The foundation is convinced, along with other organizations, that many parts of the world need to be exposed to more sanitary practices using toilets,” says Hoffman.

Hoffman and his team were one of eight recipients of a $400,000 grant to develop a toilet that could turn waste into clean water, energy or nutrients. “Our system was designed to meet the goals of the Gates Foundation,” says Hoffman, “And to be independent of any traditional urban infrastructure, sewers, electrical grids -- to basically generate its own power and then to totally process the waste.”

The Caltech team demonstrated the system at the fair with a toilet, waterless urinal and squat toilet. The self-contained toilet and wastewater treatment system uses energy from solar panels to drive electrochemical treatment processes, which treats the waste. The wastewater is completely disinfected after treatment and residual solids can be used as fertilizer.

“We capture sunlight with solar panels and store the electricity in batteries,” says Hoffman. “In the next generation, the solar panels will be built into the structure that houses the toilet.”

Hoffman adds that Caltech’s toilet design has drawn attention for potential use with portable restrooms in more urban regions.

“A lot of places that have contacted me say it would be great even for the urban environment, like in major cities, which may be not be fully coupled into the subsurface infrastructure for waste disposal,” he says. “I’ve had calls from major cities expressing interest in these self-standing treatment systems where you don’t have to pump and dispose or empty a pit latrine.”

Check out a video on the solar-powered toilet


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