• 02.20.14

Take A Seat On This Gates-Funded Future Toilet That Will Change How We Think About Poop

The inside story of how Caltech engineers and Kohler designers are testing a toilet technology that could significantly improve the health of 2.5 billion people around the world. It might even appear in U.S. bathrooms, too.

Yan Qu and Clement Cid spend a lot more time thinking about poop than your average academics. The pair, both at Caltech, are part of a team working on what could be the future of bathrooms: a self-cleaning, solar-powered toilet that turns human waste into hydrogen and fertilizer.


In 2012, their toilet won the Gates Foundation’s Reinvent the Toilet Challenge, which asked entrants to create a safe, cheap, and hygienic toilet–one that could serve the 2.5 billion people around the world who lack access to safe sanitation. Now the toilet system is getting some help from the toilet maker Kohler and taking a trip to India for testing.

The Caltech toilet has been a long time in the making. In his previous job as co-founder Sonoma Research, team leader and Caltech engineer Michael Hoffman worked on a number of toilet-related projects, from U.S. Navy wastewater treatment plants to a NASA space shuttle system for urine removal. The Gates-approved toilet is, in a sense, a continuation of this work.

In 2011, Hoffman and his team received a $400,000 grant to develop a toilet that can remove human waste for five cents per user per day. This is what they came up with: A toilet that uses a solar panel to power an electrochemical reactor, which breaks down waste into solids that can be used as fertilizer and hydrogen that can be stored in fuel cells to power the reactor when it’s cloudy outside. A pump sends treated, recycled water back to a reservoir on the top of the toilet. The toilet is completely self-contained, no sewer connection required. It can run off the grid, and it can treat wastewater in just three to four hours.

The team has yet to reach its five-cent goal, however. According to Qu, a Caltech postdoctoral researcher, the toilet currently costs about 11 cents per user per day if it’s connected to the grid (or $1,500 over the 20-year life span of the toilet). With batteries, the system costs more. “We’re working on lowering the cost, obviously,” says Qu. “We’re also working on using the hydrogen and all of that. That’s an added value to the system that we don’t take into account.”

In December, Caltech sent two solar toilet systems to India–a full bathroom and treatment system in a shipping container to Mahatma Gandhi University in Kerala for testing, and a treatment system to Ahmedabad, where it will be hooked up to Eram Scientific’s “eToilet“–an electronic self-cleaning public toilet system that charges people a small fee to enter. The Mahatma Gandhi toilet is also making a pit stop in March at a toilet fair in Delhi.

Building a better toilet

Building a relatively low-cost, efficient, and maintenance-free toilet has been a huge challenge for the Caltech team. Even after years of work, Caltech is still figuring out how to make the system completely automated. “Right now, we require to have someone open and close the [toilet] valves, even if it’s done electronically. The goal of the system is one that works by itself but can be remotely monitored,” says Cid, a graduate student with the Caltech team.

How do you test a new toilet? With fake poop, of course.

While the toilet is designed for easy repairs, the system will inevitably break down at some point. When that happens, someone needs to be close by to fix it, or the toilet will end up trashed like so many promising high-tech innovations sent to developing countries. Caltech is considering a business model that involves training local technicians. This should theoretically work, explains Qu, because “when it doesn’t work, it’s easy to see. You can do a test on different parts of the systems.” Aside from automation and repair logistics, Caltech is also working on finding local manufacturing resources wherever the toilet is used to make production as cheap as possible.


Participants at the Reinvent the Toilet fair used synthetic poop in their toilet demonstrations (we wrote about the company behind the fake poop here), but Caltech uses the real thing for its tests. “People use the bathroom. We don’t use synthetic. We use real shit,” Cid says. “We do the bacterial tests before we do the [chemical] reaction. Over time, we see the degradation.”

Kohler steps in

Caltech isn’t working on the project alone. When the winners of the toilet challenge were announced, an engineer from Kohler–a company best known for its plumbing products–reached out to the team and began working with them on plumbing. “He started to work with them to specify the right products for project, knowing they’re trying to build sealed toilet solution prototype to be shipped to India on the 17th of December,” explains Tristan Butterfield, Kohler’s global creative director.

Then, before the toilets were shipped in December, Butterfield drove with his team to Caltech to take a look at the self-contained toilet system. “No one had really thought about the design of the bathroom. They’ve thought about the product, but not the interior design or the exterior design,” he says. “The fact is that this thing is going to be put into a community in India and someone is going to have to live with that.” If the toilet was going to be placed in a community, he thought, it should have some cultural context. It shouldn’t feel institutional.

Ever since, Kohler has been working on the design for the system, which may end up in a local community where it could be used by up to 10 families after it visits Mahatma Gandhi University.

The LED-lit interior of the bathroom was inspired by old-fashioned Indian bathrooms, according to Butterfield. It’s highly decorative, with blue geometric tiles provided by Heath Ceramics. The exterior, painted a soft pink color, is being decorated by Indian artists on the ground. A charging station provides power for phones (“More people in India have cell phones than toilets,” Butterfield notes) and benches on the outside of the bathroom offer a place for people to sit while they wait their turn.

Butterfield admits that the design is the “Rolls Royce of the category,” and that the team will work on driving down costs later. But Kohler’s plumbing additions aren’t particularly expensive, and since the company has distribution in India, it’s easy to get toilet parts locally.

“All the teams working on this don’t know if it’s going to be a success. They don’t know if it’s going to work or be received well. That’s the exciting part of doing something unprecedented,” says Lily Zepeda, a filmmaker who has been visiting the Caltech campus twice a month for a documentary about the toilet project.


The toilet of the future

Once testing is finished–there will be a number of new test units built in the near future–the next step is to actually start manufacturing the toilet. “There is a potential market in the U.S, so we’re thinking about that. We have discussions with different groups in different countries. The Gates Foundation is helping us move this way,” says Qu.

In some ways, the toilet is a tough sell. Why create such a high-tech, expensive system, you could argue, when many places just need basic toilets? The Caltech toilet is even a cut above the toilets we use in the developed world–if every household had one, we wouldn’t need to worry as much about flushing the toilet during droughts, for example. But if Caltech can get the cost down to a price point where the toilet is truly affordable, there’s may be no reason why developing countries shouldn’t have the opportunity to leapfrog us in toilet technology, much like they already have with cell phones, skipping the landline infrastructure entirely.

The Gates Foundation shows no signs of letting up on its funding for futuristic toilets anytime soon, so even if the Caltech team doesn’t succeed the way it hopes, plenty of other researchers will continue working in the area.

“Look at the promise of delivering proper sanitation to parts of the world that will, let’s face it, never have water or sewage infrastructure,” says Rob Zimmerman, senior channel manager for sustainability at Kohler. “If that can be demonstrated, it’s going to be one of the most significant breakthroughs of the 21st century.”

About the author

Ariel Schwartz is a Senior Editor at Co.Exist. She has contributed to SF Weekly, Popular Science, Inhabitat, Greenbiz, NBC Bay Area, GOOD Magazine and more.