Can This Toilet Save Millions of Lives?

A solar-powered toilet is the latest hope for the 2.5 billion people without access to clean water

Caltech toilet
Prototypes of the winning design from the 2012 "Reinventing the Toilet Challenge" are now being tested in India. Caltech/Michael Hoffmann

Globally, you might say that there is one household item that separates the haves from the have-nots. Of the more than 7 billion people populating the Earth, 2.5 billion don't have access to a toilet. In these regions, where clean water is scarce, easily preventable diseases, such as typhoid and cholera, are full-blown epidemics. Each year, as many as 1.5 million children die because of poor sanitation.

For these impoverished communities, concentrated mostly in parts of South Asia and Africa, sewage plants simply aren't an option. Families are often forced to use contaminant-ridden alternatives like latrine pits (essentially a dug-out hole in the gound) or simpy resort to defecating out in the open. So for toilets to be practical, they need to be not only self-powered and waterless, but also affordable for families that make as little as a dollar a day. To that end, the Bill and Melinda Gates Foundation launched the "Reinvent the Toilet Challenge," a competition which, in 2012, awarded a team of researchers $100,000 to develop a prototype capable of solving one of the most dire health crises in the developing world.

The winners, a group of engineers working out of the California Institute of Technology, has now embarked on a crucial trial run of their design. In December, a couple of test toilets were shipped to India and installed at public restroom facilities at Mahatma Gandhi University in Kerala and in Ahmedabad. In March, the prototype in Kerala will be moved to Delhi, where it will be demonstrated at a toilet fair.

Interestingly enough, the concept the Caltech team ultimately came up with isn't waterless. In fact, it operates just like a conventional toilet. "We went with a conventional flush toilet because, after testing different designs, we found people generally prefer those," says Clement Cid, a PhD student who worked on the project. "This is true even in the developing societies."

In practice, the toilet system—a self-contained combination of a toilet and a sewage system—works similarly to what's found in the small-scale septic tank sewage systems popular in rural areas of the United States. A simple flush and the feces is sent to a holding chamber where it's put through a hi-tech sanitation process that eradicates infectious, disease-causing bacteria. 

Caltech toilet
The challenge now is to figure out how to bring down the $1,200 price tag of what's essentially a portable, self-contained sewage treatment system. Caltech

The most noticeable difference between this new design and standard toilets is the addition of a roof-mounted photovoltaic panel. The panel powers the whole sanitation process by supplying energy to a biochemical reactor located beneath the floor that's engineered to purify the waste through the use of electrodes. As feces and urine pass through this chamber, an electrochemical reaction between the anode and cathode (think batteries) breaks down the matter into separate components, such as hydrogen, fertilizer and clean water. Another mechanism filters the waste, diverting the hydrogen toward a compartment that stores it as energy in fuel cells. The fertilizer is collected for farming purposes, while the remaining water is pumped back into a reservoir so it can reused.

“It's an entirely closed-loop system,” Cid explains. “And whereas septic toilets treat the waste only partially, the water that we recycle is totally safe, without any contamination.”

The challenge now is to figure out how to sufficiently bring down the $1,200 price tag of what's essentially a portable, self-contained sewage treatment system. The figure doesn't include other expenses, such as maintenance and repairs should the toilet break down. When connected to the grid, operating the toilet runs about 11 cents a day, more than twice the foundation's stated goal of delivering a technology that costs 5 cents a day. Though it still doesn't sound like a lot, imagine spending 10 percent of your income just to use a toilet. Hooking the system up to a rechargeable battery would raise that number even more since the energy storage units would need to be replaced every so often.

The team's goal, for now, is to devise a method for manufacturing electrodes that function at the same efficiency, but at half the price. Much of this, Cid says, would involve cutting deals to attain the source materials locally. The team is also exploring a redesign that would make the toilet system more compact, requiring less materials. Another possibility is figuring out a way to tap into the fuel cells, a potential source of  energy.

"We've built a top of the line BMW and the goal is to provide a very low end Tata Nano car," says Michael Hoffman, an engineering professor who leads the project. "We are currently exploring manufacturing options. Next week, I will be visiting potential manufacturing partners in China."

One approach, which the engineers have discussed with the Bill and Melinda Gates Foundation, lies on the business end. The proposed strategy involves initially marketing the commodes to middle and upper-middle class families in Asian countries, who tend to be receptive to the idea and also able to afford installation. The expectation is that as mass production gradually ramps up, manufacturing costs are driven down.

But the solar-powered toilet isn't without its critics. In an editorial published by the New York Times, Jason Kass, an environmental engineer and founder of an organization called Toilets For People, points out some of the flaws inherent to efforts that seek to apply highly-sophisticated technologies to the problems of people with scarce resources.

He writes:

Just imagine the fate of a high-tech toilet in one of these communities. What happens if the unique membrane systems get clogged? Or if the supercritical water vessel or the hydrothermal carbonization tank leaks, or worse, explodes? Or what if one of the impoverished residents realizes the device is worth more than a year's earnings and decides to steal it? If the many failed development projects of the past 60 years have taught us anything, it's that complicated, imported solutions do not work.

Treehugger's managing editor Llyod Alter slams the latest version of the toilet as an entirely misguided effort that, above all, disseminates some of the West's most mistaken ideas on sanitation. These include sitting on a toilet rather than squatting, a choice that can cause more strain in the bowels, and placing toilets inside of washrooms. He contrasts this with toilets in Japan, which are more sanitary since they're located in a separate room. And as Kass mentions, servicing such a complicated system would require trained specialists that these poor communities cannot afford.

Nonetheless, Hoffman believes that with the way new technologies tend to progress, these kinds of toilets will be practical in the long run. He uses Apple as an example. When Apple first introduced the touchscreen smartphone just seven years ago, it cost at least $600. Early this week, software developers from Mozilla unveiled a version for developing markets that debuts at just $25. "The costs were once prohibitive for the poor, but now are attainable," he adds.

The practicality of solar-powered toilets in impoverished communities that severely lack resources should become more clear within the next few years. In 2015, the Caltech team plans to test newer prototypes in small communities in five countries, most likely India, China, Thailand, Cambodia and Peru. Mass scale production of at least 1,000 toilets is slated for as early as 2016.

Get the latest stories in your inbox every weekday.