Michael Hoffman, sitting in the middle of the bottom tier, led the California Institute of Technology design team seated in front of its energy-producing, water-saving toilet. Image: Caltech/Michael Hoffmann
Since word got out that Michael Hoffmann and a team of his students had developed a state-of-the-art, sustainable, energy-producing toilet for rural, developing countries, his phone has begun to ring much more frequently.
Hoffmann, a California Institute of Technology professor, was the team leader for Caltech's winning entry into the Bill and Melinda Gates contest to invent a more sustainable toilet. He and his team of six developed a flushing toilet that sanitizes the water and produces hydrogen from human waste to create electricity. One upshot was a $100,000 prize.
Another result was the callers, who are not always the kind one would expect. Some are American cabin owners who live off the electric grid. Others are owners of luxury apartment buildings in India. Others are developers in China, home to a middle class that is expanding much faster than the nation's sewer systems.
"There's a broad-scale interest," Hoffmann said. "There are much bigger markets out there."
While World Toilet Organization founder Jack Sim called improving access to sanitation in the developing world the "cheapest preventative medicine in the world" at the World Economic Forum on Africa in May, the cause has not been advancing as quickly as some think it should.
The seventh of the United Nations' eight Millennium Development Goals is to cut the number of people living without access to clean water in half between 1990 and 2015. So far, 2 billion people have better access to clean water, but the world is still off track to the goal, according to the latest World Health Organization report on sanitation. It is unlikely to reach it in the next three years.
While China and India have made great strides in providing access to sanitation by decreasing the rate of open defecation, sub-Saharan Africa and most of South Asia lag behind.
One answer to an urgent question
Many of these regions also face diminishing water resources in the face of more severe droughts caused by climate change. Waterless toilets do exist but can be less sanitary and, for obvious reasons, much less pleasant.
"[In] the developing world, people will still want a flushing toilet," said Clement Cid, a doctoral student at Caltech who worked on the project. Hoffmann and his team created prototypes of three different toilets: a Western-style one, a water-free urinal and a squat toilet, commonly used in South and Southeast Asia.
The Gates Foundation also bestowed second- and third-place prizes to Loughborough University in Britain, for a toilet that cleans water and creates biological charcoal, and the University of Toronto, for a toilet that uses a simple sand filter and ultraviolet rays to clean and disinfect water.
The Gates Foundation has committed $40 million to address problems of water, sanitation and hygiene. The goal of the contest was straightforward and daunting.
Entrants had to build a toilet that can operate without a connection to an electrical grid or water system. Its operational costs should be less than 5 cents per day. The foundation invited 22 universities to participate by submitting proposals. The selected projects were then offered $40,000 to develop a prototype.
The waste in Caltech's photovoltaic toilet goes to a septic holding tank, where it breaks down in a low-oxygen environment. Then it drops into a solar-powered biochemical reactor, where electrodes help further purify the water and hydrogen is produced in the reaction.
The urine oxidizes to make a chlorinated byproduct that further disinfects the water. The water is filtered and stored in a holding tank where it is recycled to flush the toilets or used for irrigating crops. The hydrogen is sent to hydrogen fuel cells that turn it into electricity.
Hoffmann began working with nanoparticle semiconductors through his academic and professional career. In his past job as co-founder of Sonoma Research, he helped develop a urine-removal system for a NASA space shuttle, designed Navy wastewater treatment plants and participated in a project to create a hydrogen fuel cell for BMW cars.