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A worker in a slum in Nairobi, Kenya, tries to unclog a pit latrine, before loading a cart and dumping the effluent from slum pit latrines into a local watercourse. The Reinventing the Toilet Challenge hopes to replace this kind of toilet with one that quickly converts urine and feces into clean water, mineral ash fertilizer, carbon dioxide and energy. ((Khalil Senosi/Associated Press))

Cheap, waterless toilets that can turn human waste into clean water and fertilizer within 24 hours are being designed and built by eight engineering teams around the world, including one from Canada.

The goal of the Bill & Melinda Gates Foundation's $3-million Reinventing the Toilet Challenge is to bring affordable, sustainable human waste treatment to the 2.6 billion people in the developing world — about 40 per cent of the world's population — who have no access to flush toilets. That, in turn, is expected to reduce the number of children who die each year of diarrheal diseases —  a figure reported by the Gates foundation to be around 1.5 million.

"I think it's a really important problem," Yu-Ling Cheng, the director of the University of Toronto's Centre for Global Engineering, said Wednesday. She is leading one of the eight teams that won a $400,000 grant to turn their proposed toilet design into a prototype within one year. All eight prototypes will be displayed at a showcase in Seattle next summer.

Reinventing the Toilet Challenge

The Reinventing the Toilet Challenge was announced by the Bill & Melinda Gates Foundation Tuesday in Kigali, Rwanda, at the 2011 AfricaSan Conference, which focuses on sanitation and hygiene. It was among $42 million in new grants from the foundation targeting sanitation and clean water.

 The other teams selected to participate are:

  • California Institute of Technology in the U.S.
  • Delft University of Technology in the Netherlands.
  • Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz (EAWAG) in Switzerland.
  • National University of Singapore.
  • University of KwaZulu-Natal in South Africa.
  • WEDC at Loughborough University in the U.K.
  • Stanford University in the U.S.

The toilet cannot be hooked up to water, sewage or power lines and must cost less than five cents per user per day. It must convert urine and feces into clean water, mineral ash fertilizer, carbon dioxide and energy.

It sounds as though the goal is to "create a magic toilet," Cheng acknowledged in a video interview posted on the University of Toronto website.

But her team has already come up with a design that they think will address all the criteria. It includes components that:

  • Dry the waste without chemicals, using a physical process.
  • Disinfect it using ultraviolet light.
  • Filter the liquid using a membrane.
  • Smoulder the solid waste "like charcoal briquettes in a barbeque."

"They're all very inexpensive," Cheng said.

She added that she can't provide too many more details in order to protect the potential intellectual property value of the designs, so businesses will have confidence they can profit by manufacturing them.

While the project doesn't yet have any business partners, Cheng said she received some inquires about the project Wednesday after the news first hit the media.

'It turned our thinking upside down'

The University of Toronto was one of 21 schools invited to submit a proposal. Prior to the invitation, most of the engineers involved had never thought about toilets before, Cheng said.

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A boy stands at a public toilet at Kibera slum in Nairobi. (Noor Khamis /Reuters)

"It turned our thinking upside down," she added, "because if you're designing for something in the First World, you don't even think that you wouldn't have power and you wouldn't have water."

The ability to treat waste within 24 hours is also important because most existing "green" toilets rely on composting, which takes a long time.

"While the human waste is sitting around, it will attract bugs, vermin, bacteria will grow and it's not a healthy situation," Cheng said. It's a particularly bad problem in crowded areas such as urban slums or areas where heavy rains can cause flooding that spreads human waste.

Besides the waste processing itself, the group needs to make sure the toilet is safe and robust.

"What if some kid throws a toy in there or decides to play with it?"

Developers also face cultural challenges. For example, Cheng said, people who grow up using an open field or a stream as a toilet may find it strange to use an indoor facility.

The team plans to do field tests of their prototype in Bangladesh within the next year to ensure their design is culturally appropriate. Cheng said a radical new toilet design could benefit far more people than just those in the developing world.

It could be used at campsites or outdoor events such as festivals and concerts. Or it may even have wider applications.

She said the way First World nations, such as Canada, treat human waste "is kind of ridiculous when you think about it." Water clean enough to drink is used to flush human waste away, then transport it long distances for sewage treatment.

"All that is very wasteful in terms of both money and energy. It actually means a lot of carbon emissions," she said. "Maybe once we come up with a toilet that really works, we wouldn't need this network of water and sewage in order to treat our human waste."