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Caltech wins Gates Foundation toilet challenge

17 August 2012

Caltech's solar-powered toilet won the $100,000 Reinventing the Toilet Challenge issued by the Bill and Melinda Gates Foundation. The UK's Loughborough University picked up the $60,000 second prize.

Caltech's winning design

Last summer, Hoffmann, the James Irvine Professor of Environmental Science at Caltech, and his team were awarded a $400,000 grant to create a toilet that can safely dispose of human waste for just five cents per user per day. The lavatory can't use a septic system or an outside water source, or produce pollutants.

Hoffmann's proposal, which won one of the eight grants, was to build a toilet that uses the sun to power an electrochemical reactor. The reactor breaks down water and human waste into fertilizer and hydrogen, which can be stored in hydrogen fuel cells as energy. The treated water can then be reused to flush the toilet or for irrigation.

The challenge is part of a $40 million program initiated by the Gates Foundation to tackle the problems of water, sanitation, and hygiene throughout the developing world. According to the World Health Organization, 2.5 billion people around the globe are without access to sanitary toilets, which results in the spread of deadly diseases. Every year, 1.5 million people—mostly those under the age of five—die from diarrhea.

The team built a prototype inside the solar dome on the roof of Caltech's Linde + Robinson Laboratory, and after a year of designing and testing, they, along with the other grantees, showed off their creation. 

The runners up

The $60,000 second-place prize went to the UK's Loughborough University, whose toilet produces biological charcoal, minerals, and clean water. It uses a process called Continuous Thermal Hydrocarbonisation which kills all pathogens to create safe to handle, valuable material and uses power from heat generated during processing. The toilet is designed to work in both single-family and multi-user contexts with daily running costs of just a few pence per person. See Loughborough's video above.

The $40,000 third-place award went to the University of Toronto's design, which sanitises waste products and recovers resources and clean water.

The Swiss Federal Institute of Aquatic Science and Technology and their partner EOOS won $40,000 as a special recognition for their toilet interface design.


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