When Bill Gates ran Microsoft, he determined the fate of programmes worth billions of dollars, but the co-founder and former CEO of the biggest software maker turned his attention to toilets.
With 1.5 million children a year dying of diarrhoea related to poor sanitation in the developing world, billionaire Gates and his wife Melinda asked their foundation to focus on helping to create a next-generation toilet that is suitable for countries with limited access to water and sewage lines.
"The topic we are discussing today can rightly claim to be the most neglected thing in all the things that are done to help the poor," Mr Gates said on Tuesday at a ceremony to announce the top four projects at his foundation's Reinvent the Toilet Fair in Seattle.
"The toilet that was invented 200 years ago, the flush toilet, really hasn't had that many milestone advances."
The Bill and Melinda Gates Foundation gave grants to eight institutions last year to develop low-cost loos that can be operated for 5 cents a day per user, do not require a connection to a sewer or water to flush, and are hygienic and sustainable for the world's poorest populations. The projects are also supposed to look at how the waste can be used to generate energy and recover salt, water and other nutrients.
Toilets developed by the organisations that lined up funding last year, plus 27 other related projects built with the foundation's grants, were put on display. The exhibits
included faecal substitutes made from miso paste, which is meant to mimic the viscosity of human waste. The foundation purchased 50 gallons of the fake faeces for use at the expo.
Lamenting the lack of innovation in toilet design, Mr Gates invoked Thomas Crapper, the plumbing company founder who helped popularise the modern toilet. "If Crapper was born today, he'd find the toilet quite familiar," he said.
The winning entry went to the California Institute of Technology's solar-powered white ceramic toilet and stainless metal urinal combo. While it looked normal from above, underneath was a septic holding tank that separates solids and liquids before they move on to an electrochemical reactor that disinfects waste and generates hydrogen to be used as fuel.
Professor Michael Hoffman of California Institute of Technology explains his team's winning entry at the Reinvent the Toilet Fair competition. Photograph: Anthony Bolante/Reuters
Second place went to Loughborough University, in the United Kingdom, whose system is essentially a pressure cooker for human waste.
A long metal tube called a hydrothermal carbonisation reactor turns faeces into a brown dust called biological charcoal that looks and smells like coffee grounds and can be used as soil or fertiliser. The system also generates clean water from urine and faeces, as well as energy by combusting the biological charcoal.
The University of Toronto's third-place project dries and smoulders waste to sanitise it, while using a sand filter and ultra-violet light to disinfect urine.
The foundation's next step will be to decide which models are viable, and then get prototypes to test in the field over the next 15 months, said Carl Hensman, programme officer with the foundation's Water, Sanitation and Hygiene programme.
Around 2015, the foundation plans for small pilot studies in places such as sub-Saharan Africa and Bangladesh.
Bloomberg