“IF THOMAS CRAPPER were around today, he would find our toilets quite familiar,” says Bill Gates, referring to the Victorian manufacturer of sanitary ware whose name has become attached to one of the body’s most fundamental functions. “They haven’t seen many advances apart from handles and paper toilet-rolls.” In fact, with the exception of S-traps to contain odours, flush toilets have changed little since Sir John Harington installed one in Richmond Palace for Queen Elizabeth I in the late 1590s.

Mr Gates considers it time for a change. On August 14th his charity, the Bill & Melinda Gates Foundation, announced the gold-, silver- and bronze-medal winners in its Reinventing The Toilet Challenge, which aims to bring safe, affordable and “sustainable” loos to the 40% of the world’s population who lack access to basic sanitation. This could help prevent many of the 1.5m childhood deaths from diarrhoea that now occur each year.

The challenge is nothing if not ambitious. It seeks a toilet that costs less than five cents per user per day to operate, that requires neither a supply of clean water nor sewerage infrastructure to take the waste away, and that will generate energy and recover salts, water and other nutrients. Even though the challenge is little more than a year old, the award winners are on track to achieve all these goals.

In third place is a toilet designed by researchers at the University of Toronto. It treats urine and faeces separately, using a material freely available in many of the world’s poorest regions: sand. Urine is filtered through sand, and the resulting fluid is sterilised with ultraviolet light. Faeces are dried slowly within the toilet before being fed into a smouldering sand-filled reactor. The system can sanitise the waste of ten people in two hours, leaving only sand and fresh(ish) water behind.

The runner-up comes from Loughborough University in Britain. A tank feeds mixed urine and faeces through a rig that heats it to 200°C under high pressure, killing pathogens. Returning the superheated mixture suddenly to atmospheric pressure causes it to separate into its liquid and gaseous components. The gas is used to heat the feed tank. The liquid is fed into a digester that produces enough methane to power the system—and some to spare.

The winning toilet is smarter still. It has been developed by Michael Hoffman of the California Institute of Technology, and has earned him the $100,000 first prize. His toilet uses solar panels to power an electrochemical system that turns waste into useful things. One is a compound which oxidises the salts in urine to generate chlorine. This creates a mildly disinfecting solution that can be used to flush the toilet. The second is hydrogen, which is suitable for cooking or for powering a fuel cell to produce electricity. The residue from the process can be used as fertiliser.

The Gates Foundation will now pay for prototypes to be tested in the field, probably of all three winners and possibly of some other ideas. Mr Gates hopes that the foundation’s reinvented toilets will start being deployed more widely in as little as two years. They will thus be able to help achieve what is the most off-track of the United Nations’ Millennium Development Goals: to halve by 2015 the proportion of people without sustainable access to basic sanitation. As the chairman of the UN Secretary-General’s Advisory Board on Water and Sanitation, the Prince of Orange, observes, “politicians and leaders worldwide don’t like to be associated with toilets, even state-of-the-art toilets. This sanitation stigma distorts international and national development agendas.”

Dr Hoffman agrees that sanitation is insufficiently sexy. He says the technology behind his solar-powered toilet had been sitting on the shelf since he demonstrated it to NASA, America’s space agency, in the early 1990s, for use on the International Space Station. “It is hard to get a scientific grant for treating faeces,” he says.

Even the Gates Foundation itself, which hands out around $3 billion each year, has devoted just $6.5m to its Reinventing The Toilet Challenge. But that will change as the project moves from conception to delivery. The foundation plans to spend up to $80m a year on sanitation, an investment that the World Health Organisation estimates will produce a return of 900% in the form of social and economic benefits from increased productivity and reduced health-care costs.