By Simon Kuper in the FT Weekend Magazine, 10 November 2018: 

Whenever Bill Gates visits a slum, an unasked question goes around his mind. “Do you mention to each other that it doesn’t smell good, and I wouldn’t like to live here, or is that just inappropriate?” he told me in a phone interview. “We take for granted that we have a toilet right inside our household.”

In fact, it’s a luxury. Only 27 per cent of the world’s population has a home toilet that sends waste to sewers, then on to a treatment plant, estimates the World Health Organization. Three people in 10 have neither toilets nor latrines. They pay a daily price in disease and lost dignity. “Sanitation-related diseases, including diarrhoea, cholera and typhoid, kill nearly 500,000 children under age five, each year,” says the Gates Foundation. But now, thanks largely to Gates, companies are about to start selling what he terms the “reinvented toilet”. He sounds as proud of it as of the Microsoft Windows operating system that made him rich. The reinvented toilet could transform countless lives, and might even take off in wealthy countries.

Gates speaks about toilets rapidly, obsessively and with a slight squawk. He can discourse on “shit-flow diagrams” and has drunk “poop water”: excrement converted to drinkable water by new “omniprocessors”. He shrugs: “People acted like that was some surprising thing. The input into an omniprocessor is not attractive to drink, but the output is.”

The toilet has barely changed in a century. But the Gates Foundation decided that simply importing the rich-world model to poor countries wouldn’t work. Firstly, our toilets use too much scarce water. They account for nearly 30 per cent of an average home’s indoor water consumption in the US, more than any other household item, says the Environmental Protection Agency. Some older toilets use six gallons a flush.

And the developing world cannot accommodate traditional toilets. Fast-growing megacities in poor countries typically lack sewers and waste treatment plants, says Gates. “The cost to go back in [and build them], just in one Indian city, would be many billions of dollars — so it will never happen.” Even where infrastructure exists, there’s often no money for electricity or maintenance. That leaves 892 million people worldwide defecating in places such as “street gutters, behind bushes or into open bodies of water”, reports the WHO. Bill Gates on Africa’s population boom and the risk of the US turning inwards

So Gates’s foundation has spent $200m since 2011 helping to fund research and development into revolutionary new models of toilets. Now they’re here: off-grid loos that eliminate human waste, kill germs and extinguish smells on the spot, explains Gates. “Most of them, I think, have a sort of ashbox that you end up having to empty from time to time. The idea is to get these toilets into slums where there is no chance you would ever build a sanitation system.” The first versions on sale will be multi-unit public toilets. They could replace the filthy communal latrines common in Indian slums. If schools install these toilets, more girls might attend. (South African schoolchildren have drowned falling into latrines.)

But Gates sees public reinvented toilets as an imperfect solution, especially for women and children: “Particularly at night, going out to those community toilets that might not smell good, where you might not feel safe, that’s a problem.” He hopes that in the next few years, companies will be selling “the ultimate, which is the household reinvented toilet. Which is really what you want. It has to be cheap, have no smell, and it can’t require much in the way of maintenance. We have put a lot of effort into aesthetics and usability.”

Gates’s foundation is not making the toilets. Chinese companies may become the first mass producers, selling mostly in Africa and India. The global market could be worth $6bn in annual revenues, estimated the Boston Consulting Group in 2016. The problem is affordability. Gates hopes that within four years, the household reinvented toilet will cost five cents per user per day. He says: “Toilets aren’t zero cost today. People value having a good toilet. You could have pay-as-you-go solutions to help with the capital cost, as has been done for solar in Africa. We would expect that in a slum these toilets would get very high demand.”

However, Steve Sugden of the non-profit Water for People cautions that many poor families cannot afford several hundred dollars up front for a home toilet. Often, says Sugden, the women of a household think it’s worth it but the men, who control the household budget, don’t. Gates admits that household reinvented toilets might initially be bought by the richer citizens of the poor world — the Indian middle classes, for instance, or rural Chinese: “Even in China there are quite a few places that the government is saying that the way toilets work right now is completely inadequate.”

One thing Gates knows: everyone needs a toilet. “I think the key thing is to take a week to live in a place where there are cesspools to the left and the right of you, which is what slum living is like. It’s not something you ever get used to.”