One of the development projects that I keep an eye on is the Bill and Melinda Gates’ Foundation challenge to reinvent the toilet. It launched in 2011 and while I don’t think all the inventions that have come out of it are practical for the poorest who need them most, there’s no doubt that it’s kicked off a wave of new ideas. With each passing year new toilets have been developed, and the most promising are now testing in South Africa.

This week saw the first Reinventing the Toilet Expo in Beijing, and Gates has been talking about what the project has generated so far. It’s an inspiring story, and a necessary one. It isn’t going to be possible to deliver traditional flushing toilets to everyone in the world – they’re just too wasteful of clean water. But what if there are better ways of creating a toilet, ways that…