Former Microsoft CEO and philanthropist Bill Gates has awarded a series of prizes to universities in the US, the UK, and Canada for prototypes of sustainable, eco-friendly toilets designed for use in the developing world. As part of the Bill & Melinda Gates Foundation's Reinvent the Toilet Fair, Gates awarded $100,000 to Caltech for a solar-powered, energy-generating toilet, $60,000 to Britain's Loughborough University for a toilet that converts human waste into biological charcoal, and $40,000 to the University of Toronto for a toilet that recovers clean water from feces and urine. Financed by six $400,000 grants given out last year, the prototypes are still some way from mainstream use — according to The Seattle Times, the winning design currently costs more than $1,000 per unit to produce.

While hardly a glamorous issue, the problem of defecation is an important one for many countries in the developing world, where a lack of plumbing and other infrastructure, not to mention droughts, makes conventional flush toilets impractical. "Worldwide, there are 2.5 billion people without access to safe sanitation — including 1 billion people who still defecate out in the open and more than 1 billion others who must use pit latrines," writes Gates on his Gates Notes blog. Check out the video below for more about the problem, as well as some of the ways that charitable organisations like the Gates Foundation are trying to tackle it.