Since stepping down as Microsoft CEO, Bill Gates has been hard at work trying to tackle the world's biggest health problems. One promising project that's caught his eye is the Omniprocessor, a huge machine that converts sewer sludge (yes, that means human waste) into clean drinking water, ash and electricity. Of course, Gates was keen to visit one of the facilities to see, and more importantly taste, the results for himself.

The machine, built by Janicki Bioenergy, could overhaul sewage treatment and provide access to clean water in developing countries. Too often, human waste isn't dealt with properly -- sometimes it's just dumped in the nearest river, or the ocean -- and then it makes its way back into the community's water supply. With the Omniprocessor, the sludge is boiled until it separates into solids and water vapor. The former fuels a fire inside the machine, which creates steam and then electricity, while the latter is fed through a cleaning system to produce regular old H2O. With a pilot program in Senegal scheduled for later this year, Gates is likely to be one of many enjoying the benefits of this poo-fuelled process.