Wednesday, Bill Gates sent out a tweet to remind people about that time he drank poop water.
Last November, Gates visited a facility in Washington state that burns human waste to produce water, electricity and ash. The Omni Processor, a Gates Foundation project, helps solve the problem of poor sanitation facing many poor countries, by taking human waste out of streets and streams and turning it into something useful.
In January, Gates posted a video of himself at the processor, drinking the product of what had been, five minutes earlier, human feces. "It's water!" he said after taking a sip.
Now, the Janicki Omni Processor (JOP) is being test in Dakar, Senegal, where 1.2 million people are not on a sewer line, and human waste is often manually transported in buckets from overflowing pits outside homes.
Manual emptying spreads disease, explained Mbaye Mbeguere, of Senegal's National Institute of Sanitation, in another video Gates released this week.
"Right now we cannot remove the pathogen. This is why the Omni Processor is very important," he said.
The JOP is already treating one-third of the sludge in the city of Dakar and Gates said it is "working as predicted."
Other processors are being developed, as well. Worldwide, at least 2 billion people lack adequate sanitation facilities, leading to diseases that kill 700,000 children each year, according to Gate's post. "The idea behind every Omni Processor design is to solve this problem by making sanitation affordable for the poor."
The next version will burn garbage in addition to human waste.