Come August and he will host the world's best scientists and engineers in Seattle, US, to see if they can design cheap, dry toilets which don't hitherto exist.
This public health innovation, says the co-chair of Bill and Melinda Gates Foundation, is his "ultimate dream" though it is "not the only one".
"The ultimate dream is this so-called dream - that of a toilet design," Gates told a select group of journalists here today, but added that it was not "the only dream".
Gates said, "There's expertise all over the world in this. We're putting money and asking people to come up with a cheap design. And, actually this August we have scientists, engineers from all over the world come and tell us (on this)."
He said his Foundation has thrown up this challenge for quite some time now and hopes to get his "dream toilet" soon.
"It should be possible to have a toilet that does not require running water, whose cost is very low and whose smell characteristics are as good or better than a flush toilet. But, it doesn't exist yet," he said.
He added, "Let's see what they come up with. If they don't come up with anything then we will put the challenge out again. Maybe get a new group of scientists to work on it."
Gates is in India to review the projects being run by his Foundation.
Low cost dry toilets, if created, would prove a boon to public health in the developing countries where lack of hygiene is a principal driver of disease and malnutrition.
In India alone, only 46.9 per cent of the total 246.6 million households have toilets at home. Of the rest, 3.2 per cent use public toilets. If that was less, 49.8 per cent use open spaces for defecation.
The Rural Development Ministry under Jairan Ramesh is also launching a campaign to make India open defecation free. MORE
