The BBC reports that Bill Gates is, in a manner of speaking, flushing his money down the toilet.
His charitable organisation, the Bill & Melinda Gates Foundation, is looking for future loos that can improve sanitation around the world.
At the Reinvent the Toilet fair, hosted at its Seattle campus this week, designs included a lavatory that used microwave energy to turn poo into electricity.
Another turned excrement into charcoal, while a third used urine for flushing.
In total 28 designs were shown off at the fair and the winner was a team from the California Institute of Technology.
Led by Prof Michael Hoffman, the toilet they designed was solar-powered and generated hydrogen gas and electricity. They won a $100,000 prize.
"We couldn't be happier with the response that we've gotten," said Bill Gates (pictured presenting the award to Hoffman) at the event.
Read more on the Christian Science Monitor