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.