American billionaire Bill Gates has given $100,000 (£63,800) to researchers to develop a solar powered toilet.

The founder of Microsoft awarded the money to the California Institute of Technology (Caltech) yesterday at the ‘Reinvent The Toilet Fair’ in Seattle hosted by his charity.

A year ago he had challenged universities to come up with a way to capture and process human waste and transform it into useful resources. The Caltech researchers’ solar toilet generates hydrogen and electricity.

Writing in a blog for the Bill & Melinda Gates Foundation website, the philanthropist (pictured at the fair yesterday, right) pointed out the importance of “providing safe sanitation for everyone in the world”.

He said flushing toilets were “pretty outdated” and argued they were too expensive and too wasteful of water.

Mr Gates wrote: “The fact that four out of every 10 people still don’t have access to flushing toilets proves that – even today – it is a solution too expensive for much of the world. And in an era where water is becoming increasingly precious, flush toilets that require 10 times more water than our daily drinking water requirement are no longer a smart or sustainable solution.”