Scientists from around the world, including a team from London, have been taking part in a competition to reinvent the toilet for the 2.5 billion people around the world who do not have access to modern sanitation.
The competition, run by the Bill and Melinda Gates Foundation, has selected a number of projects that will get more funding to takes their ideas from labs into cities. The prototypes will be tested within three years.
The challenge for the team of scientists was to invent a toilet:
- that operated without running water
- that did not need electricity
- that did not rely on a septic system
- that did not discharge pollutants
- capable of operating at a cost of 3p per day
- with the ability to capture energy or other resources
Microsoft mogul Mr Gates said he was delighted with the response.
Most of the toilets on display at the foundation's headquarters in Washington turned solid waste into energy.
One prototype uses microwave energy to transform human waste into electricity, another captures urine and uses it for flushing and another turns excrement into charcoal.
The United Nations estimates disease caused by unsafe sanitation results in about half the hospital admissions in the developing world.
About 1.5 million children die each year from diarrhea but scientists believe most of these deaths could be prevented with proper sanitation plus safe drinking water and improved hygiene.
Chris Elias from the foundation said the challenge was critical as water is becoming an increasingly valuable commodity, that 40% of people in the world do not have adequate access to.
The Gates foundation launched the competition almost a year ago. Since then they have provided more than $370 million in funding to scientists committed to reinventing the toilet.
The fair this week will be attended by future financial partners like UNICEF and Oxfam.