Microsoft co-founder Bill Gates has launched a search for a new toilet better suited to developing countries to help prevent disease and death.

A charitable foundation founded by Gates and his wife kicked off a "Reinvent the Toilet Fair" in Seattle and awarded prizes for promising innovations.

"Toilets are extremely important for public health and, when you think of it, even human dignity," Gates said.

"The flush toilets we use in the wealthy world are irrelevant, impractical and impossible for 40 per cent of the global population, because they often don't have access to water, and sewers, electricity, and sewage treatment systems."

The Toilet Fair was described as a swirl of about 200 inventors, designers, investors, partners and others passionate about creating safe, effective, and inexpensive waste management systems.

Universities from Britain, Canada, and the United States were awarded prizes in a competition launched a year ago challenging inventors to come up with a better toilet.

First place went to the California Institute of Technology for designing a solar-powered toilet that generates hydrogen gas and electricity.

Loughborough University came in second for a toilet that transforms waste into biological charcoal, minerals, and clean water.

Third place went to the University of Toronto for a toilet that sanitises human waste and recovers minerals and water.

Gates said approximately 2.5 billion people worldwide do not have access to safe sanitation systems and this contributes to severe health problems.

"Beyond a question of human dignity, this lack of access also endangers people's lives, creates an economic and a health burden for poor communities, and hurts the environment," Gates said.

Food or water tainted with faecal matter causes intestinal diseases that kill 1.5 million children annually - a figure higher than deaths from AIDS and malaria combined, according to Gates.

"Inventing new toilets is one of the most important things we can do to reduce child deaths and disease and improve people's lives," Gates said.

"It is also something that can help wealthier countries conserve fresh water for other important purposes besides flushing."

AFP