Bill Gates thinks toilets are a serious business and he's betting big that a reinvention of this most essential of conveniences can save half a million lives and deliver $US200 billion-plus in savings.

The billionaire philanthropist, whose Bill & Melinda Gates Foundation spent $US200 million over seven years funding sanitation research, showcased some 20 novel toilet and sludge-processing designs that eliminate harmful pathogens and convert bodily waste into clean water and fertiliser.

Bill Gates says new approaches for sterilising human waste may save $US233 billion ($323 billion) annually in costs linked to diarrhoea, cholera and other diseases caused by poor water, sanitation and hygiene. Credit:AP

"The technologies you'll see here are the most significant advances in sanitation in nearly 200 years," Mr Gates, 63, told the Reinvented Toilet Expo in Beijing on Tuesday.

Holding a beaker of human excreta that, Mr Gates said, contained as many as 200 trillion rotavirus cells, 20 billion Shigella bacteria and 100,000 parasitic worm eggs, the Microsoft co-founder explained to a 400-strong crowd that new approaches for sterilising human waste may help end almost 500,000 infant deaths and save $US233 billion ($323 billion) annually in costs linked to diarrhoea, cholera and other diseases caused by poor water, sanitation and hygiene.