Bill Gates thinks toilets are a serious business, and he’s betting big that a reinvention of this most essential of conveniences can save a half million lives and deliver $200 billion-plus in savings.

The billionaire philanthropist, whose Bill & Melinda Gates Foundation spent $200 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 fertilizer.

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

Holding a beaker of human excreta that, Gates said, contained as many as 200 trillion rotavirus cells, 20 billion Shigella bacteria, and 100,000 parasitic worm eggs, the Microsoft Corp. co-founder explained to a 400-strong crowd that new approaches for sterilizing human waste may help end almost 500,000 infant deaths and save $233 billion annually in costs linked to diarrhea, cholera and other diseases caused by poor water, sanitation and hygiene.

One approach from the California Institute of Technology that Gates said he finds “super interesting” integrates an electrochemical reactor to break down water and human waste into fertilizer and hydrogen, which can be stored in hydrogen fuel cells as energy.

Without cost-effective alternatives to sewers and waste-treatment facilities, urbanization and population growth will add to the burden. In some cities, more than half the volume of human waste escapes into the environment untreated. Every dollar invested in sanitation yields about $5.50 in global economic returns, according to the World Health Organization.

“Human waste that is properly handled can be a very economically attractive investment due to the health benefits,” said Guy Hutton, a senior adviser for water, sanitation and hygiene with Unicef in New York, in an interview. “Given the unmet need of 2.3 billion people still without basic sanitation, there is a potentially very substantial market and economic gain to be had.”

The reinvented toilet market, which has attracted companies including Japan’s LIXIL Group, could generate $6 billion a year worldwide by 2030, according to Gates.

“Innovative companies have a golden opportunity to do well by doing good,” LIXIL President Kinya Seto said in a statement. “We can help jump-start a new era of safe sanitation for the 21st century by developing solutions that can leapfrog today’s existing infrastructure, functioning anywhere and everywhere.”

Companies displaying their sanitation technologies included China’s Clear, CRRC Corp. and EcoSan; Sedron Technologies LLC from the U.S.; SCG Chemicals, a unit of Thailand’s Siam Cement Pcl; and India’s Eram Scientific Solutions Pvt, Ankur Scientific Energy Technologies Pvt, and Tide Technocrats Pvt, the Gates Foundation said in an emailed statement.

The initial demand for the reinvented toilet will be in places like schools, apartment buildings, and community bathroom facilities. As adoption of these multi-unit toilets increases, and costs decline, a new category of reinvented household toilets will become available, the Gates Foundation said. (Bloomberg)