Microsoft co-founder Bill Gates thinks one of the answers to improving health is in the bathroom.

A year ago, his foundation issued a challenge to universities to create a new toilet, launching a worldwide effort to improve sanitation.

This week the Bill & Melinda Gates Foundation announced who won the challenge.

California Institute of Technology was the big winner and was awarded $100,000 for its idea of a solar-powered toilet that generates hydrogen and electricity. The United Kingdom's Loughborough University won second place and was awarded $60,000 for a toilet that produces biological charcoal, minerals, and clean water. The University of Toronto in Canada garnered third place and $40,000 for a toilet that sanitizes feces and urine and recovers resources and clean water.

The new commodes are being showcased at a "Reinvent the Toilet Fair" Tuesday and Wednesday in Seattle.