"Parents enroll their kids here because of our child-friendly toilets," says Eunice, the co-founder of a Kenyan school with latrines designed specially for kids. Frederic Courbet/WSUP/Panos hide caption

itoggle caption Frederic Courbet/WSUP/Panos

More than 170 volunteers in the Brattleboro, Vt., area have contributed urine to the Rich Earth Institute field trials. Mike Earley/Courtesy of Rich Earth Institute hide caption

itoggle caption Mike Earley/Courtesy of Rich Earth Institute

Contaminated water can spread diseases like cholera and typhoid. A new project aims to provide water filters in the form of an educational book. Soe Than Win/AFP/Getty Images hide caption

itoggle caption Soe Than Win/AFP/Getty Images

A boy collects water at a new spigot in Shululu, Tajikistan. Before the government built a new water system, villagers were allocated half-hour time slots to collect water from a trickling tap. Jason Beaubien/NPR hide caption

itoggle caption Jason Beaubien/NPR

A young boy plays on a commode during an event for World Toilet Day in New Delhi in November. An estimated 131 million Indian homes don't have a latrine or a clean toilet. Raveendran/AFP/Getty Images hide caption

itoggle caption Raveendran/AFP/Getty Images

Bill Gates, co-founder of the the Bill & Melinda Gates Foundation, checks out a toilet demo at the Reinvent the Toilet Fair in Seattle, Wash. The festival featured prototypes of high-tech toilets developed by researchers around the world. Bill & Melinda Gates Foundation hide caption

itoggle caption Bill & Melinda Gates Foundation