Waterless, Solar-Powered Toilet Could be Answer for Communities Lacking Adequate Sanitation Systems

University of Colorado, Boulder engineers have come up with an innovative toilet design that requires no water and uses solar power to heat human waste to a high enough temperature that it sterilizes and transforms into a matter known as biochar.

This waterless, solar toilet could be introduced introduced to some of the 2.5 billion people living in communities around the world that lack adequate and safe sanitation systems.

The UC-Boulder researchers designed the toilet with a $770,000 grant from the Bill and Melinda Gates Foundation as part of the "Reinvent the Toilet Challenge," an effort to develop the next-generation toilet that can be used to disinfect both liquid and solid human waste while also producing useful end products.

The biochar - a highly porous charcoal - that the solar-powered toilet produces can be used to boost crop yields and as a means of sequestering carbon dioxide.

"Biochar is a valuable material," Karl Linden, a professor of environmental engineering at UC-Boulder and the principal investigator for the project, said in a statement. "It has good water holding capacity and it can be used in agricultural areas to hold in nutrients and bring more stability to the soils."

Linden said a soil mixture containing 10 percent biochar can hold up to 50 percent more water and increase the availability of plant nutrients.

Linden and his team's design will be exhibited in New Delhi later this month along with other recipients of the Reinvent the Toilet Challenge grant.

A total of 16 research teams are taking part in the challenge to reinvent the toilet. A full list of those teams and their ideas for a new toilet can be found here. Some of the other designs make use of biochar, while others make use of automation for cleaning and sanitization purposes, or divert urine that recycles water for flushing.

The Boulder team's toilet consists of eight parabolic mirrors that focus concentrated sunlight to a small spot on quartz-glass rod that's connected to buldles of fiber optic cable. The Sun's energy is channeled through the cables and used to heat the human waste into biochar.

"While the idea of concentrating solar energy is not new, transmitting it flexibly to a customizable location via fiber-optic cables is the really unique aspect of this project," Linden said. "We are doing something that has never been done before."