Waste-cooking solar toilet unveiled in India


March 25, 2014

The University of Colorado's solar toilet

The University of Colorado's solar toilet

A toilet project that addresses environmental and health concerns was unveiled in Delhi, India this month. Around 2.5 billion people in the world lack proper sanitation, and it’s with those people in mind that a team at the University of Colorado Boulder has designed a self-contained, solar-powered, waterless toilet. It was made possible with a grant from the Bill & Melinda Gates Foundation.

Concentrating solar power is the key technology behind the system, which is equipped with eight parabolic mirrors that catch sunlight. These focus light onto a stamp-sized spot on a quartz-glass rod, from which energy is transferred to eight bundles of fiber-optic cables, each one an amalgamation of thousands of fused fibers. Tests have shown that the fiber-optic cables can produce between 80 and 90 watts of energy each, or a total of 700 watts of energy, which is used in the reaction chamber where the waste material is treated.

In every cycle of use, a urine-diverting squat plate deposits the fecal material into a collection vessel within the reaction compartment. The urine and used hand wash water are sent to a pretreatment storage tank. The reaction compartment comprises two vessels that are alternated between "collection" and "reaction" modes via a simple carousel system that can be automated or manually controlled. Once the collection vessel is filled, it is rotated into the reaction position.

The vessel is illuminated by concentrated sunlight and heated to temperatures between 200ºC (392ºF) and 600ºC (1,112ºF) depending on the daily solar conditions. The urine/hand wash water mixture is thermally treated with a small solar heater to a temperature of 60ºC (140ºF) to 70ºC (158ºF) for up to 90 minutes. In the prototype unveiled, odor control is achieved with an exhaust fan and an in-line filtration process using the produced char as an adsorbent.

Concentrating solar power is nothing new, but transmitting solar energy to a customizable location through fiber-optic cables breaks new ground, said Karl Linden, professor of environmental engineering and leader of a team of more than 12 researchers.

The unit unveiled is designed for use by four to six people a day, but a larger version is being designed in order to meet the needs of several households. The idea is to bring the cost down to five cents a day, a target set by the Gates Foundation, which launched the Reinvent the Toilet Challenge as part of a larger effort to save the lives of 700,000 children worldwide, who die from illnesses caused by water contaminated with fecal matter.

Source: University of Colorado Boulder

About the Author
Antonio Pasolini Brazilian-Italian Antonio Pasolini graduated in journalism in Brazil before heading out to London for an MA in film and television studies. He fell in love with the city and spent 13 years there as a film reviewer before settling back in Brazil. Antonio's passion for green issues - and the outdoors - eventually got the best of him and since 2007 he's been writing about alternative energy, sustainability and new technology. All articles by Antonio Pasolini

People lacking proper sanitation probably lack it for the same reason they couldn't afford to buy this first world solution


Anaerobic digestion can treat the waste just as effectively and produce fertilizer and useful energy as a byproduct.


Please not yet another solar oven and worse this time, a solar toilet. I saw these unused in Honduras in 2000. The locals hated them. We were fools to install them.


This is a brilliant concept. Glad to know the Bill and Melinda Gates Foundation is fuelling the future. Although in the prototype stage it can revolutionise the way people treat crap.

Jitesh Naidoo

This design is grossly over-engineered. It would not be used here, would not be used in the developing nations, could not be afforded there, if they had anywhere near enough money they would buy composting toilets and then use the sizeable savings for lots of other needs. The one element that does have merit is the fused quartz joined to compacted fibre optic cable part. Interior building day-lighting could be done for new and existing buildings better than current choices. This is the better mouse-trap here and not this off-the-wall crapper.


That's some hot sh**! Assuming that it works as designed.

Post a Comment

Login with your Gizmag account:

Related Articles
Looking for something? Search our articles