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Solar-Powered Toilet That Can Turn Waste Into Biochar

A toilet that can transform human waste into biochar, powered by nothing but the sun, has been developed by researchers at the University of Colorado Boulder.

The new technology was designed to address some of the sanitation issues that are common in many developing countries — and thereby help to protect local water supplies, and limit the spread of waterborne illnesses and diseases.

Image Credit: UC Boulder

Image Credit: UC Boulder

The self-contained unit works by using the energy of the sun, concentrated by eight parabolic mirrors, to heat up a quartz-glass rod that’s connected to eight bundles of fiber-optic cables, which then heat up the reaction chamber. The temperature in this chamber can reach over 600 degrees Fahrenheit — hot enough to sterilize human waste and produce biochar.

This new system was built and designed as part of the Gates Foundation’s “Reinvent the Toilet Challenge” using a $777,000 grant from the Bill & Melinda Gates Foundation. The ‘challenge’ was created as a means of developing solutions to the problems associated with human waste pollution. For example, more than 700,000 children die every year as the result of exposure to food and water tainted with pathogens from fecal matter. A cheap, effective means of dealing with human waste could go a long way towards limiting those numbers.

As far as the other side of this equation — for those that don’t know, ‘biochar’ is the term used to describe charcoal when it’s used for a number of specific purposes, such as a soil amendment. The researchers note that the widespread use of biochar could be used to both boost crop yields and to sequester carbon dioxide.

“Biochar is a valuable material,” stated researcher Karl Linden. “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. A soil mixture containing 10% biochar can hold up to 50% more water and increase the availability of plant nutrients. Additionally, the biochar can be burned as charcoal and provides energy comparable to that of commercial charcoal.”

The University of Colorado — Boulder provides more:

Tests have shown that each of the eight fiber-optic cables can produce between 80 and 90 watts of energy, meaning the whole system can deliver up to 700 watts of energy into the reaction chamber, said Linden. In late December, tests at CU-Boulder showed the solar energy directed into the reaction chamber could easily boil water and effectively carbonize solid waste.

While the current toilet has been created to serve four to six people a day, a larger facility that could serve several households simultaneously is under design with the target of meeting a cost level of five cents a day per user set by the Gates Foundation.

The CU-Boulder team is now applying for phase two of the Gates Foundation Reinvent the Toilet grant to develop a field-worthy system to deploy in a developing country based on their current design, and assess other technologies that may enhance the toilet system, including the use of high-temperature fluids that can collect, retain and deliver heat.

Interesting technology, though I do have questions about how likely it is to enter widespread use.

What do you think?

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Written By

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.


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