Concentrated Solar energy heats the fecal matter up to 750°C and produces thereby char for agricultural soil application.

The Sol-Char Toilet – is a waterless, self-contained toilet that functions off-the-grid. Concentrated sunlight is delivered to fiber optic bundles located at the focus of parabolic concentrators (see Concept Sketch). The fiber optic cables are fed to the reaction compartment of the Sol-Char where the various individual cables are terminated at an outer or “solar” lid positioned over the waste collection container. The innovative transmission of concentrated solar power illuminates the inner collection container and disinfects the waste though conduction, convection, and radiation heat transfer. The reaction compartment comprises two or more containers that are alternated between “collection” and “reaction” modes via a simple carousel system that can be automated (powered with photovoltaic energy) or manually controlled. The reactor is designed to achieve high temperatures (300oC to 750oC) and produces a safe and useable product.

On-going research activities include:
• Solar collection and transmission optimization
• Reactor modeling and fabrication
• Char product evaluation and testing
o Hydrothermal carbonization (HTC) and dry pyrolysis chars will be compared
o Dry pyrolysis will also be evaluated with mixed waste and urine diversion to determine the best utilization of nutrients
o Adsorption studies will be conducted in the liquid and gas phase to determine if the char can be further enriched with NPK
• Means for odor control, gas utilization, and final product storage
• User interface and safety features
Our prototype development is underway and we are excited to further advance this technology. We welcome your feedback and comments!

Detailed location of main activity Countries of activity


Our goal during this phase 1 of research is to develop a functioning toilet prototype that will provide a scientific basis for utilizing concentrated solar energy to safely disinfect and transform human waste into valuable end products (such as char for agricultural soil application).
Further information

This was an RTTC grant.

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