Available Technology

Sol-Char: Producing Char from Waste using Solar Energy

A recent “Reinvent the Toilet Challenge” put forth by the Bill & Melinda Gates Foundation called for researchers to develop sanitation solutions that are affordable and desirable to use, render fecal waste harmless within a short time-span, are self-contained without the need for flush water or electricity, and produce valuable end products. Current waterless toilets – such as dry pit latrines, ventilated improved pit (VIP) latrines, and composting toilets – fall short of these ideals. Dry pit latrines and VIPs are plagued with difficulties associated with the removal of contents from full pits, and the need to treat the waste offsite once it is removed poses additional risks to public health and the environment. Composting toilets require an external power source or intensive user input in order to properly maintain the compost, are often associated with undesirable odors, and require extended lengths of time before the waste is rendered safe and suitable for use as a soil amendment in agriculture. A University of Colorado research group led by Alan Weimer has taken on the challenge of “Reinventing the Toilet.” In September of 2012, this group (with Principal Investigator Karl Linden) received funding from the Bill & Melinda Gates Foundation to develop a novel toilet that produces char from waste using solar energy.
Patent Abstract: 
This toilet, the Sol-Char, is a waterless, self-contained toilet that can function completely off-the-grid by capturing readily available solar energy. Concentrated sunlight is delivered to fiber optic bundles located at the focus of parabolic concentrators; 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 solar power illuminates the inner collection container and disinfects the waste though convection and radiation heat transfer. The reaction compartment comprises two 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 with minimal heat loss due to specially designed insulation and produces a safe and useable product. The Sol-Char toilet can be developed for virtually any number of users with solar power input scaled accordingly. Means for innovative odor control and final product storage/collection (for later use as a soil amendment) are also being developed as a part of the Sol-Char.
Internal Laboratory Ref #: 
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