(757a) A Finite Element Heat Transfer Model for the Solar-Driven Pyrolysis of Untreated Human Feces

Currently, 2.6 billion people on the planet do not have access to adequate sanitation and many communities in the developing world have neither the facilities nor the resources to properly treat human waste, leading to open defecation posing enormous public health risks as well as issues related to individual dignity and safety. Sanitation is not a problem unique to developing countries – modern sanitation processes are also unsustainable due to their often massive requirements for energy and water. Alternative waste treatment and conversion methods are likely to be incorporated as the demand for space and fresh water increases throughout the world. The Sol-Char Toilet, a solar-powered waste treatment technology developed at the University of Colorado Boulder, takes advantage of our most abundant renewable resource: the sun. In the Sol-Char Toilet, concentrated solar power (CSP) is transmitted through fiber optic cables to drive pyrolysis of human waste, converting a hazardous and unusable material to biochar. When compared to other biomass materials human feces are a non-homogeneous and complex biomass material with exceptionally high water content, resulting in unique heat transfer phenomena as a result changing domain shape, varying thermophysical properties, and chemical reactions. In this presentation, the validity and accuracy of a finite element heat transfer model that accounts for changing mass and domain shape, variable thermophysical properties and power supply (direct normal irradiance as measured in “on-sun” validation experiments) and reaction kinetics will be discussed.