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Pratt, RTI to Develop Waterless Toilets

A grant from the Bill & Melinda Gates Foundation will fund development of the toilet for use in developing nations

Jeff Glass, Hogg Family Director of Engineering Management and Entrepreneurship, and RTI International researchers have been awarded a grant from the Bill & Melinda Gates Foundation to develop a toilet for use in developing nations that converts human waste into burnable fuel, stored energy and disinfected, non-potable water.

The novel waste treatment system could significantly improve public health and quality of life among people in less developed countries. Joining the Duke and RTI team in developing a prototype of a safe, sanitary and affordable waste treatment system are Colorado State University, NASA’s Ames Research Center and the U.S. Naval Research Laboratory.

The $1.5 million grant is part of the second round of the Bill & Melinda Gates Foundation’s Reinvent the Toilet Challenge, which supports efforts to create a stand-alone unit that does not require piped-in water, a sewer connection or outside electricity. To qualify, the toilet units must cost no more than 5 cents per person per day and be easy to install, use and maintain.

RTI’s design will accomplish three primary functions: disinfect liquid waste, dry and burn solid waste, and convert the resulting combustion energy into stored electricity. The system also includes innovations to improve operational utility, energy efficiency and cost.

“More than 2 billion people worldwide do not have access to safe and effective sanitation,” said Brian Stoner, Ph.D., a senior fellow in materials and electronic technologies at RTI and principal investigator on the project. “This unique design offers solutions to several problems that have plagued developing nations by providing a toilet that effectively disposes of waste without requiring outside resources. It will also have the capacity to capture and recycle water, energy and other valuable resources that are in human waste.”

The team will work closely with researchers at NASA to leverage decades of research and experience in developing waste treatment systems for spaces with similar limitations on energy and water usage.

The solid waste drying process will use a combination of mechanical, solar and thermal energy. A mechanical screw-like device will separate out liquids and begin the process of converting solid waste into combustion fuel. Solar energy, natural drafts and heat from burning waste will further aid the drying process.

As it dries, the waste will be broken down into uniform-sized pellets, which will be burned using the RTI-developed Thermoelectric Enhanced Cookstove Add-on device, a self-powered unit that captures a portion of heat and converts it into electricity. This electricity will run a combustion blower and be stored in a battery to power the water treatment functions.

Liquid waste—including urine and liquid that is removed from the solid waste—will be disinfected through electrochemical processes using diamond-based electrodes (to be developed in partnership with Advance Diamond Technologies, Inc. and Duke). The disinfected water will be suitable for use as rinse water for the toilet or as fertilizer.   

“The proposed system will take advantage of current best practices in waste management while leveraging recent innovations in electrochemical disinfection technology employing robust, low cost, conducting diamond, thin film electrodes,” said Glass, a co-investigator and technical lead for the liquid disinfection module.

RTI will also partner with Duke’s Master of Engineering Management program, leading a team of students to conduct energy balance and economic feasibility studies.

“This project is ideal for our students because it requires development of cutting edge technologies while simultaneously considering social adoption and economic feasibility issues for resource-poor environments,” Glass said. “Our MEM students bring a combination of engineering and business skills to the project along with a strong desire to have a positive impact on society, especially the developing world.”

“This project will build on RTI’s successful history of working with university, government and commercial partners in programs ranging from defense technology to global health and public policy,” Stoner said. “One of the primary strengths of our team is the integrated expertise that was assembled to tackle this very ambitious and worthwhile problem. Our team includes experts in engineering, water and sanitation, energy, and economics who have the knowledge and resources needed to transition these innovative concepts from the laboratory to prototype demonstration.”