Pressure cooker on steroids treats human waste

Jul 09, 2013

Like alchemists, engineers from Duke University and the University of Missouri are developing a process to turn sewage into drinkable water, energy and useful byproducts at a cost of less than a nickel per person per day.

In addition to the technological aspects of the project, the researchers are investigating plans to make the technology economically self-sustaining in , since many areas with the greatest are typically urban and low-income. The new approach will operate without connections to water, sewer or electrical lines.

The Bill & Melinda Gates Foundation is supporting the team's efforts with a $1.18 million grant as part of the Reinvent the Toilet Challenge. Researchers expect that a working prototype will have been constructed at Duke in 15 months. It will be tested first in the U.S. and then deployed in South Africa, India or Ghana, depending on the results of ongoing feasibility studies.

"We not only want to design and build the right piece of equipment to improve sanitation, but one that is well-integrated into its community, both economically and socially," said Marc Deshusses, professor of civil and environmental engineering at Duke's Pratt School of Engineering and principal investigator of the project. "We expect the end products of the process will be used by the communities to build businesses that make it self-sustaining."

The proposal is to produce a self-contained "toilet" unit that can be transported to locations overseas in a 20-foot container. The prototype will have the capacity to handle the daily fecal waste of about 1,200 users collected from community centers or neighborhood latrines directly piped or transported to the facility for processing.

Deshusses, who received a grant from the Gates Foundation in 2011 to develop a novel sanitation system for the developing world, describes the technology that powers the process as a "pressure cooker on steroids." The technology behind the proposal is known as supercritical water oxidation (SCWO).

"When you heat water above 705 degrees Fahrenheit under pressure, it becomes a 'supercritical fluid,' thicker than steam but less dense than water," said co-principal investigator William Jacoby, associate professor of biological engineering at Missouri and director of its Carbon Recycling Center. "When we add oxygen to the process, it quickly 'burns up' any carbonaceous materials, including human waste."

Jacoby said that the SCWO process has been used to treat hazardous wastes, such as polychlorinated biphenyls (PCBs) and chemical weapons.

"In terms of human waste, the process is faster than other treatment methods, and it produces hot, and potable, water and excess energy in the form of heat," Jacoby said.

The reaction produces clean water, heat, carbon dioxide, benign salts and nitrogen, which can be used by the community or turned into business opportunities to support the system, the researchers said. For example, the could be used in community showers or clothes-washing facilities and the heat could generate electricity.

While one team of engineers works on the technical aspects of the project, another will work in parallel on developing business plans to make the endeavor feasible not only economically, but also from a regulatory and cultural standpoint.

"The technology to treat the waste is not necessarily low-tech, but it is very sustainable, with no adverse environmental impacts, so our challenge is to make it cost-effective and self-sustaining," said co-principal investigator Jay Golden, who directs Duke's Center for Sustainability & Commerce. He is also on the faculty of Pratt and Duke's Nicholas School of the Environment.

"By working with people on the ground, we'll develop a plan for linking the system and its to specific community needs," Golden said. "More broadly, we'll try to identify other regions where our model can be effectively duplicated."

Explore further: New solarclave uses nanoparticles to create steam

add to favorites email to friend print save as pdf

Related Stories

Cranfield to develop innovative waterless toilet

Aug 16, 2012

Cranfield University is to develop a waterless, hygienic toilet with the potential to transform the lives of the 2.5 billion people worldwide without access to basic sanitation, thanks to $800,000 funding from the ‘Re ...

New solarclave uses nanoparticles to create steam

Jul 09, 2013

(Phys.org) —A team of researchers at Rice University has developed a solar powered autoclave based on solar energy and metal and carbon nanoparticles. In their paper published in the journal Proceedings of ...

New toilet technology after 150 years of waste (Update)

Aug 14, 2012

(AP) — These aren't your typical loos. One uses microwave energy to transform human waste into electricity. Another captures urine and uses it for flushing. And still another turns excrement into charcoal.

Recommended for you

Obama launches measures to support solar energy in US

23 hours ago

The White House Thursday announced a series of measures aimed at increasing solar energy production in the United States, particularly by encouraging the installation of solar panels in public spaces.

Tailored approach key to cookstove uptake

23 hours ago

Worldwide, programs aiming to give safe, efficient cooking stoves to people in developing countries haven't had complete success—and local research has looked into why.

Wireless power transfer achieved at five-meter distance

23 hours ago

The way electronic devices receive their power has changed tremendously over the past few decades, from wired to non-wired. Users today enjoy all kinds of wireless electronic gadgets including cell phones, ...

User comments : 0

More news stories

Under some LED bulbs whites aren't 'whiter than white'

For years, companies have been adding whiteners to laundry detergent, paints, plastics, paper and fabrics to make whites look "whiter than white," but now, with a switch away from incandescent and fluorescent lighting, different ...

Vietnam battles fatal measles outbreak

Vietnam is scrambling to contain a deadly outbreak of measles that has killed more than 100 people, mostly young children, and infected thousands more this year, the government said Friday.