Reinventing the toilet

University of Colorado team uses the power of the sun to turn human waste into fuel

Courtesy of University of Colorado

Karl Linden and his research team are not reinventing the wheel, but they are trying to reinvent the toilet.

It began several years ago for Linden, a professor of environmental engineering at the University of Colorado Boulder, in a class he taught about water sanitation and hygiene. He gave a short assignment about potential global health initiatives.

“I realized how many great ideas the students came up with,” Linden says about the student’s responses.

A year later, Linden got together with environmental engineering professor R. Scott Summers and chemical and biological engineering professor Al Weimer to submit a grant proposal to the Bill & Melinda Gates Foundation’s Reinvent the Toilet Challenge, which asked researchers around the world to create toilets that sterilize human waste without outside electricity, sewer or water sources — all for less than 5 cents per user per day.

The idea also gained the attention of the Engineering for Developing Communities Program at the university, as it applies engineering skills while learning about social, political and sustainability aspects of the work they do, which Linden said are not learned in the regular engineering program.

Linden received the first grant in 2012 for $770,000, along with a second grant in 2013 for $1 million from the Gates Foundation to further develop the toilet.

“You need an assessment of what the community wants,” says Linden.

“If you don’t meet their needs, what you are going to do won’t work.”

According to the Gates Foundation website, 2.5 billion people worldwide don’t have access to safe, affordable and sustainable toilets.

“Urban areas have sewers,” says Michael Hoffmann, the James Irvine professor of environmental science at the California Institute of Technology, “but that requires a huge subsurface infrastructure and electricity for pumps and aeration.”

Without proper waste sanitation, food and water tainted with fecal matter results in the deaths of roughly 1.5 million children each year.

Linden’s Sol-Char toilet turns human waste into biochar and fertilizer utilizing only the power of the sun.

Solar panels focus light onto fiber optic cables, which carry the sunlight to the waste-holding chamber, providing heat to create the biochar.

Biochar is a highly porous charcoal, the result of highly heated human waste.

It can be mixed with soil to increase nutrients and water retention, increasing crop yields and removing carbon dioxide, a greenhouse gas, from the atmosphere. Biochar can also be burned for fuel like traditional charcoal.

According to the World Health Organization, every $1 investment to improved sanitation has a return of $5 to $28 in social and economic benefits due to increased productivity, reduced healthcare costs, and preventing illness, disability and early death.

Working with the Gates Foundation is “totally unlike any organization that provides funding for the university,” says Linden. “Usually your goal is not to build something.”

“We’re not trying to beat someone else out,” Linden says about the Gates Foundation challenge, “It’s a pretty high order to meet.”

Linden said the Gates Foundation is not looking for one team to make the perfect toilet, rather research a variety of ideas and solutions to sanitation.

Linden — and on average 12 other professors, graduate and undergraduate students — have been working on the project since September 2012. This group is much larger than the average two- to three-person groups Linden normally sees.

“I love the project because it’s so challenging,” says Elizabeth Travis, a research assistant who is working toward a master’s degree in the engineering college’s Mortenson Center in Engineering for Developing Communities. “You’re forced to meet these challenges within a specific time frame.”

Hoffmann and his team at CalTech also received a grant from the Reinvent the Toilet Challenge in 2012.The Caltech toilet turns human waste into fertilizer and hydrogen. The hydrogen can be used as fuel to power hydrogen fuel cells.

Hoffmann has been working on semi-conductor systems, the main component of his team’s toilet, for over 30 years.

“I had that vision for a long time,” says Hoffman on utilizing his semi-conductor research. “I was just waiting for the right application to come along.”

Hoffmann has received continuing grants from the Gates Foundation, along with support from kitchen and bathroom manufacturer Kohler Co. He currently has two units open to the public, one undergoing testing in Aminabad, India, and another on the Mahatma Gandhi University campus in Kottayam, India.

As for Linden and his team, they recently attended the Reinvent the Toilet Fair 2014 in New Dehli, India to showcase a working prototype of their Sol-Char toilet.

While the toilet successfully processed synthetic human waste into biochar, it did fall short on meeting costs for a single house, says Linden, but did meet the goal for communal use.

This summer is a turning point in Linden’s research and development. The Gates Foundation grant is due to last until September, and Linden says he and his team would “love” to continue to work on the many challenges still facing the Sol-Char toilet.

“The next goal is how cheap can we make it,” says Linden.

“It’s too flashy,” says Linden, about the solar panels. Reducing the flashiness and streamlining the design will deter theft, making it safer for users to have at their residence.

Linden said he would also like to see the toilet be usable in areas of lower sunshine and have the entire process of waste sanitation shortened from its current 24-hour timeframe.

Linden is pursuing several different options for the Sol-Char toilet. He is looking for another Gates Foundation grant recipient to team up with, or other existing projects going on, such as Sanergy, a Kenya-based, large-scale Porta potty system, to integrate the on-site sanitation process.

Linden also said he is in contact with national parks in Colorado and outdoors companies to provide the Sol-Char toilets in the Rocky mountain region.

While the future of the Sol-Char toilet remains uncertain, Linden said it is still important at this point to refine the research and prepare it for publication, allowing other organizations and research groups to access the information.

While Linden hopes to continue improving the Sol-Char toilet, he says the research is still an important step in “pushing the envelope on what’s out there.”