News / Science & Technology

Microbes Produce Electricity from Sewage

A microbes clings to a carbon filament, serving as an efficient electrical conductor. (Xing Xie, Stanford Engineering)
A microbes clings to a carbon filament, serving as an efficient electrical conductor. (Xing Xie, Stanford Engineering)

Related Articles

Man-Made Earthquakes on the Rise

In the US, there were more than 300 earthquakes above magnitude 3.0 from 2010 to 2012

Hydrogen Fuel Closer to Reality

Commercialization of such a solar-thermal reactor is likely years away
VOA News
Researchers have devised a way to generate electricity using raw sewage and special bacteria.

Engineers at Stanford University call the invention a “microbial battery” and hope one day the technology will be suitable for use at sewage treatment plants.

For now, the prototype is about the size of a D-cell battery and looks like a “chemistry experiment with two electrodes, one positive, the other negative, plunged into a bottle of wastewater.”

Engineers at Stanford University have extracted electricity from raw sewage. (Xing Xie, Stanford Engineering)Engineers at Stanford University have extracted electricity from raw sewage. (Xing Xie, Stanford Engineering)
x
Engineers at Stanford University have extracted electricity from raw sewage. (Xing Xie, Stanford Engineering)
Engineers at Stanford University have extracted electricity from raw sewage. (Xing Xie, Stanford Engineering)
Inside that murky vial, attached to the negative electrode like barnacles to a ship's hull, an unusual type of bacteria feast on particles of organic waste and produce electricity that is captured by the battery's positive electrode.

"We call it fishing for electrons," said Craig Criddle, a professor in the department of civil and environmental engineering.

The electrons come from exoelectrogenic microbes – organisms that evolved in airless environments and developed the ability to react with oxide minerals, rather than breathe oxygen as we do, to convert organic nutrients into biological fuel.

For years, scientists have tried to tap the energy produced by these creatures, but until now it has proved challenging.

The Stanford researchers approach was new.

At the battery's negative electrode, colonies of wired microbes cling to carbon filaments that serve as efficient electrical conductors.

"You can see that the microbes make nanowires to dump off their excess electrons," Criddle said. To put the images into perspective, about 100 of these microbes could fit, side by side, in the width of a human hair.

As these microbes ingest organic matter and convert it into biological fuel, their excess electrons flow into the carbon filaments, and across to the positive electrode, which is made of silver oxide, a material that attracts electrons.

The electrons flowing to the positive node gradually reduce the silver oxide to silver, storing the spare electrons in the process.

According to Xing Xie, an interdisciplinary researcher, after a day or so the positive electrode has absorbed a full load of electrons and has largely been converted into silver.

At that point it is removed from the battery and re-oxidized back to silver oxide, releasing the stored electrons.

The battery, scientists say, is about 30 percent efficient in extracting the energy from waste water. While that may sound small, it is roughly the same efficiency as the best commercially available solar cells.

And while waste water will never offer the same potential solar energy could, the Stanford researchers say it’s worth pursuing because at the very least, it could offset some of the electricity used to treat sewage, or about  3 percent of the total electrical load in developed nations.

One drawback with the battery is the expense of silver.

"We demonstrated the principle using silver oxide, but silver is too expensive for use at large scale," said Yi Cui, an associate professor of materials science and engineering.

"Though the search is underway for a more practical material, finding a substitute will take time."

You May Like

Nigeria Incumbent in Tight Spot as Poll Nears

Muhammadu Buhari is running a strong challenge to Goodluck Jonathan, amid a faltering economy and Boko Haram security worries More

Video Liberia's Almost Last Ebola Patient Grateful but Still Grieving

Beatrice Yardolo tells VOA that despite her fame, life is still a struggle as she waits for government's promise of support to arrive More

Video Cambodian Land Grabs Threaten Traditional Communities

At least seven different indigenous groups in Ratanakiri depend mainly on forest products for their survival, say they face loss of their land, traditional way of life More

This forum has been closed.
Comment Sorting
Comments
     
by: Christian from: Colombia
September 17, 2013 8:51 PM
That´s one of the most smart and necessary inventions that human being have done until now because in this moment we just need to protect the environment all people even in Colombia are in emergency about the environment without oxygen it´s imposible to survive.

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Liberia's Almost Last Ebola Patient Grateful but Still Grievingi
X
Benno Muchler
March 26, 2015 3:41 PM
Beatrice Yardolo was to make history as Liberia’s last Ebola patient. Liberians recently started counting down 42 days, the period that has to go by without a single new infection until the World Health Organization can declare a country Ebola-free. That countdown stopped on March 20 when there was another new case of Ebola, making Yardolo’s story a reminder that Ebola is far from over. Benno Muchler reports from Monrovia.
Video

Video Liberia's Almost Last Ebola Patient Grateful but Still Grieving

Beatrice Yardolo was to make history as Liberia’s last Ebola patient. Liberians recently started counting down 42 days, the period that has to go by without a single new infection until the World Health Organization can declare a country Ebola-free. That countdown stopped on March 20 when there was another new case of Ebola, making Yardolo’s story a reminder that Ebola is far from over. Benno Muchler reports from Monrovia.
Video

Video Cambodian Land Grabs Threaten Traditional Communities

Indigenous communities in Cambodia's Ratanakiri province say the government’s economic land concession policy is taking away their land and traditional way of life, making many fear that their identity will soon be lost. Local authorities, though, have denied this is the case. VOA's Say Mony went to investigate and filed this report, narrated by Colin Lovett.
Video

Video US, South Korea Conduct Joint Military Exercises

The Eighth U.S. Army Division and the Eighth Republic of Korea Mechanized Infantry Division put on a well orchestrated show of force for the media this week during their joint military training exercises in South Korea. VOA’s Seoul correspondent Brian Padden was there and reports the soldiers were well disciplined both in conducting a complex live fire exercise and in staying on message with the press.
Video

Video Space Program Status Disappoints 'Last Man on the Moon'

One of the films that drew big crowds last week at the annual South by Southwest festival in Austin, Texas, tells the story of the last human being to stand on the moon, U.S. astronaut Eugene Cernan. It has been 42 years since Cernan returned from the moon and he laments that no one else has gone there since. VOA’s Greg Flakus reports.
Video

Video Young Filmmakers Shine Spotlight on Giving Back

A group of student filmmakers from across the United States joined President Barack Obama at the White House this month for the second annual White House Student Film Festival. Fifteen short films were officially selected from more than 1,500 entries by students aged 6 through 18. The filmmakers and their families then joined the president and a group of celebrities for a screening of their films. VOA’s Julie Taboh reports.
Video

Video VOA Exclusive: Interview with Afghan President Ashraf Ghani

Afghan President Ashraf Ghani, during his first visit as president to Washington, gave a one-on-one interview with VOA Afghan Service reporter Said Suleiman Ashna, about his request for a change in U.S. troop levels, the threat from the Islamic State, and repairing relations with the United States and Pakistan. The interview was held at Blair House, late Sunday, in Pashto.
Video

Video California Science Center Tells Story of Dead Sea Scrolls

The ancient manuscripts were uncovered in the mid-20th century, and they are still yielding clues about life and religious beliefs in ancient Israel. As VOA's Mike O'Sullivan reports, an exhibit in Los Angeles shows how modern science is bringing the history of these ancient documents to life.
Video

Video Angelina Jolie Takes Another Bold Step

Hollywood actress and filmmaker Angelina Jolie has revealed she had her ovaries and fallopian tubes removed to lower her odds of getting cancer. Doctors say the huge publicity over her decision will help raise awareness about the importance of cancer screening. VOA’s George Putic has more

All About America

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More