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

Turkey: No Ransom Paid for Release of Hostages Held by IS Militants

President Erdogan hails release of hostages as diplomatic success but declines to be drawn on whether their release freed Ankara's hand to take more active stance against insurgents More

Audio Sierra Leone Official Pleased With Ebola Containment Measure

Official says three-day sensitization effort will help reduce infection rate of Ebola disease nationwide More

US Pivot to Asia Demands Delicate Balancing Act

As the tumult in the Middle East distracts Obama, shifting American focus eastward appears threatened 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.
Fears Ebola Outbreak ‘Beyond Our Capability to Contain’i
X
Jeff Seldin
September 20, 2014 10:28 PM
Each day brings with it new warnings about the deadly Ebola outbreak already blamed for killing more than 2,600 people across West Africa. And while countries and international organizations like the United Nations are starting to come through on promises of help for those most affected, the unprecedented speed with which the virus has spread is raising questions about the international response. VOA's Jeff Seldin has more from Washington.
Video

Video Fears Ebola Outbreak ‘Beyond Our Capability to Contain’

Each day brings with it new warnings about the deadly Ebola outbreak already blamed for killing more than 2,600 people across West Africa. And while countries and international organizations like the United Nations are starting to come through on promises of help for those most affected, the unprecedented speed with which the virus has spread is raising questions about the international response. VOA's Jeff Seldin has more from Washington.
Video

Video Iran, World Powers Seek Progress in Nuclear Talks

Iran and the five permanent members of the U.N. Security Council plus Germany, known as the P5 + 1, have started a new round of talks on Iran's nuclear program. VOA State Department correspondent Pam Dockins reports that as the negotiations take place in New York, a U.S. envoy is questioning Iran's commitment to peaceful nuclear activity.
Video

Video Obama Goes to UN With Islamic State, Ebola on Agenda

President Obama goes to the United Nations General Assembly to rally nations to support a coalition against Islamic State militants in Iraq and Syria. He also will look for nations to back his plan to fight the Ebola virus in West Africa. As VOA White House correspondent Luis Ramirez reports, Obama’s efforts reflect new moves by the U.S. administration to take a leading role in addressing world crises.
Video

Video Migrants Caught in No-Man's Land Called Calais

The deaths of hundreds of migrants in the Mediterranean this week has only recast the spotlight on the perils of reaching Europe. And for those forunate enough to reach a place like Calais, France, only find that their problems aren't over. Lisa Bryant has the story.
Video

Video Westgate Siege Anniversary Brings Back Painful Memories

One year after it happened, the survivors of the terror attack on Nairobi's Westgate Shopping Mall still cannot shake the images of that tragic incident. For VOA, Mohammed Yusuf tells the story of victims still waiting for the answer to the question 'how could this happen?'
Video

Video Militant Assault in Syria Displaces Thousands of Kurds

A major assault by Islamic State militants on Kurds in Syria has sent a wave of new refugees to the Turkish border, where they were stopped by Turkish border security. Turkey is already hosting about 700,000 Syrian refugees who fled the civil war between the government and the opposition. But the government in Ankara has a history of strained relations with Turkey's Kurdish minority. Zlatica Hoke reports Turkey is asking for international help.
Video

Video Whaling Summit Votes to Uphold Ban on Japan Whale Hunt

The International Whaling Commission, meeting in Slovenia, has voted to uphold a court ruling banning Japan from hunting whales in the Antarctic Ocean. Conservationists hailed the ruling as a victory, but Tokyo says it will submit revised plans for a whale hunt in 2015. Henry Ridgwell reports from London.
Video

Video A Dinosaur Fit for Land and Water

Residents and tourists in Washington D.C. can now examine a life-size replica of an unusual dinosaur that lived almost a hundred million years ago in northern Africa. Scientists say studying the behemoth named Spinosaurus helps them better understand how some prehistoric animals adapted to life on land and in water. The Spinosaurus replica is on display at the National Geographic museum. VOA’s George Putic has more.
Video

Video Iraqi Kurdistan Church Helps Christian Children Cope find shelter in churches in the Kurdish capital, Irbil

In the past six weeks, tens of thousands of Iraqi Christians have been forced to flee their homes by Islamic State militants and find shelter in churches in the Kurdish capital, Irbil. Despite U.S. airstrikes in the region, the prospect of people returning home is still very low and concerns are starting to grow over the impact this is having on the displaced youth. Sebastian Meyer reports from Irbil on how one church is coping.


Carnage and mayhem are part of daily life in northern Nigeria, the result of a terror campaign by the Islamist group Boko Haram. Fears are growing that Nigeria’s government may not know how to counter it, and may be making things worse. More

AppleAndroid