Microbe power as a green means to hydrogen production

Jun 01, 2010
Dr. Prathap Parameswaran showing the electrode used in the microbial electrochemical cell (MEC). When the bacteria are grown in an oxygen-free, or anaerobic environment, they attach to the MXC's anode, forming a sticky matrix of sugar and protein. This living matrix, known as the biofilm anode, is a strong conductor. Credit: The Biodesign Institute at Arizona State University

Scientists have been hard at work harnessing the power of microbes as an attractive source of clean energy. Now, Biodesign Institute at Arizona State University researcher Dr. Prathap Parameswaran and his colleagues have investigated a means for enhancing the efficiency of clean energy production by using specialized bacteria.

Microbial electrochemical cells or MXCs are able to use bacterial respiration as a means of liberating electrons, which can be used to generate current and make clean electricity. With minor reconfiguring such devices can also carry out electrolysis, providing a green path to production, reducing reliance on natural gas and other fossil fuels, now used for most hydrogen manufacture.

Dr. Prathap Parameswaran showing the electrode used in the microbial (MEC).

MXCs resemble a battery, with a Mason jar-sized chamber setup for each terminal. The bacteria are grown in the "positive" chamber (called the ). The research team, led by Bruce Rittmann, director of Biodesign's Center for Environmental Biotechnology, had previously shown that the bacteria are able to live and thrive on the anode electrode, and can use waste materials as food, (the bacteria's dietary staples include pig manure or other farm waste) to grow while transferring electrons onto the electrode to make electricity.

In a microbial electrolysis cell (MEC), like that used in the current study, the electrons produced at the anode join positiviely charged protons in the negative (cathode) chamber to form . "The reactions that happen at the MEC anode are the same as for a which is used to generate electricity, " Parameswaran says. "The final output is different depending on how we operate it."

When the bacteria are grown in an oxygen-free, or anaerobic environment, they attach to the MXC's anode, forming a sticky matrix of sugar and protein. In such environments, when fed with , an efficient partnership of bacteria gets established in the biofilm anode, consisting of fermenters, hydrogen scavengers, and anode respiring bacteria (ARB). This living matrix, known as the biofilm anode, is a strong conductor, able to efficiently transfer electrons to the anode where they follow a current gradient across to the cathode side.

The present study demonstrates that the level of electron flow from the anode to the cathode can be improved by selecting for additional bacteria known as homo-acetogens, in the anode chamber. Homo-acetogens capture the electrons from hydrogen in waste material, producing acetate, which is a very favorable electron donor for the anode bacteria.

Microbial electrochemical cells or MXCs are able to use bacterial respiration as a means of liberating electrons, which can be used to generate current and make clean electricity. MXCs resemble a battery, with a Mason jar-sized chamber setup for each terminal. The bacteria are grown in the "positive" chamber (called the anode). Credit: The Biodesign Institute at Arizona State University

The study shows that under favorable conditions, the anode bacteria could convert hydrogen to current more efficiently after forming a mutual relationship or syntrophy with homo-acetogens. The team was also able to reduce the negative impact of other hydogen consuming microbes, such as methane-producing methanogens, which otherwise steal some of the available electrons in the system, thereby reducing current. The selective inhibition of methanogens was accomplished by the adding a chemical called 2-bromoethane sulfonic acid to the adode's microbial stew.

The group used both chemical and genomic methods to confirm the identify of homo-acetogens. In addition to detection of acetate, formate, an intermediary product, was also discovered. With the aid of quantitative PCR analysis, the team was also able to pick up the genomic signature of acetogens in the form of FTHFS, a gene specifically associated with acetogenesis.

"We were able to establish that these homo-acetogens can prevail and form relationships," Parameswaran says. Future research will explore ways to sustain syntrophic relations between homo-acetogens and anode , in the absence of the chemical inhibitors.

Further progress could pave the way for eventual large-scale commercialization of systems to simultaneously treat wastewater and generate clean . "One of the biggest limitations right now is our lack of knowledge," says Cesar Torres, one of the current study's co-authors, who stresses that there remains much to understand about the interactions of bacterial communities within MXCs.

The field is still very young, Torres points out, noting that work on MXCs only began about 8 years ago. "I think over the next 5-10 years the community will bring a lot of information that will be really helpful and that will lead us to good applications."

Explore further: Water-based nuclear battery can be used to generate electrical energy

More information: The team's results appear in the advanced online issue of the journal Bioresource Technology.

Related Stories

Study: cow-powered fuel cells grow smaller, mightier

Aug 21, 2007

Cows could one day help to meet the rise in demand for alternative energy sources, say Ohio State University researchers that used microbe-rich fluid from a cow to generate electricity in a small fuel cell.

Microbial fuel cells turn on the juice

Dec 05, 2007

The combination of beer, wastewater, microbes, fuel cells, high school students and teachers sounds like a witches’ brew for an old –fashioned, illicit ‘60s beach party.

Microbes turn electricity directly to methane

Mar 30, 2009

(PhysOrg.com) -- A tiny microbe can take electricity and directly convert carbon dioxide and water to methane, producing a portable energy source with a potentially neutral carbon footprint, according to a ...

Progress Toward a Biological Fuel Cell?

Dec 30, 2008

(PhysOrg.com) -- Biological fuel cells use enzymes or whole microorganisms as biocatalysts for the direct conversion of chemical energy to electrical energy. One type of microbial fuel cell uses anodes (positive electrodes) ...

Making more efficient fuel cells

Sep 07, 2009

Bacteria that generate significant amounts of electricity could be used in microbial fuel cells to provide power in remote environments or to convert waste to electricity. Professor Derek Lovley from the University of Massachusetts, ...

Renewable hydrogen production becomes reality at winery

Sep 29, 2009

(PhysOrg.com) -- The first demonstration of a renewable method for hydrogen production from wastewater using a microbial electrolysis system is underway at the Napa Wine Company in Oakville. The refrigerator-sized hydrogen ...

Recommended for you

Future of energy storage

6 hours ago

MIT professor Fikile Brushett is in the process of taking the power generated by wind and solar, chemically lashing it to molecules derived from flora and fauna, and storing it in liquids until it's needed ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Quantum_Conundrum
not rated yet Jun 01, 2010
Gave it five stars.

The idea of having a bacterial shit reactor to power our homes and businesses is just too funny.

FBM will hate this one, as it allows recycling of human waste, greatly removing limits on population growth, while simultaneously providing power for said population.

Go microbes.