A new microbial fuel cell creates energy during wastewater treatment and also vastly reduces the amount of sludge produced. Israel-based company, Emefcy, named as a play on the acronym for microbial fuel cell (MFC), starts with the same principle as most wastewater treatment—water is aerated so bacteria in the liquid break down organic material in a closed series of containers known as a bioreactor.

"We didn't invent anything scientifically new," says Ely Cohen, vice president of marketing and business development for the four-year-old company.

The novelty factor: instead of using electricity to push air into the water, Emefcy uses a permeable filter that allows air in but doesn't let liquid out, much like how a diaper works. The polyethylene plastic membrane, similar to materials used in construction, surrounds the fuel cell chamber into which wastewater flows.

Inside the fuel cell, Emefcy coaxes anaerobic bacteria, primarily Shewanella oneidensis and Geobacter sulfurreducens, to release electrons in an oxygen-free environment. The electrons flow to an anode and then into a circuit to cathodes in a separate chamber on the outside of the membrane. The electrons allow the carbon cathodes to react with oxygen to form carbon dioxide.

The practical side of the Emefcy fuel cell relates to the materials engineering: both the anode and cathode are made of a carbon cloth that acts as a conductor. Precious metals have long been used as conducting materials in batteries and other types of fuel cells but are too expensive to use at a commercial scale in microbial fuel cells.

For a typical paper-recycling factory, one Emefcy fuel cell module, which is about the size of a cubic meter, could treat about three cubic meters per day of wastewater depending on the amount of organic material present, according to Cohen, and the modules can be scaled to meet the needs of larger or smaller plants.

The bacteria eat a lot to produce electricity and live a longer life because the environment is optimized for their survival, so sludge can be cut down by 80 percent, Cohen says. Roughly four watts of electricity are produced for every kilogram of organic material that the bacteria consume. The amount of electricity generated will not exactly power the entire town, or even the entire processing facility, but it can offset the energy used to clean the water.

"The energy we don't consume is more important than the electricity we might produce," says environmental engineer Bruce Logan of Pennsylvania State University, an Emefcy advisor.

Municipal and industrial wastewater plants comprise about 2 percent of the annual electrical power used in the U.S., but treatment methods have remained largely unchanged for decades. In traditional systems, most of the power goes into pumping air through the water so that bacteria in the water can grow and consume organic material that remains after the largest particles have been removed. Another substantial chunk of energy goes into trucking away the leftover sludge, which almost always ends up in landfills.

Emefcy's technology has its limitations. The fuel cell is ideal for wastewater that is high in organic material, mostly wastewater from agriculture and food processing rather than municipalities. Logan estimates that quantities of food and beverage wastewater equal domestic wastewater, and animal and farm wastewater is more than the other two markets combined. Cohen said that the food additives industry, in particular, may become a very attractive market for the technology.

Sludge reduction and regulatory compliance are also significant drivers for the food and beverage industry, which is pushing more companies to process wastewater on site rather than just sending it directly to municipal treatment facilities, according to a report from Global Water Intelligence (GWI), a water industry market research firm based in England. With increasing regulation, Emefcy's technology could become appealing for this market as well.

9 Comments

1. 1. Wayne Williamson 06:37 PM 7/17/12

   Sounds interesting, but looks like its in its infancy. I hope the Israel demonstration pans out. I just have to wonder about a cubic meter to process 3 cubic meters per module per day. A cubic meter has approx 264 gallons or a module could process about 800 gallons a day. If you needed to process 100m gallons a day then you would need 125k of these modules and they don't even work on normal waste water according to the article...

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2. 2. Greg Angelo 05:19 PM 7/19/12

   According to my reference, source one watt is the rate at which work is done when one ampere (A) of current flows through an electrical potential difference of one volt (V). Equating 4 watts which I understand to be a rate of electricity being produced with a kilogram of mass of waste appears to be an erroneous use of the term. It would appear to me as a non-scientist that a kilogram of waste should be equated to a rate of watts for a period, possibly a watt-hour.

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3. 3. Joseph C Moore, Cpo USN Ret 08:12 PM 7/19/12

   So the process produces carbon dioxide which is now classified as an environmental hazard (even though each exhale of our breath is carbon dioxide). Will this technology be prohibited in progressive states (countries)?

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4. 4. kenwa2010 09:48 PM 7/19/12

   As accorded Wikipedia, in 2015AD the world will deplete its petroleum crude oil below consumption levels. We need every scientist to look at their general and specific studies and see how to make energy from things that explode and buildups of electrons, for example. How could your study make energy?
   

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5. 5. denicepetit21 10:54 AM 7/20/12

   I find this very interesting to rethink of a way to reduce the sludge by 80%. That's impressive in my book we do need to reduce the waste into the environment. Let's work together on improvement for all humans living on the earth. The energy produced is secondary to the whole problem of waste. Reinvent the old process is what is being done here not electricity. Blessing to You Israel !!!

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6. 6. DaniEder in reply to Joseph C Moore, Cpo USN Ret 11:54 AM 7/20/12

   Much of sewage sludge originates with food, from kitchen sinks and toilets, which absorbed CO2 when it was grown, so it is net neutral. Bacteria have been breaking down biological wastes since forever. Treatment plants just do it in a concentrated location resulting from the concentration of humans in cities. Using cleaned up sludge as fertilizer completes the cycle for the next round of food growth.
   
   What would help is if people didn't put things down the drain that contaminate the sewage. One way to do that is separated "grey" and "black" water systems. Black is for organic wastes and grey is for clothes washing and utility sinks, where chemicals end up in the water. A few homes have dual systems, but I am not aware of any cities that do that on a large scale.

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7. 7. stan e m 03:04 PM 7/20/12

   We wouldn't need sewage treatment if we used composting toilets and wetlands to clean water.Old style washmachines should be banned.most of the laundry can be cleaned by hanging the clothes on a clothsline;dry.The sun will freshen and kill bugs.

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8. 8. bucketofsquid in reply to stan e m 02:21 PM 7/26/12

   @stan e m - You must have no sense of smell. What do you do in bad weather (aside from smelling bad)?

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9. 9. bucketofsquid in reply to kenwa2010 02:29 PM 7/26/12

   @kenwa2010 - I just looked this up on Wikipedia and they give a range from 2009 to 2020 with the major caveat that alternate energy sources delay the point an unknown amount. In other words you are over simplifying.

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