Wednesday, 15 August 2012 12:36
August 15, 2012
Nobody likes to think about what happens to wastewater once its gone down the drain, and it's not often that sewers capture the imagination of researchers. But a new technology being developed by Oregon State University could turn sewage treatment plants from a major drain on the country's electrical grid to a fairly significant source of energy themselves.
Power from waste
The primary concern with sewage is to ensure that the water is properly treated, with contaminants removed thoroughly enough that the water can either be recycled or released back into local waterways.
But wastewater also contains large amounts of organic material, the essential basis for fossil fuels and a convenient store of usable energy.
Many wastewater treatment plants already make use of some of this energy through a process known as anaerobic digestion, which uses bacteria to break down organic compounds into, at least partly, methane gas. This gas can then be burned as a fuel or, at the very least, flared to limit its impact as a greenhouse gas.
However, engineering research at OSU led by Hong Liu, an associate professor in the Department of Biological and Ecological Engineering, has led to the development of a technology that would instead use this wastewater as the power source in a microbial fuel cell.
Fuel without fire
Fuel cells function by causing the oxidation of a substance within an electrolyte, but forcing electrons to flow from an anode to a cathode, producing a current. Liu's team developed a strain of bacteria that would oxidize the organic material in the wastewater directly, producing significantly more power than traditional approaches. It also manages to avoid the harmful emissions that are a common consequence of these technologies.
Perhaps more importantly, current models of this system have been able to produce electricity at a rate of between 10 and 50 times that of other microbial fuel cells, and have managed to do so at a cost comparable to currently marketed systems.
"If this technology works on a commercial scale the way we believe it will, the treatment of wastewater could be a huge energy producer, not a huge energy cost," Liu said in a statement. "This could have an impact around the world, save a great deal of money, provide better water treatment and promote energy sustainability."
The group is now looking for funding to develop a test plant to prove the viability of the concept in the field.
Global impact for cleaner water
As it stands, OSU says that the U.S. uses around 3 percent of all its electricity simply to power wastewater plants, receiving far less than that in return from the various digesters and early fuel cells.
The addition of systems as efficient as Liu's fuel cell could mean transforming the thousands of municipal waste treatment plants into small scale power plants, or at least less of a drain on energy resources.
However, Scientific American notes that the bigger impact could be seen abroad, especially in the developing world where many more people do not have sufficient access to the clean water, often because of a lack of reliable power.
The United Nations Statistics Division reports that as recently as 2009 some countries had no access at all to wastewater treatment and even developed countries like Poland (62 percent) and Greece (87 percent) fall well short of full access.
The ability to power treatment equipment internally and the potential to sell electricity to surrounding communities could make these plants a more palatable investment in coming years.
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