September 17, 2012
Producing power from wastewater
Construction Corner | Korky Koroluk
A new take on an old idea has produced a technology that is certain to interest cash-strapped municipal governments with a lot of wastewater to process.
Engineers at Oregon State University have devised a modern version of microbial fuel cells that can produce electricity directly from wastewater.
Their work opens the door to a future in which waste treatment plants will not only produce enough power to run themselves, but will also have surplus electricity to feed to the local grid.
The concept of using bacteria to generate electricity has been around for years and rudimentary microbial fuel cells have been built, but there wasn’t much urgency about developing the idea until recently, when generating clean electricity without burning fossil fuels became an urgent need in a warming world.
So now the folks at Oregon State just published details of their work.
Their microbial fuel cells (MFCs), could replace the widely used “activated sludge” process for treating sewage. Their process can clean wastewater, while producing significant amounts of electricity.
There’s an irony here, as there often is in the world of science: The more questions scientists find answers for, the more questions there are to ask.
Although it is known that bacteria can produce electricity in a fuel cell, the electrochemical process by which they do that is not well understood.
While theoreticians pursue that answer, applied scientists are proceeding with the practical development of the technology.
It is estimated that in most of the developed world, about three per cent of the electrical energy consumed is used to treat wastewater.
And, of course, most of that electricity is produced by burning fossil fuels that contribute to global warming. But, the biodegradable characteristics of wastewater could, in theory, provide many times the energy that is now being used to process them, with no additional greenhouse gas emissions.
The Oregon team has proven its concept at a substantial scale in the laboratory, but they know there is a big difference between making something work in the lab and making it work just as well in the field.
“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,” said Hong Liu, a professor of biological and ecological engineering.
“This could have an impact around the world, save a great deal of money, provide better water treatment and promote energy sustainability.”
The next step will be a pilot project, for which funding is being sought.
A good candidate for the pilot, Liu said, might be a food processing plant, because it is a closed system with a predictable amount of waste.
And, while the pilot is going on, she said, more work will be done into ways to achieve the best use of the necessary microbes that give MFCs its name.
Even without that continuing work, the Oregon system seems to work better and produces more power than any previous MFCs.
So far, it isn’t possible to know how much an MFC treatment plant might cost, although researchers suggest it might be comparable to that of the activated sludge systems that are now so widespread.
But, the cost would be less when future sales of excess electricity are factored in.
That’s why the system should be of interest to municipalities.
We could well be coming to a time when wastewater treatment is done at a number of small plants spotted here and there in urban areas.
This would remove the need for a lot of large-diameter pipe and pumping stations.
Each of these small plants would also be a small power plant feeding power into the local grid—and cash into the municipal revenue stream.
Korky Koroluk is a regular freelance contributor to the Journal of Commerce. Send comments or questions to firstname.lastname@example.org.
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