Bacteria--Energy Producers of the Future?
All of us use water and in the process, a lot of it goes to waste. Whether it goes down drains, sewers or toilets, much of it ends up at a wastewater treatment plant where it undergoes rigorous cleaning before it flows back to the environment. The process takes time, money and a lot of energy.
What if that wastewater could be turned into energy? It almost sounds too good to be true, but environmental engineer Bruce Logan is working on ways to make it happen.
"Right now, we use 5 percent of our electricity to run our water infrastructure," says Logan. "We can literally pour wastewater into this fuel cell and take the energy in the wastewater and make electricity. We're using bacteria to actually turn any organic matter and some inorganic matter directly into electricity. The bacteria do it themselves. That's how we're running this fan," he says with a smile and points to a small spinning fan attached to a fuel cell.
Most treatment plants already use bacteria to break down the organic waste in the water. With support from the National Science Foundation (NSF), Logan and his team at Penn State University are taking the idea a step further. They are developing microbial fuel cells to channel the bacteria's hard work into energy. Here's how it works: The bacteria in the wastewater eat the organic waste, releasing electrons as a byproduct. Those electrons collect on carbon bristles in the fuel cell, eventually flowing through a circuit that can power a small fan or light bulb.
"We can make all sorts of different kinds of energy," Logan explains. "Typically, a microbial fuel cell produces electrical power or current, but if we add a little bit of voltage into the system, we can evolve hydrogen gas, which is really nice, because that's a very environmentally friendly energy carrier. You can run cars on it; you can use it in many, many industries. And, we can link these reactors together in order to multiply the power that's produced by each of these and to capture the power."
Logan says these wastewater batteries will be useful if they can generate enough energy to be cost effective. "In the early reactors, we used very expensive graphite rods and expensive polymers and precious metals like platinum. And we've now reached the point where we don't have to use any precious metals."
The latest versions are already using cheaper more environmentally friendly materials. Logan is also testing another system that would use salt water in the fuel cell to generate even more electricity. "You're actually creating energy and desalinating the water and treating the wastewater. It's a triple play," he notes.
Logan expects in the next five to 10 years microbial fuel cells will be ready for use in the real world. The goal is to use them to generate enough electricity to power a wastewater treatment plant with energy left over to share with the nearby community. Now that's a powerful idea.
Miles O'Brien, Science Nation Correspondent
These SELECTED VIDEOS explore and briefly explain microbial fuel cells.
Microbial Fuel Cell has10 times more Power
Biological engineers at Oregon State University have designed a microbial fuel cell that is capable of generating about 10 times more electricity than previously possible from an air cathode microbial fuel cell of the same size.
This design breakthrough could allow microbial fuel cells to be used more widely as sources of sustainable energy, said Hong Liu, an assistant professor in the OSU Department of Biological and Ecological Engineering.
The new design could ultimately lead to portable systems for power generation that are simultaneously capable of providing reusable water for developing nations and remote areas. The fuel cell design could also significantly reduce the amount of electricity used at large wastewater treatment facilities.
“We have successfully modified the fuel cell structure to enhance power generation,” said Liu, who co-authored the article with fellow OSU professor Yanzhen Fan and OSU graduate student Hongqiang Hu.
Microbial fuel cells, also known as biological fuel cells, use bacteria to convert biodegradable materials such as wastewater pollutants into electricity. As the bacteria consume the pollutants, they shed electrons, which flow through a circuit and generate electricity. In the process, pollutants are broken down, resulting in clean water.
Microbial fuel cells, especially those with air cathodes, hold great promise for many practical applications, due to their simple configuration and renewable and abundant fuel sources. However, the power outputs have historically been so low the devices have not been considered as viable sources of electricity.
The new design developed by the OSU researchers involves sandwiching a cloth layer between the anode and the cathode parts of the microbial fuel cell, a configuration that greatly reduces the internal resistance, resulting in a much higher power density, Liu says.
In lab experiments, Liu’s team successfully generated 1,010 watts per cubic meter of reactor, or enough to power 16 60-watt light bulbs. The highest previous level of sustainable electricity generated from a cubic meter of air cathode microbial fuel cell is less than 115 watts. In experiments done even more recently, Liu and colleagues have generated more than 1,500 watts from the same reactor volume.
The design improvements could eventually lead to a dramatic reduction in the cost of operating wastewater treatment plants in the United States and elsewhere.
Five percent of the electricity in the U.S. is used for water and wastewater treatment, mainly to power pumps and other equipment. “By incorporating microbial fuel cells in water treatment facilities, the cost of operation could be reduced,” Liu says.
Although scaling up microbial fuel cells to help power large wastewater facilities is a long-term goal of Liu’s, she says small scale systems will be feasible sooner. “It would be useful to build a smaller system for individual households. This is something the world can use very soon, especially in countries like China and India.”
While microbial fuel cells can't solve all global environmental and energy problems, they can help, Liu says.
As I watched this exciting video on Solar bag, it inspires me how we can help our emerging markets India, Philippines and other poorer countries solve their access to drinking water. I see the usefulness of the research product being used by NGO's, aid agencies to provide clean water. OSU continues to experiment and test newer ideas on cleaner water processes.
“Our research results are very promising. There is a real future here, and I hope we can make a small contribution to the world.”
Liu’s research is supported in part by a $200,000 grant from the U.S. Department of Transportation through the Sun Grant Initiative, the OSU General Research Fund and the OSU Agricultural Research Foundation.