Microbial fuel cells (MFCs), generate electric energy by converting chemical energy from organic compounds through catalytic reactions by microorganisms. Microbial fuel cells (MFCs) are envisioned as one of the most promising alternative renewable energy sources because they can generate electric current continuously while treating waste. While these cells individually produce less than a volt (0.6V to 0.3V), their source of electricity is organic matter (waste food, fallen leaves, etc.) which makes them ideal for converting waste to electricity.
Scientists have developed a new skin patch, a flexible square just a couple of centimetres across that sticks to skin has used only sweat to power a radio for two days. “We’re now getting really impressive power levels,” Joseph Wang at the University of California-San Diego, who was on the team that worked on the technology, told the magazine. “If you were out for a run, you would be able to power a mobile device.” Wang and his colleagues used the lactate found in sweat to power their particular biofuel cell. The amount of lactate or lactic acid in sweat is also related to how efficiently a person’s muscles are working, so could help give readings on an athlete’s performance during exercise.
“The most exciting application is wearable sensors that can monitor health conditions, then sweat could generate enough power for a Bluetooth connection so that the results could be read straight from a smartphone,” says Mirella Di Lorenzo at the University of Bath, UK.
MFCs can be of aquatic microbial fuel cells (AMFCs) type that works in water environment and Terrestrial microbial fuel cells (TMFCs) can be inoculated and worked on land, which can overcome the disadvantages of AMFCs and extend the MFCs’ application range. One of the applications of MFC is to power a wireless environmental sensor network, however challenges of the low power density and low reliability prevents their widespread adoption.
Approximately all MFCs consist of anode and cathode chambers, physically separated by a proton exchange membrane (PEM). Active biocatalyst in the anode oxidizes the organic substrates and produces electrons and protons. The protons are conducted to the cathode chamber through the PEM, and the electrons are conveyed through the external circuit. Protons and electrons are reacted in the cathode chamber along with parallel reduction of oxygen to water.
low-cost, pee-powered fuel cell
In a new paper, a team of researchers at England’s University of Bath announced they developed a low-cost, pee-powered fuel cell capable of running electronic devices, including cell phones. Dr. Mirella Di Lorenzo, a lecturer in the university’s department of chemical engineering and an author of the study, said the ability to harness the power of human waste could revolutionize electricity generation.
The device is roughly the size of a U.S. quarter, costs between $1.50 and $3 to make, and “uses natural biological processes of ‘electric’ bacteria to turn organic matter, such as urine, into electricity,” according to a release. As urine passes through the fuel cell, it reacts with the bacteria, generating electricity that researchers say can either directly power an electronic device or be stored for later use.
“Microbial fuel cells can play an important role in addressing the triple challenge of finding solutions that support secure, affordable and environmentally sensitive energy, known as the ‘energy trilemma,’” Di Lorenzo said in a statement. “There is no single solution to this ‘energy trilemma’ apart from taking full advantage of available indigenous resources, which include urine. Researchers said a single cell is capable of generating 2 watts per cubic meter, enough to power a cell phone for an unspecified amount of time, but the power output could be significantly increased by stacking multiple cells together.
Researchers produce self-sustaining microbial fuel cells (MFCs)
Researchers at Binghamton University, State University of New York have developed the self-sustaining microbial fuel cells (MFCs) through symbiotic interactions of two types of bacteria which generated power for 13 straight days.
In a cell chamber about one-fifth the size of a teaspoon—90 microliters—researchers placed a mixed culture of phototrophic and heterotrophic bacteria. Phototrophic bacteria uses sunlight, carbon dioxide, and water to make its own energy, while heterotrophic bacteria must “feed” on provided organic matter or phototrophic bacteria to survive.
While the cell was exposed to sunlight, an initial dose of “food” was added to the chamber to stimulate growth of the heterotrophic bacteria. Through cellular respiration, the heterotrophic bacteria produced carbon dioxide waste, which was used by the phototrophic bacteria to kickstart the symbiotic cycle.
Those metabolic processes generated an electrical current—8 microamps per square centimeter of cell—for 13 straight days. The power was about 70 times greater than current produced by phototrophic bacteria alone. The small current generated means that these cells can be used to provide power in remote or dangerous locations for low-power items like health monitors and infrastructure diagnostic sensors.
“This concept of creating electricity through synergistic cooperation is not new. However, much of this work is still in its nascent stages,” said Binghamton University Electrical and Computer Science Assistant Professor Seokheun Choi. “Heterotrophic bacteria-based fuel cells generate higher power, while photosynthetic microbial fuel cells provide self-sustainability. This is the best of both worlds, thus far,
“There are some challenges of using this technique,” Choi said. “Balancing both microorganisms’ growth to maximize the device performance and the need to make sure that this closed system will permanently generate power without additional maintenance are two we have found. Long-term experiments are needed.”
The evolution of this technology will require additional exploration, but we, for the first time, realized this conceptual idea in a micro-scale device,” Choi said.
U.S. Army Tests Cambrian’s Advanced BioVolt™ system for off-grid applications
Cambrian Innovation announced a partnership with the U.S. Army to demonstrate BioVolt™, a self-powered wastewater treatment system. Leveraging newly-discovered, energy-generating biological processes, BioVolt treats wastewater with zero electrical input from the grid for aeration. The demonstrator test at the Carderock Division of the Naval Surface Warfare Center in Maryland is evaluating the system for application at forward operating bases (FOBs) and other off-grid locations.
BioVolt uses electrically-active microbes as catalysts in a fuel cell architecture to treat wastewater and generate electricity. The system is containerized, mobile, and can be easily scaled for expanded capacity with additional units.
“The largest shipments of supplies we send to the tactical edge in Afghanistan and Iraq are water and fuel,” said Lateefah Brooks, the contracting officer’s representative from the U.S. Army. “Advanced wastewater treatment solutions like BioVolt that not only clean water, but also produce energy to power the system, ensure resiliency in some of the harshest environments in the world.”
“Managing water and wastewater has traditionally been a very energy- and labor-intensive process. By producing electricity from wastewater and employing energy-efficient operations, BioVolt has the potential to decouple water and energy infrastructure, providing important strategic benefits for the Army,” said Matthew Silver, Founder and CEO of Cambrian Innovation. “We also foresee applications far beyond the military, including disaster relief and off-grid water treatment.”
Continuous Sustainable Power Supply: Benthic Microbial Fuel Cell
The Naval Research Laboratory (NRL) has developed the benthic microbial fuel cell (BMFC) as a persistent power supply for marine-deployed applications. The BMFC operates on the bottom of marine environments where it oxidizes organic matter residing in sediment with oxygen in overlying water. The NRL BMFC is a maintenance free, non-depleting power supply suitable for a wide range of sensors presently powered by batteries.
Unlike batteries however, the NRL BMFC will not deplete owing to constant supply of its fuel and oxidant by environmental processes and constant rejuvenation of its microbial electrode catalysts. For this reason, the NRL BMFC is an ideal power supply for when long duration uninterrupted sensor operation is a must, and for hard to access sensors and high-density sensor arrays where the cost of battery replacement is high.
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