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TG Daily
By Humphrey Cheung
Pittsburgh (PA) - Penn State University researcher Bruce Logan and his team have developed a unique method of harnessing hydrogen gas. By creating a type of controlled microbial soup out of materials straight from a salad bar, a bacteria-induced chemical reaction takes place, ultimately resulting in large quantities of hydrogen gas. But just how much hydrogen is produced? The numbers dwarf other methods of producing hydrogen making this a very promising solution.
Researchers have designed a microbial electrolysis cell in which bacteria break up acetic acid (a product of plant waste fermentation) to produce hydrogen gas with a very small electrical input from an outside source. Hydrogen can then be used for fuel cells or as a fuel additive in vehicles that now run on natural gas. Credit: Zina Deretsky, National Science Foundation.
The team began working with various mixtures for the soup. Over time they discovered that by changing the temperature, altering the ratio of water to the source materials, even adding a small amount of electricity, they were able to achieve efficiencies in excess of 90%. Using straight vinegar, for example, a 91% efficiency was achieved. Other materials provide 68% efficiency for raw, un-pretreated cellulose, 82% for lactic acid and acetic acid--both byproducts from normal fermentation. Glucose lags furthest behind, being only 64% efficient.
How does it work? Tiny bacteria sit in the soup along with a granulated graphite anode, a carbon with platinum cathode, and an off-the-shelf anion exchange membrane. The bacteria consume the soup material, such as acetic acid. In the process they release electrons and protons, even generating up to 0.3 volts. When an additional 0.2 volts are applied from an external source, hydrogen gas bubbles begin to form. These eventually collect and bubble up to the surface where they're pumped off and captured in a storage vessle.
Powerful return from input energy
The process produces 288% more energy than the electricity required to extract it. Compared to water hydrolysis, for example, which is only 50% to 70% efficient making it require more input energy than the extracted hydrogen yields, this process is far more desirable. It can be shown that even using enough of the harnessed energy to sustain the reaction, 144% more energy is produced. This makes the microbial soup solution a real application for energy generation.
Clean energy
Best of all, it's clean energy. When hydrogen is burned, the waste exhaust is comprised only of water vapor and heat. No greenhouse gases are produced at all. And any vehicle which can run on natural gas today can be converted to run on hydrogen. The issues of high pressure hydrogen storage, and the large amount of overnight loss, still remain however.
Farm benefits
The researchers indicate another possible use for these kinds of microbial cells is for manufacturing fertilizer. Instead of using current methods, which involve trucking in fertilizer made in factories, very large farms could begin using microbial cells. They would take wood chips processed through a common practice used today, along with nitrogen from the air, to produce ammonia or nitric acid. These can both be used as sources of fertilizer, or as feed material to make ammonium nitrate, sulfate or phosphate.
The research team has filed a patent for their discovery. Their work was funded by the National Science Foundation, as well as Air Products and Chemicals, Inc.