Want electricity? Just add nano, gold, and sewage - Small Times
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Want electricity? Just add nano, gold, and sewage

July 22, 2010 - Researchers at Oregon State U. have come up with yet another unique application for nanocoatings -- help produce more electricity from sewage.

Their work, published a few weeks ago in Biosensors and Bioelectronics, focuses on the anodes of microbial electrochemical cells (MEC), the core of efforts to clean biowaste and produce useful levels of electricity, realizing twin goals of wastewater treatment and renewable energy. (OSU has been working on MECs for several years, hoping to develop systems for producing electricity from hydrogen fuel cells for automobiles.)

Bacteria from biowaste (i.e., sewage) is placed in an anode chamber, where they form a biofilm, consume nutrients, and grow, and that process releases electrons. Coating graphite anodes with a gold nanolayer increased the electricity production by 20×, they found; similar palladium coatings also produced an increase (50%-150%). They think iron nanoparticle coatings could produce similar electricity increases as gold -- and cost a lot less. And a similar approach could be applied to producing hydrogen gas instead of electricity, toward use in hydrogen fuel cells e.g. in cars.

From the paper abstract:

Significant positive linear regression was obtained between the current density and the particle size (average Feret's diameter and average area), while the circularity of the particles showed negative correlation with current densities. On the contrary, no significant correlation was evident between the current density and the particle density based on area fraction and particle counts. These results demonstrated that nano-decoration can greatly enhance the performance of microbial anodes, while the chemical composition, size and shape of the nanoparticles determined the extent of the enhancement.

More work is needed to get the process working beyond a lab environment, to lower its cost (e.g. identify the lowest-cost materials to use), and improve efficiency and electrical output even more. "We still need some improvements in design of the cathode chamber, and a better understanding of the interaction between different microbial species," added Frank Chaplen, an associate professor of biological and ecological engineering, in a statement. "But the new approach is clearly producing more electricity."

Ultimately, the researchers see the technology being used to reduce the cost of wastewater treatment, or in developing nations where wastewater treatment is impractical due to a lack of adequate power supply. Sewage treatment plants could be made to be completely self-sufficient in terms of energy usage, they say.

The research is supported by the Oregon Nanoscience and Microtechnologies Institute (ONAMI) and the National Science Foundation.


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