CBET Award Achievements
Notable Accomplishments from CBET Awards
 

Bacteria Producing Power

Bruce Logan, Pennsylvania State University

Background:  With no intermediate, electricity can be generated using bacteria in newly developed devices called microbial fuel cells (MFCs).  While MFCs have properties in common with hydrogen fuel cells, there are important differences that are just being discovered in efforts to increase power generation and current recovery.

All hydrogen fuel cells have proton exchange membranes that facilitate proton transfer from the gas being oxidized (hydrogen) to the gas being reduced (oxygen).  In MFCs, however, these membranes are not necessarily needed as water serves as the proton exchange medium.  However, the membranes are useful to keep the solution from contaminating the cathode and to reduce oxygen carry over into the chamber containing the bacteria.  The Logan Group at Penn State University hypothesized that using an anion exchange membrane would work since anions can carry protons in solution.

The Logan Group also studied the conductivities of electrode materials.  The conductivities are high, and bacteria evolved to use metal oxides, which are positively charged surfaces.  The Group hypothesized that increasing the positive charge of the carbon surface could increase bacterial adhesion and facilitate electron transfer to a surface.

Results:  The Logan Group compared power generation using an anion exchange membrane with effect of different types of membranes, including ultrafiltration membranes and different cation (proton) exchange membranes.  The Group found the anion exchange membrane resulted in the highest power density of the different membranes.

The Logan Group also compared power generation using a plain carbon electrode with that of an ammonia-gas treated electrode that resulted in a higher positive charged surface.  The Group found the treated electrode increased power to 1970 mW/m2 of anode surface area, or 114 W/m3 of reactor volume.

Bruce Logan Image 1
 
This Microbial Fuel Cell (MFC) has two chambers and was
used by the Logan Group to conduct membrane testing.

Bruce Logan Image 2
 
Dr. Logan holds a series of MFC reactors.

Bruce Logan Image 3
 
A typical Microbial Fuel Cell (MFC).
Credit, all images:  Bruce Logan, Pennsylvania State University


Scientific Uniqueness:  This research is the first instance an anion has been shown to conduct charge in an MFC and to increase power compared to conventional proton exchange membranes.  In the conductivity studies, the power densities normalized to surface area (or volume) are the highest yet achieved for air-cathode MFCs.

Impact on Industry and/or Society:  This advance brings MFCs a step closer to practical implementation as a form of wastewater treatment and energy generation.

Potential Economic Impact: This technology could be successfully marketed for wastewater treatment and provide an alternate source for energy generation.

This work is notable because it has not previously been shown that anions could be used for charge transfer in an MFC.  Also, these reactors can be easily inoculated using bacteria naturally occurring in the environment, and power generation is the highest yet produced in these types of systems.

This work is multidisciplinary. This work melds numerous fields of science and engineering, including chemical engineering and molecular biology.  While combining these fields, this new research provides a multidisciplinary environment for the education of young scientists and engineers.

This project addresses the NSF Strategic Goal of Discovery. This discovery will impact efficiency and sustainability of MFCs furthering their development.  The membrane will be useful in wastewater treatment applications.

This Nugget represents transformative research.  Exploratory in nature, this new approach could lead to further developments improving energy generation and wastewater treatment.



     
Program Officer:   Cindy Lee
     
NSF Award Numbers:   0401885
     
Award Title:   Improving Power Generation in Microbial Fuel Cells
     
PI Name:   Bruce Logan
     
Institution Names:   The Pennsylvania State University-University Park
     
Program Element:   1440   Also posted as a Nugget under Program Elements 7643 and 7644.
     

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This Nugget was Updated on 15 December 2008.