Optimizing the Microbial Fuel Cell as an Alternative Fossil Fuel Source

Philip Ong, Alex Cheah, Daniel ChewAnglo-Chinese School (Independent), Singapore

INTERNATIONAL STUDENT SCIENCECONFERENCE2-8 July 2012

Hong Kong

Introduction – The Microbial Fuel Cell

•A bio-electrochemical system that uses bacteria to produce electricity

•Converts chemical energy to electrical energy by catalytic reaction of microorganisms

•Used to generate electricity for storage

Our Aims•C

urbing carbon emissions by offering a cheap, efficient method of obtaining energy

•To conserve fossil fuels and oil

•To reduce the emissions of environmentally-unfriendly substances into the earth

Our Set-Up•O

ur experiment involved the use of a soil-based Microbial Fuel Cell (MFC) through the construction of a Winogradsky Column.

•Variables:• [Independent]: Salinity as controlled by the amount of NaCl per set-up • [Dependent]: Current (in miliamperes)• [Controlled]: Temperature, Location, Container Size & Shape, Type of electrode, Amount of soil.

Materials and Apparatus•M

aterials:•1

. Clay soil used: 50% clay [Al2Si2O5(OH)4] 50% soil [SiO2]• (400g per set-up)

•2. Sulfur• (50g per set-up)

•3. Water

•4. Newspaper Shreds • (10g per set-up)

•5. NaCl

•Apparatus:

•1. 2 Graphite Electrodes per set-up (as the anode and cathodes)

•2. 2 Crocodile Clips

•3. Multimeter

•4. Stopwatch

•5. Plastic containers

Conversions

Added amount of salt / g

Added salt concentration / ppm

0 05 232010 463015 692820 9217

Analysis

•Increase ionic strength Decrease resistance• I = 1.6 x 10-5 x Specific Conductance (in µmho/cm)• I = ½ Σ zi

2 mi

•Provide nutrients

•Tonicity: Too much salt causes crenation

•Lower oxygen levels

Limitations•C

arbon surfaces not pure

•Denitrification of nitrogen containing functionalities

•Pt electrodes might oxidize separate substrates

•Electroactive chemicals naturally present

•Contaminants easily absorbed

Conclusion•O

ptimal range: 4000ppm-7000ppm

•Good current output

•Renewable energy source

•Easily accessible

Further Research•D

ifferent genera involved•O

ptimal soil for involvement in MFC•U

sing other substitutes for soil eg. Wastewater•R

esearch into MFCs as a method of reducing toxicity of soil•Use of Sulfate Reducing Bacteria•Polysulfides to sulfur

•Electrochemically active bacteria

References•N

ewton. Oxygen Levels in Salt and Fresh Water. http://www.newton.dep.anl.gov/askasci/chem03/chem03339.htm

•U.S. Geological Survey. Saline water. http://ga.water.usgs.gov/edu/saline.html

•CaCt. Chemical Reactivity: A Study Guide. http://www.science.uwaterloo.ca/~cchieh/cact/applychem/reactivity.html

•University of Massachusetts: College of Engineering. Chapter XVIII: Electrochemical methods. http://www.ecs.umass.edu/cee/reckhow/courses/572/572bk18/572BK18.html

•Glass Properties. Definitions: Resistance, Specific resistance (resistivity), Conductance, Specific conductance (conductivity). http://glassproperties.com/resistivity/Conductivity_Resistivity.pdf

•Xi Wang et al., Impact of salinity on cathode catalyst performance in microbial fuel cells (MFCs). International Journal of Hydrogen Energy [online] 2011, 36, 13900-13906 http://www.engr.psu.edu/ce/enve/logan/publications/2011-Wang-etal-IJHE.pdf

•Korneel Rabaey et al., Microbial Fuel Cells for Sulfide Removal. Environ. Sci. Technol. [online] 2006, 40, 5218-5224 http://www.microbialfuelcell.org/Publications/LabMET/Rabaey%20Environ%20Sci%20Techn%2040%205218-5224%20Sulfide%20removal.pdf