This webpage aims to help someone to build a microbial fuel cell (MFC) using relatively inexpensive and readily available materials. The method is based on the microbial fuel cells built by Abbie Groff, a student at Conestoga Valley High School in Lancaster, PA. The research she performed with her MFCs helped her win the Grand Champion Award at the 2005 Lancaster County Science Fair. More information about her research can be found on her website.

This website is intended to be a rough guide to constructing a MFC, not an exact step-by-step procedure.

Materials

Unless otherwise noted, all materials should be available at local stores.

Two heavy duty plastic bottles with sealable lids
Short section of plastic pipe (polyethylene or PVC) for salt bridge
Means to connect pipe to bottles (plastic flanges, end caps with holes drilled)
Agar1
Salt (NaCl, KCl, KNO3, etc)
Carbon cloth2
Bacteria3
Food for the bacteria4
Fish tank air pump with plastic tubing
Sealing materials (epoxy)
Resistors
Copper wire (plastic coated)
Wires with alligator clips
Multimeter for electrical measurements

Construction Procedure

2. Connect end caps of flanges to bottles

* Epoxy end caps or flanges to sides of plastic bottles.
* After epoxy has hardened, drill or cut holes through plastic bottles to allow for contact between liquid and the salt bridge.

3. Assemble Salt Bridge

* Dissolve agar into boiling water (at concentration of 100g/L).
* Add salt to the agar/water mixture while the mixture is still hot.
* Seal one end of plastic pipe.
* Pour agar/salt mixture into plastic pipe while it is still warm and before it begins to thicken.
* Allow the agar/salt mixture to cool and solidify.

4. Assemble electrodes

* Connect copper wire to piece of carbon cloth.
* Use epoxy to fasten the wire to the carbon cloth and to help protect from corrosion.
* Test electrodes with multimeter - there should be a small amount of resistance between a point on the carbon cloth and the end of the wire opposite the cloth.
* For anode, pass wire through a hole in the bottle lid and seal with epoxy. Cathode chamber does not necessarily need a lid.

5. Assemble MFC

* Connect salt bridge between the two plastic bottles and use epoxy to seal.