Microbial Fuel Cells: An Alternative Electricity Source from Mud?

Overview

Objectives/Goals Objective/Goals: To design a microbial fuel cell using decomposing anerobic organic sediment and test which of two sources of sediment, fresh water or salt-water, can generate more microbial fuel cell electric current. Methods/Materials Methods/Material: Sediment microbial fuel cells were designed by first showing that the electrodes, electric circuit and detection system worked in a microbial fuel cell kit positive control. Deep fresh water sediments from 3 sites, and salt-water sediments from 2 sites, were collected as was the water above each sediment. Using 14 cm x 14cm x 22cm plastic jars, sediment was placed in half the jar, with a carbon fiber electrode as the anode placed in the middle of the sediment. A similar piece as the cathode was placed in water from the same source above the sediment. An electrical circuit was set up, and current and voltage was measured every 8 hours for five days using a multimeter. Results Results: Current (uA) and voltage increased over 3-4 days following setting up of each microbial fuel cell and then leveled off during days 4-5. Greater final current (uA) was observed from the 2 salt water sediment microbial fuel cells and water than from 3 made from fresh water sediment. The voltage was higher in fresh water sediment fuel cells. A negative control made by killing the bacteria by boiling the sediment had lower current and voltage, suggesting that the fuel cell electricity was produced by microbes. Conclusions/Discussion Conclusions/Discussion: The data I collected was different than my hypothesis as I thought the fresh water sediment would have richer anerobic nutrients and generate more bacteria and electrical current, but salt-water sediment produced more current. This may be useful as an electrical source in the ocean and for organic sediment recycling. Although the current was low (~200mA), it appears to be biologically generated as the current increased with time, and the current was greatly reduced in a negative control fuel cell made with boiled sediment.

Competition history

• CSEF 2011 Alternative Energy (Junior Division Only) · Entry J0232

Resources

• CSEF project summary ↗

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