Activity: Bacterial Battery

Hiro and Courtenay with their bacterial battery.

On SCOPE's Renewable Energy episode, you saw Hiro and Courtenay build a battery from pond mud. Here's how they did it:

What you need

• a pond
• a plastic container
• water
• electrodes (carbon fibre preferably)
• nutrients

What to do

1. Scoop some mud from the bottom of your chosen pond.
2. Put it into the container, enough to make it about a fifth full.
3. Fill to the top with pond water.
4. Put in the two electrodes, one down in the mud and the other near the top of the water.
5. Connect up to a multimeter and see if you have any electricity being produced.

What's happening?

Bacteria live pretty much anywhere, but not all can be harnessed to create electricity. However, strains commonly found in pond mud can be used for this purpose.

The bacteria in the mud migrate to the carbon fibre electrode and as they breakdown their food they create electrons that are syphoned off by the circuit.

Eventually they will run out of food, and the flow of electricity will slow and stop.

Whilst the output of such systems is quite small, researchers are looking into different types of bacteria, and also different food sources (such as pollution) to see if such problems can be overcome.

To get you battery working successfully you may need to experiment with different ponds, nutrients and even other factors like temperature.