Singing Compost [heap#1]

A collaboration between Harun Morrison and Paul Granjon, Centre for Art and Ecology, Goldsmiths University London

 

Composting is the natural process of recycling organic matter, such as leaves and food scraps, into a valuable fertilizer that can enrich soil and plants. The compost material contains electrogenic bacteria, microbes that release electrons as part of their metabolic process.

 

The presence of such bacteria (Shewanella Oneidensis, Geobacter…) in most soils has led to the development of microbial fuel cells (MFCs), also known as mud batteries. MFCs capture this electronic flow for powering low-power circuits such as environmental sensors.

 

Research in MFC design has established that growing live plants in the cell benefits the lifespan of the bacteria. These batteries are called Plant MFCs.

 

An array of 16 plant MFCs [see tech note below] are integrated into the bed of the Singing Compost, their electrical output channelled to a circuit producing sounds that vary according to the voltage produced.

 

Tech note:

We found out later that the copper and zinc electrodes we used generate a current due to their electro-chemical properties (the oxidation of zinc occurs at the anode, while the reduction of copper ions happens at the cathode). It is possible that electrogenic bacterial populations close to the electrodes contribute to the electrical output, but most electricity harvested is from the copper-zinc oxydo-reduction reaction, with moist soil acting as the electrolyte. This system is referred to as an Earth Battery.

 

We are planning to update the installation with electrically neutral electrodes, for example made of graphite felt.

 

Singing Compost [heap#1] is installed in the Art Research Garden of Goldsmiths University London.