We are exploring their compost heaps as a site for the bio-battery that will power the server for FutureEverything’s primary public-facing website. The website will undergo a redesign focused on reducing computational demands and climate impact while maintaining high standards of aesthetic quality, usability, and accessibility. This redesigned site will demonstrate innovative climate-conscious digital design principles that acknowledge and respect more-than-human perspectives and needs.
For testing and experimentation to build the low-power server which is powered by a stack of compost-based batteries, we took compost samples from three heaps at different phases of composting back to London with us. We also visited Sow the City at the Boiler House to discuss collaboration on compost analysis. This analysis will be performed both prior to and during the compost-based battery installation to assess potential impacts on the compost ecosystem throughout the hosting period.
Environmental impact assessment is an important component of this project. With Nature represented on FutureEverything’s board and its ongoing inquiry into mitigating anthropocentric and colonial perspectives in pursuit of multispecies justice, ecological considerations will remain central to every stage of the project’s development and implementation.
Back in London, Shinji Toya and Mariana Marangoni began experimenting with bio battery techniques, testing different equipment and materials.
In the first stages of material experimentation, both earth batteries and microbial fuel cells (MFCs) were being considered, each with its pros and cons: while earth batteries are much simpler to set up, they wield significantly less electricity. That’s because it produces an electrical current using electrochemical reactions in damp soil or mud (adding water makes it more potent!).
On the other hand, MFCs convert chemical energy from organic waste matter to electrical energy by utilizing exoelectrogenic bacteria existing in the decomposition process.
The basic components of compost batteries are the addition of electrodes – an anode and a cathode—typically made of different metals like copper and zinc, that react with the complex electrolyte solution that is the soil or compost. Through moisture, dissolved salts and minerals, organic acids from decomposition, and lively microbial activity, a lot of chemical reactions happen beneath our feet.
The flow of electrons moves from anode to cathode through the circuit. At the anode, the atoms of the metal used (for example zinc) lose electrons and become ions through oxidation. This flow of electrons can be harnessed to provide usable electricity. At the cathode, electrons from the circuit are accepted. To complete the circuit, the free-flowing ions in the moist compost migrate to either the cathode or the anode, depending on whether they are positive or negative ions (positive ions flow to the cathode, negative ions to the anode). This movement of ions completes the electrical circuit. Without ion movement through the compost, the electron flow in the wire would quickly stop as charges built up at the electrodes.
What makes compost an interesting and complex electrolyte is the microbial activity that might enhance the workings of the electric circuit. When microorganisms break down organic matter, they produce organic acids which increase conductivity. Additionally, some bacteria can directly transfer electrons to electrodes, creating a microbial fuel cell. So compost as an electrolyte is fascinating but challenging because of this additional complexity. It’s not a stable environment—temperatures fluctuate, and decomposition occurs in various stages between beginning and end points.
To understand how to work with this complexity, we set up experiments using different electrodes and compost samples at varying stages of decomposition and moisture content.
Here are entries from the records of experimentation for the earth batteries:
