Electrogenesis in plant–microbial fuel cells in parallel and series connections

The electrogenic properties of plant–microbial fuel cells (P-MFCs) assembled into a battery are studied. The operation of a single cell is studied experimentally in comparison with parallel and series connections of cells, which are two options for connection in an electrical circuit. A potential difference of $\sim$ 70 mV, which gradually vanishes, is registered in a P-MFC that does not include a plant organism. We hypothesize that the root system, with involvement of electrogenic chemoorganotrophic microorganisms, gives rise to diffusional electromotive force. We show that in series connection of three fuel cells the bioelectric potential generated by an individual cell, which is 170 mV, increases only by a factor of 1.5. In parallel connection of three cells, the current produced under a load increases, but also only by a factor of 1.5, and this takes place at later developmental stages of the plants, which is presumably caused by triggering certain compensatory mechanisms that diminish the electrogenic properties of the plants.