Evaluating a New Prototype of Plant Microbial Fuel Cell: Is the Electrical Performance Affected by Carbon Pellet Layering and Urea Treatment?

Plant Microbial Fuel Cells (PMFCs) represent a promising technology that uses electroactive bacteria to convert the chemical energy in organic matter into electrical energy. The addition of carbon pellet on electrodes may increase the specific surface area for colonization via bacteria. Use of nutrients such as urea could enhance plant growth. Our study aims to address the following questions: (1) Does carbon pellet layering affect the electrical performance of PMFCs? (2) Does urea treatment of the plants used to feed the PMFCs affect the electrical performance? A new prototype of PMFC has been tested: the plant pot is on the top, drainage water percolates to the tub below, containing the Microbial Fuel Cells (MFCs). To evaluate the best layering setup, two groups of MFCs were constructed: a “Double layer” group (with carbon pellet both on the cathode and on the anode), and a “Single layer” group (with graphite only on the cathode). All MFCs were plant-fed by Spathiphyllum lanceifolium L leachate. After one year, each of the previous two sets has been divided into two subsets: one wetted with percolate from plants fertilized with urea, and the other with percolate from unfertilized plants. Open circuit voltage (mV), short circuit peak current, and short circuit current after 5 s (mA) produced values that were measured on a weekly basis. PMFCs characterized by a “Single layer” group performed better than the “Double layer” group most times, in terms of higher and steadier values for voltage and calculated power. Undesirable results regarding urea treatment suggest the use of less concentrated urea solution. The treatment may provide consistency but appears to limit voltage and peak values, particularly in the “Double layer” configuration.