Optimizing Plant Microbial Fuel Cell Energy Output: The Effect of Anodic Substance and Shape

By: Maya G.
Year: 2023
School: Fairmont Private Schools, Anaheim Hills
Grade: 8
Science Teacher: Michael Morin

In a world facing ever-increasing energy demands and environmental challenges, young innovators like Maya are stepping up to the plate, using their scientific curiosity and ingenuity to seek sustainable solutions. Maya, a student participating in the Orange County Science and Engineering Fair, embarked on a fascinating project aimed at improving the efficiency of eco-friendly fuel cell technology known as Plant Microbial Fuel Cells (PMFCs).

Maya’s project had a clear objective: to determine which conductive material and shape for the anode in a PMFC produces the greatest energy output. Her motivation? To explore ways to enhance the efficiency of PMFC technology, ultimately benefiting our planet’s environment.

Maya constructed twelve PMFCs using Neanthe Bella Palm plants. Her PMFC model included a layered design: mud, anode, plant roots, surrounding soil, and a stainless steel mesh cathode. What set her experiment apart was the variation in anode materials. She divided the PMFCs into four groups, each containing three different anode materials:

  1. Stainless steel mesh
  2. Stainless steel mesh with activated carbon
  3. Graphite plate
  4. Carbon felt and copper

Maya then connected the anodes and cathodes using insulated copper wires to a breadboard with a load resistor inserted to create a circuit. She planned to measure the voltage across the resistor and subsequently derive the current output of each PMFC.

Over the course of her experiment, which spanned 168 hours, Maya meticulously monitored the voltage output of each PMFC every 12 hours using a multimeter. Her hypothesis was that the stainless steel mesh with activated carbon anode would produce the greatest voltage output. This hypothesis was rooted in her understanding of the electrical conductivity of stainless steel, the increased surface area facilitated by activated carbon, and the beneficial bacterial bonding affinity with the carbon surface through molecular recognition.

However, science often has its surprises. Maya’s results defied her initial hypothesis. The PMFC with the carbon copper brush electrode outperformed the other configurations. This unexpected outcome was likely due to the carbon brush’s greater microscopic surface area, which encouraged more significant bacterial growth and electron output, despite its lower electrical conductivity compared to stainless steel.

Maya’s project not only adds to our understanding of PMFCs but also highlights the importance of scientific inquiry and adaptability. Her findings suggest that factors beyond electrical conductivity play a crucial role in PMFC efficiency, emphasizing the need for further exploration in this field.