Microbial Fuel Cell

Using Porous Materials To Make Energy

Soil is abundant with diverse microbes that convert carbon-rich organic matter into energy and nutrients, essentially the microbial equivalent of breathing and the reverse of photosynthesis. During this process, excess energy is produced, which can be harnessed and used in microbial fuel cells (MFCs).


Why We Need This Knowledge

Microbial fuel cells (MFCs) represent a groundbreaking technology that harnesses the power of microorganisms to generate electricity from organic matter. Understanding MFCs is essential for developing sustainable energy solutions, reducing reliance on fossil fuels, and mitigating environmental pollution. This knowledge can lead to advancements in waste treatment processes, as MFCs can convert wastewater into a valuable energy resource while simultaneously purifying it. Additionally, MFCs hold the potential to provide renewable energy in remote or off-grid locations, contributing to energy security and resilience. Embracing this innovative technology is crucial for addressing global energy and environmental challenges.

Project Overview

Conducted by Lars van Broekhuijsen at Utrecht University (UU) and supervised by Jan Gerritse at Deltares, the project aims to (re)build diverse prototypes that can be displayed in educational centers to serve as a testament that alternative energy can be hidden in plain sight and to generate scientific interest in young and old.

Scope and Interdisciplinary Nature

The project integrates knowledge from microbiology, chemistry, soil science, materials science, and electrical engineering. By combining insights from these disciplines, we can make improvements to prototype performance and demonstrate the practical applications of MFC technology in real-world settings.

Collaboration

Lars van Broekhuijsen
Student Geosciences
Project Lead: As part of his internship at SoS, Lars van Broekhuijsen undertook this project to gain hands-on experience in the lab, execute an experimental research project, and build professional connections.

Dr. Jan Gerritse
Senior researcher
Jan Gerritse is a microbiology specialist and senior scientist at Deltares. Jan has 27 years of experience as a researcher in the field of applied and environmental microbiology. His work involves the detection, control, and utilization of microorganisms in their natural environments and in laboratory systems.

Unique Aspects
This project was undertaken by a bachelor student affiliated with the Structures of Strength (SoS). The SoS network facilitated his access to the necessary experts, significantly accelerating the project’s progress and providing valuable guidance. Despite lacking prior knowledge in microbiology and electrical engineering, Lars successfully achieved the project’s goal with the help of Jan Gerritsen and Gerard Kuipers.

Insight
Organic matter together with oxygen and the presence of microbes is normally transformed to carbon dioxide, water, and nutrients (eq. 1). However, when we deprive the environment of oxygen and add microbes that can work under anareobic conditions, we halt a part of this process to just the oxidation part (eq 2.).

Eq 1. CH2O +O2 –> CO2 + H2O + Nutrients + Energy

Eq 2. CH2O + H2O –> CO2 + 4(H^+) + 4e^- (Oxidation)

The result is that there are free electrons that can be put to work.

The presence of electrogenic or cable bacteria can directly transfer electrons between one another, making the soil conductive. This allows the electrons to flow through the soil to the anode and enter the electrical circuit to flow through whatever machinery in the circuit. The loose protons (H+) want to combine with oxygen (O2) and the electrons to produce water. They will flow to the location where the oxygen and electrons are, which is the cathode that is in contact with air or another oxidator (eq 3), finishing the overal reaction (eq 4)

Eq 3. O2 + 2H2O + 4(e^-) à 4OH- (Reduction)

Eq 4. CH2O + O2 à CO2 + H2O (Net reaction)

A Microbial Fuel Cell consists out of:

Non conductive housing.
The substrate in which the bacteria and organic matter is mixed.
Two electrodes, one working under anaerobic condition and the other under aerobic conditions.
A membrane that separates the anaerobic and aerobic compartments, but is able to let through the produced protons.

Image by J.Gerritse

Applications
MFCs can generate power from biomass while decomposing the fuel driving the process. This fuel can be waste that otherwise requires treatment before disposal. Unlike other biomass energy production methods, MFCs do not need the material to be pre-treated, such as through fermentation or burning. MFCs can decontaminate or desalinate wastewater by breaking down organic matter, reducing sludge, and potentially sustaining the process if scalability improves. MFCs are ideal for powering low-energy electronics like remote sensors and lights, functioning indefinitely in remote areas where battery replacement is difficult. They can also aid sustainable farming by monitoring soil health and powering sensors for precise farming techniques.

Results
In total 8 different versions of the MFC were constructed and tested, each with their own traits. Power output maxed out at 100 mV at a resistance of 1000 ohm, giving 10 microwatts. This is by far not enough to power a LED or small motor, however we are holding out good hope that the electrogenic microbe population will deliver more power over time.

What we have learned from these tests is:

The microbes need time to adjust and multiply before energy production increases.

In this graphs it can be seen that the microbes produce more voltage over time after assembly. It can range between days to months before the maximum is reached.

Too much organic matter in the anode compartment is not beneficial for the energy production.
When too much organic matter is added to the anode compartment, fermentation occurs. This creates a more acidic environment, not beneficial for the electrogenic microbe population and lowering power output.

Scalability is tough to apply.
Going into the testing phase we knew that upscaling wouldn’t be easy. However we had some ideas to work around it. This proved more difficult than expected, striking up new issues once we resolved the old ones.

Drawbacks
Despite their potential, MFCs face challenges. The primary issue is the low power output relative to size and cost. Achieving higher voltage for practical use is difficult, and upscaling presents problems like proton movement resistance and pH imbalance, which harm microbes and electrodes. Large membranes are costly, comprising 60% of fuel cell expenses. Linking many small cells to increase voltage is expensive due to the need for numerous electrodes and membranes. Additionally, maintaining a stable environment for the bacteria is crucial, requiring specific temperature and pH levels, and the soil contact accelerates electronic degradation, halting cell function.

Future Research
Research on MFCs is still new, and efficiency optimization requires further study, including finding suitable microbes for varied conditions and developing cheap proton exchange membranes to get the cost down. MFC’s have shown improvements with companies creating self sustaining measurement stations. Industrial use is a bit down the road, but with more research it might be here sooner than we expect.

Lets work on a greener future together.