Redesigning the Microbial Fuel Cell

Ashley Aguilar

?

Where Our Current Energy Comes from

Percentages from U.S. Energy Information Administration

​

78% fossil fuels

The Problem With Non-Renewables

Coal

Petroleum

Science Rules!

Recent science research has allowed us to make strides toward alternative energies.

What are Microbial Fuel Cells (MFCs)?

• Generates clean electricity
• Using bacteria respiration
• Cathode and anode

Rubber plug -

Seals water from leaking

Anode

Has bacteria

Air Cathode -

Where oxygen, electrons, and reduced materials meet

Brush Anode -

Has a lot of surface area

Cathode - Where oxygen, electrons, and reduced materials meet

Hole sealed by pipe screw fitting to prevent leakage but allow feeding

How Do They Work?

In short,

1. Bacteria remove electrons from organic material
2. Discharge them to anode
3. Flow through wire to cathode (like - and + in batteries)
4. Electricity generated!

https://www.google.com/search?q=mfc+animation&rlz=1CASMAE_enUS682&oq=mfc+animation&aqs=chrome..69i57j0l5.2116j0j7&sourceid=chrome&es_sm=93&ie=UTF-8&safe=active&ssui=on#safe=strict&tbm=vid&q=microbial+fuel+cell+animation

​

Explain while animation plays?

​

​

Explanation of Problem

• MFC technology not developed enough to work be implemented on a large scale
• Researchers are beginning to test alternative electrode materials
• more efficient MFC
• more benefits

​

Carbon fiber fabric

Benefits of Ceramics

(As a MFC cathode)

• Ceramic material cathode
• Graphene nitrogen doping
• water filtration
• withstands high pressure
• widely available resource

Question

How does a ceramic cathode perform compared to the conventional carbon fabric cathode?

Objective

Our focus was to engineer a ceramic air cathode for MFCs to test against conventional materials and compare performance.

Methods

1. Ceramic membrane production is done by mentor
2. Control trial carbon fabric membrane production is done by mentor
3. Other materials needed to build the fuel cell are acquired by mentor
4. Anode side assembly (student and mentor)
1. Anodes cut from carbon fiber brushes
2. Plugs drilled to allow brush wire to pass through
3. Hole sealed with Aquarium grade Silicon Caulk
4. ​
5. Cathode side (stud
• Membranes mounted on 1.25” Schedule 40 PVC Reducer bushings to allow them to be swapped between reactors and to protect them from breakage.
• Wire mesh disk cut and superglued to threaded end of 1,25" reducer bushing
• drill (mentor performed) through plastic body so titanium wire could be inserted from outside end of plug perpendicular to threads using #57 drill bit
• Marine Epoxy used to mount membranes on top of wire mesh, and to seal connection between membranes and plug from water leakage.
• MG Chemicals 8330S epoxy was used to make electrical connection between membrane and titanium wire.
6. Make external connections to the resistor and the datalogger
1. The electrical output over time will be measured for each type of fuel cell to determine peak output once cells have acclimatized and time to acclimatize. Linear Sweep Voltammetry (LSV), Electrical Impedance Spectroscopy (EIS) and Open Channel Potential (OCP) readings will be taken at peak output over the course of several feeding cycles to determine the quality of ceramic membranes as compared to conventional, and whether they remain stable over time.

​

Two of the T-pipe MFC cells wired to datalogger

Datalogger wired to cells takes voltage readings every 5 minutes.

Results

• Design revisions
• MFC acclimatization
• Multiple tests (gamry software)
• EIS
• LSV
• OCP
• Voltage output

Open Circuit Potential (OCP)

Source: Louis Dankovich

Linear Sweep Voltammetry (LSV)

Source: Louis Dankovich

Electrochemical Impedance Spectroscopy (EIS)

Source: Louis Dankovich

Voltage

*MFCs may not be fully acclimatized at time depicted in graph

*day 0 is not the day of inoculation (avg. performance)

Source: Louis Dankovich

What All These Graphs Tell Us

• Inconclusive
• OCP
• Inconclusive
• LSV
• Control 2 seems to have the highest value
• EIS
• At first glance, the ceramic cathode membranes seem to have less electrical resistance and less diffusion resistance
• Voltage
• Inconclusive, although one control does perform higher than all the others

Limitations of Research

• Working with lifeforms
• Not always reliable
• Even when fed
• Moving labs
• Limitation of measuring instruments and software
• May occasionally give nonsensical data
• Complications with large scale MFCs that may not be in small MFCs
• A small testing size
• Calculations

The Future of MFCs

• Wastewater treatment and energy production
• Sewer systems
• Remote locations
• Resource poor nations
• ..or anywhere there’s bacteria

​

?

Pipe MFC

Pro:

1) Using off the shelf plumbing fittings allows for these to be constructed quickly and easily. Also allows for a variety of configurations or implementation in existing networks.

2) Attaching ceramic to pipe fittings allows the membranes to be swapped between reactors for tests (or installed more simply in real world application)

3) High fluid volume means that loss of fluid is less likely to damage the reactor

4) Not having to clamp in membranes means they are less likely to be damaged while assembling systems

5) The T pipe configuration can be pressurized so membrane can be used for both filtration and MFC Cathode.

Con

1) Large volume may decrease efficiency of COD utilization

2) Significant space between anode and cathode may decrease power output compared to conventional.

References

Questions