Geobacter: The Fuel of the Future

Problem: Humans need to start using renewable energy so that we can prevent climate change occuring due to greenhouse gases and battery waste.

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Name: Soham Shah

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School: Jeffrey Trail Middle School

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Teacher: Ms. Amanda Brown

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Abstract

The engineering problem I am trying to solve is the urgent need for humans to transition to renewable energy sources to prevent climate change caused by greenhouse gases and battery waste. Drill holes in two containers, add zinc and copper electrodes, place steel mesh for conductivity, connect with a salt bridge, and seal. Fill with soil, vinegar, and water as needed to complete the experimental setup. The Geobacter system maintained an average voltage of 4.87V over 13 days, with a standard deviation of 0.168V, indicating some variability due to the initial ramp-up and a gradual decline after Day 7 as substrate levels dropped. Despite this, it operated close to peak efficiency, proving reliable. In contrast, the alkaline battery delivered a much lower average voltage of 1.50V with minimal variability (0.017V), showing consistent performance but significantly lower energy output compared to the Geobacter system. The improved system utilized a Geobacter-based cell with regular electrolyte replenishment, enabling sustained microbial activity and prolonged voltage generation. Pairing zinc and copper electrodes with an acetic acid-based electrolyte facilitated a steady voltage increase during the first week, attributed to ample substrate availability and water replenishment. However, voltage declined after a week due to substrate depletion.This setup offers potential for small-scale renewable energy applications, such as powering devices in remote areas or integrating into wastewater treatment plants to simultaneously clean water and produce energy, presenting a cleaner, more sustainable alternative to traditional batteries.

Introduction (Background Research)

Criteria: The geobacter battery must create as much, if not more electricity than a standard AAA battery.

Constraints: The battery must cost less than $10, be completed in 3 weeks, take up less than one cubic meter, and last at least two weeks.

According to the National Resources Defence Council, “the unchecked burning of fossil fuels over the past 150 years has drastically increased the presence of atmospheric greenhouse gases, most notably carbon dioxide” (Turrentine 7).

According to the IBM, the good news is that it’s estimated about 70 percent of today’s global greenhouse gas emissions can be addressed by clean electrification (IBM 42).

According to HEAL THE PLANET, each year, Americans throw away more than 3 billion batteries, totaling 180,000 tons of hazardous waste. (HTP 12).

As stated in a Science Direct article, “a bacterium called Geobacter [that] shuttles electrons from organic material to metal-based compounds” (Pennisi 4).

Problem

Solution

Inspiration:

When browsing Youtube, I came across a video by Keystone Science, which showcased a jar of soil, creating electricity.

Seeing this, I was frustrated that such a good idea wasn’t put to better use, so I decided to elevate it to something actually applicable.

The Engineering Solution, Prototype/Model to be tested.

1. Role of 1st Steel Mesh and Zinc Wire: Zinc undergoes oxidation, and releases atoms that, combined with the electrons from the Geobacter, create zinc ions (Zn²⁺). The released atoms travel through the steel mesh attached to the zinc wire, initiating the flow of negative charge.

2. Role of Geobacter: Geobacter bacteria release the electrons. These bacteria metabolize organic materials in the soil and facilitate electron transfer to nearby metal ions.

3. Role of Salt Bridge: The salt bridge or rope soaked in water enables ionic exchange between the anodic and cathodic chambers, so that electron neutrality is stable.

4. Role of the 2nd Steel Mesh and Copper Wire: A different steel mesh collects electrons transported through the salt bridge and transfers to the copper wire.

Materials

1. 2 Containers (11.5 L.)
2. Manilla Rope (2.5 cm. diameter and 15 cm. length)
3. Caulking (83 ml.)
4. 2 Copper Wire (12 gauge and 15 cm.)
1. Revised: Zinc Wire (12 gauge and 15 cm.)
2. Revised: Copper Wire (12 gauge and 15 cm.)
5. Adhesive Tape (60 cm.)
6. 2 Steel Mesh (13x13 cm.)
7. Drill
8. Drill Bits (Brad Point Drill Bit 5mm, Flat Drill Bit 17 mm.)
9. Soil (2 L)
• Revised: Vinegar (50 ml.)
10. Water (2 L)
11. Salt (Pinch)

Procedure

Container 1 Setup:

1. Drill Holes in the Lid:
• Use a Brad Point Drill Bit to drill five holes in the lid of the first container: 4 around and 1 in the middle
2. Prepare Steel Mesh:
• Take a 13x13 cm steel mesh and fold it in half.
• Fold it in half again to create a smaller square.
3. Prepare Copper Wire and Steel Mesh:
• Cut 15 cm of copper wire and bend it into an [ shape.
• Unfold one fold of the steel mesh and securely attach it to the 15 cm copper wire.
• Insert the longer part of the [-shaped copper wire through the center hole of the lid so that the wire hangs down into the container.
4. Drill Side Hole for Rope:
• Use a Flat Drill Bit to drill a hole in the middle of the side of the first container.
5. Insert Rope and Seal:
• Insert the rope soaked in salt water through the side hole and seal the hole with caulk to prevent leaks.
6. Add Water:
• Pour 2 liters of water into the container.

Container 2 Setup:

1. Drill Hole in the Lid:
• Use a Brad Point Drill Bit to drill one hole in the center of the lid of the second container.
2. Prepare Zinc Wire and Steel Mesh:
• Cut 15 cm of zinc wire and bend it into an [ shape.
• Unfold one fold of the zinc wire and securely attach it to the zinc wire.
• Place the attached zinc wire inside the second container.
• Insert the longer part of the [-shaped zinc wire through the center hole of the lid so that the wire hangs down into the container.
3. Add Soil and Vinegar:
• Add 2 liters of soil and 50 ml of vinegar to the second container.
4. Drill Side Hole:
• Use a Flat Drill Bit to drill a hole in the middle of the side of the second container.
5. Seal All Holes:
• Use caulk to seal all drilled holes in the second container to ensure no leaks.

Results – Data/Observations

Revised Solution and Prototype/Model

Design #1: 12 gauge copper wire in both anode and cathode

Design #2: Copper wire in cathode, zinc wire in anode, vinegar added to anode

1. Better Material Pairing: Zinc and copper were chosen for their contrasting electrochemical properties. Zinc, which oxidizes easily, served as the anode, releasing electrons into the circuit. Copper acted as the cathode, accepting these electrons during the reduction process.

2. Electrolyte: Vinegar, which contains acetic acid, was used as the electrolyte. This addition allowed the geobacter to feed more and produce electrons, which made the chemical reactions much more efficient and helped sustain the 5-volt output.

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Discussion

Statistics

The Geobacter system delivered an average voltage of 4.87V over 13 days, with a standard deviation of 0.168V. This variability is due to the initial ramp-up and the gradual decline after Day 7 as substrate levels decreased. Despite this variation, the system operated near peak efficiency, demonstrating its reliability.

In contrast, the alkaline battery had a significantly lower average voltage of 1.50V, with a very small standard deviation of 0.017V. This reflects the predictable nature of primary batteries, designed to deliver steady energy output until near depletion. While its consistency is notable, the alkaline battery's voltage output falls far short of the Geobacter system, highlighting the superior energy potential the bacterial system holds over the alkaline.

Trendline/Pattern

Additionally, a trendline analysis of the standard curve shown by the Geobacter revealed that after Day 7, the system’s voltage dropped at a gradual rate of about 0.07V per day.

In contrast, the alkaline battery performed exactly as expected, which is why they remain so commonly used, despite their environmental drawbacks.

Potential Variable and Other Studies

The data suggests that the decline in voltage after Day 7 was due to the substrate in the Geobacter system not being replenished. Initially, the system's voltage increased steadily, peaking at 5.12V by Day 8, as microbes consumed the available organic material in the mud. Over time, as the substrate depleted, the microbes had reduced access to nutrients, leading to a gradual voltage decline.

Replenishing the electrolyte water throughout the experiment likely contributed to the steady voltage increase during the first week. This approach contrasts with other studies where Geobacter systems maintained peak voltage only briefly. By refreshing the electrolyte water, we ensured efficient ion transport between the anode and cathode, supporting the system's initial performance.

The alkaline was significantly less money, took up much less space, and lasted indefinitely, until it was used. The geobacter met the requirements and was under $10 and took up less than 1 cubic meter.

Conclusion

The key improvement in the system’s design was the use of a Geobacter-based cell, combined with regular replenishment of the electrolyte, which allowed for sustained microbial activity and voltage generation over a longer period. By pairing zinc and copper electrodes with an acetic acid-based electrolyte and leveraging the natural metabolic processes of Geobacter, I achieved a steady increase in voltage during the first week.

The voltage increased at first because the microbes were working well and had enough substrate to process. But after about a week, the voltage started to drop. This is likely because the food for the microbes ran out, and we didn’t replace it. On the other hand, we did keep adding freshwater to the system, which helped the voltage keep going up during the first week. This fits with what other studies have shown—most cells only stay at their peak for a little if the substrate isn’t replaced.

This kind of setup could be used to create renewable energy in small amounts. For example, it could power small devices in places where regular batteries aren’t practical. Another use could be in wastewater treatment plants, where the microbes could clean the water and produce energy at the same time. It’s a cleaner and more eco-friendly option compared to regular batteries, which create a lot of waste.

Some additional questions for further research: What happens if we regularly add more mud or another type of organic material for the microbes to eat? Are there other kinds of substrates that could work better than mud? Would changing the setup improve how much energy it produces? Could this system work better if we tried it on a bigger scale or used it in real-world situations like wastewater plants?

Reflection/Application

• What did you learn from doing this project?
• Before starting this project, I didn’t really know much about batteries or how to use a multimeter. At first, I thought I wouldn’t need to learn much, but I was very wrong! This project ended up teaching me a lot about electrical engineering and how it can connect with biology and physics to create renewable energy sources. I learned about how ions and electrons move, and I got a better understanding of volts, amps, and ohms. I even discovered that some bacteria, like Geobacter, can produce electricity. It was amazing to see how science in different fields can come together to make something completely new.
• How can your results be applied in everyday life?
• On a small scale, someone could use a similar setup to build their own battery to power small devices, like LEDs or pedometers, in places where regular batteries aren’t practical. On a larger scale, waste treatment plants could adopt this technology. They could use the waste as a substrate for the microbes, which would clean the water and generate electricity at the same time. This could save energy costs and reduce environmental waste.
• How could your results be applied to other studies?
• This research could inspire investigations into other types of bacteria or organic materials that might perform even better than Geobacter and mud. Other studies might also test how scaling up the system—like using larger electrodes or reactors—could make it suitable for industrial applications. Finally, researchers working on renewable energy could combine this technology with solar panels or wind turbines to create hybrid systems that are even more efficient and sustainable.

References Cited

• Turrentine, J. (2022, September 13) What are the causes of climate change? Retrieved from https://www.nrdc.org/stories/what-are-causes-climate-change
• Facts about battery waste. Retrieved from https://healtheplanet.com
• (2021, June 7) Flexible energy platform: Empowering renewable power. Retrieved from https://www.ibm.com
• Nevins, K. P. (2011) Geobacter. Retrieved from https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/geobacter
• Keystone Science. 2026. Video. Retrieved from https://www.youtube.com/watch?v=BN5YLd5ni7k

1. Electron Generation by Geobacter:

09/10 - After continuous research, came across Geobacter, a bacteria capable of producing electricity.

Geobacter is a unique bacterium capable of generating electricity as part of its natural metabolic process. It feeds on organic compounds like acetate, breaking them down to release energy. During this process, electrons are produced as a byproduct. Unlike most bacteria that use oxygen as an electron acceptor, Geobacter transfers these electrons externally. The electrons travel through the bacterium's pili, which are conductive nanowires, to reach metal surfaces or electrodes. This external electron transfer is what makes Geobacter particularly valuable for bioelectric applications.

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The electrons generated by Geobacter are essentially "waste" from its metabolism, but they play a critical role in electricity generation. The pili act as electrical conduits, connecting the bacterial cell to nearby metal ions or electrodes. This ability to release electrons into an external medium sets Geobacter apart from most other microorganisms, enabling it to directly participate in electrochemical reactions that produce electric current.

2. Combining with Metal Ions:

10/15 - Discovered how electrons combine with atoms create ions

At the anode, where Geobacter is located, the electrons produced by its metabolism interact with metal ions in the surrounding solution. For example, positively charged ions that have been released due to oxidation like Zn3+ (zinc) can accept the electrons, undergoing a reduction reaction to form Zn2+. This reduction process helps stabilize the electrons and facilitates their movement through the system. The interaction between electrons and metal ions creates a redox (reduction-oxidation) reaction, which is essential for transferring energy in the form of electricity.

This step is crucial because the metal ions serve as a medium for charge transfer, effectively bridging the gap between the bacterial metabolism and the electrode system. The reduced metal ions remain in the solution, but their presence ensures that electrons keep flowing from Geobacter to the electrode. This continuous flow sustains the electric current and allows for further reactions to take place in the system.

3. Salt Bridge Function:

10/28 - Learned how salt bridge encourages ionic exchange between anode and cathode

The salt bridge is a critical component of the system, ensuring that the electric circuit remains balanced while electrons flow. It typically contains an electrolyte solution like NaCl or KCl, which provides mobile ions to counteract the charge imbalance created during electron transfer. As electrons are released by Geobacter and move to the anode, an excess of negative charge begins to accumulate. To neutralize this, positive ions (e.g., Na⁺) from the salt bridge migrate toward the anode, while negative ions (e.g., Cl⁻) move toward the cathode.

This ion movement prevents the buildup of excessive charges on either side, which would otherwise stop the flow of electrons. The salt bridge ensures that the system remains electrically neutral and that the electron flow can continue unimpeded. Without this component, the circuit would quickly become imbalanced, halting electricity production.

4. Ionic Flow to Copper Wire:

10/29 - Completing circuit, researched on how ions travel to copper wire

At the anode, Geobacter bacteria generate electrons as part of their metabolic process, and these electrons flow through an external circuit, such as a copper wire. This movement of electrons creates an electric current, which can be used to power various devices or systems. As the electrons leave the anode, the system begins to accumulate a charge imbalance, and the circuit is completed by the movement of ions.

The ions from the water, which have traveled through the salt bridge to the cathode side, move toward the steel mesh and copper wire at the cathode. These ions help balance the charge in the system and allow the electron flow to continue. The copper wire conducts the electrons from the anode to the cathode, enabling the creation of electricity. At the cathode, the incoming electrons combine with hydrogen ions (H⁺) in the solution. This ongoing flow of ions and electrons through the wire and solution maintains the electric current and keeps the system running efficiently.

Logbook Page

08/12 - Selected topic of renewable energy, investigated soil battery

09/04 - Got topic of geobacter battery approved by teacher

09/09 - Investigated battery waste and researched how soil creates electricity

09/14 - Got all materials for project

09/17 - Started to write procedure and create battery

09/25 - Completed battery, started to record voltage and amperage

10/08 - Completed testing period and made data table and graphs

10/25 - Analyzed stats and completed discussion and reflection/application

11/01 - Formatted references cited and uploaded logbook pictures

11/18 - Completed abstract

12/1 - Completed video