Dependent Variable - Type of Soil and Size of a Microbial Fuel Cell

Report
The Effect of Type of Soil and Size on Microbial Fuel Cell Efficiency
Abenet Addisu
Procedure and Materials
Introduction
Rationale
• The Earth is getting more polluted every day, and scientists must
develop creative solutions. Every chemical, pesticide, or material
used contributes to the pollution we have on Earth. It could be
argued that our planet is in a time of crisis because of all the
pollution created by our daily activities.
Purpose
• The purpose of this project is to optimize an alternative energy
source, the microbial fuel cell. With a successful outcome, this
project can help alleviate future energy This project will specifically
test different sources of organic material and different fuel cell sizes
to optimize microbial energy production.
Holes will be cut into the sides of the anode and cathode containers, and
then the compression fitting will be glued over the hole, but any leakage in
the microbial fuel cell will be checked before it is activated. Next, four
pieces of carbon cloth will be cut into squares and the copper wire will be
glued around the edge of the carbon cloth with conductive epoxy. After
this, the salt bridge will be made and placed in the compression fitting.
Distilled water will be poured inside of the cathode, while the anode will be
filled with the mud-like soil. A small hole will be cut into the lids of the
anode and cathode containers so the free end (without any carbon cloth)
of the electrodes that were made will be put inside the anode and
cathode. Alligator cables will be hooked onto the ends.
Experimental Design Diagram
Hypotheses
Research Hypothesis 1 (Soil Type): The microbial fuel cell created
using soil with more organic material will produce the most voltage.
Independent Variable: Different types of soil and size of microbial fuel
cell.
Controls: The control for the size will be a 12 cup sized microbial fuel
cell and the control for the soil will be topsoil.
Potting
Soil
1
Garden
Soil
1
Manure
5 cup
Top Soil
(C)
1
12 cup
1
1
1
1
20 cup
1
1
1
1
Research Hypothesis 2 (Size): The size of the microbial fuel cell will
impact voltage production with the largest being most effective.
Research Hypothesis 3 (Type & Size): The combination of the
largest fuel cell with the manure will produce the most voltage.
Null: Soil type and size will have not effect on microbial fuel cell
voltage production.
Background Information
Independent Variable
• This project has two independent variables which are the size of the
microbial fuel cell and the type of soil inside the fuel cell.
• Three fuel cells will be designed that hold 5, 12, and 20 cups of organic
material. Each of these designs will be tested with the different soil types.
Data Analysis
1
Constants: The anode, cathode, external circuit, the PEM, the amount
of soil and water put into each trial.
Dependent Variable: Voltage produced.
Qualitative Observations of Soil Quality
• The topsoil was very dark and rich, and it didn’t have a hard time
absorbing the water I poured in. The manure acted the same as the
topsoil except the color was a light brownish. Garden soil and potting
soil didn’t absorb much water, had a lot of wooden pieces .
Quantitative Measurement of Voltage
• Compared to the other fuel cells, the 5 cup microbial fuel cell seemed to
have done the worst. The manure also had the lowest voltage
production in two out of the three sizes. Potting soil came in at a close
second as the worst out of all the soils, but had manure beat in the 12
cup fuel cell. Out of all the sized fuel cells, topsoil had the most voltage
production. It was also the control, and the mostly used soil in the United
States.
Conclusion
Research Hypothesis 1 (Soil Type): The fuel cell created with more
organic material will produce the most voltage.
• Hypothesis 1 was not supported as top soil had more voltage than
the manure tested.
Research Hypothesis 2 (Size): The size of the fuel cell will impact
volt production with the largest being most effective.
• Hypothesis 2 was supported as the largest microbial fuel cell
produced the most voltage.
Research Hypothesis 3 (Type & Size): The combination of the
largest fuel cell with the manure will produce the most voltage.
• Hypothesis 3 was not supported as the combination of the largest
with topsoil produced the most voltage.
Null: Soil type and size will have not effect on microbial fuel cell
voltage production.
Future Research
• Expanding on the independent variables could be tested to
discover the limit of microbial fuel cells. Instead of testing which soil
produced the highest output of electricity, getting more specific and
testing different bacteria will help with results.
Dependent Variable
• The dependent variable in this experiment is the amount of voltage
produced from each type of soil and size of a microbial fuel cell. Voltage
was measured in this experiment because it’s also used to determine the
electric potential difference between the two points that create the
current.
• It was measured by attaching a multimeter to the wires from the anode
and cathode. It was measured in volts.
The pictures above show the 20 cup fuel cell being tested with top
soil. This arrangement produced the most energy. Photos by
In this experiment the data collected was quantitative and qualitative
because the voltage produced was recorded and features of each soil
sample noted.
Bibliography
The figure above shows voltage production of the four types of
soils along with the three sized microbial fuel cells.
• EAIS. (2010). Types of soils. Retrieved from
http://www.eais.net/soil/#1
• Gav, B. (2006, May 23). Peak Energy. Retrieved April 13, 2011, from
Blogspot: http://peakenergy.blogspot.com/2008/05/dirt-powered-fuelcells.html
•Harper, G. (2008). Fuel Cell Projects for the Evil Genius. Los Angeles:
McGraw Hills.
• Liu, H. (2004). Electricity Generation Using an Air-Cathode Single
Chamber Microbial Fuel Cell in the Presence and Absence of a Proton
Exchange Membrane. Environmental Science and Technology .

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