Field Testing of Various Microbial Fuel Cell ... - Mortenson Center

Field Testing of
Various Microbial Fuel
Cell Designs
Kampala, Uganda
Acknowledgements:
• Zhigong (Jason) Ren, Associate
Professor of Engineering, University of
Colorado-Denver
• Water For People, Kampala, Uganda
Funding Provided by the Following:
• The Mortenson Center
• Water for People
• Bill & Melinda Gates Foundation
James Perlow
October 20, 2012

Executive Summary
Microbial fuel cell (MFC) technology harvests the energy produced by microbes as they degrade
human waste. This energy is converted to electricity and can be used as a renewable power
source for lights or other low demand applications. The challenge facing this technology is how
to take it from the laboratory to the natural environment, most crucially, how to make this
technology affordable.
This project, funded by the Mortensen Center in Engineering for Developing Communities
University of Colorado at Boulder, Water for People and the Gates Foundation through the
University of Colorado at Denver, addressed these issues. The ultimate goal of these agencies is
to improve people’s lives through sanitation improvements in developing countries and to
provide a renewable energy source at a low cost.
To try and achieve these goals, four different MFC designs were pilot tested in different physical
environments. The project approach was to incorporate the Appraisal-Design-Intervention-
Monitoring & Evaluation development principles. These principles are a cyclic process in which
information is continually being evaluated and adjustments are made to the project to help it
succeed in the context of working within a developing community. The different designs were
either tested in a toilet comprised mostly of liquid or solids. All four designs were constructed
with locally purchased materials. The goal of generating renewable energy was simplified to the
level of generating enough power to visibly demonstrate the technology works and then start
redesigning the MFC’s to increase power output. One design placed in a septic tank produced
enough power to make a small light blink. This was considered a success because concepts
discovered in laboratory were proven to work in the field. That coupled with recent advances in
the laboratory increasing power output leads to the next phase of research, designing a self
contain MFC that produces more power. The pilot tests were started in June 2012 and are
ongoing with support from local community members and Water for People staff.
Future work will involve creating a prototype that can meet the demands of a septic tank
environment and increase the power output. Investigation of potential commercial markets also
needs researching. These issues are currently being worked on to understand the potential and
ii

limits of MFC technology placed in an environment with a need for a small amount of renewable
energy.
iii

Contents
Project Background ....................................................................................................................................... 1
iv
Appraisal/Analysis Phase .......................................................................................................................... 4
Community Descriptions ...................................................................................................................... 4
Strategy and Design ...................................................................................................................................... 7
Project Objectives ..................................................................................................................................... 7
Description of Project Activities ............................................................................................................... 8
MFC Designs ............................................................................................................................................ 9
Control Design .................................................................................................................................... 10
Septic Design ...................................................................................................................................... 10
Drum Inside a Drum Design ............................................................................................................... 10
Pour-n-Flush Design ........................................................................................................................... 11
Pit Latrine Design ............................................................................................................................... 11
Costs ........................................................................................................................................................ 12
Monitoring and Evaluation ......................................................................................................................... 12
Control Design for Quality Control and Assurance ................................................................................ 13
Septic Design .......................................................................................................................................... 15
Drum Inside a Drum Design ................................................................................................................... 16
Pour-n-Flush Design ............................................................................................................................... 16
Pit Latrine Design ................................................................................................................................... 17
Project Exit Strategy ............................................................................................................................... 18
Key Findings ............................................................................................................................................... 18
Lessons Learned.......................................................................................................................................... 18
Conclusions ................................................................................................................................................. 19
Recommendations ....................................................................................................................................... 20
Authors Notes ............................................................................................................................................. 21
Bibliography ............................................................................................................................................... 22

Tables
Table 1: Stakeholders……………………….…………………………………………………………..….5
Table 2: Problems and Solutions…………………………………………………………..………...……..6
Table 3: Logical Framework…………..………………………………………………………………..….7
Table 4: MFC's Design Costs (in US dollars)……………………………………………………………..12
Table 5: Typical Wastewater Characteristics………………………………….…………………………..14
Table 6: Control Designs Results………………………………………………………………………….15
Table 7: Septic Design Results……………...………………………………………………………....….16
Table 8: Pour-n-Flush Design Results………………………………………………………………….....17
Figures
Figure 1: MFC Schematic (Logan B. , 2008) ............................................................................................... 1
Figure 2: Pit Latrine on left; Pour-n-Flush on Right (Harvey, Baghri, & Reed, 2002) ................................ 5
Figure 3: Septic Design Laboratory Results ............................................................................................... 13
Appendix A: Photographic Log
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Project Background
Harvesting the electrons and protons released by microbes as they degrade waste to generate
electricity is a largely untapped renewable energy source. Currently, researchers are investigating
ways to reap the energy with no power input. They have shown this can be accomplished using
microbial fuel cells (MFC) to capture energy and convert it to useful electricity. MFCs harvest
the protons and electrons released from microbes as they degrade organic carbon and convert the
energy into electricity. Microbes oxidize a substrate (carbon in human waste) and convert it to
CO2 or methane. Human waste contains approximately 23 MJ/kg per dry stool depending on diet
(Murphy, Wootton, & Jackson, 1993) which is approximately equal to the energy stored in coal
(Weststeijn, 2002). This amount of power can translate to one person being able to generate
approximately 25 Watts and a family of four, 100 Watts, which is enough energy to power a
small incandescent light bulb (Logan B. , 2008). Getting electrons to flow to an anode and
reacting with oxygen (electron receptor) and protons to flow to cathode is the premise behind the
technology as shown in Figure 1.
Figure 1: MFC Schematic (Logan B. , 2008)
Microbes transfer electrons exogeneously to an anode via different methods. For example,
conductive appendages called nanowires, discovered in 2005, transfer electrons, as does a
process called cell-surface transfer (Gorby & Yanina, 2006). Cell-surface transfer occurs when
1

the surface of a cell is physically in contact with any surface and bio-film growth on an anode is
ideal for electron transfer this way in MFCs. Certain bacteria such as Pseudomonas aeruginosa
found in wastewater can shuttle electrons from the cell to a physical surface such as an anode
using mediators which are essentially electron shuttles. This process is currently not well
understood. To gain the most advantage from these three processes, many different anode
materials have been studied. An anode that has a large surface area, is highly conductive and
porous, is non-corrosive, and has low internal resistance seems to be the most effective at
transferring electrons. The limiting factor in the production of electricity with MFC technology
on a large scale currently is not the anode, but the design and material used for the cathode.
The chemical reaction that occurs at or on the cathode is a three phase reaction between a
catalyst, water, and oxygen, shown in equation 1.
2
O2(g) + 4H + + 4e - = 2H2O eq (1)
The free energy released during this reaction can be harvested in the form of electricity. The
electricity generated is in the form of direct current (DC). The cathode material acts as the
catalyst, lowering the activation energy required to make the reaction rate increase. Platinum is
frequently used as a catalyst, but is very expensive and subject to sulfide poisoning from
wastewater and therefore prohibitive for large scale applications (Feguia, et al., 2007). Chemical
oxidizers such as ferricyanide have been used as the oxidizing agent in cathode chambers,
producing some of the highest energy outputs, but ferricyanide needs to be replenished because it
is converted to ferrocyanide. Overcoming obstacles like these has led researchers to try to find
efficient cathode materials and designs that utilize oxygen as the oxidizing agent, since there is a
free, unlimited supply and because oxygen has a high oxidation potential. However, oxygen has
limitations as well as benefits—for example, it requires a high activation energy to be oxidized to
water and it can never exceed saturation dissolved in water (7.8 mg/l at 25°C) since the cathode
needs to be covered by a liquid to allow for proton transfer (Liu, Ramnarayanan, & Logan,
2004). Additionally, oxygen reduction requires high activation energy, which leads to
overpotential (difference between open and closed circuit potentials), thus limiting the transfer of
electrons.
To create an environment that can harvest the energy and overcome the limiting factors of
electron transfer, scientists are experimenting with many different MFC designs. The

architecture of MFCs’ is currently changing to become more efficient, but most are either a dual
or single chamber reactor.
The dual chamber reactor consists of an anode chamber containing the substrate and microbes
and a cathode chamber containing an oxidizing agent (dissolved oxygen) and the cathode. They
are divided by a cation exchange membrane (CEM), which allows protons to move between the
two chambers, but restricts the exchange of the media. A single chamber reactor consists of an
anode separated from the cathode only by distance in the media they are placed as opposed to
dual chamber design which has a membrane separating the chambers. This limits the cathode to
only utilize oxygen as the oxidant. Before treatment, raw wastewater contains an abundance of
organic carbon and microbes, which makes MFC technology a promising solution for a
renewable energy system. Several variations of the single chamber designs were installed in two
different environments within Kampala, Uganda as part of this project.
The project was conducted with collaboration from the Gates Foundation who awarded the
University of Colorado at Denver grant/research money as part of their grand challenge to
reinvent the toilet. The Mortenson Center at the University of Colorado at Boulder funded travel
expenses and the Water for People (WFP) field office located in Kampala, Uganda provided
community introductions and appraisal, technical and financial support, and field testing
facilities. Pilot test were conducted between June 13 and July 18, 2012.
The pilot tests were conducted in two different environments. The first was a secure easy to
access environment where a high level of control over the tests could be maintained. The second
testing area was located in a low income developing neighborhood within Kampala. The pilot
tests conducted within the neighborhood were designed to incorporate the project plan of
Appraisal/Analysis- Design/ Strategy-Intervention-Monitoring & Evaluation (ADIME)
development framework. The ADIME framework is a cyclic process. Information gathered
during each stage is evaluated and the cause and effects are incorporated back into the project
cycle. In this way adjusts can be made to the project to navigate obstacles and the project can be
sustainable. The initial stage of the project was to indentify a community that could potential
benefit from the technology and had the capacity to help implement the pilot tests. WFP, a non-
3

governmental organization with strong ties in Kampala, located the community and helped with
this initial stage.
Appraisal/Analysis Phase
Prior to the implementation of the project, discussions were held with WFP identifying possible
locations for the pilot tests. One site was identified behind the office of WFP where the pilot tests
could be conducted in a very controlled field environment and the second site was a developing
low income neighborhood in Kampala. The neighborhood was identified by WFP who had
previously worked in this community and had conducted a community appraisal.
Community Descriptions
Pilot tests were conducted in Kampala, Uganda either behind the Water for People office in the
Kitante section of the city or in the Nsambya neighborhood. Kitante is near the Kampala city
center and, in addition to the WFP office, also hosts the British High Commission, Uganda
National Museum and the Rwandese Embassy. The WFP office consists of an office building
serving nine people. Public water is supplied and the sanitation consists of two indoor toilets
which when flushed flow to a septic tank before entering the public sewer system.
4
The Nsambya neighborhood is located approximately three miles south-southeast of the central
business district. The neighborhood is located at the bottom of a hill built in an area with a very
high water table. Portions of the neighborhood are wetlands. There is access to metered private
water taps and several unprotected springs. There is no public sanitation and people use family or
community owned pit latrines and/or pour-n-flush toilets. Figure 2 shows designs of both the pit

2002)
latrine and pour-n-flush toilets.
Figure 2: Pit Latrine on left; Pour-n-Flush on Right (Harvey, Baghri, & Reed,
Sewer water (black water) that leak from the pit latrines and/or pour-n-flush toilets flows through
open channels into the wetlands. Unemployment and population density are high in Nsambya.
Schools are located within the community and the most common forms of transportation are
private car or motorcycles for hire.
The project stakeholders within Nsambya are shown in Table 1.
Table 1: Stakeholders
Stakeholders Contribution Stake
Chief of Defense- Waliggo
Joseph
Local Artisan- Isaac
Namakoola
Community leader who is a
government official. The
community defers to him to
resolve issues and he is very
familiar with families and the
living conditions. He is able to
provide suggestions to which
families or compounds may
provide the best test locations.
Highest local government
official and by giving his
approval to a location
increased his perception of
power.
Help install pilot test Reputation within the
community as a successful
artisan. Potentially lead to
5

Informal Leader- Sam Nangoli Locating families with ideal
test locations and navigation
through the neighborhood and
6
making introductions
Water For People Stays actively involved in the
community. Can be utilized
for many different resources
more employment
opportunities and he hires
from within the community.
Currently viewed by other
members of the community as
a forward thinker and helps
solidify his position
Continues their relationship
and gains more good will in
the community.
Property Manager-Moses Keeps the pilot tests running Gains more respect from the
families that share the latrines
and will be utilized for next
phase of testing.
The pilot tests had several obstacles to navigate. Some problems were identified by WFP after
the community appraisal, but others were identified after an initial site walk through the
community. Solutions were developed and applied to the project. The problems and solution are
listed in Table 2.
Table 2: Problems and Solutions
Problem Problem Detail Solution
Find Locally Sourced Material To meet the philosophy of the
funder the pilot tests needed to
be constructed of local
obtained material
Find Ideal Test Sites Personal or communities
bathrooms needed to meet
criteria of the pilot tests
specifications.
Correct Bathroom Use Urine need to be poured down
the cathode for aeration.
Education of Equipment Use People needed to understand
the system in order to care and
monitor the pilot tests.
Test Monitoring Understand the measurements
and how they are collected
Continuation of Project Having the pilots test continue
after oversight leaves.
Employed the help of a local
welder to secure material and
identify businesses selling the
required items
Utilize Chief of Defense and
informal leader to identify
ideal test sites
Hold a couple behavior
training classes with the
participating people and place
signs next to cathode in native
language
Hold training succession
Make it part of the education
and training process
Keep the communication
channels open and frequently
verbally reach out.

Strategy and Design
Project Objectives
The objective of the project was to build MFC’s from locally sourced material and to generate a
measurable amount of electricity from the system. The overall strategy of the project and
indicators of project success are indentified in Table 3. Table is a logical framework of the
project goals and ultimately the indicators tying together all the components of the project.
Table 3: Logical Framework
Goals Objectives Outputs Activities Inputs Indicators
Generate a
measurable
amount of
electricity
using MFC
Technology
placed in
human waste
Use only
material
found locally
Track system
costs
Locate a
control
environment
to test MFC
Locate a
community
environment
to test MFC
Gage
community
Interest in
Technology
Build MFC Search
markets and
incorporate
local people
with
specialized
Know what a
complete
system would
cost
Safe and easy
to monitor
pilot tests site
Real world
system
testing in a
family or
community
toilets
People stating
they would
pay for a
system that
knowledge
Buy only
local material
Investigate
the area and
physical
observe the
site
Identify a
community
and/or family
with the
capacity to
support the
pilot test
Walk through
neighborhood
identifying
how many
Supply
necessary
transportation
and funds
Money to buy
material
Discuss
options with
WFP who has
local
knowledge
Community
appraisal and
meet with
individual pit
latrine owners.
Introductions
made by
informal
leader
Provide an
overview of
what the
technology can
Completely
built system
Everything
was
purchased
locally and
system cost
could be
evaluated
24 hour
security and
easy access to
septic tank
and other
project
necessities
Toilets can
house pilot
test
equipment
and on-site
monitoring is
being
completed
Public
support and
long-term
interest in the
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8
can supply
inexpensive
electricity
Description of Project Activities
places are
without
access to
electricity
do through
visual and
verbal
demonstrations
Two general MFC concepts were explored. The first concept was to build MFC’s to take
test indicated
by
involvement
and
monitoring
advantage of the liquid environment found in a waste tank which is predominately liquid with
solids at the bottom. The mass transfer of electrons and protons are more efficient in a liquid
medium and the solids at the bottom of the tank provide for an anaerobic environment that is
favorable for microbes to release the largest amount of electrons. The second design concept was
to build an MFC in a pit latrine comprised mostly of solids. An environment comprised of
mostly solids makes it more challenging to get the mass transfer needed to generate sufficient
electricity, but has the capacity of producing greater amounts of energy since the human solid
waste provides a larger carbon source for microbes. Different MFC designs were created to
explore the feasibility of the technology and were monitored to evaluate their performance and
maximize voltage output.
Suitable test sites were found that provided these two different latrine environments. The secure
environment behind WFP office was chosen as one of the test sites because of 24 hour security
and ease of access to the onsite septic tank. This site also provided an environment that was easy
to monitor. For these reasons a control experiment was constructed to mimic MFC’s created in
the University of Colorado Denver laboratory at the WFP office. The ease of access and control
made it ideal to test different MFC material. The second test location was located in Nsambya
where the community was more reflective of the people that would be targeted for this
technology if a market solution was determined to be feasible. Selections of sites in Nsambya
were made after going through a community evaluation.
Before selecting test sites in Nsambya, a local artisan named Isaac Namakoola was recommend
by WFP to provide introductions to the community. The artisan understood the community
dynamics and who the stakeholders were that could help achieve the goals of the project. He
introductions to informal community leader Sam Nangoli who became crucial in finding

potential sites because of his knowledge of the community and family structures that used the
different latrines. He made introductions to the Chief of Community Defense Waliggo Joseph,
who was one of the community’s most respect members. The Chief of Community Defense was
very interested in the project and suggested several locations. Based upon the needs of the
project, Isaac Namakoola, Sam Nangoli and Waliggo Joseph discussed potential sites and
interviewed the owners of various toilets, gauging interest and compatibility to the two design
concepts. Three test sites were chosen in Nsambya. Once the sites where chosen, materials
needed to construct the MFC’s were located.
A local welder, Moses Ndagirira, helped locate and negotiate prices of stainless steel used for the
anode and cathode and for some of the plumbing fittings. Stainless steel required the most time
to locate. Stainless steel plates were used instead of stainless steel mesh since it could not be
found in local markets. The rest of the materials were obtained in varies local markets. By
buying locally, the MFC’s cost could be tracked and evaluated for the Kampala market
specifically.
MFC Designs
The single chamber MFCs were varied towards the goal of maximizing power output. The
different designs were adopted for the two different environmental settings (mostly liquid and
mostly solid septic environments). The following four designs were used and are described in
more detail in following sections.
• A control design,
• A septic design,
• A drum inside a drum design
• A pour-n-flush design and,
• A pit latrine design
A Hewlett Packer E2377A multimeter was used to collect voltage readings. Readings were taken
and recorded across resistors and an open circuit.
9

Control Design
A control design was built and placed behind the WFP office. The goals of the control design
were to mimicking the laboratory experiment which was successful at generating power over an
extended period of time (greater than 4 weeks). The design consisted of two different
experiments. One design was identical to that which was used in the laboratory at CU Denver,
which used stainless steel mesh as the anode and cathode. A second control was designed
identical to the first, but a different anode and cathode material mimicking the pilot tests. The
second design used stainless steel plating purchased locally instead of stainless steel mesh as the
anode and cathode. The anode and cathode were placed in 3 gallon plastic buckets containing
wastewater collected from the septic tank behind WFP. The anode was placed at the bottom of
the buckets and the cathode was half submerged. The anodes and cathodes were clipped to 1000
ohm (Ω) resistors. Photographs 1 and 2 in Appendix A show this design.
Septic Design
A MFC was built to try and take advantage of the mostly liquid environment inherit to septic
tanks. Two 5 x 10 foot pieces of common steel mesh window screening was used as the anode.
They were rolled length-wise and attached side by side. Several bricks were placed inside the
rolls to weight them down before they were placed in the bottom of the septic tank. The anode
was pushed into a layer of solids at the bottom of the tank. This solids layer at the bottom
provides a mostly anaerobic environment favored by microbes that produce the most electricity.
The anode rested approximately 4 feet below the water surface. The cathode consisted of a 1 x
1.25 foot piece of #40 stainless steel mesh coiled around a piece of packing bubble wrap. The
bubble wrap gave the cathode buoyancy and keep it on the surface of the wastewater. The anode
and cathode were clipped to a 50 Ω resistor. Photographs 3 and 4 in Appendix A show this
design.
Drum Inside a Drum Design
A drum inside a drum design was created to evaluate if sludge emptied from a pit latrine could
be utilized as a viable energy source when stored away from the pit. This design helped evaluate
the efficiency of mass transfer through solids. A perforated 30 gallon drum was placed inside a
55 gallon plastic drum containing two drainage spouts, one near the bottom and the other
approximately 18 inches up from the bottom. The spouts were installed to change the water level
10

etween the two drum thus effectively changing the ratio of cathode exposed to air and water.
The inner, smaller drum used both stainless steel plate and steel window mesh as anode material.
The cathode consisted of steel window screening placed between the two drums. A four gallon
plastic jug referred to as a “jerrican” was placed on top of the outer drum filled with water. The
water, substituting for urine, was trickled over the cathode to increase dissolved oxygen levels in
the water trapped between the drums. Oxygen acts as an electron acceptor in the reaction needed
to generate electricity. The inner drum was filled with pit latrine sludge collected by a local
sludge pumping and hauling company. The drum inside a drum MFC was placed behind the
Water for Peoples office. Photographs 5 through 9 in Appendix A show this design.
Pour-n-Flush Design
A pour-n-flush latrine located in Nsambya which serviced approximately 15 people was chosen
to test the stainless steel plates in a liquid environment. Two 16 x 16 inch stainless steel plates
were used for the anode and cathode. The anode was placed approximately four feet below the
water surface in the solids at the bottom of the tank. The cathode floated on the surface, made
buoyant by attaching several empty plastic water bottles. The anode and cathode were clipped to
a 100 Ω resistor. The design is presented in Appendix A, photographs 10 through 12. A video of
the design can be viewed at https://vimeo.com/50475418 (Password: moses).
Pit Latrine Design
Two different pit latrines in Nsambya were used to test designs placed in solids. Due to the
limited volume of solids in the first pit, the first site was abandoned. The material from the first
pit latrine was moved and installed in another pit latrine that serviced several homes with 3
separate stalls filling one pit. The anode consisted of a stainless steel 16 x 16 inch plate wrapped
with by piece of steel window screening to add extra surface area. The anode was pushed several
feet into the solids approximately 5 feet below the surface. The cathode was constructed using
steel window mesh placed inside a 5.5 foot perforated 4 inch PVC Schedule 20 pipe. The pipe
containing the cathode was then pushed into the solids leave the upper portion exposed to air. A
jerrican was suspended above the cathode and urine collected in bottles at night by the users of
the latrine was added to the jerrican which tricked it over the cathode surface. This increases the
cathode exposure to dissolved oxygen. Photographs 13 through 16 in Appendix A show the
design.
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Costs and Construction Time
Materials that were used to construct the MFC’s were purchased locally with the assistance of
community members. Table 4 shows the associated costs of each design. ‘Miscellaneous’
includes zip ties, silicone caulking, jerrican and tubing.
Construction of the MFC’s varied between the designs. General all the designs took less than 2
hours to construct once the material had been acquired except for the drum-n-drum. The drum-n-
drum design took approximately 8 hours to construct since the inner drum needed to have
perforations cut into it.
Table 4: MFC's Design Costs (in US dollars, one unit per item)
Items Septic Design Drum-n-Drum Pour-n-Flush Pit Latrine
Anode $13 $7 $13 $13
Cathode $6 $7 $13 $6
Wire $1 $1 $1 $1
PVC Pipe --- --- --- $6
Drums --- $74 --- ---
Miscellaneous $1 $4 $1 $4
Total $21 $93 $28 $30
Monitoring and Evaluation
The monitoring of the project was performed by several people. In the beginning it was a group
effort as training was necessary to ensure the data was collected the same way by all parties. As
the project progressed the monitoring of the project was continued by WFP and the property
manager. Currently the project is just being monitored by the property manager who reports the
findings back to the Project Manager in the USA. Below is a list the defined roles.
12
• Project Manager – Help supply technical support, training and initial oversight, and data
collection and analysis.
• WFP – Help collect data and communicate results to Project Manager
• Property Manager – Collect the data and report results to WFP or to the Project Manager.

The data currently is still being collected and will be used to determine if the project should
continue to the next phase. The next phase is product development. Results of the study are
discussed below.
Control Design for Quality Control and Assurance
In the laboratory at the University of Colorado Denver a stainless steel mesh anode and cathode
were placed in a bucket of municipal wastewater. Over a 25 days period, the millivolts (mV)
measured across a 1000 Ω resistor varied depending on the biofilm that accumulated on the
cathode as shown in Figure 3. Laboratory results indicated that if oxygen was available to
contact the cathode sustained voltage could be maintained at approximately 200 mV.
Figure 3: Septic Design Laboratory Results
The municipal wastewater used in the laboratory control experiment is much more diluted than
wastewater in a septic or holding tank. Table 5 shows the different ranges of concentrations
between municipal and septic wastewater. Chemical oxygen demand (COD) is a good indicator
13

of the amount of “food” available to be consumed by the microbes. Septic sewage has
considerable higher COD content than municipal sewage. Therefore, septic sewage provides an
ideal environment for microbes to release electrons as they consume the substrate increasing the
potential to generate power. A problem using septic sewage is that if household cleaners are
disposed of into the septic tank. Their concentrations are much higher than in dilute municipal
wastewater. Household cleaners contain antibacterial pesticides and therefore can reduce the
microbe population. These compounds were used at unknown concentrations in the control
testing site behind the WFP office. According to a survey of the people who used the field
latrines, cleaners were not disposed of in the holding tanks.
Table 5: Typical Wastewater Characteristics- Adapted from Metcalf and Eddy (Tchobanoglous,
Burton, & David, 1991)
14
Septic Wastewater Municipal
Constituent
Wastewater
Range (mg/l) Typical (mg/l) Range (mg/l)
Total Solids (TS) 50,000-100,000 40,000 350-1,200
Suspended Solids (SS) 4,000-100,000 15,000 100-300
Chemical Oxygen
Demand (COD)
5,000-80,000 30,000 250-1,000
BOD5 at 20°C 2,000-30,000 6,000 110-400
Ammonia 100-800 400 15-50
Total Phosphorous 50-800 250 4-15
Total Nitrogen 100-1,600 700 20-85
The control test setup behind the WFP people office was designed to mimic the experiment done
in the laboratory using wastewater from the septic tank. Stainless steel mesh was used as anode
and cathode material in one bucket and stainless steel plate into the other bucket. The anode and
cathode in each bucket were clipped to 1000 Ω resistors exactly like the lab experiment. Results
are shown in Table 6.

Table 6: Control Designs Results
Date Stainless Steel Mesh (mV) Stainless Steel Plate (mV)
1000 Ω Open Circuit
Potential
July 3, 2012 Start Date
1000 Ω Open Circuit
Potential
July 5, 2012 33.5 92.3 15.4 93.7
July 9, 2012 37.9 75.7 35.2 210.3
July 10, 2012 37.9 75.7 49.0 199.0
July 11, 2012 80.0 197.0 40.0 212.3
July 12, 2012 62.9 162.6 66.6 213.8
July 14, 2012 99.3 238.3 56.6 202.7
July 16, 2012 101.4 296.1 57.3 256.2
Results from the two control setups were lower than the laboratory results, but this is to be
expected as the microbial population requires time to assimilate and increase, which we were
unable to fully achieve in the field. The voltage, however, was steadily increasing as more time
passed, leading us to believe that it would have reached a similar output as seen in the UC
Denver lab experiments, given more time. This system was shut down in the beginning of
August since both materials demonstrated that electricity could be generated.
Septic Design
The septic design MFC with a large anode surface area and having time for the microbial
population assimilate produced the most voltage compared to all the other designs. The results of
the septic design are shown in Table 7. The design generated enough voltage to make a small
light blink as shown in this video https://vimeo.com/50330023. (Password: kampala).
15

16
Table 7: Septic Design Results
Date Stainless Steel Mesh/Steel Mesh
(mV)
50 Ω Open Circuit
July 9, 2012 Start Date
Potential
July 9, 2012 570
July 10, 2012 394 394
July 11, 2012 394 394
July 12, 2012 246.2 246.4
July 14, 2012 237.9 238.3
July 16, 2012 168.7 183.2
The amount of power generated in the septic design has potential to charge a cell phone over
time. Currently commercial venders in market places will charge a cell phone for the customer
for approximately $0.25 USD. A typical phone battery stores approximately 1000mAh (Vernon,
2007). At power densities produced from this MFC design, a cell phone could be charged in
approximately 6 hours. Based upon the costs of this design ($21) as shown in Table 4, a user
could recoup their investment in fewer than 100 phone battery charges. MFC’s in septic tanks
can provide people living off the grid an opportunity to charge their cell phones without going to
the market place.
Drum Inside a Drum Design
The drum inside the drum design was built at the end of the pilot test program. Therefore, no
data has yet been collected. WFP has currently hired several engineers who will work on getting
this MFC running and will monitor the efficiency once it is working. The data will then be
evaluated toward the feasibility assessment of this design.
Pour-n-Flush Design
The pour-n-flush design had numerous troubles even though the liquid environment was ideal to
produce electricity. The cathode was readjusted several times due to wastes being deposited

directly on the cathode. When the cathode was moved from within the tank the voltage reading
would instantly increase above 150 mV, but would then steadily decrease and stabilize at very
low values. The system is currently still being analyzed by WFP personnel and the problems are
trying to be resolved. Table 8 presents the results of the pour-n-flush design. The property
manager who lives on site has continued to assist in maintaining the MFC.
Pit Latrine Design
Table 8: Pour-n-Flush Design Results
Date Both Stainless Steel Plate (mV)
100 Ω Open Circuit
July 9, 2012 Re-start Date
Potential
July 9, 2012 21.7 44.0
July 10, 2012 6.7 6.8
July 11, 2012 12.3 30.0
July 12, 2012 Re-start Date
Two different pit latrines in Nsambya were used to test designs. The first was abandoned after it
was determined that the layer of solids was not thick enough. The pit latrine serviced a family of
five, but because of its lack of privacy it was not used often. Voltage at this location never
exceeded 25 mV. The second pit latrine serviced several homes with three separate stalls filling
one pit. This MFC was installed at the end of pilot test program, but monitoring by WFP has
continued. On September 5, 2012 the open circuit potential was measured at 76 mV and 20 mV
across the 100 Ω resistors. Monitoring of this location will continue especially since there is a
local technician, John Paul Caweg very interested in the technology and continues to contact
WFP, interested in the results. Users of these three pit latrines continue to fill the jerrican with
urine, displaying public interest. This interest has continued to make this location sustainable.
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Project Exit Strategy
The project has a lifespan and currently is expected to be terminated before the end of the year.
The exit strategy is to have the equipment removed from the waste systems and cleaned. The
property manager has been notified that he can resell the stainless steel.
Key Findings
Comparing the results of the different MFC configurations showed that the MFC placed in the
septic system behind WFP’s office produced the best results. The ability to get a light to blink
and show people the visual results that the technology can and does work was key to the
project’s success. Having people actually see the light blinking made believers of the people who
witnessed it. That was stronger evidence than taken readings with the multimeter.
Systems placed in an environment mainly consisting of solids such pit latrines were the hardest
to get working since the mass transfer of electron and protons through the waste is a limiting
factor.
Based upon the community members continuing to fill the jerrican with urine months after the
pilot test began and with very little interaction from outside organizations is a strong indicator of
public interest in the technology and acceptance. Monitoring the systems in the future will reveal
whether public interest is maintained.
Lessons Learned
Evaluating the project can be broken into two sections. Lesson learned from the research and
lesson learned from working within a developing community. The key things learned from the
research are as follows;
18
• Locally sourced material is not easy to obtain and it can vary from region to region or
country to country.
• Cleaning products in wastewater can harm the microbial population thus limiting the
voltage output.

• People in the lower income areas would be interested in the technology judging by the
questions they asked and their diligence to helping make the MFC’s work.
• MFC designed to tap the energy from latrines comprised mainly of solids currently do not
produce enough voltage and will need to be redesigned.
Lessons learned from working within a developing community are more far ranging in
complexity because they involve people. Applying the ADIME principles to the project helps
keep a project on task, but not all problems have simple answers or solutions. Lesson learned
from my practicum are as follows;
• People’s enthusiasm has highs and lows. These peaks and valleys affect the quality of the
project. In the beginning everyone wants to be involved, but as time goes on the project
no longer has the luster of “newest” and the quality of the work diminishes. When I
would return to the sites, people would get all reenergized for another short period of
time, but the intensity would eventually drop off. This can play a major role in how
sustainable the project is.
• After holding behavior training regarding dumping their night urine into the jerricans, I
was amazed at how the participates followed through. Every time I checked the pilot
tests, there was urine in the jerricans. It showed to me a level of commitment and that the
success of the project did matter to them. The behavioral training had worked.
• Using the informal leader and Chief of Defense was very helpful in picking the site
locations. They directed me to people that were highly motivated and interested. This
helped with the success of the project.
• Having an exit strategy and time deadline helps bring closure to the project. This is
important because I could relay this to the property manager. He understands it will not
be an ongoing long-term test and therefore knows his “duties” will come to an end.
Conclusions
MFC’s can provide an inexpensive renewable source of energy. Utilizing and harvesting the
energy from the natural degradation of human waste by microbes is a feasible concept. MFC
designs were tested in different environments to evaluate their performance. MFC’s placed in a
liquid environment generated more voltage than those that were placed in an environment
19

comprised mostly of solids. This was evident by the voltage recorded with the multimeter. The
fact that the septic design produced enough voltage to make a small light blink is considered a
success since this design can be expanded upon. The cost of a MFC system placed in the septic
tank was slightly over $20 USD and if power output can be increased with modifications to the
design then people could have access to an inexpensive power source. The power generated can
provide light in the bathroom area or possibly charge a cell phone. Public interest in the
technology seems to be high, but further research needs to be done to validate this theory.
Recommendations
The pilot tests are currently still setup in the different environments and settings. Therefore, with
the assistance of WFP and support from people in the community of Nsambya, it is
recommended to continue monitoring of systems by occasionally taken voltage reading. This
enables the evaluation of the technology as the microbe communities mature. The following
changes should also be considered for the different MFC designs;
20
• The use of inexpensive Chinese made carbon brushes as anode and cathode material.
Carbon brushes have a large surface area creating a greater contact area with the
microbes to transmit electrons. In the lab they generate more electricity than stainless
steel. They are also cheaper than stainless steel when purchased from overseas
companies.
• Design and build a self-contained prototype MFC to work in a liquid environment. This
will help keep parts of the MFC from being damaged as they exit the pit or from things
landing onto of them.
• Start the process of evaluating whether a market exists for the technology and if so the
associated price point. This will help designers to know the market and material needed
to target the right price point if there is one. Using information gathered during the
monitoring and evaluation phase would help in this analysis. The stakeholder WFP could
play a significant role in this process.
• Approach funders and investors with the concept to help offset costs.

Authors Notes
I took the perspective of my experience in Peace Corps with me to the practicum in Uganda. I
had served in South Africa and it was not an overall positive experience. While there, I did learn
a lot about what made projects successful and unsuccessful, but it took SCD I and SCD II to put
it in some context. Once I learned the ASIME frame work, I could correlate it much better to
what I had seen and learned. Using my past experience and the new tools, I found it much easier
to adapt my project/practicum to hurdle obstacles. The use of behavior change training worked
much better than I expected (people actually filled the jerricans with urine) and the community
appraisal information helped me navigate some obstacles. Specifically it identified key
stakeholders whom I utilized to direct me to the best test sites giving the project the greatest
chance for success. A highlight of the practicum was doing several community walks and talking
with the people. These walks gave me insight into their lives as well as being able to gauge
interest in the technology. I thoroughly enjoyed my experience in Kampala working with WFP
and the people in the community. The video I made of the pour-n-flush system is just a small
glimpse at what I encountered. The different motorcycle taxis guys that I rode with to the pilot
test were just as wonderful and curious as the people in the community. The questions everyone
asked me, gave me pleasure in explaining simple science principles. Hopefully I got some people
thinking about the physical world. I was there for just under five weeks and wished I could have
had another five weeks. I was given all the latitude I wanted to interact with the community and
make the project successful from my own point of view. I feel the community embraced me and
was helpful in working to achieve the project goals. Like Peace Corps, I felt I got more out of the
experience than I gave. Having the SCD education prior to my Peace Corps experience would
have been very valuable. My practicum was a much better experience than Peace Corps,
unfortunately it was shorter.
21

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