Team 18
Project Proposal and Feasibility Study
Austin Kearby
Mitchell Porch
Lucas Schreiber
Trevor Sherman
Engineering 339/340: Senior Design Project
Calvin College
11 December 2015
Copyright © 2015, Calvin College, Austin Kearby, Mitchell Porch, Lucas Schreiber, and Trevor Sherman
Executive Summary
Team Kinyesi will design and construct a prototype of an anaerobic digester for Tanzania Grace Bible
Institute (TGBI) located in southwestern Tanzania. Currently, TGBI prepares food for its students using
wood that is collected from the surrounding land. However, wood is a diminishing resource in the area
due to trees being continually cut down. Consequently, the college is interested in an alternate way of
fueling their cooking process. The compound currently has a pig barn where they raise between 90 and
150 Landrace pigs. The college raises these pigs to be sold as a source of income that supplements each
student’s tuition. The waste from the pigs is currently dried and used for fertilizer.
Team Kinyesi recommends collecting the pig waste into an anaerobic digester where the volatile solids
are broken down by bacteria already in the manure. The product of this decomposition is biogas that is
composed of approximately 60% methane and 40% carbon dioxide along with trace amounts of other
gases. The most notable of these trace gases is hydrogen sulfide (H2S), which can cause serious health
problems at high concentrations. Still, this biogas can be used as a fuel for cooking for the students on the
TGBI campus. This reuse of available resources would further reduce the cost for the students and protect
the environment. Along with the digestion of pig manure, Team Kinyesi is pursuing adding human waste
to the digester from some latrines on campus. The addition of human waste is mainly for sanitation
purposes as human waste does not generate significant amounts of biogas.
Team Kinyesi has personal connections to the staff located on the TGBI campus. One of the founders of
the institute, Steven Sherman, is currently living in the United States. Therefore, there are opportunities to
ask him questions regarding the situation on the ground at TGBI. Mike Caraway is available on campus
to collect specific measurements, distances, and elevations.
The prototype will be built here in the United States to affirm the research, theoretical designs, and
calculations made by the team. There are two main goals in regards to the prototype. The first goal is to
prove that the process is possible and to test the kinetics of the system. The second goal is to build a
scaled down replica of the recommended design presented to TGBI. The second goal is helpful to provide
adequate construction recommendations; however, due to cost constraints and availability of materials in
Tanzania compared to Grand Rapids, there will be certain differences between the scaled model and the
final design. Still, the prototype will be critical to making the final design decisions. This Project Proposal
and Feasibility Study investigates design alternatives, design norms, project criteria, and project goals,
providing a preliminary digester design and an affirmation of the feasibility of the project.
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Table of Contents
Executive Summary ....................................................................................................................................... i Table of Figures ........................................................................................................................................... iv Table of Tables ............................................................................................................................................. v 1. Introduction ............................................................................................................................................... 1 1.1 Senior Design Background ..................................................................................................................... 1 1.1.1 Calvin Engineering Program ................................................................................................................ 1 1.1.2 Senior Design Class ............................................................................................................................. 1 1.1.3 Team Members .................................................................................................................................... 1 1.1.4 Team Advisors ..................................................................................................................................... 3 1.2 Project Background ................................................................................................................................. 3 1.2.1 Location: Tanzania Grace Bible Institute ............................................................................................ 3 1.2.2 Problem Definition............................................................................................................................... 5 1.2.3 The Client............................................................................................................................................. 6 1.2.4 The Project ........................................................................................................................................... 7 2. Project Management ................................................................................................................................. 7 2.1 Team Management.................................................................................................................................. 7 2.2 Scheduling............................................................................................................................................... 8 2.3 Budget ..................................................................................................................................................... 8 2.3.1 Senior Design Funds ............................................................................................................................ 8 2.3.2 Eric DeGroot Engineering Fund .......................................................................................................... 8 2.4 Method of Approach ............................................................................................................................... 9 3. Project Overview ...................................................................................................................................... 9 3.1 Objectives ............................................................................................................................................... 9 3.1.1 Provide a Full Scale Design and Operations Directions ...................................................................... 9 3.1.2 Develop and Build Prototype ............................................................................................................... 9 3.2 Requirements ........................................................................................................................................ 10 3.2.1 Minimal Maintenance System ........................................................................................................... 10 3.2.2 Provide Alternative Cooking Fuel ..................................................................................................... 10 3.2.3 Energy Efficiency .............................................................................................................................. 10 3.2.4 Effluent Quality ................................................................................................................................. 10 3.2.5 Cost .................................................................................................................................................... 11 3.3 Design Norms ....................................................................................................................................... 11 ii
3.3.1 Stewardship ........................................................................................................................................ 11 3.3.2 Trust ................................................................................................................................................... 11 3.3.3 Cultural Appropriateness ................................................................................................................... 11 3.4 Basic Design ......................................................................................................................................... 11 4. Research .................................................................................................................................................. 12 4.1 Anaerobic Digester Types..................................................................................................................... 12 4.1.1 Plug Flow ........................................................................................................................................... 12 4.1.2 Continuously Mixed Flow Reactors .................................................................................................. 12 4.1.3 Sequencing Batch Digester ................................................................................................................ 13 4.2 Microbiology of Biogas Production ...................................................................................................... 13 4.3 Effluent Quality .................................................................................................................................... 14 4.3.1 Destruction of Pathogens ................................................................................................................... 14 4.3.2 Nutrient Recovery in the Effluent ...................................................................................................... 15 4.3.3 Solids Consumption ........................................................................................................................... 15 4.3.4 Effluent Testing ................................................................................................................................. 15 4.4 Methane Heating ................................................................................................................................... 15 5. Design Factors ........................................................................................................................................ 15 5.1 Temperature .......................................................................................................................................... 15 5.2 Manure Characteristics ......................................................................................................................... 16 5.3 Hydraulic Retention Time..................................................................................................................... 16 5.4 Acidity .................................................................................................................................................. 16 5.5 Influent Loading Rate ........................................................................................................................... 17 5.6 Mixing ................................................................................................................................................... 17 5.7 Structural Shape .................................................................................................................................... 17 5.7.1 Cylindrical shape ............................................................................................................................... 17 5.7.2 Pill shape ............................................................................................................................................ 17 5.8 Digester Size ......................................................................................................................................... 18 6. Heating .................................................................................................................................................... 18 6.1 Required Heating .................................................................................................................................. 18 6.1.1 Temperature Requirements ................................................................................................................ 18 6.1.2 Thermal Properties ............................................................................................................................. 18 6.1.3 Heating Factors .................................................................................................................................. 18 6.2 Energy Sources ..................................................................................................................................... 19 6.2.1 Solar Heat Capture ............................................................................................................................. 19 6.2.2 Electricity from Hydroelectric Dam .................................................................................................. 19 iii
6.2.3 Biogas Feedback ................................................................................................................................ 19 6.3 Heating methods ................................................................................................................................... 20 6.3.1 Heat exchanger................................................................................................................................... 20 6.3.2 Induction Heating............................................................................................................................... 20 6.3.3 Heating Jacket .................................................................................................................................... 20 6.4 Cost Analysis of Available Energy Sources ......................................................................................... 20 6.4.1 Charcoal ............................................................................................................................................. 20 6.4.2 Dried Manure ..................................................................................................................................... 20 6.4.3 Solar Power ........................................................................................................................................ 20 6.4.4 Hydroelectric...................................................................................................................................... 20 7. Prototype ................................................................................................................................................. 21 7.1 Location of Construction ...................................................................................................................... 21 7.2 Source of Waste .................................................................................................................................... 22 7.3 Safety Plan ............................................................................................................................................ 22 7.3.1 Personal Protective Equipment PPE .................................................................................................. 23 7.3.2 Facility Requirements ........................................................................................................................ 23 7.4 Prototype Design ................................................................................................................................... 23 7.4.1 Control System................................................................................................................................... 25 7.4.2 Heating System .................................................................................................................................. 25 7.4.3 Prototype Heating Requirements ....................................................................................................... 26 7.4.4 Prototype Assembly and Testing Plan ............................................................................................... 26 7.5 Parameters to test .................................................................................................................................. 27 7.5.1 pH....................................................................................................................................................... 27 7.5.2 Temperature ....................................................................................................................................... 27 7.5.3 Influent Composition ......................................................................................................................... 27 7.5.4 Solids Consumption ........................................................................................................................... 27 7.5.5 Volume of Gas Produced ................................................................................................................... 27 7.6 Conclusion ............................................................................................................................................ 28 8. Acknowledgements ................................................................................................................................. 28 9. References ............................................................................................................................................... 30 Table of Figures
Figure 1. Team Kinyesi: Trevor Sherman, Austin Kearby, Mitchell Porch, and Lucas Schreiber (Photo
credit: Marissa Ritter) ................................................................................................................................... 2 Figure 2. Map of TGBI in the Context of Africa, Marked with the Star ...................................................... 4 iv
Figure 3. Map of TGBI in the Context of Southwestern Tanzania, Marked with the Star ........................... 4 Figure 4. Average Monthly Temperature in Mpwapwa, Tanzania ............................................................... 5 Figure 5. Desertification Vulnerability of Africa.......................................................................................... 6 Figure 6. Anaerobic Digester Model........................................................................................................... 12 Figure 7. Multi-step Nature of Anaerobic Digestion .................................................................................. 13 Figure 8. First Location Option for the Construction of the Prototype in the Ravenswood Shed. ............. 22 Figure 9. Inventor Model of Prototype Design ........................................................................................... 24 Figure 10. Isometric view of the Inventor Model ....................................................................................... 25 Figure 11. Flo-Wing Meter ......................................................................................................................... 28 Table of Tables
Table 1. Sizing Estimates Based on Research ............................................................................................ 18 Table 2. Induction Heating Cost Comparison ............................................................................................. 26 v
1. Introduction
1.1 Senior Design Background
1.1.1 Calvin Engineering Program
The Calvin College Engineering Program has been accredited by the Accreditation Board of Engineering
and Technology (ABET). The mission statement of the program is to “equip students to glorify God by
meeting the needs of the world with responsible and caring engineering.”1 This calling is evident in the
priorities that the program holds. The program seeks to train their students so that they are well prepared
to integrate their Christian faith while using their liberal arts background as they enter into the
professional realm. Furthermore, the program provides numerous opportunities to incorporate engineering
into the international context. There is a summer trip to Germany; interim trips to Europe, Cambodia,
China, Kenya, and Ethiopia; and projects that partner with a city in Peru. Technical ability is also a
priority as is evident by the educational objectives of the program. Those objectives are summed up in the
following statement: “The long term goal is for our graduates to become kingdom servants whose faith
leads them to lives of integrity and excellence, called to leadership with a prophetic voice advocating for
appropriate technologies.” 1
1.1.2 Senior Design Class
This design project is the main component of the capstone class for engineering students at Calvin
College. The class, Senior Design, is divided up between two semesters: ENGR 339 in the fall and ENGR
340 in the spring. The fall class is two credit hours and the spring class is four credit hours. The class is
comprised of time to work on the project, guest speakers, and in-class lectures. The topics focus more on
non-technical elements of the engineering career such as ethics, presenting, cost estimating, and working
with people. The focus of the fall semester is producing the product proposal and feasibility study. The
focus of the spring semester is to actually produce the project that was proposed in the fall. The purpose
of this project is to integrate the Christian faith with the technical skills learned throughout the
engineering program to produce a God honoring project that will also prepare students for their future
careers.
1.1.3 Team Members
The members of Team 18 are pictured in Figure 1. All of the team members are committed to using their
unique skills to reuse the available resources at Tanzania Grace Bible Institute (TGBI) in order to produce
cooking energy. More about each team member is presented below.
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Figure 1. Team Kinyesi: Trevor Sherman, Austin Kearby, Mitchell Porch, and Lucas Schreiber (Photo credit: Marissa Ritter)
Austin Kearby
Austin Kearby grew up in Nairobi, Kenya for 13 years. His family returned to Denver, Colorado after his
freshman year of high school. Austin is majoring in engineering with a civil/environmental concentration
and an international designation. He has long term goals of returning overseas to use engineering as a tool
for international development. His short term plans are to find a general civil job in the Grand Rapids
area. Austin has been a part of the Calvin Men’s Rugby team for all four years at Calvin. He was captain
of the team his junior year and is president of the team this year. In his free time, Austin also enjoys
playing soccer and spending time with friends.
Mitchell Porch
Mitchell Porch grew up in Guinea and Senegal before returning to Minneapolis, Minnesota after his
freshman year of high school. Mitchell is majoring in engineering with a civil/environmental
concentration. He has an entrepreneurial mindset and already has a small business. In his free time,
Mitchell likes making longboards, playing soccer and spikeball, and riding his motorcycle. He is
interested in possibly returning overseas to do engineering long term. Looking more short term, Mitchell
is searching out civil engineering positions across the nation, although he would prefer to remain in West
Michigan after graduation.
Lucas Schreiber
Lucas Schreiber was born in Wisconsin, but has moved a number of times across the United States,
finally ending up in Sacramento, California. In Sacramento, he worked for Waste Connections and
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attended Community College. Then Lucas came to Calvin College where he is majoring in engineering
with an electrical concentration and is pursuing a math minor. He is an active member in many student
groups and is interested in helping others in any way possible. His goal is to get a job in robotics or
aerospace in either Grand Rapids area or near Houston, Texas.
Trevor Sherman
Trevor Sherman grew up in southwestern Tanzania on the compound where TGBI is located. Trevor went
to high school in Kenya. He found an interest in engineering through an EMI project that installed a
hydroelectric dam on the river near to where he lived. Now he is in the civil/environmental engineering
program at Calvin. After seeing how an engineering project has helped a community in Africa, he has
long term goals of doing similar projects overseas. In his free time Trevor likes to play soccer and spend
time with friends.
1.1.4 Team Advisors
Throughout the year, professors of the engineering program at Calvin assist students in the project
process. Professor Robert Masselink is the advisor for Team 18. Professor Masselink is a retired civil
engineering who has 44 years of experience. Furthermore, each team has an industrial consultant who has
experience in the specific field of the project. Team 18 has partnered with Jeff Friesen, P.E. Mr. Friesen
currently works with power production for large digesters in Oregon. However, he spent a year on the
TGBI campus installing a hydroelectric dam. Professor David Wunder is another resource that the team
has been consulting as he has more specific experience in the area of anaerobic digestion.
1.2 Project Background
1.2.1 Location: Tanzania Grace Bible Institute
Tanzania Grace Bible Institute (TGBI) is located in southwestern Tanzania next to the town of Mpwapwa.
The next biggest town close to TGBI is Sumbawanga and the regional capital of the area where TGBI is
located is Mbeya. Lake Rukwa is also close by. Figure 2 reveals the location of TGBI when looking at all
of Africa, and Figure 3 shows TGBI’s specific location in southwestern Tanzania.
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Figure 2. Map of TGBI in the Context of Africa, Marked with the Star2
Figure 3. Map of TGBI in the Context of Southwestern Tanzania, Marked with the Star2
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The Tanzanians living in the region around TGBI say of themselves that they are “the forgotten
region.” The region is one of the most underdeveloped in all of Tanzania. It is also located on the plateau
that stretches across much of Tanzania, which means TGBI is at a high altitude. The highest point on the
compound is at an elevation of 2087 meters or 6846 feet.3 Although Tanzania is close to the equator and
most places are quite warm, the elevation of Mpwapwa results in relatively cool temperatures throughout
the year. Figure 4 displays the average monthly temperatures in Mpwapwa throughout the year.
Average Monthly Temperature in Mpwapwa
78
25
76
74
23
72
22
70
21
68
20
66
19
64
Temperature (C)
Temperature (F)
24
18
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
Figure 4. Average Monthly Temperature in Mpwapwa, Tanzania4
1.2.2 Problem Definition
Although the TGBI campus has access to electricity due to the recently installed hydroelectric dam, there
is not enough electricity to utilize electric stoves for cooking. Consequently, cooking is done using
firewood. This firewood is collected from trees surrounding the campus. In fact, TGBI purchased a plot of
land specifically to grow a forest in order to have a supply of firewood. However, over time, this forest
has been cut down and there are no longer any trees to harvest. This process was sped up because people
from the nearby village of Mpwapwa have also been running out of sources for firewood and began
stealing trees from the TGBI land. Now the college has begun cutting down the remaining trees that are
on campus. This deforestation not only poses a problem for those seeking out sources of firewood. It also
impacts the overall health of the environment. As is the case across much of Africa, desertification is
becoming a concern. Trees are cut down, nutrients leave the soil, arable land is lost, and the desert
expands. Figure 5 exposes the vulnerability of nations across Africa to desertification. TGBI is located in
the yellow, moderate risk area for desertification.
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Figure 5. Desertification Vulnerability of Africa5
The final issue that the campus is facing is the manner in which it deals with its human waste. Currently,
the latrines are located over holes in the ground that store the waste until it is full, at which point a new
hole is dug and the latrine is moved. Therefore, pathogens found in human feces are exposed to the soil
and may cause sanitation concerns.
1.2.3 The Client
The official client for this project is TGBI. The headmaster of TGBI is Fraison Ismail, so he is the one
who will ultimately receive and accept the project design. However, most of the interactions regarding the
project have been with Steven Sherman who is one of the founders of TGBI. He currently acts as an
advisor to the school and has intimate knowledge about the TGBI campus and their desires as an
institution. Mr. Sherman is currently on home assignment, which has made it easier for the team to
contact him, but he does not have access to some of the exact data that is needed about the campus. As a
result, Mike Caraway, who lives on the TGBI campus, has stepped in to help retrieve some more specific
data that is needed.
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1.2.4 The Project
One of the resources that is available on the TGBI campus is a pig farm. TGBI invested in a pig barn so
that they could raise and sell pigs as a source of income that could supplement each student’s tuition. This
pig barn houses between 90 and 150 Landrace Pigs6. On average, there is one boar, twelve sows, and each
sow has an average of seven piglets every seven months. The piglets grow to full size over the span of
fourteen months at which point they are sold to butcheries.
Currently, the pig manure is collected and dried. The dried waste is used as fertilizer in the surrounding
fields. The human waste is collected in pits in the ground and allowed to enter into the soil. Our project is
to collect the pig manure and possibly human waste into an anaerobic digester where the volatile solids in
the waste will be broken down by anaerobic bacteria to produce biogas. Biogas is about 60% methane and
40% carbon dioxide.7 Consequently, it can be used as a fuel for cooking. Therefore, it will be collected in
the digester above the waste slurry and piped from the digester to the kitchens on TGBI’s campus where it
will be burned to cook food. The non-volatile solids remain in the slurry and exit the digester after an
appropriate retention time so that the majority pathogens in the liquid effluent are destroyed. This effluent
slurry can then be used as fertilizer in the fields. A further discussion on pathogen destruction and land
application uses is in section 4.3.
2. Project Management
2.1 Team Management
Each team member has been given certain unique tasks and responsibilities in order to appropriately
divide and conquer the work that must be done to complete this project. All the team members have
research and report writing responsibilities. Furthermore, all team members have been searching out
possible locations to build the prototype and possible sources of pig manure.
More specifically, Austin Kearby is responsible for scheduling and communications among the team. He
has been communicating with Heather Chapman, who is an Environmental Health & Occupational Safety
officer at Calvin College, Jeff Wing, who has experience installing anaerobic digesters in the developing
world, and a variety of other contacts. Austin has also been working on the sizing of the digester. Mitchell
Porch is the webmaster for the group and has been in charge of shape considerations for the digester. He
has also headed up the research on the different mixing options and the benefits of mixing. Mitchell has
also been in charge of following up with a promising source for pig manure. Trevor Sherman has been the
main connection with the client. He also has been in charge of connecting with Team Kinyesi’s industrial
advisor, Jeff Friesen. He has done most of the CAD drawings necessary for the prototype. Trevor is also
in charge of investigating the retention time necessary to sanitize the waste and the exact chemistry that is
happening in the digester. Trevor has also done most of the Inventor work to develop a computer model
of the prototype. Due to the interconnection between retention time, sizing, mixing, and shape, Trevor,
Mitchell, and Austin have been in close communication about their research and findings. Lucas
Schreiber, as the electrical concentration, is in charge of the heating of the digester. He has also been in
charge of setting up the control systems for the prototype, such as measuring the amount of gas produced
and on/off controls for the heating. He has also been investigating possible grants that the team could
apply for to fund the construction of the prototype.
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2.2 Scheduling
Team Kinyesi’s project is split into two main parts, which are divided by the two semesters. The first
semester is predominantly research and design considerations in order to produce the project proposal and
feasibility study. The second semester is the construction and testing of the prototype in order to affirm
recommendations for the final design to be submitted to TGBI. The main goal for the prototype is that it
is constructed by mid-February so that there is adequate time to test the process. Consequently, the Gantt
Chart is mainly for the scheduling of the second semester construction and testing. The Gantt Chart for
the first semester activities is available in Appendix A. The Gantt Chart for constructing the prototype is
in Appendix B.
Throughout the first semester, the team has met at least two times per week on Monday and Wednesday
afternoons after Senior Design class in order to report on research, discuss alternatives, and assign tasks
for each team member moving forward. Furthermore, the team has decided to meet with Professor
Masselink every other Monday afternoon at 3:30PM. First, there is a review of the previous meeting;
second, team members give a progress update; third, problem areas are addressed in the form of “yellow”
or “red” flags; finally, goals for the next meeting are established. Even though official meetings with
Professor Masselink only happen every other week, Team Kinyesi is in consistent dialogue with him
throughout the week, especially regarding problem areas. Team Kinyesi also met with their industrial
consultant, Jeff Friesen, via video chat on November 10th 2015, and November 30th, 2015. Notes from the
meetings with Jeff are in Appendix G.
2.3 Budget
Since one of the goals of Team Kinyesi is to build a prototype of an anaerobic digester, there will be
funding needed to purchase the necessary materials. A preliminary budget was developed by the team that
totaled $2,500. This was based on worst case situations and a prototype of eight cubic meters or
approximately 283 cubic feet. Upon review of the proposed budget, Team Kinyesi was cautioned about
the proposed size of the prototype. Consequently, the size of the prototype has been reduced.
Furthermore, the shape of the prototype is being reconsidered based on recommendations from Jeff
Friesen, and there will likely be access to electricity at the prototype location. Therefore, the budget
should be reduced significantly. Still, there will be a need for funds. Currently, the two sources of funding
are the given senior design funds and the Eric Degroot Engineering Fund. However, more sources are
being investigated.
2.3.1 Senior Design Funds
Each senior design team is provided with $500 for their project. However, depending on the project,
differing amounts are needed. Since Team Kinyesi’s budget surpasses the $500 budget provided to the
team, they will have access to the full $500. It is unknown as to whether any more money will be given
from the senior design funds, but no more is expected. Therefore, outside sources are being considered.
2.3.2 Eric DeGroot Engineering Fund
“The Eric DeGroot Engineering Fund supports engineering student design projects that promote Christian
caring, social justice, stewardship, and community impact”.8 The fund has $1,000 that the Senior Design
professors divide among the teams as they see fit. Since this waste reuse project aligns with the goals of
the Eric DeGroot Engineering Fund, Team Kinyesi applied to receive a portion of the funds. The team
was offered and accepted $825 to help support the project. The proposal that Team Kinyesi produced for
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the Eric DeGroot Engineering Fund is available in Appendix C. The preliminary budget is also part of the
proposal in Appendix C.
2.4 Method of Approach
Team Kinyesi has sought to approach this project with humility, gratefulness, and an anticipation for a
future product that truly benefits those who are affected by it. This group knows that in order to be
successful there has to be teamwork. There must be a divide and concur mindset which requires for there
to be trust among the team members. For there to be trust there has to be unity and comradery so that each
member desires to contribute and not let down his fellow teammates. Humility is how the members
should approach each step of the project. Beyond the meetings described above, the team will
communicate via cell phone or email. All of those communications must be approached with humility so
that when tension arises, it is dealt with appropriately. The team will approach the design of the digester
by researching many different types of designs and then choosing the most beneficial design for TGBI.
The opportunity to go more in depth about anaerobic digestion and to be involved in a project that has the
potential to influence peoples’ lives is exciting for the team. Therefore, the team is grateful to be a part of
this project. Ultimately, Team Kinyesi is seeking to be a good steward of the gift of God’s grace in the
lives of each individual so that the time and effort invested might make much of Jesus Christ.
3. Project Overview
3.1 Objectives
In order to produce a successful digester, Team Kinyesi has partnered with its clients and advisors to
document specific objectives for the project. These objectives aid in setting up an appropriate scope for
the project. Determining the scope of the project is critical to the project’s success and to ensure that the
work being done is worthwhile. The objectives are following.
3.1.1 Provide a Full Scale Design and Operations Directions
The main objective for Team Kinyesi is to produce a design of a full scale anaerobic digester to be
installed on the TGBI campus. This design will include the recommended location of the digester,
construction recommendations, piping recommendations, and effluent processing recommendations.
Furthermore, the design will include directions for operating the digester along with possible problem
indicators and solutions. The products from the digester are biogas to be used for cooking and fertilizer to
be land applied.
3.1.2 Develop and Build Prototype
In order to produce a better design of the full scale anaerobic digester, the team has decided to build a
prototype to test the kinetics and feasibility of the process and design. Therefore, the second objective is
to construct and test this prototype. The prototype will be a scaled down version of the proposed design
for TGBI. It will be built here in the United States, either on the Calvin College campus or at Plummer’s
Environmental Services. More about the details of the construction location can be found in section 7.1.
The desired use of the prototype is to confirm the various elements of the design. Furthermore, Professor
Wunder has recommended that construction of the prototype will not only be valuable for the final
design, but also for the experience for the members of Team Kinyesi.
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3.2 Requirements
Another important part for the scope of the project is determining the constraints and requirements that
the design must meet. The following requirements have been set with the assistance of Team Kinyesi’s
clients and advisors.
3.2.1 Minimal Maintenance System
The first requirement is that the design requires minimal maintenance. Parts are very hard to come by in
southwestern Tanzania, as the nearest town, Mpwapwa, is not very developed. This along with a lack of
technical education amongst the staff at TGBI makes it very hard to upkeep any advanced systems that
require maintenance. Therefore, the digester must be simple to run and easy to take care of so that TGBI
can own it, take care of it, and be blessed by it for many years.
3.2.2 Provide Alternative Cooking Fuel
The second requirement is that the digester needs to produce enough gas for cooking at TGBI. The
average class attending TGBI is 20 students. These students are cooked for by the TGBI staff. During a
normal day, students will have tea in the morning, which requires boiling of water. TGBI also provides
students with lunch and dinner. Both of those meals are made up of mostly ugali and mboga, a corn meal
and sauce dish. These foods are hot foods and require heating. Consequently, the biogas produced must
be able to provide enough fuel to cook 60 hot meals per day.
Sixty meals per day is a difficult measurement to compare against gas output. Consequently, the 60 meals
per day requirement must be stated in terms of liters of biogas needed per day. Based on the paper,
“Anaerobic Digestion of Biowaste in Developing Countries,” a family of five takes around 2.5 burner
hours per day to cook their food.9 Therefore, ten hours of burner time will be needed to cook food for 20
students. Depending on the burner, 200 to 450 liters of biogas are consumed per hour of cooking.9
Consequently, the digester needs to produce a minimum of 4,500 liters of biogas per day in order to
provide for the cooking needs of the students at TGBI.
3.2.3 Energy Efficiency
The TGBI compound has access to 23 kilowatts of electricity because of the newly installed hydroelectric
dam.10 Therefore, another alternative to burning wood is utilizing electric burners. In order for the
digestion process to be more beneficial than using electric burners any heating that may be required in the
design must use less electricity than the electric burners. Furthermore, any electricity used for heating the
digester must not exceed seven kilowatts in order to ensure that the college has enough electricity
available for its other needs.11 This is not the confining requirement as using electric burners uses between
one and three kilowatts for an equal number of cooked meals.12 Due to the low cost of induction heating,
the goal of the team is to eliminate any reliance on electricity.
3.2.4 Effluent Quality
Since not all of the influent solids are broken down to produce biogas, there is an effluent stream from the
digester. The goal is for the effluent stream to be used as fertilizer in the fields. The pig manure can be
land applied without going through digestion. However, biological digestion breaks down complex
molecules into more simple molecules, which are nutrient rich and are beneficial for land application.
Digestion also reduces the number of pathogens in the waste as described in section 4.3 on Effluent
Quality, which reduces the risk of disease. The pathogens that are removed are also responsible for the
bad odors associated with the waste, therefore the process also achieves odor reduction.
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3.2.5 Cost
Based on meetings with client Steven Sherman, the cost requirements are dependent on the amount of
money that can be raised by TGBI. He estimated that $3,000 would be a feasible amount to fundraise.11
3.3 Design Norms
Every project has a desired goal or outcome with key attributes that are used to achieve that goal. This
project is aimed towards being implemented in a different country where people have very different
outlooks on life compared to Western thinkers. This team also consists of different people with different
skill sets, backgrounds, and ideas. As a group, three different design norms were chosen for each
individual to uphold as paramount in the pursuit of accomplishing this project. The design norms include
stewardship, trust, and cultural appropriateness.
3.3.1 Stewardship
The design norm of stewardship is defined as a design that focuses on the “conservation of finite
economic, human, and environmental resources.” Such a design also focuses on “minimizing degredation
of the environment.”13 The team is seeking to design a piece of equipment that brings honor and glory to
God. This is being done by seeking to improve the quality of life for his people while being better
stewards of the resources that he has provided to us. The whole goal of the design is to reuse waste in
order to avoid cutting down trees, which degrades the environment. Consequently, this project fully
embraces the design norm of stewardship.
3.3.2 Trust
The design norm of trust means that the design must be dependable, reliable, and trustworthy.13 The team
must work together to be able to accomplish the project successfully. This means that members need to
trust each other in the work that they do. There will be accountability but there will be an expectant trust
between the members as well. The team will seek to build trust with advisors and others involved by
completing tasks in a thorough and timely manner. Furthermore, the team desires that the final design will
be dependable and reliable. TGBI will have to invest significant funds in order to implement this digester
with the expectation that the design will pay for itself over time. Consequently, the design must last and
provide the energy that is expected so that the client is not negatively impacted. The design norm of trust
also applies to Team Kinyesi’s prototype construction. They must use the appropriate procedures to make
sure that the prototype is safe to construct and use.
3.3.3 Cultural Appropriateness
Team Kinyesi is planning to implement this digester in Tanzania, which has a culture that is very different
from the culture here in the United States. Therefore, it is important that the design “preserves what is
good in the culture” and “respects and values the diversity”13 between Tanzania and the United States.
The team will approach this cross cultural engagement with humility and an open mindset to learn. The
digester will be designed to fit into the Tanzanian culture even though it is different from the culture that
surrounds Team Kinyesi.
3.4 Basic Design
The initial idea for this design project was based on the work done by the National Biodigester Program
in Cambodia. The general setup for the digester is pictured in Figure 6. There is an influent chamber
where the manure is collected and mixed with water. The influent chamber is connected to the main
11
digester via piping. The main digester is where the waste is broken down to form biogas. The biogas is
captured at the top of the biodigester. From the top of the digester, the biogas is piped to be used as fuel.
The solids that remain move towards the manhole, which provides access from the outside in case of
maintenance needs. Normally this is a closed system until the effluent enters the outlet tank where it can
be used for fertilizer. High pressures can be relieved naturally by pushing down on the liquid and
escaping through the u-bend trap created between the digester and the manhole.
Figure 6. Anaerobic Digester Model14
4. Research
4.1 Anaerobic Digester Types
There are many different types of anaerobic digesters that may be used to produce biogas. These different
digesters may be tailored to suit specific requirements depending on the need of the situation. Considered
here are three different digester types including plug flow, continuously mixed flow reactor (CMFR), and
the sequencing batch digester (SBR).
4.1.1 Plug Flow
Plug flow digesters by definition have a high length to width ratio. They are generally five times as long
as they are wide. Plug flow digesters usually have an influent stream with high solids contents ranging
from 10-15%. Due to manure slurries being watered down via the collection process, solid material must
often be added to the manure slurry to make it thicker. The waste moves along as a plug through the
system. Often mixing is not a part of the plug flow process. When waste is added on the influent end to
the digester an equal volume is displaced on the effluent end.15 A plug flow is also almost always heated
to ensure that the process is mesophilic.
4.1.2 Continuously Mixed Flow Reactors
Continuously Mixed Flow Reactors (CMFR) generally consist of a round or egg shaped tank with an
influent stream of liquid manure (3-6% solids) that is mixed and heated. As new fluid is introduced to the
digester on the influent end, the same amount of volume is displaced on the effluent end. Biogas is
constantly generated and is maintained by systematically adding manure to the digester. Target retention
12
time for the manure in a mesophilic CMFR system is approximately 20-30 days. Retention time can
decrease if the system is run at thermophilic temperatures.15
4.1.3 Sequencing Batch Digester
An Anaerobic Sequencing Batch Digester (ASBR) works in four stages. Part one is the fill stage when the
digester is loaded with the new manure. Part two is the react stage in which the manure and microbes are
mixed together. Part three is the settling stage where the solids are separated from the liquids. Part four is
the decant stage where the treated fluid is removed. This four stage cycle could be done one batch at a
time but due to a long startup time for digestion to begin it would not be recommended.15
4.2 Microbiology of Biogas Production
Once inside the digester, it is important to understand what happens to the waste. The anaerobic digestion
process is a multi-step chemical process catalyzed by a mixed group of bacteria. The waste enters the
digester as complex organic matter. This complex organic matter includes lipids, carbohydrates and
proteins. Figure 7 displays the multi-step process that occurs.
Figure 7. Multi-step Nature of Anaerobic Digestion16
The bacteria initiates the hydrolysis of the organic compounds. The general form of hydrolysis is shown
in Equation 1. An organic compound reacts with water to produce fatty acids, amino acids and sugars.16
Equation 1: C6H10O4 + 2H2O → C6H12O6 + 2H2 (Hydrolysis Reaction)
13
The next step in the process is a reaction where the fatty acids produced in the previous reaction react to
form hydrogen. Other reactions in this step react with sugars, and amino acids to produce acetic acid,
propionic acid, and butyric acid. This step is called acidogenesis. The equations associated with this
process are shown in Equations 2-4.16
Equation 2: C6H12O6 ↔ 2CH3CH2OH + 2CO2
Equation 3: C6H12O6 + 2H2 ↔ 2CH3CH2COOH + 2H2O
Equation 4: C6H12O6 → 3CH3COOH
The next step is called acetogenesis. In acetogenesis the propionic acid and butyric acid react to form
acetic acid and hydrogen as shown in Equations 5-7.16
Equation 5: CH3CH2COO- + 3H2O ↔ CH3COO- + H+ + HCO3- + 3H2
Equation 6: C6H12O6 + 2H2O ↔ 2CH3COOH + 2CO2 + 4H2
Equation 7: CH3CH2OH + 2H2O ↔ CH3COO- + 2H2 +H+
In the final step, methanogenesis, methane is formed from hydrogen and carbon dioxide. Methane is also
produced through ethanol reacting with carbon dioxide, and acetic acid degrading. These chemical
processes are shown in Equations 8-10.16
Equation 8: CO2 + 4H2 → CH4 + 2H2O
Equation 9: 2C2H5OH + CO2 → CH4 + 2CH3COOH
Equation 10: CH3COOH → CH4 + CO2
The above reactions are the main reactions that occur. However, there are small side reactions that
produce compounds such as hydrogen sulfide, which is a safety concern. Hydrogen sulfide is produced if
the digestion is not complete. When the reactions proceed to completion, only methane and carbon
dioxide should be present in the biogas. Therefore, concerns arise when conditions in the digester do not
propel the reactions to reach completion. Such conditions include the acidity, the carbon to nitrogen ratio,
and the temperature in the digester.
4.3 Effluent Quality
4.3.1 Destruction of Pathogens
Along with biogas production, anaerobic digestion serves to destroy pathogens in the slurry. The
pathogens are eliminated through two processes. Pathogens are starved through competition with other
organisms. Any aerobic pathogens are starved of oxygen.17 This effectively reduces the number of
pathogens. Another way pathogens are reduced is through the presence of organic acids in the slurry.18
The organic acids create an environment unsuitable for some pathogens to exist. The effectiveness of the
pathogen reduction correlates to the retention time of the slurry in the digester. For a plug flow reactor
with a twenty day retention time at mesophilic temperatures, pathogenic bacteria were reduced by over
99%.19 Similar results are expected from the digester that team 18 is building.
14
4.3.2 Nutrient Recovery in the Effluent
The anaerobic digestion process removes primarily carbon from the waste mixture, this leaves behind
valuable nutrients. These nutrients are mineralized into more biologically available forms through the
chemical digestion done by the bacteria. This proves to be a much more effective fertilizer than the waste
prior to digestion. The state of the waste after digestion allows for a quick-release organic fertilizer that
can be used on farmland for maximum plant nutrient uptake.20
4.3.3 Solids Consumption
In a practical digestion time of 20-30 days at mesophilic conditions most often only 40-60% of the
volatile solids are consumed. “As a general rule, eight cubic feet of methane gas is released for every
pound of volatile solids converted in the digestion process.”20
4.3.4 Effluent Testing
Due to the complexity of testing the effluent quality, this has been deemed outside of the project scope.
Extensive laboratory testing would be required.
4.4 Methane Heating
Anaerobic digestion of waste produces a mixture of gases, which is called biogas. Biogas consists of 4050% carbon dioxide, 50-60% methane, and about 1% hydrogen sulfide, ammonia, and other trace gases.
Pure methane has an energy content of 1000 BTU/ft3. Due to the mixed nature of biogas it has an energy
content of 500-600 BTU/ft3. Methane is combustible between concentrations of 5 and 15% in air. As the
concentration of the methane produced by anaerobic digestion is higher than the minimum for
combustion, the biogas will work as a fuel for burning.20
5. Design Factors
Anaerobic digestion design is impacted by numerous factors including temperature, manure
characteristics, hydraulic retention time (HRT), slurry concentration, acidity, loading rate, mixing, shape,
and size.
5.1 Temperature
Temperature is one of the most important factors that influence the production of biogas in an anaerobic
digester. There are three primary temperature ranges where the bacteria thrive. The first range is the
psychrophilic range, which operates below 68°F.21 The second range of temperatures is the mesophilic
range, which is between 90°F and 110°F.21 The third range of temperatures is the thermophilic range,
which is between 120°F and 140°F.21 Most anaerobic digesters run in the mesophilic range because it
does not require as much energy to heat the digester to 90°F compared to 120°F and the production of
biogas is significantly more than the psychrophilic range. Furthermore, the main benefit in digesting at
the thermophilic range is speed of digestion and therefore lower hydraulic retention time. These benefits
usually do not outweigh the cost of heating. Team Kinyesi has chosen to run their digester in the
mesophilic range.
More important than the temperature level, is keeping the temperature consistent. Changes in temperature
of more than 5°F drastically reduce the activity of the bacteria.21 Consequently, having a controlled
heating system for the digester is important. There is an entire section on heating following the design
factors of the digester.
15
5.2 Manure Characteristics
Another major influencing factor in the digestion of wastes is the carbon to nitrogen ratio (C/N ratio) of
the manure. The average C/N ratio for pigs is seven, 22 and the typical C/N ratio for humans is eight.
However, the ideal C/N ratio for the waste entering the digester is between 20 and 30.23 In order to reach
the optimal C/N ratio, high C/N ratio sources like sawdust (C/N = 200) or maize straw (C/N = 60)23 must
be added with the manure at the influent mixing chamber. The age of the manure also impacts methane
production. The longer the manure has been exposed to the atmosphere, the lower the amount of biogas
production.
The physical characteristics of the influent slurry also have an impact on the biogas production. Fresh pig
manure is composed of 9.2% solids.24 Depending on the type of digester, the percentage of solids is
increased or decreased. For the case of TGBI, water will be added to the pig waste at a 1:1 ratio.
Consequently, the percent solids of the influent slurry will be below 5%. Having a low percent solids
results in higher hydraulic retention times and therefore a large size of digester. However, it also reduces
the need for mixing.
5.3 Hydraulic Retention Time
Hydraulic Retention Time (HRT) directly impacts the quality of the effluent as well as the amount of gas
that is produced. HRT varies with other process parameters like influent composition, temperature, and
shape of the digester. Running the digester in a different temperature range affects the HRT: Mesophilic
range is faster than the psychrophilic range, and thermophilic range is faster than the mesophilic range.
The shape of the digester also changes the HRT. A higher length to width ration results in a longer HRT.
A higher volatile solids (VS) percentage composition of the influent will require a longer retention time
for the VS to be processed to the desired level. In general retention time for mesophilic digestion is
around 15-30 days.25
In a reactor where there is not any microbe recycling HRT = Solids Retention Time (SRT). HRT is a
function of the size and shape of the biodigester. A longer HRT means a greater percentage of the VS are
consumed. This rate of consumption decreases over time with approximately a first order rate of decay.
There is a ceiling that the microbes reach where the ‘food’, the VS, cannot sustain the growth of microbes
and they begin to die. Consequently, the benefit of having the slurry in the reactor for a longer period of
time is null.
5.4 Acidity
Acidity plays a critical role in whether biogas will be produced. The methanogens need a relatively stable
pH in order to thrive. A neutral pH of 7 is best, and a pH lower than 6.2 inhibits growth.26
In the case of pure animal waste, pH is often stable. The system is sensitive to significant changes in the
loading rate of VS. In the second step of the digestion process, acidogenesis, acidogenic bacteria create
organic acids as one of their products.16 If the VS concentration is increased suddenly the acidogenic
population of bacteria spikes also spiking the amount of acid produced. This causes a drop in the pH that
‘sours’ the reactor. The drop in pH inhibits the growth of methanogens and therefore ultimately slows or
stops the anaerobic digestion process.
The primary mechanism to ensure stable pH in the slurry is to maintain a consistent loading rate. Another
mechanism used to increase the pH of the slurry is to add lime. However, the addition of lime will only
reliably bring the pH up to 6.4. Furthermore, the addition of lime to the digester may result in other
16
issues. Such issues include solids build-up which results in a loss of digester volume and safety
concerns.27 Consequently, using lime to help control the pH of the slurry will only be used as a last resort.
5.5 Influent Loading Rate
In order to maintain stability in the digester, the loading rate must remain consistent so as to maintain the
reaction processes, described in section 4.2, and so as to not sour the reactor. The loading rate is usually
in terms of weight of volatile solids (VS) per day and is usually between 0.1 and 0.5 lbs VS per day per
cubic foot of digester.7 Since the digester functions better at a constant loading rate, any changes in
loading rate must be gradual. As a result, when starting up the digester, it is important to slowly build up
the loading rate so that the necessary bacteria can grow. It is recommended that the digester is filled with
water at the beginning of digester operations. The first week’s loading rate should be no more than 20%
of the final loading rate, and in the following weeks the loading rate can increase by 20% each week until
the full loading rate is reached.20 During normal operations, increase or decrease of pig waste production
must be dealt with appropriately so that loading rate changes are minimized.
5.6 Mixing
Research suggests that the thickness of the slurry is what dictates whether or not mixing is beneficial. The
target manure percentage for this project is approximately 4.5% solids. A slurry that is 5% solids
produces similar amounts of biogas whether it is mixed or unmixed. This is possibly due to the fact that
the gas being produced in the slurry that travels to the top provides some mixing. With a more liquid
slurry the gas bubbling to the top may provide sufficient mixing without added mixing from other
mechanical sources such as biogas recirculation, impeller mixing, or slurry recirculation. A slurry that is
10% solids produces significantly higher amounts of biogas when it is mixed. When the thicker 10%
slurry is not mixed, the breakdown of solids in the slurry is not as consistent and therefore mixing
becomes critical for thicker slurries. The target slurry mixture for this project is approximately 4.5%
solids and thus should not require mixing.28 A decision matrix regarding the different mixing options is
available in Appendix E.
5.7 Structural Shape
The shape of the digester helps decide what type of digester is being designed. The two alternatives
considered are a cylindrical and pill shaped digester body.
5.7.1 Cylindrical shape
One alternative for the digester shape is for it to be cylindrical and upright. A cylindrical shape helps to
improve mixing the waste inside the digester which helps to keep the bacteria in contact with the nutrients
it needs in order to continue producing biogas. Waste entering the digester should not be able to cross the
digester and exit before sitting in the tank for the proper retention time. This would be considered a short
circuit in the system. The process of mixing also helps to prevent this short circuiting issue because it
spreads the newer influent more evenly throughout the waste slurry.29 Another advantage to the
cylindrical shape is the availability of existing structures. Plastic cylindrical tanks are readily available
which would serve this purpose well.
5.7.2 Pill shape
A longer pill shaped digester was suggested to help move entrance and exit locations farther apart. The
goal of this shape is to help prevent the incoming slurry from exiting prematurely which would reduce
short circuiting issues. This shape also helps increase hydraulic retention time (HRT), without increasing
17
the size of the digester. This would help keep costs down while increasing HRT. Often this design
employs the use of a trench. The difficulty that arises through the use of a trench is maintaining an
oxygen free environment in the digester. A liner or some other method must be used, which requires
expertise and is expensive.
5.8 Digester Size
Due to the numerous factors that influence the size of the digester, there are a variety of sources with
suggested digester sizes. Some sources compare numbers of pigs to the size, but others compare the
weight of pig manure to the size. After comparing a variety of sources, it was necessary to consider the
influent waste in terms of maximal and minimal sizes. Table 1 displays the minimum and maximum
predictions for our final digester. The calculations for these predictions are in Appendix D.
Table 1. Sizing Estimates Based on Research
Criteria
Live Weight of Pigs (lbs)
Manure Weight (lbs/day)20
Biogas Production (Gal/day)7
Energy Production (BTU/day)7
Sizing Needs (ft3)23
Sizing Needs (ft3)14
Sizing Needs (ft3)21
Minimum
10,431
4,172
2,185
17,5243
1,059
706
450
Maximum
18,867
7,547
3,952
31,6958
2,119
1,236
750
6. Heating
6.1 Required Heating
6.1.1 Temperature Requirements
For this design, the team has chosen the bacteria that live in the temperature range from 90°F to 120°F,
the mesophilic range.21 As a result, it is required to heat the slurry inside the digester to that temperature
range. Beyond the need to heat the slurry so that the mesophilic bacteria can grow is the need for the
temperature to remain constant. The bacteria does not react well to changes in temperature. Therefore,
sudden temperature changes will destroy the bacteria and halt the process of biogas production. This must
be avoided. As a result, both the prototype and the final design must be heated consistently.
6.1.2 Thermal Properties
The slurry is a mix of a variety of substances which have various thermal properties. However, the vast
majority of the slurry is water. Therefore, the slurry can be assumed to have to properties of water. This
assumption is consistent with other professional papers that the team researched. Therefore, the specific
heat capacity of the slurry is 0.360 Btu/(hr ft °F), which is the specific heat capacity of water.
6.1.3 Heating Factors
There are a variety of factors that must be considered when choosing a heating method. The first factor is
the size and shape of the digester. Depending on the size of the digester, only certain heating methods
may be feasible. For example, there are heating jackets that could be used for digesters that are small (55
18
gallons or less) and cylindrical. For larger digesters, using a heating jacket becomes improbable.
Furthermore, the piping of a heat exchanger will be confined inside the digester.
The second factor that Team Kinyesi must consider with heating is whether or not the digester will be
buried. One of the main forms of heat loss from the digester is through convection. If the digester is
buried, this form of heat loss will be minimized. Furthermore, since consistent temperatures are required,
burying the digester is beneficial. The ground acts as insulation for the digester if it is buried. The burying
option is specifically for the final design because it will be difficult to dig a hole in the ground for the
prototype in the middle of winder in Michigan. Instead, the prototype can be covered with an insulating
blanket.
Another factor that influences the heating of the digester is the weather. The average temperature in
Mpwapwa near TGBI is displayed in Figure 4. Those temperatures are drastically different from the
temperatures in Michigan. Therefore, the heating requirements for the final design will be significantly
different from the heating requirements for the prototype. The biggest concern with temperature in
Tanzania is at night when temperatures can drop below 45°F. In Michigan, the digester will be inside, but
the temperatures may still drop below freezing. Consequently, the prototype will require more consistent
heating throughout the testing period than the final design.
6.2 Energy Sources
6.2.1 Solar Heat Capture
During the winter in Tanzania there is an average of seven hours of sunlight per day. 30 Photovoltaic
energy could be captured and stored in a heat reservoir in the form of a water tank. Then the heated water
could be pumped through a heat exchanger to heat the slurry. Based on the amount of daylight that
Tanzania gets, using the sun as an energy source to help run the digester is viable.31 The one major
downside of this method of energy generation is that it is very expensive.
6.2.2 Electricity from Hydroelectric Dam
The maximum capacity of the dam is 23 Kilowatts and at least eight Kilowatts of that energy is used daily
by the people at TGBI. The campus requires a certain contingency on excess power for running power
tools and other unforeseen needs. Generally electricity would be needed to heat the digester at night when
the ambient temperature drops. At night the compound will not be requiring much of the produced
electricity so this could be a feasible option. Another problem with using the hydroelectric power is that it
would require a smart power network which is outside the scope of this project.
6.2.3 Biogas Feedback
Biogas feedback is the process of using the produced biogas to boil water for heating the digester. The
pipes run into the digester to form a heat exchanger which is controlled by a temperature monitoring
system. Before the digester begins to produce biogas a propane tank must be able to be hooked to the
system in order to support bacterial growth. Once a sufficient amount of biogas is being produced, the
propane tank may be switched off and the system will be self-sustained. This is the most viable option for
the design that will be proposed to TGBI because it will not put an increased demand on the power grid.
19
6.3 Heating methods
6.3.1 Heat exchanger
A heat exchanger is the recommended system for maintaining the slurry temperature inside of the
digester. The concerns faced with pipes running through the bottom of the digester is that they would be
in a potentially corrosive environment. This system appears to be the simplest viable option.
6.3.2 Induction Heating
Induction heating converts normal household AC power into a magnetic field which is then used to heat a
piece of conductive material. It does this by using electromagnetic induction in the conductive material
and generates heat through eddy currents; however if the conductive object is magnetic then greater
heating can be achieved through a process called hysteresis, these eddy currents are then run through the
conductive objects resistance and heating is achieved as the energy is lost over said resistance.
The problem with induction heating is that it would require a consistent source of electricity. 32 The team
would prefer to not use electricity and will choose another option if it is viable.
6.3.3 Heating Jacket
A heating jacket is a simple means by which to heat the slurry inside the digester. They are simple and
easy to use and often have a variable temperatures that they may be run at. The main problem faced with
a heating jacket is the cost associated with this product. Another issue is that it requires electricity to heat.
This option is not viable for this project due to both of these concerns.
6.4 Cost Analysis of Available Energy Sources
6.4.1 Charcoal
The cost of a burlap sack of charcoal is $14. This supply of fuel will support on average four people for
approximately 30 days.33 Over time, this expense grows to be a sufficient amount of funds. This is the
current method that is used for cooking at TGBI
6.4.2 Dried Manure
Manure is free to the people living on the TGBI campus. The problem with using dried manure for
cooking is that it is culturally inappropriate and would be used only as a last resort. This is not a feasible
option
6.4.3 Solar Power
Solar collection systems cost around $15,000 to $40,000 for approximately three to eight KiloWatts.34
This makes this option not viable as it is outside of the team budget.
6.4.4 Hydroelectric
There is a hydroelectric dam that currently provides electricity to the school. Any necessary electricity
that is needed to run the digester will be drawn from this source of electricity. This project will not require
more electricity to run the digester then would be required to cook the food with an electric stove.
20
7. Prototype
7.1 Location of Construction
Many alternatives were considered for the location of the biodigester. The first thought was to partner
with the Wyoming Clean Water Plant. However, Heather Chapman believed that it would be easier to
monitor the safety of the prototype if it was constructed on Calvin's Campus. Consequently, a number of
possible locations were investigated on campus. The three possible locations that were presented by
Heather were the Ravenswood garage located near Lake Dr. on the north side of Calvin's campus, the
shed near the garage, and the greenhouse owned by the biology department that is also located close to
Lake Dr.
Concerns were raised regarding the smell pollution that would result from bringing pig manure on
campus. The smells could impact the municipalities surrounding Calvin including East Grand Rapids,
City of Grand Rapids, and Kentwood. These municipalities would be responsible for resolving the smell
pollution and be forced to shut down the prototype.
As a result, Team Kinyesi began to look for other locations to construct the prototype. Options included
landfills, the farms where the pig waste would come from, and wastewater treatment plants. However,
after further discussion about the size and construction of the prototype, it was determined that the smell
could be eliminated at the property boundary of Calvin. Therefore, the Ravenswood garage, the
Ravenswood shed, and the biology greenhouse became options again. Due to the sparking hazard of a car
being in the garage, this option was eliminated. The shed adjacent to the garage became an option and it
has become the preferred location project implementation. The location is available in Figure 8. However,
this location still needs to be approved by Calvin College and the process of getting approval is
underway.
21
Figure 8. First Location Option for the Construction of the Prototype in the Ravenswood Shed.
A secondary option that Professor Nielsen is investigating for Team Kinyesi is Plummer’s Environmental
Services. This is a good second option because they have facilities appropriate for dealing with pig
manure and biogas. Therefore, if Calvin refuses to allow for the prototype to be constructed on campus,
the team will pursue constructing the prototype at Plummer’s Environmental Services.
7.2 Source of Waste
Another key issue that Team Kinyesi has faced is the question of where to collect pig manure. A number
of farms that were contacted did not have any kind of collection system for their waste because the pigs
roamed free in a pasture. However, after much searching, Carl Meyer has agreed to provide the team with
pig manure. Due to the safety standards on Carl Meyer’s farm, he will be collecting the manure himself.
The team plans to meet with him during January to confirm the details of collecting manure. He is willing
to provide us with manure on a daily basis. The team will collect the waste from Mr. Meyer and transport
to the prototype location in closed containers via student vehicles.
7.3 Safety Plan
Safety became a huge priority for the team due to its importance to Calvin College and the surrounding
municipalities. Heather Chapman has advised the team on the necessary safety requirements and
precautions that need to be addressed in order to keep the project safe. Consequently, the team is putting
together a comprehensive safety plan to address each step in the prototyping process. The safety plan is a
separate document that can be found in Appendix F, but some important elements about personal
protective equipment and facility requirements are presented in the report.
22
7.3.1 Personal Protective Equipment PPE
The prototype may require the mixing of the manure in an open space by team members. Certain
precautions will be taken to keep team members safe. Pig manure has a very strong smell; therefore each
member will be provided with a Tyvek suit so that their clothes will not acquire the rank odor and thus
disturb other students and faculty at Calvin. Each member will wear a face mask and gloves when dealing
directly with the slurry.35
7.3.2 Facility Requirements
The proposed garage will have a four gas meter that is running at all times. There will be no sparking
elements within the garage. This means that no cars will be allowed inside the garage. No heating
elements that are required to heat the digester will be able to spark. This nixes the idea of heating the
digester with gas that it produces. Gas that is produced will be piped outside the garage to be flared. For
the team to be able to flare, an open flames permit will be filled out and submitted. The team will take
appropriate blood born pathogen training so that if human waste is tested, it will be dealt with in a safe
and responsible manner.35
7.4 Prototype Design
The prototype design uses a combination of digester type ideas. In terms of sizing, the team will be using
a 55 gallon drum for the digester body, which can be purchased locally. The material for the drum was
chosen to be polypropylene. The drum will have four bung holes in the digester to account for all the
inputs, inflows, and outflows for the digester.
23
Figure 9. Inventor Model of Prototype Design
There will be an influent chamber to insert the slurry. The slurry will be piped into the 55 gallon drum
from this influent pipe. There will be a pH meter installed into the side of the barrel to record the pH of
the slurry. There will be a temperature gauge within the prototype that measures a differential in
temperature. There will be a PVC pipe leading from the digester to a camp stove located outside the
building where the desired biogas can be flared. This gas pipe will monitor both pressure and the
volumetric flow rate of gas. This pipe will also have a pressure release valve in the case of an excessive
pressure build up. There will be an effluent collection container that can be removed so that the waste
may be returned to the farm. The whole system must remain closed so that smell is minimized and
oxygen is not able to enter. A model of this system is shown in figure 9. A detailed drawing is found in
Appendix K that will help in guiding the team through the construction of the prototype.
24
Figure 10. Isometric view of the Inventor Model
7.4.1 Control System
The prototype control system will be run on a raspberry pi B+. This will be done by soldering the
temperature sensor to the GPIO ports of the raspberry pi B+ and then computing the necessary logic to
determine if heating is needed for the digester. The control system will then drive the switch for the
induction water heater or the heating blanket if the digester temperature falls below the allowed
temperature range. In addition to the temperature sensors and heating controls, the control system will
send comprehensive data on gas production and will alert the design team if the temperature falls
suddenly by sending information about the problem via text message and email. The prototype will, on a
daily basis, send a report via text message and email to alert team members about the current status of the
digester.
7.4.2 Heating System
For the prototype, the design team is using a heating jacket for the sake of simplicity contingent on cost.
This decision matrix may be viewed in Appendix E. Due to safety concerns the design team will not have
an open flame or any kind of spark inside of the shed. The purpose of the prototype digester is to make
combustible gas in an enclosed space. The alternative was to use induction heating with a heat
exchanger. This would be a cheaper alternative, however there is a risk of sparks as an electric pump
would have to be used to create a flow of water into and out of the digester.
25
For our prototype design it is unknown before testing if a pump is needed to create flow through the heat
exchanger or if the design can just use two one way valves as to make a gurgle flow like in hot water
heater for coffee which happens also to be inductively heated. However if a pump is needed to achieve
some flow through the heat exchanger then one will be added.
For the induction heater with a heat exchanger the design calls for either an “Ecosmart POU 3.5 Point of
Use Electric Tankless Water Heater”36 or one of three unnamed heaters from “GUANGDONG
MAGGICAL ELECTRIC APPLIANCES CO.”37 38 39 all four of which can meet the requirements. The
decision between the four will be made on cost, shipping time, and ease of use overall.
Table 2. Induction Heating Cost Comparison
Cost and Next Best Alternatives Control System Heater Heater (cont.) Piping Fittings Other Sundries Item Cost($) Alternative Cost($) Raspberry Pi B+ POU 3.5 38
PVC ½ inch 40 160 27 to 270 0.527 per foot Raspberry Pi Zero 5 37
30 to 80 39
30 to 50 1% Carbon Steel ½ .80 per foot with inch need of at least 6ft Elbows Unknown with need of at least 8ft 0.36 x2 = 0.72 Elbows 50 Empty 2.34 0 320 Total Minimum 75 Maximum The total cost of all of the control and heating elements for the prototype is about $320 maximally and
$75 minimally this all depending on if the design does in fact need a pump and the heater is bought
cheaply or for ease of use.
The cost of the heating jacket comes to about $300 not including the controls system. The team has
allocated about $400 for the heating system, which appears feasible with costs mentioned above.
7.4.3 Prototype Heating Requirements
The heating calculations to model the prototype design were a pipe for the barrel wrapped in an insulating
blanket. This was done to find the heat loss due to the surrounding of the shed during the winter and
therefore the heat needed to be added constantly back in by the heat exchanging pipes. The heat
exchanging pipes were modeled as pipes in thermal contact with their surrounding as that is their purpose.
The heat transfer calculations can be found in Appendix J.
7.4.4 Prototype Assembly and Testing Plan
An assembly and testing plan was deemed necessary. The plan details calibration tests, and proper
assembly order, especially for the sensors. The testing plan is found in detail in Appendix H.
26
7.5 Parameters to test
7.5.1 pH
The pH of the slurry should be monitored as the bacteria in the digester are highly sensitive to a pH drop
below 6.2. A digital pH meter will be installed within the digester to provide this needed information.
One of the options is to ask Calvin College if they have a good pH meter that can be used by Team 18 for
the duration of this project. If that doesn’t work than a pH meter will be selected and purchased for the
use of the team.
In any case the pH meter will be connected to the control system in order to alert the team to any drastic
changes, and for recording purposes.
7.5.2 Temperature
Temperature will need to be monitored as the bacteria are sensitive to temperature changes. The goal is to
maintain this temperature range through a heating jacket. A control system will control whether the
jacket is on or off. This will need to be tested initially to see its effects on water.
In all of the gauges that are used a concern is the corrosive nature of the H2S gas among other trace gases.
However, in a shorter length operation time as is the case for this prototype the corrosion will not have a
damaging effect.
7.5.3 Influent Composition
The composition of the influent slurry is a major factor in gas production. Based on initial calculations,
the team plans to load one gallon of manure with one gallon of water. This dilution of the manure will
result in the desired total solids percentage of around 5%. The addition of water depends on the collection
process that Carl Meyer has in place. The addition of one gallon of manure is equivalent to loading 0.1 lbs
VS per day per cubic foot of digester. Furthermore, adding approximately two gallons of slurry to a 55
gallon digester results in a HRT of 25 days. To change the loading rate water will be added to the waste at
different rates, but changes will be made slowly so as to not sour the reactor.
Another element of the influent composition that the team must account for is the C/N ratio. In order to
achieve a C/N ratio of around 20, the team must mix either 0.7 lbs of saw dust or 3 lbs of corn straw.
Corn straw is more applicable for the final design, but sawdust will be easier to acquire for the prototype.
Calculations for C/N ratio composition are in Appendix I.
7.5.4 Solids Consumption
Weight of influent stream and weight of effluent stream must be measured to determine the amount of
solids consumption. A simple hanging scale will be used with the 5 gallon buckets. In order to determine
the total solids consumption, team members must keep track of the weights added and removed
throughout the entire testing period.
7.5.5 Volume of Gas Produced
In order to determine the volume of gas that is produced by the prototype, Team Kinyesi must use a flow
meter and a pressure gage. However, one of the issues with measuring the amount of biogas that is
produced by the prototype is that the flow will be lower than most flow meters can detect accurately. The
gas can also be wet and dirty, which causes problems for some meters.40 Therefore, the flow meter that is
27
used must be able to overcome these challenges. Fluid Components International LLC (FCI) produces a
flow meter that is specifically for low flow biogas that may be wet and dirty. A similar product is used by
the company where Jeff Friesen works. It is called a Flo-Wing Meter. Jeff and his bosses have agreed to
provide Team Kinyesi with this flow meter. They might also provide Team Kinyesi with a differential
pressure gage so that the volume of gas produced by the digester can be determined. A picture of the FloWing Meter is below in Figure 11.
Figure 11. Flo-Wing Meter
7.6 Conclusion
A prototype is being constructed so that the process and parameters of anaerobic digestion can be tested
to see if they are viable for the final design for the pig farm at TGBI. Based on the research and design
work that Team Kinyesi has done throughout the fall semester, this project appears feasible. There have
been other similar projects constructed across the world, and the general process is utilized regularly. The
necessary pieces also seem to be coming together so that it will be possible to construct a prototype
during the spring semester. Consequently, Team Kinyesi is confident in the feasibility of successfully
producing biogas from pig manure in the context of southwestern Tanzania as well as in Grand Rapids,
Michigan.
8. Acknowledgements
Team Kinyesi would like to say a special thank you to all who have provided support in different aspects
of this project. Firstly to Professor Robert Masselink for being our team advisor. Professor Masselink has
been a very encouraging advisor. He asked helpful questions and guided the team’s use of their time and
effort. The team’s industrial advisor, Jeff Friesen, was a great resource for the team. He was helpful in
establishing the team’s scope and current position through skype conversations. His expertise on
biodigestion helped the team understand how paramount certain parts of the digestion process were.
Heather Chapman was the team’s safety go-to person. She was positive and uplifting about the project
from the very beginning. Heather put in a lot of time for the team and made sure that the prototype was
28
safe to build and test. She helped find the location where the prototype will be built and worked with city
municipalities in order to give the team a green light on prototyping. The team would like to say a special
thank you to Steve Sherman (Trevor Sherman’s father) and Mike Caraway for supporting the team and
providing relevant information about the TGBI campus. Thank you Carl Meyer for providing the team
with pig waste for testing the prototype. Thank you Professor David Wunder for supporting the team by
providing valuable resources for research. Thank you Carl Meyer for providing a source of pig manure.
The team struggled to find a source of manure for most of the fall semester and was thrilled with your
willingness to support this design project. This project would not have been possible without the support
from these people.
29
9. References
Calvin College Engineering, [Online]. “About Us - Mission Statement.” Available:
http://www.calvin.edu/academic/engineering/about/mission.html
1
2
“TGBI.” Google Maps. Available:
https://www.google.com/maps/place/8%C2%B010'41.8%22S+31%C2%B051'46.9%22E/@1.8788856,7.
1111989,4.02z/data=!4m2!3m1!1s0x0:0x0
3
Mike Caraway. [Email Correspondence]. 8 October, 2015.
Weatherbase, [Online].“Mpwapwa, Tanzania.” Available:
http://www.weatherbase.com/weather/weather.php3?s=605393&cityname=Mpwapwa%2C+Dodoma%2C
+Tanzania
4
R.A. Almaraz, H. Esweran, S.T. Numbem and P.F. Reich. “Land Resource Stresses and Desertification
in Africa.” USDA - Natural Resources Conservation Service Soils. Web. 24 October, 2015.
5
6
Steven Sherman. [Client Interview]. 12 September, 2015.
David Schmidt. “Anaerobic Digestion Overview.” University of Minnesota - Department of Biosystems
and Agricultural Engineering. PowerPoint.
7
“Eric Degroot Engineering Fund.” ENGR 339 Moodle. Available:
http://moodle.calvin.edu/course/view.php?id=32642
8
Yvonne Vögeli, Christian Riu Lohr, Amalia Gallardo, Stefan Diener, and Christian Zurbrügg.
“Anaerobic Digestion of Biowaste in Developing countries – Practical Information and Case Studies.”
Available:
http://www.sswm.info/sites/default/files/reference_attachments/VOEGELI%20et%20al%202014%20Ana
erobic%20Digestion%20of%20Biowaste%20in%20Developing%20Countries.pdf
9
10
[10] Jeff Friesen. [Industrial Advisor Meeting]. 10 November, 2015.
11
Steven Sherman. [Client Interview]. 15 November, 2015.
12
“Electricity Usage of a Stove Top.” Energy Use Calculator. Web. Available:
http://energyusecalculator.com/electricity_stovetop.htm
“Design Norms Lecture.” Engr 339 Moodle Page - Faculty Lectures. Slides 7-11. Available:
http://moodle.calvin.edu/course/view.php?id=32642
13
“Biogas Digesters for Cambodians.” National Biodigester Program in Cambodia. UNEP. Web.
Available:
http://www.unep.org/ietc/Portals/136/Other%20documents/Other%20projects/Ecological%20sanitation%
20%20Philippines/Case%20studies%20from%20Cambodia/08%20KH_SNV_NBP_Project_Case_Study.pd
f
14
30
15
Doug Hamilton, Waste Management Specialist, Oklahoma State University, “Types of Anaerobic
Digesters” Available: http://articles.extension.org/pages/30307/types-of-anaerobicdigesters#.VkXs3PmrTIU
16
Emmanuel Serna. “Anaerobic Digestion Process.” WtERT – Waste-to-Energy Research and
Technology Council. Available: http://www.wtert.eu/default.asp?Menue=13&ShowDok=12
17
Ann C. Wilkie, Ph.D. “Anaerobic Digestion: Biology and Benefits.” Available:
http://dairy.ifas.ufl.edu/other/files/NRAES-176-March2005-p63-72.pdf
18
http://dairy.ifas.ufl.edu/other/files/NRAES-176-March2005-p63-72.pdf
19
http://www.renewwisconsin.org/biogas/AD/Pathogen%20Reduction%20Article.pdf
Charles Fulhage, Frank J. Humenik, and John M. Sweeten. “Methane Gas From Swine Manure.”
Michigan State University - Cooperative Extension Service. June 1981. Web.
20
21
John Balsam. “Anaerobic Digestion of Animal Wastes: Factors to Consider.” ATTRA. Pg 3, 7. Article.
22
Douglas W. Hamilton, Aimee D. Heald, and William G. Luce. “Production and Characteristics of
Swine Manure.” Oklahoma State University - Cooperative Extension Service. Web.
Available:http://agrienvarchive.ca/bioenergy/download/F-1735_swine_man_char_OK.pdf
23
Jeff Wing. “Biodigester Presentation.” Engineering Ministries International. PowerPoint.
John P. Chastain, James J. Camberato, John E. Albrecht, and Jesse Adams, III. “Swine Manure
Production and Nutrient Content.” Available:
https://www.clemson.edu/extension/livestock/camm/camm_files/swine/sch3a_03.pdf
24
25
http://www.biogasmax.co.uk/media/introanaerobicdigestion__073323000_1011_24042007.pdf
26
http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Biocontrol/AnaerobicDigestion.html
“Anaerobic Digester Upset & Troublshooting.” Aquafix. Available: https://teamaquafix.com/anaerobicdigester-upset-troubleshooting/
28
Charles D Fulhage, Dennis Sievers and James R. Fischer, “Generating methane gas from manure”
Available: http://www.ncbi.nlm.nih.gov/pubmed/16051083
27
Karmin K, Hoffman R, Klasson T, Al-Dahhan MH, “Anaerobic digestion of animal waste: waste
strength vs impact of mixing.” Available: http://extension.missouri.edu/p/G1881
29
30
http://www.myweather2.com/City-Town/Tanzania/Mwanza/climate-profile.aspx?month=2
“Use of Solar Energy to Heat Anaerobic Digesters.” Environmental Protection Agency. Available:
https://drive.google.com/drive/u/0/folders/0B-51JzRKnFu5RjQ5WmRJM2FXOWM
31
32
http://www.asminternational.org/documents/10192/1849770/ACFAA5C.pdf
33
Steven Sherman. [Client Interview]. 4 December, 2015.
34
http://energyinformative.org/solar-panels-cost/
35
Heather Chapman. [Safety Meeting]. 12 November, 2015.
31
36
http://www.amazon.com/Ecosmart-POU-3-5-Electric-Tankless/dp/B0047RAQZG
http://www.alibaba.com/product-detail/induction-tankless-water-heater-waterheater_60164105127.html?spm=a2700.7724857.29.89.aHNMVf
37
38
http://www.alibaba.com/product-detail/tankless-water-heater-midea-water-heater_60322999104.html
39
http://www.alibaba.com/product-detail/electric-instant-water-heater-The-hot_60366108697.html
“New FCI Mass Flow Meter Optimized for Biofuel and Biomethane Applications.” Fluid Components
International LLC. Available:
http://www.fluidcomponents.com/Industrial/News/PressReleases/ST51_Biofuel_%200708.pdf
40
32
Table of Appendices
Contents
Appendix A - Gantt Chart for First Semester ............................................................................................... 1
Appendix B – Gantt Chart for Construction ................................................................................................. 2
Appendix C - Eric Degroot Engineering Fund Proposal .............................................................................. 3
Appendix D – Pig Production Calculations .................................................................................................. 6
Appendix E - Decision Matrices ................................................................................................................... 8
Appendix F – Safety Plan ........................................................................................................................... 11
Appendix G – Industrial Consultant Meeting Notes ................................................................................... 14
G.1 Meeting number one on November 10, 2015 ............................................................................... 14
G.2 Meeting number two on November 30, 2015 .............................................................................. 15
Appendix H – Electrical Heating Controls ................................................................................................. 16
Appendix I – C/N Calculations ................................................................................................................... 18
Appendix J – Heat Exchanger Calculations ................................................................................................ 19
Appendix K – Inventor Drawings ............................................................................................................... 20
Appendix A - Gantt Chart for First Semester
A1
ID
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Task
Mode
Task Name
Duration
Phase 1 Research & scope development
Define teams
Lock down a client
Proposed project
Preliminary research
PPFS outline
Work breakdown structure
Web master chosen
Phase 2 ‐ PPFS
Project brief for industrial consultant
Project website
Project poster
Draft PPFS
PPFS Submitted
Eric DeGroot engineering fund
Presentaion
Project: Gant Chart.mpp
Date: Fri 12/11/15
Start
Finish
29 days
Tue 9/8/15
Fri 10/16/15
4 days
2 days
2 days
21 days
4 days
6 days
Tue 9/8/15
Fri 9/11/15
Fri 9/11/15
Tue 9/15/15
Fri 10/2/15
Wed 10/7/15
Fri 9/11/15
Mon 9/14/15
Mon 9/14/15
Tue 10/13/15
Wed 10/7/15
Wed 10/14/15
8 days
41 days
8 days
Wed 10/7/15 Fri 10/16/15
Sat 10/17/15 Fri 12/11/15
Thu 10/8/15 Mon 10/19/15
8 days
8 days
23 days
19 days
20 days
Sat 10/17/15
Wed 10/28/15
Thu 10/15/15
Tue 11/17/15
Tue 10/6/15
9 days
Wed 10/14/15 Mon 10/26/15
6, '15
M T
W
T
F
S
Sep 13, '15
S M T
Tue 10/27/15
Fri 11/6/15
Mon 11/16/15
Fri 12/11/15
Sun 11/1/15
Task
Inactive Summary
External Tasks
Split
Manual Task
External Milestone
Milestone
Duration-only
Deadline
Summary
Manual Summary Rollup
Progress
Project Summary
Manual Summary
Manual Progress
Inactive Task
Start-only
Inactive Milestone
Finish-only
Page 1
W
T
F
S
Sep 20, '15
S
M T
W
T
F
S
Sep 27, '15
S
M T
Project: Gant Chart.mpp
Date: Fri 12/11/15
W
T
F
S
Oct 4, '15
S
M T
W
T
F
S
Oct 11, '15
S
M T
W
T
F
S
Oct 18, '15
S M T
W
T
F
S
Oct 25, '15
S
M T
Task
Inactive Summary
External Tasks
Split
Manual Task
External Milestone
Milestone
Duration-only
Deadline
Summary
Manual Summary Rollup
Progress
Project Summary
Manual Summary
Manual Progress
Inactive Task
Start-only
Inactive Milestone
Finish-only
Page 2
W
T
F
S
Nov 1, '15
S
M T
5
T
W
T
F
S
Nov 8, '15
S
M T
Project: Gant Chart.mpp
Date: Fri 12/11/15
W
T
F
S
Nov 15, '15
S
M T
W
T
F
S
Nov 22, '15
S M T
W
T
F
S
Nov 29, '15
S
M T
W
T
F
Task
Inactive Summary
External Tasks
Split
Manual Task
External Milestone
Milestone
Duration-only
Deadline
Summary
Manual Summary Rollup
Progress
Project Summary
Manual Summary
Manual Progress
Inactive Task
Start-only
Inactive Milestone
Finish-only
Page 3
S
Dec 6, '15
S
M T
W
T
F
S
De
S
Appendix B – Gantt Chart for Construction
A2
Prototype Construction
ACTIVITY
PLAN
PLAN
ACTUAL ACTUAL PERCENT
START DURATION START DURATION COMPLETE
Period Highlight: 1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
4
8
8
11
9
9
16
19
19
19
19
19
26
30
34
34
36
3
3
4
5
8
8
8
10
10
10
30
10
15
15
12
12
15
10
15
4
5
5
2
5
3
3
3
3
4
5
6
7
4
4
4
6
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
Actual
% Complete
Actual (beyond plan)
% Complete (beyond plan)
PERIODS
1
Clean Out Shed
Get 55 Gallon Drum
Get PVC Bends
Get 5 Gallon Buckets w/ Lids
Get PVC 2in Pipe
Stand Materials (2x4, Stool)
Gets bolts/screws/nuts
Get Gas Line Piping (1in copper)
Get PVC for Heating (.5 in)
Order heating elements
Order biogas flaming cooker
Get pressure release system
Get flow meter
Get Four gas meter
Get temperature sensors
Get ph meter
Get Saw Dust or Straw to Buffer CN ratio
Get valves and calking
Digester insulation
Insulate Shed
Drill Necessary Holes in Drum
Get Electricity Access to Shed
Cut pvc to size
Build heating element
Build digester supports
Instal digester onto supports
Instal heating element
Instal pvc piping into digester
Instal temperater gages
Instal ph meter
Instal gas line exit
Instal pressure release valve
Pressure test digester
Test heating system with water
Connect pvc to inelt and outlet buckets
Instal flow meter/pressure sensor
Reinforce weak connections with fiberglass
Plan
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Instal four gas meter
Instal heating for shed
Complete blood born pathogen trainin
Complete Calvin open flame permit
Put up caution signs and tape
Aquire PPE
Laminate and post emergency contact info
Saftey check with Heather
Begin testing
16
13
10
10
30
10
30
35
40
3
3
15
15
5
15
5
5
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0%
0%
0%
0%
0%
0%
0%
0%
0%
Appendix C - Eric Degroot Engineering Fund Proposal
Team 18 - Austin Kearby, Mitchell Porch, Trevor Sherman, Lucas
Schreiber
Project Description:
There is a bible college, Tanzania Grace Bible Institute (TGBI), in southern Tanzania that currently
prepares food for its students using wood that is collected from the surrounding land. However, wood is a
diminishing resource in the area due to trees being continually cut down. The college is interested in an
alternate way of fueling their burners. The compound currently has a pig barn where they raise between
90 to 150 Landrace pigs. They currently dry out the pig waste and use it for fertilizer. However, we hope
to collect methane from the waste prior to using it for fertilizer.
Our first objective is to assess the feasibility of using pig waste to produce methane as an alternative fuel
for cooking. We will produce methane by anaerobically digesting pig (and possibly human) waste for
TGBI while continuing to use the waste as fertilizer. Our second objective is to establish a system that has
minimal maintenance. Our final objective is to develop and construct a prototype digester to test our
proposed process. This prototype will include external heating and intuitive controls.
Project Budget:
The current budget is based on estimations of costs for the predicted equipment that we will need to
construct the prototype. We have tried to predict for the worst case scenario. Consequently, we will be
trying to reduce our costs in any way possible. Based on our current estimates, our total budget request is
for $2,550. As a result, we are seeking out other grant opportunities to supplement the class funds and the
Eric Degroot Fund. However, support from the Eric Degroot Fund will be greatly appreciated. A table
with our specific budget estimations is presented in Table A1 at the end of the proposal.
Impact on the Community:
The village next to TGBI’s campus is quickly running out of wood, which they use to cook their meals. In
fact, TGBI bought a plot of land to grow a forest so that they could have a wood supply. However, people
from the village regularly sneak in and cut down the trees to use for cooking. With the production of
methane for the TGBI campus, we could lessen their dependence on wood for cooking. Furthermore,
depending on the methane yield, we plan to develop a method of packaging the methane so that TGBI
could sell it to the people living in the neighboring village. This would benefit the college and the people.
A3
Table A1 - Budget Estimations
Item
Concrete
HDPE Liner
Natural Gas Water
Heater
Water to Water Heat
Exchanger
Generator/Gas (This is
may not be needed - it
just depends on the
availability of electricity
where we build the
prototype)
Pump for mixing
Cost per unit/Sources of Info.
From The family handyman - $115/m3. Based on a
2x2x2 meter digester with the walls being 15cm
thick: 3 m^3 of concrete.
$245 for 35’ x 15’ 20 mil hdpe - Ebay
(Natural Gas in Michigan is about $5 per 1,000
ft^3) - Based on Google Results
Based on Ebay
Total Cost
$350
$400 for the Generator. Usually use 12 to 20
gallons of gas per 24 hours - $200-(consumer
reports.com).
$600
http://www.ebay.com/itm/O2-Commercial-AirPump-571-GPH-Aquarium-HydroponicsAquaponics-Fish-Pond/252139140500?hash=item3ab4a9f594:g:zIAAOSw3xJVVarJ
$3.22/10ft - Home Depot
2x4 for construction
Travel Cost To Pig Farm $11/day (for the average car) - 30 days of Travel
Influent Mixing Chamber http://www.globalindustrial.com/p/materialhandling/drum-barrel/drums-pails/plastic-labpack-with-metal-level-lock-30gallon?infoParam.campaignId=T9F&gclid=CKC6
j-3p6MgCFQiraQodtv8GCA
$10 / 10ft. Elbow - $4. (Lowe's)
Piping from Mix to
Digester - 4 in pvc pipe
Blue Rhino Propane Tank Storage tank for biogas
http://www.sears.com/blue-rhino-propane-tank20-lb-standard-exchange/p02722967000P?sid=IDx01192011x000001&gclid
=CPfT4crk6sgCFQ6OaQodC4EN8g
same as influent
Effluent Tank (plastic
bin)
1 bale - $5 - Lowe’s
Straw for Fertilizer
$8/ sheet (42” x 7’)
Metal grating for
structure
Caulking for putting stuff 1 gun ($15), 10 Tubes ($2 each) - Home Depot
together
$10/ 10ft Type L - from Lowe’s
½’’ copper gas line
$20
Plywood
A4
$250
$300
$200
$24
$35
$330
$45
$18
$20
$45
$5
$64
$35
$20
$20
Screws
High strength glass
(pexiglass)
Copper gas line fittings
Mixing air pump
TOTAL
A5
$5
http://www.eplastics.com/Plastic/clear_plexiglass_
sheet/Impact-Modified-Clear-Acrylic-030x24x48
Based on Lowes Copper Fittings $10 for a number
of fitting needs - Lowe’s
big fish tank air pump
$5
$20
$10
$140
$2,537
Appendix D – Pig Production Calculations
Tanzania Grace Bible Institute has anywhere from 90 to 150 pigs at a time. There are four groups of three
mother pigs (sows) that produce litters of about seven piglets on average every seven months. These pigs
then grow for 14 months until they weigh about 100 kilograms before they are sold. The cycle of piglets
is plotted in Figure A1 based on site data. The average number and weight of pigs on the farm at TGBI
can be determined using this data.
Figure A1. Piglets Growth Cycle
As these pigs grow up they produce more manure. These numbers were calculated based on the weights
of the pigs provided by the client. Figure A1 shows the weight of the pigs as they grow over time up to
the point at which they are sold. The maximum and minimum estimates for weight are below.
Criteria Min Max Min Max Live Weight of Pigs (kg) 4731 8558
Live Weight of Pigs (lbs) 10431 18867
From there, there are numerous estimations about the amount of manure that is produced from all of these
pigs. The final number that was used in the estimations for manure production was 4% of the live weight.
That resulted in the following estimates:
Min Max Criteria Min Max Manure Weight (kg/day) 189
342
Manure Weight lb/day
4172 7547
Some resources linked biogas to weight of manure, others tied the biogas to live weight. Both volume and
energy conversion factors are based on the following estimations:
28 ft^3/day/1000lbs swine 16800 BTU/day/1000lbs swine A6
There were also various digester volume estimations. One estimation proposed five cubic feet of digester
volume per pig. Other estimations were based on overseas experience. The results are shown below.
Sizing needs (m3)23 Sizing needs (m3)14 Sizing needs (m3)21 A7
30 20 12.74 60
35
21.24
(Jeff Wing) (Cambodia) (5 ft^3 per pig) Ft3 Ft3 Ft3 1059 706 450 2119
1236
750
Appendix E - Decision Matrices
The team made important decisions with the help of decision matrices. These decisions were based on
multiple criteria with safety being a primary concern for both the final and prototype design. Cultural
appropriateness was a major concern as the team sought to design a digester that was simple and robust
for those who would benefit from it. The matrix also considers how each design item impacts gas
production. The team was on a tight budget so cost was an important driver for making decisions. The
team also wanted to minimize cost for the Tanzania design. The importance of keeping oxygen out of the
digester is paramount. This design item was of utmost concern for the digester design. The volume of the
digester was not a huge driver for the team because space was not an issue in Tanzania. Short circuiting is
when the influent exits the digester prematurely without the volatile solids or pathogens breaking down.
This was an important design item that had an impact on the shape of the digester chosen. The energy
requirements needed to run the digester range depending on the temperature range at which the digester
runs. Stability was chosen to represent how well the temperature could sustain bacterial growth. Bacterial
growth is sustained when temperatures are stable (within 5°F) inside the digester. Operations refers to the
daily amount of effort required to run the digester. The team wanted minimal operations to simplify the
use of the digester. The construction of the prototype was a factor that was taken into account for the
feasibility of building the prototype. Originally the team was going to treat human waste in the digestion
process but this idea was rejected after research explained the extensive testing process. Final design was
used to compare the prototype design to the final design to see how well the two could relate. Pending
cost of safety equipment and sensors the team will plan to use a heating jacket to maintain the temperature
of the digester. If the budget gets too expensive then the team will use the cheaper inductive water heating
system. The different decision matrices as given below.
Table E1. Mixed vs Unmixed Decision Matrix
Category
Weight
Safety
Cultural Appropriateness
Gas Production
Cost
Anaerobic Enviroment
Volume
Total
10
9
7
7
10
4
Mixed Periodically
Score Weighted Score
10
100
7
63
8
56
9
63
5
50
8
32
364
Continuously Mixed
Score Weighted Score
8
80
4
36
10
70
6
42
6
60
10
40
328
Score
10
10
6
10
10
6
Unmixed
Weighted Score
100
90
42
70
100
24
426
Table E2. Shape Decision Matrix
Category
Safety
Cultural Appropriateness
Gas Production
Cost
Anaerobic Enviroment
Volume
Short Circuiting
Total
A8
Weight
10
9
7
7
10
4
7
Dome Shaped
Score Weighted Score
10
100
7
63
8
56
7
49
5
50
9
36
8
56
410
Horizontal Cylindrical
Score Weighted Score
10
100
9
81
8
56
8
56
9
90
9
36
9
63
482
Verticle Cylindrical
Score Weighted Score
10
100
10
90
8
56
8
56
9
90
8
32
6
42
466
Score
10
4
10
4
5
10
8
Egg Shaped
Weighted Score
100
36
70
28
50
40
56
380
Table E3. Temperature Decision Matrix
Category
Weight
Safety
Cultural Appropriateness
Gas Production
Cost
Energy Requirments
Stability
Volume
Total
10
9
7
7
7
8
5
Psychrophilic
Score Weighted Score
10
100
10
90
3
21
10
70
10
70
1
8
4
20
379
Score
9
8
8
6
7
9
9
Mesophilic
Weighted Score
90
72
56
42
49
72
45
426
Thermophilic
Score Weighted Score
8
80
6
54
10
70
4
28
3
21
8
64
10
50
367
Table E4. Digester Type Decision Matrix
Category
Weight Continuously Mixed Flow
Score Weighted Score
Safety
10
9
90
Cultural Appropriateness
9
8
72
Gas Production
7
8
56
Cost
7
8
56
Energy Requirments
7
8
56
Operations
8
9
72
Volume
4
7
28
Total
430
Score
9
7
8
8
7
7
9
Plug Flow
Weighted Score
90
63
56
56
49
56
36
406
Score
9
8
3
10
9
5
6
Batch
Weighted Score
90
72
21
70
63
40
24
380
Table E5. Addition of Human Waste for Prototype Decision Matrix
A9
Category
Weight
Safety
Cultural
Appropriateness
Gas Production
Cost
Pathogen Testing
Final Design
Operations
Total
10
9
5
7
9
7
7
No Human Waste
Score Weighted Score
10
100
8
7
8
10
3
9
72
35
56
90
21
63
437
Human Waste
Score Weighted Score
7
70
7
8
6
5
8
7
63
40
42
45
56
49
365
Table E6. Construction of Prototype Decision Matrix
A10
Category
Weight
Safety
Anaerobic Environment
Cost
Final Design
Construction of
Prototype
Operations
Total
10
8
7
8
7
7
Heated Jacket
Score Weighted Score
10
100
10
80
6
42
5
40
10
10
70
70
402
Inductive heating
Score Weighted Score
9
90
9
72
10
70
7
56
7
6
49
42
379
Appendix F – Safety Plan
Personal Protective Equipment (PPE)
A list of personal protection equipment that is needed by the team is following: gauntlet-style liquid-proof
gloves; liquid-resistant Tyvek suits; safety goggles; safety glasses; face shields; and closed-toed shoes.
The gloves, Tyvek suits, safety goggles, and face shields will be provided by Calvin College. Each team
member must provide appropriate closed-toed shoes.
PPE Required by Task





Collection of waste: Currently, Carl Meyer will be collecting the waste. If the team collects the
waste, they will wear gauntlet gloves, Tyvek suits, safety goggles, face shields, and if deemed
appropriate, shoe covers.
Handling of sealed collection buckets: Gauntlet gloves
Mixing of waste: Gauntlet gloves, Tyvek suits, safety goggles, face shields, and if deemed
appropriate, shoe covers.
Transfer of waste into chamber: Gauntlet gloves, Tyvek suits, safety goggles, face shields, and if
deemed appropriate, shoe covers.
General work done in shed: Safety glasses
Collection Process
The team will be collecting the waste in sealed five gallon buckets. The farm currently has a safety plan
that requires the farmer, Carl Meyer, to collect the waste himself. Consequently, we will not directly
handle the pig manure during the collection process.
If we are permitted to collect the waste ourselves, we will follow the collection procedures implemented
by Carl Meyer.
Mixing Process
The team plans to add one part water to one part manure. We plan to add approximately two gallons of
manure per day to the digester. Therefore, the team will be mixing the manure with approximately two
gallons of water. This mixing will be done in the five gallon bucket, and must be done carefully because
of the high splash risk.
Due to the odor contamination. The mixing will be done at the farm. To protect the mixer, they will be
wearing the appropriate PPE, which includes a Tyvek suit, tall gloves, safety goggles, face shields, and
closed toed shoes.
Transportation Procedure
The manure slurry will be transported in the sealed five gallon buckets. The buckets will be transported
in the vehicles owned by the team members. In order to prevent any manure from getting in the cars and
to reduce odor, the five gallon buckets will be sealed and placed in cardboard boxes lined with Visqueen.
These boxes will be used only for transportation of the manure bucket. The boxes that house the five
A11
gallon buckets will be transported in the trunks of the vehicles to prevent any risk of asphyxiation and
further reduce the smell in the cars.
Building Entry Procedure
Due to risk of asphyxiation, entering the shed must be done using extreme care. There will be one of two
gas composition measuring devices inside the shed at all times. The first option is to use a four gas meter
(which Calvin owns). The four gas meter will run constantly and will be attached to the inside of the shed
door. When the gas meter detects high levels of hydrogen sulfide or methane, or low levels of oxygen, an
alarm will sound. If the alarm is ringing, team members must not enter the shed and must contact
appropriate emergency personnel. The list of emergency contacts is presented below in the emergency
contact list. This list of emergency contacts will be laminated and posted outside the shed. If the four gas
meter is not ringing, team members may open the door cautiously and check the four gas meter to make
sure it is operating properly.
The second option is to use the measurement device provided by agile safety. The display for the device
will be available outside the shed and the team members must check the air composition inside the shed
before entering. If there does seem to be an issue with the gas levels inside the shed, the appropriate
safety personnel must be contacted as explained above.
When the gas detection system is decided, an updated safety plan will be provided in order to specify a
more accurate procedure for entering the shed.
Site Protection Plan
In order to ensure that no unauthorized personnel enter the shed where the digester prototype is housed,
warning signs will be posted 50 feet away from the door where possible and a lock will be placed on the
door. Where there are buildings closer than 50 feet, the signs will be posted in the most visible location
for those who would be walking in the area. The signs will read “WARNING! Combustible, Pressurized
Vessel inside Shed. Do Not Enter.” These signs will also be posted on the doors of the shed.
The shed will also have appropriate ventilation so as to release any toxic gasses that accidentally escape
the digester. Currently, there are numerous holes in the shed. These will act as ventilation to the outside
atmosphere.
Furthermore, due to risk of methane presence in the shed, there must be no sparks or open flames inside
the shed (this includes cars, snow blowers, and grills). Therefore, the heating method that is used must be
intrinsically safe, utilizing no open flame. This will be satisfied by using an induction water heater.
Feeding the Digester
While transferring the manure to the digester, team members will be wearing the PPE presented above to
avoid any contact with the slurry that might come from sloshing. The inlet bucket will be opened and the
manure slurry will be poured from transportation bucket to the inlet bucket. Then both buckets will be
closed to prevent manure contact and odor. Visqueen will be laid on the ground to contain any spilled
slurry from directly contacting the shed flood.
All team members will also participate in Blood Born Pathogen Training before any pig-manure is
handled.
A12
Gas Production and Use
The biogas that is produced by the digestion process is combustible. Consequently, it must be handled
appropriately. It will be piped outside the shed with PVC piping where it will be flared using a campstove. PVC piping is used over copper piping because the trace H2S gas that could possibly be produced
is highly corrosive and could corrode copper piping. PVC is also a cheaper option. In order to have an
open flame on campus, the team must complete an open flame permit. This is a Calvin permit that must
be completed before the digestion process can begin.
Although, the pressure build-up in the digester should be minimal, there will be a pressure release valve
inserted into the barrel to ensure that explosive pressures are not reached inside the drum. The pressure
release valve will release when the pressure inside the digester reaches six psi because 55 gallon drums
are known to start bulging when the internal pressure reaches six psi [A1]. If the pressure is released at six
psi, there will be no risk of explosion.
[A1] http://www.eetcorp.com/products/press_drum.pdf
Emergency Contact List
Emergency Contact
Contact Information
Campus Safety
616-526-6452
Heather Chapman
616-526-8591
IF DEEMED NECESSARY BY CONTACTS ABOVE:
Fire Department
911 (this will be updated by the fire department)
Ambulance
911
Police
911
A13
Appendix G – Industrial Consultant Meeting Notes
G.1 Meeting number one on November 10, 2015
Meeting with industrial consultant Jeff Friesen
We expressed our goal: gas to cook 40 - 60 meals per day.
A question that Jeff brought up - What about excess gas? Does that mean there will be a buildup
of pressure?
We talked about heating
Jeff was concerned about siloxanes. Siloxanes come from human waste like makeup and
cosmetics and processed food. On second thought, Jeff is not as concerned because we are not going to be
running it through moving parts. Siloxanes are more of a concern for engines.
We discussed the production H2S and that it is a health concern.
Currently there is a hydroelectric turbine on site that produces 23kw and TGBI uses 5kw to 8kw.
We discussed the kind of reactor that we could use. Either plug flow, batch, or cmfr.
Jeff recommends we analyze and pursue plug flow reactors.
Jeff recommended that we Investigate the effects of putting foreign objects into the digester (I.E.
dirt stones and other things)
We talked about local sources of waste
We asked about scale down factor. Both Jeff and us need to research more.
We asked if we need a way to control pressure -- Jeff said that that is getting ahead of ourselves.
We asked about collecting gas. Again, Jeff said it is ahead our where we are.
We asked if mixing is necessary in a plug flow reactor?
We asked about how to keep out oxygen? Jeff says that we need a liner.
We need to investigate what liners can we get in Darsalam - in the spring.
Construction of the digester is the biggest thing to think about.
Some examples are how to keep oxygen out and how to keep the temperature at mesophilic.
Jeff questioned how we would fix something if there was a problem without killing the whole
thing.
There are not any quick fixes.
We talked about making the prototype.
We established that we need to be able to test the prototype and we talked about using pvc pipe.
We discussed when to talk next. We decided to meet in two weeks on the Monday before
Thanksgiving.
We sent him a google meeting invite (Google calendar)
He works for an engineering company in Oregon
He does not recommend using the gas to power an engine because it is outside the scope of the
project.
A14
G.2 Meeting number two on November 30, 2015
Meeting with industrial consultant Jeff Friesen
We asked what his thoughts were on mixed flow vs plug flow and said we would like to pursue a
digester that is not mixed mechanically.
Some questions that Jeff posed – Will the digester be buried in Tanzania? How will the digester
be sealed?
We talked about this and started to think about using large plastic sim tanks available in
Tanzania.
A question that Jeff posed – How will you know if your system is failing or not? What happens if
the temperature starts to drop too low in the digester?
Lucas said he could use the Raspberry pie hardware to text us if the change in temperature within
the system was too great. This would give us a chance to respond to the failure and save the system.
We talked about needing to heat the shed as well.
Jeff suggested building a mini digester out of something like a 2-litre bottle.
Jeff talked about how corrosive the H2S in the slurry is. Be careful with metal inside of it.
Jeff talked about thermo wells as protection agents between the slurry and the thermocouples.
Jeff suggested for the TZ design to heat the digester with some of the gas that it produces. He said
there needs to be a way of heating the digester before it is producing gas. He said a good source would be
to use a gas bomb which is available for purchase in TZ.
We talked about materials that are good for heat exchange for the heat exchanging system within
the digester in TZ.
A question we posed – What type of sensor package does Jeff use and how does he keep it water
tight?
Can we control the heating system purely via a mechanical system rather than using electronics to
keep the system simple?
Jeff said he may be able to provide our team with some flow measuring devices. If he does, all
the hardware fits into a 1” piping. He was talking about a differential pressure gauge.
A question Jeff posed – Can you seal the container that you carry the manure in for
transportation?
A question Jeff posed – What materials will you use for your final design? The prototype is okay
because it is for a short period of time but if you want it to last 20 years then the materials must be
considered.
A15
Appendix H – Electrical Heating Controls
The prototype design assembly plan for the heating and control systems is as follows.
1.
Test the code for control system on the Raspberry Pi and check that alerts still work and
control outputs will switch desired devices.
2.
Check induction hot water heater to see if it works on breakers available near shed. If this
does not work, contact campus safety to see if the team can get a better energy source.
3.
Calibrate the sensor and then insert sensor packages into barrel.
4.
Assemble heat exchanger pipes for size of barrel with 12 feet of piping inside of the
barrel located under the waterline.
5.
Check the barrel for air tightness.
If not airtight then add calking till test confirms that the system is airtight.
6.
7.
Move barrel to engineering building to confirm heat exchanger piping and heat loss from
barrel equations are correct and if not return to step 4 and make adjustments to piping as
necessary.
8.
If barrel is heated correctly begin soldering sensor packages removable to Raspberry Pi.
Check that all sensor data is inputted correctly to Raspberry Pi in both input pins and
9.
voltage readings.
Check that Raspberry Pi data alters are correct with sensor inputs and disconnection
10.
alters happens.
Read over Material for induction heater for On/Off switches and internal thermostats.
11.
12.
Solder controller switch to be in parallel with switches on induction heater and check that
both need to be logic high (depends on device see step 11 if confused) to turn device on.
13.
Connect Raspberry Pi to control switches temporarily.
14.
Check entire system again for loose wires and piping connections.
While still in engineering building run through control systems tests and confirm system
15.
work for all functionality, if not fix where necessary.
Raspberry Pi internet connectivity via either wifi or ethernet
a.
Raspberry Pi alters for sudden drop in temp
b.
c.
Raspberry Pi disconnection alter from all devices
Daily call outs
d.
Raspberry Pi heating control
e.
f.
Raspberry Pi temperature drop response for heater
Disassemble temporary connections and prepare for transport to shed.
16.
17.
Check induction hot water heater works on breakers available near shed and if not modify
within state code until works or find long extension cable and better spot.
Then weatherproof extension cables and/or ethernet cables with pool noodles, choose
18.
flashy color to be seen at night or on snow.
19.
Move digester, control, and heating systems to shed.
20.
Reassemble digester, control, and heating systems.
Check induction water heater is working.
21.
22.
Run through control systems tests and confirm system work for all functionality, if not
fix where necessary.
a.
Raspberry Pi internet connectivity via either wifi or ethernet
Raspberry Pi alters for sudden drop in temp
b.
c.
Raspberry Pi disconnection alter from all devices
d.
Daily call outs
Raspberry Pi heating control
e.
f.
Raspberry Pi temperature drop response for heater
A16
23.
Begin testing digester parameters and start initial retention time.
Each of the inductive hot water heaters will be wired into the control system via the GPIO ports
of the raspberry pi and the switches on the hot water heaters themselves.
A17
Appendix I – C/N Calculations
Density of water (lbs/ft^3) Gallon 1 C/N Ratio Pig Manure Saw dust Desired gal/day ft^3/day 1.08 0.144375 C/N Ratio Pig Manure Corn Straw Desired percent added 7 200 20 0.93 0.07 6.51 14 20.51 Pounds of pig manure added per day 9.0
Pounds of sawdust added per day 9.69 0.7
percent added 7 60 20 0.75 0.25 5.25 15 20.25 Pounds of pig manure added per day 9.0
Pounds of sawdust added per 12.012 day 3.0
A18
62.4 Cubic Foot 7.48052 Appendix J – Heat Exchanger Calculations
As shown in Table J1, piping was compared on cost, size and conductivity. Equation 1 was used to
calculate the heat transferred into the digester by each type of piping. The results of this calculation is
found in the second part of Table J1.
2∗
∗
∗
Equation 1
ln
Table J1. Comparisons of pipe on cost, size, and conductivity
Heat
Inside Outside
Wall
Fittings Heat
Length
Material Properties Conductivity Cost Diam Diam Thickness Cost Transferred in Transferred in needed
Material
Copper
Cast Iron
[BTU/hr*ft*F] [$/ft]
231
[in]
[in]
[in]
[$]
1.41
0.5
0.625
0.125
0.61
0.8
0.622
0.84
0.218
0.527 0.602
0.84
0.238
[Btu/(hr*ft)]
[W/m]
[ft]
24.6
25.5
4.66
2.34
18.6
19.3
6.16
0.36
14.9
15.5
7.70
46.33
1% Carbon Steel
24.8497
PVC
0.109801
The heat loss of the drum also had to be calculated. This is shown in Table J2.
Table J2. Properties of drum and heat loss calculations
Heat loss from Drum to outside
A19
Property Units
Length
Diameter
Surface Area
Inside Temp
Outside Temp
k for Polypropylene
49.74
32.38
5059.79
90
50
0.09
[in]
[in]
[in2]
[°F]
[°F]
[btu/(hr*ft*°F)]
Heat loss by barrel with Insulation
27.3
[Btu/(hr*ft)]
Total Loss
114.7
[Btu/(hr*ft)]
Appendix K – Inventor Drawings
A20
A21 A22