2008
Jeff De Jong, Bethany Kortman, Jeena Velzen
Calvin College Engineering
12/12/2008

The project goal is to design a simple low cost process to create fuel from waste material, bringing justice to the people of Malawi by increasing the availability of fuel and reducing the effects of deforestation. The fuel making process is low cost and simple to implement with the intent of having wide adoption providing fuel, reducing waste, and creating jobs in developing nations. Ideally, the design will be functional for paper products and other carbon based waste such as agricultural waste.
The intended power source for this project is human work which incorporates design elements such as gears and chains which can be scavenged from bicycles or other available materials in the area, aiding in the cultural appropriateness of the design. By creating a people powered process, the design will provide jobs for individuals within the context of the project with the possibility of selling the fuel product for a profit.
As the feasibility study was carried out for this project, the device inputs were expanded past waste paper to include a grass local to Malawi called sekera grass which is burned off the fields at the beginning of each growing season. The initial design for the fuel processing device implements human power transmitted through gears and chains to provide the power for shredding the input materials, mixing the paper and grass with the binding agent, compressing the materials into fuel briquettes, and drying the fuel product. The material shredding component is a paper shredder, and the mixing component is a drum mixer. The compressing component of the design is a screw extruder, and the drying component is a combination of a solar heat collector and a blower.
Cost and process feasibility have been analyzed through research and experimentation for the initial design and the project objectives. Through this analysis it was determined that the project goals are feasible within the two budgets considered—the Senior Design budget and the
Malawian budget. The design and construction of the prototype is expected to cost $225. The product goals were also determined to be feasible in that a high quality fuel briquette can be produced with the initial process and component design. i

1 Introduction ............................................................................................................................... 1
1.1
Team Description ............................................................................................................... 1
1.2
Problem Statement .............................................................................................................. 2
2 Design Considerations ................................................................................................................ 3
2.1
Project Objectives ............................................................................................................... 3
2.1.1
Purpose of Design ....................................................................................................... 3
2.1.2
Cost ............................................................................................................................ 3
2.1.3
Reliability ................................................................................................................... 3
2.1.4
Scope .......................................................................................................................... 3
2.2
Design Norms ..................................................................................................................... 4
2.2.1
Stewardship ................................................................................................................ 4
2.2.2
Justice ......................................................................................................................... 4
2.2.3
Cultural Appropriateness .............................................................................................. 4
2.2.4
Safety ......................................................................................................................... 4
3 Project Organization ................................................................................................................... 5
3.1
Schedule ............................................................................................................................ 5
3.1.1
List of Key Milestones, Fall Semester ........................................................................... 5
4 Feasibility Study ........................................................................................................................ 6
4.1
Fuel and Process Options .................................................................................................... 6
4.1.1
Material Input ............................................................................................................. 6
4.1.2
Fuel Product ................................................................................................................ 6
4.1.3
Process Options ........................................................................................................... 7
4.2
Components ....................................................................................................................... 8
4.2.1
Shredder ..................................................................................................................... 8
4.2.2
Mixer .......................................................................................................................... 8
4.2.3
Compressor ................................................................................................................. 9
4.2.4
Dryer .......................................................................................................................... 9
4.2.5
Burner ...................................................................................................................... 10
4.3
Power Source ................................................................................................................... 11
4.3.1
Internal Combustion Engine ....................................................................................... 11
4.3.2
Electricity ................................................................................................................. 11
4.3.3
Renewable Energy ..................................................................................................... 11
4.3.4
Human Power ........................................................................................................... 11
4.4
Transmission .................................................................................................................... 12
4.4.1
Hydraulic .................................................................................................................. 12
4.4.2
Linkage ..................................................................................................................... 12
4.4.3
Gear and Chain .......................................................................................................... 12
4.5
Experiment ....................................................................................................................... 13
5 Preliminary Design ................................................................................................................... 14
5.1
Decision Matrices ............................................................................................................. 14
5.1.1
Process Decisions ...................................................................................................... 14
5.1.2
Component Decisions ................................................................................................ 15
5.1.1
Sensitivity Analysis ................................................................................................... 15
5.2
Description of Design ....................................................................................................... 16
ii

6 Budget ..................................................................................................................................... 19
6.1
Senior Design Budget ....................................................................................................... 19
6.2
Malawian Design Budget .................................................................................................. 19
7 Future Work ............................................................................................................................ 21
7.1
Component Design ........................................................................................................... 21
7.2
Communication ................................................................................................................ 21
7.3
Prototype Construction ...................................................................................................... 21
8 Conclusion .............................................................................................................................. 22
Figure 4.1
Methods for Charcoal Creation: the (a) Direct and (b) Indirect Methods. ............... 10
Figure 4.2
Experiments of the (a) Direct and (b) Indirect Methods ........................................... 13
Figure 5.1
Preliminary Process Diagram .................................................................................... 17
Table 5.1
Decision Matrix for Process Design Variables ........................................................... 14
Table 5.2
Decision Matrix for Component Design Variables ..................................................... 15
Table 5.3
Design specifications .................................................................................................. 17
Table 6.1
Preliminary Senior Design Budget.............................................................................. 19
iii

The country of Malawi is among the top 10 poorest countries in the world. Numerous organizations invest time and effort into aiding the people of Malawi—meeting their basic needs such as water, food, shelter, healthcare, and many other essentials. Despite these efforts, the country of Malawi is still in great need. Currently, deforestation is an increasing problem in rural areas of Malawi, as the demand for charcoal fuel requires more resources than are available. This is a very unsustainable, temporary, and environmentally damaging solution.
As a team of aspiring Christian engineers, Re-Fueled (one of fifteen Senior Design groups) has taken on this design project based on a desire for addressing environmental problems and using gifts and talents to aid the developing world. In working with Larry McAuley, a Malawi based member of Christian Reformed World Relief Committee, the team will gain a more culturally specific understanding of Malawi. The need for inexpensive fuel in Malawi requires a solution which Re-Fueled has set out to define.
1.1
Team Description
Re-Fueled is composed of three senior Calvin College engineering students in the mechanical concentration: Jeff De Jong, Bethany Kortman, and Jeena Velzen.
Jeff De Jong grew up in Glendale, California where he has worked as a swim coach at the local country club. Jeff intends obtain a degree in both engineering and business information systems. He enjoys working on his computer as well as riding and repairing his two motorcycles. After graduation, Jeff intends to return to California to pursue a career in automotive engineering.
Bethany Kortman was raised in Grandville, Michigan where she attended
Calvin Christian High School. She has received an international designation to her degree for her participation in an internship for Solvay
Pharmaceuticals in Weesp, Netherlands and an interim abroad. Bethany plays lacrosse and enjoys cycling. She also enjoys outdoor recreation including hiking, climbing, and camping. After graduation, Bethany hopes to work abroad for a few years and then settle down at an architecture and engineering firm in the West Michigan area.
Jeena Velzen was raised in Jenison, Michigan and worked for Gentex
Corporation, as well as participated as a leader for a Wilderness Orientation
Trip and resident assistant position for the Entrada Scholar’s Program.
Jeena is a member of the Calvin Swim and Dive Team as a 1 and 3 meter springboard diver. After graduation, Jeena hopes to pursue a MBA in international business while working internationally.
1

1.2
Problem Statement
Living requires fuel. Even in the most rustic and primitive areas of the world, fire is required to cook food and to provide heat. In many developing countries where electricity is not widely available and fossil fuels are too expensive, wood is the primary source of fuel. Malawi is a country of particular interest which has been ravaged by its people, stripping its landscape of forests to produce charcoal.
Malawi is a country the size of Pennsylvania in southeastern Africa, with a population slightly larger—nearly 14 million. A large majority, roughly 85%, of Malawians are poor subsistence farmers living in rural Malawi
1
. A very shocking comparison shows the per capita GDP of
Malawi is $800 compared to Pennsylvania’s of greater than $40,000. Malawi is currently experiencing massive deforestation to provide fuel for its people. Homemade charcoal from trees is illegal because of the deforestation; however, the problem persists. These circumstances present a need for an inexpensive fuel source which does not encourage the environmentally damaging process of providing fuel which is currently destroying the Malawian landscape.
Re-Fueled seeks to design a process and mechanism which can provide an affordable fuel made from materials which would otherwise be wasted. Keeping the Malawian people in mind as the end users, the design will be bound by considerations for the culture and circumstances surrounding Malawi.
1 CIA World Factbook (www.cia.gov)
2

When confronting a stated problem, proposed designs must be fashioned from objectives which are intrinsic to the problem statement. In addition, these designs are defined by norms which are specific to the designer. The following sections will layout multiple objectives of this design project.
2.1
Project Objectives
There are a number of objectives that have been deemed to be important to consider in the design. These objectives are taken into account when making design decisions.
2.1.1
Purpose of Design
The purpose of this project is to use available scrap materials within Malawi for the design and construction of a process to convert waste material to an inexpensive fuel source for cooking and heating.
2.1.2
Cost
Minimal cost is a primary objective in the design of a functional mechanism for producing fuel from waste in a developing country. The Senior Design budget is $300 per project; however, the Malawian salary is an average of $160 per year. The materials needed to construct this mechanism will be chosen from recycled and previously used scrap parts of bicycles and other parts that are available in Malawi. The intention of reusing parts is to significantly reduce the cost of the machine, as well as helping waste materials to serve another purpose.
2.1.3
Reliability
Reliability is an important objective because of the cultural differences between Malawi and the United States. A “fix it” mentality cannot be assumed for the individuals who will be the end users of the mechanism. Over time, if the mechanism breaks, the design must be simple enough so a large range of people could repair it. The design of this mechanism will focus on being very simple to understand, but also to be able to withstand frequent use without breaking down or needing repair. Although the simplicity of design aims to enable operators to repair the machine, reliability is of primary importance.
2.1.4
Scope
The scope of this design project is a very important objective which must be defined.
Although there are many possibilities for the production capacity of this design, the scope must be limited to fuel a small community. The finished project could prove to be viable for a small business, but the intent of the design is to produce enough useable fuel in one operating period for a week’s worth of fuel for a single family.
3

2.2
Design Norms
In addition to typical project objectives, there are a number of design norms which tie into the ethical, and more specifically Christian, perspective for the design of this project. Christian engineers are called by God to adhere to higher standards, which they incorporate, by their faith, into their design.
2.2.1
Stewardship
The team name, Re-Fueled, is derived from the team’s desire to design a solution from readily available materials that would otherwise be wasted. The current problems of deforestation
2
within Malawi can be offset by this design which converts waste—using a machine made of re-used components—to useable fuel. Reusing components and reducing the damage caused by unsustainable deforesting are all aspects of being
Christian stewards of God’s creation and being responsible caretakers of the earth and its resources.
2.2.2
Justice
There are many inequities within societies; this design seeks to bring justice to areas like
Malawi where individuals and families struggle to afford fuel to cook food and heat homes. Everyone should have the right to a job in order to work hard and earn a living.
By aiming to supply jobs and provide safe inexpensive fuel, this design will work toward justice on the very basic level of fulfilling some needs for God’s people.
2.2.3
Cultural Appropriateness
The design for this project must agree with the culture and environment of Malawi.
Considering materials that can be easily acquired for a low cost in the area will aid in achieving this goal. Also, in order for the device to be accepted and easily adopted, the machine must be very simple to assemble, use, and repair. By keeping the use of materials limited to locally available scrap and making the device simple, this project will make cultural appropriateness a priority. Larry McAuley will act as a liaison, communicating the needs and concerns of the theoretical Malawian end users, to help the team be as immersed as possible in the Malawian culture.
2.2.4
Safety
A device and process to bring cooking and heating fuel to homes would be obsolete if it also brought harm to the people operating the device and using the fuel product. There are many factors in this process that could cause harm to a person. All components must be designed so there are no harmful features, or else safety precautions designed into the mechanism. If input material is found as litter on the streets, it is important that possible toxins are determined and taken into consideration for the design. Consistency of the fuel is also necessary to avoid unpredictable burning, for the safety of the end user.
2 CIA World Factbook (www.cia.gov)
4

Planning is extremely important when undertaking any project. As this project spans two semesters it was imperative to create a plan and work from that plan.
3.1
Schedule
A Gantt chart was used throughout the fall semester to schedule work to be completed
(Appendix A). This includes all deliverables required by Senior Design and additional steps required for the preliminary design and feasibility test of the project.
3.1.1
List of Key Milestones, Fall Semester
The following is a list of significant project milestones that have been achieved in the preliminary feasibility design process.
September 29 Initial Project Objectives Defined
October 13 Project Website Startup
October 24 First Class Presentation
November 17 Project Proposal and Feasibility Report Draft Due
December 5 Final Class Presentation
December 12 Project Proposal and Feasibility Report Due
5

The physical aspects of the process and the mechanism need to fit within the physical and project constraints and consider the design objectives and norms. The potential input materials, output products, conversion processes, and components are considered in this section.
4.1
Fuel and Process Options
4.1.1
Material Input
There are multiple materials to consider as an input to a useable fuel production design.
Other engineers have designed processes to produce fuel from waste paper, wood, sugar cane, and other agricultural waste.
Other individuals proposing designs to meet the fuel needs of Malawi have used paper as a potential waste material which can be converted to fuel. Paper littering is a problem in
Malawi, which means that it is an available resource which would otherwise be wasted.
Paper is made from trees which makes it a feasible option for cooking and heating. The majority of Malawians live in rural areas, making paper a plentiful resource but possibly only in urban areas. Other considerations for paper include a higher burning temperature, faster rate of burning, and possible pollutants on the paper.
Agricultural waste such as grass are feasible sources for fuel because they are plentiful in many areas of Malawi. The sekera grass of Malawi grows between 2-3 meters in height and is burned to clear fields for planting. Sekera grass is only available in the dry season, which limits the source of input material during this time. Burning grass only emits alkaline gases, which help to mitigate acid rain.
4.1.2
Fuel Product
Charcoal is a very valuable resource for providing heating and cooking for domestic use.
The benefits of charcoal include the following: lower burning temperature, slower and cleaner burn, fewer ash remains. Charcoal is currently being used in Malawi as the primary fuel source. Despite its advantages charcoal production from trees is currently illegal in Malawi.
A fuel briquette is an option which comes from the compression of an input material and binding agent, which is then dried and subsequently used as fuel. The process to make a fuel briquette is simpler than the process needed to turn the input material into charcoal.
This method saves time; unfortunately it increases the burning temperature of the fuel and leaves more ash. However, the excess ash from this fuel briquette could be returned to the earth and used to fertilize the soil. In addition, a fuel briquette could be made of mixed inputs such as paper and grass. Consistency is important in a mixed fuel briquette in order to provide a product with a consistent heat output and burning temperature.
Consistency is also important in the intermediate steps to assure reliable and long lasting operation of the components used in the design.
6

4.1.3
Process Options
Many options were considered for the conversion of waste material to a useable fuel product. The ideas for the design process were formulated concurrently with fuel product feasibility testing (section 4.5).
There are many different potential components to incorporate into the optimal design.
Despite the selected fuel product, there are optional components such as a feeder or hopper for material inputs to be inserted into the process. A shredding component may be necessary to provide a more consistent fuel product. A mixing unit would be incorporated if a binding agent is added to the process and greater consistency was needed to combine the fuel product into a burnable product. A dryer and compressing unit would also be necessary to produce dense, compact product that burns easily.
Assuming a charcoal fuel product, the process requires a burner component. Both the direct and indirect burning methods were considered (section 4.2.5). Possible charcoal specific processes are shown below:
1.
feeder

mixer

compressor
 dryer

(in)direct burner

compressor
 dryer
2.
shredder

(in)direct burner

mixer

compressor
3.
(in)direct burner

compressor
Assuming a compressed fuel briquette, a burner component is not required. However, many similar components are necessary, which can be powered manually or mechanically. Fuel briquette processes are shown below:
1.
mixer

compressor

dryer
2.
shredder

mixer

compressor
3.
shredder

mixer

compressor

dryer
4.
shredder

dryer

mixer

compressor
The first listed briquette making process is the most commonly used process. There are small manually powered compressing units available that compress a paper-water mixture into briquettes that are dried and burned. A more complex process is required for a higher production capacity.
The processes are very similar with subtle differences, but the selected components and order of those components will determine the quality of the product and the ease of production.
7

4.2
Components
Each process option is comprised of a number of individual components. Many viable options for each of the individual components are examined and analyzed to make informed design decisions.
4.2.1
Shredder
There are many advantages for a shredding component. Smaller shredded inputs require less power for a drying component due to an increase in surface area of the inputs. There are various options for a shredding mechanism including a blender or food processor blade, a lawn mower blade, or a paper shredder design.
A blender or food processor blade mechanism may not work depending on the weight of the input material. Although salvaging these components would be ideal, food processor parts are not available in Malawi. Also, the blades are very small for the desired production capacity of this design, which would require a large number.
A lawn mower blade would be a large enough component for the desired production capacity for the design; however, feasibility of cutting paper with this blade is questionable. The types of lawn mower blades commonly used in the U.S. are a rare find in Malawi. The possibility exists for construction of a spinning blade similar to a lawn mower blade using more available cutting devices (like a scythe).
A paper shredder design, two parallel rotating drums covered in blades, would cut paper into useable strips, however a commercial sized paper shredder may be difficult to acquire and a domestic-use sized shredder may be too small. Feasibility for this component will depend on the ease of constructing an adequate substitute.
4.2.2
Mixer
Using a mixing component provides a stage at which to add a binding agent. In addition, a mixing component assures the intermediate product is consistent in both composition and coverage of the binding agent.
A paddle or blade mixer stirs the intermediate product in order to achieve the required consistency. The stirring implement could vary from being a set of paddles to being a set of blades. A major obstacle to this design is scaling the mixer to the necessary size for the specified task.
A drum mixer consists of a rotating drum in which the intermediate products and the binding agent are mixed. The drum can include vanes on the inside of the drum to increase agitation during the mixing process. This type of mixer design is much easier to scale for different sized applications.
8

A starchy binding agent is necessary to join the materials for a homogenous product. A number of food starch options include wheat, corn, potato, and cassava. Availability of the food type will determine the selection of a particular binding agent.
4.2.3
Compressor
A compressing unit is necessary to compact the products so that the fuel can be distributed in a solid form without crumbling and also to slow the burn.
A screw drive compressor using a power screw to compress material is an option, however it lacks in range of motion. The screw drive compressor requires rotational force to compress effectively while also requiring force to unscrew to compress again, which takes time and effort.
Currently, linkage compressors can be purchased which use leverage to compress a fuel mixture. This type of compression requires significant human powered input and must be repeated frequently to produce a large amount of compressed briquettes.
Hydraulic compression, like that used in automobile braking systems, is an effective method for compression but requires hydraulic fluid and is a complex system for the developing world, which is an added complexity to the design.
A screw extruder method of compression is an appropriate option because it serves as a continuous method for compressed product extrusion. The cost of creation and complexity of an extruder will determine its feasibility.
4.2.4
Dryer
A drying component is necessary for the design because a fuel product of high moisture content will not burn adequately. Moisture in the product could be due to input material of high water content, the moisture from the selected binding agent, or both. Forced convection of ambient or warmed air and solar radiation are all methods of drying material.
A blower, such as a spinning fan, is an option for drying the material using forced convection of ambient air. Fan blades are available from urban Malawi. This design would be simple to implement because a hand crank or foot peddling method could easily drive this device.
A hot air blower would be an effective method of drying the material; however it requires an input of fuel to create hot air to blow on the damp materials. This increases cost and decreases the overall efficiency of the entire process when comparing input and output fuels.
9

Solar drying is a readily available option for drying the fuel product because it is free, however the weather determines when drying can be done using solar radiation resulting in an unpredictable variable.
4.2.5
Burner
A burner is required for a charcoal producing process. There are two methods to convert inputs such as wood or sugar cane to charcoal: the direct and indirect method.
The direct method involves igniting the material being converted and sealing the burning material in an oxygen-deprived environment. This allows some of the input to burn up, but produces charcoal from the material remnants. Amy Smith, a former MIT professor who undertook a project to convert sugar cane waste to charcoal 3 , used the direct method
(Figure 4.1a). This method can result in a product with an inconsistent composition (i.e. all of the input material may not be fully converted to charcoal).
The indirect method (Figure 4.1b) “cooks” the input material in an oxygen-deprived environment which is heated. In this method, an exhaust piping system can recycle the noxious gases emitted from the input materials, which are combustible and can be used to provide heat to aid the process. The use of the noxious gases increases the efficiency of the burner and indicates the process is finished when no further noxious gases are emitted from the burner. This creates a more consistent product and is generally more efficient than the direct method.
(a) (b)
Figure 4.1
Methods for Charcoal Creation: the (a) Direct and (b) Indirect Methods.
3 CNN (www.cnn.com)
10

4.3
Power Source
A power source is necessary for this machine in order to operate the different stages of the process. Some of these potential power necessities include compression, transport of materials, drying of product, and other possibilities. To meet the power needs of the machine, four different options are compared.
4.3.1
Internal Combustion Engine
An internal combustion engine is a gas powered option which could prove problematic since Malawi does not have any of its own fossil fuel sources, so petroleum is expensive and not readily available. An internal combustion engine also has many parts increasing the chances of necessary and difficult maintenance, while also increasing the difficulty of the initial assembly. These parts can also be quite expensive which is important to consider because 53% of the population of Malawi lives below the poverty level
4
.
4.3.2
Electricity
Electricity from the local power grid is an option for the design if only focused on urban users; other users would not have access to an electricity source. Problems lie in the reliability of the electricity since many African countries experience rolling blackouts as a method of load shedding on a regular basis.
4.3.3
Renewable Energy
Renewable energies such as solar, wind, and hydro power are alternative power options for this design. These options are environmentally friendly and not wasteful, but also harbor many potential problems. The materials necessary for renewable energy are very costly and not readily available in Malawi. Additionally, the assembly and maintenance tasks for these systems are expensive and complex, requiring significant instruction and down time.
4.3.4
Human Power
Human power is an available energy source which can be harnessed to power multiple components of the fuel conversion process. This option could include hand cranks, bicycles, and levers. By using human powered devices, cost and complexity can both be greatly reduced. Also, jobs can be created with the process. Safety considerations are very important when incorporating human operators in a mechanical process.
4 CIA World Factbook (www.cia.gov)
11

4.4
Transmission
The transmission moves the power generated from the power source to the individual components in order to complete a given task. A number of options that vary in complexity, flexibility, and simplicity were considered in the project design.
4.4.1
Hydraulic
A hydraulic transmission allows for a great deal of flexibility regarding the placement of components relative to the power source. It can also provide mechanical advantage easily through the use of master and slave cylinders. Using hydraulics, power output can be scaled up to do very impressive tasks using a relatively small power source. Hydraulic transmissions add a level of complexity due to the use of a working fluid. There are a number of specific parts needed to maintain proper system operation and pressure. The availability of parts could be an issue as the only cheap and available resource for hydraulic parts would be automotive and construction machinery.
4.4.2
Linkage
Linkages are very simple and easy to construct. It can provide a reliable and effective form of power transmission as well as being made from a variety of available materials.
One major downside to linkages is the difficulty in placing the transmissions relative to the power source and component. Two dimensional linkages are typically the most common and the easiest design and construct. Another downside to linkages it can potentially take a very large or complex linkage to generate a significant mechanical advantage or transmit power in a three dimensional plane. Linkages are a simple and reliable solution for simple operations that can be completed in a two dimensional plane.
4.4.3
Gear and Chain
Gears and chains offer the ability to transmit power easily and efficiently in two or three dimensions. Typically gear and chain parts are easily scavenged from other machines such as bicycles and automobiles. They are a simple solution for mechanical advantage and power transmission between planes. They offer some spatial flexibility without the added complexity of a working fluid. Some issues that may arise with gear and chain transmissions can be mounting and alignment as they will affect the proper operation and reliability of the machine.
12

4.5
Experiment
An experiment to determine the feasibility of converting paper to charcoal was of primary importance. The methods for creating charcoal from wood were tested to verify the feasibility of creating charcoal from paper.
The conducted experiment tested the conversion of paper into charcoal using the direct and the indirect method. Steel cans with tight fitting lids were used as the containers in which the paper was sealed in to create an oxygen-deprived environment. For the direct method, a can was packed with paper which was ignited and sealed within (Figure 4.2a). The intent was for the paper to continue burning and smoldering in the oxygen-deprived environment, converting the paper into charcoal. For the indirect method, a can was packed with paper and sealed. Paper was burned around the can, heating it. This method intends to heat the paper within the can in an oxygen-deprived environment, converting the paper into charcoal.
Based upon the experimental data it was decided that paper conversion to charcoal was not a suitable product. Either method produced an unsatisfactory product. Using the direct method the paper would light and be consumed quickly, but once the can was sealed the flame immediately went out and the paper would not continue to burn or smolder as needed. This produced an unsatisfactory product consisting of mostly paper with burned edges and a small amount of ash from the consumed paper. It was not even possible to create charcoal from the paper using the direct method. Using the indirect method charcoal was successfully from the paper; noxious gases were also produced from this conversion process. Unfortunately the product was extremely light and brittle as well as inconsistent and difficult to light (Figure 4.2b).
The information gathered from this experiment was used in the decision to no longer pursue charcoal as the fuel product.
(a) (b)
Figure 4.2
Experiments of the (a) Direct and (b) Indirect Methods
13

The design variable options were assessed using a decision matrix which prioritizes certain design criteria. The decision matrix then presents weighted numbers for determining the most suitable options for the design. A description of the preliminary design follows (section 5.2).
5.1
Decision Matrices
5.1.1
Process Decisions
The decision matrix for process design variables was completed to determine the best choice for each set of options (Table 5.1). The primary design variables assessed using the matrix were the product, power source, and transmission for the paper to fuel process.
Aspects of the project objectives and design norms were included in the matrix with varying importance based on the variable being evaluated. The weighting is shown as a number between 1 and 5; 5 being of greatest importance and 1 being of least importance.
Cost determination was based not only on an assessment of the cost of materials, but also the profit from fuel product value. For example if the process produced a better fuel product it would offset the increased cost of the equipment. The other categories were scored where benefits have higher ranking.
Design Variables
Weighting
Table 5.1
Decision Matrix for Process Design Variables
Cost Availability
5 4
Maintenance &
Reliability
3
Efficiency Simplicity
3 2
Environmental
Impact
3
Safety Totals
3
Paper Briquettes 4 4 5 3 5 3 4 91
Charcoal Briquettes
Weighting
Human
Internal Combustion 2
Electricity 2
3
4
3
Other Renewable
Weighting
Hydraulic
Linkage
1
4
2
5
4
3
3
3
5
2
3
1
4
3
4
3
4
4
2
4
3
4
4
4
4
5
3
2
3
4
2
2
3
2
3
5
1
5
2
3
2
3
3
2
5
5
2
2
3
3
5
2
2
4
4
3
2
4
67
91
68
78
49
55
87
Gear & Chain 4 4 4 4 4 3 3 91
By completing the process variables decision matrix, the team was able to determine the appropriate process options. These decisions are as follows: The final product will be paper briquettes; human power will be the only power source; and a gear and chain transmission will be used.
14

5.1.2
Component Decisions
The decision matrix for the design components (Table 5.2) follows the same format as the matrix for the process options with varying weights according to the importance of the design consideration. The components discussed in the decision matrix are the shredding, mixing, compressing, and drying components of the device.
Weighting
Table 5.2
Decision Matrix for Component Design Variables
Design Variables Cost Availability
4 5
Maintenance &
Reliability
3
Efficiency Simplicity
3 4
Safety
4
Totals
Food Processor 5 2 2 2 4 4 74
80
82
Lawn Mower Blade
Paper Shredder
Weighting
Paddle/Blade
Drum
Weighting
Screw Drive
4
4
4
5
3
4
3
3
5
3
5
4
4
4
4
5
4
2
5
4
4
3
5
3
2
5
3
4
4
4
5
4
2
4
4
3
4
3
3
3
4
3 84
103
78
Linkage
Hydraulic
Screw Extruder
Weighting
Solar
5
3
3
4
5
4
3
3
4
5
3
4
5
3
5
4
5
5
5
4
3
3
4
3
5
4
3
4
4
5
83
76
88
112
Blower 4 4 3 5 4 3 87
Hot Air Blower 2 3 3 5 3 3 71
Through this analysis it was determined that the preliminary design shall consist of the following components: a paper shredder to increase the surface area of the input material; a solar dryer or combination of solar and blower for removing moisture from the fuel product; a screw extruder for compressing the material into briquettes. The implementation of the process and component design decisions can be found in the preliminary design (section 5.2).
5.1.1
Sensitivity Analysis
Depending on the weightings and scores assigned to the design variables, the design decisions can change drastically. Because of this, it is important to do a sensitivity analysis of the decision matrices and discuss the results.
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For process options, sensitivity analyses were done for each section of the study. Due to the potential higher selling price for charcoal, the matrix value for this option could have been increased. However, it was important to keep in mind the added costs necessary for the burning mechanism required for charcoal production. In this case, the extra component and safety costs outweigh the selling price benefits for this option. When considering the power source options for the process design, consideration must be given to the time needed to run the machine components. Keeping in mind the adage, “Time is money,” time spent with human power can add to the price of this option. However, the next most feasible option is electricity, which is an unpredictable and unreliable energy source in Malawi. Finally, the sensitivity analysis for the power transmission portion of the design indicates that the linkage and gear and chain options are quite close. Although it may be argued that linkages require less difficulty with assembly and maintenance, the flexibility that can be achieved with the application of gears and chains outweighs the simplicity of linkages.
For the design components, sensitivity analyses were done on the shredding and drying components to help determine the strengths and weaknesses of each design. The sensitivity analysis of the shredding component was completed because the paper shredder and mower blades were both considered good choices. The efficiency variable for this component was based on how well the device shreds large amounts of paper.
Since it was determined that the mower blades would require frequent sharpening in order to efficiently shred paper, the paper shredder, already designed to shred the input material, was considered the best choice for the preliminary design. However, if testing proves the mower blade to be an acceptable alternative, this option will still be considered. A sensitivity analysis was also done on the drying component of the design.
Because using the sun requires the least possible complexity and added costs, it is shown as the best possible option. However, since there is a significant rainy season in Malawi a combination of a blower and solar dryer might be the best year-round solution while keeping cost and complexity to a minimum. If the main decision was based on drying speed and reliability alone, forced hot air convection would be the appropriate design choice. However, since making the air hot would require a large energy input, this option does not lie within the design criteria.
5.2
Description of Design
The preliminary design is the combination of the selected input materials, fuel product, process type, necessary components, power source, and transmission (Table 5.3). The preliminary design has proven to be theoretically feasible based on the following: thoughtful analysis of various options (section 4), decision matrices (section 5.1), experimentation, and incorporation of design norms.
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Table 5.3
Design specifications
Design Variables
Input Material
Fuel Product
Process Type
Shredding Component
Design Specifications
Waste paper / Sekera
Fuel briquette
Paper shredder grass shredder

mixer

compressor

dryer
Mixing Component
Compressing Component
Drying Component
Power Source
Transmission
Drum mixer
Screw extruder
Solar heat collector / Blower
Human power
Gear and chain
Waste paper and sekera grass are readily available resources in Malawi, whether focusing in urban or rural areas of the country. These materials will serve as input materials for this fuel conversion process. The process will produce compressed fuel briquettes, made of a mixture of paper, grass, and cassava starch. Larry McAuley, the team contact in Malawi, has indicated a prominent availability of cassava and a cassava starch extraction factory in his area.
The preliminary process includes four components: shredder

mixer

compressor

dryer.
This process could be completed in a continuous or batch process, as well as four individual components or a single multicomponent mechanism. The design will utilize a batch process for simplicity in both operation and design of components. A single multicomponent mechanism would provide transport between each component (Figure 5.1); this eliminates operator energy and time, and the potential for intermediate product loss.
Figure 5.1
Preliminary Process Diagram
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The first component is the input material shredder. The shredder consists of two parallel drums covered in blades, which paper and grass are fed through, resulting in a more homogenous and manageable sized intermediate product. The shredded material will be collected into a hopper, separate from the mixer, so that the shredding and mixing components can be operated independently.
The drum mixer component is the location for the addition of binding agent to the intermediate products. The drum is rotated to ensure a more homogenous mixture, which produces more consistent coverage of the binding agent. This is important because a more consistent intermediate product will place a predictable load on subsequent components. This stage also determines the final consistency of the product; which should burn in a safe and dependable manner.
Mixed intermediate products are deposited into the screw extruder. The extruder consists of an auger within a cylinder where the auger rotates and pushes the mixture down the cylinder, compressing at the extrusion point. The compressed and extruded product can then be cut at regular intervals producing a final briquette.
The final component of the design is the dryer where the damp fuel briquettes are placed to cure.
The preliminary dryer design is a box with metal grating shelves for the briquettes to be placed, and solar heat is trapped in the box. Fans will produce air flow within the box to displace moisture through vents, increasing the drying rate. Dry briquettes are ready to be burned.
All process components are powered by human power which incorporates many design norms: justice, by providing jobs and inexpensive fuel products; stewardship, by reducing cost, utilizing available labor, and use green energy. The human power will be harnessed for the process by bicycles, transmitted using gears and chains.
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Since the context for this project is assembly and implementation in a developing nation, there are two different budgets to take into consideration. The first is the budget for the prototype determined by the Senior Design class. This includes expenses for feasibility testing, materials, research, tools, etc. The Senior Design budget is defined to be an average of $300 per project.
The second budget to consider for this project is the budget for implementation in Malawi. This budget must cover all start up costs involved with the machine and process including construction materials, tools, and labor. The budget for implementation in Malawi is based on the national average salary of about $160 per year while keeping in mind the aid provided by relief missions like CRWRC.
6.1
Senior Design Budget
The Senior Design budget analysis was done according to the initial process and component designs, also including extra materials for testing and possible part failure. The part prices were found by researching used part costs (Table 6.1). The budget analysis was also done on a worstcase basis assuming that some parts will be found in scrap yards for a much lower cost and some others may be donated.
Table 6.1
Preliminary Senior Design Budget
Component Amount
4
Price
Per
$20
Total
Price
$80 Single Speed Bicycle
Consumer Grade Fan Blade
Consumer Grade Paper Shredder
20 in. Lawn Mower Blades
6 in. Auger
6 in. x 4 ft PVC Piping
1 lb. Cassava Starch
2
1
2
1
1
5
$10
$15
$15
$30
$40
$2
$20
$15
$30
$30
$40
10
Various Scrap Metal 1 $0 $0
Preliminary Total $225
The preliminary total of $225.00 lies within the budget allotted to senior design groups. This determines that the testing and initial prototype is economically feasible in this context. Lying within the team’s emphasis on stewardship, however, it is important to keep the project costs to an absolute minimum so that the funds and materials are used in the most efficient way possible.
6.2
Malawian Design Budget
In order for the design to be culturally appropriate, it is immensely important consider the final product costs in the context of Malawi. Through communication with Larry McAuley from
CRWRC, the team was able to determine a rough financial feasibility estimate of the project according to the initial design materials in the context of the financial restrictions in Malawi.
The exact budget, however, is difficult to determine because the final design has not been
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decided on, and the cost of all materials cannot be identified completely. However, since the testing and designing processes will be completed in the U.S. under the Senior Design Budget, only the final design materials and labor costs need to be considered in the Malawian Budget.
Because of the lack of cost data for materials in Malawi, the total project cost as it applies to
Malawi will be analyzed in more detail during the design process. There is also the possibility of finding the materials for no cost in trash piles and through donations from local aid sources, emphasizing the goals of stewardship and caring.
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The Project Proposal Feasibility Study is only the beginning of the design and implementation process. As the year continues, progress must be made to meet the final goals of the Senior
Design project.
7.1
Component Design
Specific components of the machine need to be designed. For example, the human-powered devices need to be studied further so they can be implemented in the safest and most effective way possible. Also, the components need to be designed to withstand repeated use, weather, and potential misuse.
7.2
Communication
As there is hope for this machine and process to be adopted by Larry McAuley and his colleagues at CRWRC, continuous communication must be maintained in order to keep all parties involved updated with changes and progress.
7.3
Prototype Construction
As a final product of the Senior Design project, a working prototype must be built to demonstrate the process of creating fuel briquettes from waste materials. The design process must be iterative and coincide with construction of the prototype. Materials must be gathered from local scrap yards and other sources. This prototype will be displayed at the Senior Design Open House at the end of the Spring semester.
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This project seeks to design a simple low cost process to create fuel from waste material. The fuel making process is low cost and simple to implement with the intent of having wide adoption providing fuel, reducing waste, and creating jobs in developing nations. This design is functional for both waste paper and sekera grass.
The material inputs include waste paper and a grass local to Malawi called sekera grass. The product is a mixed fuel briquette consisting of the two inputs and a starchy cassava binding agent. The power source for the design is human power and incorporates a gear and chain transmission which can be scavenged from bicycles. The current process design calls for a shredder, mixer, extruder, and dryer in series to complete the task. The shredder is a drum type which will slice the inputs. From the shredder the intermediate products are placed in the mixer, this is a rotating drum and adds the binding agent to the intermediate products. The extruder is a screw extruder that will compress and form the briquette shape. From there the shaped briquettes are placed in the dryer which uses solar heat and a blower to dry the final product.
The preliminary project design is feasible for the physical and financial limitations present. The design also takes into account the design considerations and norms laid out. Based upon these findings is feasible to have a process and a mechanism that produces a high quality fuel briquette from waste material that will operate in Malawi.
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