ME 6606 - Project Report

DESIGN OF BINS FOR FOOD WASTE
MANAGEMENT SYSTEM
ME 6606 – COMPUTER AIDED PRODUCT DEVELOPMENT
GREEN BIN RECYCLOMANIA
ARAVIND BASKAR A0136344J
ANIRUDH AGARWAL A0147793N
ELEFTHERIOS CHRISTOS STATHARAS A0135961B
VADRI SIVA SAI A0146540L

ME 6606 Computer Aided Product Development
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TABLE OF CONTENTS
Introduction.......................................................................................................................2
Background ........................................................................................................................................................2
Observations and customer needs.......................................................................................................................3
present technologies.............................................................................................................................................4
Customer needs: .................................................................................................................................................5
concept generation and selection.........................................................................................................................9
External Search Results......................................................................................................................................9
Internal Search Results.....................................................................................................................................10
concept Selection Matrix: .................................................................................................................................12
Design concepts iteration & Final Design........................................................................................................12
detailed design steps..........................................................................................................................................13
Stress analysis...................................................................................................................................................17
Product Specifications.......................................................................................................................................21
Cost Analysis [6-18]
.............................................................................................................................................22
Cost of Material...............................................................................................................................................22
Cost of equipment ............................................................................................................................................23
Pay of employees and rent ................................................................................................................................23
Business model..................................................................................................................................................23
Final model: .....................................................................................................................................................24
Summary: .........................................................................................................................................................25
Financials:........................................................................................................................................................25
Conclusions and recommendations...................................................................................................................26
References.........................................................................................................................................................26

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INTRODUCTION
BACKGROUND
The modern life has high consumption rates which result in a negative impact on the environment. Every year
2.12 billion tons of waste is generated globally. Because of this large amount of waste, countries are trying to find
a convenient and efficient waste management system to reduce the overall impact of waste. In order to achieve
that, the waste management is moving towards processing and recycling wastes. The true aim of every system
that aims to minimize the impact of wastes is to find a way to minimize the waste. In order to reduce the waste
generated a deeper communication and community participation is needed so that the people can understand
the economic and environmental impact their waste have.
It’s crucial in order to have a functional waste management system, to cover all the dimensions. The most
important dimension is of that of the political and administrative, since this will oversee and control all the
minimization, recycling and disposal processes.
According to the United Nations, one third of the food waste produced for human consumption every year gets
lots or wasted. This amounts to US$ 680 billion in industrialized countries and US$ 310 billion in developing
countries. Every year, consumer’s in rich countries waste 222 million tons of food, which is almost as the entire net
food production of sub-Saharan Africa (230million tons).
More specifically, Singapore aims to be “zero waste” country. Working towards this goal, Singapore has integrated
a lot of mechanisms to improve waste recycling and disposal. Pulau Semakau is an island located to the south of
mainland Singapore, and there is the only remaining landfill of Singapore on the eastern side of the island. It
covers of a total area of 3.5 km2
and has a capacity of 63million m3
. In August 2011 it was estimated that this
landfill which began operation in 1999 will last until 2045. In order for that deadline to be extended the
Singaporean government has implemented various ways of minimizing and recycling the waste.
Figure 1. Pulau Semakau
Working towards that goal in 2014 it generated 7.5 million tons of waste and managed to recycle 4.5 million
tons. From these numbers close to 800,000 tons of waste were food and of those only 100,000 tons were managed
to be recycled. This study aims to develop and incrementally integrated system for food waste management. The
system aims to be integrated in households, HDB complexes and hawker centers in steps with increasing degrees
of change. The resulting system hopes to increase the amount of food waste recycled and inform the public
about waste management.

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OBSERVATIONS AND CUSTOMER NEEDS
The bins that are currently being used are not used very efficiently. The trash is not separated and thus making
recycling, difficult if not impossible. Also the trash care loosely packed together which leads to bins being full
fast and lots of waste being around the bins. This leads to an increasing time for waste collection and a potential
public health risk
.
Figure 2. Singaporean food waste statistics
Graph 1 shows data collected from the “ZerowasteSG” website, which shows the low amount of food waste
recycled and the potential for further enchantment. In order to achieve that, the public should first be informed
and educated about the environmental and economic impact their waste have and then a system should be
designed in order the food waste to be efficiently and conveniently recycled.
Figure 3. Inefficient food waste management system
Types of waste classification in Singapore[1]
:
% Composition of Waste Generated: The top 5 waste types make up 75% of the total waste generated in
Singapore, which are either disposed of at the waste-to-energy plants and landfill, or recycled locally and exported:
Ferrous Metal (19%) Construction Debris (17%) Paper/Cardboard (16%) Plastics (12%) Food Waste (10%)
% Composition of Waste Disposed: The top 3 waste types make up 68% of the total waste disposed in Singapore:
Plastics (26%) Food Waste (23%) Paper/Cardboard (19%)

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% Composition of Waste Recycled: The top 3 waste types make up 74% of the total waste recycled in Singapore:
Ferrous Metal (31%) Construction Debris (28%) Paper/Cardboard (14%)
PRESENT TECHNOLOGIES
In order to find a way to implement the “Reduce – Reuse – Recycle” concept we considered three different
concepts that we could potentially use.
1) Efficient Packaging mechanisms
Today, there is no efficient mechanism to collect the waste and package it in order to further process them. The
wastes are disposed in bins without any form of strategy and then the trash is being collected in order to be
transported into landfills. The team would aim to come up with a concept for a more efficient packaging of the
waste in order for the collection to be easier and less frequent.
2) Incineration
Incineration is a way to combust organic substances contained in waste materials. This combustion will create
ash, flue gas and heat which can be used to generate electric power. The team could design an easy process for
each household to use its wastes in order to generate power.
3) Composting – Anaerobic Digestion
The third way is to focus on organic waste and develop a bin and a process in order to make composting easier
for the user. This process will help increase the recycling rate of food, while at the same time provide natural
and organic fertilizer in order to grow more natural crops. Another way to use organic waste is anaerobic
digestion which in the process of breaking down the organic matter to produce fertilizer, also produces natural
gas which can be used to produce electricity. The team would be able to come up with a bin to facilitate the
composting process for the users and also, design a way anaerobic digestion can be used to benefit the society.
For this project we focused our study in organic wastes so and the final concept was a combination of concept 1
and 3. Incineration was immediately disqualified because of its byproducts is causing an environmental impact.
The idea for the use of biogas for anaerobic digestion was also ruled out after taking into consideration an expert
in waste management who suggested that the installation of biogas plant in populated areas would not be feasible.
So the aims of this project is to design a system that will involve the optimization of a bin and the processing of
waste and the setting up a location that the users can deposit food wastes.
 The system aims to use full capacity of the bin in order to store organic waste.
 The system aims to process waste in order to have large surface area
 The system aims be help people recycle their food waste conveniently
 The system aims promote environmental awareness

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CUSTOMER NEEDS:
Based on the teams’ understandings of the general problem, the team designed a survey so that they could learn
from the customers what is it that makes them not recycle their food waste and what is important for their bin
to have.
Demographic
The survey was conducted using googles integrated survey system and overall of 75 people out of whom 33 were
female and 42 were males. The people were chosen to live in different housings like HDB (28%) Condominiums
(29.3%) landed houses (22.7%) and dormitories/ hostels (20%). The professions of the customer’s varied from
student’s to engineers, researchers and IT consultants and their age group ranged from 21 to 55 years old.
Questions about current waste disposal and composting
The first set of questions was designed to understand the current practice of waste disposal. A remarkable 80%
answered that they throw away their food waste together with all the other waste in their home. While most of
the people (84%) have heard of composting, they didn’t know that 80% of the food wastes end up in landfills.
Figure 4. Customer Survey
Next, we found out that most of the customers have not tried composting for various reasons. Most common
reason for the people not trying composting is that they lack knowledge in doing (24%) it and that they don’t
have space in their homes (17.3). Surprisingly the fear of smell wasn’t very prominent within the sample with
only 10.7% answering that they are afraid that it will smell and attract insects. For people that have tried
composting in their homes, when asked what was the main problem they encountered was that it resulted in a
bad smell (16%) and that they couldn’t find a suitable bin (13.3%). Interesting enough is the fact that some of
the respondents indicated that Singapore doesn’t have a proper general strategy in order to take care of their
food waste. Overall despite the difficulties that composting has people seemed really interested in trying
composting in their own homes (72%).

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Our next set of questions was aimed to understand the features that the current bins have. The majority of the people
used bins with cover either plastic (42.7%) or metal (5.3%). As to the main problems these bins have is a mix of
liquid and content spillage during to overflowing. Additionally, when the customers were asked what is the most
important feature they want their bin to have they replied that, hands free use (41.3%) was very important while,
high capacity (24%) and affordable price (20%) also ranked pretty high.

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Lastly, in the question “If there was community wide composting project for food waste, where food waste would
be collected from each household, would you want to participate?”, 86.7% of the participants responded that
they would be interested and all of them would be willing to separate their food waste from their normal waste
in order to participate to the community wide composting project.

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CONCEPT GENERATION AND SELECTION
During this stage, the team brainstormed ideas in order to see how we can address the problems that were
identified during the customer survey. At first an external search was carried in order to see what products are
available in the market that might be able to help us in the solution of some of the problems. Next the team did
an internal search by brainstorming ideas and trying to give solutions to the problems like:
• How can be the waste stored without any inconvenience?
• How can the process of composting be easier?
• How can the involvement of the people be minimized?
In the next section the results of the external and internal search are presented and later the concept selection
matrix is presented.
EXTERNAL SEARCH RESULTS
1. In-house bio gas plant [2]
:
The concept of producing biogas in everyone’s home is something that the company “Home Biogas” has tackled
by their product. The product aims to recycle organic waste at the source, generating Biogas in the eco-friendliest
and effective way. The product can be installed in the backyard of people’s homes and the customer can add
food and animal waste continuously in the bin. The price of such a bio gas plant is 1500 USD and can digest 6
liters of food per day.
Pros: Biogas Production using a continuous process
Cons: Very large, very expensive, and user involvement is large
Figure 8. In-house Biogas Plant
2. In-house composting bin [3]
:
This product aims to make the composting process less complex by integrating a three bin vertical system. The
bin gets aerated naturally and material can be continuously inserted from the top, and the compost can be
removed from the bottom when needed. The bin aims to be more productive from traditional do-it-yourself
bins using this 3 step process and by having a capacity of 466l. The cost of the bin is 200USD.
Pros: Composting using a continuous process
Cons: Very large, expensive, and user involvement is large

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Figure 9. In-house Composting Bin
3. Totem 60 Waste Separation & Recycling Unit[4]
This bin is an all in one bin with different compartments in order to combine different kinds of waste. It features
a food caddy for all the food waste, a general waste compartment and a multi-purpose drawer so the user can
choose what to recycle. The price of the bin is 250 USD
Figure 8. Retail Product
INTERNAL SEARCH RESULTS
For the internal search results we considered two problems that needed to be addressed. The first problem was
to choose how the storage would be stored. The second problem was to see how the waste could be processed in
order to have a large surface area.
1. Storage options:
a) The first option considered is a sliding metal box that could store organic waste and could also be sealed in
order to avoid smell, leakage and content spillage. The box should be made of a metal in order for it to be
recyclable and to be sturdy. Because of its properties the box is going to be reusable and could be beneficial
to any modular design. Also an option like this is going to be relatively cheap since it’s a simple design, and
reusable.
Pros: Sturdy, Reusable, Good for modular design, cost
Cons: Bulky, inflexible.

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b) The second choice for storing the waste is a biodegradable bag. Changing the bags that lots of the customers
use from plastic into a biodegradable material, can prove very convenient since the users are already using a
similar product. The bags would be disposable and could be directly used for composting.
Pros: Small, Convenient, Disposable
Cons: needs to be designed.
Figure 9. Storage Options
2. Processing options:
a) Vertical Mincer: For the processing of the waste two options were considered. First a vertical mincer that
would receive waste from the top and then the passing the waste trough the mincer would result in food
waste in a much smaller size. The rotation of the mincer would be from the top using a handle.
Pros: Small, easy collection
Cons: Not ergonomic rotation
b) Horizontal Mincer: The second choice for processing the food waste is a vertical mincer. This mincer would
receive the waste from a funnel at the side of it and then as in the case of the vertical mincer, the waste
would go through the mincer and would result in food waste in a smaller size. The horizontal axis of rotation
is more ergonomic but the resulting product would be large overall.
Pros: Ergonomic processing
Cons: Large, a flexible collector can’t be attached to it.
Figure 10. Processing Options
VERTICAL HORIZONTAL

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CONCEPT SELECTION MATRIX:
The selection matrix was constructed using: space, cost, ease of use and recyclability as parameters. The products
that were benchmarked were the three concepts that were found during the external search, plus three concepts
that were born by combining storage and processing options that were found during the internal search.
By looking at the selection matrix, we saw that that the concepts of using a horizontal mincer with a box and a
vertical mincer with a bag were scoring higher than any other concepts. So our process for designing the product
began having these results in mind.
DESIGN CONCEPTS ITERATION & FINAL DESIGN
Design-1
Figure 11. CAD Model of Design - 1

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Design-2
Figure 12. CAD Model of Design - 2
We have considered two designs initially. Among the two designs design-2 is selected for simulations because of
its flexibility and usage of lesser design components and the steps have been detailed.
DETAILED DESIGN STEPS
Setting Dimensions
Iteration 1: Conceptualization
The first design was made to demonstrate a simple crushing mechanism that can be used for our purposes.
Initially it was just made considering the diameter of rotation to be ergonomic for use by people. Thus the
approximate length from palm to elbow of the team members was used to get the initial diameter. With that the
following design was produced:
Figure 13. Design Conceptualization in CAD

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The initial design did not consider joining, assembly or manufacturability either. The top mover made of hard
wood had spokes inbuilt in it and the screw flange was attached to the spokes without regard to physical
constraints and assembly. Figure 14 shows the mechanism showing how the screw was mounted.
Figure 14. Mechanism Conceptualization
This design did not consider the weight of components. The screw was initially designed for crushing and not
shredding and thus had very thick blades (2cm) as shown:
Figure 15. Initial Design of Screw
The screw was initially thought to be made of SS to be food grade. The screw alone had a volume of 9334.45 cc
which gives it a weight of about 75 kg!
Iteration 2: Functional Design
Due to the impracticality of the previous design, there was severe redesign required to make the design more
functional. Thus dimensioning was done starting from the volume of waste per week that had to be contained.
As calculated before, about 9kg of waste is produced in a week. Thus the volume required should be enough to
be able to accommodate roughly 9kg of water as the density of water is slightly less than most foods. Thus net
volume needed = 9L. The shape of the bag was to be roughly cylindrical to be most space efficient while
maintaining axial symmetry. Symmetry is needed since the opening between the screw and the holder from
which the food comes is also axially symmetric. The height is taken roughly equal to the diameter for ease of
handling and ease of calculation.

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Figure 16. Design of bag for Collecting wastes
To get a volume of 10L, where H = 2R we have:
9000 = 2𝜋𝜋𝑅𝑅3
→ 𝑅𝑅 = 11.27𝑐𝑐𝑐𝑐
Also it is noted that the lower diameter of the bag should be less than the top diameter so that it easily fits in a
regular cylindrical wire bin as shown in figure 1. Take a top diameter of 12cm (R) and a bottom diameter of
10cm (r) and a length of 24cm (H). The volume of the resulting frustum is given by:
𝑉𝑉 =
1
3
𝜋𝜋 ∗ �
𝐻𝐻
𝑅𝑅 − 𝑟𝑟
� ∗ (𝑅𝑅3
− 𝑟𝑟3) = 9148.32 𝑐𝑐𝑐𝑐 > 9𝐿𝐿
To avoid sharp corners in a fabric bag, a fillet of 3cm is also given at the end which further reduces the final
capacity.
Figure 17. Design of Holder Block
Based on the 12cm top radius, giving extra room for the food to fall beyond the boundary of the holder block,
the inner diameter of the holder block is chosen to be 20cm. To save volume it is made of 1cm thick material
with screw holes to attach to the frame. In order to give a clearance of 5mm for the food to escape so that the
final particles are in the size range of millimeters to centimeters, the maximum diameter of the screw is given at
19cm. The screw is given 4cm long blades at the lower end. So at the base of the blade diameter is 11cm.
Figure 18. Design of Screw & Shaft

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In order to reduce overall screw volume, the screw is hollowed out, giving a wall of 5mm, thus the inner diameter
of 10cm. A wooden shaft goes through the screw which is fastened to it using 6 screws as shown. The 4 screw
holes on the top of the wood block are to attach to the top mover, while the 4 holes at the bottom are to attach
to the bearing at the base of the holder block. The wooden frame was first designed to have handles so it I easy
to pick up. It had all the holes to screw all metal and wood parts together to assemble the bin. The full bin
initially looked as follows:
Figure 19. Assembly View
Figure 7 shows how every component has holes for screws to hold various parts in place together. For
connections to the frame, M10 screws are used in the holder block. For connection of wood parts to each other
and to circular portions, M6 screws are used. The wood used is 1cm thick and M6 holes are made along the
thickness so that screws can be attach to connect to wooden portions.
Iteration 3: Aesthetic Design
The previous design looked like a UFO and people are not expected to lift a 20kg bin very often. Moreover, they
want the hideous mechanism and parts to be hidden to give a standard box shape. Thus the final design was
born as shown below:
Figure 20. Final CAD Model

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STRESS ANALYSIS
The hardest material in food waste is usually bone. We made the design based on the ability of it to be able to
crush bone.
Material Young’s Modulus, E (GPa)
Collagen (dry) 6
Bone mineral (Hydroxyapatite) 80
Cortical bone, longitudinal 11-21
Cortical bone, transverse 5-13
Longitudinal direction Transverse direction
Tensile strength (MPa) 60-70 ~50
Compressive strength (MPa) 70-280 ~50
Typical stress-strain curves for compact bone, tested in tension or compression in the wet condition, are
approximately a straight line. Bone generally has a maximum total elongation of only 0.5 - 3%, and therefore is
classified as a brittle rather than a ductile solid. So bending force on blade F= transverse compressive strength of
bone*area of contact. Area of contact = thickness of blade*width gained from transverse compression of bone.
Thickness of blade t= 3cm-1cm of fillet = 20mm. Let width gain be “w” which depends on the change in radius
or directly on area strain as shown.
Area Strain 𝛾𝛾𝑎𝑎 =
2∆𝑟𝑟
𝑟𝑟
;
∆𝑟𝑟
𝑟𝑟
= 1 − cos(𝜃𝜃) = 2 ∗ sin2
�
𝜃𝜃
2
� ; 𝑤𝑤 = 2𝑟𝑟 ∗ sin(𝜃𝜃) = 4𝑟𝑟 ∗ sin �
𝜃𝜃
2
� cos �
𝜃𝜃
2
� ; 𝑤𝑤 ≈
2𝑟𝑟 ∗ �2 ∗
∆𝑟𝑟
𝑟𝑟
= 2𝑟𝑟�𝛾𝛾𝑎𝑎. Stress = area strain*elastic modulus ⇒ 𝜎𝜎 = 𝛾𝛾𝑎𝑎 ∗ 𝐸𝐸 and this stress should be equal to the
compressive strength, for failure = 50 MPa, ⇒ 𝛾𝛾𝑎𝑎 =
𝜎𝜎𝑐𝑐
𝐸𝐸
=
50
80
∗ 10−3
= 0.000625. The radius of a bone would
be half of the clearance available. Initially the clearance given was = 1.5cm/2 ⇒ r = 7.5mm. Thus w=0.375m.
Hence the transverse force 𝐹𝐹 = 𝜎𝜎𝑐𝑐 ∗ 𝑤𝑤 ∗ 𝑡𝑡, where t is the thickness at tip. Initially we started with a tip of 2cm
end thickness. This gives F=375N. Later we made the end sharp so as to be able to shred and slice food and also
to reduce contact area and hence friction. A sharp end would prevent the blade getting stuck.
The new design was made much smaller so it is lighter and easier to manage. It also gave less clearance so the
food is shredded to smaller bits for a more efficient division. The new minimum clearance at the end of the
screw was from 20cm inner diameter of the holder block to 19cm max diameter of screw blade. Thus r=2.5mm,
w = 0.125mm. While designing, for ease of manufacturing and making the blade not too slender, a base thickness
of 8mm was used. The tip does not have a defined thickness but through usage and wear and tear we assume
the edge thickness (t) to go up to 1mm. This gives a force F=6.25N. The maximum clearance was at the top
where the diameter was 15cm. This gives clearance of 2.5cm or r=12.5mm, w = 0.0625mm for the same thickness
of 1mm, we get 𝑭𝑭𝑻𝑻 = 𝟑𝟑𝟑𝟑. 𝟐𝟐𝟐𝟐𝟐𝟐 or around 3.2kgf transverse force.
Axial force
To push food, the edge of the blade should be able to crush a bone in the axial direction standing vertically on
the base of the holder block. Compressive strength in the longitudinal direction ~70-280MPa. Take 300MPa.
Length of bone getting embedded in the blade =∆r = 0.004mm. Assuming 10 times of that we have 𝑡𝑡 = 0.04𝑚𝑚𝑚𝑚
of bone embedded in the blade. Thus the force per unit length along the edge of the blade is 𝑓𝑓 = 𝜎𝜎𝑐𝑐 ∗
0.04𝑚𝑚𝑚𝑚 = 12 𝑁𝑁/𝑚𝑚𝑚𝑚. The blade being 4cm long has a base radius of 5.5cm while the edge radius is 9.5cm.

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The change in radius increases force per unit length at the base by the same factor giving 𝑓𝑓𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 = 12 ∗
9.5
5.5
=
20.73 𝑁𝑁/𝑚𝑚𝑚𝑚. Moment per unit length is given by: 𝑀𝑀𝑙𝑙 = 4𝑐𝑐𝑐𝑐 ∗ 𝑓𝑓𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 = 829.1 𝑁𝑁. Bending stress 𝜎𝜎𝑏𝑏 =
𝑀𝑀𝑀𝑀
𝐼𝐼
where M is the moment, y is the distance from the neutral axis and I is the area moment of inertia about the
neutral axis. Taking a cross section of length dl along the blade: 𝑀𝑀 = 𝑀𝑀𝑙𝑙 𝑑𝑑𝑑𝑑 and 𝐼𝐼 =
𝑑𝑑𝑑𝑑∗𝑏𝑏3
12
Here b is the
blade thickness and 𝑦𝑦 =
𝑏𝑏
2
. This gives 𝝈𝝈𝒃𝒃 =
𝟔𝟔𝟔𝟔𝒍𝒍
𝒃𝒃𝟐𝟐 or 𝒃𝒃 = �
𝟔𝟔𝑴𝑴𝒍𝒍
𝝈𝝈𝒃𝒃
----- (eq 1)
Here 𝜎𝜎𝑏𝑏 is the maximum allowable bending stress = tensile yield strength of the material. Taking 𝜎𝜎 = 250𝑀𝑀𝑀𝑀𝑀𝑀
we have 𝑏𝑏 = �
6∗829.1
250
𝑚𝑚𝑚𝑚 = 4.46𝑚𝑚𝑚𝑚. The blades were already designed at 8mm base thickness which gives a
factor of safety of 1.79. For load simulation in solidworks only pressure can be applied.
So the initial edge force of 𝑓𝑓 = 12 𝑁𝑁/𝑚𝑚𝑚𝑚 is converted to an equivalent distributed weight of w.
If the moment per unit length 𝑀𝑀 = 𝑓𝑓 ∗ 𝑙𝑙 where l is the length of the blade = 40mm, then for distributed weight
per unit length – per unit length w, 𝑀𝑀 =
𝑤𝑤𝑙𝑙2
2
.
Thus: 𝑤𝑤 =
2𝑓𝑓𝑓𝑓
𝑙𝑙2 =
2∗12
40
𝑁𝑁 𝑚𝑚𝑚𝑚2⁄ = 0.6𝑀𝑀𝑀𝑀𝑀𝑀 = 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑡𝑡𝑡𝑡 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 The result of the
simulation is as follows:
Figure 21. Analysis of the screw for bending due to axial force on blades
The top is fixed while the lower surface of the entire blade is given uniform pressure of 600 kPa. Note that the
yield strength of Aluminium is 250MPa and the maximum stress experienced is 129.4MPa which is well below
the limit still.
Torque requirement
Assuming that the coefficient of friction is maximum is 1. Then the bending load on the blade edge will be equal
to the tangential force on the same edge.

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This gives a tangential force of 12N/mm, applied for the corresponding width 𝑤𝑤 = 2𝑟𝑟�
2∆𝑟𝑟
𝑟𝑟
= 25�
0.08
12.5
= 2𝑚𝑚𝑚𝑚
where ∆𝑟𝑟 = 0.04𝑚𝑚𝑚𝑚 𝑎𝑎𝑎𝑎𝑎𝑎 𝑟𝑟 = 12.5𝑚𝑚𝑚𝑚
This gives a tangential force of 𝐹𝐹𝑟𝑟 = 24𝑁𝑁~2.45𝑘𝑘𝑘𝑘𝑘𝑘 applied at 9.5cm radius. This will translate to force at the
top handle of 𝐹𝐹ℎ𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 = 𝐹𝐹𝑟𝑟 ∗
9.5𝑐𝑐𝑐𝑐
11𝑐𝑐𝑐𝑐
as the handle is in a circle of diameter 21cm. This gives 𝐹𝐹ℎ𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎~2.1𝑘𝑘𝑘𝑘𝑘𝑘
An average man can apply 15kgf of pushing/pulling with 1 hand with ease (personal experience).
Taking half of that for our maximum allowable limit, we have a force of 7.5kgf.
This allowable limit is still ~3.4 times the load experienced in normal operation. Thus this design is easy to work
with. This gives a torque requirement of 𝑻𝑻 = 𝑭𝑭𝒓𝒓 ∗ 𝟎𝟎. 𝟎𝟎𝟎𝟎𝟎𝟎 = 𝟐𝟐. 𝟐𝟐𝟐𝟐𝟐𝟐𝟐𝟐 shared by 4 screws at the top at a radius
of 2.75cm. Each screw takes a load of 𝐹𝐹 =
𝑇𝑇
4∗0.0275
= 20.73𝑁𝑁 As calculated before, additional transverse load is
31.25N which can be in any direction. Maximum net force per screw 𝐹𝐹𝑚𝑚𝑚𝑚𝑚𝑚 = 20.73 +
31.25
4
= 28.54𝑁𝑁
For the poorest quality steel, the yield strength ~179MPa. This gives shear strength of 𝜏𝜏 = 89.5𝑀𝑀𝑀𝑀𝑀𝑀. Using this
shear strength limit, we get a cross sectional area required per screw of: 𝐴𝐴 =
𝐹𝐹𝑚𝑚𝑚𝑚𝑚𝑚
𝜏𝜏
𝑚𝑚𝑚𝑚2
⟹ 𝐴𝐴 =
28.54
89.5
=
0.3189𝑚𝑚𝑚𝑚2
or a radius of 𝑟𝑟 = �
𝐴𝐴
𝜋𝜋
= 0.3186 ≈ 0.32𝑚𝑚𝑚𝑚.The screws used are M6 (r=3mm) but apparently
much smaller ones would do too. Weight of the entire bin is nearly 20kg (~200N). This is to be held by 8 screws
in the holder block. Cross sectional area required per screw: 𝐴𝐴 =
200𝑁𝑁
8∗179
= 0.14𝑚𝑚𝑚𝑚2
𝑜𝑜𝑜𝑜 𝑟𝑟 =
0.345𝑚𝑚𝑚𝑚. Screws used are M10 (r=5mm). The screw holes are fixed while the rim where the handle connects
to the body, is given a torque of 3 Nm (instead of the needed 2.28 Nm) as shown. The simulation results are
shown in the following figure.
Figure 22. Torque analysis of top mover
Note that the yield strength of Aluminium is 250MPa and the maximum stress experienced is 1.36MPa which
is well below the limit even with a torque of 3Nm instead of the required 2.28 Nm being applied.
Spokes design
The entire weight of the bin is also required to be supported by the 3 spokes that hold the screw in the top
mover and the holder block. Each spoke thus carries about 66.7N force which is at 10cm from the base of the
spoke. This creates a bending moment of 𝑀𝑀 = 66.7N ∗ 0.1m = 6.7Nm

Page 20 of 26
The width of each spoke in both the top mover and the holder block are 2cm in width. For a thickness of b we
have an area moment of inertia of 𝐼𝐼 =
0.02𝑏𝑏3
12
and 𝑦𝑦 =
𝑏𝑏
2
for rectangular cross section.
The bending stress at the base of each spoke is given by 𝜎𝜎 =
3𝑀𝑀
0.01𝑏𝑏2 = 𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠ℎ 𝑜𝑜𝑜𝑜 𝐴𝐴𝐴𝐴
Thus 𝑏𝑏𝑚𝑚𝑚𝑚 𝑚𝑚 = �300∗
20
3
250
= 2.83𝑚𝑚𝑚𝑚 The thickness chosen was 1cm for ease of design.
For easy flow of food over the surface it has been rounded using a fillet of 1cm radius. This reduces the cross
section to a semi-circle for the spoke length but increases the cross section at the base even more to 2cm thickness
and ~4cm width. This is definitely safe enough for the load.
Note that the entire weight of the bin coming on the spokes is a worst case scenario when it gets stuck.
The analysis for the spokes done in SolidworksTM
for the holder block and the top mover as shown. The bottom
rim of the top mover is fixed as it will be supported by the bearing while a 20kg force is applied to the surface
where the wooden shaft is connected as shown.
Figure 23. 20 kg axial load stress analysis of top mover
For the screw holder, the side screw holes are made fixed (as they connect to the wood frame) while a 20kg force
is applied to the surface where the wooden shaft rests as shown.
Figure 24. Axial load stress analysis of holder block
Note that the yield strength of Aluminium is 250MPa and the maximum von Mises stress experienced is 10.05
MPa in the top mover and 7.91 MPa in the holder bock which are both well below the limit even with a load of
20 kg which is slightly above the entire weight of the bin (17.42 kgs. In this light, the ability of the wood to be
able to hold the weight of the entire bin was also tested by simple gravity analysis. The entire weight of the bin

Page 21 of 26
is (17.42 kgs). The holes for the screws connecting the holder block and the wood are constrained together while
the weight of the bin is supported by the wood as shown:
Figure 25. Axial load stress analysis of holder block
The tensile strength of wood is given as: 57MPa which shows that this design is safe.
PRODUCT SPECIFICATIONS
After the above analysis, the final specifications of the product are described are as follows:
Capacity: 9L
Dimensions: 30L * 30W * 75H
Materials: Aluminium, Wood

Page 22 of 26
COST ANALYSIS [6-18]
This cost analysis is done to incorporate the cost of manufacturing in the cost of the bin. This includes the
following costs:
1. Material used in all parts
2. Equipment for manufacturing
3. Energy/power usage
4. Salary of employee personnel
COST OF MATERIAL
Cost of screws and fasteners: ~ 1 cent/piece 30 needed per bin: 0.3$/bin. Note patterns are assumed to last 100
parts but actual life is going to be much more. Total cost =35.75$ To get the cost right, find aluminum
<=3.11$/kg.
Sand needed for casting = 6000cc.
Cost = 1.3 $/kg Where density = 1.6g/cc
So 8kg/bin, which will last for 100 bins = 0.125$/bin.
Part Name Volume (cc) Material Weight(kg) Cost/kg Cost
Mincer screw 450
Aluminium
1.26 2.1 2.646
Bearing top 140 0.392 2.1 0.8232
Bearing
bottom
26 0.0728 2.1 0.15288
Holder block 2450 6.86 2.1 14.406
Top mover 960 2.688 2.1 5.6448
Wood block 1640
Wood
1.312 0.0013 2.132
Wood frame 8000 6.4 0.0013 10.4
Lubricant 70 Grease/oil 0.07 0.03 0.0021
All wood
patterns
4026 wood 3.2208 0.0012 0.04831
Area of mesh
(cm^2)
cost/m^2
Wire mesh bin 3000 4.2 1.26
Total cost 37.5153

Page 23 of 26
COST OF EQUIPMENT
Machines needed:
1. Lathes:
a. Wood: for making wood block cost 800USD = 1086 SGD
b. Metal: for finishing of metal parts and some hole drilling 1000USD = 1358SGD
2. Furnace: to melt castings: 50kg capacity 1000USD=1358SGD
3. Table top drill: to make screw holes cost 1358 SGD (1000USD)
4. Welding machine: cost=75USD=102SGD
Total cost of these machines is thus: 1086+1358+1358+1358+102=4302$. If each lasts for the first 500 bins
ordered/made, we have cost of 4302/500=8.6$/bin. Total cost = 35.75+0.13+8.6=44.5$
PAY OF EMPLOYEES AND RENT
Taking a salary of 10$/hour and 5 bins made/hour by 1 person we have a cost of 2$/bin of manpower cost.
Since bins are not produced all the time, a place to manufacture can be rented temporarily. Assuming that 2
people can work together by sharing various machines we have 10 bins/hour. For the first 500 bins we need
500/80 days or about a week. Monthly rent for enough space in SG would be ~ 2000$. So 500 bins need only
500$ worth of rent of a week thus rent = 1$/bin. Cost of power for Melting 50kg of Al (45MJ=12.5units(kW-
hour)) at 0.18$/kwhr = 2.25$. Adding additional cost for operation of other machines ~2.5$. Cost of power
per bin=2.5/4 = 0.63$. This gives a total cost inclusive of everything = 47.13$. Taking the price to be 50$ for
simplicity and to accommodate for costs we may not have considered.
BUSINESS MODEL
Assumptions:
1. Bin selling price 100$.
2. SP of fertilizer = 0.25$ per kg waste (0.5kg/kg waste and 0.5$/kg)
3. We give 10% of total revenue from fertilizer to the following things:
10% is 0.025$/kg. Of that, we give benefits to customer 20% discount on buying fertilizer =
0.25*0.1*0.2=0.005 (If 10% of total is bought by customers). Remaining 0.02$/kg goes half to R&D and
half to sales and marketing. So 10% revenue from fertilizer goes to 2% customer benefits, 4% R&D 4%
sales and marketing
4. Bags cost 2$/kg. 1kg=50 bags so 0.04$/bag [5]
5. Pressure washing cost 1$/feet sq and total surface area of screw and block to be cleaned ~3k cm^2 so it is
0.05 US$/assembly ~0.1$/assembly
6. Cost of transportation and truck rent 1.8$/km 20km a trip=36$/trip
7. 4.5 change of bags in a month. Initially, 4.5 trips/ month since collection is direct
8. Each trip worker paid 10$/hr for 20 bags=0.5$/bag
9. 1 team of 2 sells bin to 20 households/month. We push harder in later stages to make it more for some
months increasing 10 households/ month so it is 3-5 households extra per team.
10. Stage 2: Based on capacity of holding 0.5 month of waste of 1 complex (400 households) = 400*20=8 tons.
This gives volume~16m3
which gives cost of ~300$ we add 200$ cost for a place for placing bags for
collection.

Page 24 of 26
11. Once we have stage 2 collectors, we use 2 trips/month.
12. Based on truck capacity: ~14.5tons [6]
40kg waste/month/household gives 0.02ton/ half month. So truck can carry 725 households waste in 1
trip. For every 700 more households, we have 1 extra trip. Final rate at 7 years = 14 trips/month.
13. We always try to keep no of stages and bins more than requirement so we have room to spare as all localities
are not in the same hdb complex and bin washing needs extra parts.
14. At the end we cover only 4500 households (~12 HDB complexes). Out of total households (1613700) this
is only 0.28% of the houses. Which is reasonable.
FINAL MODEL:
STAGE 1: Collecting from individual houses
Year 1
Hire a team of 2 which covers 20 households a month.
Order 500 bins and a 200$ lathe for wood working and making holes in wood and cast parts. [5]
Cover 240 households
Year 2
Order 500 more bins totaling 1000
Cover 500 total households
Year 3
Cover 760 total households
By the end of the year purchase 2 stage 2 collectors. These can hold the waste for 800 households. Those
collectors also give space for putting fresh bags for users to take while they dump used bags in the collection
point.
STAGE 2: Collecting from central deposit
Year 4
Hire another team of 2 which covers 20 households a month total 40/month. Total 2 teams.
Cover 50 in last month to give total 1250 houses covered
Order 500 bins totaling 2250 and make
Make 3 new collectors totaling capacity of 2000 households.
Year 5
Hire another team total 3 teams = 60/month. Last 3 month 70/month
Total 2000 houses covered
Make 3 new collectors totaling 3.2k households’ capacity
Year 6
Hire another team total 4 teams = 80/month. Last 4 month 90/month

Page 25 of 26
Make 2 new collectors totaling 4k households’ capacity
Year 7
Hire another team total 5 teams = 100/month for 1st
2 months. Then 130/month 10 months
Order 1500 more bins totaling 5.5k
Make 3 new collectors totaling 5.2k households’ capacity
SUMMARY:
At the end we have:
 4500 households covered
 14 trips a month
 5500 bins
 5200 household worth of collector capacity
FINANCIALS:
year 1 2 3 4 5 6 7
revenue 38040 85230 144310 235250 377660 573060 859050
cost 114866.8 122227.1 143620.7 227171.5 343315.2 467260.2 616450.5
income -76826.8 -36997.1 689.3 8078.5 34344.8 105799.8 242599.5
Investment needed 113823.9 5 yr return 43112.6
6 yr return 148912.4
Year 7 return 391511.9
5 yr cash on cash return 0.378766
Revenue growth rate year 3-6 158.35% 534.52%
58.35% by rev 434.52% by income
Revenue growth rate year 1-6 1.7202514 72%
Revenue growth rate year 3-7 156.20% 433.13%
56.20% by rev 333.13% by income
Revenue growth rate year 1-7 1.6812048 68%

Page 26 of 26
CONCLUSIONS AND RECOMMENDATIONS
 Designed a model to incorporate profitable system for collection, processing and recycling of organic
wastes.
 Optimization of the bin has been done to use lesser material, but with same capacity.
 This project main intention is to increase the awareness about food waste recycling & involvement of
people.
 We were attempted to increase the energy production capacity in a year of up to 10% of total consumption
& reduction of carbon footprint by a significant margin.
REFERENCES
1. ZeroWaste Singapore
2. http://www.homebiogas.com/
3. http://www.earthmaker.co.nz/
4. http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MA6061t6
5. http://www.engineershandbook.com/Tables/steelprop.htm
6. http://www.alibaba.com/product-detail/100-PP-Spun-boned-Breathable-
Anti_60407812153.html?spm=a2700.7724857.29.28.LKxrJH&s=p
7. http://www.answers.com/Q/How_much_can_the_average_American_garbage_truck_hold
8. http://www.ebay.com/sch/Lathes-/57121/i.html
9. http://www.iron-foundry.com/green-sand-iron-casting-cost.html
10. http://www.amazon.com/dp/B0019CGYLM/?tag=woodlatherepo-20
11. http://www.ebay.com/itm/WARNER-SWASEY-TURRET-LATHE-MODEL-M-842-NO-8-
/220517742035?hash=item3357e1b5d3:m:m_vZy-PN91iAwRFyVKY1jKw
12. http://www.indexmundi.com/commodities/?commodity=aluminum&currency=sgd
13. http://www.hearnehardwoods.com/hardwoods/pricelist/pricelist.html
14. http://www.alibaba.com/product-detail/Thermal-conductive-silicone-
grease_1174483835.html?spm=a2700.7724857.29.3.sp9884&s=p
15. http://www.dhgate.com/product/welded-mesh-fence-with-iron-wire-material/372705800.html#se1-2-
1b;price|2195169337
16. http://www.alibaba.com/product-detail/low-price-Induction-Melting-Electric-
Furnace_60330039664.html?spm=a2700.7724857.29.12.CNYH5r&s=p
17. http://www.alibaba.com/product-detail/table-drill-machine-wmd25v-at-
discount_60323913494.html?spm=a2700.7724857.29.87.Vp7cZZ
18. http://www.alibaba.com/product-detail/2015-welding-machine-price-list-
WS_60280239608.html?spm=a2700.7735675.30.67.lpo4dk&s=p
19. http://www.hometowndumpsterrental.com/blog/futuristic-trash-and-recycle-bin-designs
20. http://www.nea.gov.sg/energy-waste/waste-management/waste-statistics-and-overall-recycling
21. http://www.atlas.d-waste.com/
22. http://www.biomaxtech.com/web/index.php
23. http://www.engineeringtoolbox.com/wood-density-d_40.html
24. http://www.indexmundi.com/commodities/?commodity=soft-sawn-wood&currency=sgd
25. http://www.engineeringtoolbox.com/latent-heat-melting-solids-d_96.html

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