Bi0-digester Toilet

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    Biodigester ToiletBrad Ashley

    Farai ChikwatiJithin JohnJosh PetroXan Smith

    Adam SzumlinskiMay 25, 2011

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    Executive Summary

    The poverty-stricken village of Devikulam located in India has many prob-lems that are in severe need of being solved. Pollution-related issues suchas lack of clean water, clean cooking sources and the health risks related toopen defecation are all of major concern to the wellbeing of the village. Ap-propriate housing, local industry and community integration are also areasthat are in need of improvement.

    In order to x the many issues that face the village, the group discusseda number of ideas to solve a range of the problems. Ideas including solarstills, rainwater capture, wind energy, a brick extruder and a way to com-

    press rice hull into building blocks were investigated. The idea that waschosen however was the biodigester. It was decided that the biodigesterhelps relieve the greatest number of problems and would be of most benetto the community. The problems the biodigester helps solve are as follows;

    the disease related dangers associated with open defecation,

    the dangerous use of wood re cooking which is a major cause of healthproblems and even death due to smoke inhalation,

    the biodigester also provides nitrogen rich fertiliser which can be usedto increase the income generated through their agricultural industry.

    Biodigesters use anaerobic digestion to break down biological matter whichin turn produces methane gas that can be used as a clean energy source forcooking and even lighting. Anaerobic digestion also has the added benetthat it helps to destroy pathogens found in human waste far quicker thanthat of leaving it to compost. Within three months of waste being left in ananaerobic state it becomes safe for people to handle without serious healthconcerns, the waste can then be used as fertiliser.

    The basic design of the biodigester consists of two main storage tanks and atoilet slab with a modular toilet design. The tanks are designed to be usedin a cyclical manner, with one tank being used and the other tank being leftundisturbed for a six month period to ensure the waste is safe to handle. Thetanks will be large rectangular structures built mostly underground with aslight lip above ground. The tank cover will be made of heavy duty plasticand held down to keep an airtight seal with the tank.

    The toilet slab is a raised concrete slab that has rectangular insets con-taining pipes which lead down to the storage tanks. The rectangular insetscan have a modular insert placed within it depending on what the pipe lead-ing to the tank is being used for. If the tank is being left undisturbed the

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    inset will have a cover in place, otherwise it will contain either a squat toilet

    or a mixing trough for manure.

    The system is designed to be shared by multiple villagers, in order to re-duce costs and get the maximum efficiency out of the system. As such theimplementation and building processes need to be very specic. Holes areto be dug to the correct size, with the pipes placed in the correct manner.Afterwards the concrete is to be poured into the hole to form the tank. Theplastic sheet is then placed on top of the tank. Afterwards the pipes areconnected to their correct systems and the biodigester is ready to be used.

    As part of the implementation process, it would be ideal to introduce the

    system to the higher caste villagers, so that they do not look down on theidea and in turn encourage the rest of the community to use the system.

    For a system such as the one proposed, the villagers will need training onhow the biodigester works, how to use it and how to maintain the systemcorrectly. They will also need information on the health benets and cleanenergy produced by the biodigesters, training on how to utilise the energyfor their everyday needs.

    In conclusion this design is ideal for the Devikulam community as it elimi-nates several of their problems and replaces it with a renewable, useful and

    clean energy source. The benets outweigh the costs of the project, the gasproduced saves on other cooking fuels and the fertiliser can help improvecrop yields. We have met all of the learning outcomes as outlined by Engi-neers Without Borders. We have demonstrated the application of technicalknowledge by coming up with a difficult design, as well as learnt to integratesustainability and the specic context to the end design. Throughout thedevelopment process we have also been able to develop communication andteamwork skills, by assigning jobs and incorporating multiple ideas into thedesign. Finally, we have learnt to work with the complexities of workingcross-culturally.

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    Team Reection

    Adam

    The most difficult task when faced with a problem as large as the EWBproject which I found, was the initial ideas and designing phase, such as,nding suitable solutions to reach your goal whist considering the cultural,social and real life limitations and aspects of the chosen community.I think that working in a team really helped me and the project progress,as there is a constant stream of information and ideas being put forward byother members of the team that may not have been considered working onones own and the project develops under several diverse ideas and combinedknowledge.If I were able to repeat this project and change how I approached one of the aspects of It I would rst dene the problem I wanted to face and thendene my project around the cultural and social aspects and the availableresources and scope, as we found that it is more difficult to go from an initialidea back to considering the factors and limitations and dening the scope.The most enjoyable and benecial part of the project was to be able toimprove my team organisational skills and being able to improve my com-municational and time managements skills in a comfortable environment.

    Brad

    The largest Obstacle I faced in this challenge was communication with theentire group, which affected how well our report turned out, as demonstratedin the Interim Chapters Report, where much information was overlappedby different members of the group. However, having said this, our projectsimply would not have been possible without the help of each member of thegroup. Each member provided different ideas, backgrounds and knowledgewhich were all vital aspects to the development and growth of our project.If I had the opportunity to re-do this project, I would have organised one ortwo more meetings a week. These meetings would have been much shorterin length and would have only been there to check each members progresson their separate chapters and workload. This would have allowed the groupto not overlap on so much information. The most enjoyable aspect of thechallenge was meeting new people who I would not have met if I did nothave the opportunity to participate in this challenge.

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    Farai

    The greatest challenge I faced working on the project was my lack of back-ground information on the cultural aspects of the community to the extentthat, regardless of what I have learnt, for some part of the challenge, I wasleft making some assumptions based on my past experiences. Working asa team, however, made the challenge more manageable, none of us had tocarry any burden alone. Instead, we researched and shared our ideas, while,carefully considering our social/cultural, economic and environmental con-straints. Given a chance repeat this challenge, I would make sure I gotmy ideas organised in time, giving me enough time to review what I hadwritten. Most of all, I enjoyed working as a team as it helped me see somedifferent ways of approaching problems that I had not considered before, italso helped in keeping me motivated as the challenge grew more and moredifficult.

    Jithin

    This EWB challenge was something like an eye opener to me. Due to thevarious scenarios we faced during the challenge, I was able to discover anddisplay my innate skills and abilities. This challenge exposed me to the realworld problems and also taught me how to tackle them using my skills asan engineer.The largest obstacle which I faced while working on the project was meet-ing the time constraint as well as presenting ideas which were sensible andpassed the quality mark.Working as a team helped me a lot in realising the importance of cama-raderie and teamwork. By working in a team I understood how much wedepend on others for various tasks and how important this co-relationship is.In other words you can only achieve something by sacricing something of yours. Another thing I realised during teamwork is that not a single personis similar to another, everybody thinks and acts differently in almost everyperspective. This difference in thinking helped us a lot in gathering differentideas for our Project making it more distinct and unique in its own way.If we were given a chance to do the project again, I would probably rec-ommend that in the future we are given something which we can sort of understand more in a realistic way rather than working on the basis of as-sumptions. The amount of background knowledge we were able collect islimited because most of us solely relied on online resources and data col-lected by someone else, not a single person involved in doing the project hasa genuine understanding of what the situation at Devikulam is.The most enjoyable part of the challenge was working in teams. This madethe task easier and more manageable. There was not a single point in timewhere I felt really stressed because I always had my teammates to rely on.

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    Josh

    The EWB challenge has been a very enjoyable and interesting experienceoverall. It has been a pleasure to work on this project as part of my Engi-neering degree. Throughout the design process we ran into several obstacles,the most severe of which was the initial complexity of the design. Little rel-evant information was initially available, so we really had to knuckle downwith our research, which ended up with spectacular results. Working as ateam had a positive impact on the project, as jobs were able to be allocatedfreely, and ideas were able to be discussed and considered by the team.The most enjoyable part of the project was making excellent friends with myfellow group members. I am truly glad to have been given the opportunityto work with such amazing people. I also enjoyed being able to apply myknowledge to an actual real life problem. If I were to do this project again, Iwould change absolutely nothing. It has been an enjoyable experience, andI am extremely proud of the design we have come up with.

    Xan

    The largest obstacle faced while working on the challenge was due to thesize of the project. Initially the project seemed to be a simple matter of creating a toilet and a system to capture the gas. However after discov-ering the health aspects involved in the handling of human waste and thecomplexities of biodigester design the project became more difficult thaninitially expected.Working as a team has been a good experience, different people have differ-ent skills and abilities, all of which have added to the project as a whole.If the project was to be done again more initial research would be investedinto uncovering the complexities that would be faced, also more planning andgroup organisation would be done from the very beginning of the project.The most enjoyable part of the project has been working with a good groupof people, designing something interesting, and learning new things.

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    Table of Contents

    Executive Summary ii

    Team Reection iv

    1 Introduction 11.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Problem Denition . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Problem Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4 Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    2 Design Options 42.1 Design Ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

    2.1.1 Rainwater Collector . . . . . . . . . . . . . . . . . . . 42.1.2 Solar Still . . . . . . . . . . . . . . . . . . . . . . . . . 62.1.3 Brick Extruder . . . . . . . . . . . . . . . . . . . . . . 72.1.4 Windmill . . . . . . . . . . . . . . . . . . . . . . . . . 82.1.5 Rice Hull Bricks . . . . . . . . . . . . . . . . . . . . . 102.1.6 Biodigester . . . . . . . . . . . . . . . . . . . . . . . . 11

    2.2 Final Design Decision . . . . . . . . . . . . . . . . . . . . . . 12

    3 Final Design 133.1 Biodigester Summary . . . . . . . . . . . . . . . . . . . . . . 13

    3.2 Biodigester Details . . . . . . . . . . . . . . . . . . . . . . . . 143.2.1 CAD Drawings . . . . . . . . . . . . . . . . . . . . . . 14

    3.3 Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.4 Slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.5 Extraction Pipes . . . . . . . . . . . . . . . . . . . . . . . . . 173.6 Inlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.7 Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    3.7.1 Detailed Description . . . . . . . . . . . . . . . . . . . 213.8 Design Documents . . . . . . . . . . . . . . . . . . . . . . . . 22

    3.8.1 Bill of Materials . . . . . . . . . . . . . . . . . . . . . 223.8.2 Manufacturing Process . . . . . . . . . . . . . . . . . . 233.8.3 Maintenance . . . . . . . . . . . . . . . . . . . . . . . 243.8.4 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

    3.9 Applications of biproducts . . . . . . . . . . . . . . . . . . . . 263.9.1 Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . 263.9.2 Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273.9.3 Cooking Technologies . . . . . . . . . . . . . . . . . . 283.9.4 Lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

    3.10 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . 303.10.1 Materials Available Locally . . . . . . . . . . . . . . . 30

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    3.10.2 Materials to be Imported . . . . . . . . . . . . . . . . 31

    3.10.3 Methods of Manufacture . . . . . . . . . . . . . . . . . 32

    4 Implementation 334.1 Implementation Plan . . . . . . . . . . . . . . . . . . . . . . . 334.2 Construction Process . . . . . . . . . . . . . . . . . . . . . . . 34

    4.2.1 Methods of Installation and Labour Considerations . . 364.3 Education Schemes . . . . . . . . . . . . . . . . . . . . . . . . 37

    4.3.1 How does the Biodigester work? . . . . . . . . . . . . 374.3.2 Sanitation . . . . . . . . . . . . . . . . . . . . . . . . . 394.3.3 Gas Power . . . . . . . . . . . . . . . . . . . . . . . . 404.3.4 Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . 41

    4.4 Safety Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 Evaluation 42

    5.1 Team Evaluation of Biodigester . . . . . . . . . . . . . . . . . 425.2 Feasibility of Biodigester . . . . . . . . . . . . . . . . . . . . . 42

    6 Conclusion 43

    7 Summary 44

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    List of Figures

    2.1 Rainwater Collection . . . . . . . . . . . . . . . . . . . . . . . 52.2 Solar Still . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.3 Brick Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . 73.1 Final Render of Biodigester . . . . . . . . . . . . . . . . . . . 143.2 Biodigester Wireframe . . . . . . . . . . . . . . . . . . . . . . 143.3 Biodigester Tank . . . . . . . . . . . . . . . . . . . . . . . . . 153.4 Toilet Slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.5 Extractor Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . 173.6 Squat Toilet . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.7 Slab cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

    3.8 Biodigester Materials . . . . . . . . . . . . . . . . . . . . . . . 22

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    List of Tables

    1 Population and literacy in India according to the 2001 census* 40

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    1 Introduction

    1.1 Background

    Needs to be changed and cited so as not to be plagiarism but you get the idea

    EWB in partnership with Pitchandikulam forest has chosen the communityof Devikulam in East India to be the topic of the 2011 Engineers WithoutBorders challenge. The aim will be to provide sustainable solutions to theissues faced by the community in a range of areas such as energy, waterand sanitation, housing, industry development, ICT, transport and wastemanagement. EWB and Pitchandikulam forest hopes that the solutionsparticipants come up with could be implemented and be used to improvethe quality of life of the people in Devikulam.Devikulam is one of several villages located in the Nadukuppam Panchayat,which is a small sub-division of the Viluppuram District, in the state of Tamil Nadu. The village is blessed with a beautiful landscape full of tropi-cal plants and wildlife which is seen as one of the communities most valuableassets. Unfortunately the infrastructure in the village is of poor quality andmajority of the people in the area are living below the poverty line.The community is deeply divided between social classes or Castes. Peopleof different castes do not normally associate with each other and there isa mutual acceptance of this fact amongst the villagers. Breaking the so-cial barriers in the community is important for allowing a common sense of purpose to develop, and encourage cooperation amongst the people.

    1.2 Problem Denition

    Needs to be changed and cited so as not to be plagiarism but you get theidea

    All households in Devikulam use rewood and kerosene for cooking; ap-proximately 3L of kerosene is required each month for cooking purposes.Although LPG is preferred for its faster cooking rate, there are only 7 housesthat have LPG as an option.

    Improved cooking technology would also be benecial for the community.Around 70% of Indias population currently cook on bio-mass fuelled stovesthat are inefficient and very dangerous for health. Worldwide, 1.6 millionpeople die every year because of respiratory problems caused by smoke in-halation. The development of a smokeless stove would have many benets asit would reduced indoor air pollution and related health issues. There wouldalso be additional environmental benets in terms of conserving biomass andslowing down deforestation.

    Recently, sanitation tests have been completed on the water supplies from

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    the three main taps. The analysis indicates that the greatest areas of con-

    cern for the water supply are salinity and bacterial contamination. Saltwaterintrusion may increase the salinity of the water, making it unt for drinking.In addition during monsoon periods polluted water from the pond and sur-rounding areas that is contaminated with human or animal waste could owinto the bore and pollute it having signicant implications for human health.

    The provision of appropriate wastewater treatment is extremely importantto sustained environmental and human health. The common practice of open defecation in Devikulam has the potential to transfer pathogens toboth water and food supplies. Several wastewater treatment systems havebeen applied in the surrounding region to varying degrees of success. Dry

    or compost toilets for instance have been commonly implemented and havesignicant benets (not requiring water and allowing for simple and safewaste disposal). They have been introduced in rural villages with varyingrates of success dependant on each villages social dynamic. It is suggestedthat if they are to be implemented, signicant educational support wouldbe required. Other methods that have been practiced include;

    Baffle Reactor and PondSeptic Tank and Drain FieldBiodigesterCompost Toilet with Urine Separation

    Horizontal Flow WetlandAlthough the provision of biomass systems for wastewater treatment hasalso been considered, it is understood that its implementation would re-quire signicant support as the idea of using human waste as a fertiliserclashes with local beliefs and values.

    1.3 Problem Scope

    The problems we have chosen to address include Energy, Sanitation and theuse of human waste as a fertiliser. The Energy relates to the production of biogas for cooking food and the improved health and safety relating to using

    a clean energy source rather than biomass. We will also cover sanitation,by using the toilet system to prevent disease from pathogens and bacteriarelating to human waste. The byproduct of fertiliser from the biodigesterwill be discussed relating to he destruction of pathogens for safe handlingand education to remove the negative views attached to using human wasteon elds.

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    1.4 Criteria

    EWB SPECIFICATIONS. Financial Considerations, Cultural Considera-tion, Available Resources, Technological Considerations.

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    2 Design Options

    2.1 Design Ideas

    2.1.1 Rainwater Collector

    A main idea of our group was to create a Rainwater Collection Facility. Thisfacility was to be used for fresh drinking water, water for cooking and evenas a means to bathe and clean oneself.Upon researching the idea of rainwater as a means of potable water, wefound that the water was not as clean as we predicted. This is not to saythat rainwater is unclean, more that the natural process by which waterfalls as rain lends itself to being contaminated by pollutants in the air and

    possibly surface carried bacteria which may still be carried in the water.This means that the water would require boiling before being safe enoughfor humans to consume and that the Rainwater Collection Facility wouldrequire highly effective ltration for all uses, which adds another labour andcost factor to the project.Another factor to consider was how the Rainwater Collection Facility wouldbe lled. The houses in Devikulam are not designed to accommodate rain-water gutters on the side, and seeing as they are constructed mostly of claybricks, it is not feasible to simply say we will bolt rainwater gutters ontheir houses... Water tanks are generally cylindrical or spherical in designbecause it provides the strongest shape available, as well as the most eco-

    nomical. However a at surface such as that seen on a Solar Still wouldprovide a much larger surface area for collecting water, making it more effi-cient.We decided to discard the Rainwater Collection Facility for the above rea-sons, and because a Solar Still would theoretically provide a much moreeffective means of fresh, drinkable water than the Rainwater Collection de-sign. The Solar Still would not require as effective ltration, as very littleexternal elements will affect the water which in turn lowers the maintenancerequired to wash and clean those lters.

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    Figure 2.1: Rainwater Collection

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    2.1.2 Solar Still

    One of our early design ideas was to construct a solar still water purierso that the town of Devikulam could easily and freely have a means of producing drinkable water.The general functionality of a solar still is to use the suns solar and heatenergy to evaporate a pool of contaminated water, the evaporation processwould leave behind salts, debris and other chemicals, the water that hadevaporated would then collect and condense or a slanted or convex panelabove and collect into a separate trough or container which is drinkable.

    The major draw backs with a solar still is that during optimum weather

    Figure 2.2: Solar Still

    conditions a solar still can produce around 6 litres of clean water per squaremeter of surface area, and that the distilled water doesnt reach boiling pointso micro organisms and bacteria may survive the process and cause a threatto health concerns.To overcome these drawbacks a secondary energy source would be necessary,either an electric or fuel powered heating apparatus added to speed up thedistillation process and also increase the temperature of the impure water.

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    2.1.3 Brick Extruder

    A possible idea for the EWB Challenge was to create a hand cranked brickextruder that had a replaceable die design to enable different shapes to beextruded. These shapes would include semi hollow bricks, roof tiles andpiping.The basis of the design was a feeder for the clay, a screw pump that wouldbe cranked by hand to force the clay out through the interchangeable die.The idea was discarded due to the fact that using local resources ring bricksin a kiln was not feasible due to the lack of a kiln and the energy require-ments of running a kiln if one were to be built.Unred bricks can be eroded and damaged by water unless treated withbitumen emulsion or other water dispersant methods. Semi-red bricks canhelp relieve this problem and can be produced by stacking the bricks andthen ring them with the rice hulls which are a waste product of rice. This islimited to the availability of rice hulls which are seasonal, is energy intensiveand still does not match the quality of fully red bricks.The problem of erosion and damage by water eliminates the possibility of extruding roof tiles and piping which means that the design would simplybe a brick extruder. This makes the design infeasible because it would beeasier to simply make mud bricks using casts as it would be easier to makeand maintain the casts, cost less and use less resources to produce.

    Figure 2.3: Brick Extruder

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    2.1.4 Windmill

    While in the brainstorming stage for the design project, the idea of Energywas discussed at length, in particular the aspect of using Wind Energy asa primary energy source. In theory this would have been a great t for theDevikulam community, as it provided a renewable and clean energy source.When researched however, a few issues aroused in terms of implementingthe system, the most signicant of which was the efficiency and propor-tional size of the system. As wind has very little density and the speed of wind can vary, a large wingspan that covers a large surface area is a must.2.5m-7.6m diameter is recommended for a stand-alone system. As coveredin the equation Power/Swept Area = 0.5 x Air Density x Velocity 3 *, wecan see that the power of the wind is directly proportional to the SweptArea when the function is re-arranged in the form of Power = 0.5 x SweptArea x Air Density x Velocity 3 .Abbas Ghassemi, 2009, Wind Energy Renewable Energy and the Environ-ment, Taylor and Francis Group, pg 35.

    With the current mean wind-speed as provided from the EWB challengewebsite (5.4m/s, with a standard deviation of 1.4m/s), we can get good val-ues of the energy produced. However, not all is as it seems. As with anyother energy conversion system, it is not 100% efficient. The maximum pos-sible efficiency of a wind turbine is 59%, however turbines of this efficiencydo not yet exist. On average, the efficiency of a system is 35%, which isroughly one third of the energy that hits the turbines blades. Another blowto its efficiency is the obvious problem of variable wind speeds, meaning aconstant level of energy generation is not possible.If the wind speeds are variable, an obvious x would be to instead enlargethe swept area to ensure greater energy produced. While this would work,it would seriously impact on the cost of the system and also the systemssize.Another such issue with Wind Turbine efficiency is the need to be main-tained regularly. Constant movement and friction as we all know can causelarge amounts of wear and tear, therefore making maintenance a necessity.

    The issue with this of course, is the lack of skilled labour currently in theDevikulam village, meaning repair and general checkups could be lengthyand expensive.The cost is also a signicant issue. Approximately 80% of the systems life-time cost can be attributed to an installation cost of $3500-$8500AU perkW for a stand-alone, local system. Although with time the benets of therenewability and cleanliness of the energy will outweigh the initial invest-ment, it costs more to get up and running than a Fossil Fuel system. This,coupled with the isolation of the Devikulam community, would make it ahuge monetary investment to begin using Wind power.

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    From the above information, we can see that if Wind Turbines were im-

    plemented correctly it could be a viable and renewable source of energy.However issues such as signicant cost, efficiency, proportional size, andmaintenance make Wind Energy an unsuitable resource for the Devikulamcommunity to use effectively and consistently.

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    2.1.5 Rice Hull Bricks

    1 page by JITHIN

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    2.1.6 Biodigester

    1 page by FARAI

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    2.2 Final Design Decision

    1-2 pages by ADAM on why we chose the Bio Digester

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    3 Final Design

    3.1 Biodigester Summary

    A Biodigester is a closed system in which microorganisms break down wasteproducts to produce biogas and a nutrient-rich fertiliser. The issues thebiodigester will be able to solve are as follows;

    preventing disease caused by human waste,

    preventing health problems caused by using biomass fuels for cooking

    and providing a safe fertiliser from the slurry.

    There are a number of different bidodigester designs already in use, thethree most common being the Chinese dome biodigester, the Indian oatingbiodigester and the salchicha sausage tube biodigester.

    In order to destroy pathogens in human waste it is nescessary to leave itin a state of anaerobic digestion for a period from 60-90 days (2-3 months),aerobic composting requires one to two years to kill off all the pathogens.The team chose not to use the sausage tube biodigester due to the factthat we cant be sure the pathogens in the input feed will not spread con-taminates through the slurry to the output feed making it an unsafe choice

    of biodigester for human waste even if we were able to make a tube longenough to have a waste pass through time from end to end of three months.In order to prevent contamination and provide time for the pathogens tobe destroyed but still allow use of the toilet facilities the team decided ona two tank solution. One tank is to be connected to a toilet and used forgas production while the other tank is left for at least 3 months to destroyall pathogens before emptying the tank and using the waste as a fertiliser.The emptied tank would then be used to take waste and produce gas whilethe full tank is left for a minimum three month period before emptying forfertiliser.The size of the tanks is designed to hold 6 months of waste from 15 peo-

    ple and one animal, however larger tanks could be made or they could becleared out up to four times per year so long the tanks are left to sit forthree months before emptying.The lids of the tanks will be made out of heavy duty polyethylene sheetingwhich is cheaper and easier to make and install than a xed concrete domeor oating cover. A hole will be located on the centre of the sheeting sheet-ing which will be attached to piping allowing bags to be lled with gas.The actual toilet section will be a raised slab with a modular toilet/trough/coverthat can be placed into the slab depending on which tank is being used andthe purpose of use at the time. It will be a simple drop design with a venting

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    pipe to help reduce any smells produced.

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    3.2 Biodigester Details

    3.2.1 CAD Drawings

    Figure 3.1: Final Render of Biodigester

    Figure 3.2: Biodigester Wireframe

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    3.3 Tanks

    Figure 3.3: Biodigester Tank

    The tank will be made of concrete, the size will depend on the numberof users and how many times they intend to empty out the fertiliser eachyear. The tank in the above picture and the illustrations on the previouspage depicts a tank for 15 people plus an animal to be emptied twice eachyear.The tank will be lled via a pipe leading to a hole near the bottom of thetank which will be created during construction by sealing a piece of PVCpiping into the concrete.The tank will be covered with heavy duty plastic sheeting to trap in thegasses and prevent oxygen from entering the system.

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    3.5 Extraction Pipes

    PVC pipes coming out from behind the slab as shown in the complete con-struction illustrations are connected under the slab to the pipes going downto the biodigester tanks. They will act as air extractors using convection tosuck air from inside the toilet facilities through the pipe and release themwell above head height. The top of the pipes should be covered in y meshto prevent ies attracted by the smell from entering the pipe.

    Figure 3.5: Extractor Pipe

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    3.6 Inlets

    Inlet animal waste and vegetable matter - yet to design.

    Inlet human waste (squat toilet)The toilet design will be a simple squat toilet made of stainless steel, ce-

    Figure 3.6: Squat Toilet

    ramic or possibly cast into a concrete block.Inlet cover during disuse - doneThe cover will be made of concrete and placed over the hole leading to the

    Figure 3.7: Slab cover

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    storage tank while pathogens are being destroyed. The slab allows more

    space within the toilet facilities to be utilised and prevents people from be-ing injured by a hole in the ground. It also acts as a lid to prevent smellsfrom escaping the anaerobic tank.

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    3.7 Gas

    Gas ConnectorsConnector on tanks plastic sheet covering - the gas connector will be made of plastic with large rubber washers and additional plastic washers for stabilitysandwiched between two plastic nuts. This will allow an airtight seal withthe plastic and will not corrode when in contact with the gasses producedin the biodigester. NB need to go to bunnings to get an idea of commonlyavailable PVC tube, thread types etc. so I can gure out how to design theCAD model for this.Shut off tap Once again, investigate what is commonly available, needs tobe gas tight and preferably not made of metal.Gas Flame TrapAfter the plastic sheeting connector and a shut off tap a ame trap shouldbe put inline with the system for safety purposes. A simple ame trapconsisting of a container lled with steel wool will double as a ame trapand gas scrubber.Gas StorageThe gas will continue along piping to large plastic bags which will be lledand used for cooking.

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    3.7.1 Detailed Description

    Detailed Description of the design XAN

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    3.8 Design Documents

    3.8.1 Bill of Materials

    The materials required to construct our bio digester are; cement, pvc tubing,and a suitable airtight plastic to hold and store gasses.

    Figure 3.8: Biodigester Materials

    the tanks will be 210x210 cm base and 230 cm high and 10 cm thick.The average price of cement in India is around 200 rupees for a 50kg bag androughly 30 bags create 1 meter cubed of concrete, the tanks will be 210x210cm base and 230 cm high and 10 cm thick giving 2,373,000cm3 of cementneeded per tank which is 2.373 cubic meters of cement per tank but the ce-ment can be mixed with sand a gravel to create concrete the standard mixis for each part cement add 2 parts sand and 3 parts gravel so only 1/5th of the total volume is needed to be cement for both tanks 4.75 meters cubed is

    needed which is roughly 120/5 bags which is 24 plus an extra 6 for spare andalso to build the toilet slab, 30 bags at 200 rupees is a 6000 rupee cost whichis just under $130 AU per system. The PVC piping is needed for the inlettubes and also to transport the gas from the digester to either households orextra storage, for the plastic coating over the tanks any strong yet exibleplastic will do, these plastics and PVC pipes should be easily available, thenet price for an entire unit should not exceed $170-$200 AU, admittedlythis is a large cost but the system will provide a constant source of cleanenergy for cooking and also fertilizer and would pay for itself over its lifetime.

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    3.8.2 Manufacturing Process

    The main manufacturing processes are:

    creating the concrete slabs.

    attaching the lid and outlet pipes and ensuring it is airtight.

    building a shelter to house the biodigester and the inlet toilet.

    Concrete slabThe slabs them selves could come pre-fabricated but this would be an ex-pensive exercise, and would cause some safety concerns when trying to lowerfull size slabs into a hole.To ensure safety and also lower the cost, the slabs should be manufacturedon site, after the hole has been dug the bottom slab/oor should be poureddirectly into the hole and left to set, the wall slabs should then be con-structed from the bottom up, i.e. by the use of a wooden frame to holda 20-30 cm high ring of concrete to begin the wall section, taking care toensure the inlet piping is in place.once the walls have been nished and holes or splits in the joins can be lledwith some of the excess concrete.Airtight lid and outlet tubing

    Housing shelter for biodigester

    The housing shelter for the biodigester isnt covered in the scope of thisproject and shelter that minimises the effects of sun and weather is ade-quate.

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    3.8.4 Safety

    The biodigester will on its own help to improve the general cleanliness of thetownship, as currently all effluent and wastes are left on the roads or streets,the biodigester can safely contain biowastes and store them for periods of time long enough for all harmful pathogens to dissipate.Although there are some safety concerns that needed attention and haveaffected our design.

    Risk of re damage and explosion from storing ammable gasses

    leakage of gas into the air.

    leakage of the slurry into the earth.

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    3.9 Applications of biproducts

    3.9.1 Fertilizer

    FARAI

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    3.9.2 Gas

    FARAI

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    3.9.3 Cooking Technologies

    FARAI

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    3.9.4 Lamps

    FARAI

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    3.10 Materials and Methods

    3.10.1 Materials Available Locally

    Clay

    Pebbles

    Rocks

    Using resources locally available will save on transportation costs of suchmaterials. The clay pebbles and rocks which are all present in the area canbe used in the cement mixing process.

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    3.10.2 Materials to be Imported

    Cement mixture.

    Concrete mixer.

    Digger for pits. Materials for toilet.

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    3.10.3 Methods of Manufacture

    An underground pit must be dug.

    Cement mixers must be used to make the concrete for the walls.

    Walls must be made waterproof Concrete must be poured well toensure this is true.

    A minimum of two tanks will be created.

    A concrete slab must also be poured.

    A semi-portable toilet must be manufactured.

    There are two ways the concrete can be mixed.We can employ the use of large scale concrete mixers, as in cement mixingtrucks to pour the concrete. However, this requires skilled labour to operateand pour the concrete, but the nal result will be a very professional, strongand waterproof pour. At this scale, pouring the concrete will also need tobe done in a well thought out and organised manner.The second method is that of using small scale mixers. This allows the com-munity to get involved in the project and do some of the work themselves,which will help them gain a sense of ownership in their projects as well.However, using unskilled labour in the cement mixing process can lead to

    less than satisfactory concrete being poured, which leads to leakages in theconcrete and a much shorter life-span for the Biodigester.There are two ways of pouring and setting the concrete, each has benetsand each has hurdles that must be overcome.The rst way is to pour the concrete into moulds for each wall and, aftersetting, move each section together to create the container. However, thereare two main problems foreseen in this method. The rst problem is thatthe heavy concrete will need to be moved into place, which means that aheavy duty crane is required. The second problem is what method will beused to create a watertight seal between each individual concrete block.The second way is to manufacture a mould (probably created out of wood or

    similar) that outlines the entire container which the concrete will be pouredinto. This means that once the correct size pit has been dug, the mouldcan be placed into the hole, concrete poured into the mould and then, onceset, the mould can be removed and the container is in one piece, ready touse. The main problem is the manufacturing of the mould as if it is notdone on-site; it will need to be transported into Devikulam. Consideringhow to get the mould out of the pit after the concrete has been set is an-other aspect that needs to be considered. It is important for the concreteto be poured at the same time, as this will create a watertight pour in one go.

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    4 Implementation

    4.1 Implementation Plan

    The Biodigester we have designed is intended to be used by around 20 peo-ple each, as well as be able to contain their food wastes and their animalsbiological waste. As such we have decided to have a Biodigester for everygroup of 20 people in the village. While this could be costly, it would be themost efficient way of managing the system.The Biodigester system consists of two tanks, a toilet for human waste, amixer for cow dung and organic waste, and multiple pipe systems. Onefor delivering the waste into the tank, another for retrieving the generatedBio-Gas and another for retrieving the fertiliser after the 6 month disease-ridding phase has passed.The basis of the tank was conceited to be a cube made from concrete withouta top face. However, using Geometry formulae and Calculus concepts, thedimensions belonging to the smallest possible Surface Area for an estimatedVolume value were calculated. An estimated 9125L is required, so we werehence able to able to calculate the nal values of the design, which ended upto be a more rectangular shape. These values can be seen below in Figure4.1.A.

    INSERT FIGURE HEREThe piping system from the tanks are intended to come out onto a slab of concrete, upon which the toilet and mixer system is to be built upon. Thetoilet and mixer system are to have their own pipes, but will both feed intothe input pipe of the tank. The mixer is considered to be placed outside thetoilet area, which would allow them to put their scraps into the mixer with-out having to disturb anyone in the toilet. A piping system is also requiredfor the gas output and the fertiliser output, which would be placed outsidethe toilet area as well. Furthermore the system is to be modular, i.e. a setof pipe systems per tank. This is benecial to the community due to moneybeing saved on creating and maintaining an automated system.In order to have the system culturally accepted by the village, it would bewise to introduce the system to the higher class citizens before the lower classcitizens. If the higher class citizens are able to use and accept the system,its much more likely that the lower class citizens will begin using it as well.If we were to introduce it to the lower class citizens rst, the higher classmay look down upon the system and hence will not be culturally accepted.

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    4.2 Construction Process

    One of the most fundamental parts of the Biodigester is the storage tank sys-tem, as such they are to be installed rst. The tanks are to be installed un-derground with a small section visible above ground (roughly 10cm height)to allow easy access for usage, as well as in the event of maintenance. Assuch, holes of appropriate size for the tanks are to be dug rst. From Fig-ure 4.1.A above and taking into consideration the extra height and 10cmthickness, the holes need to be 2.83m by 2.83m by 1.42m. As two need tobe dug, it would be appropriate to have them a few metres away from eachother. These calculations for the hole and the amount of concrete neededcan be seen in gure 4.2.A below.Figure 4.2.A - Calculations for hole depth and concrete required.

    INSERT FIGURE HEREHoles for the pipes will also need to be dug, two for each tank. These pipeswill be the waste pipe and the pipe for retrieving fertiliser, as such it needsto be down near the bottom of the tank. The hole should be approximately1.04m deep, such that it is 3/4 of the way down the side of the tank.The tanks are to be made of concrete, due to their high strength and isola-tion for a signicantly cheaper cost. The concrete is also locally available,making possible maintenance down the line much easier to carry out forlocal villagers. Furthermore, small pebbles or stones are to be mixed withthe concrete, making it even stronger. The tanks are to be made initiallyby pouring 803 Litres of concrete into the bottom of their holes to create abase for the rest of the tank to be built upon.The walls are then to be created also using 559.75 litres of concrete each.The pipes are to be positioned into their correct position such that they willprotrude through both sides of the tank before carrying out this process, sothat the concrete will form around the Pipe and create an airtight seal toprevent leakages and cracks, as well as preventing the complexity of addinga pipe after the tank has been formed.The lid for the Biodigester is to be made out of a heavy duty plastic, suchas a PVC plastic sheet. Piping needs to pass through this layer too, so a

    hole of appropriate size is to be cut through the middle. This could causeleakages, so some safety measures need to be added. The piping is to bethreaded on both sides such that a nut and washer can be screwed on. Alayer of hard rubber is also added between the washer and plastic, such thatair cannot escape around the tube.This layer of heavy duty plastic is then to be stretched over the top of thetank and secured over the sides using the same method as above, i.e. thecombination of hard rubber, nuts and washers. As above, this will reducethe possibility of leakages while still producing a strong joint.As mentioned in the implementation plan, the pipes are to come out onto

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    a slab of concrete, upon which the toilet and outside mixer system will be

    constructed. Assuming the slab is to go straight over the tank system withthe tanks separated by 2m, we would need a slab of size 2.83m by 7.66m. Foran estimated 10cm depth, we would need 2168L of concrete. This concreteis to be poured around the installed pipes so that it produces a strong andairtight seal.Once the piping has been laid down such that there is toilet piping inside thetoilet area, with the mixer piping outside along with the two output piping,the toilet, mixer and output systems can then be installed. The processesof these will be covered in a later chapter.After all the piping has been created, the toilet area can then be constructed.It is beyond the scope of this project for the exact method of construction

    for this building, however it is highly recommended that it be made out mudthatch like their houses, as it uses skills already in the community.

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    4.2.1 Methods of Installation and Labour Considerations

    The labour of the building and installation process can be very intense. Itrequires numerous holes to be dug, concrete to be mixed and formed intothe correct shape, holes to be cut, screws to be tightened and the inputs of the system (toilet/mixer) to be produced.The labour of these can be managed in various ways. For the most partthe jobs can be carried out by the local villagers, drawing upon some of their skills. The holes are not extremely deep and could be successfully dugby villagers using a simple shovel. Using some form of cutting tool, holescould also be cut in the PVC pipe by the villagers. The villagers, given thecorrect instructions, could also assemble the rest themselves too. Despitethe possible inaccuracies, this could give the village an insight into how it ismade and thereby be able to perform maintenance by themselves. This isall assuming that the villagers have access to these materials from anothertown, and can get it delivered to them.Another way of managing the labour is to get the materials sent to thempre-made, i.e. with all the holes and rubber cut to the appropriate size,as well as all the nuts. The only exception to this would be the concrete,due to the immense size and weight of the material. This method would bebenecial, as it still allows the community to assemble, but in this case withmore accuracy.The third and least likely option is to hire workmen and a delivery serviceto drop off the materials and for the workmen to then build it. This wouldnot be appropriate for the village due to the costs for such service, as well asthe villagers having no knowledge of how to do maintenance, meaning theworkmen would have to be contacted every time maintenance is required.

    From the above options, the most benecial option for the village is theoption of having the parts pre-cut and given to the village. This allows forthe accuracy in the build to help prevent leakages and other errors, whilealso giving the community the background knowledge of the system in orderto perform maintenance when required. Helping to build and maintain thesystem could also generate employment and also generate a sense of com-

    munity among the villagers.

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    4.3 Education Schemes

    4.3.1 How does the Biodigester work?

    Based on the data provided by EWB and other information collected, wecame to an understanding that the average level of education of the villagersis not that high. The level of literacy is not commendable. Hence, we havedecided to develop a scheme of teaching wherein more importance is givento pictures, videos and spoken documentaries so that even a layman villagercould understand the processes which take place in the functioning of thebiodigester.The most important barrier that needs to be overcome in the implementa-tion phase of the project is to educate the villagers of the benets of the

    biodigester and bring an end to their beliefs. Since most of the villagers arefrom a backward caste, they might nd the idea of cooking from the gas pro-duced using their own a waste a bit revolting. This concept of eating fromenergy produced from pooh or human waste to say in layman terms is bittoo advanced for a village community such as theirs. In order to overcomethis barrier, the aforesaid techniques can be adopted wherein the detailedworking of the biodigester can be better understood by the community as awhole.The biodigester is designed to be used by at least 2-3 families in order togrow a sense of understanding and sharing among the community whichmight later help to ease the tension which developed among the various

    castes years before.Another barrier in educating them is going to be the language barrier. Thiscan be overcome by making use of educated volunteers from the locality thatcan also act as a bridge between the community and the project and linkthem with all the details and facts associated with the project.We have devised a way to tackle the process of educating the community indifferent levels and aspects by dividing the process into 4 main parts andthen attacking the target groups which come under the radar of that part.Sanitation is a part which concerns the whole community hence we addressit as a community issue and then move into individual households to giveit a more precedence. Energy or Gas System is another part wherein thetarget group is women because they do most of the cooking in rural India,hence they need to be educated at rst and then we move onto family as awhole. Fertilizer is a farming matter hence farmers and the labourers needto be educated in this matter at rst because they handle it most. Lateron the whole community is educated on the aspect. Safety, which is majorconcern, should be tackled in a careful way. For this we recommend the helpof children as they are the future and can help in invigorating safety valuesinto the family. All this is better explained in Fig. 1 shown below.

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    INSERT FIGURE 1

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    4.3.2 Sanitation

    Sanitation is an important concern in the working of a biodigester and onewhich needs the greatest attention. Working in a community where thelevel of understanding or literacy is of a low level, it is of utmost importanceto devise a study plan which can penetrate into the hearts and mind of the common man and help them understand the necessity of practising safesanitation procedures. Based on the statistical data provided by the EWBnearly 500 households dont have access to a latrine and hence are unawareof safe sanitation practices. This is a major concern which can be addressedby introducing our biodigester into the community and thereby teachingthe community as a whole in safely disposing of their waste and in turngenerating energy from it.

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    Table 1: Population and literacy in India according to the 2001 census*Total Scheduled castes Scheduled tribes

    (in millions) (in thousands) (in thousands)Enrolment Male Female Total Male Female Total Male Female Total

    Primary (1-5) 69.7 61.1 130.8 13762 10995 24757 7367 6369 13737Middle (6-8) 28.5 22.7 51.2 5100 3597 3597 2395 1776 4171Senior (9-12) 21.7 15.4 37.1 3228 3228 5218 1290 795 2085

    4.3.3 Gas Power

    One of the main benets of the biodigester other than disposing of the hu-

    man waste is producing methane gas which in turn can be used as a fuelsource. This novel idea might take some time to digest into the hearts andminds of the villagers. As the villagers still have caste distinctions andother discriminations among them, they might nd this to be a bit offend-ing to their traditional and cultural practices. To tackle this scenario, asuitable and understandable educational approach needs to be taken. C. GWankhede (2010, Pg 4.) in a recent study has stated that lower literacyand high dropout rates among lower caste populations is in turn a naturalcause for their poverty and underdevelopment. The statistics provided bythe EWB (2011) website also underlines this fact which is elaborated in Fig2.

    INSERT FIGURE 2G.C Wankhede(2010, Pg 4.) also states in his article that SCs and STsare considered the most backward sections of Indian society in terms of ed-ucational development which he reiterates again using a second table(G.CWankhede, 2010, Pg 5.)(Fig 3.)

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    4.3.4 Fertilizer

    One of the main benets derived from a biodigester is that the waste prod-uct from the digester is highly rich in nutrients and hence can be used asfertilizer in the elds. The village already has a forestation project as wellas many medicinal herbs growing around it. This can be used to improvetheir growth; also the villagers can use it in their elds and make their pro-duce more organic by freeing it from the clutches of chemical fertilizers. Allthese facts need to be incorporated into the educational system envisagedto educate the community about the biodigester.

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    4.4 Safety Issues

    The most important concern with using biodigesters is the safety factor. Alittle carelessness might lead to a big disaster which is why educating thevillagers in matters of safely operating the biodigester is an important partof this project. A set of explanatory slides showing the effects of bad oper-ations is going to be aired and explained to the villagers with the help of alocal resource person. Another way of getting into the minds of the villagersis by means of documentaries and short dramas depicting stories of mishapswhich might occur due to the bad operation of the digester and the gassystem. The statistics provided by EWB design brief(2011) depicted in Fig4., also shows that more than 50% of the villagers own a television whichreinforces the fact that televising these skits or dramas is a better way toget into the minds of the villagers.

    INSERT FIGURE 4This is also a better way of getting the matter into the minds of the com-munity and especially into the womenfolk because in the village, women doall the cooking.

    5 Evaluation

    TEAM at end

    5.1 Team Evaluation of Biodigester

    5.2 Feasibility of Biodigester

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    6 Conclusion

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    7 Summary

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    References

    References

    [1] Lamport, L 1994, LAT E X: A Document Preparation System . 2nd Edi-tion, Addison Wesley, Massachusetts,