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Final Design Document 1 Final Design Document 1 Document Transcript

  • Table of Contents List of Figures……………………………………………………………………………iii List of Tables……………………………………………………………………………..iv 1. Problem Formulation .............................................................................................................. 1 1.1 Introduction ........................................................................................................................... 1 1.2 Objective ............................................................................................................................... 1 2. Problem Analysis and Literature Review ............................................................................... 1 2.1 Introduction ........................................................................................................................... 1 2.2 Problem Analysis .................................................................................................................. 1 2.2.1 The Input ........................................................................................................................ 2 2.2.2 The Output ..................................................................................................................... 2 2.2.3 Solution Variables .......................................................................................................... 2 2.2.4 Criteria ........................................................................................................................... 3 2.2.5 Usage.............................................................................................................................. 4 2.2.6 Production Volume ........................................................................................................ 4 2.3 Introduction to Literature Review ......................................................................................... 4 2.3.1 Flush toilets, dry toilets, and Composting Toilets. ........................................................ 4 2.3.2 Known Conditions of Project Location ......................................................................... 4 2.3.3 Client Stipulations.......................................................................................................... 5 2.3.4 Composting Conditions ................................................................................................. 5 2.3.4.1 Temperature ............................................................................................................ 5 2.3.4.2 Moisture .................................................................................................................. 5 2.3.4.3 Aeration................................................................................................................... 6 2.3.5 Additives ........................................................................................................................ 6 2.3.6 Quality of Compost End Product ................................................................................... 6 2.3.6.1 Importance of Air Flow .......................................................................................... 6 2.3.6.2 Benefits of Urine Inclusion ..................................................................................... 7 2.3.6.3 Other Important Factors .......................................................................................... 7 2.3.7 Pathogen Concerns in Fecal Compost ........................................................................... 7 2.3.7.1 Thermophilic Composting ...................................................................................... 7 2.3.7.2 Specific Temperature Requirements ....................................................................... 7 2.3.8 Odor ............................................................................................................................... 8 i
  • 2.3.8.1 Smell diagnostics .................................................................................................... 8 2.3.8.2 Vent Airflow ........................................................................................................... 8 2.3.8.3 Venting .................................................................................................................... 9 2.3.9 Toilet designs ................................................................................................................. 9 2.3.9.1 Composting Privy ................................................................................................... 9 2.3.9.2 Compost Toilet with Axial Rotation ..................................................................... 10 2.3.9.3 Drum Privy............................................................................................................ 10 2.3.9.4 Sunfrost Batch Composting System ..................................................................... 11 2.3.10 Local Laws and Codes ............................................................................................... 11 3. Alternative Design Solutions ................................................................................................ 12 3.1 Introduction ......................................................................................................................... 12 3.2 Brainstorming ..................................................................................................................... 12 3.3 Alternate Designs ................................................................................................................ 12 3.3.1 Sunfrost ........................................................................................................................ 12 3.3.1.1 High Chair ............................................................................................................. 13 3.3.1.2 Cork Screw Mixer ................................................................................................. 13 3.3.1.3 Rolling Dolly ........................................................................................................ 14 3.3.1.4 Crank Mixer .......................................................................................................... 15 3.3.2 Biolet ............................................................................................................................ 16 3.3.3 Axial Rotation .............................................................................................................. 17 3.3.4. Composting Privy ....................................................................................................... 18 3.3.5 Anaerobic Digester ...................................................................................................... 19 4. Decision Phase .......................................................................................................................... 20 4.1 Introduction ......................................................................................................................... 20 4.2 Criteria Definitions ............................................................................................................. 20 4.3 Solutions ............................................................................................................................. 21 4.4 Decision Process ................................................................................................................. 22 4.5 Final Decision Justification................................................................................................. 23 5. Specification of Solution.......................................................................................................... 23 5.1 Introduction ......................................................................................................................... 23 5.2 Solution Description ........................................................................................................... 23 5.2.1 The Waste Containers .................................................................................................. 23 5.2.2 Barrel Lids ................................................................................................................... 25 5.2.3 Ventilation.................................................................................................................... 26 ii
  • 5.2.4 Step Box ....................................................................................................................... 27 5.3 Cost Analysis ...................................................................................................................... 27 5.3.1 Design Costs ................................................................................................................ 27 5.3.2 Construction Cost......................................................................................................... 28 5.3.3 Maintenance Cost......................................................................................................... 28 5.4 Implementation Instructions ............................................................................................... 29 5.4.1 Overview ...................................................................................................................... 29 5.4.2 Barrel setup .................................................................................................................. 29 5.4.3 Stage One ..................................................................................................................... 30 5.4.4 Stage Two .................................................................................................................... 30 5.4.5 Stage Three .................................................................................................................. 30 5.4.6 Emptying and Cleaning................................................................................................ 30 5.5 Prototype Performance........................................................................................................ 30 6. Appendices ................................................................................................................................ 31 Appendix A – Brainstorming Notes ......................................................................................... 31 Appendix B - References .......................................................................................................... 37 List of Figures Figure 1: Black Box Model............................................................................................................. 1 Figure 2: Diagram of the Sunfrost Design .................................................................................... 14 Figure 3: Diagram of the Rolling Dolly Design ........................................................................... 15 Figure 4: Diagram of the Crank Mixer Design ............................................................................. 16 Figure 5: Diagram of the Biolet Design ........................................................................................ 17 Figure 6: Diagram of the Axial Rotation Design .......................................................................... 18 Figure 7: Diagram of the Composting Privy Design .................................................................... 19 Figure 8: Diagram of the Anaerobic Digester Design .................................................................. 20 Figure 9: Inside view of Barrel ..................................................................................................... 24 Figure 10: Outside view of Barrel ................................................................................................ 24 Figure 11: Stage One Lid .............................................................................................................. 25 Figure 12: Stage Two and Three Lid ............................................................................................ 26 Figure 13: System Layout ............................................................................................................. 26 Figure 14: Project Hours Pie Chart ............................................................................................... 27 iii
  • List of Tables Table 1: Composting Privy Pros and Cons ................................................................................... 10 Table 2: Compost Toilet with Axial Rotation Pros and Cons ...................................................... 10 Table 3: Drum Privy Pros and Cons ............................................................................................. 11 Table 4: Sunfrost Batch Composting System Pros and Cons ....................................................... 11 Table 5: Delphi Method Chart ...................................................................................................... 22 Table 6: Materials Cost ................................................................................................................. 28 Table 7: Maintenance Cost ........................................................................................................... 29 Table 8: Usage Costs .................................................................................................................... 29 iv
  • 1. Problem Formulation 1.1 Introduction The first phase of the design project is to create a Black Box model this is shown in Figure 1. The Chocolate Factory, along with the help and cooperation of the CCAT will be able to create a composting toilet that will be used by the people residing in the CCAT house. INPUT: OUTPUT: No useable system to A useable system to demonstrate and educate BLACK BOX demonstrate and educate public of a composting public of a composting toilet at the CCAT house. toilet at the CCAT house. Figure 1: Black Box Model The Black Box model above is the first step in determining what how our design project is going to contribute to the CCAT house. 1.2 Objective Our objective is to design and implement a useable composting toilet that will be added to the infrastructure of the CCAT house, which will demonstrate and educate the public about a composting toilet system. 2. Problem Analysis and Literature Review 2.1 Introduction The design problem is to design and install a working composting toilet for the CCAT house to use and educate visitors about composting toilets. The problem analysis states the input variables and their constraints, the output variables and their constraints, the solution variables and their restrictions, and the criteria and their constraints used to judge designs. The Literature Review will show the information relevant to building a composting toilet. 2.2 Problem Analysis 1
  • 2.2.1 The Input CCAT is currently using freshwater to discard fecal matter wasting water and nutrients. Input Variables:  CCAT resident knowledge of composting.  CCAT visitors knowledge  Users for the toilet  Range of ambient temperature  Materials Constraints:  CCAT residents have enough knowledge to properly use the toilet  No knowledge of composting toilets or experience with composting toilets  Less than or equal to three users  Between 50-70°F  High fecal contents 2.2.2 The Output A useable composting toilet system, at the CCAT house, which helps demonstrate and educate public about composting toilets. Output Variables:  CCAT resident knowledge about composting toilet  CCAT visitors’ knowledge  Compost quality  Material Constraints:  CCAT residents have enough knowledge to properly use the toilet  Knowledge and/or experience is gained  No longer hazardous waste  Low fecal content 2.2.3 Solution Variables Solution Variables:  Compost per cycle  Size 2
  •  Ventilation  Composting process  Human interaction  Type of thermal measurement Restrictions:  Moveable by two people  Must fit in 6’ by 10’ storage room  Must vent to outdoors through exterior ceiling vent  Process must be aerobic to efficiently change into compost  No direct exposure to unprocessed compost  Must be able to measure mass temperature 2.2.4 Criteria The criteria are ranked in order of importance and will be used to rank the potential designs. The constraints are the minimal requirement for specific criteria. Criteria: 1. Composting effectiveness 2. Safety 3. Odor 4. Cost 5. Difficulty of management 6. Grossness of management 7. Minimize space used 8. Positive presentation 9. Ease of construction 10. Resource appropriateness Constraints: 1. Must produce compost 2. Must kill harmful pathogens 3. No unacceptable odors released into living areas 4. Less than 325 dollars 5. Work must be reasonably accomplished by two people 6. No direct exposure to waste required 7. Must fit and function in the given area 8. Unconstrained 9. Must be built within our abilities 10. Client’s mission 3
  • 2.2.5 Usage The system will be used daily by the three residence of the CCAT house. 2.2.6 Production Volume One final solution of a composting toilet will be made. 2.3 Introduction to Literature Review The purpose of the Literature Review is to provide the group with background knowledge which will be sufficient in the process of determining and completing the design project. The topics within the literature review range from various types of composting toilets to what is required for appropriate composting conditions. 2.3.1 Flush toilets, dry toilets, and Composting Toilets. Flush toilets, using water as a carrying medium, take human waste and carry it to a central location for processing. This practice leads to water pollution and wastes nutrients that are excreted, mainly nitrogen (Stoner 1977). A dry toilet is a toilet that will accept human waste and store it, without the addition of water. One example of a dry toilet is pit toilet, such as an outhouse. A composting toilet is another form of a dry toilet; however, with a composting toilet the human waste is turned into compost, which can then be used as a soil amendment for plants. The purpose of a composting toilet is to reduce or eliminate water contamination and to reuse human waste as a soil amendment (Stoner 1977). 2.3.2 Known Conditions of Project Location The composting toilet that will be designed is to be used in a two-story home in Arcata, California, on the campus of Humboldt State University. Humboldt County is a moderate climate with heavy precipitation and high relative humidity. There is to be three people using the composting system (Haskett 2009). According to Professor Minnis of Pace University a study has shown that the average human excrement output is 120 grams per day of feces and 1.1 liters of urine per day (Minnis). Therefore an estimate of 360 grams of solid waste per day will enter the system. If urine is disposed of through the system to be designed it will require the inclusion of an estimated 3.3 liters per day. A toilet is already in place in the upper story of the home with an uncompleted chute leading down to a storage room in the basement. This same room will be available for the use of the composting system (Haskett 2009). A space of five feet by six feet with nine vertical feet is available (Haskett 2009). Access to this room is through a hallway. The room touches one exterior wall. It is likely that a location outside the building could be made available for fully or mostly processed compost (Haskett 2009). 4
  • 2.3.3 Client Stipulations The users of this composting toilet system need a design that will be effective in function, production, and demonstration of an appropriate technology. Minimal human interaction required to operate the system on a day to day basis is ideal. Energy consumption should be low or non-existent. The work required to move the system and remove the compost should be safe, simple, and not require difficult work (Haskett 2009). 2.3.4 Composting Conditions The conditions inside the composting toilet will determine to a large extent the overall effectiveness of the system. The conditions will determine: how long it will take to complete the process, how safe the final product will be, and the smell produced by the system. The conditions of a compost pile are all interconnected and one condition will affect the others (Jenkins 2005). There are many different types of microorganisms that live in the compost that are responsible for the decomposition process (Jenkins 2005). Making sure these organisms have enough oxygen for the process to remain aerobic is significant. Decomposing releases heat which is important for making the process continue quickly and also necessary to kill harmful pathogens (Stoner 1977). The ratio of carbon to nitrogen (C:N) should remain high, around 30:1, to help the pile heat up and keep odors from nitrogen compounds minimal (Leary 2007). 2.3.4.1 Temperature The organisms in a compost pile thrive in various different temperatures, which make some more potent than others. Mesophiles live at medium temperatures between 68- 113ºF (20-45ºC). Thermophiles thrive above 113ºF (45ºC). psychrophiles grows best at temperatures around 59ºF (15ºC) (Jenkins 2005). Compost temperatures must rise significantly above the temperature of the human body (37ºC or 98.6ºF) in order to begin eliminating disease-causing organisms (Jenkins 2005). 2.3.4.2 Moisture Moisture is necessary for the decomposition process and a dry pile of compost will take longer to break down (Jenkins 2005). Too much water in the compost pile will displace oxygen and prohibit aerobic conditions (Stoner 1977). The loss of aerobic conditions due to too much water would lead to an unproductive mass that could not be used as compost. The moisture content of compost should be around 65% (Jenkins 2005). Organic wastes with good moisture contents should feel damp, but not soggy (Stoner 1977). The average human excretes 1.0 liter per day of urine at 95% water and 200 grams of feces per day at 72% water (Stoner 1977). Evaporation will remove some of the extra water, but a carbon based bulking agent is necessary to absorb moisture (Van der Ryn 1978). 5
  • 2.3.4.3 Aeration Oxygen and proper aeration is critical for aerobic conditions. Not enough oxygen will cause anaerobic conditions, which causes slower decomposition, foul odors, and may cause the compost to not produce enough heat to kill all harmful pathogens (Jenkins 2005). Aeration should provide adequate oxygen and oxygen distribution throughout the compost. Aerating the system will involve vents for fresh air, airflow around pile, adding a bulking agent to create air pockets, insuring proper moisture levels, and mixing or turning the pile (Van der Ryn 1978). Some composting toilet designs have vents that are underneath, or buried, to increase airflow to the bottom of the pile. If the compost is kept in a hard to access container, such as a 55-gallon drum, mixing the pile can be difficult. Some solutions to this problem involve spinning or rotating the drum, using a stirring mechanism, or removing the contents of the drum for final composting (Stoner 1977). 2.3.5 Additives Bulking materials are an essential part of a composting toilet’s process, to insure decomposition is done correctly and safely. For the best compost we must add a sufficient amount of carbon- based bulking material (Jenkins 2005). This will allow the compost to have proper moisture levels and be able to decompose correctly. Possible bulking materials include: sawdust, peat moss, straw, or weeds. Another possible factor to the compost additives is urine, if both feces and urine are in the system that will require more organic material to help break down the extra nitrogen entering the system. Before using the composting chamber, it should be partially filled with bulking material and completed compost in order to create an absorbing system and start the composting process. Not only can bulking materials are added to the compost, food scraps, egg shells, paper and cardboard, lawn clippings and other small garden trimmings, clothes from natural fibers and disposable cotton diapers and tampons (without the plastic tags) could also be added if desired (Composting Toilet World 2009). Chemicals and other non-organic items should not be added to the toilet (Van der Ryn 1978). 2.3.6 Quality of Compost End Product Compost from human excrement is of great value for use in agriculture. Composted human waste, especially if urine is included, can have a nutrient content equal to that of chemical fertilizers (Oikos 2009). A very high percentage of valuable minerals taken in with food consumption will be available in the final product for use by the plants on which it is distributed. Nitrogen is recycled less efficiently during this process than other minerals, but still a significant percentage is made available for reuse by plant life (Sunfrost 2004). 2.3.6.1 Importance of Air Flow To promote nitrogen retention it is important to allow for sufficient oxygen exposure to the mass because with little oxygen much of the nitrogen will be converted to ammonia (NH3) and lost (Anonymous 1993, 2009). Sustaining aerobic composition, done by allowing significant airflow, also promotes the survival of beneficial microorganisms (Anonymous 1993, 2009). 6
  • 2.3.6.2 Benefits of Urine Inclusion There is very significant mineral and nutrient presence in human urine. In the overall waste output of humans urine contains the majority of Phosphorus, Potassium and Nitrogen. Between fifty and ninety percent of these nutrients expelled by humans is held in the urine (Maurer 2003). These particular elements are very important in a fertilizing product; making inclusion of urine in the composting process is a significant benefit (Sunfrost 2004). 2.3.6.3 Other Important Factors Among many different criteria for compost quality is the concern about of sharp or large non- organic materials. Also considered essential is a proper C:N ratio in the finished product. A good method for promoting balance is to mix plant matter, high in carbon, with a manure-based compost, which is often high in nitrogen (California Integrated Waste Management Board). 2.3.7 Pathogen Concerns in Fecal Compost There are dangerous amounts of bacteria and other potentially dangerous microorganisms in fecal matter, especially that of humans. Human excrement can contain numerous bacteria, viruses, and parasites (Kaiser 2006). Before the composting process there are serious concerns about the health risks of handling, storing or spreading human excrement. Through the processes that occur during composting these potentially harmful pathogens can be eliminated with sufficient effectiveness to make the use of the resulting compost safe (Jenkins 1994). Human pathogens are not adapted to prolonged life outside the human body. A very effective method for eliminating pathogens in human excrement is sustaining a temperature high enough to promote thermophilic bacterial activity (Jenkins 1994). The required temperature for effective thermophilic activity is above 1130 F (Oikos 2009). 2.3.7.1 Thermophilic Composting The key process that which destroys pathogens is thermophilic composting, which is the heating up of the material due to the natural composition process. When certain temperatures are reached and sustained nearly all harmful pathogens will be eliminated. According to Dr. T. Gibson, Head of the Department of Agricultural Biology at the Edinburgh and East of Scotland College of Agriculture, evidence shows that a few hours at 120 degrees Fahrenheit would eliminate [pathogenic microorganisms] completely. There should be a wide margin of safety if that temperature were maintained for 24 hours (Jenkins, 2005). Compost piles will heat up and Jenkins states in his Humanure Handbook that a properly prepared mass of compost will reach the necessary thermophilic temperature on its own (Jenkins, 2005). 2.3.7.2 Specific Temperature Requirements A report connected with Penn State University, shows the results of a laboratory test on compost regarding the elimination of specific pathogens with human health concerns. When L. Monocytogenes, Salmonella, and E. coli were introduced to compost the results showed that these were virtually eliminated with particular temperatures over respective time periods. With 7
  • 1200 F for 36 hours, 1300 F for 8 hours, or 1400 F for one hour, all three organisms were deactivated (Weil, Beelman, and LaBorde). 2.3.8 Odor Odor and smell of human waste is a concern to people using a composting toilet. The smell comes from the gases released by decaying organic matter (Van der Ryn 1978). The main odorous gases are: organic sulfides, hydrogen sulfides, ammonia and other nitrogen compounds (Leary 2007). The most common source of foul odors from decomposing fecal matter is organic sulfides, which can be detected at low concentrations (Leary 2007). Organic sulfides are produced with or without oxygen; however they will decompose further to other less odorous compounds under aerobic conditions. Under anaerobic conditions the concentration of organic sulfides can be ten or more times higher than under aerobic condition (Leary 2007). Most of the nitrogen that is released from the decomposing fecal matter is released in the form of ammonia gas. Ammonia gas occurs under both aerobic and anaerobic conditions but is produced in greater concentration when the C:N ratio is 20:1 or lower. Raising the pH will also increase the amount of ammonia gas produced. The smell of ammonia can be detected at low concentrations; however it is not as foul as the organic sulfides and will also dissipate quickly (Leary 2007). Other nitrogen compounds that are released are amines and indoles. These nitrogen compounds have a putrid or decaying flesh smell. Amines and indoles are produced under both aerobic and anaerobic conditions but under aerobic conditions they will continue to decay. They are also produced in greater quantity when the C:N ratio is 25:1 and lower (Leary 2007). 2.3.8.1 Smell diagnostics Smell can give insight into how well the composting process is functioning. The most efficient way to deal with odor is to make sure the process remains aerobic (Obleng and Wright 1987). If the compost pile is too moist, or does not have adequate aeration, the process will become anaerobic and there will be a strong foul odor. Adding a bulking agent will absorb moisture and allow for more air pockets in the pile. Mixing or turning the pile also increases oxygen levels (Van der Ryn 1978). If the C:N ratio is lower than 20:1, there will be a stronger smell from ammonia and the other nitrogen compounds. Adding more of a carbon based bulking agent or limiting the amount of urine going into the system will raise the C:N ratio and lower the smell of ammonia and other nitrogen compounds (Stoner 1977). 2.3.8.2 Vent Airflow A vent needs air flowing over the opening in order to create a pulling effect that will suck air out of the vent. If the vent goes up through the roof, the vent opening should be located in a place that gets adequate airflow. Chimneys, other vents, and tall trees can affect air flowing over vent opening (Stoner 1977). Bends in the pipe and sudden changes in the pipe diameter can also cause reduced airflow through the system (Pescot and Price 1982). There should be an air intake vent in the system to supply the compost with fresh air for oxygen. This vent should supply the bottom of the pile with oxygen. Air being sucked out of the top vent should then suck air in through the lower vent. Not enough airflow through the system can cause odors to back up and 8
  • leak into the bathroom. To increase airflow an electric fan can be installed in the roof vent, sucking air out of the composting chamber (Stoner 1977). Some vent tops can maximize the venture effect by their shape and increase air flow by up to 40% of a straight pipe opening (Pescot and Price 1982). The venting system needs to be designed so that the chamber is at a lower pressure than outside, which will insure air is sucked into the chamber rather than leaking out (Stoner 1977). 2.3.8.3 Venting The system will need to be vented for two reasons, gases will be given off during the decomposing process, including water evaporation, and oxygen will need to be present for the process to work efficiently. The system should be sealed so that the only ways into the composting compartment is from the toilet or through vents. The toilet seat lid should be lined with a sealer, like rubber, and be kept shut. The vents should have mesh screens small enough to keep out small flies. All vents should also be hooded so that water cannot get in and minimize sunlight to avoid flies (Van der Ryn 1978). For odor control purposes, the vents should be placed away from people, for example above the roof. Venting away from people will allow the odorous compounds given off by the composting process to dissipate and reduce odor (Leary 2007). Gases rise, so a vent should be placed high in the composting compartment, even higher than the toilet seat if possible, to avoid gases escaping through the toilet seat (Stoner 1977). 2.3.9 Toilet designs Several different designs of composting toilets exist; the following sections contain information on Composting Privy, Compost Toilet with Axial Rotation, Drum Privy, and Sunfrost Batch Composting System. 2.3.9.1 Composting Privy One design, the Farallones Composting Privy by Sim Van der Ryn in The Toilet Papers. This toilet, or privy, consists of a lower chamber, built out of bricks 3'4” tall on a 4'x'8' concrete slab. The front wall is not built out of brick to allow access. This lower chamber is divided into two compartments, with the idea that one compartment is being used as the toilet, while the other compartment has been filled and is composting. The top of the chamber has a 2”x4” wood frame on which a 1/2” sheet of plywood can be attached, which will serve as the toilet room floor. This plywood sheet should have a hole cut in the floor over each sub section (or you could cut one hole, and just rotate the plywood sheet half a turn when one section is filled). The privy also needs a 10” diameter vent to allow gases and water evaporation to escape. The brick sub frame should be lined with a strip of wood (2”x6”) or weather stripping so that the system can be sealed. Each chamber should have a 6” high lip (brick or concrete) to avoid water from seeping out. Each chamber should have both an outside wood panel door and a chicken wire baffle, placed on top of the 6” lip so that the compost does rest upon the wood panel door. The wood panel door should have a venting strip cut in the bottom. All vents should have a wire or mesh screen to keep bugs and animals out and should also have a hood over the vent to keep rain out and sunlight out, to discourage flies. Toilet seat cover should seal and be kept closed. If climate is too cold to allow piles to heat up, add an insulator, plywood for example (Van der Ryan 1978). 9
  • Table 1: Composting Privy Pros and Cons Pros Cons Simple Requires a structure external to house. (Can be connected to house, but must have clear access to front) Easy to use, maintain, and easy access to Depending on how long composting process compost. takes, may require additional storage areas Sufficient size for family of four 2.3.9.2 Compost Toilet with Axial Rotation The Compost Toilet with Axial Rotation combines the composting unit and toilet into one structure. The top of the unit has a typical toilet seat feeding directly into the composting area. Inside the unit is a horizontal drum with an axial shaft inside. This shaft connects to a simple gear and crank to allow for easy rotation of the mass inside. This rotation promotes aeration and moisture uniformity. The drum is not solid, allowing for air intake and for excess water to leave the mass. A separate chamber will collect excessive moisture and allow efficient evaporation. Another separate chamber inside the compact unit is used for final processing of the compost. By rotating the drum in the direction opposite that used for aeration about one third of the drums capacity is released into an isolated area. No longer in contact with fresh excrement this material will compost to the point that it can be safely handled and removed (Tinseth 2002). Table 2: Compost Toilet with Axial Rotation Pros and Cons Pros Cons Compact design easily fits into available space Low capacity Low amount of operation work required Compost handled in lavatory area Drum rotation good technique for proper Final Compost near fresh waste conditions 2.3.9.3 Drum Privy The drum privy is a toilet design that uses a 55-gallon drum to collect the excrement and store it to allow for composting. The drum is set on a scissor jack on a rolling cart underneath the floor of the toilet room. The drum is then jacked up so that it is sealed against the floor of the toilet room. The toilet should be a plastic lined tube that tapers out going from the seat to the floor and protrudes through the floor about an inch. The final diameter must be smaller than the drum diameter so that it will fit inside the drum. There should be a 4-6” pipe venting from the toilet through the roof. Vent should be painted black to increase airflow and have a mesh screen and hood on top. In colder climates the pipe should be insulated to avoid condensation from dripping down the pipe. The drum should have a 2” diameter hole 2” from the bottom. A polyvinyl (PVC) venting pipe shaped, as a “U”, should be placed through this hole. The pipe should extend up the side of the drum to the top both inside and out. The half of the vent pipe that is inside the drum should be perforated all the way down to the bottom and capped at the top. The 10
  • half outside the drum should have a mesh screen to keep bugs out of the system. For composting, paint drums black to increase heat absorbed from sun. Drums should be rolled each week to stir compost and increase aeration. Contents of drums can also be dumped out to compost outside. (Van der Ryn 1978) Table 3: Drum Privy Pros and Cons Pros Cons Simple and cheap Adequate aeration can be a problem Drum makes for easy transport and storage Requires ability to move full 55-gallon drums Aeration Weekly work is required for rolling the drums 2.3.9.4 Sunfrost Batch Composting System The Sunfrost Batch Composting System is the type that was previously used in the CCAT house. The Sunfrost composter incorporates a 55-gallon drum as the main container. The system is insulated, sealed and connected to a toilet through a simple vertical chute. The drum was designed to be filled to a desired capacity and then removed from the toilet so that the composting process can take place without more excrement being added. It is necessary to have at least two barrels for the system to continuously function. The system has a grate above the bottom of the barrel so that liquid that leaches to the bottom will escape. A simple hand pump is then used to recycle the liquid to the top of the mass. Before pumping the liquid, a proportionate amount of dry additive can be placed on the top of the pile to attain a proper moisture level. To promote aeration a mesh screen lines the hole barrel inside to create air passage around the entire mass. The system also includes a simple hand mixer to stir the pile. An air intake funnels the fresh air to the bottom while the exhaust pulls air from the top, promoting aeration and effectively reducing odor. A low power DC or AC fan is used to ensure proper airflow (Sunfrost 2005). Table 4: Sunfrost Batch Composting System Pros and Cons Pros Cons Many components already in possession, low Regular human interaction required cost Size and Capacity both suited to location Necessity of at least two systems Low energy use 2.3.10 Local Laws and Codes At this point there are no laws or building codes regarding composting toilets in either the city of Arcata or the state of California. According to Dean Renfer, Building Official for Arcata, there has never been a permit issued for a composting toilet or officially approved by the Building Department in Arcata. Mr. Renfer also said that composting toilet systems are not part of the California plumbing code (Renfer, 2009). 11
  • 3. Alternative Design Solutions 3.1 Introduction After analyzing the problems at hand and researching for a literature review on the problem our team has gained knowledge on the subject and various ways others have created a solution for composting human waste. Using that acquired knowledge and ideas gathered using group brainstorm sessions we have arrived at a number of alternative solutions, which have the potential to solve our problem. 3.2 Brainstorming Our group conducted a number of brainstorming sessions in order to produce ideas that could lead to entirely new solution methods or to improve upon solutions already known to the group. The first brainstorm we did was an open structure in which we sought ideas applying to the entire project. There were many and diverse suggestions that did lead to solution alternatives for our problem. Other brainstorming sessions were held with just a single specific solution variable per session. In narrowing the scope of the problem we were able to arrive at many more ideas that had not come up in the previous, less focused brainstorms. These idea sessions played a key role in producing the alternative solutions that are shown here. The actual written record of the brainstorms is shown in Appendix A. 3.3 Alternate Designs Below is a list of the alternate designs we came up with for our composting toilet system.  Sunfrost  Sunfrost Design with Toilet Chute  Rolling Dolly  Crank Mixer  Biolet  Axial Rotation  Composting Privy  Anaerobic Digester 3.3.1 Sunfrost The Sunfrost Design is the composting toilet developed by Larry Schlussler, and was previously used in the CCAT house, except with a chute adaptation to place the toilet seat in the upper bathroom. This design is the basis for the Sunfrost design with Toilet Chute, Rolling Dolly, and Crank Mixer. 12
  • 3.3.1.1 High Chair With the high chair model you would basically have a barrel that would hold the fecal matter and the user would climb up onto the barrel and sit down on the lid or toilet seat just like any other ordinary toilet and go to the bathroom on top the barrel which would then hold all of the bulking material and fecal matter beneath the actual toilet. Or in other words a toilet seat directly over a barrel. 3.3.1.2 Cork Screw Mixer The three-barrel system with corkscrew stirring is closely based on a system previously employed at the CCAT House. The toilet is located in the second floor restroom directly above the space that contains the barrel containment systems. One barrel at a time is connected to the toilet by a waste chute roughly ten inches in diameter. The chute passes through a hole in the lid of that barrel fitting tightly and sealed to be airtight. Each barrel is lined inside its vertical walls with a rigid metal screen that keeps the waste mass from touching the sides of the barrels and leaves a gap to allow airflow around the whole mass. Six inches above the base of the barrel is a circular grate and screen that keeps the solid waste above the floor of the barrel. This grate allows excess moisture to flow down out of the solid waste, preventing the mass from having a higher than desired moisture content. The space below the grate also allows for airflow. A simple manual crank pump has a down pipe reaching to the bottom of the barrel allowing the excess fluid to be pumped back onto the solid mass; usually after some dry carbon based matter such as saw dust has been added, allowing easy control of the moisture percentage in the mass. A narrow pipe enters the lid of the barrel and extends to the level of the bottom grate. Through this pipe fresh air flows into the container near the bottom so that it must pass through or around the waste mass to reach the exit vent which is out of the lid of the barrel. In each barrels exit vent is a low wattage fan to ensure airflow in the correct direction. Also in the lid of each barrel is a small hole, which allows for the passage of a thin steel rod with a corkscrew shape on the end that is used to mix up the waste mass to promote aeration throughout the mass. Each container will have one of these corkscrews so there is no need to pull the soiled rod into the open. 13
  • Figure 2: Diagram of the Sunfrost Design 3.3.1.3 Rolling Dolly The Rolling Dolly mixer design is a marriage between the Sunfrost and axial rotating design. The system works exactly like the Sunfrost design, but no stirring rod to aerate the composting pile will be used. The toilet seat in the bathroom fits over a chute that leads down into the 14
  • storage room. The chute is a straight plastic tube that stops 1 foot right above the 55 gallon barrel and attach to the lid with a chute extension that can be slid up and down to attach to the barrel lid. The lid is sealable and should stay on the barrel at all times of the composting process. The vent coming from the lid is detachable. Both the ventilation hole and chute opening can be closed so that no material can fall out while mixing. To mix and aerate the system, the rolling dolly will tilt the barrel at an angle of 30° to the floor and then the barrel can be manually spun. The lid will have to be detached from the vent and chute. The dolly has a large plate on the bottom and a track system with wheels on the side to allow the barrel to be spun once it is reclined. The dolly has a stand so that it is secured once it is reclined. The barrels are placed on a cart with wheels so that they can be easily moved and also rotate freely on the dolly. There will be three barrels; one receiving raw material and two being stored for composting. Each barrel is lined with a wire mesh on the inside to create a gap between the barrel wall and the material and allow air flow all around the pile. The air inlet will be a pipe that goes to the bottom of the barrel to increase airflow all around the pile. This air inlet pipe also doubles for the pump attachment to suck water from the bottom of the barrel. Each barrel needs to be mixed by using the dolly each week. The barrels go through a step every 3 months. The barrels first collect raw waste for 3 months then stored for 6 months in the storage room to allow for composting. Figure 3: Diagram of the Rolling Dolly Design 3.3.1.4 Crank Mixer The three-barrel system with corkscrew stirring is closely based on a system previously employed at the CCAT House. The toilet is located in the second floor restroom directly above the space where the barrel containment systems are located. One barrel at a time is connected to the toilet by a waste chute roughly ten inches in diameter. The chute passes through a hole in the 15
  • lid of that barrel fitting tightly and sealed to be air tight. Each barrel is lined inside its vertical walls with a rigid metal screen that keeps the waste mass from touching the sides of the barrels and leaves a gap to allow airflow around the whole mass. Six inches above the base of the barrel is a circular grate and screen that keeps the solid waste above the floor of the barrel. This grate allows excess moisture to flow down out of the solid waste, preventing the mass from having a higher than desired moisture content. The space below the grate also allows for airflow. A simple manual crank pump has a down pipe reaching to the bottom of the barrel allowing the excess fluid to be pumped back onto the solid mass; usually after some dry carbon based matter such as saw dust has been added. This allows for user control of the moisture percentage in the mass. A narrow pipe enters the lid of the barrel and extends to the level of the bottom grate. Through this pipe fresh air flows into the container near the bottom so that it must pass through or around the waste mass to reach the exit vent which is out of the lid of the barrel. In each barrels exit vent is a low wattage fan to ensure airflow in the correct direction. Sixteen inches above the grate is a shaft mounted the wall of the barrel and passing through the center to the other side where it passes through the barrel wall to connect to a hand crank. Mounted to the shaft is a circular steel member that will spin along the axis of the shaft, reaching down into the waste mass and stirring it up. This mechanism breaks up the mass and promotes aeration. In the lid of each barrel is a four inch square whole covered and sealed by a piece of fiberglass. These windows allow the user to see the level of waste and the progress of composting without needing to open the lids or expose the waste at all. Figure 4: Diagram of the Crank Mixer Design 3.3.2 Biolet In figure 3.2 is the design of a closed composting toilet system. Figure 3.2 is fairly advanced with a motor for stirring the compost and also a fan and heater installed to help aerate the compost to create the best humus. This is one of the standard Biolet systems the majority of these 16
  • systems will have a heater and a fan; some may have the electronic mixer where others may need to be manually mixed. Figure 5: Diagram of the Biolet Design 3.3.3 Axial Rotation This design has an outer shell that is solid and non porous. Inside the outer shell is a drum that on the top, bottom and the circular walls is made of a metal screen material that allows the flow of fluids and air in and out of the solid waste mass contained inside. On the side of the barrel is a door that opens to allow the incoming waste into the barrel. This door is designed to close when the barrel is to be rotated so that the mass does not spill out of the barrel into the outer container. Below the screen barrel is a space in the outer container to which any excess fluids in the waste mass flows. An air intake brings fresh air into the container and an exit vent containing an electric fan sustains airflow in the proper direction. The excess moisture in the bottom of the container evaporates preventing the solid waste mass from containing too much moisture for aerobic composting. 17
  • Figure 6: Diagram of the Axial Rotation Design 3.3.4. Composting Privy In figure 3.6 is the layout of a composting privy. A basic composting toilet in which you have a hole on top of a box or compartment in which the feces fall into the compartment along with the bulking material. It is in this compartment where the composing occurs with the breaking down of the feces into organic material. The compost will need to be attended to from an outside back door where you will be able to aerate and remove the compost when necessary. 18
  • Figure 7: Diagram of the Composting Privy Design 3.3.5 Anaerobic Digester This system uses a 55-gallon drum as the storage tank and digester. The drum is placed outside for safety and odor purposes. Inside the bathroom there is a wood box with a toilet seat on top. Inside the box there is a five gallon bucket to collect the human waste. This bucket is then taken outside and dumped into the digester. The lid of the digester is completely sealed but has a hatch that can be opened to allow adding more waste material (feces, toilet paper, and urine) into the digester. The lid of the digester is dome shaped, with a gas valve at the top. The biogas that is produced from the anaerobic process inside the digester is lighter than air and collects at the top 19
  • of the dome. The gas valve is connected to a hose or pipe that passes the gas through a medium bucket. The gas is bubbled through water and collected at the top where another pipe connects to a storage container. The storage container is a deflated large inner tube. After the barrel has been sitting without any raw material added for 6 months the decomposing process will be done and there will no longer be an odor. The sludge can then be dumped out into a separate compost pile and composted to insure pathogen destruction. There are three separate barrel systems in use. Each barrel is coated with an erosion resistant paint, inside and out. No mixing is necessary for raw material and there should be enough water in the barrel to make the material into sludge. Figure 8: Diagram of the Anaerobic Digester Design 4. Decision Phase 4.1 Introduction In the decision phase the alternative solutions are judged based on the criteria to find the best solution for the project. We used the Delphi method in order to quantify our opinions for each alternative solution, and narrowed our solutions down to two designs. These two designs were then discussed with the residents of CCAT to come to our final solution. 4.2 Criteria Definitions In order that we as a team and any observers understand what each criterion means and how it should be weighted toward our decision we have defined them in this section. These criteria are the same as we determined in Section II to be applicable to our project solutions. 20
  • Composting Effectiveness: How well the system turns raw organic waste into an effective and usable composting soil. Safety: How much the system exposes users and staff to raw material that is potentially harmful. The maintenance of the system should not require hazardous work. Odor: How much the system releases odorous gases into the living or work space at CCAT. This incorporates how well the system is vented and sealed and how well the composting process is maintained. Cost: The cost includes all initial costs to build and set up the system and maintain the system. Difficulty of Management: Minimal effort to maintain and empty the system and also considers how frequently the work will need to be done. Work includes aerating the compost pile and removing finished compost from the system. Grossness of Management: The up keep of the system should not be unpleasant. Minimal to no exposure to waste matter is required to keep the system in proper working order. Positive Presentation: How well the system shows a composting toilet as an appropriate technology. The system should have the appearance of being easy to use to encourage the use of a composting toilet at other locations. Ease of Construction: How many hours of construction the system will require and that construction can be accomplished with the skills available to Team Universe. Resource Appropriateness: The resources used for the system match with the CCAT mission of using local and reused or recycled materials. 4.3 Solutions These are the solutions that we will be judging. For a more details on each design refer back to Section 3.  Sunfrost  Sunfrost design with toilet chute  Rolling dolly  Crank mixer  Biolet  Axial rotation  Composting privy  Anarobic digester 21
  • 4.4 Decision Process The process we used to arrive at our solution was the Delphi method. We first determined a weight value for each of the criteria as a group. The values ranged from zero to ten with zero being no concern to ten being of critical concern to the final solution. Next we assigned a value for how well each design fulfilled the individual criteria. Zero meaning the design did not address the criteria and fifty meaning the design had outstanding design features for that criterion. When we disagreed we would debate the pros and cons and come to an agreement about the scores. Then each score was multiplied by the criteria weight, and all weighted scores were added up for each design. From these totals we could see how each design ranked in comparison to the other designs. Refer to Table 5 to see the weight for each criteria and the ranking of each design. Table 5: Delphi Method Chart Criteria Weight Sunfrost Sunfrost Crank Rolling Axial Anerobic Schute no Schute Dolley Rotation Digestion Composting Effectiveness 10 45 450 45 450 43 430 35 350 45 450 10 100 Safety 10 40 400 42 420 45 450 30 300 45 450 20 200 Odor 10 38 380 40 400 42 420 35 350 42 420 25 250 Cost 8 40 320 45 360 32 256 30 240 15 120 10 80 Difficulty of management 7 32 224 35 245 40 280 28 196 38 266 30 210 Grossness of management 7 32 224 35 245 40 280 32 224 40 280 30 210 Positive presentation 7 40 280 35 245 40 280 35 245 40 280 40 280 Ease of Construction 6 35 210 42 252 30 180 30 180 10 60 10 60 Resource appropriateness 6 40 240 42 252 38 228 35 210 30 180 30 180 Total: 2728 2869 2804 2295 2506 1570 The Delphi method chart in Table 5 shows the weight of each criterion and the scores for the designs in regards to these criteria. From the Delphi method, we narrowed out solutions down to two designs; the Sun Frost design and the Sun Frost with Toilet Chute design. We discussed the pros and cons for each of these two designs with the CCAT residents. The CCAT residents voiced opinion that they would prefer the Sun Frost design based on concerns for the cleaning of the toilet chute in the other design. 22
  • 4.5 Final Decision Justification Our decision for the final solution is the Sun Frost design. We came to this decision from narrowing down our solutions using the Delphi method and discussing the remaining solutions with the CCAT residents. The Sun Frost design was in fact the solution alternative with the highest score using the Delphi method. There are positives to the Sun Frost with Toilet Chute Design that were appealing and made it a strong option. However, there were also significant concerns for the toilet Chute design that were highly weighted both by our team and the clients. Amongst our team members and CCAT we came to a consensus that the Sun Frost design was the best suited for our situation. 5. Specification of Solution 5.1 Introduction Section 5 of the design document has a description of all the aspects of the final solution, which was selected in Section 4. A detailed description of the Sunfrost Composting toilet that Team Universe will construct including: ventilation, barrel, and step box layouts. Along with a list of costs, this will include: the implemental costs, maintenance costs, and construction time. Section 5 will conclude with implemental instructions to help the user of the system with proper practices to use the composting toilet. 5.2 Solution Description The Solution Description will cover 4 sub-sections including: the waste containers, barrel lids, ventilation, and the step box. Which all have brief descriptions and along with some user instructions as a part of our solution in the following sections. 5.2.1 The Waste Containers The human excrement composting system to be placed in the CCAT house will utilize three 55- gallon steel barrels as the waste containers. Each barrel will be filled with a drum liner, made of thick, durable plastic sheeting, formed specifically to fit inside the barrels used. The plastic liner forms neatly to the inner walls of the barrel and covers the bottom, as seen in Figure 9. By keeping the waste away from the steel walls, the liners eliminate concern of corrosion and promote easy cleaning after the removal of finished compost. Around the outside of each barrel is an insulation jacket, as can be seen in Figure10. This insulation keeps heat generated by microorganisms in the compost mass inside the barrel. Each of the three barrels is fixed to a round wooden base, which has five evenly spaced steel castors to allow for easy moving over smooth surfaces. Located at the bottom of each barrel is steel grate upon which is a fine steel mesh is attached. The grate and mesh together prevent solid waste from reaching the bottom of the barrel and create a cavity, in which excess fluid in the mass can escape, and which allows for airflow towards the bottom of the mass. The grate is held 2.5 inches above the floor of the barrel by four pieces of three-inch PVC pipe. In each barrel there is a two-inch PVC pipe, shown in 23
  • Figures 9 and 10, which extends one inch above the lid, down through the steel grate to a point just one inch above the floor of the barrel. Each pipe is held in place by the hole in the grate and the hole in the lid that it fits through. The function of this pipe is to allow the down pipe of the hand crank pump to reach the fluid at the bottom of the barrel without contacting the solid waste. Also in each barrel is a steel hand mixer with corkscrew tip, shown in Figure 9, used to stir the compost mass. Figure 9: Inside view of Barrel Figure 10: Outside view of Barrel 24
  • 5.2.2 Barrel Lids In each stage the barrel has a specific barrel lid. Upon each barrel container is a laminated wooden lid that performs multiple functions. The lids are covered on each face by laminate for ease of cleaning and to keep the wood from absorbing moisture. The edge of each lid is heavily painted for the same purposes. Just one lid has a hole and toilet seat for use on the barrel currently receiving waste. This lid, shown in Figure 11, will remain located in the bathroom upon the barrel in use. The toilet seat is placed in a location selected for comfort and ease of use. A hole in the lid under the seat is cut larger than the inner size of the seat to minimize the risk of soiling the lid during use. Connected to the same hole is a one-half inch diameter strip, shown in Figure 11, cut five inches long away from the whole to allow the stir rod to be kept in the barrel and allow it to be used in the large entrance hole. In the other two lids there is also a large hole, Figure 12, which allows for the use of the stir rod. Each of these holes is covered by a fitted piece of Plexiglas to minimize any odor escaping. There is also a notch in each of these Plexiglas pieces to allow the stir rod to stay in place. All three barrels have two holes for use by the hand crank as seen in Figures 11 and 12. To the bottom of all three barrel lids is fixed a four- inch duct fan, Figure 12, above which is a four-inch hole cut in the lid to allow air flow out of the barrel. The hole above the fan is cut to allow the four inch PVC pipe fixed to each duct hose to fit tightly in place and create a quick disconnect for the vent system, as seen in Figure 12. Figure 11: Stage One Lid 25
  • Figure 12: Stage Two and Three Lid 5.2.3 Ventilation The ventilation for our system is composed of flexible PVC tarpaulin canvas, which is a lightweight, highly flexible duct that will improve the efficiency of ventilation. The ventilation tubing has been installed in: the downstairs bathroom, about 18 feet; the downstairs storage room, about 40 feet. There was also a pre-existing metal duct which travels from downstairs to the roof of the top story. For the ventilation in the storage room we had to connect two barrels ventilation tubing, using a “Y connector” that was placed in the sub ceiling the two ventilation tubing was joined, to create one tube, that would then connect and exit the basement through the metal vent duct. Connecting the ventilation tubing to the three-inch PVC “Y connector” are zip ties, which create and air tight seal without damaging the ventilation canvas tubing. The layout for the ventilation system can be seen in Figure 13. Figure 13: System Layout 26
  • 5.2.4 Step Box The step box is constructed so that a person can easily step up and sit on the toilet seat. Refer to Figure 10 in Section 5.2.1 for box design and dimensions. The box is constructed with wood and screws. The sides of the box are 3/4 inch plywood cut outs. The step and platform are made from 3/4 inch think particle board with a lament covering the top. A cargo strap is attached to the back so that the toilet drum can be secured to the box. Rubber pads are placed on the bottom to prevent unwanted sliding on the ground. 5.3 Cost Analysis The costs that went into the design and implementation of the composting toilet solution are versatile. There were many man-hours put into the research and design necessary to select an appropriate system for the given situation. More person-hours as well as physical resources were necessary to construct and prepare the system for use by the client. Many of the physical resources did not require purchase while others did. The real or potential cost of each of these materials is shown in this section. The maintenance of the system will also require time and monetary resources over the projected period of its use. 5.3.1 Design Costs The costs of the design for this system are represented by the input of time by the three team members involved. This chart, Figure 14, shows the total hours of input as well as the hours used to fulfill each phase of the design process. Figure 14: Project Hours Pie Chart 27
  • 5.3.2 Construction Cost The construction of the composting toilet system required numerous materials. A portion of the materials were made available by the client, some were donated to the team, and the remaining materials were purchased. The following table shows all the materials used to construct and implement the system. For purchased items the price paid is shown in the chart. For donated items an estimated cost is shown so a total estimated cost of the system is shown. Table 6: Materials Cost Our Market Cost Materials Cost($) ($) 70ft. Ventilation Hose 48.30 48.30 3 Cork Screws 20.00 60.00 3 AC Fans 40.00 40.00 3 Plastic Barrel Inserts 24.00 24.00 3 Insulation Jackets 45.00 45.00 Toilet Seat 15.00 15.00 3 55-Gallon Drums 0.00 156.00 Pump 0.00 45.58 15 Casters 0.00 75.00 3 Grates 0.00 59.96 3 Wooden Bases 0.00 30.00 Wire Mesh 0.00 10.00 Wood Frame 0.00 40.00 10ft. 2 1/2" PVC Pipe 0.00 6.49 3" PVC "T" Connector 0.50 0.50 1ft. 4" PVP Pipe 0.00 1.39 52 Screws 8.28 8.28 1 Bag Zip Ties 7.00 7.00 Total: 208.08 672.50 5.3.3 Maintenance Cost The system is designed for three users to withstand at least five years and contains a few fragile parts. We predict that the ventilation system will be the most likely to require maintenance, on account that the material is very fragile plastic canvas. Another frail part of the system would be the mesh screens that keep the solid mass from the liquids; they are reused and may need to be replaced. Maintenance costs should not exceed $40.00 a year and only in the event ripping in the ventilation or corrosion of the mesh screens. 28
  • Table 7: Maintenance Cost Maintanence tasks Time Projected Frequency Cleaning /Emptying Barrels 1 hour per 4 months Rotating Container Positions 15 minutes per 4 months Adding Bulking Materials 1 minute per day Stirring/Pumping 25 minutes per week Ventilation check 30 minutes per year Ventilation Maintanence (possible damages only if necessary) 1 hour per year Screen Maintanence (damages only if necessary) 1 hour per year TOTAL: 34 hrs. per year Table 8: Usage Costs Projected Usage Money ($) Projected Frequency Bulking Material 0.00 per week Electricity use NA per month vetilation replacement 20.00 every 5 years grate/screen replacement 30.00 every 3 years plastic insert replacement 8.00 every 3 years fan replacement 20.00 every 3 years 5.4 Implementation Instructions 5.4.1 Overview The composting toilet is divided into three stages, refer back to Figure_ in section 5.2.3. The first stage is receiving fresh waste and is located in the bathroom. The second stage is composting with no fresh material being added and is located in the storage room. The third stage is continuing to compost and is also located in the storage room. After four months the barrels will rotate to the next stage with the third stage barrel being emptied and cleaned, and then put in the bathroom to receive fresh waste. 5.4.2 Barrel setup Each 55-gallon drum contains a plastic barrel liner, a barbeque grate covered with a wire mesh, an insulating cover around the outside of the barrel, a pump sleeve pipe, a stir rod, a barrel lid which contains a vent fan and vent connection, and the whole barrel is set on a rolling cart. Insure that all components are present and in correct placement. Refer to Section 5.2.1 for barrel description and set up. 29
  • 5.4.3 Stage One Stage one is located in the bathroom and is the waste receptacle. The barrel placed in the cut out of the box and strapped to the box so that the barrel will not move while in use. The lid with the toilet seat should remain at stage one. Before use of the system the barrel should be filled with six inches of wood shavings. And after every use more shavings should be added to cover the feces, about half a liters worth. The contents of the barrel should be stirred with the stirring rod at least once a week and the pump should be used to suck the liquid from the bottom of the barrel to the top of the composting pile. After around an estimated four months the barrel will be rotated to stage two; however, no new raw waste should be added if the barrel is more than three quarters full. 5.4.4 Stage Two Stage two is located in the storage room where the waste will be composting. The barrel should be placed under the vent closest to the wall adjacent to the bathroom. The lid should be put on the barrel and the vent connected. The fan should be plugged in and running. No new raw waste should be added. Wood shavings can be added if necessary for the composting process. The compost pile should be stirred once a week. The pump may also need to be taken from the barrel in the bathroom, placed in the sleeve pipe, and used to pump the liquids from the bottom of the barrel. If there is no liquid in the barrel then the pump is not necessary. After approximately four months the barrel will be rotated to stage three. 5.4.5 Stage Three Stage three is also located in the storage room. In this stage the compost will continue to break down. The barrel should be moved over from stage two and placed under the vent closest to the exterior wall. Follow the same directions as stage two for pumping and stirring. 5.4.6 Emptying and Cleaning After stage three the material will be ready to be used as compost. The vent should be removed and the barrel should be rolled outside to the dumping location. Remove the stir rod and dump the barrel over. Use a shovel to empty the barrel if necessary, but caution should be used so as to not rip or tear the plastic liner. Remove as much compost as possible. The metal screen and the inside of the barrel should be hosed off. 5.5 Prototype Performance The composting toilet was completed on December 9th, 2009 and is in place at the CCAT house on campus. This system performance cannot be evaluated at this point; however a similar Sun Frost design is working at the Arcata Educational Farm. 30
  • 6. Appendices Appendix A – Brainstorming Notes 31
  • Brainstorming Notes (Continued) 32
  • Brainstorming Notes (Continued) 33
  • Brainstorming Notes (Continued) 34
  • Brainstorming Notes (Continued) 35
  • Brainstorming Notes (Continued) 36
  • Appendix B - References Anonymous, (2004). Sun Frost “Human Humus Machine” Composting Toilet, < http://www.sunfrost.com/composting_toilets.html>, (Sep. 28, 2009) Anonymous, (1993, 2009). Compost Quality: Performance Requirement Characteristics, http://www.ciwmb.ca.gov/organics/products/Quality/PerfChar.htm, (Sep. 24,2009) Anonymous, (2005) Humboldt County, California: Climate. http://co.humboldt.ca.us/portal/about.asp (Oct. 1, 2009) Beckman, C. (2008). “Category:Composting toilets.” Appropedia, <http://www.appropedia.org/Category:Composting_toilets> (Sept. 23, 2009). Haskett, Tobey. Personal Interview. Oct. 7, 2009. Henry, C., Olsen, E., Fioravanti, M. (2009). “Improving Sanitation with Composting Toilets,” Biocycle v. 50 no. 2, 42-3 Jenkins, J. (2005) “The Humanure Handbook” a guide to composting human manure. Joseph Jenkins Inc.; Grove City, PA. 103-105. Kaiser, Josephine, 2006. An Analysis of the Use of Desiccant As a Method of Pathogen Removal In Compost Latrines in Rural Panama. http://www.cee.mtu.edu./sustainable engineering/resources/reports/J_Kaiser_Masters_Report_FINAL.pdf Nov. 3, 2009. Leary, M. (2007) Comprehensive Compost Odor Response Project. San Diego State University, San Diego CA. Maurer, M., Schwegler, P., Larsen, T.A. 2003 Nutrients in Urine: energetic aspects of removal and recovery http://iwaponline.com/wst/04801/0037/048010037.pdf Nov. 2, 2009. Minnis, Peggy, Dr. 2005. Sources of Nutrients in Wastewater. www.ces.ncsu.edu/plymouth/septic3/MinnisNutrientsText.pdf Nov. 3, 2009 Obeng, L. A., and Wright, F. W. (1987) The Co-composting of Domestic Solid and Human Wastes. The World Bank, Washington DC. Pescod, M. B. and Price, A. C. (1982). “Major Factors in Sewer Ventilation.” Water Pollution Control Federation, V. 54, N. 4 (Apr., 1982), 385-397 Renfer, Dean. Personal Interview. Sept. 30, 2009. Stoner, C. H. (1977) Goodbye to the Flush Toilet. Rodale Press, Emmaus, PA. Tinseth, Phred (2002). Composting Toilets, http://www.phrannie.org/compost.html , (Sep. 29,2009) 37
  • Unknown, C 1996-2009. Oikos Green Building Source. What is Composting? http://www.oikos.com/library/copostingtoilet/composting.html . Nov. 2, 2009. Van der Ryn, S. (1978) The Toilet Papers. Capra Press; Santa Barbra, CA. 38