"The purpose of life, the reason to exist, from birth to death, is to learn. We are here to learn of God's truth in His creation. We are here to learn to live in peace and in harmony with all of God's creation. What better way to know God than to look for His truth in His created universe. Clearly and beyond all doubt, the only purpose and reason for life is to learn. All living beings, plant or animal, that ever was, is, or ever will be throughout the universe must learn to adapt within the universe or perish as with the dinosaur. Yet it is the fate of humanity, above all, to have the consciousness to understand and give reason to life's purpose."
Thoughts by Charles H. Tankersley
Bio-Digestion is nature's means of recycling of all plant and animal wastes. All life has a beginning and an end; new life is old life recycled. New stars are born of old stars, a process which has continued since God created the universe over 14.5 billion years ago. Within the birth and death of the stars, certain elements are created, Oxygen, Carbon, Nitrogen, and more. It is the Carbon, combined with the primary element Hydrogen,the fuel of the stars, Oxygen, Nitrogen, and traces of other elements, mixed with water, that gives rise to life. Life is, then, can be called a recycling of a portion of God's Universe. Thus, with God's wisdom at work, thus is the evolution through God's recycling of His creation, with the ultimate result of God's wisdom making "the fate of humanity, above all, to have the consciousness to understand and give reason to life.".
Of all life, recycling is common place and accepted by all except humanity. Although birth and death are inevitable, the Human being, the pentacle of God's creation, is the only life which searches for immortality, the fountain of youth. The human being is the only form of life that will fight God's recycling plan. Thus, mankind is by far, the most wasteful of all God's creation. This lesson plan is the first of a series of lesson plans to reverse man's wastefulness. This is intended to be a hands-on tutorial for using God's recycling plans to improve the living condition of man and all life. This is a plan to work with God and Nature rather than against God and Nature. We are the stewards of Earth, it is up to us to give this little rock the loving care God intended. Let us recycle.
For those of us that live in a rural environment, small community or farming community, regardless of how poor or rich it may be, know the value of composting and the value of spreading manure on the Fields. We all know to put back to the soil that which we took. Thus, corn stocks and wheat shafts are plowed back into the soil so that our corn and wheat of tomorrow might grow tall and strong. This is the knowledge of our forefathers and we must respect those who have come before us. It is our heritage that we must respect the earth so that our children may respect us. Those of us who band together in large urban areas, however, do not know to recycle. We dump our waste in landfills, flush our wastes down a sewer, bury and hide our waste. Out of sight is out of mind. What we do not realize is that our waste, all of it, contains enough energy to lift us out of poverty and into a comfortable prosperity. This is the first of a series of hands on tutorials. When this series of tutorials is completed, the student will have built, with his own hands, an energy gathering system to supply the needs of his household and, perhaps, his community.
Below are a series of readings from various sources. It is most important that we all have a thorough knowledge of the terms and concepts of bio-digestion. Each reading will instill its own specific terms and concepts. As you look though the list, each item will indicate these terms and concepts which you will need to come to understand as you study each of the readings. It is recommended that the student express his understanding of these terms and concepts following each reading:
You will find important words in these articles used often in the text below, so keep the articles close at hand so you can find and understand what is being discussed.To begin with, in all engineering design, it is important to understand that safety is the most important factor to consider. Safety is related to and followed closely by reliability, then simplicity and finally by cost and aesthetic value. Thus, with safety in mind, we will build the most reliable, simple, inexpensive, and prettiest digester ever conceived. As you can see from the readings, a bio-digester is little more than a simple sceptic tank. The first reading suggested in the Table of Content above has a number of cross section pictures of septic tanks. The septic tank is, in fact a bio-digester and we will use them as the outline of our home made bio-digester but with a few exceptions to the placement of the tank, the materials used to build it, and how we collect and use the "stuff" that goes into the tank and what comes out of the tank.
The septic tank pictures show us nothing more than a water and air tight box. The picture suggests that it is made of concrete and this is true much of the time. We can make a bio-digester of concrete, however, there are many things that we can use, too. If we have enough money, we can even purchase ready made septic tanks made of plastic or steel. But let us choose the materials that are the least expensive, easy to find where we live, and that we can use ourselves. To fit our needs, take your pick of wood with a plastic our waterproof lining, concrete, clay, or fiberglass. The least expensive that is available almost anywhere on earth is clay. Then comes plastic lined or waterproofed wood followed by concrete and then fiberglass. Each of these materials have their own advantages and disadvantages and one might consider a combination of two or more. For example, the base unit might be of clay or concrete and the gas trap unit of wood, fiberglass, or plastic. You, as a group, will need to discuss among yourselves which material you can best use for your bio digester.
It would be best to start with the most simple and easiest to build design. Let us design two boxes, one 400cm inside length (~ 160") by 100cm inside wide (~40") and 150cm tall (60"). The first box will be called the Base. The other; 399cm outside length (~ 159.5") by 99cm outside wide (39.5") and 127cm high (50"). The smaller box is to be able to fit up side down easily inside the larger box to rest on a ledge about 30cm from the bottom of the base unit, about 20cm below the top of the base unit, and with equal space remaining open at all sides. The second box will be called the gas trap. Note that this gives us approximately six cubic meters which is equivalent to about 5680 liters or 1500(US)gal. An all plastic septic tank of this capacity can be purchased in the USA for about $1,500. for our shape, let us look at the pictured on "Alternative Septic System Designs" and the pictured Septic systems Link:
All three of these designs shown in the pictures above approximate what we plan to build but there will be some differences in each of the cross sections. The major difference will be we will actually be building two boxes, one that will fit up side down inside the other. In addition, it would be good if we built a small model of this at one tenth or one twelfth scale. This can be made of stiff cardboard or balsa wood, One can also build a "Working Model" at about one Fourth scale using wood. The model can be made of wood, plastic, fiberglass, clay, plaster or concrete. If it is to be a "working model", it might be good to make the base of concrete and the gas trap of wood or fiberglass. This would make the working model capable of actually digesting some organic input and producing gas and might be useful for individual homes to digest bath bathroom, pet, and kitchen wastes. The scale can also be increased for industrial use but the 6 cubic meter design above is an ideal module size in most cases. For industrial uses, it would be better to make several of the modules rather than one very big unit. This would facilitate upkeep, repairs, cleaning, and maintenance problems which might arise. (See the septic tank reading above for maintenance problems.)
Now is the time to take out pencil, a good eraser, and paper. We are going to make a design sketch. The term sketch means that the accuracy of the picture only approximates. It is the dimensions applied that count. Notebook paper will do, however a sheet of mechanical drawing paper 280 mm (11") x 430 mm (17") would work better. You will likely need several sheets of paper. You will also need a scaled rule, either in metric units or English units, and some sort of a smooth flat surface to work upon such as a desk or drawing table. As you work, if you have any difficulties with making your design drawing, it will be a mistake only if you fail to ask for help. Failure in not the lack of knowledge, rather, failure is not seeking help to gain the knowledge. A little insight for students is to know that to be a teacher or a supervisor does not mean you know it all. It means, instead, your have learned where to look to find the answers you need. It is stupidity to not seeking help as it when it is needed. Don't guess, ask!
You may pin or tape your paper down to your drawing surface. Since this is a sketch rather than a formal drawing, it will be OK if the lines are not exactly straight and/or parallel, simply be as close as you can be. After all, it is the dimensions that will count. The picture is just an approximate a guide. In the very top, left corner, write "BIO DIGESTER UNIT 1"followed with "by your name and the day's date". Put this on each sheet of paper you plan to use, but numbering each sheet as 1 of 5, 2 of 5, 3 of 5, etc.
Label sheet 1 of 5 "Base Unit". Look at the paper you are working on and visually locate the center of the upper half and put a dot on that spot. This dot will be your working reference point. With your rule, measure 76mm (3") from the left and right of the dot for a total of 152mm (6") and make a dot at each end of the long line. From the left hand dot, draw a vertical line downward 19mm (3/4")and upward 19mm (3/4"). Do the same on the right hand side. Now draw a line from the top of the left line to the top of the right line, and from the bottom of the left line to the bottom of the right line. This becomes the outline of the Plan View of the Base Unit. Now, find the center of the bottom half you your paper and place the dot. Following same procedure as for the Plan View, make the vertical lines at each end 28mm (1 1/8") up and 28mm (1 1/8")down. Once you have completed the bottom box, this will be the outline of the Elevation View of the Base Unit.
(A special note for those of you who are using the English system of measure, from this point on, all dimensions will be given in the metric system. You will need to learn to convert from metric to English system if you want to continue to use the old fashion and out dated feet and inches. For you conversion, the factor is 25.4mm equals 1 inch. Perhaps you need to have your instructor help you to learn the metric system. The student who has Internet access can find numerous conversion charts on-line by typing into Google, "metric conversion". A good one would be http://www.sciencemadesimple.net/conversions.html but the student can pick his favorite. Be careful, however, some do charge money for the service; avoid any which ask money to use or buy. The metric system is used throughout the world except in the United States and is used by scientist and many engineers in the USA.)
The plan and elevation views which you have drawn also delineate the inside limits of the Base Unit box. There can be no protrusions into this space so as to not interfere with the setting of the Gas Trap Unit inside of the Base Unit. Once the top of the gas trap unit is set flush with the water line as set by the outlet, four blocks should be set near the corners of the base unit heavy enough not to float of be easily moved, high enough and large enough to become a "stop" to hold the base of the gas trap unit at its proper level. A brick or concrete block of the proper size will work for this purpose. At this point, you will need to make the box outline into "Object" lines, that is to make them heavy. Finish this work by extending dimension lines to the top and right side of both the plan and elevation views. Apply the dimensions required. The next step is to draw the inlet and outlet for the base unit. We will make the left side the inlet side. It is this pint, it is important to note that the inlet penetrates into the base unit at a point below the gas trap unit. The top of the inlet may be flush with the bottom of the gas trap unit and should be above the very bottom of the base unit. However, one can have several inlets anywhere along the inlet end as space allows. Note too, that the outlet, as with the inlet, may be anywhere along the outlet end of the base unit but the bottom of the outlet must be above the top of the gas trap unit. This is so that when operation begins, all the air within the gas trap unit is evacuated. As the bacteria in the digester does its job, an approximate 50%-50% mixture of carbon dioxide and methane is produced. When the methane is mixed with the air, it becomes an explosive even though it is mixed with carbon dioxide. Thus, for safety's sake, the gas trap needs to have all the air removed before the methane mixture is collected.
Look to the three pictures of septic tanks above. In the middle picture, one sees an inlet pipe and a baffle to separate the inlet pipe from the larger digester chamber. In our case, we can do one of two things, we can add a small chamber for the inlet similar to the picture but with a removable cover over the chamber. Or we can make the inlet pipe turn down to below the level of the gas trap unit and then extend inside the gas trap unit. The latter scheme will allow any discharge to be forced inside the gas trap unit before digestion begins. With the first scheme the pipe discharges into the separate inlet chamber where some digestion begins before entering the gas trap chamber and will be lost through the cover and into the atmosphere. This loss come be minimized if one were to use a paddle to force the discharge down and into the confines of the gas trap unit. There is a third design which is a combination of the two and is recommended to be used here. We will make our sewer line from the homes and from our animal shelters to be 10cm concrete, clay, plastic or metal pipe. This pipe will need a "trap" at the beginning to keep the gases and odor from flowing back into the home or barnyard. As the pipe is laid in the ground, it must be set above the water level of the bio-digester such that the flow is always downhill. This means that the bio-digester is always downhill from any lodging, human or animal, and always downhill and way from any drinking and cooking water source, human or animal. Sanitation is a must to help prevent diseases. When the sewer pipe reached the bio-digester, it will connect to a "Tee" above the water line of the bio-digester. From the tee upward we will connect a short pipe with a threaded cap on the end which can be removed, This will be a point for cleaning and for inserting finely chopped organic materials such as leaves, grass clippings, etc., to be pushed down into the gas trap unit of the bio-digester. Connected to the bottom of the tee will be a pipe with a "90 degree Elbow" and piece of pipe long enough for the open end to be about 10cm to 15cm inside the gas trap unit's inlet limit. It is conceivable that one can put several of the inlet piping systems into one bio-digester unit, however, for maximum gas output, the residual time for the organic material inside the digester should be in access of 10 days and no longer than 30 days. to accomplish this residual time in the digester, no more than three sewer pipe systems should be installed into any one digester. If more than two sewer piping systems are required, then additional bio-digester modules should be considered.
The outlet end of the base unit controls the water level. The idea here open a space about 10cm deep from the top of the base unit and about 20 cm wide. from this opening a trough is made to funnel down to a 15cm pipe which will be the entrance to the piping to a "settling pond" or to an absorption field as described in the septic system in the readings above. With the water level set and the inlet level set, we can now set the top of the gas trap flush with the water level. At this point, it becomes clear that the bio-digest must be set level or with a very slight slope down from the inlet end to the outlet end. Also, at this point, we might want to consider some sort of a short, flexible pipe between the sewer collection system and the inlet piping of the Bio-digester. The outlet end pipe should also have a short, flexible pipe or tubing to the effluent distribution system. The flexible pipes or tubing will allow for any thermal expansion and for any slight misalignment of the piping. In all cases, however, the flow should always be downhill.
Label sheet 2 of 5 "Gas Trap Unit". As you did with sheet one, divide the paper in half and find the center of the two halves. The top half will be the plan and the lower half will be the elevation, just as it was with the base unit. The gas trap unit is far more simple than is the base unit. This upside down box is to fit easily into the base unit with at least one cm and not more than 1.5cm space on all sides around from the base unit. This is to allow the access water to escape and flow to the outlet of the base unit. All structural support and bracing must be on the inside of the gas trap unit and outside the box of the base unit so that there is no interference with the vertical movement of the gas trap unit as gas builds up inside the box. The gases will cause the box to rise up to the top of the water level before it can escape. This is an automatic safety valve should too much gas is produced and not used. Remember, safety is the first consideration to our design. Usually, the gas will be used prior to the gas trap over filling. Another reason for the floating gas trap is that the weight of the gas trap will slightly compress the collected gases and make it easy to transfer to the home heater burners, to the kitchen stove, or to the engine driven generator. Of course, when they become available, sulfur removal units, carbon dioxide units, and water removal units will be placed between the Bio-Digester and the end use, furnace, cook stove, or generator. However, the gas produced by the bio-digester is about 50% methane, 50% carbon dioxide with trace amounts of sulfur dioxide, water vapor, alcohol, and other gases.
At this point look at the dimensions for the inside of the base unit and with the parameters given for the spacing, add your dimensions to the gas trap unit. To finish off your gas trap, we need some way to transfer the gas to where it is to be used. What we will do is to find the center of the top of the gas trap and add enough material such that we might attach a valve with a standard garden hose male connection. If one has the proper plumbing tools and material, then, by all means replace the garden hose and its connections. The garden hose is a stop gap measure and must be carefully and regularly checked for leaks and damage. However, at least a section of the gas piping must be flexible to allow for the upward movement of the gas trap and for than thermal expansion which might occur. The attachment to the gas trap will need to be firm enough so as to not pull loose or leak as one maneuvers a garden hose about. Also, when one is first submerging the gas trap into the water filled base unit, the valve will be open to allow air to escape. Once all the air is forced out, the valve is closed and remains closed until such time as the production gasses lift the gas trap about half way out of the base unit. If you feel you need more details of any part of the Bio-Digester, be sure to use the remaining three sheets. Also, put all notes and important calculations on these remaining sheets of paper as directed by your instructor. You instructor will examine your design for errors and tell you win your design is ready for you to begin building the digester. Remember
Location is a very important chore. Always refer to the septic tank system in the reading material and treat both the inlet and outlet to the bio-digester the same as if it were a septic system, which it actually is. Where the bio-digester is located can have a major effect on the health and well being of any community. It is important to know from where the drinking, cooking, bathing and animal water is received. Look for a location that is downhill from water wells, reservoirs, lodgings for both people and animals. It would be wise to be downwind of human activity, too, so that the smell would not be a nuisances. The best location for our system would be near but uphill from a dry gully or creek that has water in it only during the rainy season and drains away from any human of animal habitat. Also, the system should be far enough uphill form the creek bottom to allow for an absorption field as described in the reading at the beginning of this tutorial. Sandy, rocky, loamy soil that allows percolation or absorption into the soil is the best. However, if it is decided to build a settling bond, this should be just after the bio-digester's discharge. A settling pond would also be a good place to deposit scum and sludge if not dried for use as fertilizer on the fields. The settling pond could be of a benefit by allowing Aerobic digestion to kill any remaining harmful bacteria. One needs to keep domestic animals and playing children away for the settling pond. The overflow from the settling pond can then be placed into the laterals to the absorption filed. Remember, the best material for the base unit is concrete follow closely by clay. In either case, the base unit becomes permanent, thus, if a location mistake is make, the base unit would have to be re-built in a new location. The old base unit would have to be buried or demolished. One last thing, think of your neighbors who might live downstream from you. Be a good neighbor.
Now that we have a design we can take the first steps toward building our digester. For this tutorial, the first construction will be a pilot model approximately one quarter scale. This model will be build entirely of treated plywood and lumber with the exception of the piping. The second construction will be to the full scale as designed. However, if one wishes, the scale can be adjusted to double size of even more. Just remember that as one increases the scale beyond the design, the more difficult it becomes to handle the gas trap part of the digester for maintenance and clean-out.
The first construction step is location as was discussed above. But after location and before we can build, we need to locate and gather the materials to build the digester. What we need for this it to look at our plan and list everything needed to put together our digester, including any special tools unique to and needed for construction. This will be called a "Bill of Materials". As we make our "Bill of Materials", we will need to list the location of the materials's source and the cost of the materials. The first "Bill of Materials" in this tutorial will be for the quarter scale pilot model, followed by the designed scale. For the full full design scale, the Bill of Material will assume a concrete base unit with ready made plastic piping and a treated plywood and lumber gas trap unit. One may replace the concrete with a dense clay or with ceramic tile set in dense clay or mortar. The primary concern with the base unit is to make it permanently water tight and strong enough to withstand the riggers of maintenance and clean-out which can include several persons standing on the bottom with shovels and cleaning equipment. And finally, Be sure to keep SAFETY first and foremost in your minds, both during construction and during the operation and maintenance for the finished product.
(Special note: The principle author of this tutorial plans to actually build the Pilot model and at a later date may build the design scale model of the bio-digester if time and funding permit.. The author, Charles H. Tankersley lives in Houston, Texas, and since the materials of construction must be purchased in Houston, Texas, English units are necessary for the Bill of Materials. For those who are in nations which the materials are available in Metric units, then please us metric units when you create your bill of materials. For this tutorial, the Bill of Materials are to be used as an example, only. The student needs to copy the form of the Bill of Materials and insert his own materials using his own units of measurements and costs. This becomes very important to those who live in areas of poverty, cost become critical to the poor and the disenfranchised. )
The Quarter Scale Pilot Model, constructed by the author, including start up, operation, and any changes will be reported as a part of this tutorial. The and will be used as the "proof of Concept" for the bio-digester's design and function. It is strongly suggested that any student group do the same before a full or enlarged scale bio-digester is built. The Pilot Model becomes the training tool before full operations begin.
| Bill of Materials (Pilot Model): | ||||
|---|---|---|---|---|
| Material | Quantity | Unit Cost Each | Sub Total Cost | Source |
| 1/2" Treated Exterior Grade Plywood, 4;-0" x 8'-0' (supplier cut to 24" by 48"; makes 12 boards) | 3 each | $0.00 | $0.00 | Lowes Hardware |
| Treated Lumber, 2x10 x 10'-0" (supplier cut to 5'-0"; makes 2 boards) | 1 each | $0.00 | $0.00 | Lowes Hardware |
| Treated Lumber, 2x4 x 8'-0" | 8 | $0.00 | $0.00 | Lowes Hardware |
| Treated Lumber, 2x2 x 8'-0" | 4 | $0.00 | $0.00 | Lowes Hardware |
| #8, 15/8" long anti-rust Decking Screws | 1 small box | $0.00 | $0.00 | Lowes Hardware |
| Silicone 1*, Standard Waterproof Caulk, 100% Silicone | 3 tubes | $0.00 | $0.00 | Lowes Hardware |
| 4" PVC schedule 40 pipe | 10 Ft. | $0.00 | $0.00 | Lowes Hardware |
| 4" PVC schedule 40 Tee | 1 each | $0.00 | $0.00 | Lowes Hardware |
| 4" PVC schedule 40 cap | 2 each | $0.00 | $0.00 | Lowes Hardware |
| 4" PVC schedule 40 90o Elbow | 2 each | $0.00 | $0.00 | Lasco (manufacturer) |
| spare | spare | $0.00 | $0.00 | Lowes Hardware |
| 3/4" plastic tubing x 10' long | 1 each | $0.00 | $0.00 | Lowes Hardware |
| spare | spare | $0.00 | $0.00 | Lowes Hardware |
The first step will be to construct the "base unit" frame work. Step one it to mark the 2" edge of both the 2x10's six inches from one end. This is the first control mark. Now, place one of the 24" by 48" plywood boards to have the 24" end on the mark and leave ½" of the 2x10 outside of the 48" edge on both sides. With the plywood held firmly in place on the 2x10's, pilot holes will be drilled through the plywood and into the 2x10's at each end and about 6" along the 48" edge. The first 2" exterior wood screw will be set on each corner, then the screws can be set in the remaining pilot holes until all are filled. Next, mark 2x2's to fit between the 2x10's and cut to fit at each 24" end of the plywood, leaving ½" as was done with the 2x10's and, using the same procedure, fasten the 2x2's. Finally, drill a pilot hole through the 2x10's into the ends of the 2x2's, being careful to avoid the earlier screws set through the plywood into the 2x2's, and set one 3" exterior grade wood screw at each of the four corners. This will be the bottom section of the base unit.
The next step is to make the long sides of the base unit. The two long sides are built identically except with both, the smooth side is the inside of the Base Unit. We attach a 2x4, cut to 48" long on the rough side at each end of the 48" length of the plywood. The 2x4 is spaced outward from the plywood 2", one end of the 2x4 extended 6" past the "bottom" of the side on each end of the plywood, the the other end of the 2x4 will extend 18" above the "top" edge of the plywood. Once the two sides are put together, it would be wise to simply fit them to the sides of the bottom part to see that the plywood fits in the half inch slot we left when we attached the 2x10. Check to make sure that the ends of the side plywood fits against the bottom plywood and is flush at each end of the bottom plywood. If you wish, at this point, you could drill the pilot holes and fasten on 2½" screw through each 2x4 into the 2x10. Make sure that the fit is correct. These screws will be removed after the two ends are checked for proper alignment.
Now for the inlet end of the box. This ply wood need to be cut so that the 24" dimension remains and the length is cut to 25". Make sure you remember which is the 24" and which is the 25" side. It would be wise to make a mark to that this is not forgotten. Along the 24" side, add a 2x2 board cut to exactly 24". This board side fits flush to the 24's edge of the end plate on each side. This can be temporarily set to check fit by drilling a pilot hole about 12" down from the top edge and installing a 2½" screw. This, again is temporary and will be removed at a later date.
The outlet end will be cut the the same 25" along the length but the top edge will be trimmed off so that the 24' dimension become 23½". The 2x2 for each end is then cut to 237frac12; and installed as with the inlet end but with the ½" gap at the top edge of the box that is formed. The ½" gap by 24" long then gives one 12 square inches for the effluent discharge which will handle the approximate 12" inlet maximum flow the 4" diameter inlet piping will provide. This becomes the "effluent" outlet spillway. At this stage, we can consider building a trough to gather the effluent and direct it to the side such that the effluent might fall into a large bucket and then used to irrigate a garden. Note that the effluent may contain some alcohols and other organic compounds and should never be used for any other purpose other than irrigation that soaks directly into the soil. Keep safety in mind, always.
At this point, we need to check both ends for fit. Using the same as with the fit for the two sides, place both ends into place, drill the pilot holes at the top and the bottom, through the 48" long 2x4's attached to the sides and into the 2x2 of the ends. Remember, this is only a fit-up check and not the final installation. Once the fit is assured and correct but still held in place, we will need to mark the locations of the inlet piping. For the model, the inlet into the base box will come up from the bottom a short distance from the inlet end and centered into the bottom plywood. To make the inlet piping, we need two 90° slip x slip ELL (Elbows). Check to make sure that from the center line of the vertical end elbow opening to the end of the horizontal opening is 4¼". The insert dimension of the fitting is 2", so that a center line to center line dimension need to be twice 2¼" less for the cut line of the pipe length. This is the catalog dimension of the ELL made by Lasco and can very for products of other manufacturers but not likely. So that the lengths of the fittings of any size can be used, We will make our inlet piping to be a semi U shaped, with one leg to be 6" length of pipe, the 90°: elbow with enough of 4" pipe length to make the distance from the short leg center line to the second 4" 90°: elbow and long leg to be 7½". The long leg is 4" PVC pipe cut length is 36" long. The pipe and fittings will be Welded with standard PVC Liquid solvent designed specifically for this purpose. If one wishes and can find it, a 4x8 concentric socket weld reducer may be installed at the top of the long leg of the inlet piping to serve as a funnel.
Now that the inlet piping is designed and solvent welded together into one complete piece and checked to be sure there are no leaks along the piping and fittings, we need to establish a means of supporting this piping and the support must be sturdy enough so that it Will not be knocked loose while filling or transporting the digester. TO do this, we will add a 2x4 on edge between the two 2x10's on edge to fit between the two 90° ELL fittings. The dimension from the short leg of the U should be exactly 6" and 4½" down from the top edge of the 2x10. Use two 3" long screw at each end to fasten to the 2x10's. For support on the horizontal, we will add a 2x4 to the top and the bottom of the inlet end plate such that the 36" long vertical pipe will fit against it the use metal strapping to screwed into the edge of the 2x4's to hold it in place. This should become rugged enough to keep the pipping in place but allow for the screws to be removed should the piping need to be changed.
For the inlet piping, we Will use 4" standard wall (schedule 40) PVC pipe and fittings. This will provide us with a large enough opening that with the use of a funnel, we can pour a mixture of finally chopped leaves, garden clippings, grass clippings, and animal manure into the vertical end of the PVC piping. Note, for this pilot model and for safety's sake, we will not use any human waste. There is too much potential to deliver debilitating diseases if human waste is used in a "pilot" model which might be transported to schools and into communities for demonstration. The human and human household wastes will be reserved for full scale working biodigestion models that have other safety precautions built into them.
| Bill of Materials (Standard Design Model): | ||||
|---|---|---|---|---|
| material | quantity | unit cost each | sub total cost | source |
| concrete cut from 1/2" x 48" x 96" standard stock | 3 each | $0.00 | $0.00 | Lowes Hardware |
| Treated Lumber 2 x 4 x 8'-0" | 10 each | $0.00 | $0.00 | Lowes Hardware |
| #8, 15/8" long anti-rust Decking Screws | 1 small box | $0.00 | $0.00 | Lowes Hardware |
| Silicone 1*, Standard Waterproof Caulk, 100% Silicone | 3 tubes | $0.00 | $0.00 | Lowes Hardware |
| 2" PVC schedule 20 pipe | 20 Ft. | $0.00 | $0.00 | Lowes Hardware |
| 2" PVC schedule 20 threaded pipe Tee | 2 each | $0.00 | $0.00 | Lowes Hardware |
| 2" PVC schedule 20 threaded pipe cap | 2 each | $0.00 | $0.00 | Lowes Hardware |
| 2" PVC schedule 20 threaded pipe nipples | 2 each | $0.00 | $0.00 | Lowes Hardware |
| 2" pipe threader | 1 each | $0.00 | $0.00 | Lowes Hardware |
| 3/4" garden hose by 25 foot | 1 each | $0.00 | $0.00 | Lowes Hardware |
| spare | spare | $0.00 | $0.00 | Lowes Hardware |