Abstract:
Multiple Tray Vermicomposter with Thermal Siphon Airflow is a vermiculture composting device that uses earthworms to create compost where worms eat and digest food to excrete compost. It is a multiple tray system with a base and a lid. New compost trays with freshly loaded food and bedding are stacked on top of older trays containing worms and compost to instigate a continuous upward migration of the worms thereby creating continuous compost production. Compost trays have permeable bottoms to allow worms to pass through. Compost production is accelerated from thermal siphon airflow to provide ample airflow to the worms without the requirement of a power source. Light-tight air-permeable connections between trays, lid, and base, also accelerate compost production by keeping the worms completely dark. If worms fall through the bottom compost tray, there exists a ramp to enable the fallen worms to climb back into the bottom compost tray.

Description:
BACKGROUND OF INVENTION 
     This invention relates to composting devices. Composting is the purposeful biodegradation of organic matter such as yard and food waste to yield effective, natural nutrients for plants in the form of small dark chunks called compost and liquid called worm leachate. The decomposition is performed by micro-organisms like bacteria, yeasts, nematodes, protozoa, and fungi. Composting is naturally a relatively slow process. It could take up to two years, if left alone, for yard clippings and leaves to completely process into good compost. In low temperatures, a number of macro-organisms, such as springtails, ants, nematodes, isopods, and earthworms can accelerate the composting process. These macro-organisms aid the process because compost producing micro-organisms live inside the macro-organisms in large quantities. The large amounts of micro-organisms living in the digestive tracts of these organisms greatly accelerate the composting process. Also, sand particles in the digestive tracts of these organisms mechanically break down waste particles allowing the micro-organisms to consume waste faster. Under the right conditions, macro-organisms can thrive to continuously regenerate, in a controlled way, to eat large quantities of organic matter, allowing the micro-organisms to decompose the matter into compost in relatively short periods of time. This device specifically relates to a “vermicomposter” device which is a composting device that uses earthworms or worms to greatly accelerate the composting process. 
     Worms require moisture to breathe because they take in oxygen through their skin. They will die if their skin dries out. On the other hand, too much moisture in composting bins will produce unpleasant orders and worms could drown in moisture pockets in the bins. Unpleasant orders result from anaerobic bacteria which naturally crop up in waste material that is too moist. Organisms that accelerate the composting process, living within the worms, are generally aerobic, in that they require oxygen to live. Composting micro-organisms continuously use oxygen from air as a reactant to produce compost. Thus, increased oxygen accelerates the composting process. Anaerobic bacteria inhibit the composting process because they thrive in oxygen free environments and thereby expand such oxygen free areas, which in turn, depletes aerobic organisms, thereby slowing the compost rate. Thus, too much moisture greatly slows the process. On the other hand, too much oxygen, which comes from airflow, could dry out the worms and kill them, as stated above. Therefore there is an optimal balance between moisture and airflow regarding maximum production rate of compost in vermicomposters. 
     In nature, worms live in the upper surface of the ground at a dept of about 0-2 feet. When they are cold, they instinctually migrate upwards towards the surface of the ground, and when they get hot, they migrate downwards. Additionally, worms dislike sunlight because it dries them, thus worms readily move downward when confronted with sunlight. Additionally, worms migrate to find layers with abundant food supplies. When conditions are within the optimal range, worms do not migrate. 
     This device plays on these instinctual characteristics of worms to yield maximum compost rates. Specifically, the device consists of a tray system where trays are stacked vertically to form several layers of bins where worms can freely migrate between the bins according to their natural instincts. By controlling the migration between layers, the device produces compost quickly and conveniently. 
     SUMMARY OF THE INVENTION 
     It is an aspect of this invention to provide a vermicomposter that provides the optimal balance between oxygen flow and moisture to maximize the vermicomposting process. This device has compost production rate of one bin or tray of compost per 6-12 weeks. 
     Gases and heat are produced by the composting process. These gases block oxygen from the micro-organisms, which slows the process. Heat slows the process as well because heat dries and kills the worms. Thus, it is another aspect of this invention to provide rapid removal of gases and heat from the device. 
     Worm leachate is liquid produced by the worms and is not toxic to worms in any way. On the other hand, tap water or garden hose water may have chlorine or other chemicals in it that can be toxic to worms. Thus, worm leachate is a good liquid to reintroduce into the device to strike the optimum balance mentioned above. Also, worm leachate is terrific natural plant fertilizer. Thus, it is an aspect of this invention to include a collection tray that is capable of collecting worm leachate produced from the device which can be conveniently reintroduced to the vermicomposter or simply used as plant fertilizer. 
     With commercial or other accelerated composting devices, control of these parameters is accomplished typically through the use of outside powered means such as with fans, pumps, powered air flow, water flushing, mechanical aeration, stirring, flipping, powered heating, powered cooling, and the like. However, these means require the addition of outside energy which is undesirable for convenience, economic, and environmental reasons. Thus, it is also an aspect of this invention to control such parameters without the use of an outside power source. 
     It is another aspect of this invention to provide a vermicomposter that can be readily operated by one person. The device can be easily assembled, lifted, and carried by an average sized person. The device is useful to the average consumer. The device can be placed in a yard, patio, balcony, basement, or the like. 
     Many composting devices basically consist of one bin. There is a disadvantage to these devices because you cannot add new waste to the bin without disrupting and contaminating the existing composting process in the bin. There is no practical way to add new waste and remove high quality compost from these devices. Thus, it is another aspect of this invention to provide a practical method to add new waste and remove high quality compost from a vermicomposter without disruption of ongoing processes. This is accomplished by a multiple tray system. 
     The multiple tray system also provides control over worm migration as discussed below. Thus, it is another aspect of this invention to provide worm migration control among several layers of worm habitat within the device. 
     As stated above, light is undesirable to the composting process. However, in order to generate the required airflow in the device, gaps, holes, or vents are required to provide such. Thus, it is also an aspect of this invention to provide air-permeable and light-tight connections between the trays and other members of this device. 
     To achieve the optimum balance between airflow and moisture, there exists a minimum and maximum air gap between members to allow optimum flow through the composting areas which is determined by the amount of composting volume in the device. Thus, it is also an aspect of this invention to provide a device with total air or oxygen venting within this range. 
     It is also an aspect of this invention to have stacking trays with apertures in the bottoms thereof that are appropriately sized to allow proper airflow while retaining the appropriate amount of moisture within the stacking tray. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of the invention with depiction of airflows. 
         FIG. 2  is an exploded perspective view of the invention in best mode square configuration. 
         FIG. 3  is a perspective view of the base/collection tray in best mode square configuration with blow-up of support rib with notch. 
         FIG. 4  is a front view of base. 
         FIG. 5  is a plan view of base/collection tray in best mode square configuration. 
         FIG. 6  is a plan view of WORM LADDER® and a cross-section view of WORM LADDER®, both in best mode square configuration. 
         FIG. 7  is a perspective view WORM LADDER® assembled on base both in best mode square configuration. 
         FIG. 8  is plan view of WORM LADDER® assembled on base/collection tray and a cross-section of the same. 
         FIG. 9  is a perspective view of WORM LADDER® assembled on top of base/collection tray, in best mode square configuration, depicting how worms can climb up WORM LADDER®. 
         FIG. 10  is a perspective view of a best mode square-shaped stacking tray. 
         FIG. 11  is a plan view of a best mode square-shaped stacking tray. 
         FIG. 12  is a top perspective view of best mode square-shaped light-tight air-permeable lid. 
         FIG. 13  is a bottom view of best mode square-shaped light-tight air-permeable lid. 
         FIG. 14  is a side-view of best mode square-shaped light-tight air-permeable lid. 
     
    
    
     DEFINITION LIST 
     
       
         
               
               
             
               
               
             
           
               
                   
               
               
                 Term 
                 Definition 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10 
                 Base 
               
               
                 11 
                 Leg of Base 
               
               
                 20 
                 WORM LADDER ® 
               
               
                 21 
                 Horizontal Flange Area on WORM LADDER ® 
               
               
                 22 
                 Ramp on WORM LADDER ® 
               
               
                 23 
                 Large Void Area in WORM LADDER ® 
               
               
                 30 
                 Stacking Tray 
               
               
                 31 
                 Wide Brim on Stacking Tray 
               
               
                 32 
                 Side of Stacking Tray 
               
               
                 33 
                 Bottom of Stacking Tray 
               
               
                 34 
                 Apertures in Bottom of Stacking Tray 
               
               
                 35 
                 Stacking Ribs on Stacking Tray 
               
               
                 40 
                 Light-tight Air-permeable Lid 
               
               
                 41 
                 Large Dome Area on Lid 
               
               
                 42 
                 Large Flat Area on Dome Area 
               
               
                 43 
                 Steep Sloped Edges on Dome Area 
               
               
                 44 
                 Wide Brim on Lid 
               
               
                 45 
                 Skirt on Lid 
               
               
                 46 
                 Vertical Support Ribs on Lid 
               
               
                 47 
                 Horizontal Support Ribs on Lid 
               
               
                 50 
                 Collection Tray 
               
               
                 51 
                 Side of Collection Tray 
               
               
                 52 
                 Bottom of Collection Tray 
               
               
                 53 
                 Support Ribs in Collection Tray 
               
               
                 54 
                 Notches on Support Ribs in Collection Tray 
               
               
                 55 
                 Bottom Surface of Notch 
               
               
                 56 
                 Side Surface of Notch 
               
               
                 57 
                 Side Vent Distance 
               
               
                 58 
                 Lower Vent Distance 
               
               
                 59 
                 Drain Hole in Collection Tray 
               
               
                 60 
                 Lower Perimeter Air Gap 
               
               
                 65 
                 Lateral Air Flow 
               
               
                 70 
                 Upper Perimeter Air Gap 
               
               
                 80 
                 Worms 
               
               
                 90 
                 Food and Bedding for Worms to Eat and Live In 
               
               
                 100 
                 Thermal Siphon Volume 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION 
     New compost trays or stacking trays with freshly loaded bedding and food material for worms are stacked on top of older trays. When worms from below are finished eating food or waste from older stacking trays or when they have a taste for fresher larger pieces of waste they migrate upwards. They may also migrate back downward when they have a taste for smaller pieces of waste. Waste pieces are reduced in size as the composting process or worm feeding process continues. Typically worms prefer smaller pieces of waste over larger pieces. Worms generally do not migrate when conditions are in the preferred range. Thus, worms generally remain in a tray until waste is completely depleted into compost without any small chunks of food or waste product. At that time, worms generally migrate upwards to the next newest tray with newer larger chunks of food or waste. The stacking tray system in this regard yields trays with good compost on the bottom and trays with uncompleted compost production toward the top. By the time waste has been completely processed into good compost on the bottom tray, all or most worms have migrated upward to trays above. In this way, completed trays can be separated from non-completed trays and removed form the system without any adjusting any waste, compost, or worms and the like. The system of adding trays and removing trays in this fashion leads to a fast, environmental, and convenient compost production process. 
     The initial tray must be loaded with food, bedding, and about 500 worms. With this device, worm populations double every three months, so no addition worms need to be loaded into any additional trays or bins. Worms will reproduce and migrate naturally into new trays. When the device is working properly, each tray undergoing the composting process, houses about 3,000 worms. Obviously, the more worms, the faster the production rate of compost, at least up to saturation population, which is more than 3,000 worms per tray. Excess worms are lost with the harvest of the bottom tray which keeps populations below saturation. 
     It is believed that the “red wiggler” species of worm, Latent name Eisenia Fetida, produces compost at the fastest rate among worm species. Thus, this device is designed to produce optimal conditions for the red wiggler to live in the device. Other species of worms may find the environment of this device to be less than ideal. 
     The invention comprises: a base  10  with collection tray  10 , at least one stacking tray  30 , and a light-tight air-permeable lid  40 . These members must have generally the same geometric shape as viewed from top elevation because these members must “stack” together or fit together, when assembled vertically, to form light-tight connections between the members of the vermicomposter device. The best mode geometrical shape is square, however other shapes such as circular or other polygonal may be used. 
     Base  10  is a sturdy base which supports the rest of the device slightly above the surface of the ground, deck, or floor. At this level air may freely flow upwards through and laterally through the device. See  FIG. 1 . Also, at this level, a container (not shown) may be place below the collection tray  50  so that the collection tray  50  may be drained of a liquid collected in the tray  50 , which can be drained by gravity, into the container. The base  10  has at least three legs  11  which support the rest of the device slightly above the surface of the ground, deck, or floor. Legs  11  support and hold steady the rest of the device at essentially a horizontal orientation. Horizontal orientation is required so the fluid, called worm leachate, which is a chemical product of the vermiculture process, can drip down and collect in the collection tray  50 , and be retained by the collecting tray  50  or container. Worm leachate forms in the stacking trays  30  and flows downward by gravity, eventually dripping into the collection tray  50 . Therefore, all stacking trays  30 , collection tray  50 , and lid  40  should remain horizontally level when the device is in operation. The at least three legs  11  perform this function. Worm leachate may be used as a very effective natural plant fertilizer or to safely add moisture back to the stacking trays  30 . 
     The upper surface of the base  10  forms the collection tray  50 . Thus, the collection tray  50  is integral to the top surface of the base  10 . The collection tray  50  comprises: a set of sides  51 , a bottom  52 , a set of support ribs  53  with notches  54 , and is open on the top to form a liquid-tight container. The set of sides  51  collectively forms essentially a continuous polygonal or circular wall member, where sides are contiguously joined at their sides, surrounding the perimeter of the bottom  52 . Bottom  52  is generally horizontal member with similarly shaped perimeter to the set of sides  51 . The set of sides  51  and bottom  52  form the open top container or well. The sides  51  and bottom  52  are solid members without holes or apertures to yield a liquid-tight container. Sides  32  have height sufficient to hold about  2 - 3  weeks production of worm leachate from several stacking trays and also allow for the required air gap  60  (described below) beneath the bottom surface of the lower stacking tray  30  or WORM LADDER®  20 . Collection tray bottom  52  may have slightly non-horizontal surfaces or contours that create downward grades in the bottom surface leading to a low point in the container structure, where, generally, a hole in the container structure may be located. This drain hole  59  is used to drain the collection tray  50 . A drain valve (not shown) may be installed into drain hole  59  to control the drain flow of worm leachate stored in the collection tray  50  or drain hole left open to drain into container without valve to ensure maximum air gap (discussed below). Worm leachate may be used to fertilize or re-introduce moisture into the device. Or drain hole  50  is simply left open to drain into container below. 
     To assemble the device, the base  10  is placed on the ground, deck, or floor with its collection tray  50  facing upwards and positioned horizontal. The WORM LADDER®  20  is then placed inside the collection tray  50 , with WORM LADDER®  20  also in horizontal orientation, nested within a pocket of notches  54  (described below). The purpose of the WORM LADDER® is to provide “a ladder” for worms to use to climb back up into the lower stacking tray  30  after the worms have fallen through an aperture  34  down into collection tray  50 . Worms fall through from time to time during the vermiculture process. WORM LADDER® is a registered trademark owned by Anderson Die &amp; Manufacturing Company and its use for commercial purposes is strictly prohibited by law without consent from Anderson Die &amp; Manufacturing Company. 
     One mode of the invention further comprises a WORM LADDER®  20 . WORM LADDER® comprises: a horizontal flange  21 , at least one ramp  22 , and large void area  23 . Horizontal flange  21  is the upper most portion of the WORM LADDER®  20  and is essentially a flat flange member in the same shape of a stacking tray  30 , with the same number of sides or circular, as viewed from plan view. Horizontal flange  21  has a large void area  23  in the center to allow air flow through the WORM LADDER®  20 . With square stacking trays  30 , flange  21  is shaped like a square rim member. Ramps  22  are coupled to the inner edge of flange  21 . Ramps  22  are planar and coupled at one edge to the inner edge of the horizontal flange  21 . Ramps  22  may lead down from the flange  21  to rest on bottom  52  of collection tray  50 . Thus, the edge opposite the flange edge may touch bottom  52 . Ramps  22  may be coupled to flange  21  by a bendable or hinged connection. Thus, ramps  22  may be bent downward during installation of WORM LADDER®  20  to ensure that all ramps  22  actually rest on bottom  52 . There must be ample clearance around the other ramp edges to allow clearance for hinge action of multiple ramps at once and provide clearance for minimum air gap (described below). One mode of ramp  22  for a square system is trapezoidal planar, with the long parallel edge coupled to inner edge of flange  21 . Best mode ramps  22  are attached to each other at their short edges. Thus, ramps  22  form a rim shaped member as well. With this mode, the minimum air gap must exist completely under the WORM LADDER®  20  to allow for the required airflow. Thus, the minimum air gap must exist between the upper surface of worm leachate sitting in the collection tray  50  and the lower surface of the WORM LADDER®  20  at all times to allow for the required air flow. Thus, ramps  22  do not touch bottom of collection tray in best mode. Worms can span a small air gap of at least one inch or so. 
     A stacking tray  30  may then loaded with bedding and food and placed on the WORM LADDER®  20 . In the case of the initial stacking tray used to start the device, an initial deposit of starter worm must be made. A stacking tray  30  comprises: a wide brim  31 , a set of sides  32 , a bottom  33 , and is open on the top. The set of sides  32  surrounds the entire perimeter of the bottom  33  where sides  32  collectively form essentially a continuous polygonal or circular wall member, where said sides are contiguously joined at their sides, surrounding the perimeter of the bottom  33 . Joined at the top of sides  32  is wide brim  31 , which is a flange member that has horizontal flange surface generally perpendicular to the sides 32 , where flange member  31  extends radially outward from sides  32  to an outer edge. Wide brim  31  runs along the entire perimeter of the upper surface of the stacking tray  30 . With best mode square stacking trays, wide brim  31  is a square rim member. Wide brim  31  is required to add structural integrity to the stacking tray  50  which would otherwise be somewhat flimsy as a result of the open-top configuration of the member. The bottom  33  of the stacking tray  30  is generally horizontal and acts as a bottom support member for material that is loaded into the tray. Bottom  30  has many apertures  34  in it that are sized to allow the free passage of air between the apertures  34  while still keeping in tact bedding and food within the tray  30 . Apertures  34  are also sized to allow worm leachate to freely drip through apertures  34 . Compost and worms can sometimes fall through apertures  34 . Best mode bottom  33  includes apertures  34  sized at about 0.25″ square and are positioned throughout the entire bottom area to provide free flow of air throughout the bottom area. The sides  32  of the stacking trays  30  are solid to prevent the passage of light into the trays. As stated above, light shining directly onto the worms, bedding, or food substantially disrupts the vermicomposting process and is undesirable. Sides  32  of stacking trays have height appropriate to load several alternating layers of bedding and food inside of a tray, each layer ranging from 1-4″ thick with empty air space of at least a few inches at the top of the tray. All sides  32  of a tray  30  must have the same height. The best mode height of side  32  or depth of a stacking tray  30  is about 5″. This depth of stacking tray was chosen because it yields an overall assembled device size that is easily handled by one person while large enough to allow for substantial compost production. 
     When a stacking tray  30  is placed on the WORM LADDER®  20 , the tray “nests” slightly within base  10  in a stable position where the bottom surface of the stacking tray  30  sits slightly below the top surface of base  10 . Thus, the stacking tray  30  rests slightly inside collection tray  50 . This arrangement prevents any light shining on the side of the vermicomposter from shining inside a stacking tray  30  system. 
     There is a perimeter air gap  60  around the entire perimeter of the connection between base  10 , WORM LADDER®  20 , and bottom stacking tray  30  that allows the free flow of air from outside of the device to the inside of the stacking trays through gap  60  and apertures  34 . This gap is the lower perimeter air gap  60 . The lower perimeter air gap  60  is sized to provide an air flow generated by thermal siphon (see blow) that yields an optimal temperature range of about 60-80° F. with moisture range of about 60-80% inside of the collection trays  30  with the device loaded properly and placed in a cool, dry, shaded place such as barn, shed, porch, basement, garage, or other location with ventilation and shade from sunlight. The device is not designed to be placed in direct sunlight or rain. Air gap vent  60  allows for free airflow through the device without any appreciable sheer forces acting on the air as it flows through air gap vent  60 . 
     Air flow is created by a thermal siphon effect where heat and gasses are generated inside of the tray from the composting process. These hot gasses naturally travel upwards thereby pulling cooler air from below along with it, creating a general upward flow of air. The larger the area of bottoms  34  with apertures  34  of the stacking trays  30 , the larger the air gap required to provide ample air flow to yield maximum compost rate. Experimentation has determined that the total area of air gap must be at least three percent of the bottom area  34  in the stacking tray for a  5 -stacking tray embodiment. Best mode allows for a stacking tray with a 14.25″ by 14.25″ loading area and an air gap of 0.25″ around the full length of the perimeter of the bottom of tray  30 . Thus, there must be a least a 0.25″ are gap around the entire bottom surface of the lower stacking tray in one embodiment or the entire bottom surface of the WORM LADDER® to allow proper airflow. These dimensions yield an air gap that is about 3.5% of the area of bottom  34 . This arrangement yields a light-tight air-permeable connection between the base  10  and stacking tray  30  with WORM LADDER®  20  as an intermediate member. 
     The lower perimeter air gap  60  is accomplished with the set of support ribs  53  which are located on the upper surface of the base  10  which is collection tray  50 . Support ribs  53  are vertically oriented rectangular planer members that stand perpendicular to the inner surface of sides  51  of collection tray  50 . Support ribs  53  are joined at their outside edge to sides  51  to form a T-connection with side  51 . Support ribs  53  act as small support columns positioned around the edge of the collection tray  50 . Support ribs  53  rise to the same level as the top surface of the base  10 , thus height of ribs  53  is equal to height of sides  51 . Ribs have width running in the direction perpendicular to the inner surface of sides  51 . At least one support rib  53  per side  32  of stacking tray  30  is required to keep the tray supported level. Thus, with best mode square-shaped stacking trays  30 , at least four support ribs  53  are required in the collection tray  50 . The current best mode base  10  uses 2-3 support ribs  53  per side  32  which yields more than ample support for several loaded stacking trays  30  and lid  40 . 
     There is a notch  54  sectioned out of the upper inner corner of each support rib  53 . A notch  54  is an L-shaped void in the upper inner corner of each support rib  53 . Each notch defines on the rib: a notch bottom surface  55 , a notch side surface  56 , a side vent distance  57 , and a lower vent distance  58 . Notches  54  and ribs  53  are appropriately positioned and sized so that the bottoms of the particularly shaped of the WORM LADDER®  20  and stacking trays  30  fit inside a “pocket” formed collectively by all notches  54  in ribs  53 . The pocket aligns base  10 , WORM LADDER®  20 , and stacking tray  30  in concentric position. As stated above, to be stackable, WORM LADDER®  20  and stacking trays  30  must have similarly shaped footprints. Thus, with best mode square stacking trays  30 , the pocket formed by notches  54  and ribs  53  is also square-shaped. 
     The lower perimeter air gap  60  provides an airflow path beneath the WORM LADDER® and into the stacking tray apertures  34 . This is accomplished as follows. The WORM LADDER®  20  sits on notch bottom surfaces  55 . Thus, there exists an air gap between the outer edges of the WORM LADDER®  20  and the inner surfaces of sides  51  where this gap is at least side vent distance  57 . Below the WORM LADDER®  20 , there exists a gap between the lower surfaces of the WORM LADDER®  20  and the upper surfaces of bottom  52  where this gap is at least lower vent distance  58 . Thus, with a minimum air gap requirement of 0.25″, dimensions  57  and  58  must be at least 0.25″ to allow adequate airflow for maximum compost production. Lower vent distance  58  must also be large enough to allow for the minimum air gap to exist above the surface of worm leachate collecting in the collection tray  50 . 
     The bottom stacking tray  30  is supported vertically by WORM LADDER®  20 , which is supported by notch bottom surfaces  55 . The bottom stacking tray  30  is supported laterally by notch side surfaces  56 . The WORM LADDER® and stacking tray sit in notches  54  of the ribs  53  which are the sole means of support for these members. Ribs can be 0.0625-0.25″ thick. Best mode ribs  53  are about 0.125″ thick because this is about the thinnest ribs can be while still providing more than ample structural support for several loaded stacking trays  30  and lid  40 . This support means yields the lower perimeter air gap  60  between the bottom of the WORM LADDER®  20  and the inner surfaces of the sides  51  and upper surfaces of bottom  52  of the collection tray  50 . Technically, the air flow through the lower perimeter air gap  60  is obstructed by the support ribs  53 , however, since ribs  53  are relatively thin, only 0.125″, the obstruction is negligible, and there is no appreciable sheer force on the air flow. 
     Another loaded stacking tray  30  is placed on top of the first loaded stacking tray  30 . As many as  10  loaded stacking trays may be used. When a tray  30  is loaded, food and bedding layers typically rise at least to about the half-way point of side  32  of tray  30 . With the best mode 5″ deep stacking tray  30 , the layers may rise to about 3″ in the tray  30 . Thus, when a second or top tray  30  is stacked on the first or bottom tray  30 , the bottom surface of the second tray  30  actually sits on top of and is supported by the food and bedding loaded in the first tray  30 . Stacking trays  30  are kept concentric as they are vertically stacked because the bottom of one snuggly fits inside the top of the other where stacking trays  30  are identically shaped. By loading and stacking the trays  30  in this fashion, an air gap remains around the perimeter of the connection between the stacking trays  30 . This air gap is similar to the perimeter air gap described above however the gap may be smaller here. This is because the primary airflow should remain in an upward direction for maximum compost rate; however, some lateral air flow  65  is desirable to provide bedding aeration. Thus, gaps exist around all perimeters of all connections between members of this device. 
     In best mode, stacking trays  30  have stacking ribs  35  on the outside surfaces of the sides  32 . Ribs  35  protrude essentially perpendicularly out of sides  32 . Stacking trays  30  should have at least one rib  35  per side  32 . Ribs  35  provide support between stacking trays  30  when they are stacked while empty and unloaded. The trays  30  would tend to stick together without ribs  35 . When stacked in this fashion, the bottom surface of bottom  33  of top tray  30  fits within the open top of the bottom tray  30  and slides into the bottom tray until a rib  35  on the top tray abuts against the upper surface of wide brim  31  of the bottom tray. Stacking is necessary to reduce the overall shipment size of the device and for convenience of storage. 
     The light-tight air-permeable lid  40  is used to cover the upper most stacking tray and provide a light-tight air-permeable cover for the device. The lid comprises: a large dome area  41 , a wide brim  44 , a skirt  45 , a set of vertical support ribs  46 , and a set of lateral support ribs  47 . Large dome area  41  of the lid  40  extends above the brim  44  and is the upper most portion of the lid  40 . Large dome area  41  has an inner or lower surface which forms a large general concave downward shape and an outer or upper surface. The upper surface of dome area  41  is the upper most portion of the device. Large dome area  41  may have a large flat area  42  on top, with gentle downward and outward grade to allow drainage of rainwater and the like off the top surface of the member, and steep sloped edges  43  leading downward to the wide brim  44 . Large dome area  41  forms a space where hot air and other hot gasses collect. The length and width or area of the large dome area  41  should match those of the bottom  33  of stacking trays  30 . Thus, there should be dome space above the entire bottom  33  of the upper stacking tray  30 . This space is required to ensure the thermal siphon air flow action described above. The dome space allows a relatively large portion of the warmest air and gasses in the device to collect at the top of the device. This warm air “primes” the thermal siphon pump action and keeps the flow of air moving in the general upward direction. The large dome area  41  enables an upward airflow without the use of fans or pumps. 
     An upper perimeter air gap  70  is required around lid  40  to maintain general upward airflow. Thus, there must be a perimeter air gap  70  of at least three percent of the total bottom area  52  of a stacking tray  50  to ensure adequate air flow. As stated above, the best mode perimeter air gap is 0.25″ which corresponds to the best mode bottom  52  which is 14.25″ square. 
     The upper perimeter air gap  70  is accomplished by the set of vertical support ribs  46  and the set of lateral support ribs  47 . Vertical support ribs  46  are horizontally oriented rectangular planar members that are joined at their upper edge to the bottom surface of wide brim  44  of support lid  40 . Vertical support ribs  46  support lid  40  above the upper most stacking tray  30  at the required distance to yield the appropriate air gap. This means that ribs  46  must have a minimum height that is no less than the required air gap size. Best mode vertical support ribs  46  support the lower surface of lid brim  44  about 0.25″ above the upper surface of tray brim  31 . Thus, vertical support ribs  46  are about 0.25″ in height. Vertical support ribs  46  are oriented radially outward from the center of the lid  40 . The width of ribs  46  must be equal to or wider than the width of wide brim  31  on a stacking tray to form the air gap. As with the large dome area  41 , the wide brim of the lid  44  may have a slight downward and outward grade on its upper surface to allow drainage of rainwater and the like. Thus, with a graded brim  44 , vertical support ribs  46  would have to be slightly taller than the required air gap distance in order to ensure that the minimum gap exists along the full width of the stacking tray brim  31 . The height of best mode vertical support ribs  46  on lid  40  with downward grade brim  44  is about 0.375″. There must be at least one vertical support rib  46  per side of stacking tray  30 . Best mode allows for one vertical support rib  46  per side with the addition of one vertical support rib  46  in each corner of the square-shaped stacking tray  30 . Thus, in best mode, there are eight vertical support ribs  46  on lid  40 . The use of extra ribs helps ensure that the minimum air gap remains around the entire perimeter of the lid. 
     Wide brim  44  of the lid  40  must completely cover wide brim  31  of stacking tray  30  in order to create the light-tight seal. Otherwise, light could shine directly downward into the food and bedding through a gap that would exist between the outer edges of the lid  40  and the inner surfaces of the sides  32  of tray  30 . Both brims  31  and  44  are essentially horizontal, noting that lid brim  44  made have slight downward and outward grade. Wide brim  44  of lid  40  sits above wide brim  31  of the tray  30  with lid  40  placed on the device. Thus, to provide complete cover, wide brim  44  should be slightly wider than wide brim  31  to provide a overhang ledge to keep light from shining directly down in the upper stacking tray  30 . 
     Skirt  45  is required to prevent light from shining laterally into upper stacking tray  30  through the air gap between lid brim  44  and tray brim  31 . The skirt  45  is added to block this light. Skirt  45  is generally a vertical rim member and is attached to wide brim  44  of lid  20  at its upper edges. Skirt  45  hangs downward from the outer edges of brim  44  around the entire perimeter of the brim  44 . In order to block the lateral light, brim  44  must have length at least equal to the air gap between brims. Best mode skirt length is about 0.25-0.375″. Vertical support ribs  46 , which extend radially outwards, are joined at their outer ends to the inner surfaces of skirt  45 . This adds structural integrity to ribs  46  and skirt  45 . 
     The minimum upper perimeter air gap  70  must also exist between the inner surfaces of skirt  45  and the outer surfaces of stacking tray  30 , which is the outer edge of wide brim  31 . Otherwise, skirt  45  would choke down on tray brim  31  and impede the airflow to disrupt the composting process. Thus, lid wide brim  44  must extend wider than that of stacking tray brim  31  by at least the amount of the minimum air gap distance. Lid brim  44  must extend beyond tray brim  31  to yield perimeter air gap  70  between the skirt  45  and the tray brim  31 . The thickness of the material of the lid  40  must also be taken into account. Thus, with best mode air gap of about 0.25″ and lid material thickness of about 0.125″, where the best mode tray brim is 0.75″ wide, best mode lid brim  44  has width of about 1.125″. In this way, wide brim  44  of the lid  40 , skirt  45 , and vertical support ribs  46  yield a light-tight air-permeable connection. 
     Lid  40  must be kept concentric with the upper stacking tray  30  to keep air gap  70  continuous and constant around the perimeter of the connection. Horizontal support ribs  47  help guide and hold lid  40  into a concentric position with the upper stacking tray  30 . Horizontal support ribs  47  should have height greater than that of the vertical support ribs  46  because horizontal support ribs  47  must extend slightly down into the upper most stacking tray  30  so that the horizontal support ribs  47  slide against the inner surfaces of sides  32  when moved laterally into a non-concentric position. Thus, horizontal support ribs  47  act as prongs to funnel the lid into concentric position as the lid  40  is placed on top of the upper tray  30 . Horizontal support ribs  47  are best positioned at all corners of the particularly shape of stacking tray  30 . Thus with best mode square shaped stacking trays, there should be  4  horizontal support ribs  47 . With circular stacking trays, which do not have corners, horizontal support ribs  47  may be position at the four quadrants of the circular shape.