WO2014143741A1

WO2014143741A1 - A method for composting organic waste

Info

Publication number: WO2014143741A1
Application number: PCT/US2014/027828
Authority: WO
Inventors: Paul S. Mankiewicz
Original assignee: Gaia Institute
Priority date: 2013-03-15
Filing date: 2014-03-14
Publication date: 2014-09-18

Abstract

A method for composting organic waste by depositing recycled foam in a container. The container having an inlet port, an exhaust port and a waste impermeable, but air permeable air floor, the inlet port and exhaust port being disposed so as to allow gas to travel into the container through the inlet port, through the air floor and out of the container through the exhaust port. The recycled foam filling the container from 1/3 to 2/3 by volume. Organic waste is deposited in the container to fill the container. The organic waste and the recycled foam are mixed.

Description

A METHOD FOR COMPOSTING ORGANIC WASTE

CROSS REFERENCE TO RELATED APPLICATION(S):

[0001] This application claims the benefit of U.S. Provisional Patent

Application No. 61 /792,446, filed March 15, 201 3, the contents of which are herein incorporated.

[0002] This invention is directed to a method for utilizing an organic food waste composter, and in particular, optimizing the operation of the organic waste composter by utilizing hydrophobic lightweight foam as an aerator so moist to wet organic waste flows from top to bottom down a density gradient, with oxygen supplied and excess heat eliminated by air flow in passages between foam chunks.

[0003] Organic waste composting systems are known in the art such as from Applicant's U.S. Patent No. 5,948,674 which describes an organic waste composting system having a container with a gas impermeable floor, sides and top. A gas inlet port and a gas exhaust port are provided in the container. An air floor is provided within the container, the air floor being gas permeable and impermeable to solids contained within the container. The system further includes a mixing blade dimensioned so that the shear forces produced by the blade when rotated within the organic waste are substantially equal to the viscoelastic forces of the organic waste particles. The mixing blade is dimensioned to further shear the waste to a size which increases its surface area to volume ratio without compacting it, thus providing suitable moisture distribution, particle distribution, and air channels between the particles.

[0004] This organic waste compactor and compacting method has been satisfactory. However, it suffers from the disadvantage that it requires several days to compost waste and often requires several iterations of downstream composting to arrive at a useable end product. It also is run as a batch system, as opposed to continuous feed throughput, and moisture level has to be maintained around 50% to 55% to maintain porosity. [0005] Accordingly, a method which overcomes the shortcomings of the prior art is desired.

SUMMARY OF THE INVENTION

[0006] A method for composting organic waste comprises the steps of filling a cylindrical vessel between 1 /2 and 2/3 full by volume with recycled foam, each piece of recycled foam having a diameter of between 1 " to 3+". The remaining volume of the cylindrical vessel is filled with organic waste. A shaftless auger is placed within the cylindrical vessel to mix the organic waste and recycled foam and a container lid is placed on the container. Air is passed through the air floor of the container and travels through larger, low resistance air channels in the organic waste foam mixture to create an oxygen pathway oxygenating the bacteria in the moist to wet mixture which decomposes the organic waste.

[0007] In an exemplary embodiment, the recycled foam is formed of polystyrene, polyurethane, or other low density space filling plastic structures or the like. The container has a gas inlet port and a gas exhaust port. An air floor is gas permeable but can be permeable to solids contained within the container. The mixing blade of the auger is dimensioned so that the shear forces produced by the blade and rotated within the organic waste are substantially equal to the viscoelastic forces of the organic waste particles. A mixing blade may be flattened and beveled at one end and dimensioned to further shear the waste to a size which increases its surface area to volume ratio without compacting it, providing a high moisture level and material distribution and air channels between composting masses divided and spread along the foam and organic waste interface.

[0008] Compost 10 requires the promotion of motion within the container. Therefore, either, alternatively or in concert with the shaftless auger mixing method, a concrete or industrial vibrator within or against the compost vessel may be turned on periodically to facilitate the flow of higher density moist composting organic waste in the downward direction and the 'floating upward' of the low density foam, facilitating diffusion and mixing and opening air passageways in the process. http://www.harborfreight.com/power-tools/concrete-vibrators.html http://www.dahnkesales.com/vibrator.htm

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a fuller understanding of the invention, reference is had to the following description, taken in connection with the accompanying drawings in which:

[0010] Fig. 1 is a schematic sectional view of an organic waste composting system utilized in accordance with the present invention;

[0011] Fig. 2 is a top plan view of an air floor assembly for use in the organic waste composting system of the present invention;

[0012] Fig. 3 is a bottom plan view of the drive configuration for the auger constructed in accordance with the invention;

[0013] Fig. 4 is a schematic view of one embodiment of an auger used in accordance with the invention;

[0014] Fig. 5 is a schematic view of a plurality of organic waste composting systems of the present invention connected in series in accordance with the present invention;

[0015] Fig. 6 is a schematic view of a plurality of organic waste composting systems of the present invention connected in series in accordance with the present invention;

[0016] Fig. 7 is a fragmented enlarged sectional view of an organic waste foam mixture showing air channels in detail;

[0017] Fig. 8a is a sectional view of the base of the mixing blade constructed in accordance with another embodiment of the invention;

[0018] Fig. 8b is a sectional view of the tip of the mixing blade constructed in accordance with another embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] The present invention is directed to a container and mixer and/or vibrator which converts a pre-compost mixture of organic waste and recycled foam into a substantially fully composted product and a method of waste thereof. The pre- compost solution contained within the container is a mixture of organic waste, such as foodstuffs, and recycled foam pieces. As shown in FIG. 1 , an organic waste composting system 100 includes a container 10 for forming compost therein and a mixing assembly 150. Container 1 0 is provided with an air inlet port 30 and an air exhaust port 40.

Container 10 includes side wall 15, a sealed bottom, which can be cone shaped to facilitate collection and material handling of continuous throughput 14 and a removable top 12.

[0020] Container 10 includes an air inlet port 30 for bringing air into container 10 and an exhaust port 40 for exhausting gaseous by-products from container 10. An air floor 20, is disposed within container 10 above air inlet port 30, is air permeable and permeable to flow of composted organics but impermeable to foam chunks sized to remain above the screen air-floor bottom. As shown in FIG. 2, a preferred embodiment of air floor 20 includes a perforated, reinforced fabric or plastic disc 22. Container 10 is gas and liquid impermeable. Container 10 may also be made of other impermeable materials such as PVC o other rigid plastic, or may be made collapsible by using polyvinyl chloride (PVC) film, a geotextile bag or the like. Where container 1 0 is made of a thin film bag, air floor 20 may comprise a pallet upon which sits container 10 with a perforated air floor fabric positioned above a well in the pallet. A fan or blower 51 may be attached directly to the well in the pallet to blow air into container 10. In a preferred embodiment, container 10 is a 55-gallon drum, but may be larger or smaller depending on the user's composting scale. Top 12 may be removable and impermeable to gases. Top 12 forms an airtight seal when in the closed position.

[0021] Mixing assembly 1 50 may be any structure or mechanism to promote motion between the foam particles and organic waste. Preferably mixing assembly 150 comprises at least one mixing blade 60 which is rotatably driven by drive gears 50, which in turn is driven by a motor. Alternatively, mixing blade 60 may be manually driven. Mixing assembly 150 is preferably mounted to floor 14 and is configured independent of top 12 and may be utilized while top 12 is removed from container 10.

[0022] Mixing blade 60 is designed so that the blade width and curvature radius are dimensioned so that the shear forces produced by the rotating blade within the viscous material of a pre-compost mixture are substantially equal to the viscoelastic forces for the particular particle size making up a pre-compost mixture of moist to wet viscous fluid. Blade 60 may be designed as a function of the Reynolds number, Re, where:

Re=D6v/u

Where D is the scale of the mixing blade, d is the density of the fluid, v is the velocity of the blade within the fluid and u is the viscosity of the fluid. The Reynolds number is not directly applicable to a composting system because the Reynolds number applies to Newtonian fluids where the ratio of shear stress to shear rate is constant, while in a compost mixt the materials within form a colloidal matrix which is plastically deformed under loads. In this new fluidize bed configuration, shape of the blade is used to impart an upward force to the foam blocks contained within the container, moving these upward relative to the denser, viscoelastic composting organic material, leave a high volume of free air space within the composting materials in surface contact with foam blocks. The resultant upward movement of foam shears the downward flow of the organic mixture increasing surface area to volume ratio. Blade 60 is also shaped so that when utilized it imparts a substantially upward force to the foam blocks contained within container 10 into the downward flowing composting organic material, shearing and mixing the compost within container 10.

[0023] Alternatively, or in combination with the blade, an oscillating or vibrational field can supply energy to the wet viscous composting material to induce flow between and amongst the foam chunks and blocks, optimizing exposed surface area and low resistance flow channels in the process. [0024] Accordingly, mixing blade 60 is designed to achieve preferred viscous flows within the pre-compost solution without compacting the pre-compost mixture. As shown in FIG. 4, mixing blade 60 is preferably configured in the form of a helix formed about an axis. As known from U.S. Patent 5,948,674, blade 60 may have blade angle a. Less steep blade angles tend to produce proper compost mixture particle and free air distribution where the ratio of shear stress to shear rate is roughly equal to the viscoelastic forces sufficient to hold together particle masse in the 0.1 to 1 .0 cubic inch range. Accordingly, blade angle a is generally set in the range of about 10° to about 30°, and is preferably set in the range of about 13.3° to about 26.6°. In a preferred but non-limiting embodiment, the leading part 62 and edge of blade 60 are flattened and beveled relative to the remainder of blade 60.

[0025] Blade rotation can be coupled to the operation of a concrete or industrial vibrator to maximize through-put flow, or decoupled to optimize or maximize mixing within wet composting masses.

[0026] Further, as shown in FIGS. 8A and 8B, in a preferred embodiment the height of the cross-section of mixing blade 60 preferably flattens gradually from base to tip which moves material from the bottom to the top of the container more effectively. At the base, mixing blade 60 preferably has a cross-sectional width, W_B', of 1 /4" to 1 /2" and a cross-sectional height, Η_Β· of 3/8" to 5/8". At the tip, the mixing blade 60 preferably has a cross-sectional width, W_r of 1 /2" and a cross-sectional height, H_r of 1 /16" to 1/8".

[0027] As can be seen in Figures 1 -5 in a preferred non-limiting embodiment, multiple blades 100 are disposed within container 1 0. In a preferred embodiment as seen in Figs. 3 and 5, three blades 60 are provided.

[0028] Furthermore, in a preferred embodiment as shown in Fig. 5, container 10 includes a funnel shaped base 31 to better collect the composted organic material sized to pass through perforated floor 20 and out an exit port 33 and out through a drainage pipe 35. In this way, throughput compost is collected and removed from the container, utilizing gravity, for either recycling or a downstream secondary composting stage.

[0029] As shown in Fig. 5, composting begins by depositing a quantity of pieces of foam 70. In a preferred non limiting embodiment, the foam is recycled. The pieces of recycled foam 70 have an average diameter of about 1 " to about 3" or more in a preferred non-limiting embodiment. Recycled foam particles 70 may be polystyrene, polyurethane, or other low density space filling plastic systems or the like. The cylinder is filled by volume from 1 /2 to 2/3 of the volume of container 1 0 with foam particles 70. Organic waste 80 is then deposited into container 10 to fill the remainder of container 10, or may be introduced periodically, once a day or several times a day, as the waste is produced or arrives at the composting site. The use of the recycled foam helps insure that air floor 20 does not become clogged with the organic waste 80, and the turning of the auger and/or vibration of the medium moves material down gradient and through the screen of the air floor at the base.

[0030] The 1 " to 3" diameter of foam particles 70 are larger than the perforations within perforated floor 20 and therefore will not pass therethrough.

Furthermore, the blades apply a force which will not break down foam particle 70 and as a result the composting material 80 can be become much moister. The use of the fiber with the foam particles having a substantially greater size than the organic waste particles allows the organic waste 80 to settle, slide, flow or filter down into the spaces between foam particle 70 as a result of the auger rotation and/or vibration, making mixture 74 denser. As the organic waste 80 continues to flow downward, it will eventually fall through the openings in air floor 20 draining the broken down waste therethrough. In effect, organic waste drains once it reaches the appropriate size and decomposition level. As a result, rather than being handled as a batch as in the prior art, organic waste 80 may be continually added to the top as the older organic waste settles to the bottom and drains. Furthermore, over time, the lighter larger foam particles 70 will "float" to the top with the assistance of the auger blades 60.

[0031] To promote the microbial reactions necessary to decompose matter into compost, surface area should be maximized. The individual pieces of organic waste 80 should preferably be sized to achieve a surface area to volume ratio of from approximately 4 to 1 to approximately 10 to 1 square inches to cubic inches before depositing within container 10. Optimal moisture content of the initial mixture of organic waste and recycled foam between 45% and 60% and therefore the ratio of organic waste to recycled foam should be selected within the ranges discussed above to achieve a moisture content of the mixture within this range. The addition of some fraction of composted organics from the base of the vessel effectively re-innoculates the incoming batch with activated microbial colonies to optimize breakdown rates.

[0032] As shown in FIG. 5, the organic waste 70 and recycled foam 72 are mixed together within container 10 by the use of specially designed mixing blade 60. Removable top 1 2 is replaced on container 10 to seal container 10. The motors 50 are then activated to drive mixing blade 60 through the organic waste 80 and the recycled foam 70 together, resulting in a compost mixture 74.

[0033] As noted above, mixing blade 60 is configured in such a way as to ensure that composting takes place efficiently and rapidly within the compost mixture 74. This is achieved by mixing the organic waste 80 and recycled foam particles 70 together to ensure the proper moisture level and particle distribution within the compost mixture 74, ensuring that the average particle size of organic waste 80 is optimized to provide for effective colonization of decomposing microorganisms (bacterial

communities) on the surface of organic waste 80, and creating air channels 76 between particles of compost mixture 74 as shown in FIG. 7. These air channels 76 support rapid growth of bacterial communities which break down the degradable substratum in a very short time frame by providing oxygen to the bacteria and by transferring heat, carbon dioxide, water vapor and ammonia away from compost mixture 74. Mixing blade 60 achieves this type of optimal mixing without compaction by virtue of its unique design described above. Leachate from the base or other water may be added to keep microbial growth at optimal rates, since the foam blocks are not wetable like standard bulking agents.

[0034] The rate of decomposition is proportional to the surface area of the waste available for the colonization of microorganisms which perform the decomposition as well as its moisture content. Hence, it is desirable to maximize the surface area-to-volume ratio of the organic waste 80. Optimally, the surface area-to- volume ratio of organic waste 80 should approach 10 cm² /cm³, and the particle size of compost mixture 74 is preferably reduced to approximately 0.1 to 1 .0 cubic inches, a size which allows for rapid colonization by microbes in about 4-12 hours. Given the irregular shape of "chunks" of compost mixture 74, this results in a high volume of free air space (approximately 25-40%) in compost mixture 74. Putrescible organics are broken down rapidly, in about 3-6 days. Because the mixing blade 60 of the present invention, together with the vibration supplied by concrete or industrial vibrators are designed to provide effective mixing, more variable and larger particle sizing still allows for high rates of breakdown, since air channel creation by using a slowly rotating blade and vibration which takes advantage of the viscoelastic properties of the compost mixture 74 inducing flow into large, low resistance air channels between the foam.

[0035] As noted above, while compost mixture 74 may have an initial moisture content of 45% to 60%, because the fluidic properties of the viscoelastic compost mixture 74 will move it to flow between the foam blocks, opening up low resistance air flow channels in the process, higher water content will lead to more rapid breakdown without eliminating essential oxygen from actively growing microbes. The viscous flow of composting material does not disrupt large area of microbial films, so breakdown rates continue at high waste-processing capacity in the compost mixture 74.

[0036] Thus, mixing blade 60 by itself or together with concrete or other vibrators is employed to optimally structure optimally sized particles without compacting. This is generally achieved by rotating mixing blade 60 at an angular velocity of about 1 -100 radians/second. More particularly, in a configuration in which container 10 is a standard 5 foot diameter pipe cut in 5 foot length, optimal mixing is achieved between about 10 and 100 revolutions per minute. This yields the desired thickness of the organic mix of about 0.1 to 1 .0 inches and also creates a large volume of air channels 76 within compost mixture 74.

[0037] After the organic waste 80 and foam block are initially sized, mixed and distributed by mixing blade 60, air is circulated through air channels 76 within compost mixture 74 by moving air into container 10 through air inlet port 30 by using a blower 51 , a fan or other suitable means. Air rises through air floor 20 into air channels 76, providing oxygen to the decomposing bacteria adhering to compost mixture 74.

Alternatively, the air flow may be reversed by blowing air into container 1 0 through air exhaust port 40 and allowing it to flow downwards through the air channels 76 in compost mixture 74 thereafter exiting through air inlet port 30. Typically, mixing blade 60 need only be employed to initially mix the organic waste 80 and recycled foam 70 together. However, should condensation occur near the inner walls of the container, mixing blade 60 may be used again to distribute the moisture. Leachate from the base of the container as well as make up water may be used to increase the moister content of the composting organic matter, to optimize microbial activity. Unlike other compost mixes, because of the fluidized bed configuration of hydrophobic foam and wet, viscoelastic organics, higher water content does not inhibit the flow of oxygen.

[0038] Near the top of container 10, air leaves the container via air exhaust port 40, carrying with it the gaseous by-products of the decomposition process: carbon dioxide, water vapor, ammonia and heat. At this point, this exhaust air can be noxious. In composting systems of the past, the exhaust air would be filtered by a separate biofilter or the like to remove the odor and harmful gaseous components.

[0039] Utilizing a series of organic waste composting systems of the present invention, the exhaust air may be reused to enhance further composting in a second container 10, and may be eventually discharged in an odorless, non-toxic state. As shown in FIGs. 5 and 6, a plurality of organic waste composting systems, 100a, 1 00£> and 100c, are connected in series. A first organic waste composting system 100a, identical to container 10 described above, is connected to a blower 51 or other air supply at its air inlet port 30a and performs composting in accordance with the invention. The air exhaust port 40a of the first organic waste composting system 100a is connected by a first air hose 45a to the air inlet port 30£> of a second organic waste composting system 100b. Likewise, the air exhaust port 40£> of the second organic waste composting system 100b is connected by a second air hose 45£> to the air inlet port 30c of a third organic waste composting system 100c. Any desired number of organic waste composting systems 100 may be sequentially connected in this manner. Organic waste composting system 100b may contain a more mature compost than that contained in composting system 100a, and composting system 100c may contain the most mature compost in the system.

[0040] By exhausting the waste heat, gases and humidity from first composting system 100a to second composting system 100 b containing a more mature compost, the waste heat, humidity and unused oxygen of first composting system 100a are incorporated into the total efficiency of the system because the same air stream moves through composting vessels in series. High carbon dioxide concentrations from the initial composting system 100a also pass through any remaining vessels and cause downstream growth of fungal mycelia as a result of the carbon dioxide enrichment in the downstage composts. Similarly, the waste products of the more mature compost in composting system 100£> are input to a further downstream compost contained within composting system 100c, composting system 100c being a more mature compost then that found in composting systems 1 00£> and 100a. Through the use of these waste products, the downstream composting systems contained within the downstream containers act as biofilters. As a fully mature compost is removed from the system, the preceding containers within the system are each moved up one "stage" within the system so that in the example of FIG. 6, composting system 100c would be the final stage, compost contained within composting system 1 00£> would be an intermediate earlier stage acting as a biofilter, and a less mature or first-stage compost system 100a would exhaust its gaseous by-products into the inlet port 30b of composting system 1006.

[0041] It should be noted that this system of composing different stages of compost in series may also be accomplished in a single container by using several layers of compost, each layer of which has achieved a different stage of composting. For example, in a container of sufficient volume to hold three layers of compost, each having reached a different stage of decay, the most mature compost could be deposited into the bottom of the container, the intermediate compost could be placed thereon, and the youngest compost could be placed on top. Each layer could be mixed using the blade of the present invention when deposited into the container without disturbing the layer below. In this embodiment, the air flow through the container is preferably reversed; that is, air is blown into the container 10 through air exhaust port 40 and flows downward through the compost mixture 74 exiting the container 10 through air inlet port 30. With the flow of the air reversed in this manner, the lower, more mature layers of compost would act as a biofilter in much the same way that the composting systems 100 holding the more mature compost described above act as biofilters.

[0042] It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the article set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

[0043] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

CLAIMS What is claimed:

1 . A method for composting organic waste comprising:

depositing foam particles in a container, the container having an inlet port, an exhaust port and a waste impermeable, but air permeable air floor, the inlet port and exhaust port being disposed so as to allow gas to travel into the container through the inlet port, through the air floor and out of the container through the exhaust port; the foam filling the container from 1 /3 to 2/3 by volume;

depositing organic waste in the container to fill the container; and mixing the organic waste and the foam particles.

2. The method of claim 1 , wherein the foam particles are formed from recycled foam.

3. The method of claim 1 , wherein mixing the organic waste and the foam particles is done with a blade dimensioned so that the shear forces produced by the blade when rotated within organic waste and foam particles are at least equal to the viscoelastic forces for the organic waste and less than a force necessary to break down the foam particles.

4. The method of claim 3, wherein the blade is rotated at an angular velocity of about 1 to about 100 radians per second.

5. A system for composting for organic waste comprising: a container having an inlet port, an exhaust port and a waste impermeable, but air permeable air floor, the inlet port and exhaust port being disposed so as to allow gas to travel into the container through the inlet port, through the air floor and out of the container through the exhaust port; foam particles filling the container from 1 /3 to 2/3 by volume; and a blade dimensioned so that the shear forces produced by the blade when rotated within the precompost organic waste are equal to the viscoelastic forces between the particles forming the precompost organic waste and provide a force less than a force necessary to break down the foam particles.

6. The organic composter of claim 5, wherein the blade is helical.

7. The system of claim 5, wherein said air flow includes a screen which is permeable to gases and substantially impermeable to the organic waste.

8. An organic waste composting system comprising: a first organic waste composter system having a first container; foam particles disposed within the container, filling the container from 1/3 to 2/3 by volume; a first inlet port disposed in said first container, a first exhaust port disposed in said first container, and a first waste impermeable, but gas permeable air floor, the first inlet port and first exhaust port being disposed with said container to allow gases to travel into said first container through the first inlet port, through the first air floor through the foam particles, and out of said first container through the exhaust port; and at least a second organic waste composting system having a second container, foam particles disposed within the container, filling the container from 1 /3 to 2/3 by volume, a second inlet port disposed in said second container, a second exhaust port disposed in said second container; and a second waste impermeable but gas permeable air floor; the second inlet port and second exhaust port being disposed within said second container to allow gases to travel into said second container through the second inlet port, through the second air floor through said foam particles and out of said second container through the second exhaust port, said second inlet port being in fluid communication with said first exhaust port; said first and said at least second containers each further including a gas impermeable floor, gas impermeable sides and a gas impermeable top; said gas impermeable tops being selectively removable from said first and said at least second containers.

9. The organic waste composting system of claim 8, wherein at least one of the first container and second container has a helical blade dimensioned so that the shear forces produced by the blade when rotated within the precompost organic waste are at least equal to the viscoelastic forces between the particles forming the precompost organic waste, but are less than the force necesasry to break down a foam particle.

10. The organic waste composter of claim 9, wherein the blade has a blade angle of from about 1 0⁵ to about 30⁵.