Vermicast production through conversion of biodegradable organic matter

Abstract

A feed stock-to-vermicast converter, comprising an enclosed flow-through vessel having an upstream inlet for introducing convertible feed stock into a mixed epigeic bed conversion zone adapted to accommodate a population of epigeic vermicast-producing worms, communicating with a vermicast-converted feed stock outlet.

Claims

1. A feed stock-to-vermicast converter, comprising an enclosed flow-through vessel having: an upstream inlet for introducing convertible feed stock into a mixed epigeic bed conversion zone adapted to accommodate a population of epigeic vermicast-producing worms, communicating with a vermicast-converted feed stock outlet.

2. The converter according to claim 1 wherein the mixed epigeic bed zone includes at least one mechanical mixer.

3. The converter according to claim 2 wherein said mixer is adapted to mix fresh feed stock into at least partially converted feed stock in said epigeic bed zone.

4. The converter according to claim 3, wherein said mixer is adapted to mix at least a substantial proportion, and preferably substantially all, incompletely rendered biodegradable feed stock with fresh feedstock, into the epigeic zone.

5. The converter according to claim 4, wherein said vessel is a vertical down-flow converter and said mixer collects said at least partially converted feed stock from immediately downstream of said epigeic bed zone.

6. The converter according to claim 3 wherein the mixer includes a plurality of radially extending paddles arranged in longitudinally spaced apart relation along a rotatable shaft.

7. The converter according to claim 6 comprises a plurality of mixers wherein the respective rotatable shafts are arranged in mutually parallel relation with respective radially extending paddles extending in interdigitated longitudinal offsets between said shafts.

8. The converter according to claim 2 wherein at least one aerator is provided for selective aeration of the mixed epigeic bed zone.

9. The converter according to claim 8 wherein the at least one aerator comprises at least one air inlet located in downstream relation to an up-stream diffuser.

10. The converter according to claim 9 wherein the aerator is a manifold with a plurality of spaced apart air inlets thereon and said diffuser is adapted to facilitate an air flow channel through adjacent downstream flows of materials.

11. The converter according to claim 10 wherein the aerator manifold and diffuser are located below said mixed epigeic zone.

12. The converter according to claim 2 wherein said epigeic zone is supported on a downstream bed comprising converted feed stock, intermediate between said zone and said outlet.

13. The converter according to claim 12 wherein portions of said vessel enclosing said downstream bed comprise mutually down-stream converging hopper side walls terminating at said outlet.

14. The converter according to claim 13 wherein said outlet includes a spiral extractor for extracting downstream vermicast converted feed stock from said converter.

15. The converter according to claim 2, further including process controls for use in monitoring, or controlling or a combination thereof, of one or more of epigeic zone pH, temperature; and moisture levels.

16. The converter according to claim 15 wherein said pH is preferably in the range of at or above 6 to at or below 12.

17. The converter according to claim 15 wherein the pH is less than about 9

18. The converter according to claim 15 wherein said pH is near neutral.

19. The converter according to claim 18 wherein the pH is in the range of from about 6.5 to 7.5.

20. The converter according to claim 16 wherein the moisture is about 40 to about 60%.

21. The converter according to claim 15 wherein the moisture is about 50 to about 55%.

22. The converter according to claim 15 wherein said temperature is at least about 20, and preferably at least about 30 and more preferably about 35 or more degrees.

23. A method for converting a feed stock to vermicast comprising adding convertible feed stock through an upstream inlet into an enclosed flow-through vessel to introduce convertible feed stock into a mixed epigeic bed conversion zone within said vessel, said epigeic bed conversion zone being adapted to accommodate a population of epigeic vermicast-producing worms; mixing, in said epigeic bed zone, said convertible feed stock into at least partially converted feed stock to form a mixed feed stock; converting said mixed feed stock in said epigeic bed zone to vermicast using said worms; extracting vermicast-converted feedstock through a vermicast-converted feed stock outlet from said vessel.

24. The method according to claim 23, wherein said mixing includes mechanical mixing with at least one mechanical mixer in said mixed epigeic bed zone.

25. The method according to claim 24, comprising mixing at least a substantial proportion, and preferably substantially all, incompletely rendered biodegradable feed stock with convertible feedstock, into the epigeic zone.

26. The method according to claim 25 comprising mixing all or at least a substantial proportion of all incompletely rendered biodegradable feed stock.

27. A back mixed enhanced, epigeic-converted vermicast product.

28. The product according to claim 27, wherein said product is a refined substantially intractable-free product.

29. The product according to claim 28 having a vermicast content of greater than 80% by weight.

30. A feed stock to vermicast converter system, comprising an enclosed flow-through vessel adapted for conversion of convertible feed stock to vermicast, and having: an upstream inlet operable for introducing convertible feed stock into said vessel; and, a downstream outlet operable for passing converted vermicast product from said vessel; and, a mixed depth epigeic bed conversion zone intermediate between said inlet and said outlet, operable: to accommodate a feed-rate-stabilized population of epigeic vermicast-producing worms; to receive convertible feed stock at a population-stabilizing feed rate from said inlet into intermixed relation in said mixed depth epigeic bed conversion zone with at least partially converted feed stock therein, for a (flow-through-residence) time sufficient for conversion of a predetermined proportion (at least some or even substantially all) of inlet-received convertible feed stock into vermicast; and to pass through converted product having a corresponding proportion of vermicast, at a feed rate balanced rate, on to said downstream outlet for passage there through from said vessel.

Description

INTRODUCTION TO THE DRAWINGS

[0057] FIG. 1 is a perspective view of a converter according to the present invention;

[0058] FIG. 2 is a top plan view of the converter illustrated in FIG. 1;

[0059] FIG. 3 is an elevated side view of one side of the converter illustrated in FIG. 1;

[0060] FIG. 4 is an elevated end view of the converter illustrated in FIG. 1;

[0061] FIG. 5 is an elevated end view opposite that illustrated in FIG. 4;

[0062] FIG. 6 is a bottom-up view of the converter illustrated in FIG. 1; and

[0063] FIGS. 7a, 7b and 7c are respectively, top plan, elevated side and end views of the mixer arrangement in isolation, which is variously otherwise depicted in FIGS. 1 and 2.

DETAILED DESCRIPTION

[0064] Referring now to the drawings in general there is provided a feed stock-to-vermicast converter 1, comprising an enclosed flow-through vessel 2 having an upstream inlet 3 for introducing convertible feed stock. The vessel 2 is of double-walled construction and adapted to include a closeable cover (not shown) for closing over inlet 3. Vessel 2 is constructed of welded stainless steel with a vee-shaped lower hopper 4. The void between the double walled construction of vessel 2 is insulated with polystyrene insulation to buffer temperature change and reduce the transfer of noise and vibration. The cover is also of stainless steel construction and includes provisions for safety interlocks and for automated feeding. Vessel 2 is supported on levelable feet with rubber pads to further reduce noise and vibration.

[0065] The feed stock material is introduced into a mixed epigeic bed conversion zone 5 adapted to accommodate a population of epigeic vermicast-producing worms. Zone 5 communicates, whether directly or indirectly with a vermicast-converted feed stock outlet 6.

[0066] The converter vessel 2 as illustrated is a vertical down-flow converter and a mixer 7 collects the at least partially converted feed stock from downstream of the epigeic bed zone 5. Provision is made for optionally either an interval or a continuous top feed into a flow-through vessel-enclosed converter 1. Vessel 2 is preferably opaque.

[0067] Detritovourous decompiculture worms, such as the red wiggler Eisenia fetidae, are epigeic (surface dwellers) and together with associated microbes are the ideal vectors for decomposing food waste. Epigeic species habituate natural leaf litter (inhabiting the ectorganic layers: the above soil layer of organic materials) and do not actively redistribute (faunal bioturbation is animal driven mixing of soil) material. According to Jan. 21, 2009, Invasive Worms: Affects on Native Soils, Daniel Halsey, Soil 5125, University of Minnesota, epigeic earthworms dwell within the first inch of the soil litter. Notably in this regard, raised bed vermiculture practices mentioned elsewhere herein are known to use bins to which one inch layers of worm chow are added from time to time to accommodate this ecological habit. U.S. Pat. No. 6,223,687 is a thin layer vermicomposting process that employs unmixed biomass layers of 2 to 8 inch thickness in order to overcome vermicomposting problems associated with beds of two to five feet in depth. Epigeic earthworm speices include Dendrobaena octaedra, Dendrobaena attemsi, Dendrodrilus rubidus, Eiseniella tetraedra, Heliodrilus oculatus, Lumbricus rubellus, Lumbricus castaneus, Lumbricus festivus, Lumbricus friendi, Satchellius mammalis. The mixed epigeic conversion zone according to the present invention is a zone in which mixing is employed to increase the effective depth of the ecotype. To some extent this encourages migrating detritivore populations to be more evenly and actively dispersed through the zone both by physical relocation and by more uniform distribution of food and appealing/sustaining habitat. Back mixing is preferably accomplished as a counter flow (counter current flow within the otherwise predominant flow through in the converter 1), but optionally (not shown) could be carried out as a separated return flow isolated from a downstream location and reintroduced into mixed relation at an upstream epigeic location. Preferably mixing also captures flow through material from at or below the epigeic-zone 5/hopper 6 interface to return worm cocoons and to moderate the availability (concentration) of food in the epigeic zone which may moderate worm population dynamics as well as returning incompletely converted feed stock for vermicast production.

[0068] To this end, the converted mixed epigeic bed zone includes at least one mechanical mixer 7 is adapted to mix fresh feed stock into at least partially converted feed stock in the epigeic bed zone 5 and to mix at least a substantial proportion, and preferably substantially all, incompletely rendered biodegradable feed stock with fresh feedstock, into the epigeic zone 5. The mixer 7 includes a plurality of radially extending paddles 8, (about 12 in length) arranged in longitudinally spaced apart relation along a rotatable shaft 9,9a, and in the illustrated embodiment there are a plurality of such mixers (two) wherein the respective rotatable shafts 9, 9a are arranged about 18 inches apart from extending in interdigitated longitudinal offsets between the shafts 9, 9a.

[0069] Provision is also made or at least one aerator 10 for selective aeration of the mixed epigeic bed zone, and in the illustrated embodiment at least one aerator comprises at least one air inlet located in downstream relation to an up-stream diffuser 12. The aerator 10 is a manifold with a plurality of spaced apart air inlets 11 thereon and the diffuser 12 is adapted to facilitate a longitudinal air flow channel through adjacent downstream flows of materials. The aerator 10 manifold and diffuser 12 are located below the mixed epigeic zone 5. The aeration system is preferably devised to ensure even and constant distribution of air throughout the epigeic zone 5. A compressor 13 driven system inserts air under pressure through a network of stainless steel manifold tubes with bottom (downstream) facing holes and an inverted angle-iron diffuser 12 (arranged with its apex pointing upwards in downward material flow dividing relation) facilitates flow-through of materials into the lower portions of vessel 2.

[0070] Epigeic zone 5 is supported on a downstream bed comprising converted feed stock, intermediate between the zone 5 and the outlet 6wherein portions of the vessel 2 enclosing the downstream bed comprise mutually down-stream converging hopper 4 side walls terminating at the outlet 6.

[0071] The outlet 6 includes a spiral extractor 14 for extracting downstream vermicast converted feed stock from the converter 1.

[0072] Process controls (not shown) are provided for use in the monitoring, or controlling or a combination thereof, of one or more of epigeic zone pH, temperature; and moisture levels. The pH is preferably in the range of at or above 6 to at or below 12. (The pH is preferably less than about 9, more preferably near neutral and especially in the range of from about 6.5 to 7.5). The moisture is about 40 to about 60%, and preferably about 50 to about 55%). The temperature is at least about 20, and preferably at least about 30 and more preferably about 35 or more degrees. The most common worms used in composting systems, redworms (e.g. Eisenia foetida, Eisenia andrei, a feed most rapidly at temperatures of 15-25 C. (59-77 F.). They can survive at 10 C. (50 F.). Temperatures above 30 C. (86 F.) may harm them.

[0073] In operation, the present invention provides a method for converting a feed stock to vermicast comprising adding convertible feed stock through an upstream inlet into an enclosed flow-through vessel. Feedstock is shredded and dewatered through the use of non-proprietary existing equipment. The feedstock is then loaded into the machine where the ideal conditions within allow for the rapid growth of aerobic bacteria which are in turn ingested by the worm (e.g. E. Foetidia) population.

[0074] The epigeic bed conversion zone 5 is adapted to accommodate a population of epigeic vermicast-producing worms; and provision is made for mixing, (in the epigeic bed zone 5), of new convertible feed stock into at least partially converted feed stock to form a mixed feed stock; to facilitate converting the mixed feed stock in the epigeic bed zone to vermicast using the worms. The mixing includes mechanical mixing with at least one mechanical mixer 7 in the mixed epigeic bed zone 5 and mixing at least a proportion of incompletely rendered biodegradable feed stock (exiting the epigeic zone) with newly added convertible feedstock, into the epigeic zone 5. Preferably this entails mixing substantially all or at least a substantial proportion of all such incompletely rendered biodegradable feed stock. To ensure optimal distribution of the biomass, the interior of the vessel 2 is equipped with the aforementioned two shaft 9,9a driven mixers with several pairs of propeller-like paddles 8 that stir the epigeic biomass. The mixer shafts 9, 9a are driven, through reduction gearing, at very low speeds (less than about 20, preferably less than 10 and even more preferably nearer about 2 revolutions per day) and at high torque.

[0075] The conditions and worm population (initially about 25000 red wigglers) are optimized such that a 2 meter long embodiment of the illustrated device 1000 kg of (pre-de-watered) organic waste feedstock per day (a 5 meter long device can process 3500 kg per day). In these embodiments the vessel 2 is about 45 inches wide and has an overall depth of about 45 inches. The operation of these converters is adapted to maintain a stable worm population and to utilize a targeted amount and preferably virtually all of the compostable material that is required for sustaining such stability. More broadly or generally speaking, the system is balanced to balance the addition of fresh, with the back mixing or partially converted, to a degree where a desired vermicast concentration is achieved in the product exiting the outlet. The converted vermicast product migrates towards the bottom of the vessel 2 while the worm population continues to remain localized in the epigeic zone 5. As the vermicast product reaches the bottom of the vessel 2 over time it is harvested from the bottom of the hopper 4 using spiral extractor 14 to auger the casts out of the gated outlet 6 at the bottom of the vessel 2. The harvested castings are then screened, variously packaged and sold.

[0076] The dynamic balance afforded by the present invention addresses problems that can be associated with, on the one hand, undesired worm biomass production (diversion (excess beyond what is required to maintain the stable worm population) of biodegradable material into vermiculture production) and, on the other hand, unintended or at least undesired vermicompost production at the expense of vermicast production, (i.e. the unintentional or indifferent underutilization of biodegradable feed stock in the desired production of vermicastby leaving behind unconverted feed stock material). This systemic balancing thereby permits a general control over the (pref. high and even substantially complete) proportion of biodegradable feed stock to vermicast conversion in the product exiting the converter. The mixing of the new with the old feed stock in the zone buffers the flow of feed stock/product materials residence in the conversion zone and hence the availability of biodegradable material to the epigeic (and hence also migratory or counter current movement) worm population.