Controlled release biodegradable coatings for seeds and fertilizers
By using biodegradable PHA coating materials, the instability problem of existing controlled release fertilizer technology under environmental changes is solved, environmentally friendly and controllable nutrient release is achieved, and crop yield is improved.
Patent Information
- Application Number
- JP2024191336
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2019-05-24
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-12
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The existing technology for controlling the release of fertilizers is greatly affected by changes in environmental conditions, and the petroleum-based coating is not environmentally friendly and lasting, making it difficult to provide timely nutrient supply under environmentally friendly and controllable conditions.
Biodegradable polyhydroxyalkanoate (PHA) is used as the coating material, combined with a variety of degradable polymers to form a double or multi-layer coating to control the slow release of nutrients under specific environmental conditions.
Under environmentally friendly conditions, the controllable release of nutrients according to plant growth needs is achieved, which avoids improper nutrient supply and increases crop yield.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present disclosure relates to biodegradable polymeric compositions. More particularly, the present disclosure relates to controlled release biodegradable coatings for seeds and fertilizers. [Background technology]
[0002] Plants take up nutrients at different rates based on environmental conditions, but the most important period for nutrient uptake is during the early development of the plant, when nutrients must be sufficient. However, excessive nitrogen uptake can overstimulate vegetative growth and delay crop maturity. Thus, the timing of nutrient uptake is important to maximize crop yield.
[0003] To address these challenges, controlled release fertilizers (CRFs) have been produced, where the fertilizer is encapsulated in a petroleum-based polymer coating that slowly releases the fertilizer into the soil; thus, nutrients can be delivered at a pace more suited to the metabolic needs of the plant. However, changes in temperature, moisture, or soil biological activity can unpredictably alter this rate, negatively impacting crop yields by providing the wrong amount of nutrients at the wrong time. Thus, to date, commercial application of CRFs has been limited by a lack of data on the kinetics of release in various environmental conditions. Furthermore, the petroleum-based coating applied to the fertilizer is not environmentally friendly, and may persist in the environment for years after fertilization.
[0004] Thus, it would be desirable to provide new controlled release fertilizer formulations that are not harmful to the environment and that do not persist after the growing season, and that have more predictable and controllable fertilizer release rates. Summary of the Invention
[0005] These and other needs are met by a granular composition for agricultural use according to the present disclosure. According to one embodiment, the granular composition is comprised of a plurality of granulates having a first biodegradable coating layer applied to the granulates. The granulates are in turn comprised of a material selected from the group consisting of seeds, fertilizers, and pesticides. The first biodegradable coating is comprised of polyhydroxyalkanoates, and the polyhydroxyalkanoates contain from about 70 mole percent to about 99 mole percent of monomeric residues of hydroxybutyrate and from about 1 mole percent to about 30 mole percent of monomeric residues of different polyhydroxyalkanoates having 5 to 22 carbon atoms.
[0006] In some cases, the polyhydroxyalkanoate is preferably composed of about 70 mole percent to about 99 mole percent monomer residues of 3-hydroxybutyrate, and in some cases, the polyhydroxyalkanoate is preferably composed of about 1 mole percent to about 30 mole percent monomer residues of 3-hydroxyhexanoate.
[0007] In certain embodiments, the granules of the composition are preferably comprised of seeds. In other embodiments, the granules of the composition are preferably comprised of fertilizers, more preferably urea-based fertilizers. In further embodiments, the granules of the composition are preferably comprised of pest control.
[0008] In certain embodiments, the first biodegradable coating layer preferably comprises a polyhydroxyalkanoate having a weight average molecular weight of about 50,000 to about 2.5 million Daltons.
[0009] In certain embodiments, the particulates preferably have an average particle size of about 1 mm to about 25 mm before coating.
[0010] In certain embodiments, the polyhydroxyalkanoates may also contain monomeric residues of 3-hydroxyvalerate, 4-hydroxyvalerate, and / or 5-hydroxyvalerate.
[0011] Further, in some cases, the polyhydroxyalkanoate is composed of monomeric residues of three or more hydroxyalkanoates, preferably each having from 5 to 22 carbon atoms.
[0012] In certain embodiments, the first biodegradable coating layer also comprises at least one polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polybutylene adipate (butylene terephthalate) copolymers, polyglycolic acid, polymaleic acid, and mixtures thereof.
[0013] In certain embodiments, the first biodegradable coating layer also comprises from about 5 weight percent to about 95 weight percent polycaprolactone.
[0014] In a preferred embodiment, the first biodegradable coating layer is composed of less than 1 weight percent polyurethane, and more preferably the first biodegradable coating layer is completely free of polyurethane.
[0015] In certain embodiments, the first biodegradable coating layer is composed of about 50 weight percent to about 95 weight percent polyhydroxyalkanoate, and about 5 weight percent to about 50 weight percent of a biodegradable polymer other than polyhydroxyalkanoate.
[0016] Additionally, at least the first biodegradable coating layer begins to dissolve after about three to about twenty-one days of exposure to environmental conditions at a temperature of about -5 to about 60° C. and a pH of about 2 to 9. More preferably, at least 10 weight percent of the first biodegradable coating layer is dissolved after about three to about twenty-one days of exposure to environmental conditions at a temperature of about 60 to about 100° F. (about 16 to about 38° C.).
[0017] In certain embodiments, the granular composition can also include a second biodegradable coating layer applied to the first biodegradable coating layer, which is preferably composed of at least a polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, meso-lactide and polybutylene adipate (terephthalate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polyglycolic acid, polymaleic acid, and mixtures thereof.
[0018] In a further aspect, the present disclosure provides a method for controlled release of granular material. According to one embodiment, the method includes the initial step of preparing a granular composition comprised of a plurality of granules having a first biodegradable coating applied to the granules. The granules are in turn comprised of a material selected from the group consisting of seeds, fertilizers and pest control agents. The biodegradable coating is comprised of polyhydroxyalkanoates, and the polyhydroxyalkanoates are comprised of from about 70 mole percent to about 10 mole percent of the polyhydroxyalkanoates. It contains about 99 mole percent monomeric residues of a hydroxybutyrate, and about 1 mole percent to about 30 mole percent monomeric residues of a different hydroxyalkanoate having from 5 to 22 carbon atoms.
[0019] In a second step, the granular composition is spread onto the soil of the plot.
[0020] At least the polyhydroxyalkanoate in the first biodegradable coating layer is then dissolved by exposing the soil of the plot and the granular composition dispersed therein to moisture. Upon decomposition of the polyhydroxyalkanoate, the granular material is released into the soil.
[0021] In some cases, it is preferred that the polyhydroxyalkanoate be composed of from about 70 mole percent to about 99 mole percent monomer residues of 3-hydroxybutyrate, and in some cases it is preferred that the polyhydroxyalkanoate be composed of from about 1 mole percent to about 30 mole percent monomer residues of 3-hydroxyhexanoate.
[0022] In certain embodiments of this method, the granules of the composition preferably comprise seeds. In other embodiments of this method, the granules of the composition preferably comprise fertilizers, more preferably urea-based fertilizers. In further embodiments, the granules of the composition preferably comprise pest control.
[0023] In certain embodiments of this method, the polyhydroxyalkanoate may also contain monomeric residues of 3-hydroxyvalerate, 4-hydroxyvalerate, and / or 5-hydroxyvalerate.
[0024] Moreover, in some cases it is preferred that the polyhydroxyalkanoate be composed of monomeric residues of three or more hydroxyalkanoates, each having from 5 to 22 carbon atoms.
[0025] In certain aspects of this method, the first biodegradable coating layer also comprises at least a polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polybutylene adipate (butylene terephthalate) copolymers, polyglycolic acid, polymaleic acid, and mixtures thereof.
[0026] In certain aspects of this method, the first biodegradable coating layer also includes about 5 weight percent to about 95 weight percent polycaprolactone.
[0027] In a preferred embodiment of this method, the first biodegradable coating layer comprises less than 1 weight percent polyurethane, and more preferably the first biodegradable coating layer is completely free of polyurethane.
[0028] In certain aspects of this method, the first biodegradable coating layer is comprised of about 50 weight percent to about 95 weight percent polyhydroxyalkanoate and about 5 weight percent to about 50 weight percent of a biodegradable polymer other than polyhydroxyalkanoate.
[0029] Furthermore, at least the first biodegradable coating layer begins to dissolve after exposure to environmental conditions of temperatures of about -5 to about 60°C and pH of about 2 to 9 for about 3 to about 21 days. Preferably, at least 10 weight percent of the first biodegradable coating layer is dissolved after exposure to environmental conditions at temperatures of from 60 to about 100° F. (about 16 to about 38° C.) for about 3 to about 21 days.
[0030] In certain aspects of this method, the granular composition can also include a second biodegradable coating layer applied to the first biodegradable coating layer, which is preferably composed of at least a polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, meso-lactide, polybutylene adipate (terephthalate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polybutylene adipate (butylene terephthalate) copolymers, polyglycolic acid, polymaleic acid, and mixtures thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] granular composition In accordance with the present disclosure, there is provided a granular composition for agricultural use, the granular composition comprising a plurality of granules having at least a first biodegradable coating applied to the granules.
[0032] Granules can be composed of various materials that are agriculturally useful substances.Generally, granules can be composed of materials selected from the group consisting of seeds, fertilizers and pesticides.It may be preferred that the granules of the composition are composed of seeds.Examples of seeds that can be used in the granule composition include grass seeds, fruit and nut seeds, crop seeds and vegetable seeds.
[0033] In another embodiment, the granules of the composition are preferably comprised of a fertilizer. Fertilizers that may be provided as coated granular compositions according to the present disclosure include nitrogen-, phosphorus- and potassium-based fertilizers. In a particularly preferred embodiment, the fertilizer may be a urea-based fertilizer.
[0034] In still other cases, the granules may be composed of pesticides. In general, any solid pesticide material may be provided as a coated granular composition according to the present disclosure, including inorganic pesticides, organic pesticides, and biological pesticides. Examples of such pesticides include, but are not limited to, pesticides including ammonium nitrate, potassium chloride, sodium phosphate, calcium sulfate, chlorpyrifos, metribuzin, chlorimuron ethyl, atrazine, S-metolachlor, cyanazine, viral biological pesticides, and bacterial biological pesticides.
[0035] The size of the granules will vary depending on the nature of the granule material. Generally, the granules will have an average particle size of about 1 mm to about 25 mm before coating. For seeds, more specifically, the granules can preferably have an average particle size of about 1 mm to about 25 mm before coating. For fertilizers, the granules can preferably have an average particle size of about 1 mm to about 8.5 mm before coating. For pesticides, the granules can preferably have an average particle size of about 1 mm to about 10 mm before coating.
[0036] In accordance with the present disclosure, a first biodegradable coating is applied to the particulates that includes polyhydroxyalkanoates (PHAs) that contain from about 70 mole percent to about 99 mole percent monomeric residues of hydroxybutyrate and from about 1 mole percent to about 30 mole percent monomeric residues of a different hydroxyalkanoate having from 5 to 22 carbon atoms.
[0037] In more preferred embodiments, the polyhydroxyalkanoate is preferably comprised of from about 70 mole percent to about 99 mole percent monomer residues of 3-hydroxybutyrate, and in some cases, the polyhydroxyalkanoate is preferably comprised of from about 1 mole percent to about 30 mole percent monomer residues of 3-hydroxyhexanoate.
[0038] In some aspects of this method, the polyhydroxyalkanoate can be composed of monomeric residues of three or more hydroxyalkanoates, each having from 5 to 22 carbon atoms, for example, in some cases the polyhydroxyalkanoate can be composed of monomeric residues of 3-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate.
[0039] In other cases, the polyhydroxyalkanoate can be composed of at least three monomer residues selected from the group consisting of monomer residues of 3-hydroxybutyrate, 4-hydroxybutyrate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, and 3-hydroxydecanoate.
[0040] In certain embodiments, it is preferred that the first biodegradable coating comprises a polyhydroxyalkanoate having a weight average molecular weight of about 50,000 to about 2.5 million daltons.
[0041] In certain embodiments, the polyhydroxyalkanoate may also contain monomeric residues of 3-hydroxyvalerate, 4-hydroxyvalerate, and / or 5-hydroxyvalerate.
[0042] In some cases, the first biodegradable coating layer may include one or more additional polymers. For example, the first biodegradable coating layer may also include at least one polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymer, meso-lactide, polybutylene adipate (terephthalate) copolymer, polyvinyl alcohol, polyvinyl acetate, cellulose ester, polysaccharide, polyglycolic acid, polymaleic acid, and mixtures thereof. In a more preferred embodiment, the first biodegradable coating layer may include about 5 weight percent to about 95 weight percent polycaprolactone.
[0043] In some embodiments, the granular composition may also include a second biodegradable coating layer applied to the first biodegradable coating layer, preferably comprising at least one polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polybutylene adipate (butylene terephthalate) copolymers, polyglycolic acid, polymaleic acid, and mixtures thereof.
[0044] In some cases, the granular composition can include additional coating layers in addition to the first and second biodegradable coating layers. These optional additional coating layers can be applied below the first coating layer, between the first and second coating layers, and / or above the second coating layer.
[0045] In certain aspects of this method, the first biodegradable coating layer is about 50 weight percent to about 95 weight percent polyhydroxyalkanoate, and about 5 weight percent to about 50 weight percent of a biodegradable polymer other than polyhydroxyalkanoate. Suitable examples of compositions for the first biodegradable coating layer include: [Table 1]
[0046] In some embodiments, the biodegradable coating may contain relatively small amounts of other additives, from 0.3 to 10% by weight, such as polyvinyl acetate, clay, calcium, talc, starch, pentaerythritol, and sulfur.
[0047] As used herein, the term "biodegradable" describes a material that can be decomposed or broken down by microorganisms or organisms in the soil. Generally, it is preferred that at least about 50 percent by weight of the coating be made up of materials that are biodegradable. More preferably, 100 percent of the materials that make up the coating are biodegradable.
[0048] It is also preferred that the biodegradable coating contain less than about 1.0 weight percent polyurethane, and more preferably, the biodegradable coating is completely free of polyurethane.
[0049] Preparation of granular composition In another aspect, the disclosure provides a method of making a coated granular composition. In one embodiment, the method includes mixing a polyhydroxyalkanoate, and optionally other polymers and / or solvents, at a temperature of about 25° C. to about 170° C. to provide a first coating mixture. The first coating mixture is then applied to an exterior surface of a plurality of granules. The method also includes solidifying the coating mixture to create a first biodegradable coating on the exterior surface of the plurality of granules. The granules coated according to this method are comprised of a material selected from the group consisting of seeds, fertilizers, and pest control agents.
[0050] Optionally, a second coating mixture can be prepared in a similar manner and applied to the first biodegradable coating to provide a second biodegradable coating, and any other layers can be applied in the same manner.
[0051] In certain aspects of this method, the granules of the composition preferably comprise seeds. In other aspects of this method, the granules of the composition preferably comprise fertilizer, more preferably urea-based fertilizer.
[0052] Uses of the granular composition The coated granular compositions of the present disclosure are suitable for use for agricultural purposes. In particular, the granular compositions of the present disclosure can be used to provide a controlled release method for granular material.
[0053] According to this method, a coated granular composition is provided as discussed above, where again the granular material may be comprised of a material selected from the group consisting of seeds, fertilizers and pesticides.
[0054] The granular composition is spread over the plot of soil to be treated with the composition. The application rate can vary depending on the nature of the granule being applied. For coated fertilizer granules, the granular composition can be spread over the soil at a rate of about 10 to 50 pounds per acre. For coated pesticide granules, the granular composition can be spread over the soil at a rate of about 1 to 10 pounds per acre.
[0055] Once applied to the soil, the soil patch is exposed to moisture in the form of rain, irrigation and / or ambient water vapor, and as a result, the granules of the coated granular composition are likewise exposed to moisture.
[0056] This exposure to moisture and small globules naturally present in the environment causes at least the polyhydroxyalkanoates in the biodegradable coating to begin to undergo hydrolytic degradation. Thus, at least the polyhydroxyalkanoates gradually dissolve into smaller oligomers and monomers. In some cases, other polymers present in the biodegradable coating may also degrade hydrolytically.
[0057] As this degradation proceeds, lower molecular weight degradation products may dissolve in water or otherwise escape from the granules, creating gaps in the biodegradable coating and exposing portions of the granule material beneath the coating that are then released into the soil via gaps in the biodegradable coating.
[0058] As the particulates are released through gaps or openings in the coating, the rate of release of the particulate material is largely determined by the rate of decomposition of the polyhydroxyalkanoate when exposed to environmental moisture. As a result, the rate of decomposition can be affected by factors such as the particular polyhydroxyalkanoate used in the coating (such as monomeric residues of 3-hydroxybutyrate, monomeric residues of 4-hydroxybutyrate, monomeric residues of 3-hydroxyhexanoate, and those having up to 22 carbon atoms) and the weight average molecular weight of the polyhydroxyalkanoate.
[0059] As a result, advantageously, one skilled in the art can effectively control the release rate of particulate materials (seeds, fertilizers, pesticides, etc.) by selecting the appropriate type and amount of polyhydroxyalkanoates for the biodegradable coating.
[0060] In certain embodiments of this method, at least the first biodegradable coating layer begins to dissolve after about three to about twenty-one days of exposure to environmental conditions at a temperature of about −5 to about 60° C. and a pH of about 2 to 9. More preferably, at least about 10 weight percent of the first biodegradable coating layer is dissolved after about three to about twenty-one days of exposure to environmental conditions at a temperature of about 60 to about 100° F. (about 16 to about 38° C.).
[0061] The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are intended to be illustrative and not restrictive of the principles of the invention. The invention has been chosen and described in order to provide a best explanation of the principles and practical application thereof, and to thereby enable those skilled in the art to utilize the invention in its various embodiments and with various modifications as appropriate for the particular use intended, All such modifications and variations are within the scope of the invention as defined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.
Claims
1. A granular composition for agricultural use comprising a plurality of granules having at least a first biodegradable coating layer applied to the granules, the granules comprising: the particulates comprise a material selected from the group consisting of seeds, fertilizers, and pesticides, and the polyhydroxyalkanoate comprises from about 70 mole percent to about 90 mole percent monomer residues of hydroxybutyrate, and from about 1 mole percent to about 30 mole percent monomer residues of a different hydroxyalkanoate having from 5 to 22 carbon atoms; The granular composition.
2. 2. The granular composition of claim 1, wherein the polyhydroxyalkanoate comprises from about 70 mole percent to about 99 mole percent monomer residues of 3-hydroxybutyrate.
3. 2. The granular composition of claim 1, wherein the polyhydroxyalkanoate comprises from about 1 mole percent to about 30 mole percent monomer residues of 3-hydroxyhexanoate.
4. 2. The granular composition of claim 1, wherein the granules comprise seeds.
5. 2. The granular composition of claim 1, wherein the granule comprises a fertilizer.
6. 2. The granular composition of claim 1, wherein the granule comprises a pesticide.
7. 2. The granular composition of claim 1, wherein the first biodegradable coating layer comprises a polyhydroxyalkanoate having a weight average molecular weight of about 50,000 to about 2.5 million daltons.
8. 2. The granular composition of claim 1, wherein the polyhydroxyalkanoate further comprises monomeric residues of 3-hydroxyvalerate, 4-hydroxyvalerate and / or 5-hydroxyvalerate.
9. 2. The granular composition of claim 1, wherein the polyhydroxyalkanoate comprises monomeric residues of three or more hydroxyalkanoates, each having from 5 to 22 carbon atoms.
10. 2. The granular composition of claim 1, wherein the granules have an average particle size before coating of from about 1 mm to about 25 mm.
11. 2. The granular composition of claim 1, wherein the first biodegradable coating layer further comprises at least one polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polybutylene adipate (butylene terephthalate) copolymers, polyglycolic acid, polymaleic acid, and mixtures thereof.
12. 10. The granular composition of claim 1, wherein the first biodegradable coating layer further comprises about 5 weight percent to about 95 weight percent polycaprolactone.
13. 10. The granular composition of claim 1, wherein the first biodegradable coating layer comprises less than 1 weight percent polyurethane.
14. 2. The granular composition of claim 1, wherein the first biodegradable coating layer comprises from about 50 weight percent to about 95 weight percent polyhydroxyalkanoate and from about 5 weight percent to about 50 weight percent of a biodegradable polymer other than polyhydroxyalkanoate, and wherein at least the first biodegradable coating layer begins to dissolve after exposure to environmental conditions of temperatures from -5 to 60°C and a pH of about 2 to 9 for from about 3 days to about 21 days.
15. 2. The granular composition of claim 1, further comprising a second biodegradable coating layer applied to the first biodegradable coating layer, the second biodegradable coating layer comprising at least a polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, meso-lactide, polybutylene adipate (terephthalate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polyglycolic acid, polymaleic acid, and mixtures thereof.
16. 1. A method for controlled release of a particulate material comprising: providing a granular composition comprising a plurality of granules having a first biodegradable coating layer applied to the granules, the granules comprising a material selected from the group consisting of seeds, fertilizers and pest control agents, and the first biodegradable coating layer comprising a polyhydroxyalkanoate, the polyhydroxyalkanoate comprising from about 70 weight percent to about 99 mole percent monomer residues of hydroxybutyrate, and from about 1 mole percent to about 30 mole percent monomer residues of a different hydroxyalkanoate having from 5 to 22 carbon atoms; applying the granular composition to the soil of the plot; exposing the soil of the parcel, and the granular composition dispersed therein, to moisture whereby at least the polyhydroxyalkanoate in the first biodegradable coating layer dissolves; wherein upon decomposition of the polyhydroxyalkanoate, particulate matter is released into the soil. The method.
17. The method of claim 12, wherein the polyhydroxyalkanoate comprises from about 70 mole percent to about 99 mole percent monomer residues of 3-hydroxybutyrate.
18. The method of claim 12, wherein the polyhydroxyalkanoate comprises from about 1 mole percent to about 30 mole percent monomer residues of 3-hydroxyhexanoate.
19. 13. The method of claim 12, wherein the particulate material comprises seeds.
20. 13. The granular composition of claim 12, wherein the granule comprises a fertilizer.
21. 13. The granular composition of claim 12, wherein the granule comprises a pesticide.
22. The method of claim 12, wherein the polyhydroxyalkanoate further comprises monomeric residues of 3-hydroxyvalerate, 4-hydroxyvalerate and / or 5-hydroxyvalerate.
23. 2. The granular composition of claim 1, wherein the polyhydroxyalkanoate comprises monomeric residues of three or more hydroxyalkanoates, each having from 5 to 22 carbon atoms.
24. The first biodegradable coating layer is made of polycaprolactone, polylactic acid, polybutylene sulfide, 13. The method of claim 12, further comprising at least one polymer selected from the group consisting of polyvinyl acetate, polybutylene succinate (adipate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polybutylene adipate (butylene terephthalate) copolymers, polyglycolic acid, polymaleic acid, and mixtures thereof.
25. 13. The method of claim 12, wherein the first biodegradable coating layer further comprises about 5 weight percent to about 95 weight percent polycaprolactone.
26. 13. The method of claim 12, wherein the first biodegradable coating layer comprises less than 1 weight percent polyurethane.
27. 13. The method of claim 12, wherein the first biodegradable coating layer comprises about 50 weight percent to about 95 weight percent polyhydroxyalkanoate and about 5 weight percent to about 50 weight percent of a biodegradable polymer other than polyhydroxyalkanoate, and wherein at least the first biodegradable coating layer begins to dissolve after exposure to environmental conditions of a temperature of -5 to 60°C and a pH of about 2 to 9 for about 3 days to about 21 days.
28. 13. The method of claim 12, wherein the granular composition further comprises a second biodegradable coating layer applied to the first biodegradable coating layer, the second biodegradable coating layer comprising at least a polymer selected from the group consisting of polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate (adipate) copolymers, meso-lactide, polybutylene adipate (terephthalate) copolymers, polyvinyl alcohol, polyvinyl acetate, cellulose esters, polysaccharides, polyglycolic acid, polymaleic acid, and mixtures thereof.