WO2023239949A1

WO2023239949A1 - Plant growth media and methods

Info

Publication number: WO2023239949A1
Application number: PCT/US2023/024999
Authority: WO
Inventors: Juan Manuel BRAVO; William Thomas LEWCZYK; Nicholas CESARIO; Maanas MAHESHWARI; Toby COREY
Original assignee: Cruz Foam, Inc.
Priority date: 2022-06-09
Filing date: 2023-06-09
Publication date: 2023-12-14

Abstract

A method of growing plants is described. The method comprising providing a foam including starch. The foam having pores and a density of less than 1 g/cm3. The method further comprising placing a seed or a plant in or on the foam and applying water to the foam. An apparatus for growing plants is described. The apparatus comprising a foam including starch, chitosan mixed with the starch, and cellulose fibers mixed with the chitosan and the starch. The apparatus further comprising a hole or indentation in the foam shaped to receive a seed or a plant.

Description

PLANT GROWTH MEDIA AND METHODS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63/350,731, filed on June 9, 2022, which is hereby incorporated by reference in its entirety.

TECHNIC AL FIELD

[0002] This disclosure relates generally to the field of hydroponic gardening, and in particular but not exclusively, relates to growth media for plants. BACKGROUND INFORM ATION

[0003] Petroleum -based plastic foams are ubiquitous in modern society: they are used for packaging, floatation, etc. However, petroleum-based plastic foams suffer from a number of disadvantages. For example, the ocean has become flooded with petroleum-based foam waste. This is because many petroleum-based foams, such as polystyrene foam, take 500 years or more to decompose. Furthermore, petroleum-based plastic foams are either unrecyclable because of their chemical composition and/or their recovery is not economically feasible because the low material content of the foam.

[0004] Petroleum-based foams tend to be toxic or made by toxic processes. While petroleum-based foams resist decomposition, they may allow toxic compounds to be released into the environment as the foam undergoes decomposition (e.g., degraded foam monomer units). In addition, polystyrene and other petroleum -based foams, may be made using toxic chemicals such as benzene and styrene, which have been shown to be carcinogenic and which may slowly leach out into the environment or onto products in contact with the foam.

[0005] In addition to the problem with petroleum-based materials, grow media used by the grow media industry is dominated with peat. However, despite peatlands storing approximately 30% of the world’s soil, when farmed for agriculture needs, peat changes from being a carbon sink into a greenhouse gas emitter, making it severely environmentally detrimental in the long run. Drained peatlands release approximately 1 .9 gigatons of CO2e annually. This amounts to 5% of global anthropogenic greenhouse gas emissions, a stark lack of correlation considering damaged peatlands make up just 0.3% of global landmass.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of an element are necessarily labeled so as not to clutter the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described.

[0007] FIG. 1 depicts a plant growth medium including foam, in accordance with an embodiment of the disclosure.

[0008] FIG. 2 depicts an example method of manufacturing a plant growth medium, in accordance with an embodiment of the disclosure.

[0009] FIG. 3 depicts a top-down view of a plant growth medium including foam arranged into an array, in accordance with an embodiment of the disclosure.

[0010] FIG. 4 is a cartoon illustration of a foam extrusion system and method that can be used to fabricate a plant growth medium, in accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

[0011] Embodiments described herein variously provide an apparatus or system for plant growth media and/or a method for growing plants and/or forming plant growth media. In the following description numerous specific details are set forth to provide a thorough understanding of the embodiments One skilled in the relevant art will recognize, however, that the techniques described herein may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

[0012] Reference throughout this specification to "‘one embodiment”, “an embodiment”, “one example” or “an example” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment”, “in an embodiment”, “in one example” or “in an example” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0013] As stated above, petroleum-based foams and dominate peat grow media suffer from di sadvantages. The foams described herein solve these problems and are biodegradable, non-toxic, utilize non-tox ic precursors and are produced by environmentally friendly processes. As will be shown, these biodegradable foams represent a significant advance over existing industrial foam technology and peat grow media substrates because these biodegradable foams have similar or better mechanical, chemical, and sustainable agriculture growth properties without the negative environmental impact of conventional petroleum-based foams or peat substrates.

[0014] The biodegradable foams described herein may be used as a growth medium (e.g., in place of conventional peat grow media) for plants (e.g., plants of economic importance such as lettuce, small leafy plants, or other plants). Conventional growth media product could harm the plant or the people consuming the plant. Moreover, once the growth medium has been used, disposal of a non-biodegradable growth medium may cause environmental problems such as soil pollution and soil nutrient degradation.

[0015] FIG. 1 depicts an embodiment of a plant growth medium including foam 101 , plant 103, hole 105, light source 107, and water source 109. Plant 103 is disposed in hole 105 in foam 101. In one embodiment, foam 101 has a density of less than 1 g/cm^J, is porous, and these pores may be formed with a gas (e.g., nitrogen, oxygen, carbon dioxide, or the like) during manufacture. In some embodiments, foam 101 includes chitosan and plant 103 roots are in contact with the chitosan. Plant 103 may be grown from seed and its roots may grow into the pores of the foam.

[0016] In one embodiment, foam 101 may be a composite (e.g., a material made from two or more component materials) including a matrix polymer (e.g., starch, fibers, chitosan, chitin and/or chitosan oligosaccharides). The matrix polymer may include a mixture of one or more polymers, and the polymers listed herein are not mutually exclusive. Multiple polymers can be mixed to form the matrix polymer (e.g., starch, fibers and chitosan may be mixed) In some embodiments, one or more starches (e.g., pea starch or corn starch) may be used to form or otherwise be included in the matrix polymer. In some embodiments a plasticizer (e.g., urea) may be added to the polymer mixture to make foam 101 more pliable so that foam 101 may return to its original shape after being deformed.

[0017] In some embodiments, it was found that certain components may negatively affect germination, growth, or other phonological growth stages of the plant 103 For example, it was found that glycerol, borax, and sorbitol all inhibited germination of the plant 103. Accordingly, in some embodiments, the foam 101 does not include glycerol, borax, or sorbitol. In some embodiments, the plasticizer may correspond to urea, which may not disrupt the phenological growth stages of the plant 103.

[001S] In some embodiments, there is a dispersed phase disposed in the foam, and the matrix polymer imparts stress or strain onto the dispersed phase when under a load. In some embodiments the dispersed phase may not be homogeneously mixed into the matrix polymer. In other words, the dispersed phase may have a nonuniform distribution throughout the matrix polymer For example, cellulose fibers included in the dispersed phase may be dispersed more or less randomly in the matrix polymer. In some embodiments, the dispersed phase may include at least one of chitin, wood flour, hemp, coconut husk, calcium carbonate, talc, cellulose fibers (e.g., recycled cellulose), one or more soil additives to promote growth (e.g., firass, peat moss, cellulose fibers, wood fibers/fluor, rice hulls, coco coir, nitrogen fertilizers, phosphorus fertilizers, potassium fertilizers, worm castings, perlite, vermiculite, compost, manure, bone meal, fish emulsion, Epsom salt, mycorrhizal fungi, seaweed extract, complete or balanced fertilizers, slow-release fertilizers, organic ferti lizers, liquid fertilizers, micronutrient fertilizers, controlled-rel ease fertilizers, other fertilizing soil additives, or combinations thereof), or the like. However, one of ordinary skill in the art will appreciate that other ingredients may be added, and some of the listed ingredients may be removed from, foam 101 in accordance with the teachings of the present disclosure Further, it should be understood that embodiments of the foam 101 depicted in F IG. 1 has been made with all of the aforementioned polymers, dispersed phases, and plasticizers, and that these ingredients may be used alone or in combination. [0019] In some embodiments, the roots of plant 103 may grow to be in contact the dispersed phase and polymer matrix. For example, the roots of plant 103 may be in contact with starch, chitosan chitin, wood flour, hemp, coconut husk, soil additives, calcium carbonate, talc, urea, cellulose fibers, other constituent components of the foam 101, individually or in combination.

[0020] In some embodiments, a composition of the foam 101 may include starch, chitosan, urea, glycerol monostearate, calcium carbonate, talc, cellulose fibers, soil additives, and combinations thereof. In one embodiment, a starch weight percent representative of the starch, by weight, included in the foam 101 is from 80% to 100%. In the same or another embodiment, the foam 101 may optionally include chitosan and the foam 101 has a chitosan weight percent representative of the chitosan, by weight, included in the foam 101 that is greater than 0% and up to 5% In the same or another embodiment, the foam 101 may optionally include urea and the foam 101 has a urea weight percent representative of the urea, by weight, included in the foam 101 that is greater than 0% and up to 5% In the same or another embodiment, the foam 101 may optionally include glycerol monostearate and the foam 101 has a glycerol monostearate weight percent representative of the glycerol monostearate, by weight, included in the foam 101 that is greater than 0% and up to 5%. In the same or another embodiment, the foam 101 may optionally include calcium carbonate and the foam 101 has a calcium carbonate weight percent representative of the calcium carbonate, by weight, included in the foam 101 that is greater than 0% and up to 5%. In the same or another embodiment, the foam 101 may optionally include talc and the foam 101 has a talc weight percent representative of the talc, by weight, included in the foam 101 that is greater than 0% and up to 5%. In the same or another embodiment, the foam 101 may optionally include cellulose fibers and the foam 101 has a cellulose fiber weight percent representative of the cellulose fibers, by weight, included in the foam 101 that is greater than 0% and up to 20%. In the same or another embodiment, the foam 101 may optionally include one or more soil additives and the foam 101 has a soil additive weight percent representative of the one or more soil additives, by weight, included in the foam 101 that is greater than 0% and up to 20%. In some embodiments, one or more of chitosan, urea, glycerol monostearate, calcium carbonate, talc, cellulose fibers, and/or the one or more soil additives may be omitted depending, for example, based on the type of plant or seed to be implanted or otherwise in contact with the foam 101.

[0021] In one embodiment of the foam 101, the cellulose fiber weight percent is greater than each of the soil additive weight percent, the talc weight percent, the calcium carbonate weight percent, the glycerol monostearate weight percent, the urea weight percent, and the chitosan weight percent, but less than the starch weight percent. In the same or another embodiments of the foam 101, the talc weight percent and the calcium carbonate weight percent are approximately (e.g., within 10%) equal to one another. In the same or other embodiments of the foam 101, the glycerol monostearate weight percent is greater than the soil additive weight percent, the talc weight percent, the calcium carbonate weight percent, and the chitosan weight percent but less than the cellulose fiber weight percent and the starch weight percent. In the same or other embodiments of the foam 101, the chitosan weight percent is greater than the calcium carbonate weight percent and the talc weight percent but less than the soil additive weight percent, the cellulose fiber weight percent, the glycerol monostearate weight percent, the urea weight percent, and the starch weight percent. In some embodiments, the cellulose fiber weight, percent, is from 5% to 15% to facilitate water transmission throughout the foam 101.

[0022] In some embodiments, the foam 101 further includes acetic acid and the foam 101 has an acetic acid weight percent of greater than 0% and less than 1% to facilitate the incorporation of chitosan into the foam 101. It is noted that while acetic acid may affect pH, it. may facilitate plant growth for acid-loving plants (e.g, plants that, prefer a soil pH of about 5.5) In the same or other embodiments, the calcium carbonate weight percent of the foam 101 is greater than 0% and less than 3% to improve nucleation and neutralize the acetic acid and starch. In some embodiments, the calcium carbonate weight percent is greater than the acetic acid weight percent to have the foam form an alkaline environment to promote growth of alkaline soil plants (e.g., grow plants that do not thrive in acidic soil).

[0023] It is appreciated that the chitosan, calcium carbonate, talc, and glycerol monostearate may respective provide antimicrobial, nucleation, nucleation, and lubrication benefits. The cellulose fibers and, to a lesser extent, talc allow for better water transmission. Talc, for example, may be less (e.g., 0.5 talc weight percent) to increase pore size of the foam 101 to facilitate plant growth. Urea, when included in the foam 101, corresponds io a fertilizer that also facilitates plant growth.

[0024] In some embodiments, there is more starch than chitosan by weight in foam 101 (e.g., a starch weight percent representative of the starch included in the foam 101 is greater than a chitosan weight percent representative of the chitosan included in the foam 101). In some embodiments, there is more chitosan than starch by weight in foam 101 (e.g., the chitosan weight percent is greater than the starch weight percent). In some embodiments, there is more starch than calcium carbonate by weight in foam 101 (e.g., the starch weight percent is greater than a calcium carbonate weight percent representative of the calcium carbonate included in the foam 101), In some embodiments, there is more starch than talc by weight, in foam 101 (e.g., the starch weight percent is greater than a talc weigh! percent representative of the talc included in the foam 101). In some embodiments, there is more starch than glycerol monostearate or urea by weight in foam 101 (e.g., the starch weight percent is greater than a glycerol monostearate weight percent, representative of the glycerol monostearate included in the foam 101, and a urea weight percent, representative of the urea included in the foam 101 ). In some embodiments, there is more starch than cellulose fibers by weight in foam 101 (e.g. , the starch weight percent is greater than a cellulose fiber weight percent representative of the cellulose fibers included in the foam 101). In some embodiments, there are more cellulose fibers than chitosan by weight in foam 101 (e.g., the cellulose fiber weight percent is greater than the chitosan weight percent). In some embodiments, there is more chitosan than cellulose fibers by weight in foam 101 (e.g., the chitosan weight percent is greater than the cellulose fiber weight percent). In some embodiments, there are more cellulose fibers than calcium carbonate by weight, in foam 101 (e.g., the cellulose fiber weight percent is greater than the calcium carbonate weight percent). In some embodiments, there are more cellulose fibers than plasticizer by weight in foam 101 (e.g., the cellulose fiber weight percent is greater than a plasticizer weight percent representative of the plasticizer included in the foam 101).

[0025] In one embodiment, a dye (e.g., food colorant or other non-toxic dye) may be added to the polymer matrix to color (e.g., red, green, blue, yellow, orange, etc ) the foam 101 . It should be appreciated that this color is not suitable for illustration due to the black and white nature of the drawing.

[0026] Plant 103 may be any plant including plants of commercial interest such as fruit, vegetables, cotton, flaxseed, hemp or the like. It is appreciated that the plant 103 may also be at any phenological development stage (e.g., seed, germination, flowering, ripening, or otherwise).

[0027] Hole 105 may be circular, square, or a slit in the foam 101 depending on the type of plant being inserted into hole 105. Hole 105 may take any shape suitable to hold plant 103 and may be a dent/divot/indentation in the foam 101 . In some embodiments, the hole 105 may extend entirely through the foam 101, which may be supported by an underlying substrate or container. In other embodiments, the hole 105 may only partially extend through the foam 101.

[0028] Light source 107 is positioned so that photons can travel from the light source and hit plant 103 and foam 101. Light source 107 may be one or more light emitting diodes, incandescent bulbs, gas-based light sources, or the like Light source 107 may emit red and blue photons (e.g., light having wavelengths within the electromagnetic spectrum correspond to red and blue) so that plant 103 may grow. In the same or other embodiments, the light source 107 may emit additional or different wavelengths (e.g., white light).

[0029] Water source 109 (e.g., a tube or mister) is positioned so that water is applied to the foam. Water from the water source 109 may saturate the pores of foam 101 to reach the roots of plant 103 which are disposed in foam 101. In some embodiments, the foam 101 is hydrophilic to rapidly absorb water from water source 109.

[0030] FIG. 2 depicts one embodiment of a method of manufacturing a plant growth medium. The blocks in FIG. 2 may appear in any order and even in parallel. Blocks may be added to and removed from the method depicted in FIG. 2. In some embodiments, the method of FIG. 2 may be utilized to form the foam 101 illustrated in FIG. 1.

[0031] Block 201 shows feeding powder or solid ingredients (e.g., starch such as pea starch, corn starch, or the like) into an extruder. In one embodiment, the extruder may be a twin-screw extruder. [0032] Blocks 203 and 205 illustrate feeding ingredients (e.g., to be mixed with the powdered ingredients from block 201). Specifically, block 203 illustrates feeding chitosan and other materials into the extruder. In one embodiment, the other materials may include calcium carbonate, talc, cellulose fibers, or the like, and the foam plant growth medium output from the extruder includes the aforementioned materials. In some embodiments, the chitosan and/or other materials may be fed in a liquid or solution form (e.g., as a solution dissolved in water and/or acetic acid) to provide precise dosage control (e.g., via a liquid dosing system with one or more stages or zones).

[0033] Block 205 depicts feeding acid into the extruder, which may include feeding acetic acid (or other acids such as HC1) mixed with water into the extruder. In some embodiments, a blowing agent such as calcium carbonate may be fed into the extruder to impart gas (e.g., carbon dioxide) into the foam mixture and form bubbles/pores in the foam.

[0034] It is appreciated that blocks 203 and 205 may occur sequentially or in parallel In other words, in some embodiments, a solution of chitosan, acetic acid, water, and the other materials (e.g., at least one of calcium carbonate, talc, cellulose fibers, urea, or the like) may be formed and dosed to mix with the powder or solid ingredients from block 201 . In other embodiments, the liquid dosing system may have multiple zones for precise control of individual ingredients that may be dosed in liquid form sequentially or in parallel.

[0035] Block 207 shows producing the plant growth medium including the chitosan and the starch from the extruder. The plant growth medium is a foam (e.g, the foam 101 illustrated in FIG 1) having a density of less than 1 g/cm^J and pores filled with water vapers and possibly a gas (e.g., nitrogen, carbon dioxide, air, or the like).

[0036] Block 209 illustrates cutting holes into the foam. The holes are shaped to receive a seed or plant. The holes may be circular, rectangular, or any other shape including a slit. The holes may be punched into the foam with a dye punch, pressed into the foam to form an indentation, cut into the foam to form a slit, or the like.

[0037] FIG. 3 depicts a top-down view⁷ of plant growth medium including foam 301 (with hole 305 cut into foam 301) arranged into an array, in accordance with an embodiment of the disclosure. In the depicted embodiment, the foam 301 may be cut into rectangular blocks; however, other shapes may be used (e.g., circular blocks or the like). The array of growth media can be used to grow plants in rows and columns (to maximize the number of plants in a gi ven area). The foam blocks may be disposed in a tray or the like that holds water, such that the foam is continually receiving water and nutrients for the seed or plant disposed in hole 305. It is appreciated that in some embodiments, the plant growth medium illustrated by FIG. 3 may correspond to or otherwise be one possible implementation of the foam 101 illustrated in FIG 1.

[0038] FIG. 4 is a cartoon illustration of a foam extrusion system 400A and method that can be used to fabricate the plant growth medium described herein (e.g., the foam 101 illustrated in FIG. 1 and/or the foam 301 illustrated in FIG. 3), in accordance with an embodiment of the disclosure. In one embodiment, extrusion system 400A is a twin-screw extruder. Extrusion is a continuous process where materials are fed into the extrusion machinery, and structured extrudate (e.g., the extruded material product) is pushed out of the system in desired shapes. An extruder has several parts: feeder, extruder barrel, extruder screws, extruder drive, and die profile. Polymers and other materials may be fed into the extruder with a controlled gravitational feeder. The polymers and other materials are then transported from the start of the system along the screws at an elevated temperature within, and along the length of, the heated barrel. As the polymers are moved along the heated barrel, various additives and blowing agents can be added into the system. This continuous movement allows materials to mix well, forming a uniform viscous mixture, which then goes through a die profile at the end/output of the extruder. Extrusion manufacturing is a high throughput process. Depending on the specific die design (e.g., the shapes and dimensions of the opening that the materials will be pushed out of), the final extrudate can be in various forms, like rolls, tubes, sheets, planks, and other customized shape profiles. Compared to batch processing, extrusion is less expensive, and the extrudates have consistent properties since batch-to- batch variances are eliminated. Extruder system 400 A may be used to produce the plant growth medium described herein.

[0039] Foam extrusion system -400A includes barrel 421, screw 423, drive motor 425, input 427 (e.g., input for the ingredients described elsewhere herein, depicted here as a “hopper”), breaker plate 429, feed pipe 431, die 433, foaming agent(s) in cylinder 435, heating unit 437, puller 439, and dehydrator 441. As illustrated a mixture is provided (in input 427 or other inputs depicted elsewhere) and the mixture may include polymer, acid, dispersed phase, water, other components included in the plant growth media discussed herein (e.g., constituent components of the foam 101 illustrated in FIG

1 and/or the foam 301 illustrated in FIG. 3), or combinations thereof. The polymer may include chitosan or starch In some embodiments, the mixture further includes a plasticizer (preferably nontoxic, e.g , urea) to impart a flexible character and in some embodiments an elastic character, to the porous composite foam. In some embodiments, starch (e.g., pea starch), urea, chitosan, calcium carbonate, talc, fertilizer soil additives and cellulose fibers (e.g., recycled cellulose) may all be fed into extrusion system 400A. As shown, the mixture is inserted into the input 427 of the extrusion system 400 A, where it is fed into barrel 421 . Extrusion system 400A pushes the mixture through one or more barrels 421 — only one barrel 421 is depicted here, but one of skill in the art having the benefit of the present disclosure will appreciate that additional barrels may be coupled in series in accordance with the teachings of the present disclosure — with one or more screws 423 disposed in one or more barrels 421. As shown, the one or more screws 423 are coupled to one or more motors 425 to turn one or more screws 423, which push the mixture forward.

[0040] In the depicted embodiment, a foaming agent (e.g., contained in cylinder 435) is input (via a foaming agent input pipe) into extrusion system 400A to be received by the mixture, and foam the dispersed phase and the polymer matrix into the porous composite foam. In the same or other embodiments, the cylinder 435 may be included within or otherwise representative of a liquid dosing system, adapted to dispense chitosan and/or other materials (e.g,, calcium carbonate, talc, cellulose fibers, urea, or the like), dissolved individually or in combination in water, acetic acid, or other solvent. In some embodiments, the foaming agent includes at least one of sodium bicarbonate, sodium carbonate, carbon dioxide, or the like. In the depicted embodiment, heating unit 437 applies heat (depicted as wavy lines above heating unit 437) proximate to the input of extrusion system 400A.

[0041] Once the foam reaches the end of extrusion system 400A a shape of the porous composite foam is output from die 433. The shape has a fixed cross-sectional profile (e g., circular, square, rectangular, hexagonal, or the like). Puller 439 is positioned to receive the foam from die 433 and keep a constant tension on the foam being removed from the system. Tension may be achieved by having the rollers of puller 439 being engaged by a motor to turn the rollers and pull the foam from die 433 Dehydrator 441 may receive the foam, and dehydrator 441 may heat the foam or pull vacuum (e.g., reduce the pressure) on the foam to remove excess solvent

[0042] In some embodiments, the foam that is continuously extruded may be chopped into blocks (e.g., with chopper or multiple blades cutting the foam at a continuous interval). Blocks of foam may then have holes or slits cut into them that are shaped to receive seeds or plants.

[0043] It is appreciated that in some embodiments, the extrusion processing techniques for fabricating the foam, may utilize lower processing temperatures than typical plastics or polymers. For example, formulations used in various embodiments of the disclosure may have processing temperatures lower than 160°C (e.g., approximately 140°C).

[0044] The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.

[0045] These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.

Claims

CLAIMS What is claimed is:

1. A method of growing plants, the method comprising: providing a foam including starch, the foam having pores, wherein the foam has a density of less than 1 g/cm³; placing a seed or a plant in or on the foam; and applying water to the foam.

2. The method of claim 1, wherein the foam further includes chitosan mixed with the starch.

3. The method of claim 2, wherein the foam further includes glycerol monostearate or urea mixed with the starch and the chitosan.

4. The method of claim 2, wherein the foam further includes at least one of calcium carbonate or talc mixed with the starch and the chitosan.

5. The method of claim 4, wherein the foam includes a chitosan weight percent representative of the chitosan included in the foam, wherein the foam includes a calcium carbonate weight percent representative of the calcium carbonate included in the foam, wherein the foam includes a talc weight percent representative of the talc included in the foam, and wherein the chitosan weight percent is greater than the talc weight percent and the calcium carbonate weight percent.

6. The method of claim 2, wherein the foam further includes at least one of cellulose fibers or one or more soil additives mixed with the starch and the chitosan.

7. The method of claim 6, wherein the foam includes a starch weight percent representative of the starch included in the foam, wherein the foam includes a cellulose fiber weight percent representative of the cellulose fibers included in the foam, wherein the foam includes a soil additive weight percent representative of the one or more soil additive included in the foam, wherein the foam includes a chitosan weight percent representative of the chitosan included in the foam, wherein the cellulose fiber weight percent is greater than the chitosan weight percent and the soil additive weight percent, and wherein the cellulose fiber weight percent is less than the starch weight percent.

8. The method of any of claims 1-7, further comprising forming a hole into the foam prior to placing the seed or the plant in or on the foam, and wherein the seed or the plant is placed into the hole.

9. The method of any of claims 1-8, wherein the water has a pH between 5 and 8.

10. The method of claim 1, wherein the foam further includes at least one of chitosan or cellulose fibers mixed with the starch, wherein after applying the water, one or more roots from the seed or the plant penetrate the pores of the foam, and wherein one or more roots of the seed or the plant are in contact with at least one of the starch, the chitosan, or the cellulose fibers.

11. The method of any of claims 1-10, wherein the water includes nutrients for the seed or the plant, and wherein the pores of the foam are structured to trap the water.

12. The method of any of claims 1-11, further comprising illuminating the seed or the plant with light, the light including red and blue wavelengths.

13. An apparatus for growing plants, comprising: a foam including: starch; chitosan mixed with the starch; and cellulose fibers mixed with the chitosan and the starch, and a hole or indentation in the foam shaped to receive a seed or a plant.

14. The apparatus of claim 13, wherein the foam further comprises one or more soil additives mixed with the starch and the chitosan.

15. The apparatus of claims 13 or 14, wherein the foam further comprises glycerol monostearate or urea mixed with the starch and the chitosan.

16. The apparatus of any of claims 13-15, further comprising one or more trays shaped to receive the foam.

17. The apparatus of any of claims 13-16, further comprising the plant disposed in the hole,

18. The apparatus of claim 17, wherein foam includes pores, and wherein roots of the plant penetrate the pores in the foam and are in contact with the chitosan.

19. The apparatus of any of claims 13-18, further comprising a water source positioned to make the foam wet when water is flowing from the water source.

20. A method of manufacturing a plant growth medium, comprising: feeding starch into an extruder; feeding chitosan into the extruder; feeding acid into the extruder; producing the plant growth medium including the chitosan and the starch from the extruder, wherein the plant grovrth medium is a foam having a density of less than

1 g/crn³, the foam further including pores fill ab le with a gas; and creating one or more holes or indentations in the foam, wherein the one or more holes or indentations are shaped to respectively receive a seed or a plant.

21. The method of claim 20, wherein the chitosan is dissolved in an aqueous solution including the acid before the feeding the chitosan and before the feeding the acid.

22. The method of any of claims 20-21, wherein the extruder includes a twin screw extruder.

23. The method of any of claims 20-22, further comprising feeding glycerol monostearate or urea into the extruder, and wherein the plant growth medium further includes at least one of the glycerol monostearate or the urea.

24. The method of any of claims 20-23, further compri sing feeding calcium carbonate into the extruder, and wherein the plant growth medium further includes the cal cium carb on ate .

25. The method of any of claims 20-2-4, further comprising feeding talc into the extruder, and wherein the plant growth medium includes the talc.

26. The method of any of claims 20-25, further comprising feeding cellulose fibers into the extruder, wherein the plant growth medium includes the cellulose fibers.

27. The method of any of claims 20-26, further comprising feeding soil additive into the extruder, wherein the plant growth medium further includes the soil additive.

28. The method of any of claims 20-27, further comprising feeding water into the extruder.

29. The method of any of claims 20-28, further comprising cutting the plant growth medium into substantially rectangular blocks.

30. A plant growth medium, comprising: a foam having a density of less than 1 g/cm³, the foam including: a starch; chitosan mixed with the starch ; urea mixed with the starch and the chitosan; and cellulose fibers mixed with the starch, the chitosan, and the urea;

31. The plant growth medium of claim 30, further comprising calcium carbonate mixed with the starch, the chitosan, and the urea.

32. The plant growth medium of any of claims 30-31 , further comprising talc mixed with the starch, the chitosan, and the urea.

33. The plant growth medium of any of ciaims 30-32, wherein the foam includes a starch weight precent representative of the starch included in the foam and a chitosan weight percent representative of the chitosan included in the foam, and wherein the starch weight percent is greater than the chitosan weight percent.

34. The plant growth medium of claim 33, wherein the foam includes a urea weight percent representative of the urea included in the foam, and w'herein the starch weight percent is greater than the urea weight percent.

35. The plant growth medium of any of claims 33-34, wherein the foam includes a cellulose fiber weight percentage representative of the cellulose fiber included in the foam, and wherein the starch weight percent is greater than the cellulose fiber weight percent

36. The plant growth medium of any of claims 33-35, wherein the foam further includes a soil additive, wherein the foam includes a soil additive weight percent representative of the soil additive included in the foam, and wherein the starch weight percent is greater than the soil additive weight percent.