WO2017049263A1

WO2017049263A1 - Plasma activated water for an enhanced soil-free horticulture

Info

Publication number: WO2017049263A1
Application number: PCT/US2016/052415
Authority: WO
Inventors: James Ferrell; Tsung-Chan TSAI; Sameer Kalghatgi; Jeffrey S. Louis; Robert L. Gray
Original assignee: EP Technologies LLC
Priority date: 2015-09-18
Filing date: 2016-09-19
Publication date: 2017-03-23

Abstract

The nutrient rich water which is sprayed onto the roots of a plant being grown aeroponics or hydroponics is plasma-activated water generated by a non-thermal plasma.

Description

PLASMA ACTIVATED WATER FOR AN ENHANCED SOIL-FREE HORTICULTURE

Related Applications

[0001] This application claims priority to and the benefits of U.S. Provisional Patent Application Serial No. 62/220,521 filed on September 18, 2015 and entitled "PLASMA ENHANCED SOIL- FREE HORTICULTURE," which is incorporated herein by reference in its entirety.

Background and Summary

[0002] Hydroponics and aeroponics are types of soil-free horticulture in which plants are grown without using soil as a root-encasing medium. In hydroponics, the roots and lower stem of the plant are suspended in a body of nutrient rich feed water. In aeroponics, the roots and lower stem of the plant are suspended in air where they are sprayed with nutrient rich feed water.

[0003] Because of the ability to precisely control the conditions and materials to which the root and shoot systems are treated in both hydroponics and aeroponics, plant growth can be expedited. Additionally, this precise control of conditions and materials makes the invasion of pests, unwanted plants (weeds), funguses and diseases easier to eliminate. Moreover, because all of the plant is treated to air in aeroponics, the entire plant has increased availability to atmospheric oxygen and nitrogen, which not only promotes seed germination and faster plant growth, but can further reduce the incidence of disease.

[0004] In accordance with this invention, the nutrient rich feed water with which the roots of a plant being grown by hydroponics or aeroponics are treated is feed water which has been plasma activated by non-thermal plasma. As a result, further improvements in plant growth and disease avoidance are achieved. [0005] Thus, this invention provides an improved plant growing process comprising contacting the roots of a plant being grown by soil-free horticulture with feed water that has been plasma activated by non-thermal plasma.

[0006] In addition, this invention also provides a plant growing assembly for growing a plant by soil-free horticulture comprising a housing for supporting the plant so that the roots of the plant can be suspended in a soil-free medium, a feed water supply assembly structured to contact these plant roots with feed water, and a plasma generating system for plasma-activating the feed water with non-thermal plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] This invention may be more readily understood by reference to the following drawings wherein:

[0008] Fig. 1 is a schematic illustration of a conventional system for generating plasma activated water in bulk with direct plasma exposure;

[0009] Fig. 2 is a schematic illustration of a conventional system for generating plasma activated water in bulk with indirect plasma exposure;

[0010] Fig. 3 is a schematic illustration of a conventional system for generating plasma activated water in the form of a mist or spray;

[0011] Fig. 4 is an illustration of a first embodiment of this invention in which the plasma activated water mist or spray produced by the system of Fig. 3 is used to spray the roots of a plant being grown by aeroponics;

[0012] Fig. 5 illustrates another embodiment of this invention in which multiple water mist or spray generators and multiple plasma generating systems are used to mist or spray the roots of a single plant being grown by aeroponics; [0013] Fig. 6 is a view similar to Fig. 5 illustrating yet another embodiment of this invention in which multiple water mist or spay generators and multiple plasma generating systems are used to spray the roots of multiple plants being grown by aeroponics;

[0014] Fig. 7 illustrates still another embodiment of this invention in which the water mist or spray used for spaying the roots of a plant being grown by aeroponics is plasma activated using a direct plasma rather than the indirect plasma used in the embodiments of Fig. 4-6;

[0015] Figs. 8-11 illustrate additional embodiments of this invention in which plasma activated water is used to grow plants by hydroponics.

DETAILED DESCRIPTION

Definitions

[0016] For the purposes of this disclosure, it will be understood that "soil-free horticulture" means a plant growing process in which a plant is grown without using soil as a root-encasing medium. In addition, "hydroponics" will be understood to mean a type of soil-free horticulture in which the roots of the plant are suspended in a body of nutrient rich water, while "aeroponics" will be understood to mean a type of soil-free horticulture in which the roots of the plant are suspended in a gaseous medium where they are contacted with droplets of nutrient rich water regardless of the particle size of the droplets. Meanwhile, "geoponics" means a plant growing process in which the roots of the plant are encased in a natural or synthetic soil. Plant growing processes in which the roots of a plant are suspended in a body of water that also includes an inert root-supporting material such as expanded clay aggregates, glass waste grow stones, coir peat, rice husks, perlite, vermiculite, sand, gravel and the like are also considered to be hydroponic growing processes for the purposes of this disclosure.

Aeroponics

[0017] This invention can be used to improve any aeroponic process in which the roots of the plants being grown are suspended in air or other gas where the roots are sprayed with nutrient rich feed water. [0018] Such processes are well known and described in a number patents and publications, examples of which include Progressive Plant Growth Has Business Booming, pp. 64-67, Spinoff, © 2006, National Aeronautics and Space Administration, U.S. 2015/0102137, U.S. 2015/0068122, U.S. 2015/027051, U.S. 2014/0338261, U.S. 2014/0311029 and U.S. 2014/0000162. See, also, U.S. 3,931,695 as well as U.S. 2014/0325908, which provide a more general disclosure of controlled environment agriculture ("CEA") of which aeroponics is a part.

[0019] As described in these and other publications, three important features which characterize aeroponics are that (1) the individual plants being grown are isolated from one another in the sense that their roots are not comingled in a common root-encasing medium, (2) the composition and amount of the nutrient rich feed water with which the roots of these plants are sprayed can be precisely controlled, and (3) the composition of the gaseous atmosphere to which these roots are treated can also be precisely controlled. As a result of these features, many advantages can be achieved by aeroponics which are not possible in conventional geoponic and hydroponic growing techniques. Examples of such advantages include pathogen-free growing, pesticide-free growing, herbicide-free growing, improved plant health, optimum growth rates, better sprouting, faster germination, more blooms, bigger yields, and substantially reduced water and nutrient requirements.

Hydroponics

[0020] This invention can also be used to improve any hydroponic process in which the roots of the plants being grown are suspended in a body of nutrient rich feed water.

[0021] Such processes are also well known and described in a number patents and publications, examples of which include U.S. 4,038,779, U.S. 5,588,254, U.S. 7,637,055 and U.S. 8,720,110.

[0022] In hydroponics, the body of nutrient-rich feed water in which the roots of the plant are suspended can be static, in which case the nutrient-rich feed water is normally changed periodically, or dynamic in which case the nutrient-rich feed water continuously flows past the roots. Also, regardless of the particular type of hydroponic growing process employed, an inert root-supporting material such as expanded clay aggregates, glass waste grow stones, coir peat, rice husks, perlite, vermiculite, sand, gravel and the like can be included in the nutrient-rich feed water for physically supporting the roots there, if desired.

[0023] As in the case of aeroponics, important features of hydroponics are that (1) the individual plants being grown are isolated from one another in the sense that their roots are not comingled in a common root-encasing medium and (2) the composition and amount of nutrient rich feed water with which the roots of these plants are treated can be precisely controlled. As a result, improved plant health, better growth rates, bigger yields, and reduced water and nutrient requirements are achieved relative to conventional (geoponic) growing processes.

Plasma Activation

[0024] In accordance with this invention, the nutrient rich feed water which is used to grow plants by soil-free horticulture processes is feed water which has been plasma activated by nonthermal plasma.

[0025] A plasma is a gaseous medium which is at least partially ionized and hence contains free electrons, ions and neutral particles. It can be formed by exposing a gas to an electric field formed between two electrodes, such as, for example, a high voltage electrode and a ground.

[0026] Generally speaking, there are two types of plasmas, a thermal plasma and a non-thermal plasma. A major difference between these two types of plasmas is the overall temperature of the plasma. In a thermal plasma, most of the molecules are ionized. As a result, the temperature of a thermal plasma is typically a few thousand degrees Celsius or more. In such a plasma, the electrons, ions and neutrals are said to be in thermal equilibrium with one another in the sense that they exist at essentially the same high temperature. In contrast, in a non-thermal plasma, only a small percentage of the molecules are ionized. As a result, the ions and neutrals are at a much lower temperature than the electrons. The overall result is that the temperature of a nonthermal plasma, as a whole, is often at or near room temperature.

[0027] In accordance with this invention, the nutrient rich feed water which is contacted with the roots of the plants being grown by soil-free horticulture is generated by exposing feed water to a non-thermal plasma. Activating water with plasma to obtain plasma activated water is shown and described in numerous publications including U.S. 2014/0322096, U.S. 2014/0100277, WO 2002/059046, WO 2007/048806, WO 2012/018891 and U.S. Pat. No. U.S. 7,291,314, the disclosures of which are incorporated herein by reference in their entireties. As described there, plasma activation of water can generate a variety of different ingredients relevant to plant growth including reactive oxygen species ("ROS") such as hydrogen peroxide and reactive nitrogen species ("RNS") such as NO, (N0₂)^" and (N0₃)^". In addition, various additional properties of the water relevant to plant growth may also be affected including pH, oxidation-reduction potential and conductivity.

[0028] One known method for plasma activating water is illustrated in Figure 1, which shows a dielectric barrier discharge ("DBD") plasma generating system 100 including high voltage source 102, conductor 104, housing 108, high voltage electrode 106 and dielectric barrier 110. Plasma generating system 100 also includes reservoir 120 which is grounded by means of conductor 122. During operation, high voltage source 102 is turned on and non-thermal plasma 130, which forms below the dielectric barrier 110 and contains electrons, positive ions, negative ions and neutral particles, activates water 126 in container 120.

[0029] Another known method for plasma activating water is illustrated in Figure 2, which shows a plasma generating system 200 which is similar to plasma generating system 100 of Fig. 1, except that plasma generating system 200 further includes filter 250 in the form of a conductive mesh that is grounded by grounding conductor 222. Plasma generating system 200 operates in much the same way as plasma generating system 100, except that charged ions and electrons are prevented from passing through filter 250. The modified plasma 230 so obtained, which is typically referred to as an "afterglow" or "indirect" plasma, then activates the water 126 in reservoir 120.

[0030] Note in this regard that, in this disclosure, modified plasmas in which the charged ions and electrons have been removed such as produced in the system of the above Fig. 2 are referred to as "indirect" plasmas. In contrast, plasmas containing all of the ingredients of a full plasma, i.e., electrons, positive ions, negative ions and neutrals such as produced by the system of Fig. 1, are referred to in this disclosure as " direct plasmas." Unless otherwise clear from context, "plasma" will be understood to include both direct plasmas and indirect plasmas. The high voltage power source used to generate both of these types of plasmas may be a DC power source, a high frequency AC power source, an RF power source, a pulsed DC power source, a pulsed AC power source, a microwave power source or the like. In some embodiments, these high power voltage power sources can be operated with voltages that range from 3 kV to 30 kV at frequencies ranging from 50 Hz to 50 kHz. They can also be pulsed with a duty cycle of 1-100 % and pulse duration of 1 nanosecond up to 10 microseconds. Meanwhile, filter 250 in the embodiment of Fig. 2 can comprise a copper woven wire cloth having a 16 x 16 mesh size with a 0.011" wire diameter and a 0.052" opening size (67% opening area). However, a mesh made of different conducting materials, wire diameters and opening sizes can also be used. Producing plasma activated water using the plasma generating systems of the above Figs. 1 and 2 is more thoroughly described in commonly assigned application U.S. 2014/0271354 (atty. docket 35416/04005), the entire disclosure of which is incorporated herein by reference.

[0031] A method for plasma activating water in the form of a mist or spray is illustrated in Figure 3, which shows a dielectric barrier discharge ("DBD") plasma generating system 300 including housing 302, first high voltage source 304 electrically connected to first high voltage electrode 306 inside housing 302, second high voltage source 308 (which may be the same as or different from first high voltage source 304) electrically connected to second high voltage electrode 310 also inside housing 302 which is spaced from high voltage electrode 306, dielectric barriers 312 and 314 associated with high voltage electrodes 306 and 310, respectively, and grounded filters 316 and 318 in the form of a conductive mesh also associated with high voltage electrodes 306 and 310, respectively. Associated with plasma generating system 300 is mist or spray generator 320 such as, for example, a piezoelectric disc, a spray nozzle, an atomizing nozzle, or the like for generating and projecting water mist or spray 322 through the open space between electrodes 306 and 310 of plasma generating system 300 and then out of housing 302 through an exit passageway (not shown). If necessary, a fan or similar device can be used to propel the mist or spray generated by mist or spay generator 320 through the plasma generated and then out of housing 302 through its exit passageway.

[0032] During operation, the plasma generated by high voltage sources 304 and 308 contacts the water droplets forming water mist or spray 322 as they pass through the plasma , thereby creating plasma activated mist or spray 323. High voltage sources 304 and 308 can be operated in the same way as high voltage source 102 in the embodiments of Figs. 1 and 2 above. [0033] Producing plasma activated water mists or sprays using the plasma generating system of Fig. 3 is more thoroughly described in commonly assigned application S.N. 62/018, 179, filed June 27, 2014 (atty. docket 35416/04020), the entire disclosure of which is also incorporated herein by reference. Although dielectric barrier discharge plasmas are described in detail herein, other types of plasma generators, such as, for example, corona discharge plasma generators, radio frequency generators, and the like may be used for activating water mists or sprays.

[0034] Figure 4 illustrates a plasma generating system of the type illustrated in Fig. 3 being used to plasma activate water mist or spray being sprayed onto the roots of a plant being grown by aeroponics in accordance with an exemplary embodiment of this invention. As shown there, a plant growing assembly comprises housing 402 for supporting plant 430 being grown by aeroponics and a feed water supply assembly for contacting the roots of a plant being grown by aeroponics with a mist or spray of plasma activated water. Housing 402 is structured in such a way that plant 430 is maintained in an upper portion thereof with its roots 432 hanging down into the interior of housing 402. Meanwhile, the feed water supply assembly comprises reservoir 434 located in a lower portion of housing 402 for containing feed water and mist or spray generator 420 located in reservoir 434 for generating feed water mists or sprays 422 and 423 from this feed water and directing these feed water mists or sprays at roots 432 of plant 430.

[0035] This exemplary embodiment of a plant growing assembly also includes plasma generating system 400 arranged so that feed water mists or sprays 422 and 423 traveling from reservoir 434 to roots 432 pass through plasma generated in the open space between electrodes 406 and 410 and their associated grounded filters 416 and 418, respectively. With this structure, feed water mists or sprays 422 and 423 are treated and hence activated by the indirect plasmas generated by high voltage sources 404 and 408 of plasma generating system 400. As a result, nutrients which may be important for plant growth such as one or more of NO, (N0₂)^" and (N0₃)^" are generated in feed water mists or sprays 422 and 423 for supplying to roots 432 of plant 430. In addition, other changes beneficial to plant growth may also occur in feed water mists or sprays 422 and 423 such as a decrease in pH as well as the generation of reactive oxygen species such as hyperperoxy radicals and hydrogen peroxide. As a result, pathogens that might be present in these feed water mists or sprays may effectively be destroyed or deactivated, thereby further enhancing the disease avoidance made possible by aeroponic growing processes. [0036] In this regard, attention is again directed to commonly assigned application U.S. 2014/0271354 (atty. docket 335416/04005), which shows that plasma activated water, and especially indirect plasma activated water, is highly effective in killing or deactivating Escherichia coli ("E. colF) bacteria. This demonstrates that the modified aeroponic growing process of this invention should be even more effective than conventional aeroponic growing processes in terms of disease avoidance, because any bacteria and other pathogens that might inadvertently contaminate the feed water in reservoir 434 will likely be destroyed or deactivated by plasma generating system 400.

[0037] In addition to further enhancing disease avoidance, it is also believed that one or more phenotypic characteristics of the plants being grown will be further enhanced by the inventive aeroponic growing process of Fig. 4. In this regard, please see Park et al., Reactive Nitrogen Species Produced in Water by Non-equilibrium Plasma Increase Plant Growth Rate and Nutritional Yield, Current Applied Physics 13 (2013) pp S19-S29, Elsevier, which indicates that plasma activated water can significantly improve growth rate and nutritional yields in plants grown by conventional (geoponic) growing processes. It is therefore believed that similar improvements in plant growth rate and nutritional yields should also be achieved in the inventive hydroponic and aeroponic plant growing processes.

[0038] Note, however, that that the inventive process and plant growing assembly illustrated in the above Fig. 4 differ from that shown in Park et al. in that, in Park et al, plasma activated feed water is generated in bulk after which portions of this plasma activated feed water, still in bulk form, are periodically fed to plants being grown in soil. In contrast, in the inventive process and system of the above Fig. 4, the feed water is converted into a mist or spray which is directly sprayed onto the roots of the plant, with this feed water mist or spray being sprayed onto these roots immediately after it is plasma activated.

[0039] Because of these differences, certain advantages are achieved by this invention which are not achieved by the technology of Park et al. For example, the amount of plasma activated feed water that needs to be generated in the inventive system is far smaller than in the technology of Park et al., because aeroponics inherently uses smaller amounts of water due to the water impinging directly on the roots of the plant. Second, there is no loss due to decay of the active ingredients in the plasma activated water used in the inventive process and system, since this water is applied to the plant roots immediately after it is generated rather than hours later, as occurs in Park et al. Third, because the plasma generated water used in the inventive process and system is applied as soon as it is generated, the operation of plasma generating system 400 can be integrated with the preexisting control system used for controlling misting/spraying of the plants. As a result, a separate control system for controlling the operation of the plasma generator can be avoided.

[0040] As indicated above, plasma activating the feed water being supplied to a plant can have a variety of different effects on plant growth. In this regard, it is well appreciated in the art that the particular effect plasma activation has on water depends on a number of different factors including the type of plasma generating system used as well as the manner in which this system is operated. For example, it is well understood in the art that DBD systems, when operated at relatively lower power consumptions, primarily generate oxygen-reactive ingredients such as hydrogen peroxide. In contrast, when operated at relatively higher power consumptions, such systems primarily generate nitrogen reactive ingredients such as NO, (N0₂)^" and (N0₃)^".

[0041] Accordingly, when selecting the particular type of DBD plasma generating system 400 to use in connection with this invention, as well as the manner in which it is operated, it is desirable to choose a system and mode of operation which provides the best combination of nutrient supply and pathogen destruction for the particular plants being grown. Thus, in some embodiments of this invention, plasma generating system 400 will be selected and operated at relatively higher power consumptions so as to foster nitrogen-based nutrient supply, while in other embodiments of this invention, plasma generating system 400 will be selected and operated at relatively lower power consumptions so as to foster generation of hydrogen peroxide for pathogen control. In any event, given the known effects that different types and operating modes of different plasma generating systems can have on the composition and properties of plasma activated water, persons of ordinary skill in the art should have no difficulty in selecting the particular type of plasma generating system to use in each embodiment of this invention, including its particular manner of operation, by routine experimentation. [0042] Fig. 5 illustrates another embodiment of this invention in which multiple water mist generators and multiple plasma generating systems are used. As shown there, the plant growing assembly of this embodiment is similar to that of Fig. 4, except that the plant growing assembly of this embodiment includes two subsidiary reservoirs 536 and 538 in addition to primary reservoir 534 for holding feed water, two mist or spray generators 520 and 521 for generating water mists or sprays 522 and 523 from the feed water in subsidiary reservoirs 536 and 538, respectively, two plasma generating systems 500 and 501 arranged to activate water mists or sprays 522 and 523 and then direct these activated water mists or sprays to the roots 532 of plant 530, and two conduits 540 and 542 for directing water mists or sprays 522 and 523 from subsidiary reservoirs 536 and 538 to plasma generating systems 500 and 501, respectively.

[0043] In operation, this plant growing assembly works in essentially the same way as the plant growing assembly of Fig. 4, except that two feed water mist or spray generators and two plasma generating systems are used. The result is that a greater amount of plasma activated water can be sprayed onto roots 532 of plant 530 in a given amount of time relative to the embodiment of this invention of Fig. 4.

[0044] Fig. 6 illustrates yet another embodiment of this invention in which multiple plants are aeroponically grown in accordance with an exemplary embodiment of this invention using a single feed water mist or spray generator. The plant growing assembly of this embodiment is similar to that of Fig. 5, except that the plant growing assembly of this embodiment is arranged to process multiple plants 630, 631, 632 and 633 using a single mist or spray generator. For this purpose, a single feed water mist or spray generator 620 is provided for generating feed water mist or spray from the feed water contained in single common reservoir 634 and for directing this feed water mist or spray into mist or spray header 609. In addition, mist or spray supply conduits 611, 613, 615 and 617 are provided for directing separate portions of this feed water mist or spray towards the roots of plants 630, 631, 632 and 633, respectively. Four separate plasma generating systems 600, 601, 602 and 603 of the type used in Figs 3-5 are arranged to plasma activate these separate portions of this feed water mist or spray as they travel from mist header 609 to the roots of these plants. [0045] In operation, this assembly works in essentially the same way as the assemblies of Figs. 4 and 5, except that multiple plants are being processed using only a single feed water mist generator and a single reservoir for feed water. The result is that a greater number of plants can be processed using common equipment for supplying plasma activated water, which reduces costs.

[0046] Still another exemplary embodiment of this invention is illustrated in Fig. 7. This embodiment is similar to the embodiment of Fig. 6, except that in this embodiment, the feed water mist or spray is plasma activated using a direct plasma rather than the indirect plasma used in the embodiment of Fig. 6. In addition, only a single plasma generating system is used.

[0047] For this purpose, multiple mist or spray generators, such as, for example, piezoelectric discs, 720, 721 and 722 are provided for generating water mists or sprays 744, 746 and 748 from the feed water contained in reservoir 734 and directing these water mists or sprays towards the roots of plants 730, 732 and 734, respectively. In addition, high voltage source 704 of plasma generating system 700 is provided to generate and project direct plasma 705 across housing 702 from one side to the other in such a way that water mists or sprays 744, 746 and 748 pass through this direct plasma (in its so-called Z direction) as they transit between reservoir 734 and the roots of plants 730, 732 and 734. As a result, these water mists or sprays are activated by this direct plasma.

[0048] In operation, this plant growing assembly works in much the same way as the plant growing assembly of Fig. 6, except that only a single plasma generating system is used and, in addition, the feed water is activated by direct plasma rather than indirect plasma. The result is that capital costs are significantly reduced, since only one plasma generating system is used.

[0049] An embodiment of this invention in which the soil-free horticultural process being used is hydroponics rather than aeroponics is illustrated in Fig. 8. As shown there, a plant growing assembly for growing plants 830, 831 and 832 by hydroponics comprises housing 802 for supporting the plants so that lower portions of their roots are suspended in plasma activated feed water containing nutrients and other ingredients relevant to plant growth such as NO, (N0₂)^", (N0₃)^", hyperperoxy radicals and hydrogen peroxide flowing along flow path 852. To provide this plasma activated feed water, a reservoir 834 containing feed water is arranged in fluid communication with the inlet 855 of flow path 852, while water pump 820 is arranged to pump this feed water into flow path 852 via inlet 855.

[0050] To plasma activate the feed water in reservoir 834, gas pump 860 is provided to supply a working gas such as air, nitrogen, oxygen, carbon dioxide, various noble gases such as He, Ar, Xe, Kr, etc. and mixtures thereof through aerator 862 and into the pool of feed water in reservoir 834, while plasma reactor 800 such as an RF plasma jet or microwave plasma jet is arranged to treat this gas for generating various species relevant to plant growth before it passes into the feed water. As a result, the reactive oxygen and nitrogen species which are generated in this gas as it passes through plasma reactor 800 are introduced into the feed water, thereby plasma activating this water. This plasma activated water, which contains ingredients relevant to plant growth including oxygen-containing species for inactivating pathogens and nitrogen-containing species for plant fertilization, is then contacted with the roots of plants 830, 831 and 832, thereby achieving significant enhancements in both disease avoidance and plant growth, as explained above.

[0051] If desired, the plant growing assembly of Fig. 8 can be designed so that any plasma activated water not consumed by plants 830, 831 and 832 as it passes along flow path 852 is returned to reservoir 834 for mixing with fresh feed water. This is illustrated in Fig. 8, which shows plasma activated feed water passing out of flow path 852 being directed back into reservoir 834 by outlet 853 of flow path 852. With this approach, unused plasma activated feed water can be recycled for reuse, which reduces the amount of plasma activation needing to be accomplished by plasma reactor 800 and its associated gas supply. Because plasma reactor 800 does not directly treat the feed water in reservoir 834 but only the gas being discharged into this water, it is believed that the plasma generated by plasma reactor 800 will have little or no effect on the ingredients relevant to plant growth that may be present in this feed water.

[0052] Fig. 9 illustrates another embodiment of this invention in which the plants are being grown by hydroponics. The plant growing assembly shown there is essentially the same as that shown in Fig. 8, except that in the plant growing assembly of Fig. 9, aerator 862 is not used. Rather, plasma generator 900 is designed and arranged so that the gas passing into this plasma generator is directly discharged into the feed water in reservoir 934 by this plasma generator. In addition, plasma generator 900 is further arranged so that the plasma it generates directly treats both the water in reservoir 934 as well as the gas passing through this plasma generator simultaneously. Examples of plasma sources which can be used as plasma generator 900 include pulsed corona discharges, pulsed spark discharges, plasma jets, gliding spark discharges, and gliding arc plasmatrons. With this approach, not only can aerator 862 be eliminated but, in addition, it is believed the operation of plasma generator 900 will be more efficient, because at least a portion of the plasma it generates directly treats the water in reservoir 934.

[0053] As in the embodiment of Fig. 8, the plant growing system of Fig. 9 can also be designed with an outlet 953 for recycling to reservoir 834 any plasma activated feed water not consumed by plants 930, 931 and 932. Although plasma generator 900 in this embodiment does directly treat the feed water in reservoir 934, it is believe that this will have no significant negative impact on any previously-generated ingredients relevant to plant growth that may be present in this feed water from recycled plasma activated feed water, at least insofar as its nitrogen- containing species are concerned. This is because the effect of exposing these previously- generated nitrogen-containing species to additional plasma will likely at most be to further oxidize the nitrogen atoms in these species. Thus, it is believed that, at most, NO will be oxidized to (N0₂)^" and (N0₃)^"' while (N0₂)^" will be oxidized to (N0₃)^". Neither of these conversions is detrimental, as these more highly oxidized nitrogen-containing species still can be important to plant growth.

[0054] Fig. 10 illustrates another embodiment of this invention in which the plants are being grown by hydroponics. The plant growing assembly shown there is essentially the same as that shown in Figs. 8 and 9, except that in the plant growing assembly of Fig. 10, a working gas is not used. Rather, plasma generator 1000 is used which generates a plasma directly on the surface of the feed water in reservoir 1034. The plasma can be either a direct plasma or an indirect plasma. Examples of plasma sources which can be used for this purpose include surface DBD (dielectric barrier discharge) optionally operating in a NO mode, volumetric DBD optionally operating in a NO mode, arc discharge and pulsed arc discharge. [0055] Fig. 11 illustrates still another embodiment of this invention in which the plants are being grown by hydroponics. The assembly shown there is essentially the same as that shown in Fig. 10, except that in the assembly of Fig. 11, a working gas is used. That is to say, the feed water in reservoir 1134 is plasma activated by a plasma source 1100 which simultaneously treats the surface of this feed water with plasma as well as a working gas which is directed at this surface by means of gas pump 1160 after passing through this plasma source. Examples of plasma sources which can be used for this purpose include surface DBD (dielectric barrier discharge) optionally operating in a NO mode, volumetric DBD optionally operating in a NO mode, gliding arc plasmatron, RF plasma jet, microwave plasma jet, gliding arc discharge, arc discharge and pulsed spark discharge

[0056] In still other embodiments of this invention in which the plants are being grown by hydroponics, the same systems and approaches shown in Figs. 8-11 can be used, except for replacing the particular plasma sources shown there with plasma sources which are located under the surface of the feed water and which do not use a working gas. Examples of plasma sources which can be used for this purpose include a pulsed corona source, a pulsed arc or spark source and a dielectric barrier discharge generator such as shown in the above-noted Park et al. article.

[0057] In some exemplary systems, the plasma generates nitrate (N0₃) from nitrogen in the air. Nitrate is a nutrient that is easily absorbed by plan roots without the need for microbes that are required in other systems. In addition, the plasma generates hydrogen peroxide (H₂0₂) from oxygen in the air and water. Hydrogen peroxide, along with active species generated by the plasma, aids in disinfection and can be a source of 0₂, which is critical for root health, especially in hydroponic systems.

[0058] In some embodiments, a solid metal embedded catalyst may be used to decompose hydrogen peroxide to form water and oxygen gas. This allows a control of hydrogen peroxide concentration and provides a high volume of oxygen. In some embodiments, the decomposition of the gas can be used as a source of pressure to eliminate the need for external pumps. [0059] In some embodiments, the alkalinity of the water increases as a result of the plants absorption of the nitrite. Because activating water with plasma causes the water to become more acidic, the activated water may be used to balance the buildup in alkalinity.

[0060] In addition, plasma activated water contains active species that have antimicrobial properties, the plasma activated water will have a significantly higher rate of disinfection than hydrogen peroxide alone as the plasma activated water contains additional reactive species that also have disinfection and antimicrobial properties.

[0061] Although only a few embodiments of this invention have been described above, it should be appreciated that many modifications can be made without departing from the spirit and scope of this invention. For example, although many of the above embodiments use piezoelectric discs for generating feed water mists or sprays, any other device capable generating feed water mists or sprays can also be used, examples of which include spray misters and steam misters.

[0062] In addition, although the embodiments of this invention described in Figs. 4-7 have particular numbers of plants being processed, particular numbers of reservoirs for feed water, particular numbers of feed water mist or spray generators and particular numbers of plasma generating systems, it should be appreciated that these descriptions are provided for illustrative purposes only and that any number of these respective elements can be used. For example, although the embodiment of Fig. 5 is described as having only one plant being processed using water mists or sprays obtained from only two separate sources, it should be appreciated any number of plants can be processed with any number of separate water mist or spray sources using the approach of this embodiment.

[0063] Similarly, although the above description indicates that the roots of the plants being grown by aeroponics are suspended in air, it should be appreciated that any other gaseous atmosphere which is useful for growing plants by aeroponics can be used. For example, air which is augmented with other gases which promote plant growth such as nitrogen and carbon dioxide or aid in plant health such as oxygen can be used. [0064] In the same way, although the above description indicates that water is used as the plant growing liquid, any other liquid which is know or which may become known for this purpose can also be used.

[0065] In addition, although the above description indicates that the feed water is plasma activated before it contacts the plants being grown, it should be appreciated that the plasma generating system used to accomplish this plasma activation can be arranged to treat and thereby activate this feed water at the same time that it contacts the roots of the plants being processed.

[0066] Also, although the above description does not discuss various features common to aeroponic growing of plants such as the manner of controlling operating variables such as the pH of the feed water, the types and amounts of nutrients and other ingredients in the feed water, the temperature of the plant roots, the particle size of the spray or mist applied to the plant roots, the amount of light used, etc., it should be appreciated that all of these features can be employed in a conventional way when carrying out the modified aeroponic growing process of this invention.

[0067] Similarly, although the above description focuses primarily on planar DBD electrodes, other types of plasma sources using various working gases, such as air and nitrogen can be used. The plasma sources which produce nitrogen-rich species using air include a RF plasma jet, microwave plasma jet, volumetric dielectric barrier discharge (DBD) optionally operating in a NO mode, surface DBD optionally operating in a NO mode, gliding arc discharge, arc discharge, or pulsed spark discharge

[0068] Further, although Figs. 1 and 2 show that the feed water being plasma activated is a pool of this water contained in reservoir 120, it should be appreciated that the plasma generating system used in this and other embodiments of this invention can be structured and arranged so that the body of feed water being treated is in the form of a flowing body of water flowing through or past this plasma generating system.

[0069] Finally, note that the recycle approach illustrated in the hydroponics embodiments of Figs. 8-11 in which unused plasma activated feed water is returned back to the feed water system for reuse in another application of plasma activated feed water can also be used in the aeroponics embodiments of this invention such as illustrated, for example, in Figs. 4-7. [0070] All such modifications are intended to be included within the scope of this invention, which is to be limited only by the following claims.

Claims

CLAIMS:

1. An improved plant growing process comprising contacting the roots of a plant being grown by soil-free horticulture with feed water that has been plasma activated by nonthermal plasma.

2. The modified process of claim 1, wherein the soil-free horticultural process is aeroponics.

3. The modified process of claim 2, wherein the non-thermal plasma is a direct plasma.

4. The modified process of claim 2, wherein the non-thermal plasma is an indirect plasma.

5. The modified process of claim 2, wherein the non-thermal plasma is generated by a dielectric barrier discharge (DBD) plasma system.

6. The modified process of claim 2, wherein the feed water is plasma activated by exposing the surface of a pool of feed water to a non-thermal plasma.

7. The modified process of claim 2, wherein the feed water is plasma activated by exposing a mist of feed water to a non -thermal plasma.

8. The modified process of claim 7, wherein the non-thermal plasma is generated by a dielectric barrier discharge plasma system which comprises a pair of opposed electrodes arranged to define a space there between, and further wherein the feed water is plasma activated by passing a mist of the feed water through this space.

9. The modified process of any one of claims 1-8, wherein multiple plants are grown by aeroponics, wherein the non-thermal plasma is generated by at least one plasma generating system, and further wherein the same plasma generating system is used to activate the feed water which is sprayed onto the roots of more than one plant.

10. The modified process of any one of claims 1-8, wherein the feed water is plasma- activated before it contacts the roots of the plant.

11. The modified process of claim 1, wherein the soil-free horticultural process is hydroponics.

12. The modified process of claim 11, wherein multiple plants are grown and further wherein more than one plant are grown with feed water plasma-activated by the same plasma generating system.

13. A plant growing assembly for growing a plant by a soil-free horticultural process comprising a housing for supporting the plant so that the roots of the plant are suspended in a soil-free medium, a feed water supply assembly for contacting the roots with feed water, and a plasma generating system for plasma-activating the feed water with non-thermal plasma.

14. The plant growing assembly of claim 13, wherein the plasma generating system is structured to generate a direct plasma.

15. The plant growing assembly of claim 13, wherein the plasma generating system is structured to generate an indirect plasma.

16. The plant growing assembly of any one of claims 13 to 15, wherein the soil-free horticultural process is aeroponics, wherein the soil-free medium is a gas, and further wherein the feed water supply assembly comprises a spray generator for spaying the roots of the plant with a mist or spray of plasma-activated feed water.

17. The plant growing assembly of claim 16, wherein the feed water supply assembly comprises a mist or spray generator for generating a water mist or spray, and further wherein the plasma generating system is structured to treat the water mist or spray.

18. The plant growing assembly of claim 17, wherein the plasma generating system is a dielectric barrier discharge plasma system which comprises a pair of opposed electrodes arranged to define a space therebetween, and further wherein the mist or spray generator is structured to project a mist or spray of water through this space.

19. The plant growing assembly of any one of claims 13 to 15, further comprising a reservoir for containing a pool of feed water, and further wherein the plasma generating system is structured to treat the surface of this pool of feed water.

20. A plant growing assembly comprising: a housing for holding one or more plants; a source of feed water; a plasma generator; a mist or spray generator; wherein feed water from the source of feed water is converted to a mist or spray and passed through plasma generated by the plasma generator and directed at the roots of one or more plants.

21. The plant growing assembly of claim 20 further comprising a catalyst for decomposing hydrogen peroxide to form water and oxygen gas.

22. The plant growing assembly of claim 20 further comprising a first power setting for delivering a first power level to the plasma generator and a second power setting for delivering a second power level to the plasma generator, wherein the first power level generates more oxygen-reactive ingredients than the second power level and the second power level generates more nitrogen reactive ingredients than the first power level.