The invention relates to a method of cultivation of algae or cyanobacteria in the presence of a luminous material that converts light of a first wavelength to a second wavelength more suitable for use in photosynthesis by the algae or cyanobacteria, and apparatus for performing the method. In one embodiment the apparatus (50) is of flexible plastic with fluorescent light concentrator or light guide (76) and perforated pipe (56) for bubbling carbon dioxide through the culture. The algae or cyanobacteria may be used to produce biofuels.

Claims

The invention claimed is:

1. A bioreactor comprising a plurality of containment apparatuses, each containment apparatus comprising a first light guide, wherein: the first light guide is a luminescent light guide comprising a first luminescent material; and the first light guide guides light to a second luminescent material underneath the first light guide; and the first light guide luminescent material emits visible light between 540 nm and 600 nm suitable for absorption by the second luminescent material; and a second light guide is formed between adjacent containment apparatuses.

2. The bioreactor of claim 1, wherein each containment apparatus underneath the first light guide comprises the second luminescent material that absorbs visible light emitted by the first luminescent material.

3. The bioreactor of claim 2, wherein the second luminescent material emits red light.

4. The bioreactor of claim 1, wherein the second light guide is a liquid-filled light guide.

5. The bioreactor of claim 4, wherein the liquid-filled light guide is filled with clear water.

6. The bioreactor of claim 1, wherein the first light guide or the second light guide widens in one axis.

7. The bioreactor of claim 1, wherein the first light guide or the second light guide widens in two axes.

8. The bioreactor of claim 1, wherein the first light guide or the second light guide comprises a non-curving surface for internal reflection.

9. The bioreactor of claim 1, wherein the first light guide or the second light guide comprises a curving surface for internal reflection.

10. The bioreactor of claim 1, wherein the second light guide further comprises a double wall that maintains a boundary for guiding light.

11. The bioreactor of claim 1, wherein the first light guide comprises a light extractor that extracts light from the first luminescent material at angles that would otherwise be trapped by total internal reflection according to the refractive index of the first luminescent material.

12. The bioreactor of claim 11, wherein light is extracted in one direction.

13. The bioreactor of claim 11, wherein light is extracted in more than one direction.

14. The bioreactor of claim 1, wherein the first light guide is adapted to reduce reabsorption of luminescence by the first luminescent material.

15. The bioreactor of claim 14, wherein the first light guide is adapted to reduce reabsorption by means of a substrate lacking a luminescent material and of sufficient refractive index that luminescence is guided by the substrate.

16. The bioreactor of claim 1, wherein each containment apparatus is triangular, with a base positioned away from a light source and a vertex positioned towards the light source.

17. The bioreactor of claim 1, wherein each containment apparatus is tubular and triangular, with a base positioned away from a light source and a vertex positioned towards the light source.

18. The bioreactor of claim 1, further comprising a bio-digester.

19. A method for growing an aquatic plant, an alga or a cyanobacterium comprising growing the aquatic plant, alga or cyanobacterium in the of bioreactor of claim 1. Description

This application is a continuation-in-part of International patent application PCT/AU2010/000090 filed 29 Jan. 2010, which claims priority to Australian provisional patent application 2009900346 filed 30 Jan. 2009, and Australian provisional patent application 2009904028 filed 24 Aug. 2009, all of which are incorporated herein by reference. This application also claims priority to Australian provisional patent application 2010903485 filed 4 Aug. 2010, and Australian provisional patent application 2011902211 filed 3 Jun. 2011, both of which are incorporated herein by reference.

FIELD

The invention relates to an algae containment apparatus and a bioreactor, and to uses and methods for growing algae or cyanobacteria related thereto. The invention also relates to a light guide, and to uses and methods related thereto.

BACKGROUND

Production of biofuel from renewable processes is a key step towards securing a more responsible energy economy for the future. But beyond this, these fuels must be used in way that does not generate, or minimises, harmful emissions such as carbon dioxide.

Many important advances in biofuel production have been made. However, while advances in commercial production of algae has made great leaps regarding species selection, growth media, and even genetic manipulation, there remains a disproportionate lack of advance in the areas relating to working algal pond depth and harvesting. Algal pond depth is restricted by limited penetration of sunlight into the pond. Efficient harvesting of large quantities of algae requires large expenditures of energy and money.

Closed bioreactors are one means to overcome some of these disadvantages. However, such bioreactors are severely limited by cost and infrastructure requirements especially for biofuel applications. Open ponds are much more economic, particularly for cultivating algae, but are often is restricted by the availability of light to specific dimensions within the algal ponds. That is, light may only penetrate to a certain depth leaving many algae with sub-optimal illumination for growth, or even no light for growth.

In addition most algae growing systems, e.g. closed bioreactors or open ponds, experience photo-inhibition caused by over exposure to sunlight levels at the water surface. In an open pond this occurs a within the first few centimeters of water where little algae growth results. Only after the incoming sunlight intensity has been greatly reduced by the absorbance of photo-inhibited algae at the surface, do algae begin to grow at intermediate depths.

Furthermore, algae depend on photosynthetic pigments, such as chlorophyll, that selectively absorb certain wavelengths of light while other wavelengths are of lesser use, thus further reducing the overall utility of incoming solar radiation. As a result, algae systems exhibit low solar-photosynthetic efficiency. By most estimates, the photosynthetic efficiencies of current algae bioreactor systems average between 2% to 7% and have a maximum theoretical yield of 11% solar-photosynthetic efficiency.

Therefore, there is a need for an improved bioreactor that addresses the disadvantages of previous bioreactors with respect to bioreactor design, cost, and the inherent biological incompatibilities between the available light in such bioreactors and the algal photosynthetic system.

It is to be understood that any reference herein to prior art does not constitute an admission that such art forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY

A first aspect provides an algae containment apparatus, for growing an aquatic plant, an alga or a cyanobacterium, the algae containment apparatus comprising a first luminescent material that emits visible light suitable for growing the aquatic plant, alga or cyanobacterium, wherein the algae containment apparatus is capable of forming a first light guide.

A second aspect provides a bioreactor comprising the algae containment apparatus of the first aspect.

A third aspect provides a method for growing an aquatic plant, an alga or a cyanobacterium comprising growing the aquatic plant, alga or cyanobacterium in the algae containment apparatus of the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides absorbance spectra of chlorophylls and similar compounds.

FIG. 1a depicts absorbance spectra for chlorophyll a and chlorophyll b and a schematic absorbance spectrum for a luminescent material that absorbs green light. Also depicted is the corresponding schematic emission spectrum for the luminescent material illustrating emission of red light that overlaps with chlorophyll absorbance.

FIG. 1b depicts absorbance spectra corresponding to those illustrated in FIG. 1a, without the schematic absorbance and emission spectra of the luminescent material. Also illustrated are the absorbance spectra of .beta.-carotene, phycoerythrin and phycocyanin. Phycoerythrin and phycocyanin are phycobilins that absorb light for photosynthesis in cyanobacteria.

FIG. 1c depicts absorbance spectra of chlorophyll a, chlorophyll b, and carotenoids (top) and the related photosynthetic action spectrum (bottom).

FIG. 2 graphs to optical absorbance of pure water and shows how the absorbance increases by a factor of 10 between 500 nm (about 0.0005 cm.sup.-1) to 600 nm (nearly 0.005 cm.sup.-1). This translates to an absorbance of about 1 over a 2 m path length.

FIG. 3 provides the chemical equations describing the process of carbon dioxide scrubbing by reaction with an amine (monoethanolamine, MEA) and the reversible reaction upon heating for subsequent release of carbon dioxide.

FIG. 4 provides schematic representations of an embodiment of the algae containment apparatus and an embodiment of a bioreactor comprising the algae containment apparatus.

FIG. 4a is an orthogonal section of an open pond bioreactor comprising a plurality of the algae containment apparatus.

FIG. 4b is a transverse cross section of an algae containment apparatus.

FIG. 4c depicts an overhead perspective view of an alternative raceway bioreactor comprising a plurality of algae containment apparatus.

FIG. 4d illustrates the shading and luminescent effects when algae are grown in algae containment apparatus in sunlight.

FIG. 4e is an orthogonal view of an algae containment apparatus comprising a light guide positioned on top of the algae containment apparatus.

FIG. 4f is an elevation view according to FIGS. 4d and 4f of a plurality of algae containment apparatus each comprising a light guide. Also shown is orange light emitted from the edge of the light guides.

FIG. 4g provides longitudinal cross sections of embodiments of the light guide of FIG. 4e.

FIG. 4h provides a schematic representation of one embodiment of adjacent algae containment apparatuses comprising first and second light guides

FIG. 5 provides an orthogonal representation (FIG. 5a) and a cross-sectional representation through section 5b-5b (FIG. 5b) of a prismatic light guide.

FIG. 6 is a cartoon representation of one embodiment of a surround comprising the luminescent light guide of the disclosure.

FIG. 7 is a cartoon representation of one embodiment of a cover comprising the luminescent light guide of the disclosure.

FIG. 8 is a cartoon representation of a light guide (upper) and a luminescent light guide (lower).

FIG. 9 are photographs illustrating light guidance in a luminescent material lacking light extractors (upper) and comprising light extractors (lower).

FIG. 10 is a cross-sectional representation of a luminescent light guide of the disclosure comprising light extractors (a formed plastic) positioned between layers of air (upper) and a thin polymer layer in a water filled luminescent light guide with light extractors that extract light that does not escape into the water (lower).

FIG. 11 are photographs of a luminescent light guide of the disclosure comprising light extractors (a formed plastic) inside a plastic sleeve filled with water. The light is guided by the water and guidance stops at the water fill line (right).

FIG. 12 is an orthogonal representation of a method of manufacturing a bioreactor that comprises a plurality of algae containment apparatuses formed into a sealed insert that is positioned in a vessel. Clear water is located above the algae containment apparatuses.

FIG. 13 is a cross-sectional representation of an algae containment apparatus comprising first and second light guides.

FIG. 14 is a cross-sectional representation of detail 14b of FIG. 13.

FIG. 15 is a cross-sectional representation of detail 15b of FIG. 13.

FIG. 16 is a representation of the insert (upper) prior to its sealing to the algae containment apparatus (lower) to form the sealed insert.

FIG. 17 depicts a hypothetical absorbance and emission band for a luminescent material showing a typical degree of overlap where re-absorption would occur.

FIG. 18 depicts a hypothetical absorbance spectrum of luminesced light, trapped by total internal reflection in a luminescent light guide, travelling over a distance 200 times its thickness. A large majority the fluoresced light will experience repeated cycles of re-absorption and re-emission over its journey to the edge of the light guide. This effect is reduced as luminescence occurs closer to the edge.

FIG. 19 is a representation of a luminescent light guide comprising a sheet 5 mm thick and 1 m wide from the centre (2 m in total length). A luminesced photon originating from the centre must travel through 1 m of polymer in which the luminescent material is dispersed. The absorbance and emission spectra would then be adjusted to give the spectrum shown in FIG. 18.

FIG. 20 is a representation of a luminescent light guide of the disclosure with a single layer of polymer comprising a luminescent material and a much thicker solution of liquid or other transparent material of high refractive index. The black line represents the path of light guided by total internal reflection. The light would travel almost entirely through clear material and spend very little of its journey passing through the polymer where re-absorption can occur.

FIG. 21 is a representation of a luminescent light guide of the disclosure with multiple polymer layers each comprising a luminescent material within a thicker clear layer of high refractive index.

FIG. 22 is a representation of a luminescent light guide of the disclosure placed in water and the air to luminescent light guide interface is created by air layers above and below the luminescent light guide.

FIG. 23 is a representation of a luminescent light guide of the disclosure showing the maximum curvature attainable by the luminescent light guide (upper). Light that escapes the luminescent light guide may be trapped by the water/air interface such that the light is redirected downwards (lower).

FIG. 24 shows photographs of a symmetrical pyramid shaped light extractors of the disclosure with nearly equilateral triangles with all angles near 60 degrees.

FIG. 25 shows photographs of two sides of a luminescent substrate comprising light extractors of the disclosure under a UV "blacklight". The luminescent light extracted from each light extractor is extremely efficient, but no luminescent light is extracted by the face lacking light extractors.

FIG. 26 shows photographs showing a scratch made by a knife on one side of the substrate where both sides of the substrate show nearly identical light extraction.

FIG. 27 shows representations depicting equal light extraction from all the vertices in the pyramid (right) and light extraction from one face of the light extractor and in one direction produced by an asymmetrical light extractor that is rounded on one side and possesses a sharp triangular shape on the other (left).

FIG. 28 are photographs showing light extractors in the form of a cross-shaped indentation. Light is extracted from the positive, raised side of a sample of indented red plastic (left), whereas light is not extracted from the negative, indented side (right). Similar results were achieved with a point indentation (not shown).

FIG. 29 shows photographs of three identical plant pots filled with potting soil and planted with Coriander seeds. The centre pot comprised a luminescent growing apparatus of the disclosure, which resulted in better growth than the flanking pots. The luminescent growing apparatus can be seen in the centre pot in the upper two photographs, but is not seen in the centre pot of the lowermost photograph, because it was removed to give a clear view of the plant.

FIG. 30 depicts a set of standard Cartesian x, y, z axes of a light guide and a representation of the light guide which widens in one direction, along the x axis, which favors light guidance in the direction of the widening.

FIG. 31 shows the same concept as FIG. 30, but the light guide widens along both the x and y axes such that light may be guided along a specific xy vector.

FIG. 32 is a representation of a light guide of similar composition to that of FIG. 30 with a variation such that widening of the light guide is achieved using a curved edge, where the slope of the lower edge of the light guide is exponentially increasing as it continues outward away from the centre of the light guide.

FIG. 33 depicts a light guide similar to that of FIG. 32 in which the curved widening occurs in both the x and y directions to favour total internal reflection down a specific xy vector.

FIG. 34 depicts an algae bioreactor comprising a light guide with a curved widening lower edge.

FIG. 35 depicts a light guide without widening that displays excellent light guiding ability in water.

FIG. 36 is a photograph of a light guide and bioreactor with the features of FIG. 34 complete with the straight upper boundary where the luminescent polymer with light extractors and side flaps of double layer plastics that maintain the air boundary for guiding light downwards.

FIG. 37 plots the increased growth rates and densities achieved using the light guide of FIG. 36.

FIG. 38 depicts a 10.times.5 cm light guide with light extractors in the upper portion of one of four branches on a potted Frangipani tree at the start of the growth season just before leaves or flowers have begun to grow.

DETAILED DESCRIPTION

The shallow depths at which traditional open pond algal systems operate to allow sufficient exposure to sunlight require large areas to obtain adequate algal growth. Bioreactors require smaller areas and allow larger volumes of algal growth, but suffer from the problem of restricted availability of light at depth.

The present apparatus and methods overcome this limitation by increasing the solar efficiency of algae grown in the bioreactor. Thus, more algae may be grown in a smaller volume of growth medium. Furthermore, the depth of the bioreactor may be up to 10 times greater than current designs and therefore would require 10 times less land area. Most importantly, due to the optimised light spectrum in the system, algae will be able to grow at higher concentrations within the bioreactor. Additionally, fewer materials and less transparent tubing should be required compared with current bioreactors.

Thus, the present disclosure provides the following advantages: increased photosynthetic efficiency by conversion of light absorbed at a low level into light absorbed at a higher level; sustained algal or cyanobacterial growth at depths beyond that penetrable by a light source; improved efficiency of open systems towards the efficiency of closed systems; improved efficiency of closed systems; sustained algal or cyanobacterial growth during the night; reduced land use by replacement of ponds with bioreactors; utilisation of carbon dioxide from industrial and agricultural sources for photosynthesis; and ease of harvesting.

Plants, algae or cyanobacteria grown according to the present disclosure can be used to produce biofuels, feeds, foods, food additives, bioactives such as pharmaceuticals and antibiotics, bioplastics, industrial chemicals or specialty chemicals.

In some embodiments, the luminescent material is disposed in or coated on a substrate. Thus, the substrate may emit light to the algae or cyanobacteria. In some embodiments, the substrate provides growing surfaces for the algae or cyanobacteria.

In one embodiment, the bioreactor comprises a substrate for providing growing surfaces for the algae or cyanobacteria. The substrate may comprise the luminescent material.

In some embodiments, the algae are grown in water or growth medium that is near, or in contact with, the luminescent material.

In one embodiment, the luminescent material may be part of a light guide that distributes light evenly down a water column in the shape of a sheet, tube, or other useful geometry where the algae are allowed to grow in a growth medium. The light guide functions according to methods and materials known in the art in a fashion optimised for the algae containment apparatus or bioreactor.

If used in a terrestrial environment for example, a liquid-filled light guide may comprise a single wall containing the liquid, where the change in refractive index is provided by the ambient atmosphere.

If used in an aquatic environment for example, a liquid-filled light guide may comprise a double wall comprising an inner wall containing the liquid and spaced apart from an outer wall, where the change in refractive index is provided by air, vacuum, or any number of transparent materials of a lower index of refraction than the inner liquid and filling the cavity formed by the spaced apart double walls. Alternatively, the cavity formed between the spaced-apart double walls may be filled with a gas, for example an inert gas such as nitrogen, carbon dioxide or argon as found in U.S. Pat. No. 4,420,796. In such a light conduit, the air or other gas provides an appropriate refractive index to guide light in the conduit.

In some embodiments, the first wavelength or wavelength range comprises ultraviolet or visible light and the second wavelength or wavelength range comprises visible light. In another embodiment, the first wavelength or wavelength range comprises green visible light and the second wavelength or wavelength range comprises red visible light. Typically, the first wavelength or wavelength range comprises about 500 nm to about 600 nm and the second wavelength or wavelength range comprises about 600 nm to about 700 nm.

By most estimates, algae systems have a maximum theoretical yield of 11% solar-photosynthetic efficiency. Photosynthesis can provide up to 40% efficiency for conversion of solar energy to glucose at the wavelengths at which chlorophyll absorbs, i.e. 420 nm and 650 nm (FIG. 1). At other wavelengths of the spectrum, however, photosynthesis is less than 1% efficient so that the whole spectrum averages between 5% to 10% efficiency. Up to 90% of all inefficiencies related to bioreactors for mass scale algae growth are related to incompatibility between the received solar radiation and the biologically optimal conditions for algae growth in terms of intensity and wavelength. The present disclosure addresses this incompatibility by promoting selective light absorbance through luminescent conversion of unused light to absorbable light, and thus may improve the solar efficiency of photosynthesis in a bioreactor or open pond.

The luminescent conversion of unused light to absorbable light may allow growth of algae or cyanobacteria at night or at depths at which light does not naturally penetrate.

In other embodiments, the first wavelength or wavelength range comprises ultraviolet light and the second wavelength or wavelength range comprises violet or blue visible light. Generally, the first wavelength or wavelength range comprises about 250 nm to about 400 nm and the second wavelength or wavelength range comprises about 400 nm to about 500 nm.

In further embodiments, the first wavelength or wavelength range comprises ultraviolet or blue light and the second wavelength or wavelength range comprises green, yellow, orange or red visible light. The first wavelength or wavelength range may comprise about 250 nm to about 400 nm and the second wavelength or wavelength range comprises about 450 nm to about 650 nm.

In further embodiments, the luminescent material comprises: a calcium sulfate phosphor; a zinc sulfate phosphor; a strontium aluminate phosphor; a calcium aluminate phosphor; a CaSrS phosphor; a CaS phosphor; or yttrium aluminium garnet (YAG, Y.sub.3Al.sub.5O.sub.12), terbium aluminium garnet (TAG, Tb.sub.3Al.sub.5O.sub.12), or Zex.

Alternatively, the luminescent material may comprise: a halogen-substituted, alkaline earth metal aluminate doped with at least one rare earth element activator, or a composition of: aL.bM.cAl.dSi.pP.O.:fR, wherein L is selected from Na and/or K; M is a divalent metal selected from one or more of the group consisting of Sr, Ca, Mg and Ba; Al, Si, P and O represent their respective elements; R is selected from one or more rare earth element activators; and wherein the variables a, b, c, d, p and f are: 0.0<a<0.1; 0.0<b<0.3; 0.0<c<0.4; 0.0<d<0.3; 0.0<p<0.5; and 0.0<f.ltoreq.0.25, with the proviso that at least one of the variables d and p is >0, and at least one of the variables a and b is >0.

Otherwise, the luminescent material may comprise: antimony-activated calcium fluorophosphate, lead-activated calcium tungstate, tin-activated strontium magnesium orthophosphate or manganese-activated magnesium fluorogermanate; yttrium and/or gadolinium oxides activated by trivalent europium and having the formula (Y.sub.aGd.sub.1-a).sub.2O.sub.3:Eu.sup.3+, preferably a=1; calcium- and terbium-activated aluminates, silicates, phosphates and borates selected from compounds of the formulae CeMgAl.sub.11O.sub.19:Tb Y.sub.2SiO.sub.5:Ce,Tb LaPO.sub.4:Ce,Tb LaMgB.sub.5O1.sub.0:Ce,Tb; or alkaline earth hexagonal aluminates of the B-alumina structure, or alkaline earth chlorophosphates, each activated by divalent europium and having the formula BaMgAl.sub.10O.sub.17:Eu.sup.2+ BaMg.sub.1.7Al.sub.20O.sub.32.7:Eu.sub.2+ BaMg.sub.2Al.sub.24O.sub.39:Eu.sub.2+ (Sr,Ca,Ba).sub.10Cl.sub.2(PO.sub.4).sub.6:Eu.sup.2+.

According to some embodiments, the luminescent material is disposed in or coated on a substrate. The substrate provides growing surfaces for the algae or cyanobacteria. The luminescent material may be disposed in or coated on one or more surfaces of the substrate. In certain embodiments, the substrate may comprise more than one luminescent material. If more than one substrate is present, the individual substrates may comprise different luminescent materials or the individual substrates may comprise more than one luminescent material. If more than one luminescent material is present, the luminescent materials may be separated or mixed.

In some embodiments, the substrate comprises a dielectric material. The dielectric material may comprise a polymer, glass, or quartz. The polymer may comprise acrylate or polycarbonate. In one embodiment, the polymer is polymethyl methacrylate. Quartz and certain polymers may be of benefit because they transmit UV light.

In one embodiment, the substrate is the luminescent material.

In one embodiment, the bioreactor includes a bank or storage cell comprising a further luminescent material for use in the bioreactor during the night or at depths not exposed to light. In one embodiment, such luminescent materials will have long glow times and provide low light levels necessary for heterotrophic, nocturnal growth of algae using any number of organic carbon sources as is known in the art.

In some embodiments, the luminescent material absorbs the first wavelength or wavelength range from sunlight. Alternatively, the luminescent material may absorb the first wavelength or wavelength range from an artificial light source, such as a fluorescent light.

In particular embodiments, the bioreactor utilises an industrial source of carbon dioxide. The industrial source of carbon dioxide may be post-combustion carbon dioxide, pre-combustion carbon dioxide, or flue gas, either treated or untreated. Post-combustion carbon dioxide may be isolated using a solvent, a membrane, a zeolite, or a cryogen. In some embodiments, the solvent is an amine. Typically, the solvent is monoethanolamine (MEA) or triethanolamine (TEA). In alternative embodiments, pre-combustion carbon dioxide may be isolated using integrated gasification combined cycle (IGCC). In some embodiments, IGCC produces hydrogen or syngas.

In another embodiment, the carbon dioxide is received as untreated flue gases and is absorbed by the algae growth medium kept at a basic pH where the algae take up inorganic carbon as anionic carbonates where algae species, such as Coccolithophores, known for their ability to take up calcium carbonates, are grown in the bioreactor or pond.

In another embodiment, the carbon dioxide is received from untreated flue gases from a power station utilising oxygen fired combustion where flue gases can be up to 95% carbon dioxide. Such systems may or may not use recycled flue gases to dilute the pure oxygen.

In other embodiments, the bioreactor utilises an agricultural source of carbon dioxide. For example, dairy effluent wastewater may be treated in a bio-digester to generate biogas, typically a mixture of methane and carbon dioxide. Emissions from combustion of the biogas may be used as a source of carbon dioxide for photosynthesis as well as the carbon dioxide component of the biogas itself. Alternatively, human wastewater or sewage, either treated or untreated, may be utilised.

In one embodiment, the bioreactor comprises, or is co-operative with, a bio-digester.

Persons skilled in the art will appreciate that suitable bioreactors, or bioreactors that may be suitably adapted, are known.

In some embodiments, the substrate may be filtered. Filtering enables isolation of the substrate for simple harvesting of the algae. In one embodiment, the algae or cyanobacteria may be harvested from the substrate. Harvesting may comprise wiping, scraping, washing, rinsing, drying or partially drying the algae or cyanobacteria, or altering the pH of the growth medium to disrupt binding of the algae.

In one embodiment, where algae are grown in water and are not bound to, a surface, harvesting is accomplished by preliminary concentration of the algae followed by aggregation and filtration or centrifugation. Preliminary concentration can be accomplished using sonic standing waves in a controlled containment that causes algae to concentrate at the nodes of the standing waves. The columns of concentrated algae can be diverted or separated from water with a lower concentration of algae. This concentrate can then be aggregated, filtrated, or centrifuged as is known in the art.

As used in the subject specification, the singular forms "a", "an" and "the" include plural aspects unless the context clearly dictates otherwise. Thus, for example, reference to "a luminescent material" includes a single luminescent material, as well as two or more luminescent materials and so forth.

As used herein, "acrylate" refers to a polymer, homopolymer or copolymer, derived from the monomer acrylic acid or its derivatives possessing one or more functional groups. Derivatives include, for example, methyl acrylate, ethyl acrylate, methacrylate and methyl methacrylate.

As used herein, "plant" and "plants" refer to the singular and plural forms of the word, respectively. "Plants" include any photosynthetic organism comprising chlorophyll, particularly chlorophyll a and chlorophyll b, that is not an alga or a cyanobacterium as herein defined. Generally, plants possess cellulose in their cell walls. Plants include trees, herbs, bushes, grasses, vines, ferns and mosses.

Plants may be ornamental, utilitarian or crop plants, including agriculture, horticulture, aquaculture and hydroponic crop plants, such as vegetables, forestry plants or fruit trees.

The plant may be terrestrial or aquatic.

The plant part may be a bud, a fruit, a seed, a flower, a leaf, a branch or a stem, or any other part that will benefit from light of the second wavelength or wavelength range emitted by the luminescent material.

As used herein, "alga" and "algae" refer to the singular and plural forms of the word, respectively. "Algae" lack the many distinct organs found in plants, but comprise a nucleus enclosed within a membrane and chloroplasts bound in one or more membranes. "Algae" are eukaryotic organisms that comprise chlorophyll that harvests sunlight for autotrophism via photosynthesis. Chlorophyll includes chlorophyll a, chlorophyll b, and chlorophyll c. Each of chlorophyll a, b, and c possess two major absorbance peaks in the electromagnetic spectrum: one near 420 nm and one near 650 nm (blue light and red light, respectively; FIG. 1). Chlorophyll has a lesser degree of absorbance of ultraviolet (UV), green, yellow, orange, or infrared light. "Algae" include Axodines, Bolidomonas, Brown algae, Charophyta, Cryptomonads, Diatoms, Dinoflagellates, Euglenids, Eustigmatophytes, Glaucophytes, Golden algae, Green algae, Heterokonts, Pelagophyceae, Phaetothamniophyceae, Pinguiophyceae, Prymnesiophyta, Raphidophytes, Red algae, Synurids, and Yellow-green algae. Microscopic algae and phytoplankton are particularly contemplated.

Photosynthetic algae are relatively simple and cost-effective to grow and maintain. Algae can grow photosynthetically using carbon dioxide and sunlight, plus a minimum amount of trace nutrients. They also can alternatively or additionally grow heterotrophically on another carbon source, such as glucose or sucrose, or waste water. They are generally regarded as environmentally friendly and safe for human operators.

Chlorophyll includes chlorophyll a, chlorophyll b, and chlorophyll c. Each of chlorophyll a, b, and c possess two major absorbance peaks in the electromagnetic spectrum: one near 420 nm and one near 650 nm (blue light and red light, respectively; FIG. 1). Chlorophyll has a lesser degree of absorbance of ultraviolet (UV), green, yellow, orange, or infrared light. Photosynthetic pigments in algae include chlorophyll a and chlorophyll b.

The luminescent material can be a useful tool for light-dependent growth process and can enhance the growth of any green plants as long as all physical nutrients are supplied.

Flowering plants, fruits, and vegetables can exhibit improved growth and quality by enhancement of other regions of the light spectrum.

For example, flowers are encouraged by larger amounts of far red light in the 650 nm to 750 nm region. This can be achieved using a far red-emitting luminescent material.

Fruits and vegetables contain carotenoids that give them distinctive colours such as the red compound, lycopene, found in tomatoes. Other carotenoids have yellow, orange and many other colours that can be seen in the range of colours of produce.

It is known that increases in particular wavelengths of light can encourage increased production of the compounds in plants that absorb those wavelengths. Red fruits can be made to be more red or even increase their size.

The greatest advantage of this technology is that it uses the sun as its only energy source.

Further advantages of the present disclosure include: conversion of light to usable wavelengths, rather than simple filtering of lesser used wavelengths; increased photosynthetic efficiency by conversion of light absorbed at a low level into light absorbed at a higher level; better use of available light; optimisation of light spectrum to better suit growth; ability to use a single light source with a single wavelength output at an energy equal to or higher than 400 nm in conjunction with luminescent material(s) that absorb and convert this high energy monochromatic light to create the entire range of wavelengths required for growth; light extractors for distribution of light; improved efficiency of open systems towards the efficiency of closed systems; utilisation of carbon dioxide from industrial and agricultural sources for photosynthesis.

The light extractor of the disclosure or the luminescent light guide of the disclosure may be incorporated into a surround for surrounding the plant or a part thereof, the alga or the cyanobacterium. The surround acts to emit light of the second wavelength or wavelength range to an individual plant or to a part thereof, for example, a flower as shown in FIG. 6, a bud or a blossom to encourage and improve the development of fruits, vegetables, or flowers.

In one embodiment of the surround, the technology can be used for growing wine grapes, in which lighting conditions are known to be particularly important. The lighting can be customised such that the grape colour and flavour may be fine-tuned by the increase or decrease of particular flavanoids, carotenoids, polyphenols etc.

Similarly, a surround may be applied to a seaweed or to algae or cyanobacteria grown in liquid medium.

If it is desired to direct the light of the second wavelength or wavelength range to one or a plurality of plants or seaweeds, or to algae or cyanobacteria, light extractor of the disclosure or the luminescent light guide of the disclosure may be incorporated into a cover for covering the plant or a part thereof, the alga or the cyanobacterium. For example, the cover may be draped above flowers, as shown in FIG. 7, or the cover may comprise a cover for an orchard, the cover being suspended over the fruit trees.

Similarly, light extractor of the disclosure or the luminescent light guide of the disclosure, the surround, or the cover may be incorporated into a greenhouse, a terrarium, a conservatory, herbarium, arboretum, nursery, or bioreactor. A plurality of light extractors of the disclosure or luminescent light guides of the disclosure, surrounds or covers may be used. For example, in one embodiment, a bioreactor may comprise a plurality of luminescent light guides. In another embodiment of a bioreactor, a plurality of covers may be used to cover an open pond-type bioreactor. Alternatively, a plurality of covers may be used in an orchard or to cover a greenhouse.

As used herein, "algae containment apparatus" refers to any container or vessel that supports a biologically active environment in which algae or cyanobacteria grow. An "algae containment apparatus" may also be suitable to grow aquatic plants.

An "algae containment apparatus" has no predetermined length other than that dictated by factors of practical engineering and includes tubes or tubular triangular shaped bags. An "algae containment apparatus" may be rigid or flexible. In one embodiment, an "algae containment apparatus" is a substrate.

The algae containment apparatus may be flexible. The algae containment apparatus may be tubular. The cross-section of the apparatus may be any useful geometry including circular, ellipsoid, square, rectangular, parabolic, triangular or any combination thereof. The algae containment apparatus may be tubular and triangular, e.g. parabolic in cross-section, with a base positioned away from the light and a vertex positioned towards the light. The algae containment apparatus may comprise piping with intermittent holes for delivery of gases comprising carbon dioxide. The algae containment apparatus may comprise a first light guide. The luminescent material of the algae containment apparatus may emit a second wavelength in the range of about 600 nm to about 700 nm, or may emit a second wavelength range of about 600 nm to about 700 nm. The algae containment apparatus may comprise diffusion particles.

As used herein, "bioreactor" refers to any device or system larger than and/or comprising an "algae containment apparatus" that supports a biologically active environment in which plants or part thereof, algae or cyanobacteria grow. A "bioreactor" may be an open system or a closed system. Thus, a "bioreactor" may include a pond, lake or raceway. Alternatively, a "bioreactor" may be a vessel. These vessel "bioreactors" are commonly cylindrical, ranging in size from liters to cubic meters, and are often made of stainless steel. Alternatively, a "bioreactor" may be made of concrete or a polymer. To be used as a bioreactor, a carbon source, an energy source and trace nutrients are required. For plants and photosynthetic algae or cyanobacteria, a carbon source is carbon dioxide, and an energy source is light, typically sunlight.

Persons skilled in the art will appreciate that suitable bioreactors, or bioreactors that may be suitably adapted, are known.

The bioreactor may comprise a plurality of algae containment apparatuses that may be positioned side by side. The bioreactor may further comprise a second light guide positioned on the containment. The second light guide of the bioreactor may comprise a luminescent material. The luminescent material may emit light comprising the range of about 540 nm and about 600 nm. The second light guide may comprise diffusion particles. The bioreactor may be an open pond or raceway.

As used herein, the term "greenhouse" refers to a structure used to grow plants including vegetables, herbs, flowers, legumes, fruits, vines and trees. In a typical greenhouse, enclosures are constructed to contain plant growth in ideal conditions usually free of pests, viruses and fungi. These enclosures also allow for control of lighting, moisture and humidity for any given plant. Accordingly, greenhouses allow controlled and dense growth. The term "greenhouse" includes a terrarium, a conservatory, herbarium, arboretum, or nursery.

The shape of a structure disclosed herein, including but not limited to an algae containment apparatus, a bioreactor or a greenhouse, for example, may be any shape or size, provided that it serves its purpose. A bioreactor may comprise a receptacle, a container, a vessel, a tank, a bag, a sac, a chamber, a reservoir, or a pond, for example. A greenhouse may comprise any useful cross-section such as a square, a rectangle, a circle, an ellipse, a triangle, a pentagon and so on.

Also disclosed herein is a method for improving a greenhouse or a bioreactor for growing a plant or part thereof, an alga or a cyanobacterium, comprising providing the greenhouse or bioreactor with light extractor of the disclosure or the luminescent light guide of the disclosure, the surround, or the cover.

The shallow depths at which traditional open pond algal systems operate to allow sufficient exposure to sunlight require large areas to obtain adequate algal growth. Bioreactors require smaller areas and allow larger volumes of algal growth, but suffer from the problem of restricted availability of light at depth.

The present apparatus and methods overcome this limitation by increasing the solar efficiency of algae grown in the bioreactor. Thus, more algae may be grown in a smaller volume of growth medium. Furthermore, the depth of the bioreactor may be up to 10 times greater than current designs and therefore would require 10 times less land area. Most importantly, due to the optimised light spectrum in the system, algae will be able to grow at higher concentrations within the bioreactor. Additionally, fewer materials and less transparent tubing should be required compared with current bioreactors.

In the claims that follow and in the description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features, but not to preclude the presence or addition of further features in various embodiments of the invention.

As used herein, "cyanobacterium" and "cyanobacteria" refer to the singular and plural forms of the word, respectively. "Cyanobacteria" are prokaryotic, photosynthetic organisms that are also know as blue-green algae, but are not true algae. In contrast to algae that employ chlorophyll for photosynthesis, "cyanobacteria" generally employ phycobilins to absorb light for photosynthesis. Phycobilins in "cyanobacteria" include phycoerythrin, phycocyanin and allophycocyanin. Phycobilins predominantly absorb light in the green/yellow/orange (and near red) region of the electromagnetic spectrum from about 500 nm to about 650 nm, a region that chlorophyll absorbs very poorly.

The term "dielectric" refers to a non-conducting substance.

As used herein, the term "conduit" or "light conduit" is used interchangeably with the term "light guide" and refers to any material or construct of multiple materials, solids or liquids, designed to transport light using internal reflection or total internal reflection. This internal reflection is dependant upon the indices of refraction of the materials involved where the materials are transparent or translucent. Fibre optics are the most common example of conduits, but larger systems such as sheets and columns of any unspecified width or length are also included.

As used herein, "doped" or "doping" refers to the process of intentionally introducing impurities ("dopants") into a pure material to change its optical properties, i.e. with respect to luminescence, i.e. fluorescence or phosphorescence. "Dopants" include rare-earth elements.

As used herein, "emit" or "emission" refer to discharging or issuing light energy from a luminescent material.

As used herein, the term "excite" or "excitation" refers to causing change to, or exerting influence on, the luminescent material, particularly to the absorption of light energy by the luminescent material. "Exciting" refers to charging the luminescent material by absorption of light energy in readiness for its later emission as visible light of longer wavelength.

The term "fluorescent" or "fluorescence" and the term "phosphorescent" or "phosphorescence" each refers to a class of luminescence in which energy, usually light energy, is absorbed by a material at one wavelength or within a window of wavelengths and is subsequently emitted by the material as energy of a longer wavelength, or lower energy. "Fluorescence" can be distinguished generally from "phosphorescence" based on the time scale of light emission from the material, with phosphorescence emission being longer than fluorescence, but more accurately defined by the distinct pathways in the photophysics of relaxation from light induced excited states. These photophysical differences are clearly defined and known.

As used herein, "luminescence" refers to fluorescence and/or phosphorescent.

As used herein, "emit" or "emission" refers to discharge or issuance of light energy from a luminescent material.

As used herein, the terms "absorb", "absorption", "excite" or "excitation" refers to causing change to, or exerting influence on, the luminescent material, particularly to the absorption of light energy by the luminescent material. "Absorbing" or "exciting" refers to charging the luminescent material by absorption of light energy in readiness for its later emission as visible light of longer wavelength. The term "absorption" refers to the physical process of absorbing light.

In contrast, and as used herein, "absorbance" refers to the mathematical quantity, as defined by Equation 1, of absorbed light.

As used herein, "growth medium" refers to any mixture of trace nutrients capable of sustaining growth of algae or cyanobacteria. An example of a growth medium is a solution including the following constituents (the concentration for each constituent is mg/L): NaNO.sub.3, 250; CaCl.sub.2.2H.sub.2O,25; MgSO.sub.4.7H.sub.2O,75; K.sub.2HPO.sub.4, 75; KH.sub.2PO.sub.4, 175; NaCl, 25; KOH, 31; FeSO.sub.4.7H.sub.2O,5.0; H.sub.3BO.sub.3, 11.4; ZnSO.sub.4.7H.sub.2O, 8.8;MnCl.sub.2.4H.sub.2O, 1.44; MoO.sub.3, 0.7; CuSO.sub.4.5H.sub.2O, 1.57; Co[NO.sub.3].sub.2.6H.sub.2O, 0.50 and EDTA, 50. Alternatively, a growth medium may comprise wastewater or seawater, either treated or untreated.

The term "polymer" refers to a large molecule built up by repetitive bonding of many smaller units called monomers. The term "polymer" includes both homo-polymers comprising one species of constituent monomer and co-polymers comprising more than one species of constituent monomer.

As used herein, "substrate" refers to any entity that provides a vehicle for the luminescent material and/or a growing surface for algae or cyanobacteria. Thus, in a vessel bioreactor for example, the substrate may include the walls and base of the bioreactor. In some embodiments, "substrate" refers to an entity distinct from the walls or base of the bioreactor that provides a vehicle for the luminescent material and/or growing surface for algae or cyanobacteria. In some embodiments, the algae containment apparatus or bioreactor is configured to prevent fouling of the substrate by direct contact with the algae. More than one "substrate" may be present in a bioreactor. In a particular embodiment, the "substrate" is the luminescent material.

The term "ultraviolet" or "UV" light refers to that portion of the solar electromagnetic spectrum subdivided as UVA, UVB, and UVC ranging from 400 to 100 nm.

The term "visible light" refers to that portion of the electromagnetic spectrum or photons visible to the naked eye, and is distinct from "ultraviolet" or "UV" light. This portion of the electromagnetic spectrum is typically regarded as falling between wavelengths of about 400 nm and about 750 nm.

Any luminescent material, which is capable of excitation by, or absorption of, light of a first wavelength or wavelength range and emission of visible light of a second wavelength or wavelength range longer than that of the first wavelength or wavelength range, can be used according to the present disclosure, provided that the emitted light is suitable for growing algae or cyanobacteria. In particular, light of the second wavelength or wavelength range should be absorbable by algae or cyanobacteria photosynthetic proteins or pigments, including chlorophyll a, chlorophyll b, chlorophyll c, and phycobilins such as phycoerythrin, phycocyanin and allophycocyanin.

The main characteristic driving selection of a luminescent material to be used is the emission wavelength of the material.

The luminescent material should be selected on the basis of the desire type of luminescence, i.e., fluorescence or phosphorescence.

Quantum efficiency may also be a characteristic driving selection of a luminescent material. Quantum efficiency should be of a magnitude sufficient to produce visible light suitable for photosynthesis.

The luminescent material should absorb light in the green region of the electromagnetic spectrum (about 500 nm to about 600 nm), a part of the spectrum largely unused by the chlorophyll pigments in algae. The luminescent material will absorb and use this energy to luminesce, or emit, red light between about 600 nm and about 700 nm, in one embodiment near 650 nm, which the algae can use extremely well for photosynthesis, and therefore growth.

The luminescent material may also exploit chlorophyll's absorbance peak in the electromagnetic spectrum near 420 nm. In this instance, the luminescent material should absorb UV radiation in the range of about 250 nm to about 400 nm and emit visible light in the region of about 400 nm to about 500 nm, in one embodiment near 420 nm, where such light is also used for photosynthesis.

In some embodiments, the luminescent material will absorb light from the UV and/or blue region, generally from about 250 nm to about 500 nm, and emit light in the green, yellow, orange or red region, generally from about 500 nm to about 650 nm, which may be then be absorbed by phycobilins of cyanobacteria and used for photosynthesis.

In one embodiment, more than one luminescent material may be present. For example, use of two luminescent materials, one that absorbs UV light and luminesces blue light and the other that absorbs green light and luminesces red light enables much more of the total solar spectrum to be used for photosynthesis in algae. Thus, the disclosure allows use of nearly all of the solar spectrum for photosynthesis, except for the infrared (IR) portion, although the IR portion may be used in cold climes for maintaining algal growth.

A luminescent material includes quite generally all inorganic, organic and organometallic materials capable of converting an input of absorbed photons into an output of photons of different energy, and the output comprises a visible light with a brightness and intensity sufficient for photosynthesis. The luminescent material may be coated on the substrate and/or may be disposed in or contained in the substrate.

In one embodiment, the luminescent material may be any inorganic luminescent compound. In one embodiment, the inorganic luminescent compound may comprise a rare-earth doped inorganic crystal or a doped zinc sulphide. In another embodiment, the luminescent material may be any organic luminescent compound. In yet another embodiment, the luminescent material may comprise a quantum dot. In one embodiment, the luminescent material may be any organometallic luminescent compound.

The luminescent material may be, for example, a commercially available luminescent pigment or luminescent dye.

Examples of the luminescent (phosphorescent) material used include, but are not limited to, calcium sulfate phosphors (host crystal: CaS; activator: Bi); zinc sulfate phosphors (host crystal: ZnS; activator: Cu, e.g. "GSS" manufactured by Nemoto & Co., Ltd.); strontium aluminate or calcium aluminate phosphors (host crystal: strontium aluminate or calcium aluminate; activator: Eu, Dy, Nd, or the like; e.g. VGS-FAP or VGS3-FAP series manufactured by Visionglow International Pty Ltd; LumiNova.RTM. G-300 series, BG-300 series, and V-300 series, manufactured by Nemoto & Co., Ltd.; "ULTRA GLOW series" NP-2810, NP-2820, and NP-2830, manufactured by Nichia Corporation; "R-bright" B and YG, manufactured by Lead Co., Ltd.; "Chemibright Powder" G-40-C, G-100-B, G-100-C, GB-80-B, and B-50-B, manufactured by Lumica Corporation); phosphors containing CaSrS, as a host crystal, and Bi, as an activator; and phosphors containing CaS, as a host crystal, and Eu or Tm, as an activator. Examples of suitable phosphorescent materials also include yttrium aluminium garnet (YAG, Y.sub.3Al.sub.5O.sub.12), terbium aluminium garnet (TAG, Tb.sub.3Al.sub.5O.sub.12), and Zex, which can emit a yellow light having a wavelength in the range of 530 to 590 nm.

Examples of the luminescent (phosphorescent) material used include, but are not limited to, calcium sulfate phosphors (host crystal: CaS; activator: Bi); zinc sulfate phosphors (host crystal: ZnS; activator: Cu, e.g. "GSS" manufactured by Nemoto & Co., Ltd.); strontium aluminate or calcium aluminate phosphors (host crystal: strontium aluminate or calcium aluminate; activator: Eu, Dy, Nd, or the like; e.g. VGS-FAP or VGS3-FAP series manufactured by Visionglow International Pty Ltd; LUMINOVA.RTM. G-300 series, BG-300 series, and V-300 series, manufactured by Nemoto & Co., Ltd.; "ULTRA GLOW series" NP-2810, NP-2820, and NP-2830, manufactured by Nichia Corporation; "R-bright" B and YG, manufactured by Lead Co., Ltd.; "Chemibright Powder" G-40-C, G-100-B, G-100-C, GB-80-B, and B-50-B, manufactured by Lumica Corporation); phosphors containing CaSrS, as a host crystal, and Bi, as an activator; and phosphors containing CaS, as a host crystal, and Eu or Tm, as an activator. Examples of suitable phosphorescent materials also include yttrium aluminium garnet (YAG, Y.sub.3A1.sub.5O.sub.12), terbium aluminium garnet (TAG, Tb.sub.3A1.sub.5O.sub.12), and Zex, which can emit a yellow light having a wavelength in the range of 530 to 590 nm.

If the structure of the fluorescent material has the stilbene moiety, or the distyrylbiphenyl moiety, any chromophore groups, such as methoxyphenyl group, anthracene group, pyrene group, or 9,10-anthraquinone group, can be symmetrically bonded to such a stilbene moiety or distyrylbiphenyl moiety for enhancing brightness. Examples of such fluorescent materials include, but are not limited to, 4,4'-bis(2-methoxystyryl)biphenyl, 4,4'-bis{2-(9-anthracenyl)ethylenyl}biphenyl, 4,4'-bis(2-(1-yrenyl) ethylenyl)biphenyl, and 4,4'-bis(2-(1-anthraquinonyl)ethylenyl)biphenyl. When 4,4'-bis(2-methoxystyryl)biphenyl is used as the fluorescent material, it can be excited by UV light and subsequently emits a blue light having a wavelength between 450 nm and 490 nm. When 4,4'-bis{2-(9-anthracenyl)ethylenyl}biphenyl is used as the fluorescent material, it can be excited by UV light and subsequently emits a yellowish-green light having a wavelength between 520 nm and 550 nm. When 4,4'-bis{2-(1-pyrenyl)ethylenyl}biphenyl is used as the fluorescent material, it can be excited by UV light and subsequently emits a blue light having a wavelength between 450 nm and 490 nm. When 4,4'-bis{2-(1-anthraquinonyl)ethylenyl}biphenyl is used as the fluorescent material, it can be excited by UV light and subsequently emits a red light having a wavelength between 580 nm and 660 nm. In order to increase the brightness, a blue phosphor may be used with 4,4'-bis(2-methoxystyryl)biphenyl, or 4,4'-bis{2-(1-pyrenyl)ethylenyl}biphenyl to convert the emission to a blue light; a yellowish green phosphor may be used with 4,4'-bis{2-(9-anthracenyl)ethylenyl}biphenyl to convert the emission to a yellowish green light; and a red phosphor may be used with 4,4'-bis{2-(1-anthraquinonyl)ethylenyl}biphenyl to convert the emission to a red light.

The particle size of the luminescent material embedded in the substrate is not particularly limited, though it may comprise particles with an average diameter of 10 nm to 10 .mu.m. If the luminescent material has an average particle diameter below 10 nm, it exhibits poor durability and significantly decreased brightness. If the luminescent material has an average particle diameter above 10 .mu.m, greater visible light scattering arises. In the case of non-mineral luminescent materials that do not depend on a crystal lattice for their luminescent processes, as in most fluorescent dyes, the material can be fully dispersed or dissolved into the substrate as individual molecules absorbing light and subsequently luminescing.

Any lighting source that emits light of a wavelength that is suitable for energising the luminescent material may be used as an energy source. The source may be the sun, an incandescent device, a halogen device, or a fluorescent device. The device may be fluorescent such as bulb, globe or tube. In some embodiments, light is derived from sunlight.

The luminescent material may absorb light prior to algal absorption of light, since algal growth may impede absorbance of light by the luminescent material. The luminescent material may possess an emission period of sufficient duration to enable optimal algal absorption prior to abatement of the luminescence.

Any lighting source that emits light of a wavelength that is suitable for energising the luminescent material may be used as an energy source. The energy source may be solar or artificial. The artificial light source may be an incandescent device, a halogen device, or a fluorescent device. The device may be fluorescent such as bulb, globe or tube.

In one embodiment, the artificial energy source may be a low energy UV fluorescent bulb, often known as a "black light" that has a single emission peak near 370 nm. The luminescent growing apparatus may comprise one layer with a mixture of luminescent materials or individual layers with each luminescent material separately disposed. The luminescent materials absorb well the 370 nm light from the black light and may provide emission peaks in the blue, red and/or any other desired wavelength ranges for optimal plant growth. The luminescent growing apparatus may contain multiple light extractors that allow the emitted light to be dispersed.

In some embodiments, the luminescent material is disposed in or coated on a substrate. Thus, the substrate may emit light to the algae or cyanobacteria.

Algae or cyanobacteria may grow on a surface. The surface may be provided by the luminescent material. Alternatively, the surface may be provided by a substrate.

The substrate may be any shape that is amenable to exposure to light and provides a surface for growth of algae. Thus, shape selection will largely be driven by these considerations.

The substrate may be regular or irregular in shape. The dimensions may be equal or unequal and may or may not be in proportion. The substrate may be solid, hollow, porous, or laminar, for example. The substrate may comprise more than one material.

If more than one substrate is present, the substrates need not be homogenous; the substrates may include any combination of shapes or sizes or compositions of individual substrates.

The main characteristics driving selection of a substrate to be used according to the disclosure include high surface area, transmission of UV light, stable to sunlight or UV light, approximate neutral buoyancy in water, and durability.

The substrates may be arranged in close proximity to enable high concentrations of algae to be grown in relatively small volumes. The substrates may be arranged as closely packed layers or in an array. Alternatively, the substrates may not be in any fixed orientation and may circulate through the bioreactor randomly. The substrate may be a whole continuous surface or freely moving pieces of any range of sizes, shapes or composition. The substrates may be circulated by any appropriate mechanism that allows exposure to a fixed light source, such as sunlight or conduits, for example. Circulation may be achieved by bubbler, injector, pump, blade, impeller, jet, nozzle, stirrer, or shaker, for example.

The substrate may comprise a dielectric material. The dielectric material may comprise a polymer, glass, or quartz. In one embodiment, the polymer comprises acrylate or polycarbonate. In one embodiment, the polymer is polymethyl methacrylate or polycarbonate. In one embodiment, the polymer is polymethyl methacrylate.

In one embodiment, the luminescent material is disposed in a polymer. In another embodiment, the luminescent material is coated on a polymer substrate. The polymer may comprise: an acrylic, a urethane; an ester; a methacrylate; a thiophene; a co-polymer of any bond conjugated polymer; a light transparent polymer; a low ultra violet absorbent polymer; a heat conducting polymer; or an electrically conducting polymer. In another embodiment, the polymer may be: aniline based; pyrrole based; acetylene based; or furan based.

In another embodiment, the polymer may comprise polyurethane, polyester, polyamide, polyurea, polycarbonate and polymethyl methacrylate. The constituent monomers in the polymers of the present disclosure may be methacrylate-based, carbonate-based, acrylamide-based, methacrylamide-based, or styrene-based monomers.

Constituent monomers of the vinyl polymers that may be used include acrylic esters, specifically, e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, tert-octyl acrylate, 2-chloroethyl acrylate, 2-bromoethyl acrylate, 4-chlorobutyl acrylate, cyanoethyl acrylate, 2-acetoxyethyl acrylate, dimethylaminoethyl acrylate, benzyl acrylate, methoxybenzyl acrylate, 2-chlorocyclohexyl acrylate, cyclohexyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, phenyl acrylate, 5-hydroxypentyl acrylat

» Number: 8,551,769

» Publication Date: 08/10/2013

» Applicant: Zero Discharge Pty Ltd. (Prahran, Victoria, AU)

» Inventor: Falber; Alexander (Bellevue Hill, AU)

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