WO2018115339A1

WO2018115339A1 - Structure for cultivating macroalgae

Info

Publication number: WO2018115339A1
Application number: PCT/EP2017/084197
Authority: WO
Inventors: Bert Groenendaal; Patrice Vandendaele
Original assignee: Atsea Technologies N.V.
Priority date: 2016-12-23
Filing date: 2017-12-21
Publication date: 2018-06-28
Also published as: BE1024510B1; EP3559198A1

Abstract

The invention relates to a structure for cultivating macro-algae. The structure comprises a multidimensional substrate and a wire system comprising a number of wires. The wire system is connected to the multidimensional substrate. The wire system comprises a very open structure. The invention further relates to the use of such a structure for the cultivation of macroalgae, to a method for cultivating macroalgae and to a method for making a structure for the cultivation of macroalgae.

Description

Structure for cultivating macroalgae

[0001] The invention relates to a structure for cultivating macroalgae. The structure according to the invention comprises a multidimensional substrate provided with an open wire system. The invention further relates to the use of a structure for the cultivation of macroalgae, to a method for cultivating macroalgae and to a method for producing a structure for cultivating macroalgae.

Background

[0002] Cultivating algae such as macroalgae has become more important in recent years since macroalgae are considered as a promising resource for the future. Macroalgae are amongst others used for food or feed, as additives for food or feed, as raw materials for biofuels, as raw materials for pharmaceutical products or as raw materials for (bio) materials. Cultivating algae has many advantages. Compared to the cultivation of plants on land, the cultivation of macroalgae leads to higher productivity. In addition no scarce farmland or freshwater is needed and no additional nutrients are needed for the cultivation of macroalgae. Furthermore, macroalgae can make an important contribution to protecting or increasing the marine biodiversity.

[0003] Various methods are known for cultivating macroalgae. A first method involves the cultivation of macroalgae on ropes. In such method macroalgae are sown on a rope or cuttings of macroalgae are placed between the strands of a rope. The ropes are then placed in the sea or ocean by, for example by securing them to a float, to the seabed or to other objects such as a windmill. Attaching the cuttings of macroalgae requires a manual process that is time-consuming and expensive. In addition, a minimum distance (usually a few meters distance) between consecutive ropes is needed to ensure that neighboring ropes do not interact with one another, for example in case of a storm and/or strong currents. As a result, the yield of macroalgae per unit area is limited.

[0004] In recent years, a method has been proposed in which the cuttings of macroalgae are placed in tubular nets which are then placed in the sea or ocean. Even though the process for placing the cuttings in the tubular nets is less time-consuming than placing cuttings of macroalgae in or on ropes, the yield per unit obtained by this method is limited since this method also requires a minimum distance (usually a few meters distance) between consecutive tubular nets. [0005] Another method for cultivating macroalgae comprises the growing of macroalgae on two-dimensional mats or cloths. Microscopic small juvenile seaweed plants are thereby applied to a mat or cloth, for example by immersing a mat or cloth in a container with juvenile seaweed plants or by spraying a solution or suspension containing juvenile seaweed plants on the cloth or mat. However, this method can only be used for a limited number of seaweed species.

[0006] There is thus a need for improved methods for cultivating macroalgae which make the cultivation of macroalgae economically profitable. Description of the invention

[0007] It is an object of the invention to provide an improved structure for cultivating macroalgae.

It is another object of the invention to provide a structure for cultivating macroalgae allowing to obtain a high yield of macroalgae per surface unit.

It is a further object of the invention to provide a structure for cultivating macroalgae which enables seaweed cuttings to be applied efficiently to the structure.

It is also an object of the invention to provide a method for cultivating macroalgae.

[0008] A first aspect of the invention relates to a structure for cultivating macroalgae. The structure comprises

a multidimensional substrate comprising a first side and a second side, a wire system comprising several wires, the wire system is connected to the first side or to the second side of the multidimensional substrate and is forming a multidimensional wire system extending over a surface A of the multidimensional substrate, i.e. over a surface area A of the side of the multidimensional substrate to which the wire system is connected, i.e. the first side or the second side. When the wire system is connected to the multidimensional substrate, the majority of the surface A of the multidimensional substrate is not covered by the wires. Preferably, at least 70% of the surface A of the multidimensional substrate is not covered by the wires of the multidimensional wire system.

The wire system is preferably connected to the multidimensional substrate. Preferably, the wire system and/or the wires of the multidimensional wire system is/are connected at predetermined connection spots to the multidimensional substrate.

[0009] In particular embodiments, a wire system (a first wire system) is connected to the the first side and a wire system (a second wire system) is connected to the second side of the multidimensional substrate. The wire system that is connected to the first side (the first wire system) and the wire system connected to the second side (the second wire system) can be identical wire systems or can be different. [0010] With the term "multidimensional" two-dimensional or three-dimensional is meant.

A two-dimensional structure is characterized by a length and a width; a three-dimensional structure is characterized by a length, a width and a thickness.

A multidimensional substrate comprises a two-dimensional substrate (characterized by a length and a width) or a three-dimensional substrate (characterized by a length, a width and a thickness). A multidimensional filament comprises a two-dimensional filament (characterized by a length and a width) or a three-dimensional filament (characterized by a length, a width and a thickness). [0011] As substrate, any substrate that allows the connection of wire systems can be considered. The substrate preferably comprises a predominantly flat substrate having a first side and a second side, such as for instance an upper side and a lower side or a left side and a right side. [0012] The substrate is preferably a flexible substrate. With the term "flexible substrate" a substrate that is bendable or pliable is meant. [0013] The substrate may comprise a plastic material, a natural material or a combination thereof. As plastic material, polyethylene, polypropylene, polyester, polyamide, polyvinyl alcohol, polyvinyl chloride, polyurethane, polyethylene terephthalate, polyacrylate, polycarbonate, polyvinylidene fluoride, polylactic acid, blends and block polymers thereof or combinations thereof can be considered. Bio-based polymers such as bio-poylethylene terephthalate or bio-polyethylene can also be considered as plastic material.

As natural material, flax, jute, cotton, sisal, bamboo and combinations of these can be considered.

[0014] In preferred embodiments, the substrate is biocompatible and/or biodegradable.

[0015] The multidimensional substrate may comprise one substrate or a combination of substrates, such as, for example, a layered structure comprising several layers.

[0016] The multidimensional substrate or one of the layers of the multidimensional substrate may or may not be provided with one or more coating layers, such as, for example, a UV stabilizing coating layer, a hydrophilic coating layer, a hydrophobic coating layer or a combination thereof.

[0017] A suitable multidimensional substrate comprises, for example, a film, a foil, a mesh, a textile structure or a combination thereof.

In preferred embodiments the multidimensional substrate comprises a textile structure such as, for example, a woven structure, a non-woven structure, a knitted structure, a braided structure or a combination of one or more such structures.

[0018] In preferred embodiments, the multidimensional substrate reflects a high amount of the incident light. A structure for cultivating macroalgae comprising a multidimensional substrate with a high light reflection has the advantage that it allows the macroalgae applied on or to the structure to absorb more light. The light which is reflected by the multidimensional substrate can in fact again reach the macroalgae applied to or on the structure according to the invention. The amount of light absorbed by the macroalgae has a positive effect on the growth of the macroalgae.

To determine the degree of light refiection, the percentage of light in a given wavelength range, typically in the wavelength range from 400 nm to 700 nm, that is reflected is measured. For example, the multidimensional substrate according to the invention has a degree of light refiection of light having a wavelength between 400 nm and 700 nm of at least 50%. This means that at least 50% of the light with a wavelength between 400 nm and 700 nm is reflected by the multidimensional substrate. In other preferred embodiments the multidimensional substrate has a degree of reflection of light having a wavelength between 400 nm and 700 nm of at least 60%, at least 70%, at least 80%, at least 90% or at least 95%.

In certain embodiments, the multidimensional substrate comprises a white substrate. In alternative embodiments, the multidimensional substrate may be provided with a highly reflective coating. It is of course also possible that the multidimensional substrate comprises a white substrate which is provided with a reflective coating.

[0019] It can be preferred to have a multidimensional substrate with a large specific surface area, for example a specific surface area that is greater than 1 m² per m² of the multidimensional substrate. More preferably, the specific surface is larger than 5 m² per m² of substrate, such as for instance a specific surface area between 5 m² and 1000 m² per m² of substrate, for example between 10 m² and 500 m² per m² of substrate, for example 100 m², 200 m², 300 m² or 400 m² per m² of substrate. A multidimensional substrate with a high specific surface area increases the degree of light reflection of incident light. As mentioned above, a high degree of light refiection has a positive effect on the growth and productivity of the macroalgae.

[0020] The multidimensional substrate preferably has a pore size between 10 μιη and 1500 μιη, more preferably between 25 μιη and 500 μιη, such as for example 50 μιη, 75 μιη, 100 μιη, 200 μιη, 300 μιη or 400 μιη. [0021] Before being connected to the multidimensional substrate, the wire system can consist of a single structure, such as for instance a knitted, braided, knotted, welded or woven structure, mesh or net.

In preferred embodiments, the wire system comprises a knitted, braided, knotted, welded or woven net.

In other embodiments, the wire system comprises - prior to being connected to the multidimensional substrate - of loose wires, i.e. wires that do not consitute a selfsupporting wire system. For example, a wire system includes a group of parallel or predominantly parallel wires.

[0022] Any elongated element can be considered as wire. Examples comprise a filament, a cord, a cable, a wire, a ribbon or combinations thereof.

[0023] The wires of the wire structure preferably have a diameter or equivalent diameter ranging between 0.1 mm and 50 mm, for example between 0.5 mm and 10 mm, for example 2 mm. The different wires of the wire structure can have the same diameter. In other embodiments, a wire structure comprises wires having different diameter.

[0024] The wires may comprise a plastic material, a natural material or a combination thereof. As plastic material, polyethylene, polypropylene, polyester, polyamide, polyvinyl alcohol, polyvinyl chloride, polyurethane, polyethylene terephthalate, polyacrylate, polycarbonate, polyvinylidene fluoride, polylactic acid, blends and block polymers thereof or combinations thereof can be considered. Bio-based polymers such as bio-poylethylene terephthalate or bio-polyethylene can also be considered.

As natural material, flax, jute, cotton, sisal, bamboo and combinations thereof can be considered.

The different wires of the wire structure may comprise the same material. In other embodiments, the wire structure may comprise wires of a different material. [0025] In preferred embodiments the wires of the wire system are biocompatible and/or biodegradable. [0026] The wires of the wire system and/or the wire system may or may not be provided with one or more coating layers, such as for instance a UV stabilizing coating layer, a hydrophilic coating layer, a hydrophobic coating layer or a combination thereof.

[0027] In preferred embodiments, the wires comprise polyethylene, polypropylene, polyester or polyamide filaments or cords.

[0028] The wires of the wire system may comprise the same material as the multidimensional substrate. In alternative embodiments, the wires of the wire system and the multidimensional substrate comprise different materials.

[0029] The wires of the wire system or the wire system are/is preferably partially connected to the multidimensional substrate.

With the term "connecting" is meant within the context of this invention any way in which the wires of the wire system or the wire system are/is at least partially connected, attached, bonded or joined to or with the multidimensional substrate. Connecting thus includes bonding, joining, gluing, sticking, laminating, etc. Preferred techniques for connecting the wires or the wire system to the multidimensional substrate comprise mechanical methods, thermal methods, chemical methods or combinations of one or more of these methods. Mechanical methods comprise for example, stitching, embroidery, knitting or knotting or combinations thereof. Chemical methods comprise for example gluing. Thermal methods comprise for example heating and melting the wires or wire system and/or the heating and melting the multidimensional substrate, preferably followe by applying pressure to connect the wires or the wire system to the multidimensional substrate.

[0030] In preferred embodiments, the wires of the wire system are mechanically connected to the multidimensional substrate, for example by stitching or embroidery. [0031] By "partially connecting to the multidimensional substrate" is meant that certain parts of the the wires of the wire system or certain parts of the wire system are connected to the multidimensional substrate while other parts of the wires of the wire system or of the wire system are not connected to the multidimensional substrate.

[0032] Preferably, the wires of the wire system are connected to the multidimensional substrate at predetermined locations, called the connection spots. There is preferably a minimum distance between consecutive connection spots. As a result, the wire system can be partially moved, i.e. the wire system is partially displaceable, with respect to the multidimensional substrate. Because the wire system can be partially moved or displaced with respect to the multidimensional substrate, cuttings of the macroalgae can be connected to the structure for cultivating algae, for instance by placing the cuttings of the macroalgae between the wire system and the multidimensional substrate, or by connecting the cuttings to or around the wires of the wire system.

[0033] The distance between two consecutive connection spots varies for example between 0.1 cm and 1000 cm, for example between 1 cm and 200 cm, between 1 cm and 100 cm, between 10 cm and 100 cm, such as for example 20 cm, 30 cm, 40 cm, 50 cm, 60 cm or 70 cm.

[0034] In certain embodiments, the wires of the wire system are connected to the multidimensional substrate at certain points, the connection points, for example by stitching or embroidery. The distance between two successive connection points varies, for example, between 0.1 cm and 1000 cm, for example between 1 cm and 200 cm, between 1 cm and 100 cm, between 10 cm and 100 cm, such as for example 20 cm, 30 cm, 40 cm, 50 cm, 60 cm or 70 cm.

[0035] The mutual distance between consecutive connection points may be constant throughout the structure or may vary over the structure. In certain embodiments, in some zones of the structure the mutual distance between consecutive connection points is smaller than in other zones . [0036] In other embodiments, the wires of the wire system are connected to the multidimensional substrate by connecting the wire system according to certain lines, the connecting lines, to the multidimensional substrate, for example by stitching or embroidering. These lines are oriented, for example, according to the longitudinal direction or according to the width direction of the multidimensional substrate. Alternatively, the lines are oriented according to the length and width direction of the multidimensional substrate. Of course, it is also possible that these lines are oriented in a direction that does not correspond to the longitudinal direction or the width direction of the multidimensional substrate.

For example, the distance between two consecutive connection lines varies between 0.1 and 1000 cm. In certain embodiments, the distance between two consecutive connection lines varies between 1 cm and 200 cm, for example between 1 cm and 100 cm or between 10 cm and 100 cm, such as for example 20 cm, 30 cm, 40 cm, 50 cm, 60 cm or 70 cm.

[0037] The mutual distance between consecutive connection lines can be constant over the entire structure or can vary over the structure. In certain embodiments in some zones of the structure the mutual distance between consecutive connection lines is smaller than in other zones.

[0038] The multidimensional wire system of a structure according to the invention preferably has a very open structure. Preferably, the major part of the surface A of the multidimensional substrate is not covered by the wires of the multidimensional wire system. In preferred embodiments at least 70 %, at least 75 %, at least 80 %, at least 90%, at least 92%, at least 95% or at least 97% of the surface A of the multidimensional substrate is not covered by the wires of the multidimensional wire system.

[0039] Because the wire system has a very open structure, a high amount of incident light reaches the macroalgae. This is important since macroalgae use photosynthesis to produce energy and carbohydrates. A high amount of incident light that reaches the macroalgae has a positive effect on the growth and productivity of the macroalgae. [0040] The distance between consecutive wires of the wire system preferably varies between 1 cm and 50 cm. In preferred embodiments the distance between two consecutive wires varies between 2 cm and 50 cm or between 5 cm and 20 cm, such as for example between 5 cm and 15 cm or between 7 cm and 12 cm, such as for example 8 cm or 10 cm. When the algae are connected to or around the wires of the wire system, the distance between consecutive cuttings of macroalgae can be determined by choosing the distance between consecutive wires.

By choosing the distance between consecutive wires, the yield per unit area can be optimized.

[0041] The mutual distance between consecutive wires of the wire system can be constant over the entire wire system.

In other embodiments, the mutual distance between consecutive wires is not constant over the entire wire system. The wire system has, for example, zones in which the wires are placed at a short distance from each other and zones in which the wires are placed at a greater distance from each other. A short distance between consecutive wires corresponds for example with a distance of 1 to 20 cm, for example a distance of 2 cm to 20 cm or a distance of 5 to 15 cm, such as for instance 7 cm, 8 cm, 10 cm or 12 cm. A longer distance between consecutive wires corresponds for example with a distance greater than 10 cm, for example a distance of 20 to 50 cm, for instance a distance of 25 cm, 30 cm or 40 cm. Structures having a wire system combining zones where the wires are positioned at a short distance and zones where the wires are positioned at a larger distance are particularly suitable for cultivating different types of macroalgae on one structure, for example for a combination of macroalgae that allow to be placed at short mutual distance and macroalgae that require a greater mutual distance.

[0042] In a preferred embodiment, the wire system comprises a mesh net with meshes, such as, for example, square meshes or diamond meshes. The size of the meshes preferably varies between 5 cm and 50 cm, for example between 5 cm and 20 cm, between 5 cm and 15 cm or between 7 cm and 12 cm, such as for example 8 cm or 10 cm. [0043] The wire system may comprise a net with constant mesh size over the entire network.

In other embodiments, the wire system comprises a net with meshes of different mesh sizes. For example, the wire system may include a net having zones with meshes with a small mesh size and zones with meshes having a larger mesh size. The zones with a small mesh size have, for example, a mesh size between 2 cm and 20 cm, such as for example between 5 cm and 15 cm or between 7 cm and 12 cm, such as for example 8 cm or 12 cm. For example, the areas with meshes with a larger mesh size have a mesh size greater than 10 cm, such as a mesh size of 20 cm, 25 cm, 30 cm, 40 cm or 50 cm.

Structures with a wire system comprising zones with different mesh sizes are particularly suitable for cultivating different types of macroalgae on one structure, for example for a combination of macroalgae which can be placed at a short distance from each other and macroalgae requiring a greater mutual distance.

[0044] The structure for cultivating macroalgae according to the invention comprising the multidimensional substrate and the wire system is preferably a flexible structure. By "flexible structure" a structure that is bendable or pliable is meant. [0045] Preferably, the wire system extends over an area A which is at least 60% of the area of the first side of the multidimensional substrate in case the wire system is connected to the first side of the multidimensional substrate or the wire system extends over an area A which is at least 60% of the area of the second side of the multidimensional substrate if the wire system is connected to the second side of the multidimensional substrate. With 'extending over a surface A' is meant that the multidimensional substrate spreads over an area A. The circumference of the wire system thus determines the area A.

In preferred embodiments the wire system over an area A which is at least 70%, at least 80% or at least 90% of the area of the first side or of the second side of the multidimensional substrate. It is clear that the wire system can also extend over the entire surface of the first side or of the second side of the multidimensional substrate. In this case, the area A is 100% of the area of the first side or of the second side of the multidimensional substrate. [0046] The structure according to the invention allows to cultivate macroalgae by means of a multidimensional, for instance a two-dimensional or three-dimensional structure, by applying cuttings of macroalgae on or to the structure. The cuttings of macroalgae can be applied in a simple and time-efficient manner. As mentioned above, techniques are known in the prior art in which cuttings of macroalgae are applied to one-dimensional structures by applying the cuttings of macroalgae between the strands of a cord. This technique is time-consuming and expensive and the yield per surface unit is limited. After all, a minimum distance (usually a few meters distance) between consecutive ropes must be respected to ensure that adjacent ropes do not interact with each other, for example in the event of a storm and/or strong current. As a result, the yield of macroalgae per unit area is limited.

The structures according to the invention allow to immobilize cuttings of macroalgae in an efficient manner with a higher yield per surface unit.

Due to the very open structure of the wire system, the incident light can reach the macroalgae almost unhindered. The amount of incident light on the macroalgae is important as it has a positive effect on the growth and productivity of the macroalgae.

[0047] A second aspect of the invention relates to a method for cultivating macroalgae. The method includes the following steps

- providing a structure for cultivating macroalgae as described above;

applying cuttings of macroalgae to the structure for the cultivation of macroalgae.

[0048] Any method that allows the cuttings of macroalgae to be applied to the structure for the cultivation of macroalgae, to be fixed or connected, can be considered. For example, the cuttings are connected to the wires of the wire system, for example, by knotting the cuttings on the wires or by wrapping the cuttings around the wires of the wire system.

According to an alternative method, the cuttings of the macroalgae are placed between the multidimensional substrate and the wire system. The cuttings are immobilized in this way. Macroalgae with a branched structure have the advantage that they provide good immobilization. For example, the cuttings of macroalgae have a weight ranging from 10 g to 100 g, such as, for example, 10 g, 20 g, 30 g, 40 g, 50 g, 70 g, 90 g or 100 g.

[0049] The mutual distance between adjacent cuttings of macroalgae preferably varies between 1 cm and 50 cm, for example between 2 cm and 30 cm, such as for example 8 cm, 10 cm, 12 cm, 15 cm, 20 cm or 25 cm.

The preferred mutual distance between adjacent cuttings depends, for example, on the type of macroalgae.

[0050] A third aspect of the invention relates to the use of a structure as described above for the cultivation of macroalgae. The structure according to the invention is particularly suitable for cultivating the following macroalgae : Eucheuma cottonii, Eucheuma spinosum, Eucheuma denticulatum, Gracilaria and Gelidium.

[0051] A fourth aspect of the invention relates to a method to manufacture a structure for cultivating macroalgae as described above. The method includes the following steps:

- providing a multidimensional substrate comprising a first side and a second side;

- providing wires or providing a wire system;

connecting the wires or the wire system to the multidimensional substrate at predetermined locations along the first side or the second side of the multidimensional substrate.

[0052] In particular embodiments, both sides of the multidimensional substrate, i.e. both the first side and the second side, are provided with a wire system by connecting wires or the wire system on the first side and on the second side of the multidimensional substrate.

[0053] According to a first method, the wire system may comprise a structure as such, i.e. a self-supporting structure, this structure is then connected to the multidimensional substrate. The wire system can be attached to the multidimensional substrate in the above- described ways. [0054] According to a second method, the wire system consists of individual wires and the individual wires are connected to the multidimensional substrate. The wires can be connected to the multidimensional substrate in the above-described ways.

Brief description of the figures

[0055] The invention is now illustrated with reference to the embodiments shown in the figures in which :

Figure 1 shows a schematic illustration of a first embodiment of a structure for cultivating macro algae according to the invention;

Figure 2 shows a schematic illustration of a second embodiment of a structure for cultivating macro algae according to the invention.

Detailed description of the embodiments

[0056] The following terms are explained in more detail with the purpose to further illustrate the invention :

macroalgae (also called seaweed, macrophytic algae) are multicellular plant-like organisms. They include a thallus (the body) and usually a root-like attachment organ. Macroalgae use photosynthesis to produce energy and carbohydrates. They include green algae (Chlorophyta), red algae (Rhodophyta) and brown algae (Phaeophyta). Examples of green algae include Enteromorpha and Monostroma, examples of red algae include Eucheuma, Gracilaria Porphyra and Kappaphycus, examples of brown algae include Laminaria japonica and Undaria pinnatifida. Cuttings of macroalgae (also called seaweed cuttings) are parts of macroalgae, preferably with a weight ranging between 5 g and 100 g per cutting, for example between 10 g and 100 g per cutt.

[0057] The drawings are only schematic and non-restrictive. The dimensions and relative dimensions of the different elements of the drawings do not correspond to the actual dimensions and relative dimensions. The size of certain elements in the drawings can be exaggerated and not drawn to scale. [0058] Figure 1 is a schematic illustration of a structure 1 for cultivating macroalgae according to the invention. The structure 1 comprises a multidimensional substrate 2 and a wire system 7.

The multidimensional substrate 2 has a first side 3 and a second side (not shown).

The multidimensional substrate 2 comprises, for example, a woven textile structure such as, for example, a polyethylene, polypropylene or polyester structure, optionally provided with a coating such as a polymer coating.

In preferred embodiments, the multidimensional substrate 2 comprises a substrate that is commercialized under the name Algae Tex from AT SEA Technologies.

The wire system 7 comprises, for example, a mesh net consisting of polyethylene, polypropylene or polyester cords or wires 6. For example, the mesh net has square meshes with a mesh size of 2 to 20 cm, for example a mesh size of 8 cm.

The wire system 7 and more particularly the wires 6 of the wire system 7 are connected to one side of the multidimensional substrate 2, for instance to the first side 3 of the multidimensional substrate 2. The wires 6 of the wire system 7 can for example be connected by the forming stitches 8 at predetermined locations.

The distance between consecutive stitches 8 varies, for example, between 0.1 and 1000 cm. In certain embodiments, the distance between two consecutive stitches is 1 to 200 cm, for example 1 cm to 100 cm or 10 cm to 100 cm, such as for example 20 cm, 30 cm, 40 cm, 50 cm, 60 cm or 70 cm.

Once the wire system 7 is attached to the multidimensional substrate 2, the wire system 7 extends over a surface A. The surface A is preferably at least 60% of the area of the first side 3 of the multidimensional substrate 2.

The wire system 7 is a very open structure. Preferably at least 80% or at least 90% of the surface A is not covered by the wires 6 of the wire system 7.

Because the wire system 7 is a very open structure, a large amount of incident light reaches the macroalgae. This has a positive effect on the growth of the macroalgae.

[0059] In preferred embodiments, the multidimensional substrate 2 reflects a high percentage of the incident light, in particular a high percentage of the incident light having a wavelength between 400 nm and 700 nm. The multidimensional substrate reflects for example 50 %, 60% or 80% of the incident light. The multidimensional substrate 2 comprises, for example, a white coloured substrate or a substrate provided with a highly reflective coating. [0060] It can be preferred that the multidimensional substrate 2 has a large specific surface area, for example a specific surface area that is larger than 1 m² per m² of the multidimensional substrate 2. More preferably, the specific surface area varies between 5 m² per m² of substrate 2 such as a specific surface area between 5 m² per m² and 1000 m² per m² substrate 2. A multidimensional substrate 2 with a high specific surface area increases the light reflection. As mentioned above, a high light reflection has a positive effect on the growth and productivity of the macroalgae.

[0061] The pore size of the multidimensional substrate 2 ranges preferably between 10 μιη and 1500 μιη, more preferably between 25 μιη and 500 μιη, such as for example 50 μιη, 75 μιη, 100 μιη, 200 μιη, 300 μιη or 400 μιη.

[0062] Figure 2 shows a second embodiment of a structure 1 for cultivating macroalgae according to the invention. The structure 1 corresponds with the structure shown in Figure 1. Contrary to the first embodiment 1 , the wire system 7 is connected to the multidimensional substrate 2 by connection lines 8', for instance by stitching or embroidering along the connection lines 8'. These connection lines 8' are for example oriented according to the longitudinal direction or according to the width direction of the multidimensional substrate 2.

The distance between two consecutive connection lines 8' varies, for example, between 0.1 and 1000 cm. In certain embodiments, the distance between two consecutive connection lines ranges between 1 and 200 cm, for example between 1 cm and 100 cm or between 10 cm and 100 cm, such as for example 20 cm, 30 cm, 40 cm, 50 cm, 60 cm or 70 cm. [0063] The structure according to the invention is tested for cultivating macroalgae along the southern coast of Kenya, more particularly in intertidal areas. Seaweed cuttings from E. denticulatum and K. alvarezii were first washed. Subsequently, 25 seaweed cutings of 10 g each were applied to a structure according to the invention. The structure used is a structure corresponding to a structure as shown in Figure 2.

The multidimensional substrate comprises, for example, a substrate that is commercialized under the name Algae Tex from AT SEA Technologies.

The wire system comprises, for example, a mesh net with square meshes having a mesh size of 8 cm. This means that the distance between two successive wires of the wire structure is 8 cm. For example, the wire system is connected to the multidimensional substrate by stitching along connection lines 8'. Consecutive connection lines 8' are for example at a mutual distance of 50 cm.

[0064] The structure used for the tests has a total area of 1 m by 1 m. The cuttings of the macroalgae were placed between the filament and the multidimensional substrate with a distance of about 8 to 10 cm between adjacent cuttings.

[0065] After the application of the macroalgae to the structure, the structure was fastened to wooden posts at a depth of about 20 cm from the seabed using ropes such as polyethylene ropes. [0066] Every two weeks, 10 random cuttings were weighed to determine the biomass and the growth of the cuttings. It is clear that the removal of the cuttings from the structure and the subsequent replacement of the cuttings was done with the utmost care to avoid negative effects on the seaweed cuttings. [0067] The percentage daily growth rate (DGR%) of the seaweed cuttings is determined by applying the following formula:

DGR% = In (Wf / W0) / 1 x 100

With Wf the weight of the seaweed pitch on day t

Wo the weight of the initial seaweed pitch (on day 0)

t time (expressed in days). [0068] The results of the seaweed biomass are shown in Table 1 , the percentage daily growth rate is shown in Table 2.

Table 1 : average weight (g ± SD (standard deviation)) of E. denticulatum and K. alvarezii after 0, 14, 18 and 42 days of cultivation

[0069] From Table 1 and Table 2 can be concluded that particularly high percentage daily growth rates (DGR%) are obtained.

Furthermore, it can be concluded that the biomass yield obtained by using a structure for cultivating macroalgae according to the invention is three to eight times higher than the biomass yield obtained by using traditional rope-based systems.

Claims

1. A structure (1) for cultivating macroalgae, comprising

a multidimensional substrate (2) comprising a first side and a second side, a wire system (7) comprising a plurality of wires (6), the wire system (7) being connected to the first side or to the second side of the multidimensional substrate (2) and is forming a multidimensional wire system (7) extending over a surface A of the multidimensional substrate (2,) whereby the multidimensional wire system (7) and/or the wires (6) of the multidimensional wire system (7) is/are connected at predetermined connection spots to the multidimensional substrate and whereby at least 70% of the surface A of the multidimensional substrate (2) is not covered by the wires (6) of the multidimensional wire system (7).

2. The structure (1) according to claim 1, wherein at least 80 % of the surface A of the multidimensional substrate is not covered by the wires (6) of the multidimensional wire system (7).

3. The structure (1) according to claim 1 or claim 2, wherein the mutual distance between two consecutive connection spots (8, 8 ') varies between 0.1 cm and 1000 cm.

4. The structure (1) according to any one of the preceding claims, wherein the multidimensional wire system (7) and/orthe wires (6) of the multidimensional wire system (7) is/are connected to the multidimensional substrate (2) at predetermined connection points (8) or according to predetermined connection lines (8').

5. The structure (1) for cultivating macroalgae according to any one of the preceding claims, wherein the multidimensional substrate (2) comprises a substantially flat substrate.

6. The structure (1) according to any one of the preceding claims, wherein the multidimensional substrate (2) comprises a film, a foil, a mesh, a woven structure, a non-woven structure, a knitted structure, a braided structure or a combination thereof.

7. The structure (1) according to any one of the preceding claims wherein the wires (6) comprise filaments, cords, cables, ribbons or combinations thereof.

8. The structure (1) according to any one of the preceding claims, wherein the multidimensional wire system (7) comprises a group of parallel or predominantly parallel wires, a net, a mesh or a combination thereof.

9. The structure (1) according to any one of the preceding claims, wherein the multidimensional wire system (7) and/or the wires (6) of the multidimensional wire system (7) is/are partially connected to the multidimensional substrate (2) by a mechanical, chemical and/or thermal method.

10. The structure (1) according to any one of the preceding claims, wherein the multidimensional wire system (7) and/or the wires (6) of the multidimensional wire system (7) is/are partially connected to the multidimensional substrate (2) by stitching , embroidery, knitting, knotting or a combination of these.

11. The structure (1) according to any one of the preceding claims, wherein at least 95% of the surface A of the multidimensional substrate (2) is not covered by the wires (6) of the multidimensional wire system (7).

12. A method for cultivating macroalgae, the method comprising the following steps providing a structure (1) as defined in claims 1 to 11,

applying cuttings of macroalgae to the wires (6) of the wire system (7) or between the wires (6) of the wire system (7) and the multidimensional substrate (2), harvesting the macroalgae.

13. Use of a structure (1) as defined in any one of claims 1 to 11 for cultivating macroalgae.

14. A method to manufacturing a structure (1) as defined in any one of claims 1 to 1 1 comprising the following steps

providing a multidimensional substrate (2) comprising a first side and a second side; providing wires (6) or providing a wire system (7);

connecting the wires (6) or the wire system (7) to the multidimensional substrate (2) at predetermined locations.