System and method for cultivation of seaweed

Abstract

There is disclosed a system (10) for cultivation of seaweed, the system comprising: - a support structure (4), and - an elongated growth substrate (1, 5), that when spooled around the support structure (4) has a substantially flat cross-section, wherein the elongated growth substrate (1, 5) is spooled around the support structure (4) so that the long sides are stacked on top of each other with one short side facing the support structure (4), the other short side facing radially outwardly There is also disclosed a method for cultivating seaweed by using the system.

Description

[0001] SYSTEM AND METHOD FOR CULTIVATION OF SEAWEED

[0002] The present invention relates to a system and a method for cultivation of seaweed.

[0003] The cultivation of seaweed is an intricate process that typically involves two main stages: nurturing of seedlings on land and the subsequent grow-out stage at sea. This division stems from the natural life cycle of seaweeds, usually comprising multiple distinct phases: a mature sporophyte stage and a motile spore stage, which occurs during the reproductive period. To cultivate seaweed species successfully, controlled reproduction is typically induced in land-based hatcheries.

[0004] Once the motile spores are produced, they adhere to a cultivation substrate for initial growth. The most common type of substrate involves thin ropes that are wound around a rigid structure, often a tube, pipe, or similar. Due to the delicate nature of the spores, it's necessary to grow them into more robust seedlings in a controlled environment before transferring them to the sea for the grow-out stage.

[0005] Even when the seedlings reach the predetermined age / size for transfer to the sea, they are still vulnerable. This transition therefore represents a critical moment in seaweed cultivation, because of the large risk that external stress prohibits their further growth. This can be from e.g. mechanical interactions of human handling, prolonged time out of water, or other abrupt environmental changes, like sudden changes to temperature or PH.

[0006] These stressors can affect the metabolic processes of the seedlings, inhibiting their ability to assimilate nutrients and grow, and because the seedlings have not yet developed the robustness of mature seaweed to withstand these changes, this can significantly slow or completely halt their continued growth. One of the major challenges in seaweed cultivation is therefore to minimize the stress and handling the young seedlings are exposed to during their formative months, while still performing cost-effective and large-scale cultivation. Multiple production methods exist to this effect, but they currently do so by introducing compromises that negatively affect either the biological aspects discussed above or the economic scalability of the production system.

[0007] Both the production of seedlings in land-based laboratories and the subsequent grow-out stage in the sea present distinct challenges and requirements concerning growth substrate, often ropes, and various strategies exist to optimize efficiency and yield.

[0008] A known method involves using the same conventional rope in both the pre-cultivation and cultivation stages. In this approach, cultivators typically select the smallest diameter of rope (~6mm or larger) that is both strong enough to withstand sea conditions and has enough girth to support proper seaweed attachment and growth. This minimizes the handling of seedlings during the transition from lab to sea, thereby reducing the risk of mechanical stress on the seedlings, but a significant drawback is the space inefficiency in the hatchery, as large land-based hatchery areas are needed to accommodate relatively low lengths of seaweed-laden rope.

[0009] Another known method optimizes for each stage individually by using different types of rope in the pre-cultivation and cultivation stages. During the pre-cultivation in the hatchery, thin ropes, often called twine, are used to maximize the amount of growth substrate within the limited available space. These thin ropes, however, are not suitable for sea conditions and cannot support the load of large seaweed growth. After pre-cultivation, the seedling-laden twine is transferred to thicker, sea-worthy carrying ropes using a mechanical combination method. This solution optimizes for both lab space and sea-based cultivation, offering a balance between the two. However, there is an increased risk of mechanical stress on the seedlings during the transition, and the connection of one rope to another also adds complexity and cost, stemming from the logistics involved in combining the twine rope with the carrying rope, and increased complexity during harvesting. Yet another alternative method has been to eliminate the pre-cultivation stage altogether by directly affixing spores / gametophytes / seedlings onto carrying ropes in the sea. Many different organizations have described machines to perform direct seeding and various substrate materials have been tested to enhance growth; for example, AlgaeRibbon by AtSeaNova uses a stiff ribbon substrate to increase the surface area available for seaweed growth. This eliminates the costly pre-cultivation stage. However, by omitting the precultivation, yield can be lower and less consistent than when using pre-cultivation. When optimizing for efficient use of lab space by using twine, that introduces complex handling of the seedlings during combination with the secondary load-bearing rope. This in turn introduces larger losses, lower yield, and increased logistical operations. If optimizing for reduced stress during the transition by pre-cultivating on a rope capable of load bearing, the effective lab space is reduced by approximately three times (e.g. < 2mm vs. > 6mm), significantly impacting the scalability production.

[0010] With the current methods, there are persistent and inherent compromises between the biological considerations and the scalability of the production systems:

[0011] CN 202210945608 A discloses a seedling device for cultivation of seaweed, the seedling device comprising a hollow support tube and a seedling rope spooled around the support tube.

[0012] KR 20030087022 A discloses a cultivation method for seaweed and a device for raising seedlings, the device comprising a support hollow cylindrical structure and an elongated growth substrate wrapped around the support.

[0013] The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

[0014] The object is achieved through features, which are specified in the description below and in the claims that follow.

[0015] The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention. In a first aspect, the invention relates to a system for cultivation of seaweed according to claim 1.

[0016] By "substantially flat" is meant a growth substrate having a cross-section with a length-to- width ratio of 2:1 or larger, preferably in the range 4:1 or larger.

[0017] In one embodiment, the elongated growth substrate may be substantially flat (i.e. have a substantially flat cross-section) also when unloaded. This may be beneficial for reducing the amount of compression (loading) needed between the loops when the rope is spooled onto the support structure. In an alternative embodiment, the elongated growth substrate may be less flat or non-flat when unloaded. The elongated growth substrate may be provided in an elastic material so that its cross-section becomes substantially flat in compression.

[0018] In one embodiment, the elongated growth substrate may comprise a load-bearing hollow braid rope. The sheath of the rope may provide the primary tensile strength and durability required for seaweed cultivation. The hollow braid rope may in one embodiment include high-durability polyester (PES) that offers resistance to ultraviolet (UV) exposure, saltwater corrosion, and abrasion. IN one specific non-limiting embodiment, the sheath may be braided from 48 filaments arranged in 24 plaits, each containing two parallel filaments. This configuration allows for uniform load distribution and structural integrity, and given the system's load requirements, an internal core— as found in kernmantle ropes— is unnecessary. This rope, having a diameter of 14 mm and a breaking load of over 800 decaNewtons (daN), is capable of withstanding the mechanical forces encountered in a marine environment while supporting the load of growing seaweed biomass. Furthermore, the sheath serves as a substrate for seaweed spore attachment and holdfast development. The rope is devoid of chemicals that may leach into the water and is washed prior to deployment to ensure compliance with environmental safety standards.

[0019] In one embodiment the surface of the sheath may be roughened to increase the available texture for spore settlement and promote holdfast development. The buoyancy of the PES rope may be slightly negative, enabling stable positioning within the water column, thereby optimizing conditions for seaweed growth and minimizing displacement caused by water currents.

[0020] The parameters of the rope can be tailored to meet the specific requirements of various seaweed species and environmental conditions. Parameters include the rope's diameter, number of plaits, filament size, radial depth of the plaits, surface roughness, buoyancy, and material composition. For example, increasing the diameter may provide additional surface area and stability for species requiring greater attachment space or for deployment in high-energy environments. Conversely, reducing the diameter may optimize space usage and material efficiency for smaller species or in sheltered environments. Adjusting the surface roughness enhances spore settlement and holdfast development, while modifications to buoyancy ensure optimal positioning within the water column. The material composition and filament size can be altered to adjust the rope's tensile strength and flexibility, catering to specific cultivation needs.

[0021] The length of the elongated growth structure, such as the hollow braid rope, that can be wound around the support structure is determined by the thickness of the rope when laid flat under compression and the size of the support structure. As the thickness of the flattened rope decreases, more rope can be spooled, thereby increasing space efficiency during the pre-cultivation phase. Upon deployment, the rope is unspooled and may regain its round shape or at least reduce its flatness, significantly expanding the surface area available for seaweed growth. By optimizing the rope's flattened thickness, the system maximizes both the rope length that can be stored in the hatchery and the surface area for cultivation once deployed at sea.

[0022] In one embodiment, the support structure may be formed with grooves or other guiding means for guiding the elongated growth substrate onto the support structure, which may ease the spooling and un-spooling and give a predictable positioning of the elongated growth substrate on the support structure. The guiding means, such as grooves, may make it difficult to provide compression between the loops of the elongated growth sub- strate and it may as such be particularly advantageous with a substantially flat crosssection also when unloaded.

[0023] In one embodiment the support structure may be formed with ledges / flanges extending radially outwardly from top and bottom portions of the support structure. The ledges may be useful to keep the elongated growth substrate in place on the support structure and optionally to provide compression / loading on the elongated growth substrate if desired.

[0024] In a second aspect, the invention relates to a method of cultivation of seaweed according to claim 6.

[0025] At the time of deployment at sea, each turn of the spool will be separated from the next, and the seedlings will have space to grow further, thereby gradually settling on the rest of the rope. The flat shape of the rope can be achieved by using a rope that deforms under compression, or by a rope that has an oblong equilibrium / unloaded state, e.g. a hollow core rope. The rope may be spooled onto the rigid structure, e.g. a tube, such as by using a spooling machine that may keep the rope in constant tension while distributing it in uniform, axial compression relative to the rigid structure. The rigid structure may act like a guide for the rope. As an alternative or in addition, the spooling machine may actively guide the rope onto the structure.

[0026] The system and method according to the invention combine the advantages of both the "twine" and "pre-cultivated direct" methods, without adopting any of their aforementioned disadvantages.

[0027] In particular, the system and method according to the invention i.a. have the following advantages:

[0028] 1) Using a flat rope as substrate achieves mode duality cultivation of seaweed, by allowing for efficient use of hatchery space, similar to the use of twine, while 2) it avoids the need for the mechanical combination of two ropes during the transfer of seedlings from pre-cultivation to the cultivation stage. Thereby a) reducing the biological stress on the seedlings during transition, increasing yield and b) minimizing the logistical operations needed to deploy the seedlings at sea, c) decreasing the overall length of rope needed for cultivation by more than 50%, d) streamlining harvest operations by removing the complexity of hauling in the combination of twine and carrying rope at the same time, and e) eliminating the possibility of negative environmental impacts from detached twine rope during deployment and harvest.

[0029] 3) It allows for a more efficient deployment by the simultaneous release of multiple ropes spun around from the same rigid structure.

[0030] A load-bearing rope with a flat / elongated geometry is spooled around the rigid structure, e.g. a tube, at the pre-cultivation stage. The outer (or both) short side(s) of the flat rope acts as a growth substrate, and is exposed to the spores, and later light, water, and nutrients. The long sides of the flat rope are tightly spooled up against each other, orthogonally to the rigid structure, such that there is no free space for the spores to grow there.

[0031] The short side of the rope performs the same function as the twine does, by having spores settle and develop into seedlings, while the long sides of the rope provide the majority of load-bearing structure and capacity. The width of the long side can be increased or decreased according to the specific load-bearing requirements of the system.

[0032] At the time of deployment at sea, each turn of the spool is separated from the next, and the seedlings will have space to grow further, thereby gradually settling on the rest of the rope. The flat shape of the rope can be achieved by using a rope that deforms under compression, or by a rope that has an oblong equilibrium / unloaded state, e.g. a hollow core rope. The rope is spooled onto the rigid structure, e.g. a tube, such as by using a spooling machine that keeps the rope in constant tension while distributing it in uniform, axial compression relative to the rigid structure. The rigid structure may act like a guide for the rope. As an alternative or in addition, the spooling machine may actively guide the rope onto the structure.

[0033] In one embodiment, a plurality of individual ropes may be spooled along the same rigid structure adjacent to each other, such as in a double or triple helix mode. A plurality of ropes may be deployed at sea simultaneously from the same rigid structure, allowing for a more efficient deployment.

[0034] In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

[0035] Fig. 1 shows, in a side view, a system according to the invention;

[0036] Fig. 2 shows, in a cross-sectional view along the line A-A, the system from Fig. 1;

[0037] Fig. 3 shows, in a perspective view, the system from Fig.l;

[0038] Fig. 4 shows detail B from Fig. 2;

[0039] Fig. 5 shows, in a side view, a system for growing seaweed at sea; and

[0040] Fig. 6 shows the system from Fig. 5 in a perspective view.

[0041] In the following, reference numeral 10 will be used to denote a system according to the present invention. Identical reference numerals refer to identical or similar features in the drawings. The drawings are shown simplified and schematic, and various features therein are not necessarily drawn to scale.

[0042] Fig. 1 shows a system 10 according to the present invention, where a flat rope 1 is spooled around a rigid structure 4, here in the form of a hollow, cylindrical tube.

[0043] Fig. 2 shows a longitudinal cross-section as seen through the line A-A from Fig. 1. The upper and lower end of the rigid structure 4 is provided with a ledge / flange 2 ensuring an axial force on the flat rope 1 and preventing is from unspooling.

[0044] Fig. 3 shows the system according to the invention in a perspective view, while Fig. 4 shows detail B from Fig. 2, where the flat cross-sectional shape of the rope 1 can be bet- ter seen. In shown embodiment, the width / height ratio of the rope 1 is approximately 4:1.

[0045] Figs. 5 and 6 show the rope 1 when deployed at sea and functioning as a growth substrate 5 in a seaweed farming system 100. The seaweed farming system 100 comprises a cultiva- tion frame 6 spanning the rope 1 / growth substrate at sea. The cultivation frame 6 in the shown embodiment having a substantially quadratic shape and being provided with buoys 8 in each corner for creating buoyancy. The cultivation frame 6 is further moored to the seabed by means of anchors 12 connected to the cultivation frame 6 via mooring lines 14. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0046] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

C l a i m s1. System (10) for cultivation of seaweed, the system comprising:- a support structure (4), and- an elongated growth substrate (1, 5), that when spooled around the support structure (4) has a substantially flat cross-section, c h a r a c t e r i s e d i n that the elongated growth substrate (1, 5) is spooled around the support structure (4) so that the long sides are stacked on top of each other with one short side facing the support structure (4), the other short side facing radially outwardly.

2. System (10) according to claim 1, wherein the elongated growth substrate (1, 5) has a substantially flat cross-section when unloaded.

3. System (10) according to claim 1 or 2, wherein the support structure (4) is a hollow cylindrical structure.

4. System (10) according to any one of the preceding claims, wherein the support structure (4) is formed with guiding means, such as grooves, for guiding the elongated growth substrate onto the support structure.

5. System (10) according to any one of the preceding claims, wherein the support structure (4) is provided with ledges (2) extending radially outwardly from a top portion and a bottom portion of the support structure, the ledges providing an axial force onto the elongated growth substrate and preventing it from unspooling.

6. Method for cultivation of seaweed, using a system (10) according to any one of the preceding claims, the method comprising the step of:- spooling the elongated growth substrate (1, 5) onto the support structure (4);- exposing the elongated growth substrate (1, 5) to spores.

7. Method according to claim 6, wherein a plurality of individual elongated growth substrates (1, 5) is spooled adjacently along the support structure (4).

8. Method according to claim 6 or 7, wherein the step of exposing the elongated growth substrate (1, 5) to spores includes exposing one or both of the short sides in the substantially flat cross-section to the spores.

9. Method according to claim 8, wherein the method further includes the step of ex- posing the spores on the elongated growth substrate (1, 5) to water, light and nutrients.

10. Method according to claim 9, further including the step of deploying the elongated growth substrate (1, 5) to sea.

11. Method according to claim 9, further including the step of simultaneously deploy- ing a plurality of elongated growth substrates (1, 5) to sea.

12. Method according to claim 10 or 11, further including the step of spanning the elongated growth substrate (1, 5) in cultivation frame (6).

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