Seaweed cultivation and monitoring system and sediment collection device

Abstract

This invention provides a seaweed cultivation and monitoring system aimed at improving carbon capture and storage in the ocean. [Solution] System 1 comprises a support structure 110 configured to be installed in a body of water, and a net structure 120 with a sediment collection device 130 positioned below it. The support structure includes a frame and a plurality of vertical support members. The vertical support members are positioned at the corners of the frame, and each vertical support member comprises a floating member and an anchor member. The floating members maintain a connection with the frame, and the anchor members are configured to be fixed to the seabed. The system design offers high adaptability and robustness, enabling large-scale offshore seaweed cultivation and verifiable carbon sequestration in harsh marine environments.

Description

Technical Field

[0001] The present disclosure relates to seaweed cultivation and monitoring systems. Specifically, the present disclosure relates to seaweed cultivation and monitoring systems and seaweed cultivation and monitoring methods that can enhance carbon capture and storage in the marine environment.

Background Art

[0002] The increase in the concentration of carbon dioxide (CO2) in the atmosphere is a major factor in global climate change, leading to rising global temperatures, ocean acidification, and sea-level rise. Urgent and innovative solutions are needed to effectively reduce and sequester CO2 from the atmosphere and the ocean. Carbon capture and storage (CCS) technologies have emerged as an important approach, encompassing various methods for capturing CO2 directly from industrial sources or from the atmosphere and storing it permanently. Among these, solutions that utilize nature, particularly those that harness the vast potential of marine ecosystems, are attracting increasing attention due to their remarkable scale and potential for sustainability.

[0003] One promising approach for large-scale carbon sequestration in the marine environment is the cultivation of seaweed, also known as macroalgae. Seaweed absorbs large amounts of CO2 from seawater through photosynthesis and converts it into biomass. The subsequent sinking of this biomass to the deep sea represents a natural and effective mechanism for long-term carbon sequestration, as carbon is removed from the active biogeochemical cycle over a long period. This process is often referred to as "ocean carbon farming" or "blue carbon" initiatives, offering a promising strategy for mitigating climate change by harnessing the biological pump of the ocean.

[0004] However, existing technologies and methodologies for offshore seaweed cultivation and carbon sequestration in the deep sea face several significant limitations that hinder their widespread implementation and overall effectiveness. Current seaweed cultivation is primarily limited to shallow coastal areas. These near-coastal environments are often constrained in terms of available space, susceptible to coastal development pressures, and potentially subject to nutrient deficiencies or environmental changes that affect seaweed growth and yield. Furthermore, reliance on shallow waters limits the scale at which carbon sequestration can be achieved, making it difficult to have a significant impact on global CO2 concentrations.

[0005] Furthermore, a significant drawback of current carbon sequestration methods involving biomass sedimentation is the lack of robust and reliable methods for monitoring carbon deposition and quantifying the actual amount of carbon sedimented. Without accurate, real-time monitoring capabilities, it is difficult to validate the effectiveness of these strategies, assess their carbon removal efficiency, and generate verifiable carbon credits. This lack of verifiable monitoring data presents significant challenges to investment, regulatory oversight, and the widespread adoption of ocean-based carbon sequestration solutions. The inability to accurately track carbon sedimentation fluxes creates uncertainty regarding the sustainability and overall impact of such initiatives. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, there is an urgent and unresolved need for advanced offshore aquaculture technologies that can overcome these existing constraints. More specifically, there is a need for systems and methods that can enable seaweed cultivation in the open ocean beyond the constraints of coastal areas, thereby enabling significantly large-scale operations. Such technologies must be designed to withstand the often harsh and volatile conditions of the open ocean, including diverse climatic conditions, strong currents, and extreme weather events. Crucially, there is a persistent demand for integrated solutions that incorporate effective and simultaneous monitoring of carbon sedimentation flux and provide real-time data on the amount of carbon being sequestrated. The development of such comprehensive and durable technologies is essential to maximizing the potential of offshore seaweed cultivation as a viable and effective carbon sequestration strategy. This disclosure addresses these critical shortcomings by introducing an innovative system for offshore seaweed cultivation and carbon sequestration that extends beyond current capabilities and provides high robustness and integrated monitoring capabilities for effective climate change mitigation. [Means for solving the problem]

[0007] To achieve the purposes of this disclosure, this disclosure provides a seaweed cultivation and monitoring system comprising: a support structure comprising a frame and configured to be installed in a body of water; a net structure configured within the frame and configured for cultivating seaweed; and at least one sediment collection device coupled to the net structure and positioned below the net structure, wherein the at least one sediment collection device is configured to collect sediment.

[0008] Preferably, the precipitate includes settled seaweed.

[0009] Preferably, the support structure comprises a plurality of vertical support members for supporting the frame.

[0010] Preferably, the vertical support members are positioned at the corners of the frame, and each vertical support member comprises a floating member and an anchor member, the floating member being configured to maintain a connection with the frame and the anchor member being fixed to the seabed.

[0011] Preferably, at least one sediment collection device is positioned at a vertical distance of at least 2 meters below the net structure.

[0012] Preferably, the net structure comprises a plurality of tube nets, each tube net having two rings at both ends, and the rings are configured to be connected to a frame.

[0013] Preferably, the multiple tube nets include a substrate configured for cultivating seaweed.

[0014] Preferably, the base material is selected from the group consisting of natural materials, artificial materials, and combinations thereof.

[0015] Preferably, the distance between each of the multiple tube nets is between 0.3m and 2m.

[0016] Preferably, the sediment collection device comprises an upper ring, a net trap, a collection cup, and a sinker.

[0017] Preferably, the net trap is substantially conical in shape.

[0018] Preferably, the net trap is made from a mesh material having a mesh size of 150 to 300 μm.

[0019] Preferably, the length of the net trap can be 2 to 5 times the diameter of the upper ring.

[0020] Preferably, the length of the net trap is between 2m and 5m.

[0021] To achieve still other objects of the present disclosure, the present disclosure provides a sediment collection device including an upper ring, a net trap, a collection cup, and a sinker.

[0022] Preferably, the net trap is substantially conical.

[0023] Preferably, the net trap is made of a mesh material having a mesh size of 150 to 300 μm.

[0024] Preferably, the length of the net trap can be 2 to 5 times the diameter of the upper ring.

[0025] Preferably, the length of the net trap is between 2 m and 5 m.

[0026] With the above technical features, the present disclosure provides a large-scale seaweed cultivation system that can withstand changing marine environments and stably harvest seaweed. Specifically, by providing a tube net, the harvesting of seaweed becomes easier. Furthermore, the sedimented seaweed can be collected through the sediment collection device. By monitoring the amount of harvested seaweed and the sedimentation amount, the amount of accumulated carbon dioxide can be monitored and estimated.

[0027] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, it will be apparent to one of ordinary skill in the art that one or more embodiments may be practiced without these specific details. In some instances, conventional structures and processes are shown schematically in order to simplify the drawings.

Brief Description of the Drawings

[0028] [Figure 1] A perspective view of a seaweed cultivation and monitoring system according to an embodiment of the present disclosure. [Figure 2] A perspective view of a support structure according to an embodiment of the present disclosure. [Figure 3]A partially enlarged view of a frame according to one embodiment of the present disclosure. [Figure 4] A partially enlarged view of a tube net within a seaweed cultivation and monitoring system according to one embodiment of the present disclosure. [Figure 5] This is a perspective view of a sediment collection device for a seaweed cultivation and monitoring system according to one embodiment of the present disclosure. [Figure 6] This is a flowchart of a seaweed cultivation and monitoring method according to one embodiment of the present disclosure. [Figure 7] This is a flowchart of a method for monitoring seaweed accumulation during seaweed cultivation according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0029] Embodiments will be described in detail below with reference to the accompanying drawings. However, these embodiments can be implemented in various forms and should not be construed as limiting the implementation or application of any particular embodiment claimed. These embodiments encompass the features of several particular embodiments, as well as method steps and their sequence for constructing and operating these particular embodiments. However, the same or equivalent functions and sets of steps can also be implemented in other particular embodiments. In contrast, these embodiments are intended to fully and completely disclose the present disclosure and to fully convey the technical idea to those skilled in the art. In contrast, these embodiments are intended to fully and completely disclose the present disclosure and to fully convey the technical idea to those skilled in the art. The same reference numerals used in the accompanying drawings indicate the same components. In the following description, detailed descriptions of prior functions or structures are omitted to avoid repeating unnecessary details of the embodiments.

[0030] Unless otherwise defined, all technical and specialized terms used herein have the same meaning as those generally understood by those skilled in the art. In the event of any conflict, the definitions and other provisions of this specification shall prevail.

[0031] In this specification, singular nouns may include their plural forms, and vice versa, as long as it does not create a contextual inconsistency. In this specification and in the claims for utility model registration, "at least one" and "one or more" have the same meaning, both referring to one, two, three, or more.

[0032] All parameters and numerical ranges used to define the broad scope of this disclosure are approximations, although relevant numerical values ​​are described as accurately as possible in specific embodiments. However, essentially, all numerical values ​​inevitably carry a certain degree of error due to the standard deviation associated with each individual test method. The adverb “about” as used herein generally means that the difference between an actual numerical value and a particular numerical value or range is less than 10%, 5%, 1%, or 0.5%. Alternatively, the adverb “about” as used herein means that the actual numerical value differs by a range less than or equal to an allowable standard deviation from the mean, which is defined by those skilled in the art. Except in embodiments or unless otherwise specifically designated, all numerical ranges, quantities, numerical values, and percentages used herein (e.g., representing the amount of material used, time period, temperature, operating conditions, quantitative proportions, etc.) shall be interpreted as having the adverb “about” attached to them. Accordingly, unless otherwise specifically designated, all numerical parameters disclosed herein and in the claims for utility model registration are approximations and may be modified as necessary. At a minimum, numerical parameters must be characterized by significant figures and interpreted as values ​​obtained using a common carry-over method. In this regard, numerical ranges are expressed as extending from one endpoint to the other, or between two endpoints. Unless otherwise specified, all numerical ranges include the endpoints.

[0033] Referring to Figure 1, a seaweed cultivation and monitoring system 1 according to one embodiment of the present disclosure is shown. System 1 comprises a support structure 110, a net structure 120, and at least one sediment collection device 130.

[0034] Referring to Figure 2, the support structure 110 is configured to be installed in a body of water and includes a frame 111. In some embodiments, the support structure 110 may further include a plurality of vertical support members 112 for supporting the frame 111. To fix the support structure 110 to the body of water, the vertical support members 112 are positioned at each corner of the frame 111, and each vertical support member 112 includes an anchor member 113 and a floating member 114. The anchor member 113 and the floating member 114 can be connected by a rope 117. The material of the rope 117 connecting the anchor member 113 and the floating member 114 can be selected from corrosion-resistant and high-strength materials suitable for an underwater environment, such as stainless steel, aluminum alloy or reinforced plastic, nylon, etc., and is preferably a nylon rope. The anchor member 113 may be a weight such as a ballast stone, or some device for fixing the vertical support members 112 to the seabed. The floating members 114 can be made from EVA (ethylene vinyl acetate) floats or other floats with equivalent buoyancy as needed. The floating members 114 can be connected to the four corners of the frame 111 by nylon ropes or other suitable materials to form a floating platform. The design shall take into account factors such as water flow resistance, wave impact, and biofouling to ensure the stability of the system under various aquatic conditions.

[0035] Frame 111 provides the main skeletal frame structure for the entire system. Frame 111 can be constructed from a variety of durable and corrosion-resistant materials, such as marine-grade stainless steel, galvanized steel, or high-density polyethylene (HDPE) pipes, PE or nylon rope, preferably nylon rope. The shape and dimensions of frame 111 can vary depending on the scale of cultivation, water characteristics, and target seaweed species. For example, it can be rectangular, square, or circular. Referring to Figure 3, frame 111 may further comprise a floating unit 115 to ensure the buoyancy of the frame. Frame 111 is designed to withstand dynamic forces from ocean currents and waves while maintaining structural integrity. Frame 111 may further comprise connecting members 116, such as hooks, clamps, or integrating loops, which are arranged along frame 111 to facilitate easy connection and disconnection of the net structure 120. This modular design enables efficient installation, maintenance, and harvesting operations.

[0036] The net structure 120 is provided within the frame 111 and is configured for cultivating seaweed. In some embodiments, the net structure 120 may comprise a plurality of tube nets 122.

[0037] Referring to Figure 4, each tube net 122 is provided with two rings 123 at both ends (only one end is shown in Figure 4), which are configured to be connected to the frame 111 via connecting members 116. Each tube net 122 can contain a substrate (not shown) to which seaweed is attached for cultivation. The choice of substrate is diverse and may include natural materials (e.g., natural fibers, ropes, stones) or artificial materials (e.g., plastic nets, PE tubes, PVC pipes), or combinations thereof. The distance between each of the multiple tube nets 122 can be predetermined, but is not limited to this. Preferably, the minimum distance between each tube net 122 can be 0.3 m, but there is no limit to the maximum distance. The minimum distance is necessary to prevent the tube nets from becoming entangled. In one embodiment, the distance between each tube net is 0.3 m to 2 m, preferably 0.5 m to 1.5 m, to ensure sufficient space for seaweed growth and water exchange. The material of the net structure 122 shall have good water permeability and be harmless to seaweed.

[0038] The tube net 122 itself is typically made from a mesh material that is durable, flexible, and UV resistant, preferably nylon mesh material, which allows for efficient water circulation and nutrient exchange while firmly holding the seaweed. The mesh size can be 10mm to 50mm, preferably 20mm to 40mm, which may vary depending on the growth stage and species of seaweed, ensuring proper fixation and preventing premature detachment.

[0039] As shown in Figure 4, the two rings 123 at both ends of each tube net 122 play a crucial role in their integration with the frame 111. These rings 123 are often made of sturdy plastic or metal and provide a strong connection between the tube net 122 and the frame 111, allowing the tube net 122 to be easily suspended horizontally or vertically within the frame 111. This design allows for the convenient installation and removal of individual tube nets 122 for sowing, monitoring, or harvesting without disrupting the entire seaweed cultivation and monitoring system 1. The modularity of these tube nets within the frame facilitates expandable and contractible cultivation operations, allowing for the expansion or contraction of the cultivation area as needed.

[0040] Referring to Figure 5, at least one sediment collection device 130 is connected to the net structure 120, positioned below it, and configured to collect sediment. The sediment collection device 130 comprises an upper ring 131, a net trap 132, a collection cup 133, and a sinker 134. The upper ring 131 is connected to an upper rope 135 (connected to the frame 111 or the net structure 120) and the net trap 132. The net trap 132 and the collection cup 133 are configured to collect sediment. The sinker 134 is configured to maintain the net trap 132 in an deployed state. This sediment may include sinking seaweed, detached biological debris, plankton residue, or other particulate matter in the water. In some embodiments, the upper ring 131 may be made of steel or a suitable material. In some embodiments, the net trap 132 may be substantially conical or other shapes suitable for collecting sediment. The net trap 132 can be made from a mesh material having a specific mesh size, for example, 60 μm to 500 μm, preferably 150 μm to 300 μm, which allows water to pass through while effectively collecting sediment. The length of the net trap 132 should be 2 to 5 times, more preferably 2 to 3 times, the diameter of the upper ring 131. In one embodiment, if the diameter of the upper ring 131 is 1 m, the length of the net trap 132 can be 2 m to 5 m, preferably 2 m to 3 m. In some embodiments, the collection cup 133 can be made from steel, plastic or a suitable material. In some embodiments, the sinker 134 can be metal, stone or a suitable material that imparts weight. The sediment collection device 130 can be positioned below the net structure 120 at a vertical distance ranging from 2 to 15 m to ensure the collection of sediment originating from the upper seaweed cultivation area. Preferably, the sediment collection device 130 can be suspended from the structural ropes of the seaweed cultivation and monitoring system and is usually installed in the center and on both sides of the net structure 120 (a total of 3 units).

[0041] Referring to Figure 6, this disclosure also provides a method for cultivating seaweed using the seaweed cultivation and monitoring system 1 described above, which includes the following steps. S101: System installation: Install seaweed cultivation and monitoring system 1 in the body of water. S102: Arrangement of substrate: The substrate is placed inside multiple tube nets 122. S103: Seaweed attachment: Seaweed is attached to the substrate inside multiple tube nets 122 for cultivation.

[0042] In some embodiments, the method may further include the step of harvesting seaweed cultivated from a plurality of tube nets 122.

[0043] Furthermore, referring to Figure 7, the present disclosure provides a method for monitoring seaweed sedimentation during seaweed cultivation, which includes the following steps: S201: System Installation: Install seaweed cultivation and monitoring system 1 in the body of water. S202: Arrangement of substrate: The substrate is placed inside multiple tube nets 122. S203: Seaweed attachment: Seaweed is attached to the substrate inside multiple tube nets 122 for cultivation. S204: Collection of sediment: Sediment is collected using at least one sediment collection device 130.

[0044] In some embodiments, the sediment is derived from cultivated seaweed. The method may further include the step of analyzing the sediment collected from at least one sediment collection device 130 to assess the health or productivity of the seaweed. Furthermore, the method may include measuring the sedimentary carbon flux from the collected sediment and estimating the amount of carbon sequestration from the collected sediment, providing useful data for understanding the environmental impact and potential benefits of seaweed cultivation.

[0045] The following describes in detail specific embodiments of the seaweed cultivation and monitoring system described herein.

[0046] A. Experimental design

[0047] 1. Exam site

[0048] The offshore seaweed cultivation and monitoring system described herein is located at coordinates 23°7.741′N 121°24.709′E, off the coast north of Sanxiantai, Chenggong Township, Taitung County, on the eastern coast of Taiwan. This location provides access to open ocean conditions relevant to large-scale seaweed cultivation research.

[0049] 2. Examination Period

[0050] The construction of the offshore seaweed cultivation and monitoring system was completed in September 2023. Ongoing trials of seaweed cultivation began in October 2023 and continued until May 2025, totaling 20 months of operation. This extended trial period allows for comprehensive observation of seaweed growth and system performance across various seasonal conditions.

[0051] 3. Test Environment

[0052] The environmental conditions at the test site are characterized by specific ocean parameters. Surface seawater temperatures in this region typically range from approximately 25°C in winter to 28°C in summer and autumn. Mixed layer depth exhibits seasonal variations, increasing from approximately 20m in summer to 80m in winter. Salinity fluctuates stably between 33.5 and 34.5 psu throughout the year.

[0053] The seaweed cultivation and monitoring system is strategically positioned on the upper slope of the continental margin, in the area where it transitions into the deep-sea Pacific basin. The water depth directly beneath the seaweed cultivation and monitoring system (support structure) is 26m. Beyond this point, the seabed drops steeply to a depth of 500m 4km offshore and then to a depth of 1000m 6.6km offshore, with a slope angle of approximately 8°. The test site is located 600m east of the coastline and is mainly influenced by alternating east-west currents, which exhibit a tidal range of approximately 2m. Furthermore, the northward-flowing Kuroshio Current passes east of the test site, contributing to the region's ocean dynamics.

[0054] Nutrient availability, particularly nitrate concentrations at the surface, is maintained below 0.5 μmol / kg throughout the year. Nitrate concentrations increase with depth, reaching approximately 10 μmol / kg at 100 m and approximately 15 μmol / kg at approximately 250 m. In winter, coastal upwelling carries nutrient-rich seawater to shallower depths, improving nutrient availability. In contrast, nutrient levels are generally low in summer and autumn, with the exception of typhoon events, which cause significant vertical mixing and consequently increase surface nutrient concentrations.

[0055] 4. Calculation methods for Net Primary Production (NPP) and other data

[0056] Net primary production (NPP) of seaweed at the test site is evaluated using two complementary methods to ensure the robustness and cross-validation of the results.

[0057] The first method estimates NPP from the net change in seaweed biomass. For each cultivated seaweed species, multiple 1m cultivation lines are maintained. The biomass on these lines is weighed monthly. The average weight change between replication lines is used to represent the growth of each cultivated species in the seaweed cultivation and monitoring system. NPP is given by the following formula NPPi = ΔNCWi × (1 - WCi) × CCi It is calculated using, where, NPPi is the net primary output of species i (g C / m 2 / month) ΔNCWi represents the net change in wet weight (g / m³). 2 / month) WCi is water content fraction. CCi is the carbon content relative to dry weight.

[0058] This method provides an estimate of NPP (Nutritional Profitability) integrated over time under in-situ conditions. However, it is recognized that this method is likely to underestimate true NPP due to potential biomass losses caused by factors such as marine organism feeding.

[0059] The second method directly measures NPP through a sealed bottle culture experiment. Each month, two or three 1g (wet weight) samples are taken from each seaweed species from the seaweed cultivation and monitoring system. Each sample is cultured in 1-liter clear and dark bottles. These bottles are filled with seawater directly collected from the test site. A control bottle containing only seawater collected from the test site is also prepared and cultured along with these samples. The oxygen concentration in the bottles is continuously monitored over a 6-hour culture period. In addition, seawater samples are taken from all bottles before and after culture to measure dissolved inorganic carbon (DIC) and total alkalinity (TA). NPP is calculated using the following formula: NPPi=((DICidark-DICilight) seaweed-(DICidark-DICilight) control)×1L÷1g×12g / mol×(12hr / 6hr))×Coveragei×30 It is calculated using, where, The ΔDIC value represents the change in DIC concentration between light culture and dark culture. Coveragei is the seaweed biomass of species i (g wet weight / m³). 2 )

[0060] During the light culture period, DIC decreases due to pure photosynthesis by seaweed. Conversely, during the dark culture period, DIC concentration increases due to respiration by seaweed. To identify the DIC change due to the metabolic activity of seaweed, a control value (value obtained from a bottle containing only seawater) is subtracted. For the calculation, a diurnal cycle consisting of a 12-hour light period and a 12-hour dark period is assumed, with photosynthesis occurring only during the light period and respiration occurring at a constant rate throughout the entire 24-hour diurnal cycle. Oxygen measurements are used as a complementary dataset to constrain the DIC-based estimate, as photosynthesis consumes DIC and releases O2 according to stoichiometric ratios.

[0061] This second method provides a direct measurement of NPP unaffected by feeding. However, this method only represents a short-term snapshot of productivity and may not adequately capture the average state under real-world conditions over a longer period.

[0062] Despite the inherent uncertainties of each method, the average NPP values ​​obtained from both methods show good agreement in this experiment. This agreement provides high confidence in the robustness and reliability of the results, demonstrating the effectiveness of seaweed cultivation and monitoring systems.

[0063] B. Equipment design

[0064] This section details the preferred range of structural dimensions, variations in spacing, and alternative material types for seaweed cultivation and monitoring systems, as well as the rationale for specific design choices regarding tube nets and collection devices.

[0065] 1. Optimal dimensions, spacing, and alternative materials for system components.

[0066] The seaweed cultivation and monitoring system incorporates at least one seaweed cultivation module, which comprises three main components: a support structure, a net structure, and a sediment collection device.

[0067] The system features a support structure designed to be installed on the sea surface within a designated area. The support structure includes a frame and a vertical structure; the frame is suspended by the vertical structure, which includes floating members and anchor members connected by ropes. The dimensions of the frame in the current test configuration are 30 meters x 10 meters, but these dimensions are highly adjustable. These dimensions can be adjusted based on specific seabed topography, the target aquaculture area, and local environmental conditions. The frame of this structure is constructed using PE ropes, providing a flexible yet robust base. EVA foam floating units are attached along the PE ropes at 750 mm intervals to ensure buoyancy and proper positioning. It should be noted that these EVA foam floating units can be replaced with other floating materials, such as plastic floats, that provide equivalent buoyancy, depending on material availability, cost-effectiveness, and desired durability. The floating members are configured to maintain the shape and stability of the frame. The floating members are installed 10 to 40 meters outside each of the four corners of the frame by nylon ropes, forming floating platforms that maintain the frame in a substantially rectangular shape. Each floating platform consists of four 100 mm cylindrical plastic floats, which are connected in series. Similar to the floats on the frame, these plastic floats can be replaced with EVA floats or other floats with equivalent buoyancy if necessary. Next, each corner of the frame is connected to anchor members on the seabed using PE ropes. These ropes are kept under tension, thereby maintaining the overall shape and structural integrity of the frame against currents and waves. The anchor members connect the floating members to ballast stones using PE ropes, fixing the entire system to the seabed. Each ballast stone has a weight of 3 tons in air and consists of rocks firmly contained in PE mesh bags. These ballast stones are strategically placed on the seabed directly beneath the frame to function as effective anchors.To further improve durability, especially against extreme weather events such as typhoons, ballast stones can be replaced with other materials of equal or greater weight, thereby ensuring that the system remains in place even under harsh weather conditions.

[0068] 2. Rationale for selecting the type of tube net and substrate

[0069] To cultivate seaweed, HDPE mesh sheets were used to surround the plants. However, these sheets proved susceptible to damage under stress, resulting in frequent breakage. After extensive improvements, the PE mesh sheets are now cleverly formed into 80mm diameter tubular nets. This tubular design significantly improves durability and promotes optimal seaweed growth by providing a more protected and stable environment.

[0070] A key design improvement involves firmly securing 10mm diameter nylon ropes parallel to the top of each tube net. These nylon ropes bear the main load and are designed to securely connect the tube nets to the frame. By tying loops to both ends of the nylon ropes and attaching them to shackles, the tube nets can be easily suspended from the structural frame. This modular suspension system facilitates installation, maintenance, and harvesting.

[0071] The mesh size of the tube nets is carefully selected to suit the specific seaweed species being cultivated, thereby ensuring optimal growth and retention of the seaweed. For example, 40mm mesh is currently used for Sarcodia suiae, while other species such as Eucheuma perplexum, Gracilaria perplexa, Ulva reticulata, and Caulerpa microphysa are cultivated using 20mm mesh tube nets. The substrate for seaweed attachment is essentially the inner surface of these tube nets, into which seaweed spores or julienned thallus are introduced to initiate growth.

[0072] 3. Placement and number of sediment collection devices

[0073] The sediment collection equipment for sediment collection is carefully designed and strategically placed within the system. Each net trap includes the following:

[0074] (1) Upper ring with a diameter of 1 meter This ring functions as a robust connecting component for the upper suspension rope and the lower net trap. Standing 30 cm tall, the stainless steel ring also balances the net trap, maintaining its vertical position in the water column.

[0075] (2) Net trap This consists of a conical plankton net with a fine mesh size of 330 μm and a height of 2 meters. This design is extremely effective in effectively capturing settled particles larger than 330 μm, providing a comprehensive sample of the settled material.

[0076] (3) 1-liter collection cup Positioned at the bottom of the net trap, this cup is designed to hold the collected particles. A 5cm x 10cm rectangular opening is cut into the cup wall and covered with a 150μm mesh screen. This screen allows excess seawater to drain while effectively retaining all collected particles. The overall dimensions of the sediment collection device can be modified as appropriate depending on specific marine conditions or research objectives.

[0077] Net traps are typically suspended from the structural ropes of the seaweed cultivation and monitoring system. For comprehensive monitoring, they are usually installed in the center and on both sides of the platform, for a total of three. They are positioned 2 meters below the frame or net structure to specifically capture material originating from the seaweed cultivation and monitoring system. A sinker weighing 5-10 kg is attached to the bottom of each net trap to maintain its vertical position in the water column and prevent it from being swept away.

[0078] Each sediment collection device is typically installed for 6 to 24 hours to maintain the freshness and integrity of the collected material. If a longer installation period is required (e.g., continuous monitoring over several days), it may be necessary to add preservatives or toxins to the collection cups to prevent the decomposition of the collected samples.

[0079] Importantly, sediment collection devices are primarily used for monitoring purposes, specifically to assess the health, productivity, and carbon sequestration of seaweed. Therefore, if monitoring is not required in a particular aquaculture operation, these net traps can be completely omitted from the system, thereby simplifying installation and reducing operating costs.

[0080] C. Experimental Results

[0081] This section details the analytical methods for collected samples and the calculation methods for key indicators such as precipitated carbon flux, providing insights into the performance and environmental impact of seaweed cultivation systems.

[0082] 1. Quantification of collected substances

[0083] To facilitate comparative analysis of sediment, sediment collection devices are installed both inside and outside the seaweed cultivation and monitoring systems. After collection, the material recovered from the collection bottles undergoes a multi-stage size fractionation process to separate it into three categories: >2000 μm, 500-2000 μm, and <500 μm.

[0084] Within the 2000 μm fraction, visible seaweed residue is carefully sorted by hand, weighed, freeze-dried, and then analyzed for carbon content. Since the majority of seaweed residue is contained within this larger size fraction, its contribution is significant in estimating total settling seaweed biomass.

[0085] The remaining precipitates in all three size fractions are then filtered onto pre-combusted fiberglass filters. These filters are first treated with a 10% hydrochloric acid solution to remove carbonate minerals, ensuring that subsequent analysis reflects organic carbon. After acid treatment, these filters are freeze-dried and analyzed for carbon and nitrogen content, as well as carbon and nitrogen isotopic composition.

[0086] Seaweed residue typically has a higher carbon-to-nitrogen ratio (C:N ratio) and lower delta-ion compared to other marine sediment particles. 13 The carbon content is shown. These distinct chemical and isotopic properties serve as effective tracers, allowing for accurate estimation of the contribution of smaller seaweed residues to the total sediment. Through these comprehensive analyses, the precise carbon content of both seaweed-derived and non-seaweed-derived sediments collected from within and outside seaweed cultivation and monitoring systems is obtained.

[0087] 2. Method for calculating precipitated carbon flux and carbon sequestration

[0088] Based on the detailed analysis described above, the organic carbon content associated with seaweed-derived and non-seaweed-derived residues will be obtained during the installation period of each sediment collection device. This important information will then be used to determine the precipitated carbon flux (gC / m³). 2 This is used to calculate the carbon-to-energy ratio ( / hr). This is achieved by dividing the total amount of carbon collected by the opening area of ​​the sediment collection device and its installation period (in hours).

[0089] Since sediment collection devices are strategically installed directly below the seaweed platform (specifically 2m below) to maximize the collection of vertical sediment while minimizing the effects of horizontal transport, it is assumed that the opening area of ​​the trap approximates the effective collection area in these installations. However, it should be noted that in installations in deeper waters, the effects of horizontal transport may be more pronounced, and the effective collection area may need to be adjusted accordingly to ensure accurate flux calculations.

[0090] To accurately estimate the net contribution of seaweed cultivation to settling biomass, baseline settling carbon flux measured by traps installed outside the platform is subtracted from the settling flux observed directly beneath the seaweed platform. This comparison method effectively separates carbon flux directly attributable to the operation of seaweed cultivation and monitoring systems.

[0091] For a robust and representative assessment of the sedimentation algal carbon flux, it is desirable to conduct monitoring multiple times throughout the year to obtain average estimates. At a minimum, monthly monitoring is necessary. This frequency allows for the capture of significant seasonal variations in the sedimentation flux, which are often related to changes in algal growth patterns and fluctuating environmental conditions.

[0092] It is important to note that under extreme weather conditions such as typhoons, it may not be possible to install sediment collection devices due to the rapid and significant removal of seaweed biomass. To address such extreme weather events, including typhoons, compensatory methods are applied to estimate seaweed carbon loss by comparing seaweed biomass before and after each event. This estimated loss is then incorporated into an overall calculation of the contribution of seaweed cultivation and monitoring systems to carbon sequestration, providing a more complete picture of their environmental impact.

[0093] D. Conclusion

[0094] I. Comparison with conventional seaweed cultivation equipment / technology

[0095] Most existing seaweed cultivation technologies are designed primarily for shallow waters and relatively stable marine conditions. For example, in many Southeast Asian countries, seaweed is commonly cultivated directly in sediments at depths of less than 1 meter. In East Asian countries such as South Korea and China, kelp is usually grown on single-row systems extending offshore. These conventional methods are inherently dependent on specific geographical and calm water conditions, thereby significantly limiting the spatial scope and scalability of seaweed cultivation efforts.

[0096] In contrast, seaweed farming for the purpose of sedimentation biomass for carbon sequestration requires robust infrastructure that can be installed near deep-sea areas and is designed to withstand strong currents and harsh open ocean conditions. The seaweed farming system described herein features an innovative tubular mesh design and offers several key advantages over conventional methods. These advantages include superior wave resistance, UV resistance, low shading, excellent seawater exchange, and reusability. This design is particularly well-suited to deep-sea environments, allowing seaweed to grow outward through mesh openings and maximizing biomass production.

[0097] The system design described herein has undergone rigorous testing under extreme conditions and has been demonstrated to withstand strong currents and waves up to 17 meters high during typhoons. This durability makes it particularly suitable for expanding seaweed cultivation beyond conventional coastal areas to more open, high-energy offshore locations.

[0098] Furthermore, a key characteristic of this system is its integrated use of sediment collection equipment to quantify settled seaweed biomass and carbon transport into the deep sea. This direct measurement capability is important, directly supporting its application to large-scale marine carbon sequestration strategies and providing verifiable data on carbon removal.

[0099] II. Methods and Applications

[0100] This section details practical methods for seaweed harvesting, the reusability of cultivation substrates, and methodologies for quantifying carbon dioxide sequestration.

[0101] A. Harvesting of cultivated seaweed

[0102] Seaweed that grows beyond the tubular net can be harvested manually or using automated machinery. This newly grown biomass can be efficiently collected and used for a variety of purposes, including reseeding in a new aquaculture cycle or as a raw material for diverse applications such as bioenergy, food, or pharmaceuticals.

[0103] B. Reusability of the substrate within the tube net

[0104] The seaweed remaining within the tube net can be efficiently processed. It can be shredded into smaller pieces using automated equipment and then collected for various uses to prevent waste generation. After the remaining seaweed is removed, the tube net is thoroughly cleaned with automated brushes and reused in subsequent aquaculture cycles, significantly improving the sustainability and cost-effectiveness of the system. Alternatively, in certain aquaculture strategies, seaweed can be intentionally left in the tube net to allow for longer growth periods or specific biomass development, enabling continuous growth.

[0105] Quantification of C.CO2 sequestration

[0106] In this specification, carbon dioxide removal (CDR) by offshore seaweed cultivation is defined as the total amount of particulate organic carbon (POC) and dissolved organic carbon (DOC) ultimately stored in marine sediments or in the deep sea at depths of 200 m or less. This definition is consistent with the reliable prior research by Krause-Jensen and Duarte (2016), as well as the guidelines of the Fisheries Agency of Japan, and has also been adopted by NOAA and the U.S. National Academicians, providing a robust framework for carbon calculation.

[0107] Under this comprehensive framework, carbon sequestration is 1. The proportion of particulate carbon buried in shallow-sea sediments, 2. The proportion of particulate carbon that is naturally transported to the deep sea at depths of 200m or less. 3. The proportion of dissolved organic carbon that is naturally transported to the deep sea at depths of 200m or less. 4. The proportion of particulate carbon that has been intentionally deposited into the deep sea by artificial means. It contains four main carbon flux components.

[0108] In parallel with these carbon removal estimates, it is crucial to rigorously consider carbon dioxide emissions associated with operational activities, as well as potential ecological impacts, to ensure net positive carbon removal results.

[0109] In order to quantify the total amount of carbon dioxide removed during seaweed cultivation,

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[0110] The proportion of net primary production (NPP) buried in the sediment (f1) can be quantified by constraining the increase in the carbon burial rate in the sediment directly beneath the seaweed cultivation and monitoring system. At this test site, this term (f1) is considered negligible. This is because the test site is located on the upper continental slope, and strong ocean currents rapidly transport seaweed residue to deeper waters, thereby preventing significant long-term burial in shallow-water sediments.

[0111] The proportion of NPP naturally transported to the deep sea (f2) is constrained using the installed net traps. Observations at this test site indicate that approximately 13-23% of NPP naturally separate from the seaweed platform during growth, contributing to this transport to the deep sea.

[0112] The proportion of NPP released as dissolved organic carbon (DOC) and transported below 200m (f3) is constrained through controlled seaweed incubation experiments. Results from this test site suggest that Eucheuma perplexum releases DOC equivalent to 6±5% of its NPP in the initial stages. However, further analysis showed that only about 20% of this DOC remained after about 20 days, meaning that only about 1.8±1.4% of the NPP can be effectively mixed below 200m at this test site.

[0113] The proportion of NPPs (f4) intentionally deposited into the deep sea can be directly quantified by monitoring the deposited biomass using optical and / or acoustic imaging systems, providing an accurate measure of intentional carbon sequestration activity.

[0114] The ecosystem scaling factor (S) takes into account potential changes in carbon flux due to ecological interactions and is constrained through comparative studies of NPPs conducted both inside and outside seaweed farming and monitoring systems, thereby enabling a more accurate overall assessment.

[0115] Finally, carbon dioxide emissions (E) associated with seaweed farming operations can be directly calculated based on the consumption of specific fossil fuels and electricity generated during cultivation, maintenance, and harvesting.

[0116] This disclosure introduces a novel seaweed cultivation and monitoring system designed to overcome the limitations of conventional shallow-sea technologies, making large-scale offshore seaweed cultivation feasible and efficient. Unlike conventional methods that are limited to specific geographical conditions and calm waters, this system is designed for deployment in deep-sea environments and can withstand harsh conditions such as strong currents and large wave heights, as demonstrated by its durability during typhoons with waves reaching 17 meters.

[0117] The key to this technological innovation is a robust support structure featuring a durable frame and vertical support members, secured by anchor members. The net structure includes a dedicated tubular net with integrated nylon ropes and customizable mesh sizes, providing an optimal environment for seaweed growth while improving durability and reusability. This tubular design offers clear advantages in wave resistance, UV resistance, low light blocking, and excellent seawater exchange.

[0118] A key feature of this disclosure is the integrated sediment collection device, such as a conical net trap. These devices are strategically positioned below aquaculture lines, enabling accurate quantification of sinking seaweed biomass and carbon transport into the deep sea. This direct measurement capability is essential for applying the system in marine carbon sequestration strategies and for accurately assessing its environmental impact.

[0119] This system promotes efficient seaweed cultivation methods, including the placement of diverse substrates within the tube net and effective harvesting techniques. Furthermore, the reusability of the tube net and the substrates contained within it enhances the sustainability and economic viability of this system.

[0120] Importantly, this disclosure outlines a comprehensive methodology for quantifying carbon dioxide removal (CDR). This involves detailed calculations of various carbon flux components, including natural and intentional transport of particulate and dissolved organic carbon to deep-sea or sediments. By comparing carbon flux from seaweed to baseline measurements and considering operational emissions, the system provides a robust framework for estimating net carbon sequestration. This innovative approach positions the seaweed farming and monitoring system as a powerful tool for promoting sustainable marine aquaculture and making a significant contribution to global carbon removal efforts. [Explanation of Symbols]

[0121] 1 System 110 Support structure 111 frames 120 Net Structure 130 Sediment Collection Device

Claims

1. A seaweed cultivation and monitoring system, A support structure configured to be installed in a body of water, the support structure including a frame, A net structure configured within the aforementioned frame, wherein the net structure is configured for cultivating seaweed, A sediment collection device is coupled to the net structure and positioned below the net structure, Equipped with, The aforementioned at least one sediment collection device is configured to collect sediment, and is part of a seaweed cultivation and monitoring system.

2. The system according to claim 1, wherein the sediment comprises sedimentary seaweed.

3. The system according to claim 1, wherein the support structure comprises a plurality of vertical support members for supporting the frame.

4. The system according to claim 3, wherein the vertical support members are positioned at the corners of the frame, and each of the vertical support members comprises a floating member and an anchor member, the floating member maintaining a connection with the frame, and the anchor member being fixed to the seabed.

5. The system according to claim 1, wherein the at least one sediment collection device is positioned vertically at least 2 meters below the net structure.

6. The system according to claim 1, wherein the net structure comprises a plurality of tube nets, each tube net having two rings at both ends thereof, and the rings are configured to be coupled to the frame.

7. The system according to claim 6, wherein the plurality of tube nets include a base material configured for cultivating seaweed.

8. The system according to claim 7, wherein the substrate is selected from the group consisting of natural materials, artificial materials, and combinations thereof.

9. The system according to claim 6, wherein the distance between each of the plurality of tube nets is 0.3 m to 2 m.

10. The system according to claim 1, wherein the sediment collection device comprises an upper ring, a net trap, a collection cup, and a sinker.

11. The system according to claim 10, wherein the net trap is substantially conical in shape.

12. The system according to claim 11, wherein the net trap is made of a mesh material having a mesh size of 60 to 500 μm.

13. The system according to claim 11, wherein the length of the net trap can be 2 to 5 times the diameter of the upper ring.

14. The system according to claim 13, wherein the length of the net trap is between 2 m and 5 m.

15. A sediment collection device comprising an upper ring, a net trap, a collection cup, and a sinker.

16. The sediment collection device according to claim 15, wherein the net trap is substantially conical in shape.

17. The sediment collection device according to claim 16, wherein the net trap is made of a mesh material having a mesh size of 60 to 500 μm.

18. The sediment collection device according to claim 16, wherein the length of the net trap can be 2 to 5 times the diameter of the upper ring.

19. The sediment collection device according to claim 18, wherein the length of the net trap is between 2 m and 5 m.

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