WO2021251814A1 - Seaweed cultivation by sprinkler irrigation: improved apparatus and method of use - Google Patents

Abstract

The present invention relates to a land-based aquaculture system for seaweed and, in particular, to a land-based aquaculture apparatus and the operation thereof. It also provides a method for harvesting the seaweed material applied to a structure for cultivation by sprinkler irrigation in which a support net is attached to a support frame and a growth net supporting the crop is placed on top of the support net.

Description

PROVISIONAL NORTH AMERICAN PATENT APPLICATION

Spray Algae Culture: Improved Apparatus and Method of Use

Field of Invention

The present invention relates to a terrestrial aquaculture system for algae and, in particular, to a terrestrial aquaculture apparatus and its operation.

Art Background

Humans have been consuming macro-marine algae (seaweed) for a long time, yet they do not make up a large part of the modern diet. On the other hand, interest in algae has been growing as more people interested in improving health or discovering new appearances and flavors appreciate them.

As the demand for seaweed has increased, the value of improvements in seaweed farming methods has become apparent. Wild harvesting continues to be an important source of seaweed to meet the growing demand worldwide. However, wild collection uses a limited seasonal resource subject to contamination and is not well suited to large-scale production with year-round availability.

There are several technologies available for growing algae. Spores or vegetative fragments can be sown on ropes, and ropes can be suspended in favorable locations in the ocean, in estuaries, or in land ponds. In the latter case, the crop can be fertilized for faster growth. Alternatively, the culture can be confined in a floating cage in a favorable location and fertilized by spraying it with a nutrient solution. Algae can be grown loose in tanks or ponds with sufficient water circulation to keep them suspended and moving in the water column. The algae can be grown in tanks or ponds attached to ropes or cords. The algae can be grown in sand or screens with a seawater spray to keep them hydrated. Algae can be grown as mats for water remediation.

These various methods have different advantages and disadvantages related to quality, performance, capital investment, labor costs, and other operating costs.

The traditional method, suspended rope culture in open water, can have fairly modest investment requirements if a suitable site is available. The biggest cost is in planting and harvesting labor, which is usually done by hand from boats. Productivity depends on the conditions that are available at a chosen site.

Tanks with fast water circulation are at the other extreme: labor requirements are low, productivity is high with the addition of fertilized water and carbon dioxide, and high light use efficiency. Capital costs are high and operating costs are high. i When looking for an improved design for a growing system, we have found that spray cultivation has the potential to generate more moderate capital and operating costs than the quick-mix cultivation method without incurring the high labor costs of traditional methods.

Spray culture was introduced in 1973 by Chapman (Robledo and García-Reina 1991, “Algae spray culture technique”, pp. 233-242 in “Cell biotechnology, physiology and intensive culture of algae” and García-Reina eds .), A commercial method was patented (Moeller and Hunt, 1980 "Process and apparatus for the commercial cultivation of marine and freshwater hydrophytes", US patent 4,209,943) and the use of an early form of the method was pursued. commercially by Hydrobotanicals Company from 1979 to 1981 (Robledo and García-Reina 1991, “Algae spray culture technique”, pp. 233-242 in “Cell biotechnology, physiology and intensive culture of algae” and García-Reina eds.) , But without commercial success.

Several variations of spray culture have been described. We are particularly interested in a sprinkler culture system that has a water inlet, at least one pump to deliver water to the facility for crop growth, at least one recirculation pump to provide a water spray that provides essentially coverage complete of the growing area, a support system that supports the crop over a water collection channel so that the water that is drained from the crop is delivered to the recirculation pump, a drain or pump that allows a quantity to be discharged regulated water to a water discharge area, such as a holding pond and means of delivering fertilizer to the water circulating in the growing facility.

With several improvements to previous designs, we believe this method will provide the best combination of high quality, reliability, and low cost for aquatic plants in general and seaweed in particular, including Ulva, Porphyra, and other commercial varieties.

Advantages of the spray cultivation method

Spray cultivation does not require water recirculation, but water recirculation is easily incorporated into the design of the spray cultivation system. With recirculation of water in a spray culture system, the volume of seawater required for operation is low, determined by the rate of evaporation. The water discharge must be sufficient to avoid excess salinity. The target salinity value depends on the particular needs of the algae species being grown. If convenient, fresh water can also be used to control salinity. The reason a low seawater volume requirement is desirable, in addition to reduced pumping costs, is that seawater intakes can be expensive to build, difficult to operate, and a serious limitation on where they can be locate the facility. Conventional intensive mixing systems can use water recirculation to reduce seawater intake and seawater pumping costs.

The volume of water in a spray culture is very low. The water film is constantly being renewed, but it is very thin, so getting moving water into contact with the crop is very economical. In contrast, in a highly mixed conventional system, the cost of generating turbulent flow in large volumes of water is substantial and represents It is a significant operating cost. The flow of water in spray culture is turbulent, but the volume of water is orders of magnitude less. As a result, the cost of pumping in spray culture, while still a cost factor, is greatly reduced compared to a turbulent pond.

Spray culture uses a small volume of water, so it is practical to physically or chemically sterilize incoming water and filter recycled water without incurring higher operating costs. As a result, the biomass of algae grown in spray culture is very clean. This eliminates the danger of crop loss or decreased yield due to the presence of unwanted invasive species and results in a very high quality crop that does not require post-harvest cleaning.

The low volume of water required by spray culture makes it feasible to operate with modest inputs of seawater. Large intakes of seawater and the location of operations near the coast are not required. Land use in coastal areas is often highly regulated, so it is a great advantage to be able to operate further inland.

Spray cultivation has the potential for very high nutrient use efficiency. High efficiency in the use of nutrients minimizes the cost of fertilizers and avoids overloading the environment with nutrient contamination.

The large air / water interface in spray culture results in a near equilibrium concentration of carbon dioxide in the aqueous phase and makes carbon dioxide supplementation unnecessary. The yields are quite respectable, close to those of highly mixed C02 supplemented cultures.

Disadvantages of the spray cultivation method.

Spray cultivation does not lend itself to pumping planting and harvesting the way a highly mixed crop does, but requires planting and harvesting from a supporting structure. Spray cultivation requires a significant investment in support structure and plumbing.

In this disclosure, we disclose design and operational details that retain the advantages of spray culture and mitigate the disadvantages, resulting in a superior apparatus and method for growing algae.

Disclosure of the invention

Some issues that we have addressed in our design are: (1) construction cost of the grow facility, (2) convenience of the harvesting system to minimize cost of harvesting, and (3) reliability and energy expenditure of the sprinkler system.

Construction cost.

In general, a spray culture system of the type we have chosen requires a waterproof liner to capture the water that drains from the crop, a plumbing system and spray nozzles to provide a sufficiently uniform spray of water and a medium to support the culture. It is often helpful to have walls high enough to prevent the wind from causing distortions in the spray pattern. Such distortions can result in failure to irrigate parts of the crop with consequent reductions in yield and also loss of water in the areas surrounding the crop structure.

We have devised a construction design that is quickly and easily assembled from commonly available materials. Key features are (a) the use of PVC cables or pipes to support the perimeter of the waterproof liner with (b) rebar stakes at intervals to secure the structure to the ground, (c) the use of dual function PVC pipes to deliver water to the spray nozzles and support the removable screens that support the crop. All parts and materials are commonly available as supplies for aquaculture, irrigation, or construction. Assembly requires only ordinary plumbing and construction tools. It is fast, simple and inexpensive. Once built, the only maintenance required is regular cleaning and painting of the PVC exposed to the sun. The plastic liner will need to be replaced at intervals depending on the quality. A typical expectation is a useful life of approximately 20 years, so replacement cost is a minor consideration in the total cost of algae production.

This design can be implemented on flat or gently sloping terrain with access to a suitable water source and adequate drainage.

The structure consists of a waterproof lining held in the shape of a box by a PVC frame that is fixed in place with stakes; an underground tank or reservoir; a recirculation pump; a PVC pipe structure (frame); thick plastic mesh that is fixed to the frame (support mesh); and fine plastic mesh that supports the crop (growth mesh). The waterproof coating traps the water after it has been sprayed on the crop and drains into the reservoir. The frame conducts the water to the spray nozzles that are mounted on the frame and provides a structure to which the support mesh is attached. The pump returns water to the support frame. The support mesh is attached to the frame. The grow net fits over the support net, but is not clamped, so it can be easily removed for harvesting, planting and cleaning operations.

Description of Drawings and their Document Reference Numbers

Document Reference Numbers:

No 1. Waterproof coating

No 2. Support frame

No 3. Stakes

No 4. Underground tank

No5. Recirculation pump

No 6. Support mesh

No 7. Growth mesh

No8. Vertical perimeter frame

No 9. Spray nozzles

NolO. Clear plastic barrier DESCRIPTION OF THE DRAWINGS:

Figure "A" is a top view drawing of a specific spray culture structure:

1.It has dimensions of 2.20 meters wide by 7.70 meters long.

2. The frame has a waterproof liner (# 1) folded and supported in a box shape by a 2-inch PVC frame (# 2).

3. The box-shaped waterproof liner (# 1) is fixed in place with 3/8-inch rebar stakes 1.5 meter long (# 3).

4. The box-shaped watertight liner (Nol) is held vertically in place by a ½-inch PVC perimeter frame (# 8).

5. The main support frame is also a closed circuit irrigation and support structure with 3 interconnected main lines, it is made of 2.0 inch PVC pipe (No. 8). The function of this structure is to lead water to the sprinkler nozzles (No. 9) to irrigate the crop.

6. An underground tank (No.4) is connected to the main support frame (No.8), it supports a recirculation pump (No5) to provide irrigation water to the system.

7 The support mesh is the material that covers the entire production area, it is a thick plastic mesh (No. 6) that is fixed to the support frame.

8. The growing mesh is made of a fine plastic mesh that supports the culture (No7). Figure "B" is a cross section of the system and the subsoil where it is placed:

1. It has dimensions of 1.50 meters high by 7.70 meters long.

2. The box-shaped waterproof liner (# 1) is fixed in place with 3/8-inch rod stakes 1.5 meters long (# 3). These are placed one every 1.1 meters around the perimeter. Rod stakes are driven 0.75 meters into the ground and 0.75 meters left on the surface to hold the structure in place

3. A clear plastic barrier that surrounds the entire perimeter (NolO) is attached to the 3/8 inch rod stakes 0.75 meter high (# 3).

4. The box-shaped waterproof liner (# 1) is held vertically in place by a ½-inch PVC perimeter frame (# 11).

5. The main support frame is also a closed circuit irrigation and support structure, it is made of 2.0 inch PVC pipe (No. 8)

6. The growing mesh is made of a fine plastic mesh that supports the culture (No7).

Brief description of the construction of the apparatus.

The structure is fed by a water source. For seaweed like Ulva, saline water should be provided in a salinity range of 10 to 40 ppt. If desired, it can also be fed by a low salinity water source that can be used to mitigate increased salinity due to evaporation. The structure also has a drain that allows to dispose of the water. The land where the production structure will be placed if necessary is leveled and excavated to have a shallow trench with a slope towards the drainage end of the structure. When the liner is in place, the water drains into a reservoir, so there is little or no standing water in the liner. The edges of the cladding are raised on the perimeter and held in position using suitable structural elements. PVC pipes with suitable fittings are used to build a dual function structure that conducts water and acts as a frame to support a supporting mesh. The support mesh is fixed to the frame. The spray nozzles are installed at intervals in the pipe structure in such a way as to provide substantially uniform spray coverage of the production area. A growth mesh is placed over the support mesh. The growing mesh supports the crop. The growing screen and culture are easily removed from the support screen for harvest. Dual-purpose stakes hold the frame in place and also provide support for installing a wind shield (clear or translucent) that prevents spray water from leaving the production area.

A recirculation pump in the tank provides water to the water distribution system. If desired, additional equipment can provide automatic fertilization, reservoir water level control, water discharge control, and salinity control.

Some advantages of our apparatus and cultivation method:

Moderate capital cost. This system can be assembled by people with normal construction skills from readily available parts and equipment, resulting in low capital investment costs.

Harvest system convenience. The fine meshes that support the crop as it grows are supported by a plastic mesh so that the fine meshes themselves can easily be rolled up with the crop in place and transported to a harvest table. At the harvest table, the crop can be visually inspected and transferred to centrifuge equipment to remove surface water and from there to containers for shipping. Due to the absence of dirt and foreign organisms in the sprinkler system, there is no need to clean or sort

Convenient maintenance. The spray culture system is resistant to contamination by unwanted organisms, but it is possible for diatoms and undesirable fungi to colonize the culture screens. If this occurs, you need a simple method to sterilize the culture mesh. The meshes are lightweight and flexible, so they can be easily stacked or rolled up for transport and sterilization.

Low energy sprinkler system. While the energy requirements for water spray are much lower than for turbulent mixing, it is still advantageous to minimize pumping cost by reducing both spray volume and water pressure to minimal values. The sprinkler system must be sufficient to deliver nutrients and prevent the crop from drying out. Areas not covered by the spray will have low or no productivity. Micro spray nozzles provide the best available combination of low water volume and uniform coverage. Such nozzles are generally designed for a water pressure of at least 15 psi. Some nozzles do not work well at lower pressures, providing a water distribution that is uneven, so parts of the intended spray zone may not be regulated. Others will operate at water pressure as low as 5 psi, even if that is outside the pressure range for which they were designed. Spray nozzles are also susceptible to clogging, and this has deterred some researchers from using them, due to the labor cost of checking nozzles and replacing non-working nozzles. In our experience, a fine mesh filter in conjunction with large diameter distribution pipes largely prevents clogging, so nozzle maintenance is not a significant cost.

Other equipment, such as overhead shower fixtures, can also work well at very low pressure. However, the flow volume per unit area covered required by such accessories is much higher than that of micro-spray, so the total pumping energy is considerably higher.

The spray system lends itself to intermittent use, unlike a highly mixed conventional production system. It can generally be turned off at night without loss of productivity. We have also confirmed the usefulness of intermittent spraying during the day, and our experiments show that a 50% duty cycle gives a somewhat higher performance. With proper plumbing, the use of an intermittent sprinkler can reduce energy use by at least 50%, making energy requirements even lower than observed in Example 3.

Effect of micro-spraying on the morphology of algae. An unexpected effect of growing algae with this apparatus is an altered morphology of the algae. Spray culture resulted in a curlier sheet or filament of Ulva clathrata. It also improved the texture of Ulva lactuca and Porphyraspp. The overall result was a higher quality product because the effect on morphology gives a more interesting appearance and the effect on texture gives a more pleasant eating experience. Short-term trials with Chondruscrispus also showed improved texture in spray culture. Generally, we expect algae grown in spray culture to have a more delicate texture and higher value than those harvested from the wild.

Example 1. Construction of a spray cultivation unit in La Paz, BCS, Mexico.

In this example, we describe the construction of 4 spray cultivation units, each with 10 square meters of cultivation area. For each 10-square-meter cultivation unit, the operations and construction times were:

1. The ground was leveled with a 2% slope and a shallow V-channel. This process was done by hand in 2 hours.

2. The liner was 1mm thick HDP (High Density Polyethylene) which was cut and shaped to make a 2m X 5 X 0.25m box. This is done by cutting, folding and folding only, there is no need to join. Heat was used to make it easier to fold the liner into a box. This process took 2 hours.

3. The sides of the HDP box were scored and bent to fit over a PVC frame. 10 1/4 "holes were drilled spaced around the perimeter. Mark and fold the sides of the HDP box, assembling the PVC frame, drilling the holes and securing the liner to the frame with bolts, nuts and washers took 1 hour.

4. The 2-inch PVC pipe parts of the dual-purpose water distribution and support frame were measured, scored, and cut with a circular saw in 1 hour.

5. The 2-inch PVC frame was assembled using the PVC connectors: Ts, Crosses, 90 ° corners, quick disconnect joints, and a flow valve in 0.75 hours.

6. The 20 m2 of 1 cm x 1 cm plastic mesh (support mesh) were cut to size and fixed to the PVC structure. A 0.5 cm polypropylene cord was used to attach the plastic mesh to the frame in such a way that the plastic mesh was under tension. This process took 4 hrs.

7. Holes to mount spray nozzles to PVC frame were measured, drilled, and tapped. 25 holes were separated by 0.6 m. This took 0.75 hours).

8. 25 spray nozzles (Orbit Irrigation Products, part number 4687867117 1 were fitted in 1 hour.

9. The overspray barrier parts were cut using 12.50 µm of 1mm thick by 0.80m wide clear plastic in 0.5 hours.

10. 9 pieces of ½ inch X 1.5 m steel bars of rebar material were cut with the circular saw in 0.25 hours.

11. 4 pieces of 2.5 m 1.0 m anti-mosquito mesh were measured and cut in 0.25 hrs.

12. The assembly of all the above components of the 10 m2 pond took 1 hour.

13. A hole for the 400 liter water tank was dug by hand in approximately 2 hours.

14. The water supply was connected to the system in 0.025 hrs.

15. Power was connected to the pump and the system was tested and cleaned in 0.25 hours.

The total time was 15.50 h. or 1.55 man hours / m2

Example 2. Cultivation of Ulva clathrata by spray culture

Sowing. The planting material was cut into 1 cm x 1 cm pieces and 500 grams of the cut material was suspended in 15 liters of seawater in a 20 liter bottle. The bottle was shaken to maintain a uniform distribution of the short filaments in the water and the resulting suspension was sprayed on the grow screens to achieve a planting density of 250 grams / m2. This operation was carried out 5 times in the 10 square meters. After planting a growing net, two people carried it horizontally and placed it on the support net in the cultivation apparatus. The sowing process required about 0.75 hours per 10 m2, part of which required 2 people, which resulted in a total work time for sowing of about 0.1 hours / m2.

Harvest. The cultivation system had an area of 10 m2, composed of 4 growth meshes. The meshes were rolled up, placed on a cart, the cart moved to the next mesh, and so on until all meshes were collected. The tights were brought to the harvest table. Once on the processing table, the crop was removed by hand to a low speed centrifuge to remove excess water. Due to the excellent species control with this method, no cleaning was required. After centrifugation, the harvest was transferred by hand to a suitable container for shipment as fresh produce. The total harvest work time for the 10 m2 system was approximately 1 hour or 0.1 hours / m2. Working time per unit dry weight. Almost all the work required for growing Ulva is for planting or harvesting. The labor required for the fertilization, control and maintenance of the system and the laboratory cultivation of the planting material is less than 20% of the total work required. The productivity of a Ulva spray culture in good conditions averages about 20 grams of dry weight per square meter per day over a 21-day growing period. The harvest occurs after about 3 weeks, so the harvest amount is about 420 grams of dry weight. In low productivity seasons, the harvest interval may be longer and the harvest quantity may be somewhat reduced. A reasonable estimate of planting and harvesting work with our method is 30 minutes / kg dry weight, which is acceptable for a high value crop.

Example 3. Cultivation of Ulva lactuca using spray culture

In La Paz, BCS, Mexico Ulva lactuca was grown in March using the spraying apparatus of Example 1 and operations similar to those described in Example 2. The yield after dehydration was 276 grams of wet weight per m2 / day. No dry weight was taken, but the wet weight after dehydration is usually about 8 times the dry weight. The taste and appearance were excellent.

In January and February in Galicia, Spain a 20 square meter spray culture apparatus similar to that described in Example 1 was used. The edges of the HDP liner were folded over a cord attached to the stakes at the perimeter of the production area. instead of a PVC frame. Other aspects of the construction were the same.

The operations were similar to those described in Example 2. The planting material was distributed on the growth mesh, the growth mesh was brought to the support mesh. The algae were subjected to a continuous spray of fertilized seawater with water recycling and sufficient water exchange to maintain salinity between 35 and 40 ppt. After 30 days of culture, the 8 sections of the growth mesh were rolled up and transported to the harvest table where the culture was removed, dehydrated, and then packed for shipment. Energy use by the sprinkler system was similar.

The yield was similar to that of Ulva clathrata, 235 grams of wet weight per square meter per day. No dry weight was taken, but the wet weight after dehydration is usually about 8 times the dry weight. The energy use was 0.67 kwh / kilogram, that is, less than 7 kwh / kg dry weight. The product at harvest was clean and free of visible contaminating organisms. The texture of the product was more delicate than wild harvest, the morphology was more curly, the color was a uniform bright green.

Example 4. Culture of Porphyraspp using spray culture

A spray culture apparatus similar to that described in Example 1 was used. The edges of the HDP liner were folded over a cord attached to the stakes at the perimeter of the production area in place of a PVC frame. Other aspects of the construction were the same. The operations were similar to those described in Example 2. The planting material was distributed on the growth mesh, the growth mesh was brought to the support mesh. The algae were subjected to a continuous spray of fertilized seawater with water recycling and sufficient water exchange to maintain salinity between 35 and 40 ppt. After 21 days of culture, the 8 sections of the growth mesh were rolled up and transported to the harvest table where the culture was removed, dehydrated, and then packed for shipment.

The yield was approximately 108 grams wet weight per square meter per day. The product at harvest was clean and free of visible contaminating organisms. The quality of the product was superior to the wild harvest in terms of texture, color and flavor.

Claims

CLAIMS: 1. A method of construction of a spray culture structure in which a support screen is attached to a support frame and a growth screen that supports the culture is placed on top of the support screen. 2. A method of construction of a spray culture structure in which a support mesh is attached to a support frame made of pipes wherein said support frame also serves to distribute water. 3. A method of constructing a spray culture structure in which lateral movement of the structure is prevented by stakes driven into the ground at the perimeter of the growing area. 4. A method of constructing a spray culture structure in which a transparent or translucent sheet that functions to confine the water spray to the growing area is mounted on stakes at the perimeter of the growing area. 5. A method of construction of a spray culture structure in which an impermeable liner is used to confine water that runs off the crop and in which said liner is folded up at the perimeter to have a box-shaped configuration. . A method of constructing a spray culture structure according to claim 2, wherein the water spray nozzles are mounted directly on the water distribution pipes. A construction method according to claim 3, wherein the stakes are steel stakes using a building material as a reinforcing bar. A construction method according to claim 5, wherein the edges of the waterproof coating are supported by a frame. Said frame may consist solely of perimeter elements resting on the ground, or it may have vertical elements that raise the perimeter elements above ground level. A construction method according to claim 5, wherein the edges of the waterproof liner are supported by a cord. A construction method according to claim 5, wherein the cladding is substantially flat and the edges are raised by a soil berm. 11. A mode of operation of a spray culture apparatus in which drip irrigation micro-sprinklers are used to distribute water and said micro-sprinklers are operated at a pressure between 5 and 10 PSI. 12. A mode of operation of a spray culture apparatus in which a removable growing screen supported by a support screen is used to support the culture. The crop is harvested by rolling up the growing net and transporting it to a processing station. 13. A mode of operation of a spray culture apparatus in which a removable growing screen supported by a support screen is used to support the culture. The culture is planted in a processing station and the planted growth mat is transported to the growth apparatus and placed on the support mat. 14.A method of planting algae material on a spray culture structure in which a support screen is attached to a support frame and a growing screen that supports the culture is attached on top of the support screen: The first operation requires cutting the algae material into small pieces and mixing them in water in a proportion by weight of 20% algae 80% water to use the water as a propellant and to be able to spray the mixture on the seedling growth mesh. The second operation is to use a container, such as a bottle, that can be operated manually by shaking the bottle as a pressure disperser or to use a diaphragm pump as a propellant for the mixture of water and algae particles to apply the material in a manner. uniform over the growing mesh; making a tour over the entire culture mesh and thus obtain a specific and uniform density of the algae material in all production areas. The third operation is to transport the culture mesh with the algae seed material on it to the spray culture structure where it is attached to the support mesh anchored to a support frame. 15. A method of harvesting algae material applied to a spray culture structure in which a support screen is attached to a support frame and a growth screen that supports the culture is attached on top of the support screen: First operation, at the end of the algae development cycle, to carry out the harvest, the cultivation mesh is rolled up with the algae and transported on a wheelbarrow to be taken to a detachment area of the algae attached to the mesh. Second operation, on a table or platform, the culture mesh is spread like a mat with the algae and using a scraper the algae is separated from the culture mesh to complete the harvest.