TECHNICAL FIELD

[0001] The present disclosure relates to land-based farming of fish and/ or shrimp.

BACKGROUND

[0002] Recirculating aquaculture systems (RAS) can be used to cultivate fish and/ or shrimp. The water in such a system is recirculated and hence needs purification from e.g. generated feces and ammonia. Biofloc technology can be used in order to purify the water in such a system and the system is then named biofloc recirculating aquaculture system or Bio-RAS.

[0003] Biofloc technology is the use of microbes such as bacteria, algae, protozoa and/ or zooplankton to purify water and prevent disease in aquaculture systems. The bioflocs can also serve as feed for the cultivated aquatic species and hence provides a nutritional value to the system.

[0004] CN109744177 A discloses the use of a biofloc reactor separate from the farming tank, wherein the bioflocs are precipitated in the bottom of said biofloc reactor and pumped to the farming tank to be used as fishfeed.

[0005] DE202016000556 Ui discloses a system wherein bioflocs are propagated in a fluidized bed reactor and used as shrimp feed. The biofloc also performs nitrification in the shrimp tank in order to reduce the ammonia concentration.

[0006] CN207948624 U discloses a biofloc recirculating aquaculture system, wherein the water is recirculated to a biofloc reactor during breeding of the fish and post-breeding it is recirculated to the biofloc reactor via a sediment filtration system.

SUMMARY

[0007] The present inventors have realized that there is a need for further development of the Bio-RAS so that the system can be used in temperate climate with lower production costs and improved biosecurity. [0008] The present disclosure aims to provide a method and a system for land- based farming of fish and/ or shrimp that can be used in temperate climates while simultaneously minimizing the waste generated by the system and reducing the need for external feed, additional water and chemical pharmaceuticals.

[0009] Accordingly, there is provided a method for a land-based Biofloc recirculating aquaculture system for farming of fish and/ or shrimp, the method comprises the steps of:

- farming fish and/or shrimp, wherein the fish and/or shrimp optionally consume bioflocs;

- routing feces-containing sediments from the farming step to an aerobic bioreactor;

- anaerobic digestion of sediments from the aerobic bioreactor to obtain digested sediments;

- biofloc propagation in the aerobic bioreactor, wherein digested sediments and feces containing sediments from the farming tank are consumed in the propagation; and

- routing bioflocs from the aerobic bioreactor to the farming step.

[0010] The bioflocs that are generated serve to purify the water in the farming step from e.g., ammonia as it contains nitrogen-consuming microorganisms. The purification of the water occurs in the entire system where the bioflocs are present. The bioflocs may further serve as a nutritional source for the fish and/or shrimp which reduces the need for external feed. In addition, the utilization of bioflocs increase the nutrition, survival, growth, wellbeing, taste of the farmed fish and/or shrimp as well as reduces the amount of water needed.

[0011] Hence, in one embodiment, the fish and/or shrimp consume the biofloc during the farming step. The use of biofloc as a feed source gives rise to a more sustainable feed.

[ooi2]The feces produced by the fish and/ or shrimp in the farming step as well as residual feed that the fish and/or shrimp have not consumed, forms a sediment in the farming tank/s. The sediments are routed together with water from the farming step to the bioreactor and will serve as nutrients for the bioflocs and enables said bioflocs to propagate. [0013] Sediments comprising residues that the bioflocs, fish and/ or shrimp cannot consume are formed in the bioreactor during the propagation of the bioflocs. These sediments are subjected to an anaerobic digestion step and are, thereby, made available, once again, to the bioflocs, fish and/or shrimp for consumption. The digestion step enables the use of the sediments which would otherwise be discarded as waste. Hence, the utilization of the sediments from the bioreactor will minimize the waste generated by the Bio-RAS and further conserve water as this step replaces the need of “bleeding” the system i.e., replacing fouled sediment water with clean water.

[ooi4]In an embodiment of the method, the feces-containing sediments comprise non-consumed bioflocs.

[0015] In an embodiment of the method, the bioflocs comprise microbes and organic substances.

[ooi6]In an embodiment, the method comprises farming fish and shrimp simultaneously.

[0017] In an embodiment, the method comprises farming of tilapia.

[0018] In an embodiment, the method comprises farming of Whiteleg shrimps.

[ooi9]In an embodiment, the method further comprises a step of nitrification of a stream from the aerobic bioreactor to produce a nitrified stream and recirculation of said nitrified stream to the bioreactor, which nitrification is carried out separately from the anaerobic digestion, the propagation in the bioreactor and the farming.

[0020] In an embodiment, the method further comprises internal circulation of a biofloc-containing suspension within the bioreactor.

[002i]In an embodiment, the method further comprises a multiplication step for zooplankton and algae.

[0022] In an embodiment, the method further comprises adding an external feed, such as a starch-based feed, to the farming step. The starch-based feed may comprise a fermented starch source, such as fermented brans, flours, rice, cassava, potato, soya and/or other vegetable sources. [0023] In an embodiment of the method, the temperature in the farming step is 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C.

[0024] In an embodiment of the method, the temperature in the bioreactor is 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C.

[0025] In an embodiment of the method, the temperature in the anaerobic digestion step is 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C.

[0026] In an embodiment of the method, the feces-containing sediments routed from the farming step to the aerobic bioreactor have a concentration of 20 g/L to 500 g/L.

[0027] In an embodiment of the method, the biofloc propagation in the aerobic bioreactor is buffered.

[0028] In an embodiment of the method, the biofloc propagation in the aerobic bioreactor has a pH of 7-8.5, preferably 7.6S.3

[0029] Further, there is provided a land-based Biofloc recirculating aquaculture system for farming of fish and/or shrimp, said system comprising:

- a farming arrangement for farming fish and/or shrimp, comprising an inlet and a sediment outlet;

- a bioreactor for biofloc propagation; and

- a digestor configured to anaerobically digest sediments from the bioreactor, wherein said bioreactor comprises:

(i) at least one inlet connected to the digestor and the sediment outlet of the farming arrangement;

(ii) a sediment outlet connected to digestor; and

(iii) a biofloc outlet connected to the inlet of the farming arrangement.

[0030] The digestor degrades the sediments formed in the bioreactor and makes them available for the bioflocs to consume. The digestor, hence, enables the use of the sediments which would otherwise be regarded as waste and thereby, reduces the waste generated by the system.

[oo3i]In an embodiment of the system, the farming arrangement comprises at least two farming tanks, which may be arranged in series. [0032] In an embodiment of the system, the farming arrangement comprises an additional inlet for an external feed.

[0033] In an embodiment, the system further comprises a multiplication environment for zooplankton and algae.

[0034] In an embodiment of the system, the bioreactor comprises means for internal circulation.

[0035] In an embodiment, the system further comprises a nitrification reactor that is separate from but connected to the bioreactor. Further, the nitrification reactor is typically also separate from the digestor and the farming arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Fig. 1. A land-based bio-RAS for farming Whiteleg shrimps.

[0037] Fig. 2. A land-based bio-RAS for farming Whiteleg shrimps and Tilapia simultaneously.

DETAILED DESCRIPTION

[0038] As a first aspect of the present disclosure, there is provided a method for land-based bio-RAS for farming of fish and/ or shrimp. Bio-RAS is the abbreviation for Biofloc Recirculating Aquaculture System, which is suitable for land- based farming due to the limited need for a supply of clean water.

[0039] The method comprises the steps of:

- farming fish and/or shrimp, wherein the fish and/or shrimp optionally consume bioflocs;

- routing feces-containing sediments from the farming step to an aerobic bioreactor;

- anaerobic digestion of sediments from the aerobic bioreactor to obtain digested sediments;

- biofloc propagation in the aerobic bioreactor, wherein digested sediments and feces containing sediments from the farming tank are consumed in the propagation; and

- routing bioflocs from the aerobic bioreactor to the farming step.

[0040] The method is suitable for farming only fish, such as Tilapia, or only shrimps, such as Whiteleg shrimps. However, there are additional advantages of farming fish and shrimps simultaneously. An advantage is increased shrimp health which can increase the survival rate of the shrimps. Another advantage is an increase in feed efficiency, where the same amount of feed can farm a larger number of fish and shrimps.

[oo4i]In an embodiment, the temperature in the farming step is 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C. If the temperature in the farming step is lower than 20 °C or higher than 34 °C, the fish and/ or shrimp will be more prone to disease.

[0042] In an embodiment, the fish and/or shrimps consume the bioflocs during the farming step. In an embodiment where both fish and shrimps are farmed, one or both may consume biofloc. However, it is not necessary that the fish and/or shrimps consume the biofloc.

[0043] The bioflocs may serve as a nutritional source for the fish and/ or shrimp. Due to the use of bioflocs as a feed source, a reduction in cost can be made due to less need for external feed. It is also a more sustainable feed than conventional fish-meal based feed.

[0044] In an embodiment, an external feed can be added to the farming step. Normally, the external feed comes from a starch source such as brans, flours, rice, cassava, potato, soya and/or other vegetable sources. It is, preferably, fermented in order to be made more available to the fish and/or shrimps.

[0045] During the farming step, pollutants such as ammonia are formed. In a high amount these pollutants become toxic for the fish and/ or shrimps and it is therefore vital to remove them from the system. By utilizing biofloc technology, the bioflocs can consume the ammonia and neutralize it. The purification of the water by ammonia consumption occurs in the entire system where the biofloc is present, however, especially in the bioreactor where the bioflocs are concentrated.

[0046] During the farming step, a sediment is formed at the bottom of the farming arrangement. This sediment contains feces generated from the fish and/ or shrimp, feed that has not been consumed as well as other waste materials. This feces- containing sediment is routed to the bioreactor where it is consumed by the bioflocs and enables their propagation. The feces-containing sediments routed from the farming step to an aerobic bioreactor may have a concentration of 20 g/L to 500 g/L.

[0047] The propagation of the bioflocs occur mostly in the aerobic bioreactor but may also occur during the farming step. The bioflocs can comprise microbes and organic substances which are produced by the microbes. The main microbes are algae, bacteria, zooplankton such as Ciliates, Rotifers and Copepods, nematodes, protozoa, metazoan, fungi, yeasts among others. The microbes then produce organic substances such as organic minerals, phenolic acids, enzymes, antioxidants, natural extracts, oligosaccharides, beta-glucans, vitamins, nucleotides, colorants, and mucus amongst other.

[0048] In an embodiment, the temperature in the bioreactor is 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C.

[0049] In an embodiment, an internal circulation of a bioreactor suspension occurs during the propagation step, creating a turbulent environment inside the bioreactor. A turbulent environment is preferred as it aids in keeping the bioflocs aerated and preventing the bioflocs from settling. If the bioflocs settle, anaerobic zones can be formed and the organic matter in the bioflocs risk to rotten and attract anaerobic bacteria forming toxic substances, due to the lack of oxygen.

[0050] In an embodiment, the suspension in the bioreactor can be buffered. The pH in the bioreactor is 7-8.5, more preferably 7.6S.3. The pH maybe changed in order control the amount of nutrients present and made available to the bioflocs, fish and/ or shrimp.

[0051] During the propagation in the bioreactor, sediments are typically formed at the bottom of the bioreactor. These sediments, which comprises parts of the feces- containing sediments from the farming step that cannot be consumed by the bioflocs, are routed to an anaerobic digestion step. The sediments may for example comprise vegetable fibres and waxes.

[0052] In the digestion step, an anaerobic degradation of the sediments occurs wherein the sediments are broken down to molecules which are more readily soluble in water as well as more readily incorporated into the bioflocs. The molecules that are generated during the digestion can be enzymes, phenolic compounds, sugars, fatty acids, amino acids, and antioxidants. These molecules together can serve as a functional mix or “super food” to the fish and/or shrimp as well as the bioflocs. Organic acids are also generated during the anaerobic digestion step and have an anti-pathogenic effect. The acids can also lower the pH to below 5 during the digestion and thereby enables the production of digestible prebiotic microbes.

[0053] Furthermore, the digestion step allows for the elimination of mycotoxins, antibiotics, pesticides, hormones, and transgenic DNA that might be present in the system.

[0054] The digestion step takes place under denitrification conditions wherein the residence time is typically 4-5 h and the temperature is typically 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C. The anaerobic digestion maybe anaerobic fermentation or may comprise anaerobic fermentation.

[0055] The digested sediments are routed back to the bioreactor and are now made available to be consumed by the bioflocs. The digestion step, hence, further enables the biofloc propagation and reduces the waste generated by the system. The digestion step can be performed continuously or batch-wise.

[0056] The bioflocs generated in the bioreactor are routed to the farming step where they may be consumed by the fish and/ or shrimps. Normally, the bioflocs routed to the farming step are not completely consumed therein. Hence, the feces- containing sediments (routed from the farming step to the aerobic reactor) typically comprises non-consumed bioflocs. In an embodiment, the farmed fish and/ or shrimps do not consume bioflocs. The bioflocs still serve to purify the water in the farming step from e.g., ammonia as it contains nitrogen-consuming microorganisms as well as increase the nutrition, survival, growth, wellbeing and taste of the farmed fish and/ or shrimp.

[0057] Nitrification typically occurs continuously in the entire system where the bioflocs are present, however, there can be a need for an additional nitrification step. The bio-RAS method can, therefore, further comprise a step of nitrifying a stream from the aerobic bioreactor to produce a nitrified stream which is recirculated back to the bioreactor. This step can be performed batch-wise as needed, i.e., when there is a further need for removal of nitrogen and/or a need for a fast removal of nitrogen. This step is performed separately from the anaerobic digestion step and the propagation step in the bioreactor.

[0058] In an embodiment, the method further comprises a multiplication step for zooplankton and algae that is separate from the propagation of the bioflocs in the bioreactor. The zooplankton are preferably rotifer and copepods; and the algae is preferably chlorella. The multiplication environment allows for more control of the zooplankton and algae due to pure cultures.

[0059] As a second aspect a land-based Biofloc recirculating aquaculture system for farming of fish and/or shrimp, said system comprising:

- a farming arrangement for farming fish and/or shrimp, comprising an inlet and a sediment outlet;

- a bioreactor for biofloc propagation; and

- a digestor configured to anaerobically digest sediments from the bioreactor, wherein said bioreactor comprises:

(i) at least one inlet connected to the digestor and the sediment outlet of the farming arrangement;

(ii) a sediment outlet connected to the digestor; and

(iii) a biofloc outlet connected to the inlet of the farming arrangement.

[0060] The farming arrangement typically comprises at least one tank, preferably at least two tanks, such as at least two tanks arranged in series. The farming of fish and/or shrimps occurs in said tank/s. In the embodiment wherein the farming arrangement comprises one tank, said tank is connected to the bioreactor via an inlet and an outlet. It the embodiment wherein the farming arrangement comprising multiple tanks arranged in series, the first tank is connected to the bioreactor via an inlet and the last tank in the series is connected to the bioreactor via an outlet. When at least two tanks are used, they can be used to farm shrimps, such as Whiteleg shrimps, in one tank and fish, such as Tilapia, in the other.

[oo6i]In an embodiment, the farming arrangement further comprises an additional inlet for external feed from starch-based sources such as brans, flours, rice, cassava, potato, soya and/or other vegetable sources. The additional feed is preferably fermented and can be added as needed. [0062] The system comprises a bioreactor in which propagation of the bioflocs occur. The bioreactor creates an environment suitable for the propagation of the bioflocs.

[0063] In an embodiment, the temperature in the bioreactor is 20-34 °C, preferably, 28-33 °C, most preferably 32-33 °C.

[0064] In a further embodiment, the suspension in the bioreactor is buffered to a pH of 7-8.5, preferably 7.6S.3.

[0065] In an embodiment, the bioreactor comprises means for internal circulation. This means can be e.g., a pump and/or a propeller which recirculates the biofloc containing suspension and creates a turbulent environment inside the bioreactor. A turbulent flow is preferred as it aids in keeping the bioflocs aerated and preventing the bioflocs from settling. The pump creates the recirculation by pumping the suspension from the bottom of the bioreactor to the top while the propeller stirs the suspension within the bioreactor.

[0066] In one embodiment, the bioreactor is connected to a multiplication environment for zooplankton and algae via an outlet. The multiplication environment is further connected to the farming arrangement via an outlet. The zooplankton are preferably rotifer and copepods; and the algae is preferably chlorella. The multiplication environment allows for more control of the zooplankton and algae due to pure cultures.

[0067] In an embodiment, the bioreactor is designed to promote the sedimentation of matter in the bioreactor suspension that the bioflocs cannot consume. This formed sediment is routed from the bioreactor to a digestor.

[0068] The digestor is connected to the bioreactor via an inlet and an outlet. The sediments routed to the digestor are subjected to an anaerobic digestion (degradation) which renders the sediments more available for the bioflocs to consume. Once the sediments have been digested, they are routed back to the bioreactor and can be consumed by the bioflocs.

[0069] In an embodiment, the system further comprises a nitrification reactor connected to the bioreactor by means of an inlet and an outlet. Said nitrification reactor can be employed when necessary, i.e., when there is a further need for removal of nitrogen and/or the need for a fast removal of nitrogen.

[0070] In an embodiment, the anaerobically digested sediments may be routed from the digestor to the farming arrangement, in addition to routing them to the bioreactor. Likewise, the feces-containing sediments may be routed from the farming arrangement directly to the digestor, in addition to routing them to the bioreactor.

EXAMPLES

Example 1

[0071] Fig. 1 shows a specific embodiment wherein the farming arrangement 100 comprises one tank 101 for culturing Whiteleg shrimps. The tank 101 is connected to an aerobic bioreactor 102 via an outlet 103 at the bottom of said tank 101. During the farming of the shrimps, sediments are formed at the bottom of the tank 101, which sediments comprise excess feed, feces, and other waste materials. These sediments and water from the tank 101 are routed to the aerobic bioreactor 102 with a flow rate of 20 g/L -500 g/L. Inside the bioreactor 102, a propagation of the bioflocs occur under turbulent conditions wherein the bioflocs consume parts of the sediments. During the propagation of the bioflocs in the bioreactor 102, heavy sediments are formed at the bottom of the bioreactor 102. These sediments comprise organic material that cannot be consumed by the bioflocs. Hence, these sediments are routed to a digestor 104, in which an anaerobic degradation of the sediments occurs. This degradation (digestion) makes the sediments more available to the bioflocs. The degraded sediments are routed back to the aerobic bioreactor 102 and (at least partly) consumed by the bioflocs. The suspension from the bioreactor 102 comprising the propagated bioflocs is routed back to the shrimp tank 101 to be used as feed for the shrimps as well as for purification of the water inside the farming tank 101. Fig. 1 further depicts an additional feed 105 of fermented starch to the farming tank. This feed is obtained from a feed fermentor 106, in which a starch-containing material is fermented. The additional feed 105 is typically not added continuously but rather added as needed. Example 2

[0072] Fig. 2 depicts a system 200 for farming of Whiteleg shrimp and

Tilapia. A first tank 201 is used to farm Whiteleg shrimp and is connected via an outlet 202 at the bottom of said tank 201 to a second tank 203 used to farm Tilapia. The second tank 203 is then connected via an outlet 204 at the bottom of said tank 203 to a bioreactor 205. During the farming, sediments are formed at the bottom of the second tank 203, which comprise excess feed, feces, and other waste materials. These sediments and water from the second tank 203 are routed to the aerobic bioreactor 205 at a flow rate of 20 g/L -500 g/L. Inside the bioreactor 205, a propagation of the bioflocs occur under turbulent conditions wherein the bioflocs consume the sediments. During the propagation of the bioflocs in the bioreactor 205, heavy sediments are formed at the bottom of the bioreactor 205. These sediments, which comprise organic material that cannot be consumed by the bioflocs, are routed to a digestor 206, in which an anaerobic degradation of the sediments occurs. This degradation (digestion) makes the sediments more available to the bioflocs. The degraded sediments are routed back to the aerobic bioreactor 205 and consumed by the bioflocs. The suspension from the bioreactor comprising the propagated bioflocs is routed to the first tank 201 to be used as feed for the shrimps and Tilapia as well as for purification of the water inside the tanks 201, 203. Fig. 2 further depicts an additional feed 207 of fermented starch, which ca be added to one or both of the farming tanks 201, 203. This feed 207 is obtained from a feed fermentor 208, in which a starch-containing material is fermented. The additional feed 207 is typically not added continuously but rather added as needed.

[0073] The farming of Whiteleg shrimps together with Tilapia can increase shrimp survival from 60 % to 95 % and feed efficiency from 10 kg of feed => 5 kg of product (shrimps) to 10 kg of feed => 9 kg of product (6 kg shrimps+3 kg Tilapia).