WO1987004051A1

WO1987004051A1 - Method for the manufacture of fish silage pellets, fish silage pellets manufactured by the method and equipment for the manufacture

Info

Publication number: WO1987004051A1
Application number: PCT/FI1987/000004
Authority: WO
Inventors: Paul Petroff; Matti Uusi-Honko
Original assignee: Paul Petroff
Priority date: 1986-01-13
Filing date: 1987-01-13
Publication date: 1987-07-16
Also published as: DK474187D0; DK474187A; FI860623A0; FI860623A

Abstract

Method and equipment for the manufacture of fish silage pellets. In order that the manufacture of fish silage pellets would be a pro-environmental process so that the phosphorus effluents into natural waters from cultured fish eating the pellets would be remarkably low, the pellets are manufactured according to the invention by a method, which is essentially characterized by the following steps: waste fish and guts are ground into a mass and/or other animal tissues are ground to a mass and/or a mass is made of fish meal by adding water thereto; the mass obtained is mixed with a diluted acid by means of which acid the pH of the mass is adjusted so that the upper limit is a pH still preventing bacterial activity and the lower limit a pH still permitting the activity of the digestive enzymes of the waste fish; to the mass is added fodder meal, necessary vitamins and a binder and it is pressed into pellets.

Description

Method for the manufacture of fish silage pellets, fish silage pellets manufactured by the method and equipment for the manufacture

The invention relates to a method for the manu¬ facture of fish silage pellets. More and more attention is year by year paid to the pollution of the environ¬ ment. The present invention has a preventing effect on the pollution of natural waters. As generally known, phosphorus (P) has a disadvantageous influence on natural waters, because it promotes the eutrophication of waters. Fish breeding establishments cause today a considerable phosphorus stress on waters. According to experts, a phosporus effluent of about 24 kg is directed on waters per each cultured fish ton. This amount of phosphorus is obtained by calculating as follows: for the culture of 1000 kg fish, about 1700 kg dry pellets are needed (silage factor is 1700/1000 = 1,7), the phosphorus content of which is 1,4 %, i.e. the amount of phosphorus is 1700 kg x 1,4 % = 24 kg. When feeding fish, about 15 % of the silage is wasted on account of so-called overfeed, because this part of the si-lage drifts away with water streams so that the fish do not have time to eat it. The real amount of phosphorus coming into the water is thus 1,15 x 24 kg = 28 kg. This amount shall, however, be reduced by the part which is removed from the water in connection with that 1000 kg fish is lifted out of the water to be killed. Because the part mentioned above is 4 kg, 28 - 4 = 24 kg phosphorus remain in the water. If the fish to be cultured is fed with silage pellets manu- factured according to the method of the present inven¬ tion, the silage factor of which pellets is 2,4 and the content of phosphorus 0,36 %, the corresponding amount of phosphorus will without overfeed be 4,6 kg and including possible overfeed 5,5 kg. Thanks to the present method, it is thus possible to manufacture fish silage the phosphorus content of which is remarkably low com- pared with the phosphorus content of the known fish silage, while calculations show that it is possible to reduce phosphorus effluents to about one fifth compared with what they are today per a certain cultured fish amount. To carry out this, the method of the invention is characterized in that a) feedfish and fish guts are ground into a mass and/or other animal tissues are ground into a mass and/ or a mass is made of fish meal by adding water thereto, b) the mass obtained is mixed with a diluted acid consisting of an organic acid and possibly of a mineral acid, by which acid the pH of the mass is adjusted so that the upper limit is a pH still preventing bacterial activity and the lower limit is a pH still permitting the activity of the digestive enzymes of the feedfish and to the mass are added active digestive enzymes in that case that the mass does not include them, c) to the mass is added partly or entirely ripened whole-wheat fodder meal or corresponding meal, d) to the mass are added necessary vitamins and a binder and e) the mass is pressed into pellets after careful mixing. Later on, measures are presented due to which the effluents of phosphorus can be made still remarkably lower than these values. When instead of conventionally used binders, gelatine is used as binder in a pellet manufactured by this method, the phosphorus included in the pellets is in a less water-soluble form, which also is advantageous as to water pollution. A further advan- tageous effect of gelatine is that the sinking speed of a pellet in water is reduced, which decreases overfeed. However, the pellet must sink, because the fishes are not likely to eat floating pellets. By adjusting the oil content of the pellets, it is also possible to influence the sinking speed of the pellet, but in a modest degree only, because the oil content of the pellets shall be within certain limits to be suitable for the fish to be cultured.

In order to prevent the acid mixture added to the fish silage pellet from having an injurious effect on the taste of the fish, the organic acid used accor¬ ding to the invention is formic acid and the mineral acid is sulphuric acid.

The oil and blood coming from the cultured fish of fish breeding establishments pollute waters, too, because the blood from the killing of cultured fish is practically poured directly into the water from the breeding establishment, which is due to the fact that it is expensive to transport the blood far from the breeding establishment. So is often done also with the oil or the fat from the fish. By doing as described above, the eutrophication of water is further promoted, because both blood and oil promote an eutrophication. Also considering the aspects of protection of animals, it is most undesirable to pour the blood into the water, because blood in water causes stress, nervousness and panic feeling in the fish to be cultured, which also has been proved scientifically. On the other hand, said oil poured into water is problematic also, because it drifts to shores and stays there bad-smelling. To solve the last-mentioned problems, the method of the invention is characterized in the features presented in the characterizing part of the dependent claims 3 and 11.

Additionally, the method of the invention has the advantageous property that is has a killing influence on bacteria, salmonella and pathogenes thanks to the relatively low pH used according to the method. The mass manufactured by this method can be called a sterile product and it can be stored at least one year without cooling measures. Further, an advantageous property of the silage pellet manufactured by this method shall be mentioned, i.e. the influence of the pellet on the growing speed of the fish, which is due to the fact that the digestive enzymes of the waste fish which have been ground into the mass begin to digest it and by the action of the acids mentioned above the bones of the waste fish get soft and dissolve, the result being a homogenic emulsion. Consequently, the fish to be cul¬ tured get its feed in a "pre-digested" form, whereby the digestive system of the fish does not need to do this "digestion work" . Though the method of the invention is connected with several favourable effects presented above, its main advantage, however, is that the pollution of natural waters caused by fish culture can be substan¬ tially reduced. Pellets are preferably manufactured on a floating fish breeding establishment, whereby the establishment is characterized in that it comprises a storage container arranged in the control building of the fish breeding establishment to float on water, whereby the container with its contents does not substantially reduce the carrying capacity of the fish breeding establishment.

In the following, the invention is described in detail with reference to the enclosed drawings, where

Figure 1 shows the circulation of phosphorus when 1000 kg fish is cultured by using known fish silage, Figure 2 shows the circulation of phosphorus when 1000 kg fish is cultured by fish silage pellets manufactured by the method of the invention.

Figure 3 shows schematically a fish breeding establishment, which can be used for the manufacture of fish silage pellets made by the method of the invention and

Figure 4 shows a partial illustration of the fish breeding establishment of Figure 3 in somewhat greater detail.

Figure 1 shows a situation prevailing in practice, whereby at the culture of 1000 kg fish by using known fish silage pellets, the silage factor being 1,7, the phosphorus content 1,4 % and the overfeed 15 %, about 28 kg phosphorus will be fed into the water, 4 kg of which is removed together with the fish lifted up to be killed. In this case, the fish culture causes a total effluent of about 24 kg phosphorus into the water system.

Figure 2 shows that at the culture of 1000 kg fish by using fish silage pellets manufactured by the method of the invention, the silage factor being 2,4, the phosphorus content 0,36 % and the overfeed 15 %, only about 9,5 kg phosphorus will be fed into the water, 6,7 kg of which is due to the waste fish, e.g. Baltic herring, and 2,8 kg is included in the grain part of silage. Also in this case, 4 kg phosphorus is removed by lifting up the fish to be killed, whereby the culture of this fish amount causes a total effluent of only about 5,5 kg phosphorus into the water system. If the de-sludging system described later on is used, still about 4,4 kg phosphorus can probably be reduced from the last-mentioned amount of phosphorus, whereby the culture of 1000 kg fish causes a total effluent of as little as about 1 kg phosphorus into the water system. If fish caught in the waters of the fish breeding establishment is used for the manufacture of silage pellets, the result can even be that instead of adding 24 kg as in the case of Figure 1 , actually more than 5 kg phosphorus are removed from the water system. The last-mentioned case is illustrated with broken lines in Figure 2.

In Figure 3, a fish breeding establishment is schematically shown, by means of which fish silage pellets of the invention are preferably manufactured. With reference numeral 1 is marked the building of the establishment, from where the operations of the esta¬ blishment are controlled. The building 1 is surrounded by eight breeding basins 2 delimited by trussed steel beam constructions 3 and floating like the building 1 on pontoons 4. When it is necessary to wath the situa¬ tion of the fish in the basins, e.g. the need of food, it is preferably that the trussed construction 3 at the same time forms a balustrade, whereby it is even in windy weather possible to walk without trouble along the margins of the basins. With reference numeral 5 is presented anelectrically driven jib crane, by means of which bags 6 are lifted up from the basins 2 by using control lines.

In Figure 4 is shown the establishment of Figure 3 in more detail. In the following, the most important operations and equipments of the establishment are examined. Through a pipe 7 having a diameter of about 40 mm, fish silage pellets manufactured at the esta¬ blishment are fed into the water. At the end of the pipe 7 there is a conical plate 8 having a diameter of about 2 m, by means of which fish silage pellets can be fed into the water within a relatively large area. Thanks to the distributing plate 8, tail and fin damages are substantially reduced at the feeding of fish in the basin 2, which damages would appear, if the fish were fed "spotlike" within a very small area. It is assumed that the fish in the basin eat about 90 % of the fish silage fed, whereby the part of overfeed thus is 10 %. Under the basins 2, there is arranged a de-sludging system moving on guide bars 9, which system comprises a fully pneumatic pump 10, when when it is functioning recovers about 80 % of the excrements of the fish and which also recovers fish silage wasted because of over¬ feed. The construction of the pneumatic pump 10 is such that it does not break the excrement and the sludge, but this remains compact, when it is pressed through a flexible tube 11 up to a filter unit comprising two rotating filter mats 12 and 13. The water flowing in the filter basins takes the sludge coming from the flexible tubes 11 towards teh first filter mat 12, the screen size of which is 500 μm, whereby a great part of the sludge sticks to its urface. A suction device 14 sucks the sludge out of the rotating filter mat 12. The sludge getting "between" the filter mat 12 drifts due to the flow of the water towards the right edge of the filter mat 12 and the sludge sticking thereto is at a later stage (when the mat comes to the point of the suction device 14) also sucked away by means of the suction device 14. The finely-powdered sludge drifts towards the second filter basin, in which the same procedures take place as in the first basin. The screen size of the latter filter mat 13 is 200 μm and the suction device related thereto is marked with reference numeral 15. The sludge is moved by means of the suction devices 14 and 15 into transport containers. The sludge recovered in this way is very well suited for use as fertilizer, the fertilizing values of which can be compared with excrements of a hen and which is not so bad-smelling as hen excrements. Thanks to the re¬ covery of the sludge, a great part of phosphorus can additionally be removed from the water (cf. figure 2: 5,5 kg P - 1,1 kg P). It is also possible to dry up the excrement mass by means of infrared line to a dry fertilizer. With the reference numeral 16 is marked a stunning basin for cultured fish, where the fish is stunned by an electric shock or by carbonic acid, from which basin 16 the fish is moved into a blood shedding basin 17. The blood obtained from the basin 17 is pumped to a soilage container 18 and is used to the manufacture of silage pellets. A fish cleaning line is marked with reference numeral 19. The guts are recovered from the cleaning line 19 and are also used to the manufacture of silage pellets. Further, the fish oil is recovered from, the process water of the cleaning line by leading the process water by means of a pump 20 through a flexible tube 21 to the filter unit mentioned above. Naturally, the de-sludging system is not used, when the oil is re¬ covered. The oil is used as a part component at the manufacture of fish silage pellets. The container 18 is the main equipment for the realization of the method of the invention. The container 18 is arranged in the control building 1 to float on the water within a casing 22, which arrangement provides more room in the control building and does not burden its carrying capacity.

Additional room is needed e.g. for the storage of meal and additives. From the container 18 the fish silage mass 8 is pumped into a pellet manufacturing machine. From the machine the pellets are forwarded by water through the pipe 7 to the fish. Of the equipments of

Figure 4 shall further be mentioned an oxidizer general¬ ly marked with reference numeral 23, the purpose of which oxidizer is to add oxygen for the fish, if necess¬ ary, e.g. in calm summer weather or in autumn before the killing of the fish, when the content of oxygen in water may sink. The oxidizer has a cylindrical form and it floats on pontoons 24 and 25. The surface of the cylinder is manufactured of a metal net resistant against corrosion and within the cylinder there is porous, fine granular rock material with a roundish form, e.g. material sold under the trade mark LECASORA. The material of fine structure is arranged immediately between the meshy outer jacket and the likewise meshy inner jacket of the cylinder. There can be more than one inner jacket. The cylinder is arranged to rotate on bearings with a speed of rotation of about 10 rotations per minute by means of an electro-motor. The equipment also comprises spacing discs parallel with the radius of the cylinder, which promote the flow of both water and air in the direction of the cylinder axis, whereby the equipment is able to transmit the oxygen of the air into the water more efficiently. The operation of the oxidizer is based thereon that a large reaction surface is provided between the water and the air.

According to the method of the invention, the manufacture of fish silage pellets proceeds as described in the following.

The feedfish is unloaded directly from a trawler into the container 18, where it together with the guts obtained from the cleaning line 19 and having a very great oil content is ground into a mass. When there is only little fresh feedfish or when it is not available, it can be partly or entirely replaced by other animal tissues and/or fish meal, possibly by adding water simultaneously. Active digestive enzymes are added to the mass, if they are not included in the mass already. With the container 18 is connected a dosing device for the acid mixture, by means of which acid mixture is added to the mass by mixing carefully, the composition of which acid mixture is 19 % by volume sulphuric acid, 22 % by volume formic acid and 59 % by volume water. Mineral acid is not absolutely necessary, though it is desirable to use it considering economical aspects. Consequently, the acid can consist of mixtures of organic acids only or also of only one organic acid. The amount of the acid mixture to be used varies a little depending on the feedfish used. The composition mentioned is suitable for Baltic herring with low oil content and about 30 1 thereof is used for 1000 kilo¬ grams herring, ϋndissociated acids easily penetrate tissues (cell walls) and dissociate after penetration at the highest pH of cell liquids. The sulphuric acid in the acid mixture lowers the pH of the liquids in the silage mass, whereby the formic acid not dissociating in acid environment (ph 1,5-2,5) penetrates to acidate the pieces of the mass.

The acid amounts are correct, if in two hours from acidation the pH of the mass is about 2,5 and further, when the process goes on, in eight hours 3-4, at which level the pH approximately shall stay due to the buffer effect of the formic acid. The digestive enzymes remain unchanged even at very low acidities, but begin to digest waste fish effectively, when the pH in the process has risen over two. In forty-eight hours or at a later stage, the fat or oil needed in the pellet is added to the mass in the form of fish oil or some other oil by mixing well, as well as antioxidant preventing the oils from turning rancid, which antioxidant is BUT (butylhydroxytoiuene)- acid, potassic sorbate or the like. When a low-oil waste fish is used, oil shall be added respectively more. The acidity of the mass is observed during the storage. If the pH rises over 4,1, a little acid is added, because otherwise the bacterial activity gets started. Before the mass is pressed into pellets, partly or entirely ripened whole-wheat meal or corresponding meal as well as the necessary vitamin and mineral mixtures and the binder or the binders are added thereto. The composi¬ tion of the mixture is then 60-70 % by volume silage mass, 25-30 % by volume fodder meal, 3-8% by volume vitamins and minerals (in total) and 1-3 % b.yvolume gelatine and possibly other binders. The humidity of a fish silage pellet manufactured in this way is about 35-40 %, the content of phosphorus about 0,35 % and the silage factor 2,4.

It is evident that the method of the invention can be realized deviating from the above in somewhat different ways within the limits of the claims enclosed. It shall also be mentioned that the method is applicable for producing food for fur animals as well.

Claims

Claims:

1. Method for the manufacture of fish silage pellets, c h a r a c t e r i z e d in that a) feedfish and fish guts are ground into a mass and/or other animal tissues are ground into a mass and/ or a mass is made of fish meal by adding water thereto, b) the mass obtained is mixed with a diluted acid consisting of an organic acid and possibly of a mineral acid, by which acid the pH of the mass is ad¬ justed so that the upper limit is a pH still preventing bacterial acitivty and the lower limit is a pH still permitting the activity of the digestive enzymes of the feedfish and to the mass are added active digestive enzymes in that case that the mass does not include them, c) to the mass is added partly or entirely ripened whole-wheat fodder meal or corresponding meal, d) to the mass are added necessary vitamins and a binder and e) the mass is pressed into pellets after careful mixing.

2. The method according to claim 1, c a r a c¬ t e r i z e d in that fat in the form of fish oil or some other oil or fat is added to the mass by mixing well.

3. The method according to claim 2, c h a r a c ¬ t e r i z ed in that the fat needed is partly obtained as offal from the cleaning line (19) of a floating fish breeding establishment.

4. The method according to any of the preceding claims, c h a r a c t e r i z e d in that the guts mentioned at stage a) are obtained from the cleaning line of a floating fish breeding establishment.

5. The method according to any of the preceding claims, c h a r a c t e r i z e d in that at stage b) as organic acid is used formic acid and as mineral acid sulphuric acid.

6. The method according to claim 5, c h a r a c ¬ t e r i z e d in that the composition of the acid approximately is 19 % by volume sulphuric acid, 22 % by volume formic acid and 59 % by volume water and that about 30 1 of the acid mixture is used per 1000 kilo¬ grams feedfish.

7. The method according to claim 6, c h a r a c ¬ t e r i z e d in that the pH of the mass is adjusted to be between 3-4 in about 8 hours from the acidation.

8. The method according to any of the claims 2-7, c h a r a c t e r i z e d in that in connection with the addition of fat, to the mass is added antioxidant rp prevent the oils from turning rancid, e.g. BHT-acid, potassic sorbate or the like.

9. The method according to any of preceding claims, c h a r a c t e r i z e d in that in connection with stage d) , to the mass are added commonly used vitamin and mineral mixtures.

10. The method according to any of the preceding claims, c h a r a c t e r i z e d in that one binder or the only binder added in connection with stage d) is gelatine.

11. The method according to any of the preceding claims, c h a r a c t e r i z e d in that to the silage mass is added fish blood obtained from the blood shedding basin (17) of the fish breeding establishment.

12. Fish silage pellet manufactured by the method according to any of the preceding claims, c h a r a c - t e r i z e d in that its phosphorus content is about 0,35 %.

13. Equipment for the manufacture of fish silage pellets on a floating fish breeding establishment, which equipment comprises basins for the treatment of raw material as fish, guts and meal, and a machine for the manufacture of pellets, c h a r a c t e r i z e d in that the equipment comprises a storage container (18) for fish silage or its raw materials, which storage container is arranged in the control building ( 1 ) of the fish breeding establishment to float on water, whereby the storage container (18) with its contents does not substantially reduce the carrying capacity of the fish breeding establishment.

14. Equipment according to claim 13, c h a r a c ¬ t e r i z e d in that the storage container (18) is arranged to move vertically within a casing (22), which casing is stationary with respect to the control buil¬ ding (1 ) .