|Infobox on Fishmeal
|Example of Fishmeal
|Stowage factor (in m3/t)
|Humidity / moisture
Fish meal, or fishmeal, is a commercial product made from fish and the bones and offal from processed fish. It is a brown powder or cake obtained by drying the fish or fish trimmings, often after cooking, and then grinding it. If it is a fatty fish it is also pressed to extract most of the fish oil.
The use of fish by-products is not a new idea; it has been used in previous times to feed poultry, pigs and other farmed fish.
Fishmeal can be made from almost any type of seafood but is generally manufactured from wild-caught, small marine fish that contain a high percentage of bones and oil, and is usually deemed not suitable for direct human consumption. The fish caught for fishmeal purposes solely are termed “industrial”. Other sources of fishmeal is from by-catch of other fisheries and by-products of trimmings made during processing (fish waste or offal) of various seafood products destined for direct human consumption. Virtually any fish or shellfish in the sea can be used to make fishmeal, although there may be a few rare unexploited species which would produce a poisonous meal.
Fishmeal is made by either cooking, pressing, drying and grinding of fish or fish waste to which no other matter has been added. It is a solid product from which most of the water is removed and some or all of the oil is removed. Four or five tonnes of fish are needed to manufacture one tonne of dry fishmeal.
There are several ways of making fishmeal from raw fish; the simplest way is to let the fish dry out in the sun. This method is still used in some parts of the world where processing plants are not available, nevertheless the end product is poor in comparison with ones made by modern methods. Nowadays all industrial fish meal is made by the following processes:
Cooking A commercial cooker is a long steam jacketed cylinder through which the fish are moved by a screw conveyor. This is a critical stage in preparing the fishmeal, as incomplete cooking means that the liquor from the fish cannot be pressed out satisfactorily and overcooking makes the material too soft for pressing. No drying occurs in the cooking stage.
Pressing A perforated tube with increasing pressure is used for this process. This stage involves removing some of the oil and water from the material and the solid is known as Press cake. The water content in pressing is reduced from 70% to about 50% and oil is reduced to 4%.
Drying It is important to get this stage of the process right. If the meal is under-dried, moulds or bacteria may grow. If it is over-dried, scorching may occur and this reduces the nutritional value of the meal.
Two main types of dryer: Direct and Indirect
Direct Very hot air at a temperature of 500°C is passed over the material as it is tumbled rapidly in a cylindrical drum. This is the quicker method, but heat damage is much more likely if the process is not carefully controlled.
Indirect Cylinder containing steam heated discs which also tumble the meal.
Grinding This is the last step in processing which involves the breakdown of any lumps or particles of bone are involved in this stage.
Fishmeal is a nutrient-rich and high protein supplement feed ingredient that stores well, and is used primarily in diets for domestic animals and sometimes as a high-quality organic fertilizer.
Shipment / Storage / Risk factors
Fishmeal is used as an ingredient in animal feeding stuffs. Shipped extensively in bulk, though sometimes packed in 4 or 5-ply bags of 50 kilos with a polythene liner between two of the plies. If damaged sufficiently to be unable to be used for animal feed may be useful as a fertiliser.Increase of temperature in cargoes of fish meal is bound to occur, because handling and the movement of the stow caused by weather and sea conditions cause particles of unoxidised fat to become exposed and initiate the oxidation process. If the antioxidant remnant in the immediate vicinity is sufficient, the generation of heat by the oxidisation process will be retarded and no damage will occur. Should there not be sufficient antioxidant in the vicinity, or what there is becomes rapidly consumed, then temperatures will increase to the point of combustion.
That is the process under normal conditions but in general terms the cause of heating can be attributed to one or a combination of the following factors:
1) Inefficient production process
2) Inefficient and/or insufficient application of antioxidant
3) Ineffectiveness of antioxidant due to age or adulteration
4) Inefficient stowage
5) Carriage in vessels with defective cargo ventilation systems
6) Carriage of cargo in bulk carriers that entails excessive high stowage, thereby precluding the dissipation of heat generated in the lower strata.
7) Voyages that entail the cargo being in the vessel in excess of two months.
8) Weather and sea conditions.
Each of the aforementioned factors is divisible into various components that individually play an important role in identifying the cause of excessive heating and/or combustion. Whilst heating might be spread over a wide area of a cargo of fish meal, actual combustion initiates at one or more focal points and radiates out in all directions.Combustion of the fish meal itself rarely develops into naked flame although it can be seen occasionally when packaging ignites. Red hot fish meal cools rapidly when fully exposed. The first consideration when heating is detected is the location of the vessel and weather conditions at the time. A basic rule is never to apply water for the following reasons:
a) There is sufficient oxygen in water to initiate the oxidation process of hitherto unexposed molecules of fat.
b) Wet fish meal is a great medium for attracting flies. Maggots propagate at great speed, that is only surpassed by the strength of the stench of decomposition.
The only way to contain combustion of fish meal is to locate the centre of heat and physically remove it together with the cargo in the near vicinity. This action involves removal of hatch covers and excavation into the cargo as quickly as possible. The only other remedy is to close down ventilation and adopt all measures necessary to ensure that the cargo space is sealed as best possible and apply CO2 to bring the oxygen content of the space below to 2%. Smoke tracings give an indication of the combustion zone although the centre of combustion might not be located directly below that point.
When heating has affected a large percentage of the cargo, examination involves the separation of bags according to the colour of the meal unless it is seriously toasted to a dark golden brown colour or completely destroyed. Meal may be heat hardened or pressure compacted. Heat hardened meal is simple to detect because of its very dark colour and breaking resistance. Compacted meal is easily reduced to powder by hand pressure. Meal that has become lumpy but maintaining its colour is generally attributable to excessive moisture that has in turn produced problems such as mould etc. Once all the fish meal that has been affected by heating is segregated, samples should be drawn. It is advisable where possible for similar samples to be drawn for all interested parties. Initially the laboratory should be instructed to analyse for the normal elements on the basis of which fish meal is commercialised as follows:
Protein oil, moisture, salt and sand, ash.
In general terms, sand does not appear in fishmeal from the Northern Hemisphere but could be present in fishmeal from the Southern Hemisphere. If the content of oil and moisture is higher than certain limits it can become heated. The chance of heating is lessened where moisture content is between 6% and 12% and fat content does not exceed 11%, or 15% for fish meal containing an antioxidant. Fish meal containing more than these percentages of moisture and fat should be allowed more time in the drying out period before shipment. Meal should be allowed to mature at least 21 days before shipment, but not more than six months. Temperature of the meal at the time of loading should not exceed 37,5°C. For more details reference should be made to current IMDG Code, class 4.2 for non-antioxidant stabilised meal and class 9 for antioxidant treated meal.
Heating can cause severe caking and discolouration.
In bulk from European and Scandinavian countries fish meal travels well without antioxidant. If shipped in bulk from South America, Africa or Asian countries, there is little risk if antioxidant is added, but if stowed in a deep hold with poor ventilation without antioxidant, can be affected by self-oxidation. If shipped in bags stowage is normally carried out by laying bags fore and aft in rows of two athwartship, so that the mouths meet in the centre of the rows, leaving a ventilation channel; of at least 20 cm between each row. The ventilation channels to be kept open by dunnage. In some South American and Asian areas fish meal is stored in the open where it is possible for moisture to be absorbed from the atmosphere bringing it above its normal level. Water damage, if heavy, can affect release of free ammonia as can heavy heating, pressure or poor ventilation. With the number of different species now being utilised, colour can vary from light brown to very dark, or for white fish variety from whitish to greyish white. Grinding can be fine to coarse. Fish meal in torn or burst bags, due to water damage, etc., can be extensive to rebag. A certain amount of dusty material can be regarded as ‘dirty cargo’ in some ports. All shipments of fish meal are accompanied by a pre-shipment certificate that must show production dates and details of fat, moisture, antioxidant content and temperature at time of loading. These documents should be sighted to establish the suitability of the cargo for shipment.
Fishmeal or fishscrap is usually offered for shipment in a STABILISED form but the UNSTABILISED form may also be offered. Moisture, fat and stabilizer contents (which determine IMO class), UN No., packing, stowage and segregation - may vary from one manufacturer to another.
IMO requires that the temperature of cargo in each hold is monitored throughout the voyage. This can only be satisfactorily performed by the installation of remote reading sensors which are normally connected to a switch box which also has a connection for a read-out meter. It is common to install sensors at two or three levels in a lower hold and one or two levels in a tweendeck depending on the depth of the relevant spaces. Between four and eight sensors are distributed at each level depending on the cross sectional area of the cargo spaces. From experience it is known that there can be some increase in temperature (possibly up to 3-4°C) as recorded from some sensors, at the outset of a voyage after which the temperature stabilizes. This situation need not give rise to concern. If, however, the temperature of one or more sensors exceeds 40°C and continues to rise, the Master should take timely steps to seal the relevant hatch covers using sealing tape and if necessary plastic sealing or cement. Considerations should be given at this stage to sealing ventilation openings: owners and charterers should be informed of the temperature figures and their advice or instructions sought. In any event, the instructions in the IMO entry ‘Observations’ should be followed i.e. if any temperature sensors indicate a cargo temperature in excess of 55°C, the cargo space and any interconnecting cargo space should be sealed effectively and CO2 should be injected as stipulated in the Fire Fighting Manual provided by the installers of the CO2 system. The injection should take place slowly over a 24-hour period. It is basically undesirable to inject less CO2 than is recommended in the manual even though this means that only a few cargo spaces can be so treated.
It should be appreciated that any cargo heating results from an oxidation process. This means that the oxygen concentration in a hold is depleted and the concentration of nitrogen (an inert gas) increases. Hence in a sealed hold cargo heating tends to be self-quenching. It is therefore of paramount importance that the Master has all necessary materials on board to allow very efficient sealing of cargo spaces in order to minimize atmospheric interchange. Very efficient sealing may be a time-consuming operation but should never be skimped. Technically, provided that hold sealing is adequate, it would be possible for a ship with cargo heating in all her holds, to sail safely across the Pacific Ocean with her CO2 supply exhausted (assuming a sufficient reserve for the engine room). However, such action would only be recommended if sealing efficiency could be guaranteed. Under normal circumstances where there is obvious progressive heating, a ship would be recommended to go to a port of refuge to obtain adequate CO2 supplies. This often involves fitting a bulk tank containing several tones of CO2. If considered necessary, further sealing should be performed whilst the ship remains in port. Unless special circumstances prevail, sealed hatch covers should not be opened until the first discharge port for that hold is reached. An accurate assessment of the situation in any cargo space can be obtained by measuring the oxygen concentration via a pipe connected to an oxygen meter which is introduced by slightly opening an access manhole. The manhole should be closed and secured immediately measurements have been made. The oxygen meter should be tested immediately before use by checking the oxygen level of the external atmosphere (20,9%). When oxygen levels (of the cargo hold) are below 10% heating is greatly restricted. Even without use of CO2, this situation may be achieved in a few days when hatches are effectively sealed and there is a substantial quantity of cargo heating in a hold.
Heating cargoes (if any) should be discharged first. However, where this is not practicable the rate of spread of heating in a cargo space can drastically be reduced by maintaining a low oxygen concentration. This is done for preference by the use of CO2 or when supplies are not available by keeping the holds sealed. It must be appreciated, however, that once the holds are opened for discharge and the oxygen concentration is allowed to rise to at least 20% which is necessary for safe working in the hold, heating will resume at an accelerating rate. Hence attempts should be made to discharge pockets of heating cargo as soon as possible. One some occasions this can be achieved without difficulty. However, sometimes smoke generation becomes excessive, preventing manual operations. There are then several options for dealing with this problem and the choice depends on the circumstances prevailing.
The first option is to reseal the hold and inject CO2, the minimum quantity injected being that recommended by the installers of the ship’s CO2 system. Again this operation should take place over a 24-hour period. The hold should then be left sealed for at least four days. The oxygen concentration must again be allowed to rise to 20% before labour is allowed into the space to resume discharge. This option, when successful, results in the minimum amount of cargo damage but extends the discharging period. It may be considered impractical if it has to be repeated several times.
The second option is to control smoke evolution by the use of water sprayed through a fine spray directly onto the smoking cargo, whilst discharge proceeds. This procedure, if properly used, results in limited water damage to part of the cargo. However, excessive water is often applied, particularly when the local fire service intervenes, and the amount of cargo wetted can be substantial.
Very occasionally the cargo will actually ignite. Flames should be extinguished with a water spray.
The third and last option which should only be used when other methods have failed is to use a water spray to control smoke evolution or fire and discharge heating pockets by grab. The procedure obviously results in more cargo damage.
Flammable materials should not be stored in store-rooms adjacent to or above holds loaded with fishmeal.
Damage and apparently sound cargo should always be separated at the time of discharge. However, even badly heated cargo has feed value and cane be incorporated in cattle feed. Hence, cargo should never be left on board to be dumped at sea.
Non anti-oxidant treated fishmeal is classified as spontaneously combustible (class 4.2 – UN No. 1374 as amended 20-82), whereas anti-oxidant treated fishmeal is classified as a miscellaneous dangerous substance (class 9 – UN No. 2216 as amended 24-86). The IMDG Code stipulates that the moisture content of both types (of classes) of fishmeal is to range between 5% and 12%, whilst the fat content of non anti-oxidant treated fishmeal may not exceed 12% and that of anti-oxidant treated fishmeal may not exceed 15%, by weight. Thus, in as far as moisture content is concerned, there is no difference between the two types of fish meal and in this context it should be noted that there have hardly ever been cases where heating was initiated by a too high moisture content of the fishmeal.
The IMDG Code distinguishes between the aforementioned two types of fishmeal on a number of other important points and these are that non anti-oxidant treated fishmeal should have been weathered for not less than 28 days before shipment, whereas no weathering (or curing), prior to shipment, is required for anti-oxidant treated fishmeal; furthermore, non anti-oxidant treated fishmeal requires a special method of stowage and ventilation, whereas anti-oxidant treated fishmeal does not and may even be shipped in bulk, thus forming a dense mass, filling a ship’s hold entirely. The purpose of weathering before shipment, of non anti-oxidant treated fishmeal, is to allow oxidation of unsaturated fatty acids, naturally present in the fat, remaining in the fishmeal after production, to occur. One of the by-products of oxidation is heat, which is to be removed at a faster rate than at which it is produced. This is in order to prevent the fishmeal from increasing in temperature, which is undesirable, as the rate of oxidation increases with temperature, so that a situation may ariser where the rate of oxidative heat production is such that it cannot be removed fast enough; eventually, such fishmeal may reach a temperature at which spontaneous combustion will occur.
Fishmeal carried in containers
The substance is usually offered for shipment in large quantities and compliance with provision "(e)" under observations on page 9030 of the IMDG Books could be impracticable. There are no objections to the carriage of class 9 fishmeal or fish scrap in closed cargo transport units under deck without taking and recording temperature readings 3 times a day provided:
- The units are packed to their maximum volume (the less air present, the less the risk of spontaneous combustion).
- The doors of the containers must be sealed with self-adhesive tape (to minimize possible air ingress).
- The containers must be stowed in an accessible position and not less than 6 meters from any source of heat.
- Daily routine inspections must be carried out.
- All other provisions listed on page 9030 of the IMDG Books are met.
- Packaging is mainly in black plastic bags.
- Sensitive to spontaneous combustion.
- Recommended container type is a 20 ft GP container.
Container to be stowed as full as possible, leaving the least dead space (meaning less oxygen/cause to spontaneous combustion). Attention should be given to the max. pay load of the container. Local authorities may require the container doors to be tape sealed.No dunnage to be used. Fishmeal can also be carried in bulk mode inside GP containers. A plastic inner liner bag must be fitted to the container prior to loading. Refer to Cargo Research Desk for details.
Particulars: A certificate is required, issued by a competent authority, mentioning the humidity percentage, whether or not anti-oxidation treated, curing-and non-curing period. Unmodified fish meal can spontaneously combust. In the past ships have sunk because of such fires. These days the danger is eliminated by adding antioxidants to fishmeal prior to storage or transportation.