FISH MEAL AND OIL 469 



cylinder is loaded through the port to from Vz to % of capacity with raw fish waste. 



In some plants the port is covered and a vacuum is drawn on the inside cylinder 

 to increase the rate of drying. In others the port is left open and the drying takes 

 place under atmospheric pressure. If the latter method is used, the drying time 

 is increased, with a corresponding increase in cost. 



When the mass of fish has been cooked and dried sufficiently, as determined 

 by the operator, it is discharged through a port at the bottom. This material is 

 then placed in a hydraulic press where the small amount of remaining water and 

 oil is pressed out. The cake of pressed meal is then ground, after which it is ready 

 to be sacked for market. 



Since fish meal prepared by this method contains all the water-soluble com- 

 pounds, it may bring a higher price in the market. However, it also contains a 

 larger per cent of oil which, in some markets, oflFsets the higher value of the meal. 

 The oil produced by this method may be more highly oxidized and in general 

 brings a lower price than oil produced by the wet-reduction process. 



Butler (1949) states that equipment for setting up a dry-rendering plant, de- 

 signed to process shark carcasses which contain no recoverable oil, costs approxi- 

 mately $35,500, plus freight from the manufacturing plant. These costs are cal- 

 culated on the basis of a capacity of 32 tons of raw material per 12-hour day. This 

 estimate includes the installation of four batch driers of the steam-jacketed type, 

 conveyors, motors, grinders, and meal-collecting and sacking equipment. 



It is further estimated that a similar unit, suitable for processing fish waste 

 with a capacity of 1 ton of raw material per hour, consists of the same equipment, 

 except that only one drier is included. The costs in this case are approximately 

 $25,000, plus freight charges. This estimate does not include steam and electric 

 power for operating the equipment. Boilers and fuel would be additional, and 

 would probably cost about $1,200 to $1,800 for the 4-unit operation and about 

 half that amount for the 1-unit plant. The fuel costs would depend upon the 

 type of fuel desired for the plant operation. A supply of water for use in generat- 

 ing steam in the boilers would of course be needed for either of the above opera- 

 tions. Odor-disposal equipment is also required, especially in densely populated 



Wet-Reduction Process 



Fish used in large volume for the production of oil and meal are reduced by 

 the wet process. The three species of fish which are included in this group are the 

 menhaden, pilchard, and sea herring. Menhaden is by far the most important, 

 rated according to volume of catch. It is the only species which is considered un- 

 suitable for human consumption, chiefly because of its excessive oil content. It is 

 also the only species which is sought entirely for its value in the production of meal 

 and oil. 



At one time meal was considered the least valuable product from fish, and was 

 used chiefly as fertilizer. Of late years meal has become recognized as an excep- 

 tional ingredient for animal food, and its value for this purpose exceeds that of 

 oil. In 1948 there were 501,578 tons of menhaden manufactured into 104,058 

 tons of meal, valued at $11,560,914, and 8,763,939 gallons of oil, valued at 

 $10,132,179. Menhaden is found on the Atlantic and Gulf coasts. A breakdown 

 of the production of this industry by states is contained in Table 102 (p. 472). 



