28 BULLETIN" 150, U. S. DEPARTMENT OF AGKICULTUEE. 



FISH SCRAP FROM SALMON WASTE. 



From preceding paragraphs it is to be seen that during the last 

 year a total of 1,630 tons of dried fish scrap and 286.000 gallons of 

 oil were manufactured from the waste from salmon canneries on the 

 Pacific coast of the United States. The amount of these products 

 represents the output of five plants. 



The methods employed in at least four of the five plants in all 

 essentials are similar. The differences between them are chiefly in 

 mechanical features and in the arrangement of the machinery within 

 the plants. The same process is used in all of them. This consists 

 in cooking the waste by steam, either in closed retorts under pressure 

 or in open retorts, in pressing the cooked fish in one type of press 

 to remove the water and oil, and drying the scrap. In the following 

 paragraphs the methods in vogue in these rendering stations are 

 described in some detail. 



COLLECTING. 



The waste is carried from the cannery to the rendering plant on 

 scows. In cases where the floor of the cannery is high enough above 

 the surface of the water the refuse from the various " butchering " 

 operations can be run through chutes into the scows by gravity. 

 There are instances, however, where this is not possible at high water, 

 and it has been found necessary to install conveyors for loading the 

 scows. These are arranged beneath the cannery floor. The material is 

 delivered to them at the bottom of hopper-shaped receptacles which 

 receive the waste from the cannery floor. Where the top of the 

 scow at high tide is above the level of the cannery floor, two con- 

 veyors working together at an angle to each other are utilized, one 

 bringing the material horizontally to the edge of the dock to which 

 the scow is made fast and the other lifting it over the side of the 

 scow. The conveyors may be operated by a small gasoline engine 

 or by the same motive power that operates the mechanical cleaner 

 or the cutter. 



UNLOADING. 



The charged scow is towed to the dock of the rendering plant, 

 where it is unloaded mechanically. An adjustable bucket conveyor, 

 of the wheat-elevator type, is rigged in such a manner that its free 

 end can be thrust into the mass of material constituting the load of 

 the scow. The load is thus lifted and deposited directly, or by means 

 of an auxiliary conveyor, into storage bins. From these it is drawn 

 off as desired into cooking vats. What is regarded as the best prac- 

 tice consists in raising the waste directly to bins situated over the 

 cooking vats, which in turn are placed over the presses, so that only 

 one lifting is necessary, and the material thereafter may pursue its 

 course through the factory by gravity. 



