TANKAGE. A name applied to a product, used mainly for fertilizing purposes, which is prepared from the residue resulting from the treatment of abattoir and slaughter-house re fuse with steam and hot water in closed tanks for the removal of fat, a process commonly known as 'tanking'. Tankage is variable in composition, depending upon the materials used in its preparation and the process of manufac ture, but is generally rich in nitrogen, and it is this element which mainly determines its value as a fertilizer. According to Voorhees, two dis tinct kinds of tankage are ordinarily prepared: (1) concentrated tankage, containing from 10 to 12 per cent. of nitrogen with very small per centages of phosphoric acid; and (2) crushed tankage, of which there are several grades, con taining from 4 to 9 per cent. of nitrogen, and 3 to 12 per cent. of phosphoric acid. Products containing more than 12 per cent. of phosphoric acid are known as bone tankage, and are properly classed with bone fertilizers (q.v.). The term
tankage is also sometimes applied to the product obtained by drying, and in some cases partially charring, city garbage. This garbage tankage is more variable in composition and less valuable as a fertilizer than true tankage, although, like the latter, its value as a fertilizer depends mainly upon its nitrogen. The nitrogen of meat and hone tankage of good quality has been found to be about 60 per cent. as effective as plant food as that of nitrate of soda. which is taken as the standard. Tankage is therefore one of the most valuable sources of organic nitrogen for fer tilizing purposes. Tankage is also beginning to be used with very promising results as a con centrated feeding stuff, especially for feeding hogs. When used in combination with corn it sup plies the deficiencies, from a feeding standpoint, of that grain in protein and ash constituents and thus furnishes a better'balanced ration.