FIG. 91.—A source of nitrogen from shellfish waste Shellfish Wastes
FERTILIZER Nitrogen From Organic By-Products Valuable
Do you belong to the once numerous group of farmers who judged the potency and value of a commercial fertilizer by the robustness of its odor? If so, some of the materials that the department has recently pointed out as possible sources of organic fertilizer nitrogen, or ammonia, may not appeal to you, strongly.
There are by-products of the manufacture of cocoa and chocolate, for example, that carry the pleasing fragrance of a freshly opened can of breakfast cocoa, which have been produced in such quantities and held so cheaply that the Bureau of Soils has looked into the possibility of utilizing them for fertilizer purposes.
It was found that upwards of 20,000 tons of by-product cocoa cake is produced annually in the United States. This presscake is the residue from the manufacture of cocoa butter, of which enormous quantities are consumed in the confectionery industry. Like breakfast cocoa, much of the by-product cake results from the pressing of roasted and shelled cacao beans, but the cake is lower-grade material and usually contains less of the fat than beverage cocoa powders.
Viewed as fertilizer material, the by-product cocoa cake (or when ground, “cocoa meal”) is somewhat like castor pomace in chemical composition. The cocoa, however, contains about 4 per cent of nitrogen (equal to 4.9 per cent of ammonia), whereas castor pomace will usually contain as much as 5 per cent of nitrogen, or about 6 per cent of ammonia.
Other by-products of the cocoa industry are the shells, known to the trade, after grinding, as “cocoa shell meal” and extracted presscake, or defatted cocoa. The shells are produced wherever cacao beans are roasted for the manufacture of cocoa and chocolate. Production of the extracted or defatted cocoa, on the other hand, has been confined to a single locality.
Analyses show that the shells contain from 2.5 to 3 per cent of nitrogen (3 to 3.6 per cent of ammonia); and the dried defatted cocoa, about 4.4 per cent of nitrogen, or 5.3 per cent of ammonia. Cocoa by-products contain small quantities of phosphoric acid and upward of 2 per cent of potash. When applied to the soil, the cocoa by-products, like cottonseed meal and castor pomace, supply organic matter as well as fertilizing elements.
Fertilizer materials like these, known to the trade as “organic ammoniates,” command comparatively high prices, as a rule. In view of this fact, the cocoa by-products seem to offer possibilities as economical sources of organic nitrogen, particularly in the vicinity of the centers of cocoa and chocolate manufacture—as New York, Philadelphia, and Boston, in the East, and San Francisco and Los Angeles, on the Pacific coast.
There are other trade residues that have attracted attention and which more nearly satisfy the one-time requirements, namely, that a fertilizer should possess “an ancient fishlike smell.” The refuse materials from the packing of crabs and shrimps, for example, are richer in plant-food elements, after drying, than the cocoa by- products.
Dried crab waste is a refuse from the crab-meat industry along the lower shores of Chesapeake Bay. A representative sample, after drying, was found to contain 52 per cent of nitrogen (6.3 per cent of ammonia) and quantities of phosphoric acid and lime equivalent to 7.4 per cent of bone phosphate, and over 30 per cent of carbonate of lime.
Shrimp waste and shrimp bran are by-products of different branches of the shrimp-packing industry located along the South Atlantic and Gulf coasts. The so-called “waste" is the refuse of the canneries and is artificially dried. It contains about 8 per cent of nitrogen (9.7 per cent of ammonia), 10 per cent of bone phosphate, and 9 per cent of carbonate of lime. Shrimp bran consists of the air-dried heads and shell refuse separated from the meats, after the entire shellfish has been cooked in brine and then sun-dried.
As a result of the brine treatment, the bran may contain as much as 9 per cent of common salt, a substance not generally welcome in fertilizer materials. Less than 2 per cent of salt is normally present in the dried crab and shrimp wastes. The bran contains nearly 7.5 per cent of nitrogen, or about 9 per cent of ammonia, 8 per cent of bone-phosphate, and 7 per cent of carbonate of lime.
Such shellfish residues should prove valuable as organic-ammoniate fertilizers. With careful watchfulness of the salt content, they should also prove useful in the feeding of pigs or other livestock. And, in the districts in which they are produced, their use ought to be economically advantageous.
New trade wastes of similar character appear from time to time as the result of industrial developments. It is the aim of the Department of Agriculture to aid in all practicable ways in the conservation and utilization of waste products which give promise of agricultural usefulness.