160
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 22, No. 2
Commercial Possibilities of the Common Milkweed’ . As Indicated by Its Yield and Composition Fisk Gerhardt IOWAAGRICULTURAL EXPERIMENT STATION, AMW, IOWA
The milkweed plant has been propagated for the first time in sufficient quantities to determine the yield and composition of its various plant parts. Experimental data are presented which indicate a production of 30 bushels of seed, 280 pounds of floss, and 1 ton of air-dry stems per acre. The ratio in yield of pod to seed is approximately 12 to 1, while that of seed to fiber is 2 to 1. The seeds possess large amounts of nitrogen, oil, and phosphorus. New data are presented relative to their composition: 21 per cent of the seed is composed of a semi-drying oil, while 47 per cent of the remaining meal is crude protein. Certain physical and chemical properties of the floss indicate its similarity to kapok. A comparison of its composition with that of several well-known fibers is
vv
ITH the pronounced increase in the consumption of cellulose as it is constantly entering into new and unexpected fields, it becomes obvious that our future supply will of necessity originate from annual plants rather than from those species requiring years to attain sufficient maturity. Further, certain fibers such as kapok and possibly milkweed possess a low absorption coefficient and a high degree of buoyancy ( 3 ) . Some of these fibers enjoy a specific commercial adaptation in the production of lifesaving (I), playground, and insulating equipment. I n the development of our future sources of fiber, the byproduct return in the form of oils, gums, resins, and protein concentrates will continue to be a factor of prime importance. The commercial demand for these commodities is gradually approaching in magnitude that of our cellulose industries. Among the primary problems, then, now confronting the chemist and plant breeder are those concerned with further exploitation of our present cellulose wastes and the develop ment of our most promising sources of fibrous materials. The milkweed, Asclepias syriacu, like the Jerusalem artichoke, Heliunthus tuberosus (1G),and possibly the sunflower] H . unnus, belongs to that group of plants possessing some potential economic value. Although the milkweed is generously distributed throughout the United States and southern Canada (d), it has received only a limited amount of scientific attention. The seed fibers of A . syriaca have been called the “cotton of the North’’ (9), but attempts to use them as textile material have met with little success (11). Dischendofer (5) has shown them to remain straight] quite brittle, and high in lignin and ash. Saunders (14) was the first to report the presence of rubber in the latex of the milkweed. The possibility of this plant being a new source of rubber was negated through the efforts of Fox (6). Neish (12) has indicated that certain by-products of the seed, such as protein and oil, offer some commercial significance. However, the literature discloses no detailed effort to investigate the properties, composition, and possible utilization of various portions of the cultivated milkweed. The plant parts which lend themselves to possible commercial adaptation are the seed, with its buoyant cellulosic fibers and high content of protein and 1 Received November 11,1929. Publication approved by the Director of the Iowa Agricultural Experiment Station.
included. Commercial application indicates that where fiber brittleness is not the determining factor, milkweed floss may be used especially in life-saving, insulating, and playground equipment. New data are presented for the tensile strength of the bast fibers, which approximate 10 per cent of the weight of the stem. Like flax, their application should be found in the textile industry. The stem tissue contains 36.5 per cent alpha-cellulose and compares favorably with many softwoods in this respect, while its hydration capacity, fiber length, and strength are favorable to the production of a paper pulp of merit.
.... ..
oil, and the stem, with its long bast fibers and woody parenchyma tissue. I n a previous paper (7) attention was directed toward certain physiological and translocatory changes which occur within the milkweed. These studies, together with the presence of an abundant source of cultivated material, suggested the advisability of continuing a rather intensive investigation upon the yield, composition, and properties of a number of products as they are found in this plant. Source of Material
I n the course of certain physiological studies upon the milkweed (7) it became necessary to propagate the plant on an experimental plot. Such an area, comprising approximately l/20 acre, was established from native seed during the spring of 1926. Owing to perennial characteristics the plant failed to mature by the close of the summer period. The material used in the present investigation was obtained from mature plants grown on the experimental plot during the following summer. Harvest and Yield
Harvest the first year occurred early in October. This was greatly facilitated by collection of the fruit prior to the rupturing of the pods. The stems remaining on the plot were cut, tied into bundles, and shocked (Figure I), and subsequently removed and stored for future use. Seed and fiber separation the first year was accomplished with an ordinary cotton gin. Considerable difficulty was experienced in this procedure] which was due chiefly to brittleness and lack of adherence of the seed fibers. It became necessary to remove the husks and to modify the saw guides prior to ginning. Seed separation the second year was accomplished by hand. The removal of the husk followed by a simple rolling between the palms resulted in a complete separation of seed and fiber, and, although somewhat cumbersome, produced less injury to the fibers. No doubt the Bley machine (IS) as used in the kapok industry would become directly applicable here. The yield of the various plant parts is shown in Table I. The maximum calculated yield is based upon the assumption of one normal plant of 10 pods per square foot per acre, with the seeds weighing 10 grams and the floss 5 grams per plant.
?'he data in Tablo I slmv
G Z5 per cent yield tho fimt y o u follosrd by R 62 per ,:nit iiicrrnse for tho acconrl y c i i ~ . Tlx r h o in yield of pod 10 seed is nppioximntely 12 to 1, whik that
