The second line of research is being followed by the Bureau of Plant Industry, assisted by the Bureau of Chemistry, and is concerned with plants other than trees. Private investigations are also being carried on.
The following five requirements are given by the Bureau of Plant Industry, Circular No. 82, as to the availability of crop plants:
1. They must exist in large quantities.
2. They must be available throughout the year.
3. They must yield a relatively high percentage of cellulose.
4. The fiber cells or cellulose, must be of a highly resistant character, and must have length, strength and good felting qualities.
5. And must be of such a nature that the cost of obtaining the fiber will not be prohibitive.
Fibers complying with these conditions will come into commercial use whenever the increasing costs of wood-pulp reach a figure approximately equal to cost of producing cellulose from any other available source. Up to the present time this has not been brought about, but the steady increase in the cost of wood-pulp is approaching a level with which crop pulps may soon compete.
A synopsis of the fibers described in the circular referred to is given below.
Corn Stalks.—On account of the enormous supply, corn stalks were first taken up by the Bureau. The yield of stalks per acre is conservatively estimated at one ton, and the annual product is placed as at least 100,000,000 tons, of which not over one-third is believed to be utilized by the farmers. Three products have been derived from the stalks:
1. Long fiber suitable for paper-making, composing 12 to 18 per cent of the bone-dry weight.
2. Pith pulp, suitable for paper specialties, equal to 15 to 30 per cent bone-dry weight.
3. Corn-stalk extract, obtained by lixivaition, and of value as a cattle food, a ton of stalks yielding 200 to 300 pounds of soluble solids.
It would require an immense area to supply a mill of moderate capacity, and the question of whether the derivatives of corn stalks could be sufficiently valuable to overcome the costs of harvesting and hauling, has never been answered by any experiment on a commercial scale.
Broom Corn.—Broom corn contains a higher percentage of fibers than corn stalks. In laboratory and semi-commercial tests, fiber yields of 32 to 40 per cent have been obtained with a comparatively low consumption of chemicals. The Bureau claims that results “indicate that this material is suitable for immediate use in paper-making on the basis of quality of fiber produced and yield of fiber secured.” It is estimated that 450,000 tons is the approximate annual crop. Food extracts may also be obtained as well as the fiber.