Corncobs Enter Industry

ABOUT 200,000 tons of corncobs were put to interesting and profitable industrial uses during the war. They performed an essential service so well that increasing quantities are destined no doubt to serve more extensively in the days of peace. Other industries have made a market for this agricultural commodity whose previous utility was limited largely to corncob pipes, starting the kitchen fire, and stopping up the hayfield water jug.

Of the tonnage of cobs used industrially during the war, more than half went into the production of furfural, a chemical essential to the new synthetic rubber industry. Many thousands of tons were used in manufacturing ordnance. But perhaps the most interesting new use was one developed by the Northern Regional Research Laboratory at Peoria, 111, in cooperation with the Navy, a method for cleaning carbon and oil deposits from airplane engines with ground corncobs in an air blast. To supply these industrial needs about 50 grinding plants were established to produce cob products; only one existed before the war.

An expanding industrial utilization of corncobs, however, depends on the processor’s ability to obtain them in large quantity without paying too much for collecting and transporting them. Several industrial attempts to use them have failed because those conditions could not be met. Yet the supply of cobs is plentiful and fairly well concentrated. A survey we made in 1943 showed that 16 million tons of cobs are produced yearly; 3 million tons of them came from corn sold off the farm. Illinois and Iowa account for three-fifths of that amount; Minnesota, Nebraska, Indiana, Ohio, and Missouri also produce large quantities.

Cobs that accumulate at country mills or elevators or at hybrid-seed plants are the easiest and cheapest source, particularly if operators grind the cobs. We found more than 100,000 tons of cobs collecting at elevators each year within a radius of about 80 miles of one point in Illinois, and 42,000 tons in an Indiana area 150 miles long and 40 miles wide. Cobs were a nuisance at the plants, and some large elevators built special incinerators to get rid of the cobs. During the war, some operators increased the concentration of cobs at their elevators by paying a slight premium for ear corn. It has been practical also to collect cobs from farms.

The secret of finding industrial uses for farm wastes lies in capitalizing the unusual or unique properties of each. Cobs have one such property that is outstanding.

A cob is composed of four rather distinct parts: Light chaff; coarse chaff in the form of tough, wood-like flakes; pith; and a woody ring.  The ring and the coarse chaff are tough, woody, and resistant to abrasion and granulation. That is their industrially important property. The two parts constitute 94 percent of the entire cob—in processing, therefore, the yield of salable product is high.

The early impetus to the introduction of cobs to industry came from the need by the naval air forces for a method to supersede the use of solvents and hand tools in cleaning carbon and oil deposits from cylinders and pistons when giving airplane engines their usual overhaul after 800 hours of flying. The solution, it appeared, would be found in soft-grit blasting. Work on the problem led to the discovery that corn grits, a form of hominy, if used in a sand-blasting machine under about 90 pounds pressure, did a safer, faster, and less expensive job. But the Navy’s plan to use 100,000 bushels of grits a year had one serious drawback— there could be no salvage of the grits for food or the production of alcohol because of the poisonous lead in the cylinder deposits. Thus, in an effort to save this food and improve the process, this laboratory, working with the Norfolk Naval Air Base, developed the use of a mixture of 60 percent ground corncobs and 40 percent unground rice hulls.

lasted about 10 times longer than corn grits. Costs were lowered more than 80 percent. The Navy has standardized on those materials, and its specifications call for corncobs ground to pass a 10-mesh screen and to be retained on a 32-mesh screen. Chaff and fine particles must be absent and not more than 13 percent moisture may be present.

Using this process, the Navy found that the cleaning operations were practically foolproof. The hard carbon, oil, and scale were rapidly and completely removed. The cob particles were nonabrasive on the metal, hence no change in the close dimensions of parts occurred. Dirt does not collect on the particles; the particles can be used repeatedly until they finally become powder and are blown out of the blasting booth.

The soft-grit blasting method is being rapidly put into industrial use.  For example, one of the major automobile companies is using the method in several of its plants where engines and parts are rebuilt or repaired. A manufacturer of farm equipment has installed it to clean aluminum-foundry core boxes. A logging company is using it for maintenance of tractors and other logging equipment. Several glass companies use it for cleaning molds.

Almost any kind of deposit may be removed from metals by it, except hard mill scales Automobile paints and lacquers are easily removed. In all cases a smooth, clean, dry surface results. The method can have wide use in garages. It can be used to clean farm machinery. Moreover, numerous tests and demonstrations, made in cooperation with a number of different industries, show there are many purposes for which sand and possibly shot are now used as cleaning agents where soft-grit blasting would do as good a job with greater safety. There are many other jobs for which sand or shot cannot be used, but for which soft-grit is ideal.

Ground corncobs were used to some extent before the war for burnishing metal parts by tumbling in a barrel. The manufacture of ordnance for the Army and Navy greatly increased such use, particularly for burnishing cartridge cases. Specifications by one arms manufacturer called for ground cobs passing a 10-mesh and being retained on a 48-mesh screen.

This laboratory has shown that any of the corncob fractions ground to pass a 100-mesh screen can replace wood flour in the manufacture of certain of the lower-cost phenol-formaldehyde plastics. White cobs are preferred to red. The outlet for cobs in this market, however, is restricted. Freight rates on cobs from the Corn Belt to the eastern seaboard are higher than the rates manufacturers pay on wood flour from Maine and New York. When and if these plastic molding powders are manufactured in the Central States, this use will represent a potential market for corncob fractions.

An increasing market is developing for coarsely ground cobs for use as chicken litter, especially in laying houses. When prepared for this purpose, the cobs are coarsely ground and the fine particles screened out.  Trials show that material passing a 2-mesh screen and retained on a 4-mesh screen is considered acceptable, although some poultrymen prefer particles up to I inch long. For litter use, cobs have the advantage of being clean and absorbent. There is also the possibility that with the addition of chemicals an ideal litter may be produced.

A number of uses for corncobs which, strictly speaking, are not new uses should be mentioned. A chief use is for pipes. One company in Missouri is said to have produced 30 million pipes in 1940. The industry depends, however, on a special variety of corn that requires exceptionally fertile soil for development of cobs of suitable size.

During the war, cob particles about the size of sawdust were used for packaging metal parts for shipment. The cob particles kept the parts dry and prevented a certain amount of corrosion.

Finely ground cobs are in use in floor-cleaning and sweeping compounds. Cob particles that pass a 20-mesh screen have been used a number of years in cleaning furs.

Furfural is an amber-colored liquid. It has been manufactured for more than 20 years at a plant in Cedar Rapids, Iowa, by treating oat hulls with dilute sulfuric acid and steam. The residue from this treatment is used as fuel or sold as fertilizer filler. Important uses for furfural have been found in making plastics, refining wood rosin, making lubricating oils from petroleum, and in producing other important chemicals derived from it. When it was found that furfural was one of the best chemicals for purifying butadiene used in making synthetic rubber, the production requirements were so great that the Government built a plant at Memphis, Tenn., that produces 12,000 tons of furfural a year and uses 100,000 tons of cottonseed hulls or corncobs as raw material.

The prospects are bright for an expanding market for furfural. Many large chemical companies here and in other countries have carried on extensive research to find new uses for it. We, too, have been actively engaged in such research since the founding of the Regional Laboratories. It is now known that many new and important uses are possible. For example, fibers like nylon can be made from chemicals prepared from furfural.

More than 100 years ago chemists learned that when starch or cellulose was treated with sulfuric acid under right conditions glucose, also known as corn sugar, resulted. The sugar, glucose, is the raw material used in the fermentation process for making alcohol. In the present process for making furfural the cellulose of the hulls and cobs is destroyed and appears in the residue. We believed that if the right conditions could be found, it should be possible to produce furfural from corncobs and at the same time. The smaller amount of residue resulting should be just as valuable as the present furfural residue.

Our research confirmed this idea, with the result that this laboratory has been able to develop a process that gives promise of producing both furfural and glucose at lower costs than was possible before. We are now studying this process in a semicommercial plant at the Northern Laboratory, built under a special appropriation by Congress for the production of synthetic liquid fuels from nonpetroleum sources. If our expectations can be realized, a greatly expanded market not only for corncobs but also for other agricultural residues such as peanut shells, rice hulls, cottonseed hulls, flax shives, and the like will exist.

Although thousands of bushels of ear corn are ground whole and fed to cattle with good success, ground cobs have not been considered desirable for addition to mixed feeds. Indeed, many States prohibit such use in commercially prepared feeds. During the time of feed shortage, however, cobs ground to pass a one-eighth screen were moving in carload quantities into this market. Cobs may have some value, also, in feeds of high molasses content, but they contain very little protein and their vitamin content is very low.

Corncob processing will be found to be just like any other business— markets must be established, and sales and managerial ability will be even more important than ability to process the product. Careful investigation should be completed before investments in processing plants are made. Cob prices, it should be realized, can never be high but a small return to the farm per ton will result in a good percentage return on net farm income. A market should be found for all fractions resulting in cob grinding. Furfural plants can use any of the fractions, coarse or fine. With the start made, and with intelligent effort, there should be an industrial market for cobs and hulls, whether we consider the raw material either in its physical or its chemical composition.