by Shelby Thames, Distinguished How Crops University Research Professor and Can Provide Raw Professor of Polymer Science, University of Southern Mississippi, Materials for the Hattiesburg; Robert Kleiman, National Center for Agricultural Utilization Research, ARS, USDA, Peoría, ÎL; and Cliemical L. Davis Clements, Director, Industry Agricultural Materials, CSRS, USDA, Washington, DC

Nature has produced an estimated specific commodities (corn, soybeans, 300,000 different plant species, of cotton, etc.) in relation to the tradi- which we use only a few hundred in tional food, feed, and fiber markets. organized agriculture. In 1957, USDA To fully explore potential uses of a initiated a program that collected crop, we must view it not simply as a plants worldwide from a number of commodity but as a complex raw ma- sources. The idea was to take a close terial that has specific functional look at these plants chemically and see groups suitable for producing indus- if any new and different materials in trial products. The utility of a given them could be useful to humanity. crop as a resource for the chemical in- About 8,000 different species were dustry depends upon the chemical collected, most of which had never composition and structure of the mate- been examined before. Their chemical rials found in that crop. compositions were analyzed for poten- All crops are made up of many tial sources of starch, protein, oil, fi- types of materials. For example, the ber, gum, and medicinal components, com plant has starches, oil, zein (pro- as well as for any special individual tein), and a number of lesser compo- characteristics. For example, research- nents in each kernel. The cobs and ers found over 100 different, never-be- stalks contain (a long chain, fore-discovered oils. or polymer, of sugar molecules con- This effort to utilize new species, taining six carbon atoms), hemicellu- as well as to develop new uses for tra- lose (a polymer of sugar molecules ditional crops, is possible because na- containing five carbons), and (a ture offers renewable, reliable ''living polymer made up of six-member car- factories" for an incredible array of bon-hydrogen rings). Bach of these chemical materials. materials contains chemically distinct Agriculture in the United States is structural units that can react with accustomed to identifying crops as other chemical structures to form new

86 Part III. Products From Nontraditionai Crops materials. These reactive chemical fruits or seeds. Seed oils have been units are referred to as the "chemical used for millenia as an energy compo- functionality" of the material. nent of food—and almost as long in Its specific chemical functionality nonfood applications. The ancient is the basis for each material's use as Egyptians used castor oil in their an industrial resource. For this reason, paints and as a lubricant, and Biblical when we consider industrial uses for passages refer to olive oil as a source both traditional and nontraditional ag- of fuel in lamps. ricultural products, we group crop re- Seed oils from traditional crops sources in terms of their primary ma- such as soybeans, com, cotton, coco- terials: starches, oils, proteins, nuts, and flax provide raw materials lignocellulosics, and other natural for many of the products that we use products such as naturally derived every day. From the soap we wash chemicals. We will examine in more with, to the grease we use to lubricate detail the functionalities and uses for our automobiles, combines, and mili- three of these materials: oils, starches, tary equipment, vegetable oils are a and lignocellulosics. prime ingredient. In addition, a num- ber of new crops, such as crambe, Vegetable Oils rapeseed, lesquerella, and others, pro- A major ingredient in many plants is duce oils with unique compositions. the oil that can be extracted from their The oil from these new crops is used

Seed oils from traditional crops, such as USDA067-10-2A soybeans, provide raw materials for many of the products that we use every day— from the soap we wash with, to the grease we use to lubricate our automobiles.

New Crops, New Uses, New Markets 87 New crops, such as lesquerella, produce materials for products from lubricants to oils with unique compositions that are cosmetics. opening up new applications as raw Ken Hammond/USDA 92BW0693-35 for products ranging from lubricants The oils can be used directly for dust to plastics and from cosmetics to in- control or as carriers for pesticides. dustrial chemicals. Alcohols such as methanol or ethanol Seed oils consist primarily of a can react with the oil's triglycéride to chemical form called a triglycéride. give what is called a fatty acid ester, These triglycérides are liquids at room which is useful, among other things, temperatures and insoluble in water. as a substitute diesel fuel. Vegetable Some triglycérides are stable at high oils can be converted to glycerol (used temperatures because they are either in cosmetics, synthetic fibers, explo- saturated (nonreactive) or partially un- sives, etc.) and fatty acids through the saturated (somewhat reactive). These chemical addition of water to the oils, used in cooking, include com oil, triglycéride. peanut oil, safflower oil, olive oil, and The fatty acids of soybean oil and sunflower oil. Others, with high levels (from wood, primarily pine) of chemical unsaturation, are valuable are used to make materials included in either because they are chemically re- hot-melt glues and in the curing com- active or because they contain unusual ponent of epoxy glues, while the fatty chemical structures. acids in coconut oil are the major in- Vegetable oils can react with other gredient in soaps and detergents. materials to form either a much Other uses for fatty acids include fab- thicker liquid (a lubricant) or solids. ric softeners, cosmetics, plastics.

88 Part III. Products From Nontraditional Crops paints, coatings, inks, antifoaming descriptions of how scientists are agents, minerals processing agents, searching for new oil crops while, at and mold release agents in foundries. the same time, pursuing new uses for In short, whether we realize it or not, several of the seed oils. we use vegetable oils in our everyday life for many things we would be hard Starches pressed to do without. Traditionally, we view com, potatoes, Many new uses of seed oils are tapioca, rice, and wheat as foods for now being developed to take advan- human and animal consumption, not tage of their natural functionalities. as sources of a naturally occurring Soybean oil has been modified to re- starch. But these food items are im- place petroleum in inks for newspaper portant sources of industrially useful . (The 1991 and 1992 Year- starch, a polysaccharide ("many sug- books of Agricultue were printed with ars") consisting of a long chain of in- soy ink.) A number of nylons based on dividual glucose (sugar) units. oils from other crops, particularly ny- Today starch is an important raw lon-1 1 and nylon-13,13, are being material for the chemical industry. For evaluated for use as engineering plas- instance, the paint and coatings indus- tics in the automotive industry. New, try has utilized starch and its deriva- flexible coatings and paints can be tives as stabilizers and flow modifiers made from rapeseed and crambe oils. for latex paints and other water-dis- The functionality of each oil is persed coatings. Starch is also used as unique. The fatty acids in each oil are a binder in explosives, for example for different, and therefore each oil's abil- fireworks and industrial applications. ity to react is different. The unsatur- Starches can be acidified, dried, ated bonds in the fatty acids that make heated, and cooled to produce either up the triglycérides are reactive; that British gums or white and yellow dex- is, they can combine with other trins, which are used as adhesives. The chemicals easily. So, when we delib- specific nature of the product is con- erately add oxygen, sulfur, or phos- trolled by the processing. phorus to the unsaturated bonds in a Unmodified starch has been used triglycéride, we can make a lubricant, for many years to size textiles. a rubber additive, or a wax. The reac- consists of passing a yam through a tivity of unsaturated bonds in fatty ac- solution of starch to deposit a coating ids also leads to the production of raw of starch over the surface of the yam materials necessary in the manufacture to bind individual fibers into a smooth of nylons, polyesters, waxes, and other strand. After heating to dry the sizing products. agent, the coated or sized yam is ready The natural structure of seed oils for weaving. During weaving, a yam allows us to create unique products is exposed to abrasion and tension, for use in all facets of our daily lives. and sizing provides abrasion resis- In some of the chapters of this year- tance and strength for the fibers. book, you can find more complete Starch is commonly used in a wide

New Crops, New Uses, New Markets 89 variety of adhesives, particularly those adhesives, medical poultices, - designed to bond paper to itself, glass, making, coatings, dentifrice powders, or other materials. It is also useful for and refining and for making tab- binding mineral wool in ceiling tiles lets, binders, and disintegrants. and for binding clay in ceramics. The Carboxymethyl starch is also used for overwhelming majority of all starch textile printing and as a component in used for adhesives is used in the pro- film-forming mixtures. Other applica- duction of corrugated board. Other ap- tions of carboxymethyl starch are as a plications are in the manufacture of thickening agent, flocculant (to en- paper bags, bottle labels, gummed hance settling of suspended solids), tapes, envelopes, and a variety of antisoil-deposition agent (to help sur- poster pastes or billboard-type appli- faces repel dirt), and chelating agent cations. Starch-based adhesives are (to combine with dissolved metals). the materials of choice for Modification of starch to and other pasting operations requiring cyanoethyl-starch provides water the alignment of patterns and edges. dispersability, resistance to swelling, The structure of starch can be excellent adhesive properties, and in- modified or changed by a number of creased fiber absorbency. Methyl- chemical reactions. Among them is starches are used as thickeners, protec- the reaction of starch with tive colloids, soil-suspending agents, dithiocarbonic acid to make what is and detergent compounds. Ethyl- called xanthated starch. Applications starches are used primarily in the pa- for xanthated starch include wastewa- per industry as a component of sizing ter treatment, slow release of volatile formulations, a pigment adhesive, and chemicals such as pesticides, fillers for other specialty coatings. for powdered rubber, and paper- Plastic is so widely used in all fac- making. ets of everyday life that its disposal af- Modified starches are used exten- ter use has become a serious problem. sively in the paper industry. The Many applications—food packaging, starch acts as a binder for paper to en- disposable plates and utensils, and hance its dry strength and imparts de- medical items such as syringes—have sirable water retention properties that a fairly short useful life and are not, or prevent excessive dewatering during cannot be, recycled. Starch-derived the process. Modified materials that are truly biodegradable starch is also used to thicken coatings are leading candidates to replace used on paper so that they are smooth nondegradable petroleum-derived and nonsagging. This application is plastics. The chemical functionalities similar to using starch as a thickener of starch allow it to be used in the in cooking a stew. Starch also is the preparation of polymers that can be "carbon" in carbonless paper. formed into films or solid shapes and Starch modified with monochloro- that can retain their properties acetate is called carboxymethyl starch throughout the useful life of the prod- and is used as an absorbent in ucts. When the starch-based products

90 Part III. Products From Nontraditional Crops must be disposed of, they can be con- which are used in explosives and sumed by microorganisms, for ex- Ping-Pong balls. ample in composting systems. The least utilized component of lignocellulosic materials is lignin. Lignocellulosics are highly complex polymers By weight, the largest component of that consist of phenolic rings (six car- plant matter is lignocellulosic mate- bons in a ring with a hydroxyl group rial—a mixture of cellulose, hemicel- attached) that are connected by combi- lulose, and lignin. The relative nations of carbon and oxygen link- amounts of the three lignocellulosic ages. Lignins can react with sulfuric components depend on the type of acid to produce a group of compounds plant and, to some extent, the age of called , which are used the plant. as binders (in wallboard) and dispers- Traditional uses of lignocellulosic ing agents (in pigments). materials have taken advantage of Most of the commercially available their fibrous nature, which is a result lignin is a byproduct of paper produc- of the long polymer chains of cellu- tion, which uses sulfur compounds to lose and hemicellulose. Common separate the lignin from the cellulose lignocellulosic materials are wood and pulp. The lignin coproduct, called paper pulp. In fact, paper is almost "black hquor," is used as the primary pure cellulose. source of carbon disulfide (a chemical Cellulose and hemicellulose poly- intermediate in making other sulfur mer chains can be hydrolyzed (a compounds) and dimethyl sulfoxide chemical process in which water is (an organic solvent). Sadly, though added, breaking the chains) into indi- there is an oversupply of lignin, the vidual sugar molecules. These sugars most valuable structure within the lig- can then be fermented into a number nin, the phenol ring, continues to be of commercially important chemicals little utilized. Essentially all of the through the action of yeasts and phenolic compounds in industry, in- bacteria. cluding most synthetic dyes, are made Because cellulose is a stable natural from petroleum or coal, not lignin. polymer, it is much more difficult to Finally, lignocellulosic materials hydrolyze than hemicellulose, and its can be viewed as the most abundant hydroxyl groups (bonded hydrogen source of carbon-hydrogen-oxygen and oxygen) react easily with other (C-H-0) compounds that we have. chemicals without destroying the basic Through the processes of pyrolysis/ polymer. This can be an advantage in gasification (thermal degradation in making a number of important cellu- the absence of oxygen for combus- lose derivatives: cellulose acetate, tion) and liquefaction (depolymeriza- which is used in photographic film tion into a variety of smaller and various coatings; rayon, which is compounds), it is possible to produce used in textiles; and cellulose nitrates. the equivalent of synthetic crude oil,

New Crops, NGW Uses, New Markets 91 synthesis gas (a mixture of carbon of the cheapest per unit weight as well monoxide and hydrogen), and syn- as one of the most abundant renewable thetie natural gas. These materials, in resources that we have. turn, provide raw materials identical to those used in the existing petrochemi- Summary cal industry. Plants contain a host of compounds In summary, lignocellulosic materi- that are chemically useful in making als are a resource that will always be industrial products. To develop indus- produced at the same time that we are trial products, we need to think of producing crops for food, feed, fiber, plants not just as commodities but as or chemicals. Wood wastes, harvest- "living factories" for chemical raw able field residues, and most food- materials. The major materials present processing wastes can be collected as in all plants are the three described sources of lignocellulosics. The here—oils, starches, and chemical functions of lignocellulosics lignocellulosics—and protein and permit their use either directly as naturally derived chemicals. Together, chemical derivatives or indirectly as a these materials are the source of a source of C-H-O compounds for fur- broad range of products from medi- ther chemical synthesis. As a category cines to , from jet engine of materials, lignocellulosics are one lubricants to lipstick. □

by Charles S. Taylor, Genera! Kenaf: Manager, Kenaf International, McAHen, TX, and Daniel E. Kugler, Director, Annual Fiber Office of Agriculturai Materials, CSRS, Crop Products USDA, Washington, DC Generate a Growing Response From Industry "Don't put shade on it." newer groups of interested farmers in That is the only general crop man- the Mississippi Delta, the plains of agement recommendation for the Oklahoma, the tidewaters of the Caro- steadily increasing number of kenaf linas, and the valleys of California— growers in areas of south Texas and are quickly learning that growing this southern Louisiana. They—along with annual hibiscus is compara-

92 Part 111. Products From Nontraditionai Crops