Chemicals from Wood 639 realized^ although even yet the resins It is usually unnecessary, and often do not promise that their bond with detrimental, to roughen the wood sur- wood will be spontaneous^ for the pro- face; in fact, the mating surfaces duction of a good joint generally re- should be machined to a smooth, true quires high pressure, with or without fit. added heat. Animal glue must not be overheat- Phenol-formaldehyde and urea-for- ed. Heating the wood is generally un- maldehyde are the most widely used necessary or detrimental. synthetic-resin glues. Melamine and Glue should be thick, rather than rcsorcinol glues, among the discoveries thin, in consistency when it is pressed. during the Second World War, promise A relatively heavy pressure should good performance, the resorcinols par- be applied to bring the surfaces to be ticularly so because highly durable joined into firm contact until at least bonds can be obtained without hot partial setting has occurred. » pressing. The resins are available as Minor details of procedure can be powders, solutions, or prepared films. varied in any way that will assure a Their special advantage is that they re- proper jellylike consistency of the glue duce surface swelling and the other at time of pressing. changes caused by the water in the less concentrated adhesives, particularly in DON BROUSE^ a native of Indiana, furniture and other fine veneer work joined the Forest Products Laboratory in which they are being adopted. in 1923 and was assigned to work on the problems connected with the ap- THE GLUING OF WOOD is not a sim- plication of wood-working adhesives. ple, infallible procedure, because wood He is assistant to the chief of the Divi- species vary chemically and physically, sion of Wood Preservation at the Labo- and glues vary in source, methods of ratory and has general supervision over preparation, and use. investigations on adhesives, veneer and Findings at the Forest Products plywood production, and sandwich Laboratory after years of research lead panel fabrication. Dr, Brouse has de- to five general recommendations for grees from Purdue University and the applying glue. University of Wisconsin.

CHEMICALS FROM WOOD ALFRED J. STAMM

Chemical processing of wood, up The extraction process, although to the present time, has been limited highly profitable when applied to a few to ( 1 ) destructive distillation, whereby species, is not suitable for all woods charcoal, wood alcohol, acetic acid, and actually utilizes only from 1 to 20 turpentine, and tars are produced, and percent of the weight of the wood. ( 2 ) extraction processes with water or Two rather new processing methods, petroleum solvents that remove the ex- hydrolysis and hydrogénation, show traneous materials, such as tannins, promise of broader application. Hy- turpentine, rosin, and essential oils. drolysis changes the cellulose and other The destructive-distillation process carbohydrate material into sugars. in recent years has not proved to be Hydrogénation causes hydrogen gas to very profitable, because many of the react wâth the wood components at products formerly produced exclu- high temperatures and pressure to sively by the process are now made form liquid products. more cheaply by synthetic methods. The new procedures, together with 640 Yearbook^ of Agriculture 1949 the old; provide a practical approach woods; a large part of that would also to the chemical utilization of wood be suitable. Altogether, those residues residues. equal in weight about half the present Wood residues are especially adapt- petroleum production. Enough wood ed for chemical processing because residues are available, then, to supply wood of any form or size or quality a great new chemical industry. can be used. Sawdust, shavings, slabs, Such a large industry wouíd not be trimming, cordwood, and cull logs are warranted unless its products were in all suitable. Further, the presence in sufficient demand at a price for which the residue of relatively large amounts they could be profitably produced. of knots, bark, and even wood in the The nature and uses of the products early stages of decay does not interfere obtained by the various methods of with most of the processes, although it chemically processing wood can be a may reduce the yield of chemical prod- measure of this demand and value. ucts. Even though it would usually pay to process the hardwoods (broadleaved EXTRACTION diíTers from the other species) separately from the softwoods chemical-processing methods in that it (cone-bearing species) for the reason is highly dependent upon species and that the products and yields from those alters the wood substance only slightly. two general classes of wood differ, it The only extensive wood-extraction in- is not necessary generally to separate dustry is the naval stores industry of them. the South, which extracts turpentine The amounts of wood residues avail- and rosin from old stumps of longleaf able indicate the possible magnitude of and slash pines from which the sap- a chemical industry based on their full wood has decayed. Only the heart- utilization. Naturally, the first wood wood stumps of those species are used residues to be considered for such an because of their high extractive con-- industry would be those that occur at tent. The industry processes about sawmills, veneer mills, and secondary 6,000 tons of stump wood daily to ob- manufacturing plants, because the ma- tain 12,500,000 gallons of turpentine terial is already at hand and a large and 750,000 drums (520 pounds to the part (in the form of sawdust and shav- drum) of rosin a year. Turpentine is ings) is already reduced sufficiently in used chiefly as a paint thinner, a me- size for use. Some 16 million tons of dicinal, and a raw material for making such material now remain unused each synthetic camphor and other valuable year. An additional 27 million tons are synthetic products. The rosin is used burned to generate steam for plant chiefly in soaps, paper size, paints, operations. As soon as its chemical- varnishes, sealing waxes, cements, and processing value becomes greater than plastics. Large amounts of cymene and its fuel value, which at present averages a rosin residue are also obtained. The about $4 a ton, this material, too, will latter is used in plastics and as a binder be available for chemical processing. for sand in foundry cores. The total mill residue is equal in Chestnut wood chips and hemlock weight to one-fifth of the national pe- bark are extracted to obtain tannin for troleum production. Left unused in tanning leather. In no case is the tan- the woods each year, because their re- nin content of wood sufficient to make moval is considered unprofitable, are extraction profitable for it alone. In 44 million tons more of cut wood, the case of chestnut, the extracted chiefly crooked, split, and partly de- chips have been used to form pulp for cayed material unsuitable for lumber paper making. The chip residue might but admirably suited for chemical use. also be used for further chemical Still another 23 million tons of stand- processing. ing timber are killed by fire, lightning, Years ago a small industry existed in or insects each year and left in the the Northwestern States in which the Chemicals from Wood 641 butt logs of western larch were ex- cordage, and also in medicináis. Both tracted with water to remove the large softwood and hardwood tars find use amount of water-soluble gum that they as flotation oils in mineral separation contain. The gum was chemically con- and as gasoline gum inhibitors. The verted to mucic acid^ which is used as heavier fractions are used as preserva- the gas-liberating acid in some brands tives, disinfectants, and stains. The of baking powder. The process was not pitch finds use as a waterproofing and a financial success because the large insulating agent and as a binder for amount of chip residue was unused. briquets. A number of small plants scattered Although the products obtained by about the country extract essential oils, the two older wood-processing meth- medicináis, and flavoring materials ods named are of considerable indus- from needles, bark, roots, or wood of trial importance and could perhaps be various species. Those plants, like all used in larger amounts than are now other extraction plants, could profit produced, a large expansion in their by chemical refining of their residues. production does not now seem war- ranted. Any real increase in the chem- DESTRUCTIVE DISTILLATION is by far ical utilization of wood will thus have the oldest wood-chemical-processing to be by the processes which produce industry. For years the charcoal resi- products that are in greater demand. due was the only product sought. Char- coal is used as a domestic and picnic HYDROLYSIS of wood to sugars, fuel; in smelting and reducing various followed in some cases by their conver- ores; in making such chemicals as car- sion to other products, is a most prom- bon bisulfide, which, in turn, is used ising chemical approach to large-scale in making viscose, rayon, and cello- utilization of wood residues. phane, and also sodium cyanide, a At the Forest Products Laboratory powerful disinfectant. it was found that sugars can be pro- Now a number of valuable volatile duced to the extent of about half the products are also obtained by con- weight of the wood by a simple process densing the vapors from destructive of heating wood chips or sawdust with distillation. In the case of hardwoods, a dilute solution of acid in water un- methyl alcohol (wood alcohol), ace- der moderate steam pressure. These tone, and acetic acid are obtained as a sugars, which arc a mixture of glucose water-soluble distillate, together with and several diíTerent pentose sugars, the water-insoluble tars and pitches. would be difificult to purify and crystal- Methyl alcohol is used as an antifreeze lize, but can be evaporated easily to a agent in the radiators of automobiles, molasses that contains 50 percent for denaturing grain alcohol, as a sol- sugar. vent in many industries, and for mak- Experiments now under way are us- ing formaldehyde, which, in turn, is ing this molasses as an animal feed. used as a disinfectant and in making The tests have been sufíicient to indi- plastics. Acetone is used as a solvent in cate that it is palatable to cattle and the rayon and plastic industries, and sheep. If its nutrient value proves acetic acid in making white lead paint equal to that of cane molasses, which and acetate rayon and films. Yields of it resembles closely, it could find ex- methyl alcohol, acetone, and acetic tensive use as a livestock feed. Pilot- acid are lower from softwoods than plant studies indicate that about 180 from hardwoods. gallons of molasses can be produced The pines, however, yield consider- from a ton of dry wood at a cost that able turpentine and softwood tar. Soft- should not exceed 10 cents a gallon. wood tar is used in the compounding Cane molasses sold on quantity basis of rubber, to some extent in manu- at 25 to 40 cents a gallon in diilcrcnt facturing oakum for calking ships, in parts of the country in 1948. If its 802002°—49 42 642 Yearboo\ of Agriculture 1949 price could be made as attractive as content alone. The production of wood the pilot-plant studies indicate, the yeast thus also shows promise of de- demand for feed molasses from wood veloping into a sizable industry that could be tremendous. If livestock feed- could use up large amounts of wood ing could be built up to the level al- residue. ready demonstrated as possible with Different cultures and fermentation cane molasses (about 3 pounds per day conditions make possible the manufac- per head for cows, somewhat more for ture of acetic, butyric, and lactic acid beef cattle, and somewhat less for from wood sugars and also acetone, sheep), the amount of molasses used butyl alcohol, and butylène glycol. for feeding could be increased at least Butyric acid is used in making cellu- 75 times. In theory, such a goal could lose-butyrate plastics. Lactic acid is utilize the equivalent of about two- used as a food preservative. Butyl alco- thirds of all available wood residues. hol and butylène glycol can be used in Here, then, is a potential use for wood making artificial rubber. Butylène residue that could consume large glycol would be a good antifreeze agent quantities of it. for use in automobile radiators. The sugar solution resulting from When sugars are formed by the hy- hydrolysis can also be fermented to drolysis of w^ood, a residue of fine solid ethyl alcohol (grain alcohol). Bark- lignin remains. This material, a sub- free softwoods yield up to 60 gallons stance that binds the wood fibers to- of alcohol per ton of dry wood, and gether in a tree, has a higher fuel value hardwoods about 50 gallons. Bark may than wood itself and may be burned as be present up to 50 percent, but its a fuel in the processing plant. It show» presence somewhat decreases the yield. promise as a soil conditioner. When This alcohol is suitable for many in- agricultural crop residues decay, the dustrial purposes. A large commercial remaining humus is largely lignin, so it plant capable of processing 200 to 300 is natural that lignin should have soil- tons of wood residue a day in the man- conditioning value. Lignin from wood ufacture of ethyl alcohol has been built hydrolysis has not shown the value in on the Paciñc coast. The short time plastics found in other forms of lignin in which it has operated has demon- recovered from paper manufacture. strated the commercial possibilities of the process. When shortages of petro- HYDROGéNATION has been most ex- leum products occur, the ethyl alcohol tensively studied on isolated lignin, but produced at such plants could become it may also be applied to all parts of one of our chief motor fuels. It can, wood. In the process, the lignin is sus- under present conditions, be produced pended, or preferably dissolved, in an from wood at about one-fifth of the organic liquid that itself does not react cost of producing it from grain. with hydrogen and that will not de- Only the hexose sugars are used in compose at the high temperatures used. making alcohol. The pentoses remain Most of the work to date has been done in the stills after distillation. They may on batch lots placed in small bombs. A be used for growing yeast or for con- metallic or metallic-oxide catalyst is version to furfural, which is a chemi- used to promote the reaction. A com- cal used as a solvent in oil and rosin plex mixture of liquid products and a refining, in certain plastics, and re- tarlike residue arc produced. cently as a starting material in making The liquid consists of a mixture of nylon. complex cyclic alcohols, phenolics, and Tests are under way to determine neutral oils. The cyclic alcohols, when the food value of wood yeast. It is rich added to gasoline, show good anti- in riboflavin, a vitamin, and conse- knock properties. They are also good quently should have greater food value solvents, and some of them have toxic than is indicated by its high protein properties. The phenolics are a mix- Puttmg Unused Wood to Wor^ 643 turc of those suitable for plastics and neutral oils. Such a plant, it is esti- some that are not. Means of separating mated, could produce, by the combined them have not yet been found. methods, from a ton of dry wood about The neutral oils are of the hydrocar- 110 gallons of liquid fuel consisting bon type. Part of them may prove suit- chiefly of ethyl alcohol and m^.utral oils, able for lubricating purposes, and all together with some methyl alcohol and as fuels. furfural. The proportions of these three types With all these possibilities, the chem- of chemicals formed in the process ical processing of wood residues may may be varied with the hydrogenating well be expected to expand rapidly in conditions. the next few years. Wood may also be hydrogenatcd in aqueous alkaline suspension. The lig- ALFRED J. STAMM^ a Californian, nin forms compounds of the types just joined the Forest Products Laboratory described. When the hydrogénation in 1925 and at present is chief of the conditions are mild, the cellulose left Division of Derived Products. He has is a pulp residue ; when severe, the cel- published a number of research papers lulose is broken down into sugars and on such subjects as particle size in glycerine. The industrial possibilities emulsions^ capillary structure of wood, of such a glycerine-forming process wood and cellulose-liquid relation- must await further research. ships, swelling and its prevention, elec- Before the hydrogénation of either trical properties of wood, and molecu- lignin or cellulose can become an in- lar properties of cellulose and lignin. dustrial reality, methods for carrying Dr. Stamm has degrees in chemistry on the process in continuous-flow from the California Institute of Tech- equipment will have to be developed. nology and the University of Wiscon- The possibilities of commercial hydro- SÍ71. In 1928 he studied in the Uni- génation, however, are promising. One versity of Upsala, Sweden, in order to is to hydrogenate the lignin residue apply the ultracentrifuge technique to from a wood-hydrolysis ethyl-alcohol the study of the molecular weight of plant to obtain an optimum yield of cellulose.

PUTTING UNUSED WOOD TO WORK C. V. SWEET

Every time a saw chews through that they signify neglect or carelessness a log, it spits aside sawdust. Whenever but in the sense that they are not eco- a planer dresses the roughness off a nomically usable. If there is use for board, it throws oil shavings. Square- them, the margin of profit may be edged lumber is made only at the cost discouragingly narrow, the necessary of slabs, edgings, and trims. For every investment for equipment may be pro- log put through the sawmill a consid- hibitive, or the expense of handling and erable tonnage of wood fiber is left in hauling the raw material to one point the forest. Even the digesters of pulp may be excessive. mills disgorge as unusable sizable quan- Theoretically, there is a use to which tities of the wood fed into them. And practically every type of unused wood so it goes with nearly every operation is or can be put. The problem is in concerned with harvesting and con- finding profitable ways of doing it on verting trees into useful things. an adequate basis. Those unused materials generally Only in relatively recent years have have been called waste, not in the sense we come to regard those unused forms