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T H E J O U R - V A L OF I N D U S T R I A L A N D ENGIAVEERING C H E 3 I I S T R Y
Gentlemen, I have singled out the industry of Corn Products because it furnishes one of the most striking examples of what efficiency has done for the development of a chemical industry within a comparatively brief space of time. Unlike other industries, such as steel or sugar, our industry is a conglomerate of a number of others. Per se, the manufacture of starch has nothing to do with t h a t of oil; the manufacture of corn syrup nothing in common with the production of concentrated feedingstuffs; the manufacture of dextrines nothing with t h a t of dextrose, etc., yet these various departments are so related to the whole as t o form inseparable parts of it, and the efficiency of the whole depends, therefore, upon the efficiency of each branch. The net result of our efforts with respect to efficiency is perhaps best illustrated by the fact that we pay to-day for our Taw material-corn-three times as much as did our predecessors, and yet we sell our products in the markets of the world a t one-third of their prjce. To continue the increase of this efficiency, it is necessary t h a t we have young men with the proper training-not only men with a scientific schooling, but men who have received thorough training in engineering, who know the parts and functions of machinery and apparatus, who have a fair knowledge of factory operations, and who have a general understanding of the principles of manufacturing. It is gratifying to note t h a t the number of colleges and universities is increasing from year to year, where a course of chemical engineering is added to the curriculum of the chemical student. The chemical industries of this country have grown from a small beginning into a position of great importance. A large share of the credit is due to the schools which furnished the men. They must give us men of ideas, men with initiative, men with mental and physical equipment to carry their creations of mind through into creations of fact. No matter how small a cog the individual may be in the big wheel of industry, he may ne11 be proud of his share in the building up and development of the chemical industries, which contribute materially toward the prosperity of this country. If his work goes unnoticed by the public-at-large, he can find comfort in the fact that “The greatest joy of those who are steeped in work, and who have succeeded in finding new virtues and understanding the relations of things to each other, lies in work itself.” Such \Tork cannot result other than in efficiency. Efficiency stands for all t h a t is great and potential. Efficiency is the making of a man. Efficiency is the making of an industry. Efficiency is the making of a nation UTILIZING WOOD WASTEJ B y JOHN E. TEEPLE I. INTRODUCTORY
I have been asked to give a general survey of the field of chemical wood waste utilization: what has been acccomplished, what is being done, what are the prospects. In such an address many interesting details must be omitted, many subjects passed over lightly or merely mentioned: much of the material presented will be familiar to many of you, and a part to all of you. Man has been utilizing wood from the beginning. Wherever we find him in history, even as a barbarian, he has known how to make charcoal and probably tar from wood, if he had the wood; and there was abundance of wood. Central and Northern Europe were almost entirely forest or swamp. The larger part of our own country, excluding the middle western prairies, was covered with trees. Nearly this whole state of New York, this spot on which we stand to-night, was a forest. There was no waste wood, or it was all waste, just as you choose to con1 Paper presented before the New York Section of the Society of Chemical Industry, Chemists’ Club, -4pril 2 5 . 1913.
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sider it. The whole forest mas a huge storehouse from which man drew indiscriminately whatever was best suited or most accessible for timber, for lumber, for charcoal, for tar. Th? settlers cleared: millions of acres for agriculture by simply chopping down the trees and burning them where they lay. It has remained for our own time, our own generation, the last few years in fact, to develop a problem of wood waste utilization and to make some progress toward its solution in a chemical way. I n our day, ideas of conservation are prevalent and directing. The tar or charcoal burner of two or three hundred years ago in Russia or Sweden, and more recently in the Carolinas, centered his interest in the tar for his ropes or the charcoal for gunpowder or metallurgical purposes. To-day me approach the same manufacture with a view to utilizing waste materials. Here are certain residues unsuited for lumber, lath, railroad ties or box shooks, good only for fuel and unsalable a t fair prices as fuel. What shall we do with them? Shall we or can we make tar or rosin, or alcohol or paper, or anything else that is marketable. and can we also secure a profit in doing so? The profit side is important because no matter how remarkable transformations are accomplished, or how interesting the process may be from a chemist’s view point, still the law holds: no profit, no industry. I n this discussion we shall restrict ourselves mainly to this continent, mentioning only incidentally the work in Russia, Sweden, Austria Hungary, and other European countries. Our subject of wood waste naturally excludes most of the manufacture of paper pulp from spruce, poplar and hemlock, and some of the hardwood distillation, the extraction of tanning materials, dyestuffs, etc. I n these excluded cases we are not specifically utilizing waste materials but are competing for the purchase of raw materials which are in some demand for other industries. 2 . RAW MATERIALS
A list of the important woods of this Continent, which from their use for lumber would be a source of wood waste, would extend to more than a hundred names. For our purpose me may classify such as are of present interest as follows: First, the Longleaf Pine (Pinus palustris) in all the states touching the Atlantic Ocean or the Gulf of Mexico from North Carolina to Eastern Texas. This wood is exceedingly rich in resins and terpenes, and this tree makes the Cnited States the largest producer of turpentine and rosin in the world. Second, the Shortleaf Pine (Pinus echinata) of the same distribution but extending farther inland, especially in Arkansas and Missouri, contains comparatively a small amount of resins and terpenes. The Loblolly (Pinus taeda) and the Cuban Pine (Pinus Cubensis) are intermediate between these two in their characteristics. These are the most important Southern pines. I n the North, the h’orway Pine (Pinus resinasa) occurs in Minnesota, Wisconsin, Michigan and the Province of Ontario. It does not occur in forests, but is scattered among other timber and in groves. A large portion of this has already been cut, and the waste for our purpose is in the form of stumps on uncleared lands. Like the Longleaf pine and other resinous trees these stumps do not rot. The bark soon falls away, the layer of sap wood decays, but the remainder apparently becomes more resinous with the years. On the Pacific coast the Douglas fir (Pseudotsuga Douglasii) is especially abundant in British Columbia, Washington and Oregon. Individual trees vary considerably in character ; some are rich in resins, particularly where i t has collected in pockets or wind shakes: others contain very little. The amount being cut by lumber mills is very large, and any method of utilizing the waste either from mills or from stumps must recognize the variation and select the material suited for its purpose. We next have the class of wood suitable for what is called hardwood distillation and including white pine, maple, oak, beech, birch, chestnut, ash and some other broad leaved woods.
These are the chief types having marked characteristics that hare led t o especial efforts for utilizing their waste. Considering ncxt the form of waste. the most immediate one is lumber mill refuse. It consists of the sawdust, the slabs, edgings and ends of the lumber. The sawdust and ends m-ill have about the same average composition as the logs, but slabs and edgings contain a larger percentage of bark and saptvood. ,411 the refuse is, of course, green and contains twenty-five to fifty per cent moisture. IYlien cutting Longleaf pine that has been boxed for turpentine, many of the slabs are ve? resinous. Second, the limbs and tops left in the woods by lumbering operations: some of this can be gathered for hardwood distillation, but with the amount of other waste more available, the greater portion remains in the woods and soon decays or is burned. Third, the stumps: in resinous conifers these are the richest and most valuable for recovery of turpentine and rosin. Other stumps are too irregular and too expensive to utilize a t present. A fourth form is the resinous "lightwood" from Longleaf pine trees which have died standing or have been blovn dolvvn by winds. This has heretofore furnished a chief part of the coniferous wood used for distillation. 3.
COMPOKESTS O F T O O D WASTE
Disregarding the bark, we may consider all trees as composed of cells and ducts or interstices through which the sap flows. These cells are added in rings or layers externally, one ring for each year: a light colored part representing the spring growth and a darker colored part the summer growth. In conifers the colors are so sharply defined as to present two distinct rings, the summer growth here containing much more resin than the spring growth, and the percentage of summer wood decreases regularly from stump to top I n young trees the cells consist entirely of cellulose; in age they become encrusted with lignin or a ligno-cellulose ester. The sap is largely water. Green wood contains twenty-five to fifty per cent water, air-dried wood about twenty per cent, and wood dried a t I j O o carefully may be entirely freed of water. Such dried mood contains about I per cent mineral matter and the remaining cellulose and lignin contain about fifty per cent carbon, six per cent hydrogen and forty-four per cent oxygen. In addition, resinous conifers contain oleoresins, differing somewhat in each species. These are apparently simple mixtures of resin acids (rosin), volatile terpenes (turpentine), and in the case of lightwood, various higher boiling terpenes, terpene alcohols and esters (pine oil), probably formed from the terpenes by hydrolysis and oxidation. These pine oils occur in small quantities in green wood, but do not appear to any extent in the gum flowing from Longleaf pine trees when they are chipped for turpentine. Water, cellulose, lignin, and the oleoresin which contains rosin, the terpenes and terpene derivatives, are the only constituents of any class of wood waste so far as Tve are concerned. Any other products derived from wood waste can come only by chemical transformation or decomposition of these constituents.
4. THE
P R I X A R Y MARKETABLE PRODUCTS
(a) Paper Pulp.-iVe
have mentioned cellulose, or a t least the cellulose part of the lignocellulose complex as one component o f wood waste. By removing the other constituents we can obtain cellulose, and wood waste then can be an important source of paper pulp. Hitherto it has not been. The raw materials for both chemical pulp and mechanica! pulp or wood flour usually have been carefully selected and axe comparatively high in price. This high price has caused diligent and successful search for other raw materials. Sapwoods of Shortleaf and Loblolly pines were commercially added to the list of pulp woods. The investigations, naturally extended to wood wastes, showed that most of them from Southern pines a t least were capable of yielding merchantable paper pulp under proper treatment by the soda
or sulfate methods. The sulfite method is said to be less satisfactory. It has still to be demonstrated whether the number of plants now projected will repeat in a commercial way the success that has attended the laboratory experiments in a chemical way. It is doubtless true that nearly any laboratory success or result that indicates financial profits can be repeated commercially: but the development of a laboratory process into a working plant paying dividends is a much harder task than is often realized, and many times requires years of united effort on the part of the best chemists, engineers, chemical engineers and business managers before it is accomplished. I n this specific case, a t least onc plant has made pulp from waste wood, and transformed the pulp into very good grades of wrapping paper that have found a market. We are discussing the state of an industry and this one example brings paper pulp into our province. The advantages of waste wood for paper pulp are its cheapness and its quantity. The disadvantages are several. If made from mill waste the wood is green, full of water, has a large percentage of bark, and comes in irregular shapes. This means poor quality of pulp or large labor cost in selecting and greater manufacturing cost. If dead or fallen timber is used in conjunction with turpentine and rosin extraction by solvents, it will contain a large proportion of knots and charred wood unless carefully separated by hand. Shavings from a planing mill are comparatively free from all these disadvantages, and this has been used with success. ( b ) Ethyl Alcohol.-Since wood waste contains cellulose, it must be regarded as a source of ethyl alcohol. The raw material used is bulky compared with the finished product and must be cheap in initial cost and have no labor charge for preparation or handling. This has so far restricted it to unselected mill waste from large lumbcr mills. Hydrolysis of the cellulose with very dilute acid produces glucose and fermentation of the glucose and distillation of the resulting mash gives a v e v satisfactory grade of ethyl alcohol. Some of the patents are over twenty years old. An unsuccessful plant was established in Xississippi nearly ten years ago. The processes are beautifully simple on paper, and in the laboratory, but it is only now that we can begin to say we have such a manufacture commercially. Years of experiment have been spent in determining the most favorable conditions of hydrolysis. The kind of acid, sulfuric, sulfurous, or hydrochloric, the per cent strength of acid and proportion to wood, the amount of water, the temperature, pressure, time, have all been found important factors in hydrolysis to obtain the maximum yield of fermentable sugars, and the minimum loss of those sugars by decomposition. Then problems of proper neutralization of the saccharine liquors and removal of extracted materials that prevent or retard fermentation; the development of special yeasts and fermentation methods for the liquors; the treatment of residues to furnish suitable fuel for the plant. All these problems have now received solutions adequate enough to furnish a total production of 5,000 to 10,000 gallons ethyl alcohol per day from wood waste in two plants, one in South Carolina and one in Louisiana, both working on mill waste from Southern pines. The field is an interesting one, and in view of its possibilities should be attractive to investigators. (c) Acetate of Lime, LC-ood Alcohol and Charcoal.-When wood is heated somewhat above zooo decomposition begins. Water distils first, then dilute acids, mainly acetic. At about 27j0 considerable wood alcohol is in thc distillate, and light tar oils and gas are flowing freely; a t a higher temperature heavy tar oil flows, and finally only charcoal is left in the retort. With uniform and careful heating 350° produces good charcoal and 300° brown charcoal, although observed temperatures on retorts are usually higher owing to unsatisfactory heat distribution and transmission. The reaction is exothermic and above
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T H E JOI-R.Y.-ZL OF I-VDL-STRI.4L *-Z-\-D E.I-GIAYEERIAYGC H E J I I S T R Y
280°, with proper insulation, will support itself. Cellulose distilled alone gives no methyl alcohol, but otherwise the phenomena are the same. IVe must look to the lignin part of the wood for the methoxy groups furnishing methyl alcohol. No matter what wood is distilled there will be the same products, varying, however, in quantity with the kind and dryness of wood and with the rapidity of heating or speed of removing products from the retort during distillation. The manufacture of acetate of lime, n-ood alcohol and charcoal has not been essentially a wood waste utilization industry. Individual plants often take a part of their vood in the form of slabs from adjacent hardTvood sawmills; one small plant recently started operating in Tennessee on oak slabs, but commercial figures are not yet available. I n the main, plants have been established not primarily to use ivaste material, but t o supply a demand for charcoal in nearby blast furnaces. Slabs are, of course, cheaper than cordwood, but the yields obtained from them are somewhat smaller, and a belief has existed in many quarters that they could not be satisfactorily distilled alone. The yields from good air-dried hardwood are, of charcoal 30 per cent, or a little less, wood alcohol I O gallons per cord, 82 per cent gray acetate of lime zoo lbs. Pine woods give much smaller yields, the type usually distilled in the South, for example, producing only about 20 per cent charcoal, one t o two gallons methyl alcohol per cord, and j o to i j pounds acetate of lime, either brown or much more difficult to refine than the product from hardivood. Recovery of these smaller amounts of alcohol and acetate has been attempted in a commercial may, but is now entirely abandoned. Charcoal from pine wood usually commands a ready sale for household or manufacturing fuel, if the plant is favorably located. ( d ) Turpentine, Pine Oil and Rosiir.-Coniferous woods in general, and the Longleaf pine, Norway pine and Douglas fir in particular, contain oleoresins. These are partly physiological and mainly pathological secretions of the resin ducts, and are not to be confounded with the sap of the tree. When a coniferous tree is vvounded a secretion flows from the wound. In the case of the Longleaf pine, the wound must be re-opened by chipping a t least every week to keep the gum floxing. Since the oleoresin is so largely a pathological product, the more the tree is v-ounded and the larger amount of oleoresins lye take from it, in this manner, the more remains or is formed in the body of the tree, and the richer we find it when we work it up as waste wood. This oleoresin may be completely separated by chipping the wood and extracting thoroughly with a solvent. Fractional distillation of the extract, usually in the presence of steam, separates it,into solvent, turpentine, pine oil and rosin. These are the only products directly obtainable from the oleoresin, and none of these is obtainable from any other portion of the wood excepting the oleoresin. Of course, it is not necessary to isolate the oleoresin. Direct heating of the wood will drive off the turpentine and pine oil, and if the heating is continued, will melt out part of the rosin, decompose the rest of it, and mix rosin naphtha or rosin spirit n-ith the turpentine. Simple steam distillation of the vood will remove most of the turpentine and pine oil alone. However these products are extracted, they will be slightly different from the turpentine and rosin obtained by chipping the tree. The turpentine is liable to be contaminated with the products of distillation of the rosin, or of the wood, or of the bath, or of the solvent used in its preparation. If considerable heat or pressure has been used, particularly in the presence of acids either already in the wood or derived from its decomposition, partial transformation of the pinene to dipentene occurs. Methods of refining have now progressed so far, however, that where proper care is used in manufacture, a very satisfactory and uniform turpentine is marketed. It has a slightly different odor from gum turpen-
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tine, and even the best of it in a commercial way does not quite meet the specifications as to the amount distilling between certain limits, as does gum turpentine. This is apparently due to a slightly larger content of dipentene or B-pinene or both. This difference in proportion of constituents makes a slight difference in its solvent power. \%-hen properly made and refined. it finds widely extended use wherever gum turpentine can be used. So far as I know, it contains no constituents that are not present in ordinary gum spirit of turpentine. The rosin extracted from wood has usually been of about a n E grade, so far as color is concerned, but has been somewhat softer than the corresponding grades of gum rosin. This is due to a certain amount of heavy oils, about one per cent, which still remains in the rosin extracted from wood. This remaining one per cent of oil can be removed under proper conditions, and when this is done the rosin extracted from wood is not in any respect commercially different from the gum rosin. Most of the plants up to the present, however, have not removed this last fraction of heavy oil, and have been content to market their rosin in industries where the oil content would not interfere with its use. Pine oil is a mixture of terpene alcohols, esters, ketones, and other derivatives boiling mainly between 2 I O O and zzjo. The ordinary product has a gravity of about 0.940, although special products are put out of either higher or lower gravity. Its chief constituent is terpineol. ilbout twenty different terpene derivatives in all have been isolated from it. I t finds quite an extended use as a solvent, and also as a raw material for manufacturing or isolating various terpene products. ( e ) T a r , T a r Oils,Creosote Oils,Pitch, Light Oils,Li.ood Oils, Gas.-Whenever cellulose, lignocellulose, or any variety of wood is distilled, we obtain gas, tar, and light oils. In the case of hard woods, the gas and tar are used entirely for fuel to aid in the distillation. Tar from hard wood has not so far been worked u p into marketable products, with the exception of some of the light distillates of the tar known as wood oils, which ha\-e found a limited market in manufacturing shingle stains and similar products. W'hen we distil a resinous wood, the decomposition products of the rosin are mixed with those of the wood. In this case the tar becomes naturally much more valuable. It finds a ready market as such, particularly in the ropc-making industry, or it may be distilled and refined to produce tar oils, which find a limited market, particularly in the drug trade, creosote oils, which find a very fair market in special industries, and which should be largely used in preserving timbers, if the price of coal tar preservative continues to rise. The light oils from resinous moods, which are bctwccn t a r oil and turpentine in their character, find a very limited market. The residue from distilling tar is pitch. YOU find this same residue in distilling rosin, and of course in distilling rvood where the temperature inside the retort is properly controlled. Pitch is readily marketed both in this country and abroad. These are the main primary products produced from wood utilization plants. It is obvious that no one plant can produce them all. If, for example, the rosin is extracted and sold as rosin, there will be no production of marketable tar and pitch. ij) Cattle Foods.-\X'e have noticed that the cellulose of wood and possibly part of the lignin can be hydrolyzed rather easily to form glucose. There are, of course, a number of other sugars formed, the total from pine wood being about 23 per cent; from hard wood, possibly 2 6 per cent or more of the dry wcight of the wood. I n addition, there are other soluble carbohydrates and considerable quantities of unchanged cellulosc and the lignin part of the molecule. A large part of the soluble carbohydrates are presumably thoroughly digestible, and as cattle ' are able to digest certain varieties of cellulose, it is possible t h a t a certain percentage of the insoluble portion may be digestible. \Vhen this digested wood is mixed with cane syrup, peanut I
meal, rice meal, alfalfa, etc., it seems to make good cattle food and finds a market. j . THE S E C O S D A R Y P R O D T C T ?
( e ) Acetic Acid and Acetone.--Nearly all of the acetic acid and a very large part of the vinegar in this country is produced directly from acetate of lime by treatment usually with sulfuric acid and more rarely with hydrochloric acid. The acetate of lime is usually shipped from the point of manufacture to separate chemical plants for its further conversion. The manufacture of acetonc in the same way is entirely dependent on the \rood utilization industry. I t is made exclusively by direct distillation of acetate of lime. This being the source of acetone, it follows that indirectly the manufacture of chloroform and iodoform are dependent on the same industry. ( b ) Camplzor.-A number of processes lead from pinene, the chief constituent of turpentine, to camphor, and some of these a t times have been placed on a commercial basis. When turpentine was fifty cents per gallon and camphor one dollar per pound, this was a profitable industry. When turpentine went to one dollar per gallon and camphor to fifty cents per pound, i t was an unprofitable one. To-day, so far as I know, camphor is not being made synthetically. Whenever there is a rise in the price of camphor, or a decided improvement in the yields of camphor obtained, there is no reason why it should not again become an industry. On the other hand, if the use of camphor should decrease, due possibly to a more extended use of other materials in place of celluloid, it might never be a profitable industry again, even with low-priced turpentine and good yields. (c) Rosin Oils.-When rosin is heated in the neighborhood of 300°, or a little less, a steady and uniform decomposition occurs, giving water and light rosin spirits, and afterwards rosin oils. Some of these oils find extended use in the manufacture of axle grease and other lubricants, others in making printing ink. The pitch residue remaining in the still has already been mentioned. Rosin extracted from waste wood gives the same products, but unless the heavy oil mentioned above has been entirely removed from the rosin, the oils have rather a sharp odor, which must be removed before they can be used, for example, in printing inks. A good many attempts have been made to devise a process by which resinous wood could be converted into paper pulp by the soda method, and the soda liquors which contain rosin distilled directly for the production of rosin oils. This can be done, and has been done in a small way, but the rosin oils obtained differ from the ordinary commercial product, being lighter in gravity and more mobile, and the process is not to-day a commercial success. I n no case at present are rosin oils being manufactured in the primary wood utilization plants. ( d ) Il'ood Preserz'ative and Paints, Disinfectants, Sheep Dip.Tar is often a source of delight to the organic chemist, because it is so full of possibilities, but it is always a source of discouragement because of the difficulty of realizing those possibilities. Tar and its various distillates contain considerable amounts 'of cresols and their derivatives. It is fairly easy to obtain distillates xhich have good properties as wood preservatives, 'either for impregnation or, when mixed with pigments, for external application. It is also fairly easy to obtain distillates having about the consistency of linseed oil and which may be of .value in certain external paints when substituted for the linseed oil in the paint. I n either way, there is here a valuable source of wood-preserving material, and i t has been utilized, although in a very small way, for a great many years, particularly in railway equipment. This same occurrence of cresol has led t o a great variety of disinfectants for stables, for lavatories, for sheep dip, etc. Pyroligneous acid obtained from resinous wood is chiefly water, but it contains small amounts - granted by the L-. S. patent; because the grant is only a contingent liability, a right to sue; because our “priority of conception” doctrine with its interference proceedings, helps t o make the title to any invention problematical el-en after a patent grant; because searches, often slovenly, arc made through a woefully incomplete and partly unclassified record of the prior art, in part a t least by underpaid assistants waiting t o pass their law exams and find another job: because the absence of public opposition or expert advice from practical men makes those searches academic; and because by every technical complication from the drawing of our claims as permutations of hair splitting, through the multiplicity of appeals to our court practice as it has been (iules of procedure) and to some extent still is ( 9 circuits with untrained judges and contradictory decistons), the great advantage is given a t every step to mere money pon-er. If real estate titles were subject to all these risks, liabilities and uncertainties, who would care to buy a home? n’hy should brain property be thus jeopardized! So when we were informed t h a t “ a s a whole the progress of industrial chemistry i n recent years is recorded _ _ -i n patent literature” it is because the paper was written by a statistician not himself a practical, technical chemist. It nould be surprising if true. Actually progress is barely indicated, as incompletely as the laiv permits, only for those things t h a t can’t be kept secret and only after it becomes necessary to issue the application in order t o defend as best we may rights that are being overrun. Let us proceed to the statistics’-a magnificent piece of statistical work-which it is stated “should not by a n y means be regarded as including those patents relating t o chemical industry which are classi3ed under other dii’isions or sub-divisions” in other Trords, many of the most important truly chemical patents, separately classified because most important. I t was then pointed out as an awful condition of things that the number of chemical patents issued to German citizens ( I 754) is greater than that issued to U. S.citizens ( I j j ~ )t,h a t German Omitted here t o save space-See THISJOURNAL, 4, 329.
