Document 7Mrkm918rL4No9KJ7DeLV1q3j

Utilization of Industrial Wastes H. E. HOWE AND F. J. VAN ANTWERPEN The more important of the large number of in stances are reviewed where industrial or trade wastes are converted through research into raw materials for the manufacture of commercial prod ucts. Differentiation must be made between by products in the usual sense and materials which are true wastes--not only uselflBSinvtoften involving ex pense for their satisfactory disposition. Under such classification may be included the manufacture of sulfuric acid and recovery of elemental sulfur from smelter gases, production of sulfuric acid from hy drogen sulfide in petroleum still gases, and recovery of by-product sulfur from hydrogen sulfide in illuminating gas. Sulfite waste liquor has become the source of vanillin and other products. Waste casein finds its way into resins and adhe sives; the fermentation residues in the alcohol in dustry have been converted into cattle foods and the carbon dioxide into Dry Ice. Potash is recovered from the dusts of the cement industry, and build ing blocks have been made from fly ash. In a sense the long list of solvents now recovered from gases derived from petroleum represent suc cess in the use of otherwise waste materials. The same may be said of cements made from blast fur nace slag, and synthetic methanol utilizes carbon monoxide present as an interfering substance in gases used in the fixation of nitrogen. Furfural from oat hulls, celotex from bagasse, are other examples. S'1 y HIS summary, admittedly incomplete, can provide only Ta background for more intimate discussions of unsolved problems of disposing of industrial wastes. Much of yards and many ancient stories about them. In a similar category are the practices of the forester and lumberman, re ported to do more than the stockyards by utilizing even the this summary is reminiscent. For years one of the proudesbt ark. boasts of chemistry, next to that of devising entirely new prod Commercial utilization of cottonseed and its products ucts, has been the conversion of materials of little value, has become classic, and much of our synthetic organic chemi particularly wastes, into salable products. cal industry, of which we are justly proud, is based on the Industry, generally, is organized to manufacture principal utilization of materials that were waste products. The products. There may be by-products. New economic con fermentation industry depends almost wholly on the utiliza ditions and new demands may reverse the importance of the tion of a waste product of agriculture--blackstrap molasses. main and the by-produot. Too often there is an actual waste At times the demand for this material, together with the more material--that is, one for which no demand exists and whose or less successful efforts at cornering the supply, requires its proper disposal may involve considerable expense. The importation from as far away as the island of Mauritius. This profitable utilization of such an industrial waste is rarely pos may seem strange, for at one time it was difficult to convince sible. Ordinarily the balance from such an operation is on the sugar makers of Hawaii that it would be more economical the wrong side of the books. On the other hand, wastes are to save by-product molasses than it would be to dump it into the responsibility of the many manufacturers, and their dis the sea. posal is part of overhead or operating cost. If a return is realized, this may only reduce cost; but if a profit is made, Pulp and Paper the waste becomes a true by-product. There is an increasing Accomplishments in commercial utilization of industrial tendency for the community to see to it that the burden of wastes should encourage those still facing difficult problems. industrial waste disposal is not placed upon the public, and For years a satisfactory disposition of the waste sulfite liquor the signs of the times are seen in the establishment of legal of the paper industry has been the object of research and de guideposts. It is becoming increasingly difficult merely to velopment. Of late the preparation of commercial products throw away an industrial waste or to discharge it into a con from this material has been much in the public eye. Years venient stream. Some wastes cannot even be burned without ago in Sweden it was found profitable to produce alcohol on a arousing objection from neighbors. large scale by fermentation of the sugars in sulfite waste. One of the earliest examples of legislation requiring the Similar disposition of the material in the United States is not conservation of waste was the Alkali Act of 1863 in England. economical because other raw materials are more desirable. This required alkali works to condense hydrochloric acid gas The fact that over 65 per cent of the waste sugars in sulfite which up to that time had been allowed to escape into the air. liquors are fermentable has led to the creation of bakers' yeast In the Chance process sulfur was recovered from waste pro industries in Finland, in Germany, and more recently in duced in the manufacture of sodium carbonate by the Le Nova Scotia. The plant in Nova Scotia has a reported capac Blanc process. Until that time mounds of evil-smelling sulfide ity of over 20,000 pounds a week and is using waste liquor accumulated near the Le Blanc soda works. from the newsprint plant of the Mersey Paper Company. One recalls the application of law, chemistry, biology, and Sulfite liquor is the raw material of the Robeson prooess for engineering in using the time-honored wastes of the Stock- the production of a tanning compound, and the adhesive 1323 1324 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 31, NO. 11 Courtesy, Chemical Construction Corporation Plant for the Production of Sulfuric Acid from Waste Sulfate Solutions properties of the evaported liquor are utilized in briquetting powdered fuel, in making core binders, and in road treating agents. One of the adhesives, "Bindex", is well known in the trade. In the West the commercial production of a viscous liquid, containing 39 to 40 per cent solids, from sulfite waste liquor has reached a tonnage in the thousands. More recently an anhydrous product has been made in waste-heat stack dryers and vacuum drum dryers. The product, "Raylig", is used as a road binder adhesive. The liquid or the powder may be dissolved or diluted with water and applied as a soil stabilizer for diminishing dust. It also has a binding action similar to that of other organic materials available for the purpose. One of the largest uses of sulfite waste liquor prod ucts is as an adhesive in linoleum cements. This same ma terial, laboratory and field experiments indicate, will be a valuable source of calcium for poultry feeds and a useful spreader for orchard sprays. The foaming tendency of sulfite liquor has led to its in corporation in small quantities in certain soaps (replacing as much as 40 per cent of fatty acids in certain laundry soaps) and to its use as an ore flotation agent. The lignin of sulfite liquor has been isolated and reduced by certain catalysis, to yield high-boiling compounds which may be of value as solvents. Recently it has been shown that lignin may be used to remove iron from water. Impressive is the work of Howard (8) in utilizing the sulfite waste liquors of the Marathon Paper Mills Company. The major objective of research was "to supplement the value of the cellulose pulp by realizing on the commercial potentialities of the large tonnage of noncellulosic organic matter in such liquors". The secondary consideration was the reduction of stream pollution. As a result of this development, Marathon is now marketing a variety of products. The sulfite liquor is treated by a three-stage lime precipitation to yield inorganic and organic solid products and a liquid effluent. The inorganio product, resulting from the first lime treatment, is essentially calcium sulfite which is re-used to make.fresh cook ing acid. The second lime treatment gives a basio calcium lignin sulfonate which may be burned as fuel or made to yield other products. Without further processing other than dry ing and grinding, the lignin product is now being used in car load lots in a material for the manufacture of Portland cement, in boiler feed waters, and in ceramics. Alkaline hydrolysis of of the lignin products yields vanillin, and more than a third of the vanillin consumed in the United States is now of sulfite origin. The effluent from the vanillin process is treated fur ther and yields various lignin plastic products such as core and surface sheets for laminating, molding compositions, and lignin ooating and impregnating resins. The basic calcium lignin sulfonate may be converted into a complete series of lignin sulfonate salts and into free lignin sulfonic acid. Of these the magnesium and sodium salts are being made in ton nage quantities for use in leather tanning, water treatment, and the manufacture of dispersing agents. Thus we see how successful one deliberate research program for the commercial utilization of a waste has been. From the relief gases of the sulfite process p-cymene, sulfur dioxide, and heat are recovered. The sulfur dioxide and heat are re-used. A paint and varnish remover, prepared by mix ing p-cymene with ethyl alcohol, methanol, and acetone, is in such demand that 750,000 gallons are produced annually. At one time black liquor from the alkaline process of pulp manufacture was a serious waste. At present this liquor is evaporated and burned to produce heat and to recover its soda. In some mills activated carbon, which is finding con siderable use in water treatment, is also made. Indeed, this carbon is of such value that the cooking process of one mill is said to be built around its recovery. Another by-product of this soda recovery is the lime sludge from the causticizing of the black ash. This lime sludge is either burned to produce quicklime and again used in more causticizing, or is processed to pure calcium carbonate, whioh is utilized as a filler in the paper or in the produc tion of sulfite cooking liquor. In the kraft or sulfate process, the gases formed during the cooking process contain recover able turpentine, dimethyl sulfide, and tall oil, all of which NOVEMBER, 1939 INDUSTRIAL AND ENGINEERING CHEMISTRY 1325 have several commercial outlets. The sulfate liquor from the digesters is concentrated, processed, and returned to the cook ing kettles. The turpentine recovered meets government standards, and the tall oil is used in the manufacture of soap. The dimethyl sulfide, a highly odorous, volatile material, is, employed as a warning agent in gas lines. Although waste paper is not a problem of the paper in dustry, it is a waste of considerable tonnage and one of the raw materials for paper making. De-inked it becomes a part of a large variety of products. In some instances, notably telephone directories, special inks are used to facilitate a deinking process to be applied later. A sludge results, but thus far no use has been found for it. Much old paper stock finds its way into a number of board products. Broke is, in a sense, a waste product, although it is returned to the paper beaters and re-used. At one time white water from paper mills was simply run into the sewer, but this created sanitary problems and now many paper mills operate on a closed system or have installed some type of save-all to recover fiber and filler and return the clarified water to the paper machine. the utilization of wcod waste resulting from the manufacture of bodies, truck panels, and packing cases. The gas obtained was burned as fuel, and pyroligneous acid was worked for the usual products while the charcoal was graded, pulverized, and bri quetted. Even though motor car construction does not re quire the amount of wood it formerly did, the waste from the manufacturing of truck bodies and packing cases keeps this plant operating steadily. How one product from waste makes available another product from waste is illustrated by the practice of a naval stores company which uses pine tree stumps as a source of rosin. By treating the dark-colored wood rosin with gasoline and furfural, a pale rosin of greater value is abtained. Pickle Liquor Pickle liquor has long been a problem in the steel industry. In 1925 a patent was issued to Stevenson covering a process for producing ferrous sulfate from this material, and a plant of the American Rolling Mill Company, at Butler, Penna., is operat ing under that patent. Wood The manufacture of tanning materials from chestnut wood yields a considerable volume of waste chips. These have been made the basis of an industry producing a variety of corrugated board. In this same field should be mentioned the extensive re search of the Forest Products Laboratories on the utilization of waste wood and saw dust. Some success has come from their efforts to produce a resin from the lignin. The Weyerhaeuser Timber Company con verts waste sawdust into logs by forcing it into tubular molds under considerable pres sure; the heat of pressing causes the sawdust to fuse. By the time the mold, which is mounted on a large wheel, has completed a cycle, the fused sawdust has cooled and has been ejected from the mold. The resultant log-shaped product is an excellent fireplace fuel, burning with an even steady heat. Chemicals mixed with the sawdust give vari ous colored flames which make the fuel par ticularly attractive for holiday use. On occasion, the demand exceeds the supply. The operations of the Brown Company afford a classic example of waste utiliza tion. Originally the company developed a small waterfall to provide power for a saw mill and later a pulpmill. Since there was an excess of power, sodium hydroxide was produced by electrolysis for use in paper manufacture. The chlorine in excess of that needed for bleaching was utilized to make carbon tetrachloride, and later the waste hydrogen was turned to the hydrogenation of peanut oil. The final step was the acquisi tion of 25,000 acres of land in Florida for the production of peanuts for oil for hydrogena tion. The company also pioneered in the utilization of the black liquor from the sul fate process. Hugh K. Moore was promi nently identified with this work. In 1924 the Ford Motor Company estab lished a complete Stafford-process wood dis tillation plant at Iron Mountain, in the hard wood forest distriot of northern Michigan, for Bottom of Stafford Retorts, and Hogged Scrap Wood on a Retort Conveyor at the Ford Wood Distillation Plant, Iron Mountain, Mich. 1326 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 31. NO. 11 The Ferron process is another devised to use waste from steel pickling operations. It is applicable to pickling liquor but not to wash water. It consists of precipitation with lime under controlled pH and temperature to yield a thick slurry. The slurry is filter-pressed, disintegrated, and dried to form Ferron, which is marketed as an insulation and building ma terial. The volume of pickle liquor is such that the ferrous sulfate made from it is very close to an industrial waste. It has been roasted by acid manufacturers as a raw material for fuming sulfuric acid. There is much interest in the action of copperas on city sewage since the material produces desirable floccula tion; it is strongly urged that more city sewage be treated with this material for it has certain important advantages. If this plan is ever widely followed, there would be no surplus ferrous sulfate. The waste product obtained from tanks in which aluminum sheets are pickled is a sediment containing much alumina and free soda. Formerly thrown away, it is now used in the glass industry. Here it was once necessary to buy pure alumina to put in the mixes which also contained silica and soda. Minerals and Metals Practices in the gold mining industry offer an excellent illustration of how more efficient methods may create new sources of raw materials. Amalgamation made it possible to rework the waste heaps from early gold prospecting methods. Cyanidation methods extracted a profitable amount of this precious metal from the material which had been treated by the amalgamation method. Following this, the technique of flotation, which had worked so profitably on zinc and lead slimes, was used to recover the gold not removed by cyanida tion. For some years the sink-and-float process of mineral separation has been under development by the du Pont Company; following a series of successful demonstrations, the pilot plant has been purchased by an operating company and put into continuous service. Although most of the work has been done on coal, separating this material from slate and other noncombustibles, the process may be highly valuable in other parts of the mining industry in working over waste piles left by other processes. Tin recovered by the Goldschmidt process has long found its way into the textile industry in the form of the tetrachloride for silk weighting. The textile industry formerly discarded spent tin weighting baths but now recovers the tin con tent by precipitating as tin hydroxide, which is smelted to metal. Cadmium is a by-product of zinc smelting. Precious metals are recovered from the sludge of copper refineries. Selenium, now widely used in making ruby-colored glass, was once a waste of copper refineries, and antimonial lead is produced by working up the scum from softening furnaces in lead refining. Mineral wool is a generic term covering a num ber of similar products differentiated chiefly by the raw materials from which they are made. Rock wool is made from natural rock or from various combinations of natural minerals. Glass wool is made from silica sand, soda ash, and limestone, with or without scrap glass or other materials. Slag wool represents a commercial use of indus trial waste; it is made from iron, copper, or lead blast furnace slag, alone or mixed with flux mate rials. In 1938 the production of mineral wool is estimated to have been 400,000 tons, and in 1939 the equiva lent of probably 160 cupolas are in operation. There are seventy-one producing companies in the United States oper ating eighty-two plants. There have been many attempts to utilize fully blast fur nace slag. In 1938 thirty-four companies, operating seventy plants, were engaged in preparing blast furnace slag for the market. This material goes into concrete for roads, paving, and building operations, and is used as railroad ballast and roofing, for sewage trickling filters, in agriculture for its phos phorus content, and as a source of mineral wool. Some of our largest cement works utilize blast furnace slag as one of their raw materials. An excellent example of slag utilization is offered by the Eagle Picher Lead Company at Joplin, Mo. During the first years of the depression a process was developed to utilize the material for the manufacture of a specialty insulation. The considerable demand which developed throughout that ter ritory and the oil fields soon reduced the unsightly waste pile. Petroleum The petrolum industry recovers sulfuric acid from the acid operations of oil refineries and, by extraction, sulfonic acids from sludges resulting from such refining operations. The oil-soluble sulfonic acids are used as emulsifying and wetting agents. Naphthenic acids, recovered from certain crudes, are used for heavy metal soaps, for varnish and paint dryers, and in extreme pressure lubricating compounds. Several processes have been devised for the reclamation of used lubricating oil, although where all costs are considered there is a question as to whether this is always economical. In a broad sense a material used for a purpose that does not yield the highest return may be regarded as a waste. The Courtesy, Western Precipitation Corporation Acid Mist Cottrell Precipitatob NOVEMBER, 1939 INDUSTRIAL AND ENGINEERING CHEMISTRY 1327 paraffin hydrocarbon gases fall under such a heading, and the waste of natural gas, crude oil distillation gas, and cracked gas has been enormous. On the basis of 1939 production, it has been estimated that there are available in the United States 2500 billion cubic feet of natural gas, and 350 billion cubic feet each of crude oil distillation gas and cracked gas--a huge total of 3200 billion cubic feet. This is probably made up of 2531 billion cubic feet of methane, 36.35 billion of ethane, 159.5 billion of propane, and 96 billion of butane. Some butane is being dehydro genated into butylenes which, in turn, are polymerized into isooctenes and then hydro genated to isooctanes for aviation fuel. It may also be processed into butadiene, now of interest as a source of one type of synthetic rubberlike polymer. Flotation of Fine Phosphate Rock (Sands) Formerly Discarded as a Waste Product in the Separation of Phosphate Rock from Silica Sand at the American CyanAmid Company's Florida Phosphate Mines Though hydrocarbon gases have been liquefied and widely used as fuel at a profit over similar utilization in the refinery, only when and even though sulfur dioxide or sulfur in some other form they become raw materials for long lists of solvents and may be sold, it is not to be expected that an actual profit will other chemicals, such as those made by the Carbide and Carbon Chemicals Corporation, is their greatest value realized. be realized at present One must remember that the quantity of material from a single plant is often to be measured in hundreds of tons per day, and it is inconceivable that chemical Vistanex polybutene, a high-molecular-weight substance useful in rubber compounding, is one of the products made by the dehydrogenation of butane to butylene. Butylene is then polymerized, and the material is available in a range of giant molecules. The production of amyl alcohol from petane by the Sharpies Solvents Company is an achievement in this field. This com pany formerly stripped pentane from casing-head gasoline, markets will be able to absorb all of the sulfur which could be produced in this way. Here again public interest may require the cleansing of waste gases, but the products obtained may yet constitute an industrial waste without great possibility of complete commercial utilization. The Longyear process of Comstock and Westcott for the recovery of sulfur from smelter gases where sulfide ores are processed is planned for operation in Canada, and the poten without detriment to the gasoline as fuel, and chlorinated it tialities are put at 45,000 tons of sulfur annually. with gas from a neighboring electrolytic alkali works. The R. V. Kleinschmidt has given particular attention to re hydrolysis of the chloropentane was carried out with oell moval of objectionable materials in flue gases by a wet spray liquor, also obtained from the alkali plant without concentra or scrubber. He has found this effective not only in removing tion or purification. When the chloropentane had been sulfur dioxide but also dusts and fly ash which are often objec changed to alcohol, the cell liquor, in which the sodium hy tionable. droxide had been reconverted to chloride, was pumped back to The advent of hydrogenation has meant utilization for the electrolytic cells for another cycle of operation. This com much of the hydrogen which was formerly a waste of the pany continues to produce amyl compounds from the pentane electrolytic plants. The necessity of removing carbon mon of casing-head gasoline but now purchases the hydrocarbon. oxide from water gas to yield hydrogen for hydrogenation and Gases ammonia synthesis led to the synthesis of methanol. Dry Ice was originally produced from carbon dioxide manu The disposition or utilization of sulfur dioxide and trioxide factured for the purpose. Today at least 85 per cent of our has been a vexing problem. At Trail, British Columbia, the production is made of by-product carbon dioxide from fermen smelter has been required to reduce the sulfur content of its tation and other industrial processes. waste gases to a concentration not harmful to vegetation. At Ducktown, Tenn., and Anaconda, Mont., a similar problem Dusts has been faced. The various dusts precipitated by the Cottrell method also A favorite method of utilization where the sulfur content find a place in industry. The first installation of a Cottrell of the gases is high enough, has been the production of sulfuric precipitator, at Riverside, Calif., was made to prevent further acid. In some instances, however, this has made the sulfuric damage by cement dust to surrounding vegetation. As a acid a waste material, and there have been difficulties in its secondary and profitable effect a large amount of cement dust utilization or disposition. Acidulation of phosphate rock, in is collected which would otherwise be wasted. The recovery the manufacture of some form of phosphate for agriculture, of potash from the flues of cement plants was important has taken much of it. during the World War. In other instances dusts of a wide At Trail elemental sulfur is being obtained. Powell (16) variety are recovered either for their value or to prevent nui discusses several methods for the recovery of sulfur from fuel sances. One of the most difficult to handle--fly ash--presents gases, and the literature gives many references to similar a problem in disposal even after recovery. Attempts to activities in Germany where dependence for sulfur is now utilize it have included its use in artificial stone. At the placed almost wholly in what is recovered from smelter, coke Royal Mint of Canada, at Ottawa, a Cottrell precipitator was oven, or other gases. installed to recover various values from fumes. Within a H. F. Johnstone has done a great deal of work on the re comparatively short time the value of the recovered metal ex moval of sulfur dioxide, along with the dust which is also ob ceeded the original cost of the installation. Practically all the jectionable, from flue gases. As Johnstone pointed out, clean crude arsenic produced in the United States is recovered from ing waste gases is expensive regardless of the method used, lead and copper smelting and gold roasting. Indeed, new 1328 INDUSTRIAL AND ENGINEERING CHEMISTRY VOL. 31, NO. U uses or disposal methods are sorely needed because arsenic, recovered from waste, is becoming a waste. The clothing has long been supplied to workers in preciousmetal refining plants, and when worn out the garments are burned for their metal content. It has even been found eco nomical to filter the air from the refineries for the air-borne metal particles. The Cellite Company, in order to avoid a serious dust problem, removed and collected the fine particles of diatomaceous earth from the air in its factory. This product sub sequently found an outlet as a fine abrasive for silver polish, automobile polish, etc. The demand for the abrasive exceeded the supply, and so a plant had to be erected to produce, on a commercial scale, a product formerly regarded as a waste. Sewage In recent years we have seen a successful experiment in the treatment of city sewage at Milwaukee where the adjustment of pH of the tank effluent made possible the filtration of the material. This led to success in preparation of a fertilizer which has had wide distribution and splendid consumer ac ceptance. The result has been ability to handle a difficult city sewage at much lower cost or even a small profit to the com munity. In Germany sewage sludge is being utilized for the fertiliza tion of farm lands and sewer gas as a motor fuel is receiving increased attention. The Department of Commerce reports that Stuttgart has been particularly successful in recovering these waste materials. After several years of pioneering re search, the city has been able to recover considerable quanti ties of clarified sludge which has been taken by farmers for fertilizing purposes; some of it is transported considerable distances in tank cars. This amounted to 6000 cubic meters in 1936, 20,000 in 1937, and 22,000 in 1938. The recovered sewer gas in 1938 was approximately a million cubic meters for use as a motor fuel, estimated as equivalent to a million liters of gasoline. Agricultural Wastes We have become familiar with the many problems involved in the effort to use agricultural wastes, and much has already been accomplished. Some yeais ago Celotex, the wall board from bagasse, made its appearance, to be followed by many other boards from waste materials. Without attempting to name them all we can list Masonite from waste wood, Maftex from extracted licorice root, boards from cornstalks made by the Sweeney process, and several building boards and insulating blankets made by different units in the lumber industry. In the manufacture of Masonite panels and con struction boards from wood waste by ex ploding, the release of tannic, formic, and acetic acids gives the resulting pulp a pH of 4 or 4.5. Washing with a well water of high sodium carbonate and bicarbonate con tent, not suitable for boiler use, brings the resulting pulp to the desired pH of 6.5. In the manufacture of Celotex board from bagasse there are wastes which are used. The pith washed out of the fiber is collected and sold to explosives manufacturers, and the dust resulting from fabrication of the board is collected and sold to the plastics industry as molding flour. Cattle feed and casein are produced in con siderable quantities from surplus milk. The casein is used in the manufacture of paper coating, adhesives, paints, and plastics. A plant at Laurel, Miss., has been in operation for the past year or two and is producing, on a commercial scale, white starch from sweet potatoes. This provides a domestic source of a starch said to be suitable foT adhesives and tex tiles; it can compete with cassava, which is not grown in this country, and with tapioca, which must be imported. This promises to be the first in a series of similar new industrial enterprises. In the manufacture of starch from corn, the soluble corn solids from the tailing end of the gluten filter now go back into the process and these utilize a former waste. This process is described in the Widmer patent. Furfural and its several derivatives are well known. Origi nally research was directed toward the use of corncobs, but because large quantities of oat hulls were available in one place and were also suitable for furfural production, they, rather than corncobs, became the raw material. Prior to the production of furfural, oat hulls had been used as cattle feed and boiler fuel. Any pentosan-containing material is a potential source of furfural, and several attempts have been made to collect corncobs in sufficient quantities for its com mercial production. However, costs were too high and to date oat hulls remain the economic commercial source. Various estimates place annual consumption of furfural at about 6,000,000 pounds, made from about 10 per cent of the oat hulls available in the United States. The use of soybean meal in the manufacture of plastic parts, particularly for automobiles, is another instance of agricultural wastes becoming important as commercial raw materials. The shells which remain after cashew meats have been ex tracted from the nuts have been made the source of an oil which serves as a raw material for a superior insulating var nish. The oil is boiled with amyl chloride, and the resulting material is used in cable insulation. A polymerized product of the cashew shell oil is utilized in brake linings. Last year more than 3 million pounds of cashew shell oil were imported, and the number of products made from it is now extensive, ranging from cable insulation to liners for bottle caps. With the amyl chloride used in this process and obtained from pentane formerly wasted in casing-head gasoline, we have here a commercial product made on a large scale through utilization of two industrial wastes. By-products manufactured from citrus fruits, which be cause of size, shape, ripeness, or surplus were long regarded as a waste, is another of our classic examples. From lemons have come citric acid, lemon oil, and pectin; and from oranges we obtain juices, oil, marmalade, and pectins, with the pulp NOVEMBER, 1939 INDUSTRIAL AND ENGINEERING CHEMISTRY 1329 going into cattle feed. The avoidance of waste incident to shipping the whole orange great distances only to be juiced at the journey's end continues a subject of re search. Some canned or bottled orange juice acceptable to the market has been pro duced, but it may still be regarded as one of the problems of the industry. Lately the banana industry has conducted experiments with shredded banana stems, now a waste in producing countries because of the practice of packaging the fruit instead of distributing it in bunches as was the former custom. These shredded stems provided a satisfactory mulch which within a year dis integrates and supplies humus to the soil. Nicotine sulfate, so largely used in insecti cides, is produced from the waste parts of to bacco plants, particularly stems and the Courtesy* Dorr Company midribs of leaves. This material would otherwise be used only as a mulch. Thickener Recovering Fine Rubber Stock at the Rubber Reclaiming Plant of The Goodyear Tire & Rubber Company at Akron Beet molasses is a complex material, and from it there have been prepared methyl- amines, ammonium sulfate, sodium and potassium cyanide, In the wool industry recovery methods such as acid crack various potassium and sodium salts, and a variety of organic ing, solvent extraction, aeration processes, and centrifugal acids and esters. Molasses would represent considerable methods are practiced in removing lanolin from scouring waste were it not for the use of osmosis and the Steffens wastes. The grease may be distilled for its oleins and stearins process. The problem has not been completely solved be for use in the manufacture of soap or used as oils. There is cause the Steffens process gives rise to another waste, from some demand for it as a leather dressing, and refined lanolin some of which glutamic acid and betain are made in commer is valuable in cosmetics and certain pharmaceutical prepara cial quantities. The molasses is also used for yeast cultiva tions. Apparently the most convenient present method of tion, for cattle feed, and for alcohol manufacture. degreasing wool is solvent extraction with such solvents as Cotton linters may also be regarded as an industrial waste, naphtha or chlorinated hydrocarbons. After extraction the for prior to the World War there was no use for them. How solution is distilled and the grease recovered. A new method ever, when cellulose was badly needed for munitions, linters of freezing wool, urged by some, may eliminate much of the were recovered. This practice has continued although the waste of some processes, since at low temperatures from 30 to principal product is no longer munitions but cellulose acetate. 90 per cent of the original grease in the wool can be removed by From cottonseed, once a great waste, an immense number of beating before it goeB to a scouring bath. valuable products have been obtained; the latest is a sweep In the fishing industry there was formerly great waste inas ing compound from the hulls. The press cake from the manu much as the fillets represent only 40 per cent of the eviscerated facture of linseed, soybean, and cottonseed oils is used in cattle fish. The backbone, bead, skin, fins, etc., are now utilized feed. for the manufacture offish meal, glue, and other by-products. Miscellaneous Formerly this waste could not be merely thrown away but at considerable cost was transported to sea and dumped. In the days when the packing houses in Chicago discharged Today the bones and skin are cooked for several hours to glue, their wastes into Bubbly Creek, where they mixed with raw and the scrap is pressed and dried for use as feed or fertilizer. sewage and dilution water pumped from Lake Michigan, the The Koppers Company has developed a method for remov grease separated and rose to the surface when the waste met ing phenol from ammonia still wastes. After the free ammonia the cold lake water. Thrifty scavengers placed a raft near has been distilled and before the fixed ammonia is removed, the sewer and recovered the floating fats, making as much as the still waste is pumped to the top of a packed tower which a hundred dollars a day from this source. The packers soon is divided into two sections. The bottom section contains put a stop to their own wastefulness by installing grease jets which spray 10 per cent caustic solution through a rising collecting basins in the plants. Medicinal products are pro hot vapor, mostly steam. After passing through this spray duced from the glands and livers removed from slaughtered and being dephenolized, the vapor enters the top section of animals in the latest step toward complete use of packing the tower and meets the descending spray of fixed ammonia house wastes. Animal hoofs and horns are employed in the liquor. The vapor absorbs the phenols contained in the still manufacture of glue. liquor and is recirculated to the caustic spray section for de- Distillers' grains, the solids from distillation, have long been phenolization and another cycle. The ammonia liquors are used as stock feed, but only a few of the larger distilleries continually withdrawn, and the phenol is recovered from the practice complete recovery of their slops. Some of the wastes, caustic liquor. such as those from the yeast plant, are too dilute to justify The experience of Commercial Solvents Corporation is a recovery for feed purposes but cause serious pollution of matter of history. During the World War low-grade com was streams into which they may drain. Evaporation of thin used to produce acetone and ethanol by fermentation, the slop and the addition of the resulting sirup to the regular dis waste products being butyl alcohol, hydrogen, and carbon tillery grains has been found uneconomical; but where the dioxide Later the butyl alcohol was made into butyl acetate liquid is pretreated to permit multiple-effect evaporation to a for the first of the new lacquers and became the tail that high solid content, this recovery is made profitable. The wagged the dog. The carbon dioxide is now sold in the form method employed by Hiram Walker & Sons, Inc., which in of Dry Ice. More recently this same corporation has been volves the use of centrifugals, appears to be practical. active in the nitration of paraffins using natural gas as one 1330 industrial and engineering chemistry VOL. 31. NO. 11 of the basic raw materials. A new technique has produced a nitromethane, nitroethane, and similar compounds from which a variety of chemicals are being made. The nitroparaffins are direct and active solvents for nitrocellulose, for a wide range of synthetic and natural resins, for fats, and for some dyes. Some of the members of the new group show antigelling properties, an advantage useful in rubber cements; nitro ethane brings about such gelling in rubber latex. Spent soap from textile plants was formerly discharged into the sewer. Now oleic acid is obtained from the waste soap solutions by various recovery processes. Glycerol is a valued product from the manufacture of soap. Courte*y Western Precipitation Corporation Potash By-Product Recovery System at a Cement Plant; the Cottrell Is Preceded by Multictclonb Mechanical Collectors In the manufacture of chamois leather, the excess of par tially oxidized cod oil, drained and squeezed from the leather after the soaking period, is valuable commercially as an emulsifying oil. The oil now used in the chamois leather manufacture is largely a by-product of vitamin extraction operations. Coumarone resins are made from high-boiling coal-tar prod ucts which were formerly wasted. Millions of pounds of these resins are sold yearly for use in printing ink, as a binder for floor tile, and even as a constituent of chewing gum. Cinders are widely used with cement, as in cinder building blocks; and to the Rumford Chemical Company goes credit for perfecting a building block from waste calcium sulfate. The American Cyanamid Company uses its waste calcium sulfate, a by-product of phosphoric acid manufacture, for the manufacture of several types of gypsum building products and gypsum wall plaster. Waste brines of the West Coast have been made to give up their iodine content and thus enable the United States to be independent as regards a supply of this element. We must not overlook the extensive use of reclaimed ma terials known as junk. This reclamation is the basis for several large operations such as those of the Western Electric Company where the values handled annually approach 10, 000,000 dollars and require the services of some ninety to a hundred employees. To regain values with minimum loss and to rework the recovered materials into the form required calls for expert metallurgy. No. 1 scrap cast iron will yield about 96 per cent of new cast iron, stove plate 90 per cent usable new iron, and heavy milling steel scrap 95 per cent new steel. Zinc is recovered to the extent of 75 per cent of the stock charged, and many other metal products are recovered and re-used. Such used rubber tires as can be economically collected provide the raw material for rubber reclaiming plants, and some tire cuttings may reappear in the form of door mats and certain types of roofing materials. Conclusions One difficulty was ever present in the preparation of this paper--the determination of "waste". One generation of chemists spoke of the utilization of "waste cottonseed", "waste products from coke plants", and the wonderful utiliza tion of the waste gases from the Ducktown smelters for the manufacture of sulfuric acid. We may no longer consider the industries that have grown from such ventures as illustrations suitable for our topic. At one time they might have been but not now. The examples given here will some day be con sidered established practices and not extraordinary in any sense. So be it. It will mean only that chemists have ad vanced further toward an efficient utilization of wastes. It can mean only that there will be new problems in the utiliza tion of some product for which a use or a market has not yet been found. This is our definition of waste. Earlier in this review we referred to the British Alkali Act, the purpose of which was to abate a nuisance. In the begin ning it was a thorn in the flesh of the alkali manufacturers. Later it became a vital factor in building not only the British chemical but the British textile industry as well. In this country much has been accomplished without benefit of legal compulsion--for example, the rapid growth of syn thesis from waste petroleum gases; but much remains to be done with wastes, some of which cause actual nuisances. In eliminating them the force of law may lead to profitable exploitation and, although intended to lead to nuisance abate ment, may in fact help establish important industries. 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