Agricultural Uses of Coal and Its Products HERBERT G.GUY Koppers Company,
Pittsburgh, Penna.
More than 82,000,000 net tons of coal were carbonized in by-product ovens during 1941 in the United States. According to Ramsburg (I@, the modern oven carbonizes 26 tons of pulverized coal per day; in addition to 19 tons of coke, approximately 300,000 cubic feet of gas, 210 gallons of tar, 600
The close relationship of the cod-processing industry to agriculture is discussed. The consumption of products derived from the carbonization of coal, as well as derivatives of these primary products, has been estimated and is presented. The materials derived from coal have been found to be useful in agriculture as fertilizers, insecticides, disinfectants, herbicides, fungicides, fumigants, preservatives, plant-growth regulators, and food dyes.
HE close relationship of the coal processing industry to T agriculture is not generally realized. Few farmers know that many of the essential chemicals purchased by them for the growing of animals and plants are derived from coal. Conversely, the extent, importance, and complexity of the agricultural industry are not fully understood by those not vitally concerned with agriculture. It seems well to point out certain statistics that will emphasize the complexity of agriculture and the economic importance of this major industry. I n 1938 the total farm value of agricultural products was over $14,000,000,000 (Table I). This does not include forest products which many consider a part of agriculture. I n addition to livestock, poultry, and other animal products, there are over eighty different crops important enough to be considered separately in the annual statistics prepared by the United States Bureau of Agricultural Economics (90). Coal itself is not directly used in agriculture except as fuel. It is not the intention of the author to include those materials that indirectly influence agricultural production. It has been suggested that coal be added to the soil to absorb heat from the sun, or as a fertilizer and soil amendment. While coal might be valuable for such purposes, no record of any largescale consumption has been found. The Utah Agricultural Experiment Station has reported that the addition of coal to the soil does not benefit the growth of corn (11). Coal-has meliorative or catalytic effect when used with ammonia fertilizers but is of no value alone, according to Musierowicz (14) who worked with finely ground coal from Upper Silesia. Leached coal ashes are commonly used in greenhouse benches to improve soil drainage and to lighten soil. Ashes do not supply plant foods and must be used in combination with fertilizers (13).
Thylox
139
Gas
Purification Plant for Production of Agricultural Sulfur
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INDUSTRIAL AND ENGINEERING CHEMISTR Y
140
air, and water. The cleveloprnent of the by-product coke oven folloved by the development of synthetic ammonia, has peimitted the farmer to purchase for 40 cents today as much inorganic nitrogen as $1.00 rould buy 25 years ago. Amprica’s capacity to produce by-product and synthetic nitrogen has been increased 1300 per cent in the last 25 years and has made this country entirely independent of foreign sources for this vital plant food (Table 11). The use of inorganic nitrogen as a plant food has developed within the last hundred years Ammonium sulfate and chloride, TI hile early recognized as plant foods, were not generally available until the development of the by-product coke oven. The first by-product coke Four Late Type Saturators for the Production of Ammonium Sulfate ovens in this country TI ere built in 1893 for a t Syracuse, N. I!., the primary purposc of producing ammonia. Because of its high cost and other disadvantaies, ammonium chloride is not pounds of sulfate of ammonia, 75 gallons of light oil, and 120 commonly used as a fertilizer. Ammonium sulfate, however, pounds of recoverable sulfur plus additional miscellaneous remains the standard source of nitrogen for fertilizers in this products are produced. These products and inany. of their country because of its low cost per unit of available nitrogen derivatives are of agricultural value. It is difficult to draw a and has replaced Chilean nitrate to a considerable extent. line separating such synthetic produck into coal and noncoal derivatives. I n fact, certain of them can be produced either with or without involving any derivative of coal as a raw material. However, in order to simplify this report, it Table II. Wholesale Prices of a Unit (20 Pounds) of Nitrogen in seems advisable t o discuss the various products in the order in Fertilizer Materials (6) which they are usually separated in by-product plants. Ammonia
The most fundamental problem in agriculture is plant nutrition. Nitrogen is one of the essential elements necessary to the growth of plants and, consequently, to all life. Plants utilize nitrogen only in combined form, including ammonium, nitrite, nitrate, and organic compounds. The most important source of this element for commercial fertilizers is ammonia derived from the destructive distillation of coal or from coke,
Table
I.
Number and Value of Farm Products of Continental United States in 1938 No. of Different
Farm Producta Fruit crops Vegetables and truck crops Field crops Other crops An Total
Crops and Products 22
Total Acreage Harvested
21 36 4
4,757,240 394,052,700
...
... ...
S
Total Farm Value 475,829,000
282,443,000 4,4a097,000
6,373,000
6.366.865.000
Y8
Production Forest Product Saw timbera (1930) Lumber Pulpwood (consumption)
1,667,803 million Et. board measure 25,997 million ft. board measure 10,393,800 cords
’
a Includes only those products having an annual farm value of $150,000
or over. b
Acreage of 188,645,000: 54,642 million feet (board measure) cut.
Year
Sodium Kitrate
Ammonium Sulfate
Calcium Cyanamide
1910 1015 1820 1925 1930 1935 1939
$2.76 3.04 4 44 3 28 2.49 1 47 1.68
$2.64
$3.43 2.64 3.40 2.20 1.65
3.09 4.08 2.65 1.79 1.13 1 33
1.20
1.IG
As illustrated in Table 111, t’he consumption of fertilizers, including nitrogen-containing fertilizers, by farmers has increased steadily during the past tn-enty-five years, and even thosc in the black soil areas of the corn belt tire beginning to find it necessary t o addnit,rogen to the soil. The consumption of nitrogen in Rlirinesota ( Y ) , for example, has increased from 176 tons of available nitrogen in 1933 to 449 in 1940. I n the United States 8,310,853 tons of fert,ilizers were produced in 1940 ( 3 ) . The standard of lil-ing in backvard areas, such as India, could undoubtedly be raised if the people could be persuaded to use manufactured fertilizers. As repeat,edly deinonst~rateti, the increase in yield from the judicious use of inorgitnic fertilizers more than offsets the additional cost. The fear that the rorld would not be able to support, the increasing population, expressed in the early nineteenth century, has been overcome by the use of inorganic fertilizers. Although present conditions are causing a tight situation, there is no possibility of future shortage of nitrogen when it is realized that in 1938 synthetic nitrogen plants, on the average, operated a t about 53 per cent capacity. Before the present x a r and con-
.
February, 1943
-4
141
INDUSTRIAL AND ENGINEERING CHEMISTRY
sequent increased capacity, it was estimated that the annual world capacity for producing synthetic nitrogen, including cyanamides, was approximately 4,100,000 tons. I n an effort to save freight and other handling charges, the concentration of available plant food in mixed fertilizers has tended to increase, leading to the development of ammoniated superphosphates and similar materials. It is now estimated that over 70 per cent of the mixed fertilizers produced in this country contain ammoniated superphosphate. Ammoniated superphosphate is prepared by the treatment of superphosphate with ammonia liquor, anhydrous ammonia, or so-called nitrogen solutions containing ammonium nitrate or urea and ammonia liquor. The quantity of ammonia that can be added without serious formation of citrate-insoluble phosphate amounts to 3 per cent with ordinary superphosphate and 9 per cent with double superphosphate. Aside from the lower cost of the nitrogen, ammoniation greatly improves the mechanical conditJion of superphosphate and mixed fertilizers containing superphosphate. It reduces the
Table 111.
World Consumption of Pure Nitrogen ( 1 )
Product
1933
Ammonium sulfate Synthetic By-product Cyanamide Calcium nitrate Other forms of NP Synthetic By-product Chilean nitrste of soda Total
1934 1935 1936 1937 Thousand metric tons
1938
560 268 168 118
535 307 195 107
533 321 232 153
630 376 269 156
688 429 291 179
765 411 305 195
462
516 48
46
84
607 45 179
724
40
192
851 63 206
931 49 224
1677
1792
2070
2393
2697
2880
71
Includes nitrogen products used for industrial purposes except Chilean nitrate and ammonia in mixed fertilizers. 4
setting action when ammonium sulfate is used with superphosphate. I n 1937 the fertilizer industry consumed for this purpose 6000 short tons of anhydrous ammonia, 25,000 tons of 30 per cent ammonia B liquor, and 70,000 tons of ammoniated solutions of the fortified type (9). It has been known for some time that it is possible to ammoniate superphosphate or to produce ammonium phosphate by direct treatment with coke-oven gas. Certain manufacturing difficulties, however, have prevented the utilization of this procedure. Ammonium phosphate has been imported from Germany as the principal component of Nitrophoska. The total domestic consumption of this product amounted to 6500 short tons in 1937. Ammonia will combine with humic substances a t low temperatures in a form that is available for assimilation by plants. Ammoniated peats and brown coals have been investigated as fertilizers in Europe. These products have also been successfully treated with phosphoric acid. Peat as a soil corrective has been marketed on a small scale in this country (6). Although in the past ammonia liquors have been used only indirectly in this country for the fertilization of plants, promising results have been obtained in certain areas for their direct use. I n irrigated areas, ammonia liquor has been added to the irrigation waters with excellent results (I?'). The stimulation of plants from such treatment is very rapid. This new development is being watched with considerable interest by agricultural investigators. The large-volume low-cost production of urea has made this product available for fertilizer manufacture. This synthetic urea has also been found useful as a means of supplementing proteins in livestock feeds. Cyanogen
Modern Battery cf By-product Coke Ovens
The presence of hydrogen cyanide in cokeoven gas suggests that this valuable product can be utilized. As a step in this direction ammonium thiocyanate is being produced commercially on a large scale in this country from coke-oven gas. This compound has been suggested by agricultural investigators as a weed killer, potato wart eradicator, and seed disinfectant. It has also been mentioned as a means to speed the coloring of apples and to regulate the dormancy of plants. It is not being utilized for these purposes a t present. Ammo-
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142
nium thiocyanate also serves as a raw material in the production of complex organic thiocyanates useful as insecticides, These insecticides are utilized for the control of houseflies and other household insects, and are tending to make this country independent of foreign supplies of pyrethrum and rotenone. It is possible that sodium or calcium cyanide and hydrocyanic acid could be prepared from coke-oven gas. These materials are well known as fumigants to control insects and other pests in warehouses and similar establishments.
Table
Sulfur
The Thylox, Ferrox, and other methods of gas purification have produced finely divided sulfur, as an end product which is being successfully used for the control of insects and diseases in agriculture. Commonly known as flotation sulfur in the agricultural industry, it is sold either as a paste containing approximately 50 per cent water or in the dry form as either a dust or “dry-wettable” product. It has certain advantages over ground elemental sulfur-ultrafine particle size and great adhesiveness t o plant foliage. I n the removal of organic sulfurs from gas it is possible to produce dithiocarbamates. Certain salts of dithiocarbamic acid have recently been found promising as fungicides, seed treatments, and also as insect repellents (19). Through the use of the hot activation sulfur recovery process, hydrogen sulfide in coke-oven gas can be removed in a form readily convertible to sulfuric acid. This sulfuric acid can be used in agriculture for the preparation of superphosphates from phosphate rock, etc., and as a weed killer. Sulfuric acid has been used extensively as a selective weed killer for the elimination of weeds in grain and similar crops where cultivation is difficult. The importance of weeds is usually underestimated. I n a survey of this problem, the Chamber of Commerce (a) estimated that weeds tax the farmers for $3,000,000,000 annually. Light Oil The primary product, light oil, and its components are not extensively used in agricultural productions. Benzene, toluene, and xylene have been reported to be more toxic than carbon disulfide as fumigants (IS), but certain of their characteristics, such as residual odors, have prevented their widespread use for this purpose. The solvent naphthas, mesitylene, styrene, pseudocumene, and indene also have not been developed as agricultural chemicals. The estimated consumption of the primary products from coal carbonization is given in Table IV. Intermediates produced from light oil and naphthalene are used in agriculture either directly or combined with other
Table
IV.
Principal Primary Products Used in Agriculture
Product Naphthalene
Creosote
Use Insecticide (clothes moths, greenhouse insects, cattle lice, etc.) Wood preservative Rope preservative
Ann. Vol. in U. S. Year Reference 16,500,000 1940 (16‘) lb. 174,625,305 1940 gal. 500,000 1940
(8)
gal. 2,000,000
1940 gal. Insecticide (chinch 3,500,000 1934 gal. bus) No reports Wood preservative Small Disinfectants Large No re orts Cattle & sheep dips Listed with industria? disinfectants Fertilizer 753,216 tons 1937 (BO) Fungicide, insecticide 8,600 ton3 1940 a Weed killer
.. .
Anthracene oil Tar acid oil Cres lic acid, creso$, phenol Ammonium sulfate Sulfur (flotation)
intermediates or other chemicals. Such products are particularly useful as pest control agents. Insects, fungi, weeds, and others of the lower forms of life are considered pests. It is estimated that agricultural production is reduced a t least 10 per cent by their destructive action. The estimated consumption of these secondary derivatives of coal carbonization is given in Table V.
0 Writer’s estimate from discussions with individuals closely associated with the industry.
V.
Important Secondary Products Used in Agriculture Ann. Vol. Product Use in U.S., Lb. Year Referenoe g-Dichlorobenzene Fumigant (insecticide 5,000,000 1935 (I6 ) o-Dichlorobenzene Benioic acid, benzoates Organic thiocyanates Chlorophenols
Dinitrophenol -Nitrophenol binitro -a-cresol Dinitrocyclohexylhenol (DN) aphthol
a-8
Diphenylamine Phenothiazine n-Naphthalene acctic acid Sulfonates4
and fungicide) Soil poison (termites). wood preservative Food preservatives
700,000
1940
a
281,202
1940
b
Insecticides
800,000
1939
0
8,150,000 6,000,000 850,000 400,000 100,000 200,000 600,O00 200,000 200,000 50,000 250,000 260,000
1940
a
1940 1940 1940 1940 1940
140,000 100,000
1940 1940
Traces 150,000 2,500,000 1.000
1942 1942 1941
800,000
1940
Disinfectants preservatives (tbtal) Wood Wallboard Fabrics Latex Paints Proteinaceous Preservative Preservative Insecticide Weed killer Insecticide Soil poison Wood preservative Proteinaceous Insecticide Insecticide Anthelmintic Plant arowth reszulator Wetting agents for sprays and dusts ~
300,000
.... ..
5
a Estimate of the writer and numerous individuals closely associated with the insecticide and fungicide industry, including those in state and federal agencies. b Estimated b y the writer from reports of WPB allocations in Oil. Paint and Drug Reporter. 0 No information found on volume; represents an approximation by the writer. d Other than those from phenols and naphthalene.
At this point i t seems well to mention coal-tar food dyes. While produced in small quantities, these dyes are the most important food coloring materials. Through the use of these uniform, dependable, and safe dyes, farmers have been able to make their products more attractive to the consumer who frequently makes selections on the basis of appearance alone. The Food and Drug Administration reports that 454,254 pounds of coal-tar food dyes were certified during the year ending June 30, 1939. It is estimated that approximately 420,000 gallons of benzene were used in 1940 for the production of o-dichlorobenzene. o-Dichlorobenzenehas been widely recommended as a soil poison to control subterranean termites and as a brushon treatment for wood infested with termites and other wood borers. The production of p-dichlorobenzene consumed over 1,000,000 gallons of benzene the same year. This compound has been widely adopted as a control for clothes moths and other household insects, and has replaced naphthalene to some extent for this purpose. p-Dichlorobenzene is the standard remedy for peach-tree borers and can also be used to control blue mold in tobacco seedbeds. Diphenylamine and phenothiazine have recently been discovered to be extremely useful for certain parasites of animals. Diphenylamine is now the standard remedy recommended by the United States Department of Agriculture for the control of screwworm, a serious pest of cattle in the southern states. Phenothiazine, discovered to be useful by workers of the Department of Agriculture for the removal of internal parasites of animals, is being received enthusiastically by farmers.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February, 1943
143
According to Jardine (IO), this new anthelmintic is expected t o become one of the farmer’s most important chemical aids. Creosote
I n 1940, 265,473,149 cubic feet of wood were treated with wood preservers (8). The most important one in volume is coal-tar creosote. The direct relationship of wood preservation to agriculture is not generally realized. Through the use of pressure-treated wood, farmers can reduce their overhead to a considerable extent through longer life of fence posts, farm buildings, etc. Well-built corn cribs, silos, and hay storage sheds effect better curing of farm crops and, by preserving their quality, help reduce feeding expenses. Wood preservers now offer treated lumber, precut and ready for assembly, for the following farm buildings: hog houses, dairy barns, corncribs, granaries, silos, vegetable and fruit bins, and manure pits. Creosote is also used as a stock dip for the extermination of lice and ticks, and in poultry houses as a general disinfectant. To control poultry mites, attention must be given t o the house rather than to the bird, and excellent control may be obtained by treating the roost and interior of the poultry house with creosote. This product, usually diluted with petroleum oil, is a n excellent weed killer. Creosote is also used as an insect barrier to prevent the spread of such pests as chinch bug. Chinch bug outbreaks occurred at irregular intervals, but in 1934, 3,500,000 gallons of creosote were used to control this pest. Naphthalene
Naphthalene is an important by-product from coal carbonization. Over 16,000,000 pounds are used annually for agricultural purposes. The control of clothes moths is considered an agricultural problem since the products of the farm as well as the household goods of the farmer need to be protected from its ravages. Approximately 10,000,000 pounds of naphthalene are used annually to control clothes moth apd carpet beetle. Both naphthalene and p-dichlorobenzene will kill these pests when applied to clothing in airtight containers. Many people use these products without taking precautions to make their clothes closets airtight. Keither of these materials will kill the pests unless a sufficient atmospheric concentration is reached, and they do not act as repellents. The Department of Agriculture recommends that 1 pound of naphthalene be used per 10 cubic feet of space. However, Coleman (4) found that less than lethal concentrations will greatly retard the feeding of these insects. Applications of naphthalene in open closets will give protection against clothes moths but will not wipe out the infestation present. Naphthalene is utilized to control greenhouse pests (such as red spiders, thrips, and white flies) by fumigation, as a dry dip for cattle and hogs to control lice, for the preservation of hides in storage, and as a soil treatment to control such pests as carrot rust fly. Back-yard gardeners have found naphthalene moth balls to be useful as repellents for rabbits. The moth balls are scattered around the plants to be protected, but are not allowed to come in direct contact with the plants. Naphthalene and other coal-tar products serve as raw materials for the production of sulfonates. These sulfonates
Modern Light
Oil Recovery
Plant
are used as wetting agents in the preparation of agricultural sprays and as detergents for the washing of agricultural products before marketing. &Naphthol is a wood preservative, disinfectant, and soil poison for the control of termites. Cardboard bands, impregnated with &naphthol, are used in apple orchards for trapping codling moth larvae. A recent development in agriculture that offers considerable promise is the discovery of synthetic plant hormones. These growth regulators have been found useful in the production of fruit without fertilization, for the development of roots on cuttings, and for the prevention of premature dropping of fruit. The better known of these synthetic hormones are a-naphthalene acetic acid, indole butyric acid, phenyl acetic acid, and P-naphthoxy acetic acid. It is interesting to note that all the effective materials discovered to date have an aromatic nucleus. Farming in the future may become more of a science and less of an art through the development of synthetic plant growth regulators. Tar Acids
Tar acid oil and cresylic acid, either alone or in combination with petroleum oils to make dormant sprays for the control of overwintering aphids and other insects on fruit trees, have been largely replaced with dinitro-o-cresol and dinitrocyclohexylphenol. These nitrated phenols are also used for the control of red spiders in citrus trees and certain greenhouse crops. Dinitro-o-cresol is an extremely powerful contact insecticide but must be used with caution due to its tendency to injure foliage. Advantage has been taken of the phytocidal properties of this compound to develop a selective herbicide for the control of weeds in grain and other crops. Its selective action is believed to be due to differential wetting of foliage. Tar acid oils, cresylic acid, xylenol, cresols, and phenols are well known as disinfectants. Phenol was suggested as a bactericidal agent by Lister in 1865, and is now the standard for all disinfectants. The phenol coefficient of the disinfectants
144
INDUSTRIAL AND ENGINEERING CHEMISTRY
marketed today represents the relative effectiveness to phenol in killing Staphylococcus aureus and Bacillus typhosus. The volume of disinfectants consumed on the farm is substantial. Dairy farmers and poultrymen especially have learned the value of farm sanitation.
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Tar Bases
The heterocyclic nitrogen compounds obtained from coal tar have been investigated as insecticides and fungicides. Pyridine has considerable insecticidal action, and attempts have been made to produce synthetic nicotine from this product without commercial success. Quinoline has been reported to be an excellent ovicide. Substituted quinolines, such as 8-hydroxy-quinoline, are good fungicides. The agricultural consumption of these tar bases and their substituted products, however, is small. The tendency of farmers to fortify their feeds with vitamins may result in the larger consumption of tar bases for agricultural purposes. A large volume outlet for lovcost vitamins exists in the agricultural field. Hydrocarbons
Anthracene, phcnanthrene, carbazole, methylnaphthalenes, acenaphthene, diphenylene oxide, and fluorene have also been investigated by agricultural workers. These products are known to have insecticidal and fungicidal action, but as yet little effort has been made to utilize them. Anthracene oil has been recommended as a wood preservative but has not been accepted generally in this country for the purpose. These materials will, without doubt, eventually be used for agricultural purposes. Organic chemicals have been found to be very specific in their action as insecticides and fungicides. There are a number of possibilities not yet investigated for these compounds The agricultural consumption of organic compounds, particularly as insecticides, fungicides, plant growth stimulants, and preservatives, should increase in future years. There are over 450,000 knonm species of insects and several hundred thousand species of plants. Each species is more or less separate from all ot'hers in structure and metabolism. The usefulness of any given compound can be determined only by actual test; and while considerable knowledge has been accumulated on the relation of chemical structure to toxicity, etc., biological investigations must still be conducted by trial and error methods. An increased consumption of organic chemicals should result in an increased consumption of coal derivatives, since these materials can serve both as final products and raw materials in the manufacture of new agricultural chemicals. Coke Being Pushed from a By-Product Oven into a Hot Car
The development of chlorinated phenols in the last twenty years as disinfectants, wood and fabric preservatives, sap stain controls, etc., has been phenomenal. Most of these products are prepared from synthetic phenol, and 8,000,000 gallons of benzene were used in 1940 for the production of synthet'ic phenol. The development of chlorinated phenols as fungicides and bactericides was initiated by the discovery that the toxicity of phenol increased as the number of chlorine atoms was increased. Suter (18) reported t'hat the introduction of a halogen into the nucleus of a phenolic compound increases its bactericidal potency, without exception. As was to be expected, pentachlorophenol is the most toxic to fungi, but certain of its physical properties and industrial requirements have made i t necessary to use other products such as 2-chloroo-phenyl phenolate. A wide variety of chloro- and nitrophenolic compounds are now o n the market in order to fill the specific requirements of various industrial and agricultural needs.
Literature Cited Brit. Snlfate of A m m o n i a Federation, A n n . R e p t . , 1938. C h a m b e r of Commerce of U . S.A , , Agr. Service D e p t . C o m m . , 1930. Chem. Eng. A7ews, 20,332 ( M a r c h 10, 1942). Coleman, Wallace, J. Econ. Entomol., 33,816-17 (1940). Dachnowski-Stokes, A. P., U. 9. D e p t . Agr., Circ.290 (1933). Fletcher, C.C., M e r z , A . R., a n d Brown, B. E., I b i d . , 578 (1940). H a l v o r s o n , H.d.,M i n n e s o t a Fertilizer Analyses a n d Registration, 1940. H e l p h e n s t i n e , R . K., Proc. Chem. Wood Preseming Assoc., 37, 410-39 (1941). J a c o b , K. D . , Western P h o s p h a t e Conf., 1940. Jardino, J . T., Agr. Leaders' Digest, 1942. Jardine, J. T.. Froinine, F. D., aiid K n i g h t , H. L., U. 9. D e p t . Agr., R e p t . A g r . E@. Sta., 1940,14. J o h n s o n , R. C . , T r a n s . Bnd Ann. Anthracite Conf. (Lehigh U n i v . ) , 1939, 131-53. Moore, TTilliam, J . Agr. Research, 9, 371 (1917). Polish A g r . Forest Ann., 45, 125 (1938). Musierowicr, h., R a m s b u r g , C. J., Chem. Industries, 43,136 (1938). K o a r k , R . C., I b i d . , 42, 636 (1938). Rosenstein, Ludwig, U. S.P a t e n t 2,038,316 (1 936). S u t e r , C. M., Chem. Rev.,28,269 (1941). Tisdale, W. H . , a n d Flenner, A. L., ISD. ENG.C H E M . ,34, 501 (1942). U. S.D e p t . of A g r . , Agricultural Statistics, 1939.
