By-products of Sugar Manufacture.
Reading edition
By Cleve. W. Hines, M. S., Station Superintendent.
In various lines of manufacturing there are certain by-products which, years ago, constituted a waste and great loss, but which now under modern methods have become in many cases of considerable importance.
This is especially true with the sugar industry. Extreme care and attention is required to keep the balance on the right side of the ledger, and often the proper handling of the by-products forms the deciding factor between success and failure. In order to build up a great sugar industry in these Islands, more attention must be given to the details of the work, and many of the present losses must be turned into profits before great progress can be expected.
Cane Tops and Trash.
First in the series of by-products in the manufacture of sugar, comes cane tops. The amount of this material produced per hectare will depend upon various factors, including the variety of cane, its stage of maturity, etc. The less of these tops, of course, that may be produced for a given amount of cane, the better it will be for the growers, nevertheless they have a good feeding value if properly handled.
Per cent.
Protein 1.53
Fat 0.41
Carbohydrate 15.62
Fiber 8.87
Water 71.50
Ash 2.07
The fiber content would be slightly higher and the water content lower, for tropical cane, since maturity is completely reached before harvest begins. It may be seen from the above analyses that this makes a most excellent feed for work animals. Certainly greater advantage should be taken of this feeding stuff than is usually done, since there is a scarcity of pasturage near the end of the harvest season and the animals become needlessly thin on account of lack of feed. At present very little of this material is utilized, but instead is burned on the field with the rest of the trash. If the tops are removed and used as a stock feed, only the leaves and pieces of stalk remain, and these make a good fertilizer for cane lands.
It is the general custom in these Islands to burn all of this material as soon as the crop is harvested. The object of this burning is to destroy any insects that may be present, as well as to facilitate subsequent cultivation. In the writer’s opinion neither of these reasons is sufficiently well based, since in this country large numbers of troublesome cane insects are not found. If they were present in sufficient quantities, the trouble could be handled by placing the trash between the rows and properly treating it before plowing it under. This should be the method of disposing of the trash at all times. In this manner the waste material could be utilized, and the organic matter would be even more valuable than that contained in many of the commercial fertilizers. The nitrogen contained, which amounts to from 0.5 to 2 per cent, would be practically all saved, while with the burning method this is completely lost.
Use of Ashes.
The ash of sugar cane constitutes the mineral matter that has been taken out of the soil. This usually runs about 0.48 per cent of the total weight, according to Payson’s classical analyses. Chemically this contains the following: silica, iron, aluminum, lime, magnesia, potash, sodium, phosphorus, sulphur, chlorine, oxygen, water, etc. Of these various elements, the phosphorus and potash are the most valuable to the planter. Lime is also useful for many soils in correcting the acidity, and occasionally in supplying that element, when it happens to be lacking in a particular soil.
The cost of different fertilizers is governed by the percentage of these plant-food elements contained. Phosphoric acid is worth $0.05 per pound (₱0.22 per kilo) in crude fertilizers. At this rate the value of this element recovered from a crop of 75 tons of cane per hectare would be from ₱10 to ₱12.
Potash is valued at about ₱0.26 per kilo and that removed with a crop of 75 tons would cost about ₱25. The lime contained is a cheaper element but will not act as a detriment on any soil, while on many it will be found very helpful.
In spite of the great deficiency in these elements in the cane lands here, and the high cost of commercial fertilizers, this waste material is not only neglected at the majority of the factories but is actually thrown away, yet the same elements that command a high price in commercial fertilizers are contained in these ashes.
Filter-press Refuse.
In the defecation of cane juice, certain chemicals are often used to precipitate the impurities, which are removed from the subsiders after the clear juice has been drawn off, and sent to the filter presses, where it is filtered through heavy cloths. This material contains coarse particles of bagasse together with other impurities including the lime and phosphoric acid which were used in this work. The composition of the material depends upon the original composition of the juice and the amount of the different chemicals that has been used in the clarification. In any event, it makes a most valuable fertilizer because of the organic matter, nitrogenous bodies, phosphoric acid, and lime that it contains. This organic material is an ideal substance to be applied to the worn-out cane lands (which consist almost entirely of mineral substances) since it induces bacterial action, and during its decomposition certain acids are freed, such as carbonic, nitric, and organic acids. These have the power to act upon the mineral constituents and thus liberate other plant-food elements. The filter-press mud can very well be mixed with the bagasse ashes, and scattered about the cane rows as an almost complete fertilizer for sugar cane, the only element lacking being nitrogen, which was lost in the burning of the bagasse.
It will be remembered that in the synthesis of sucrose, which consists of carbon, hydrogen, and oxygen, there are none of the plant-food elements used which are sought for in commercial fertilizers. These are used only in building the fibrous stalk of the cane and they may all be recovered in the bagasse and cane-juice impurities. The carbon, hydrogen, and oxygen which are used practically all come from the air and water.
It is a custom to-day to cart this ash to piles or depressions some distance from the factory. In some places it is thrown into the river, or cast into the sea—an absolute loss.
Planters must not depend upon commercial fertilizers for their supply of plant-food material, when there is such an abundance of natural fertilizer being wasted. The cost of the artificial fertilizers in many cases is considered prohibitive and often unnecessary. In order to build up a great sugar industry here, the material at hand must be used, while money should be spent for modern apparatus and equipment.
Molasses.
The dark-colored viscous substance remaining after the large crystals of sucrose have been removed is called molasses. This contains small crystals of sucrose, which has passed through the perforations of the centrifugal screens, sucrose in solution, glucose, fructose, and other organic substances, such as pectin bodies, albumenoids, coloring substances, etc., besides the inorganic matter constituting the ash upon incineration of the molasses.
The composition of the molasses varies with the working of each factory, also with the condition of cane, time of harvest, etc. The juice from green cane and that which has reached ultramaturity will contain a higher percentage of invert sugar and organic non-sugars than a properly matured cane. Then factories that have ample boiling-house provision, and crystallizers as well as magma tanks, will be able to send out a molasses with lower purity, thus recovering more of the crystallizable sugar.
In any case there will be some molasses produced, and this constitutes a valuable sugar-house by-product, if properly cared for. It may be disposed of in one of several forms, namely, as a human food, a stock feed, a source of alcohol, factory fuel, and a fertilizer.
Cane molasses as a human food.—For many years low-grade cane molasses has been used as a human food in the United States. It was originally sold under the name of New Orleans molasses, but in recent years a number of companies have employed clarifying and bleaching agents and thus turned out a very fancy article, under various trade names, for baking purposes. With the boiling at low temperatures practiced to-day, there is little or no caramel formed during this work, and consequently it is only necessary to clarify and bleach the organic non-sugars, in order to make a salable molasses. The bleaching is usually accomplished by the use of a hydrosulphite, either in the form of sodium or calcium, but sometimes only the sulphurous acid gas is used.
The bleaching effect of none of these reagents is permanent, especially when the product is exposed to the air and light. Such chemicals must therefore be used with great caution, and as late in the process as possible. Care must be exercised too that an excessive amount is not employed, since an undesirable tint is liable to result as well as an excessive amount of the sulphites to be admitted, which is not permitted by the Pure-Food Law. It is astonishing how much of this low-grade molasses is thus manufactured and used in the United States for cooking purposes, and what a high price this product commands.
Cane molasses as a stock feed.—Perhaps more of the exhausted molasses is used for this purpose in these Islands than for any other.
Ordinary molasses contains from 30 to 35 per cent of sucrose and almost as much glucose. These being purely carbohydrates, it is necessary to combine them with some protein-bearing feed in order to make a perfect ration. Many leguminous plants, such as alfalfa, cowpeas, peanut vines, etc., may be cut fine and used as an absorbent for molasses. This makes a most excellent feed as it contains a sufficient amount of roughage, and at the same time offers a balanced ration if properly composed. In this country there is a great amount of exhausted cake from the coconut-oil factories, which is exported to Europe each year. There is no good reason why this should not be used as an absorbent for the molasses in making a concentrated feed, which could be transported to various parts of the Islands or exported abroad for stock.
To-day the Philippines are dependent upon Australia and other countries for many thousand head of cattle each year. The by-products from sugar factories are thrown into the rivers or flushed away from the factories through drains, and the leaves and tops of the cane are burned on the ground in order to facilitate cultivation. In the attempt to grow our own beef, these feeds should be an important factor.
Cane molasses as a source of alcohol.—Alcohol can be made from a great variety of substances containing the necessary constituents, viz, carbon, hydrogen, and oxygen.
Of the numerous alcohols possible, ethyl alcohol is the one ordinarily sought and the easiest produced. This alcohol is represented by the following chemical formula: C2H5-OH.
While glucose is the substance which may be easily transferred into alcohol by fermentation, sucrose may also be used, providing it is first changed into glucose or invert sugar. Even cellulose and starch may be used after being transferred into reducing sugars.
The process of changing glucose into alcohol and carbon dioxide is called fermentation and is accomplished by a minute organism. Sucrose will not directly ferment, consequently it must first be changed into glucose. This is usually accomplished by an enzyme which is secreted by a ferment.
The following chemical formula will serve to show the steps necessary to pass from sugar to an alcohol:
C12H22O11 (sucrose) + H2O (water) Presence of an 342 M. W.
enzyme → Invert sugar
————————————————————
(C6H12O6 (dextrose) C6H12O6 (levulose))
180 M. W. 180 M. W.
→ C2H5-OH (ethyl alcohol) + 4CO2 (carbon dioxide)
184 (2 M. W.) 176 CM. W.
The theoretical yield then of alcohol from sucrose would be 53 per cent and from invert sugar 51 per cent. In practice, however, this yield would not be experienced on account of the yeast converting some of the sugars into substances other than alcohol and carbon dioxide. These will consist mostly of glycerine and succinic acid and will amount to 4 or 5 per cent.
Since the working conditions determine to a very great extent the yield of alcohol, it is obvious that a thoroughly efficient person should be in charge of this work. In the selecting of cultures for the fermenting, the manufacturer should use only the purest, otherwise acetic acid and other foreign substances will be formed during fermentation, thus decreasing the yield of the alcohol as well as lowering its purity.
Where the percentage of sucrose and glucose of a molasses is known, it is a simple matter to calculate the theoretical amount of alcohol to be recovered and by knowing the efficiency of the factory, a factor may be obtained which multiplied by the theoretical yield will give the true amount of alcohol to be expected. In this manner it is easy to determine the price that may be paid for any molasses.
The separation of the alcohol from the water and dirt (lees) is accomplished in an apparatus termed a “still.” In this the liquor is heated by steam which causes the alcohol to evaporate. Since ethyl alcohol boils at a temperature of 78° or a little higher, depending upon the percentage present, it may be separated from the water and impurities during the evaporation, and recovered from the coils of the condenser in a fairly pure state.
There is always, however, more or less water vapor escaping with the alcohol and consequently it is impossible to secure absolute alcohol without after-treatment, although in the modern still a very high grade is often recovered in the first distillation.
In this connection the strength of alcohol is usually determined by referring it to “proof,” which is an old English system used before modern methods of testing spirits were available. In its original application, gunpowder was moistened with the spirit and the mixture subjected to the flame of a match. When just enough alcohol was present to set fire to the powder, it was said to be “proof spirit.” If not enough alcohol was present to accomplish this, it was said to be “under proof,” and when the gunpowder was lighted easily by it, it was said to be “over proof.”
By an act of the English Parliament, the term “proof spirit” was fixed as one which contains exactly 12/13 of an equal volume of water (distilled) at 51° F., which represents 57.1 per cent of alcohol by volume, or 49.3 per cent by weight.
The simplest method of determining the percentage of alcohol is by the use of a gravity spindle for liquids lighter than water, and by referring to the accompanying table for this purpose, the percentage of alcohol may be ascertained.
Volume. Specific gravity at— Volume. Specific gravity at— Volume. Specific gravity at— Volume. Specific gravity at—
15.56° 25° 15.56° 25° 15.56° 25° 15.56° 25°
15.56 15.56 15.56 15.56 15.56 15.56 15.56 15.56
P. ct. P. ct. P. ct. P. ct.
1 0.9985 0.9970 26 0.9698 0.9655 51 0.9323 0.9246 76 0.8745 0.8665
2 .9970 .9953 27 .9691 .9646 52 .9303 .9225 77 .8721 .8641
3 .9956 .9938 28 .9678 .9631 53 .9283 .9205 78 .8696 .8616
4 .9942 .9922 29 .9665 .9617 54 .9262 .9184 79 .8664 .8583
5 .9930 .9909 30 .9652 .9603 55 .9242 .9164 80 .8639 .8558
6 .9914 .9893 31 .9643 .9594 56 .9221 .9143 81 .8611 .8530
7 .9898 .9876 32 .9631 .9582 57 .9200 .9122 82 .8581 .8500
8 .9890 .9868 33 .9618 .9567 58 .9178 .9100 83 .8557 .8476
9 .9878 .9855 34 .9609 .9556 59 .9160 .9081 84 .8526 .8444
10 .9869 .9846 35 .9593 .9538 60 .9135 .9056 85 .8496 .8414
11 .9855 .9831 36 .9578 .9521 61 .9113 .9034 86 .8466 .8384
12 .9841 .9815 37 .9565 .9507 62 .9090 .9011 87 .8434 .8352
13 .9828 .9801 38 .9550 .9489 63 .9069 .8989 88 .8408 .8326
14 .9821 .9793 39 .9535 .9473 64 .9047 .8969 89 .8373 .8291
15 .9815 .9787 40 .9519 .9456 65 .9025 .8947 90 .8340 .8258
16 .9802 .9773 41 .9503 .9438 66 .9001 .8923 91 .8305 .8223
17 .9789 .9759 42 .9490 .9424 67 .8973 .8895 92 .8272 .8191
18 .9778 .9746 43 .9470 .9402 68 .8949 .8870 93 .8237 .8156
19 .9766 .9733 44 .9452 .9382 69 .8925 .8846 94 .8199 .8118
20 .9760 .9726 45 .9434 .9363 70 .8900 .8821 95 .8164 .8083
21 .9753 .9719 46 .9416 .9343 71 .8875 .8796 96 .8125 .8044
22 .9741 .9706 47 .9396 .9323 72 .8850 .8771 97 .8084 .8003
23 .9728 .9692 48 .9381 .9307 73 .8825 .8746 98 .8041 .7960
24 .9716 .9678 49 .9362 .9288 74 .8799 .8719 99 .7995 .7914
25 .9709 .9668 50 .9343 .9267 75 .8769 .8689 100 .7964 .7865
Molasses as a fuel.—Many experiments have been made, using this substance as a sugar-house fuel, and while ordinarily it may be better employed in some other manner, at the same time where no other provision is made for the use of this material, and where there is a scarcity of fuel as well, satisfactory results may be secured in its combustion if it is properly handled.
Waste molasses consists mainly of gums, sucrose, glucose, albuminoids, other organic compounds, water, and a small amount of ash.
Sucrose has the chemical formula of carbon 12 (atoms), hydrogen 22 (atoms), and oxygen 11 (atoms). The burning of carbon consists in uniting oxygen to that element, forming carbon dioxide. When hydrogen burns, the oxygen combines with it, forming water. During this oxidation, two atoms of hydrogen combine with one of oxygen, but in the molecule of sugar, these two elements are already present in this proportion, consequently only the carbon may be oxidized and thus give off heat. This is found to be true also of sucrose, reducing sugars, and many organic compounds.
An instrument called a calorimeter is used to determine the amount of heat a substance will give off upon oxidation. Tests may be made on molasses in order to determine its value as a fuel, and thus a comparison may be obtained of a pound of this material and one of coal having a standard value.
The ash from the molasses contains a great deal of potassium and some magnesium, consequently care must be exercised in the burning of the molasses so that this material does not come in direct contact with the tubes of the boiler, since a heavy coating will be formed that will greatly lower the coefficient of heat transmission.
On account of the high potash content, these ashes make a valuable fertilizer, which should be mixed with the bagasse ashes and mud cake, and applied to the cane lands.
Molasses as a fertilizer.—While molasses is not used to any great extent as a fertilizer, there is no good reason why exhaustive experiments should not be carried out with this by-product on Philippine soils, when it is now being thrown into drains or wasted, until a better use is provided for the molasses.
Experiments have been made in Hawaii, Mauritius, and other places with this form of fertilizer, and very encouraging results were reported. The plant-food elements themselves contained in molasses are small in amount, since they are contained in the low percentage of ash after burning, except, of course, nitrogen, which will be entirely saved. Its main value, however, lies in the power to induce bacterial growth, which is so necessary in worn-out soils.
Among the organisms induced by these organic matters may be included certain azotobacter species, which contrary to other forms of plant life, have the power of using nitrogen from the air. Carbohydrates form especially good mediums for their development, and it has been found that the activities of these organisms are increased by an increased amount of this substance.
While excellent results have been attained by the use of low-grade molasses for fertilizer in other countries yet it remains for the planters here to determine results under Philippine conditions, and the best method of handling their material. In some places where irrigation water is applied, the molasses is mixed with the water and applied in the usual manner.
The plant-food material contained in molasses will vary somewhat with the methods of its production, clarifying agents previously used, etc.
1 2 3 4
Mill sulphitation. Diffusion sulphitation. Open kettle. Carbonitation.
Per cent. Per cent. Per cent. Per cent.
Potash 49.48 52.20 51.48 50.16
Soda .89 .80 1.11 .32
Lime 6.47 6.78 6.58 8.53
Magnesia 4.29 3.09 3.99 2.66
Iron oxide .35 .33 .15 .47
Alumina .30 .22 .13 .30
Silica 4.12 4.59 2.83 4.10
Phosphoric acid 3.71 3.80 2.12 .91
Sulphuric acid 10.79 6.72 10.94 11.18
Carbonic acid 7.49 11.19 13.06 15.78
Chlorine 14.00 11.95 9.10 4.59
——— ——— ——— ———
101.89 101.67 101.49 99.00
Deduct O minus Cl. 3.16 2.70 2.05 1.04
——— ——— ——— ———
98.73 98.97 99.44 97.96
——— ——— ——— ———
Undetermined (carbon, etc.) 1.27 1.03 0.56 2.04
Alkalinity (cc. tenth normal per gram ash) cc. 80 93 95 109
In order to make a wise selection of the method of handling the different by-products the manufacturer must take into consideration many factors. Among them will be the quantity of his output, the facilities for handling it in any specified manner, the demand for different finished products to be made therefrom, etc. All of these and many other points must receive due consideration by a manager who expects to attain success in his work.