The tallow yield was 21,638 lb., or 20 per cent. of the total volume passed through the digester. Pronounced quantities of the fibrine and bone-meal were also secured. But the tallow yield alone should serve to convince even the most sceptical that it pays to submit condemned meat and slaughter-house refuse to a process of by-product recovery. It was not so many years ago that such valuable waste met with an untimely end—incineration in the destructor as the most effective and economical means for its disposal. Had this practice been followed in the instance under review the authorities would have allowed material worth, according to current market quotations, at least £500—$2,500—to vanish up the chimney in preference to the display of a little exertion and knowledge to secure what is in such wide and urgent request—the fat.
While the average organization, either municipal or private, conducts operations upon too limited a scale to deal with the gelatinous or “stick liquor,” the large establishments, on the other hand, are confronted with such immense quantities thereof as to render its further treatment justifiable and profitable. But the liquid is extremely thin or weak, that is low in the gelatinous constituent in its crude form, and so requires to be concentrated. To effect this at the lowest cost it should be passed through the Scott multiple effect vacuum evaporators. These are heated by the exhaust steam. In this form of evaporator the heating effect of the steam is multiplied in several stages, thus doing so many times more work for one supply of fuel as compared with a simple evaporator. The evaporation proceeds progressively and continuously, the liquor leaving the evaporator at a high degree of concentration owing to the water having been driven off. The gelatinous residue accruing from this treatment may be blended with the fibrine or meat-meal, thereby enhancing the value of the latter, which thus becomes enriched with ammonia and protein to an appreciable degree.
For some reason or other the treatment of the “stick liquor” has not aroused the measure of serious attention in these islands which it deserves. While, of course, greater results are attainable from treatment of the liquid upon a huge scale, yet relatively small quantities can be exploited very profitably, because the jelly finds an attractive market as crude tub size, the demand for which to-day is somewhat keen and firm. Doubtless hesitation to turn the stick liquor to economic account is due to lack of knowledge concerning the improvements in the rendering process, and the difficulty encountered in this direction in the past. Under the old system, where the practice was to evaporate these liquors in open vessels, the nuisance created constituted the insurmountable obstacle. The work could not be carried out without polluting the whole neighbourhood. With the Scott evaporator, however, no more nuisance is created in concentrating the offensive liquor than attends the exploitation of noisome fats by the patent digesting process, for the simple reasons that the work is conducted in closed vessels, and all obnoxious vapours thrown off during the treatment are led to the furnace to be consumed, escape of the free gases into the air being rendered totally impossible.
British waste exploiters are beginning to appreciate the advantages of the closed evaporative system, and in their determination to secure every retrievable ounce of commercially valuable products from waste are now devoting greater attention to the stick liquor. The policy is one which cannot fail to pay so long as it is conducted along the correct lines such as I have indicated.
Before leaving the question of the stick liquor it is curious to remark how some firms, while complimenting themselves upon the assiduity and diligence with which they treat their wastes, are yet likely to allow a certain material, and one which is of distinct value to their own businesses, to slip through their fingers merely from lack of knowledge. The abandonment of the stick liquor arising from the digestive treatment of meat-waste represents an interesting example of such inadvertence.
Many manufacturers dealing with meat products have installed a fat-recovery system for the treatment of their waste upon the spot, the primary idea being to secure the good edible fat for re-use in connection with their own processes. Furthermore, from their association with the cooked-meat trade they find it necessary to absorb material quantities of gelatine to carry out the glazing work in the preparation of brawn, pies and other dainties. They purchase the crude gelatine for the purpose, submitting it to careful treatments to adapt it to their varying requirements. Yet, if they but knew it, they have no need to spend a single penny—or cent—upon gelatine wherewith to conduct the final appetizing touches to their wares. They have as much of this raw material as they can possibly require immediately to hand in the stick liquor, and which, in the majority of instances, they allow to escape.
As a matter of fact this liquid residue is far preferable to the commercial gelatine which they buy for glazing purposes. They need only to attach an evaporator to their recovery plant to bring about its concentration. But this is not the only advantage. The gelatine has to be of varying densities or strengths according to its precise application. When they have their own evaporator this desideratum is readily fulfilled. It is only necessary to draw off the material from the evaporators when it has reached the requisite degree of concentration for immediate use. Not only is appreciable time saved, but the up-to-date firms are better off in pocket because they are utilizing a waste for which otherwise they would have to employ a purchased commodity. Even if they conduct concentration to the absolute it does not matter; the article is then recovered in the form of an edible jelly. This can be clarified, if desired, to be sold as such, or it can be sold to fellow-manufacturers who do not happen to have such a plant. Failing such disposal there is no difficulty in selling the jellied mass as tub size.
In a previous chapter I have described the reclamation process practised by the military authorities in connection with bones arising from the cutting-up of meat for the army, as well as those recovered from the swill-tubs. As indicated, however, exploitation is conducted only to a certain point, when the bones are handed over to the degreasers. It is then that the true recovery of the commercial constituents of the bone commences. The bone is an invaluable friend to the human race as an article of commerce, though it is to be feared that what may be described as the “bone tree” is only imperfectly understood. Its far-reaching value as a fertilizer is certainly appreciated, but this really represents the final application of the article, and may be said to be the only remaining field of utility for the ultimate residue of a residue. Bones enter into a wide range of industrial and manufacturing operations. For this reason they should be carefully gathered and retained for surrender to recognized collecting mediums rather than suffer abandonment or destruction.
The housewife is prone to regard them as mere waste when she has extracted the utmost recoverable value therefrom in the kitchen. She may possibly retain them until the itinerant specialist in this commodity, to wit, the rag-and-bone man, comes round, in which event it is sure to be sped once more on a journey of industrial exploitation. But at least one-third of the bones which enter the households of Britain escape reclamation. They are wantonly wasted, and it is to be feared that the kitchen stove is mainly responsible for this loss. The volume of bones which should be forthcoming from domestic circles in Great Britain, were the dictates of thrift religiously followed, is scarcely appreciated, but it is estimated that the supply should be at least 100 tons per week from every million members of the population.
In these islands the bones are divided into two broad classes. The one division, comprising what is known as “green” (raw) bones, represents those collected from butchers’ shops, bacon-cutting works, and other similar sources. The second class, defined as “streeters,” include those forthcoming from the recognized collectors of such waste, hotels, restaurants, clubs, and private houses, and are those which have been passed through one or more cooking processes.