Millions from Waste by Frederick Arthur Ambrose Talbot - HTML preview

CHAPTER VII
 WINNING WEALTH FROM SLAUGHTER-HOUSE OFFAL, CONDEMNED MEAT BONES, AND BLOOD

Undoubtedly one of the wonders of civilization is the ability to preserve and transport such a readily perishable foodstuff as meat in a chilled and frozen condition for an indefinite period of time. By this means cattle roaming the extensive ranches of North and South America, Australia and New Zealand, are rendered available in a fresh form for presentation upon the tables of Britain to supplement the severely limited domestic supplies. During recent years the growth of this traffic has been remarkable, and it will not be long before we touch the million-tons-a-year mark for imported beef, mutton, pork, exclusive of ham and bacon.

Yet the development of this trade has reacted directly against our own interests. The dispatch of the carcases to these islands in the dressed condition has deprived, and still is depriving us, of much valuable raw material to which we should have access were we to raise sufficient meat to satisfy our own needs. This is the exploitation of the offal or inedible portions of the beast, the products obtained from which are not only of marked intrinsic value, but enter into so many other and varied industries. From this statement it must not be imagined that we are entirely prevented from establishing a meat-waste industry, since our domestic killing trade is of distinct significance and is supplemented to a certain degree by the “home-killed” business. The latter, as is well known, represents the shipment of cattle to this country in the live condition to be slaughtered upon landing.

In these circumstances it would be perfectly feasible for us to establish the meat residue exploitation industry upon a comprehensive scale but for the fact that existing conditions are decisively adverse, although we could scarcely aspire to attain the magnitude and operations of the huge meat-packing plants of Chicago. It is extremely doubtful if we really appreciate the possibilities of this business, and, because of our ignorance, we, as a nation, are the losers. We have permitted the local or territorial slaughter of cattle to be carried to an extreme length. The municipal abattoir constitutes the feature of the slaughtering trade of these islands, and although this practice was introduced to overcome the shortcomings of the private slaughter-house, which were many, and to ensure killing and dressing animals under the most hygienic and scientific conditions, yet it is a matter for serious consideration as to whether the municipal practice should not be superseded by a centralized system, acting under State or private control, the latter for preference, so as to give full rein to the display of initiative.

There is no logical reason why the slaughter of domestic cattle should not be conducted at a central point. Such a plant conducted along the lines practised at Chicago would be of far-reaching benefit to the community. Supervision would be more effective, simpler and less expensive, inasmuch as it would be possible to dispense with the multiplicity of officials now obtaining—another form of waste. It would also enable the residues from the trade to be turned to utilitarian advantage along the most economic and profitable lines, owing to their very bulk. A visit to the Chicago stockyards brings home very forcibly the magnitude of this trade and the wealth to be won from the residues which accrue. It has been declared, and with considerable truth, that at the American stockyards the development of the by-products is every whit as extensive and as important as the preparation of the ostensible staple product. It is actually more profitable, and brings in as great if not greater revenue.

The arguments which would be levelled against the establishment of a central meat-packing plant in this country are many and obvious. In the first place full voice would be given to the apparent futility of sending a live animal from 20 to 600 or 700 miles merely to be killed, and to return the dressed carcase to be sold. Superficially it does appear to be a senseless employment of transport and to incur needless expense. Yet such a practice is followed upon the North American continent. Animals are shipped alive over hundreds of miles to be killed and returned to the point where they were bought, in the form of dressed meat ready for consumption. But the argument is fatuous. Centralized slaughtering facilities secure equitable distribution, as well as prompt movement, since the trade is sufficiently heavy to demand the inauguration of a special handling and transportation system. Then again such a practice allows bulk shipment combined with long haulage, two essential conditions to economic transportation. If the method were practised in these islands, not only would it be possible to take full advantage of the latest manifestations of science in so far as it affected the industry, but it would enable the residues forthcoming in enormous quantities to be treated upon the spot in the reclamation plant forming an integral part of the stockyard equipment. The revenue derived from the disposal of the by-products rendered available in a commercial form would not only more than offset the charges incurred concerning transportation, but would tend towards the primary product—the meat—being sold at a lower figure to the public.

Under the present system of local killing much of the offal escapes reclamatory treatment for the simple reason that the quantity forthcoming is so limited as not to be deemed worthy of exploitation, or else is subjected to obsolete or inefficient by-product recovery methods. In many instances it is sold to a contractor who endeavours to conduct bulk treatment upon a reduced scale, paying a relatively low price for the refuse and one quite disproportionate to its true value. In some instances the contractor does not attempt to carry out by-product recovery, but merely acts as a middleman, dispatching the various residues to the quarters where he knows they will be taken in hand to be worked up.

During the past few years the science of winning wealth from slaughter-house offal of every description has made enormous strides, effort having been concentrated upon the recovery of the very utmost yield of by-products for the simple reason that the demand therefor is exceedingly keen, while prices are necessarily attractive. This applies particularly to the fats, the value of which ranges up to as much as £50 per ton, according to grade, although other commodities simultaneously secured, such as meal for cattle-feeding and fertilizers, are able to command equally impressive prices. A graphic idea of the degree to which this science has been advanced is obvious from the dimensions, comprehensiveness and modernity of the by-product installations which have been laid down as adjuncts to the mammoth cattle-killing plants in various parts of the world, the majority of which, as I have pointed out in a previous chapter, are of British origin, design and construction, and many of which have been, and still are being, supplied from this country. Surely it is somewhat anomalous that other countries should come to us for the latest expressions of ingenuity and invention in this province when we are unable to point to a single pretentious plant in this country! At the same time it is distinctly gratifying to learn that if Britain cannot display sufficient imagination or commercial acumen to use plants of this character, she certainly can build them, and is not only able to keep well astride of the times, but is fertile in thought concerning a highly specialized ramification of industry.

As a matter of fact it may come somewhat of a surprise to learn that British thought is far in advance of American practise, as manifested by the stockyards at Chicago in regard to the utilization of appliances and process for the treatment of meat residues. The interests at the mammoth plant were approached with the latest British development in this line—the solvent extraction process described in a previous chapter—it being recognized that its introduction to the American stockyards would apply the seal of highest approval to the invention and represent a great achievement for the British interests which had evolved and perfected it. It possessed every virtue likely to make appeal, more particularly the means of enabling the American packers to add to their already huge profits. The process was investigated, and its superiority over the methods in vogue was frankly conceded. But the Chicago industry firmly declined to embrace the invention, not from feelings of hostility, but because the interests concerned had developed their own plant along lines, and to a degree which would not readily permit a revolution. To have introduced the new idea would have been to disorganize the whole business of by-product reclamation and would have demanded the revision of methods, knowledge, practice, and routine. Questions of cost did not enter into the issue at all. The packers merely declined to disturb the system they had standardized and had carried to such a level of perfection.

But the packers were not wholly opposed to progress. Although not willing to introduce the system into their plants, they were quite ready to turn over their wastes, after they had extracted as much as they could of material value therefrom under their system, to the British interests. The inventors accepted the proposal, and to-day one may witness the strange and anomalous spectacle of British interests taking over the residues from residues from the packing plants for further treatment, and conducting the unusual method of trading to their financial profit. It was confidence in the superiority of the new idea which brought such signal success. Yet this exploitation of wastes from wastes is not peculiar to Chicago. It is even being practised to a limited degree in these islands, which suffices to prove that certain quarters are fully cognizant of the wealth awaiting to be won from waste, and that it pays to conduct the process to the recovery of the uttermost retrievable ounce even from such material.

Certain of our municipalities, fully alive to the value of the waste incidental to the operations of their abattoirs, are sparing no effort to utilize such material to the full. However, in many instances, their enterprise is thwarted by the circumstance that the butchers making avail of the Corporation facilities extended, possess certain vested interests which must be honoured. Accordingly it is not possible to conduct reclamation to such limits as would be attainable were methods comparable with those prevailing at the Chicago stockyards in operation. To be able to extract the utmost from the refuse it is imperative that the authorities should be given unrestricted control of the animal, preferably absolute ownership. This is the reason why the big private packing plants are able to achieve such eminent success. They purchase the live animals, and consequently are free to exploit them in accordance with the principles they have elaborated. Nevertheless, despite the difficulties obtaining, much good work is being accomplished in British circles concerning abattoir waste exploitation.

The case of Edinburgh may be cited as an illustration. I purposely select the Scottish city for the reason that—so far as municipalities are concerned—it is possessed of one of the most up-to-date installations in the country, is enterprising, and serves to bring home how vested interests can mar a record of possible achievement by restrictive action. The blood is sold to a contractor, who, however, is compelled to sell back to the meat trade such quantities of this article as may be required. A proportion of the offal is also sold by the meat trade.

Diseased meat, condemned as unfit for human consumption, is treated by the authorities in the Scott plant which they have acquired. The waste is thoroughly sterilized by steam, the residuals, comprising non-edible tallow, meat fibre and bones being sold. The plant cost £600—$3,000. The working costs may be set down at approximately £200—$1,000—per annum, while the income from the sale of the uncertain quantities of meat of which disposal is made averages about £430—$2,150—per year. The hoofs and spurs of the feet of cattle, the parings of ox-feet, a small proportion of waste offal, and the manure originating in the slaughter-house, are sold by the Corporation. The sum derived from these sources during the 1917-18 financial year amounted to £533 5s.—$2,666.25—while the revenue from the sale of blood was £437 11s.—$2,187.75. All things considered it must be conceded that the by-products resulting from the operation of the slaughter-house by the Corporation of the Scottish city are fully utilized, although the defects arising from divided responsibility for the development and disposal of the wastes are obvious.

Divided interests exert another reactive influence. The public authorities are debarred from making full avail of the latest improvement in the art and craft of waste recovery. For instance, although the leading abattoirs of these islands have acquired reasonably up-to-date plants, they are all operated upon the open steam principle, with and without vacuum. The method, while satisfactory so far as it goes, does not offer the means of securing the utmost from the available material. But the authorities do not feel justified in going to the expense of acquiring the latest appliances for the prosecution of the work of reclamation, an attitude which is perfectly explicable in the circumstances.

Of course, the community suffers, though imperceptibly. The plants in question allow a certain proportion of waste to be lost which in the course of the year represents an imposing figure. Furthermore, the whole, or the greater part, of the “stick liquor” or gelatinous liquid thrown off during the fat reclamation process is lost, being allowed to escape down the drains. The abandonment of the stick liquor is regrettable because it constitutes a waste capable of being treated with profit, as I explain later. But it is doubtful whether the average municipal plant, even if it had absolutely unfettered control of all the waste products arising from the slaughter of cattle for food, would be in the position to treat the stick liquor to commercial advantage. An evaporative plant would have to be incorporated to concentrate the gelatinous substance to the desired density, and only in a few instances would the quantity of material treated be adequate to render the utilization of the stick liquor profitable. But this constitutes an additional argument for centralized meat packing and offal exploitation in these islands.

Accordingly effort is exclusively confined to the recovery of the grease. I have described the outstanding features of the vacuum system in a previous chapter, to which I would refer the reader desiring enlightenment in connection therewith. The grease is drawn off by a special skimming device into a fat tank to be clarified. Then it is run into barrels or other suitable receptacles for transport. It is scarcely necessary to point out that the grease and tallow thus obtained from condemned meat and other offal, although thoroughly sterilized in the rendering process, are graded only as fit for the manufacture of soap and other articles of utility, as distinct from products of edible importance.

The term “offal” in its application to meat residues is somewhat ambiguous. It not only comprises material coinciding with the general interpretation of the term, but certain portions of the animal which are really suited to the preparation of foodstuffs for the table. Consequently all grease recovered from the digester is not necessarily adapted to manufacturing purposes only. In these circumstances it is necessary to grade the fat before treatment, the fresh fat, which is quite suitable for yielding material adapted to the preparation of margarine, for instance, being kept distinct from the lower grades which cannot possibly be classed as edible. Selection and separation treatment of the two grades—edible and inedible—are profitable because, while both are in keen demand, it is the former which is able to command the higher market figure. But when edible fats are sought it is preferable to employ the steam-jacketed digester because the fat thus obtained, from the fact that the steam is not brought into contact with the material during the cooking process, is of enhanced quality, being sweeter, while all the natural properties of the fat are retained for reasons already set forth.

Although, therefore, the most popular system in vogue for reclaiming fat from slaughter-house residues is exposed to criticism, owing to what may be described as lack of efficiency in operation due to the recovery of the fat not being as high as it might be, it appears to meet the conditions of the average municipal abattoir. City and borough corporations, unlike private organizations, are not in the position to scrap an existing plant for one which is of later date and greater efficiency, because there is not the same incentive to reap the utmost benefits attainable as prevails under private conditions where the full brunt of competition is encountered. Of course, the initiative of corporations is just as pronounced as that of private firms and individuals, but it is the exception rather than the rule. Furthermore, the municipality is not in the position to run a plant under full load, or even at a uniform pressure the whole time. It is only able to handle the waste as it accumulates during its own abattoir operations. On the other hand, the private exploiter can acquire a plant of such capacity as to cope with the steady flow of material from the slaughter-houses, thereby keeping the by-product recovery installation working steadily at a point approaching its productive limits.

Nevertheless, the results achieved with the prevailing type of plant afford interesting reading, although it is somewhat misleading to cite them. The material varies so widely both in quantity and quality, while the ultimate fat-yield likewise fluctuates markedly. A fat bullock which has been condemned would naturally be expected to furnish a good contribution of fat. On the other hand, only a low percentage could reasonably be anticipated from a lean cow. In these circumstances a comparison without full details concerning the material handled is difficult. The figures available may be set down as being representative, though they should be accepted as being typical rather than empirical.

A consignment of condemned meat, weighing 2,240 lb., was placed in the digester. The quantities of the respective materials recovered were:—

In another instance a somewhat heavier consignment of condemned meat was committed to the recovery plant. Its composition was:—

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.

In the case of green bones it is customary to digest them, when really fresh, with open steam to recover the edible fat. Shank and marrow bones, as distinct from rough bones, are also able to yield a certain proportion of edible fat, and after having been digested or boiled still retain a considerable percentage of grease which it pays to extract. Consequently these, together with a certain quantity of less fresh green bones, and the streeters, are then passed through the benzine extractor to be degreased down to 1 per cent.

The shank and marrow bones are sawn up, the centre sections being selected for the production of such useful articles as knife and fork handles, buttons, and other utilitarian commodities for which their composition renders them eminently suitable. The ends or knuckles are degreased by submission to the solvent extraction process, and then, in some works, are subjected to further chemical treatment, which is somewhat elaborate, to be converted into baking-powder.

Otherwise the bones, after being degreased, are passed through other processes for the extraction of their gelatinous constituent. This is secured in the form of a liquor which is evaporated in vacuo to a jelly. The last-named is cooled into cakes and then dried on nets, or, if preferred, the liquor may be dried direct into glue-powder. By following a more complicated process gelatine can also be prepared from the degreased bones. But the gelatine thus obtained does not compare in quality with that extracted from skins. The degelatinizing process is not always followed, for the reason that some makers prefer to produce the higher quality bone-meal which is procurable from non-degelatinized bone. Obviously, however, the more profitable and economic procedure is to pass the bones through an associated glue plant.

The ultimate residue, whether degelatinised or not, is a bone-meal which constitutes the well-known fertilizer. The bone-meal, to be of the utmost feeding value to the soil, should carry little or no fat. At the same time, however, it should be rich in ammonia and phosphoric acid or superphosphate, which is determined in terms of tribasic phosphate of lime. To show how these requirements can be adequately fulfilled by submitting the raw waste to a complete recovery process, such as I have described, an analysis of a typical bone-meal produced from degreased bones—degreased by the benzine extraction process—but which have not been degelatinized, is given thus:—

The high percentage of ammonia, namely 7·37 per cent., deserves especial notice inasmuch as it compares with a yield of 4·5 per cent., which is the average figure recorded with fertilizing meal obtained from steamed bones. It may possibly come as a surprise to many to learn that it is the proportion of the nitrogenous content, as represented by the ammonia, rather than the phosphoric acid content, which really determines the commercial value of this manure. The higher the figure to which the ammonia figure can be forced the more attractive the price which the fertilizer will command upon the market. Thus, under normal conditions, every 1 per cent. rise in the ammonia constituent will increase the price of the bone-meal by 14s.—$3.50. On the other hand, a 1 per cent. increase in the proportion of superphosphate only serves to increase the price of the meal by 11d. to 1s. 2d.—22 to 28 cents.

The grease obtainable from green bones varies somewhat. It is affected to a marked degree by the skill and care with which the butcher wields his knife. If the bone should be scraped very clean and carefully, naturally the bulk of the attached fat is removed. But an average collection of green bones will yield about 15 per cent., or 360 lb., of fat per ton of bones treated, while the dry bone-meal will range from 1,286 to 1,344 lb. Bones which have been collected from marine store dealers and rag-and-bone merchants are not so liberal in fat yield. The repeated cooking to which they have been subjected in connection with the preparation of dishes for the table relieves them of approximately 5 per cent. of the fat which they originally carried, i.e. in the raw condition. Consequently, degreasing only enables about 10 per cent., or 250 lb., of fat to be recovered from every ton of bones treated. In this instance the bone-meal yield may be set down at 1,568 to 1,680 lb. per ton of bones. The grease remaining in the meal varies from 0·5 to 1 per cent.

As may logically be supposed, cattle-slaughtering for food produces large quantities of blood. This is an extremely valuable residue, and so is carefully collected in suitable vessels. It is then transferred to shallow receptacles and permitted to stand for a time. Blood is composed of two fundamental constituents—the serum and the clot respectively. The former, which is the albumen, is the glutinous-like, yellowish liquid which comes to the surface, the clot settling to form as it were a sediment. The serum is recovered by skimming with a suitable device, to be distributed in extremely thin layers, applied with a brush, to dry. Such a careful procedure is imperative owing to the difficulty of drying out albumen. When dry the blood-albumen is peeled in the form of thin flakes. Its applications are numerous, one of the most important being its employment for the clarification of sugar. The clot is likewise secured to be sent to the special plant, where it is also dried.

It is common knowledge that blood constitutes a magnificent fertilizer, and this is the purpose to which the dried clot is applied. In a well-designed vacuum drying plant, such as the Scott, which has been designed especially to treat such residue, the efficiency is high. The yield from the clot may be said to range from 25 to 30 per cent.—560 to 672 lb.—per ton of raw clot treated, and is recovered in the form of a rich red dry powder.

One great objection levelled against the recovery of the blood for fertilizing purposes has been the very offensive odour which is thrown off during the drying operation. But when the task is conducted under the vacuum system no such nuisance is created, because the obnoxious gases are led to the fire to suffer combustion. In dryers of the conventional type, in which the noxious gases are removed by the aid of an exhausting fan, or suffer discharge into the chimney, the process does represent an intolerable nuisance to the neighbourhood, because there is nothing to prevent the pollution of the atmosphere. Furthermore, and this is the most important point to remember, by drying the blood under the vacuum system the ammonia content of the waste, which normally is high, can be preserved to the full, owing to the drying operation being carried out at a much lower temperature than is incidental to the usual practice.

Dried blood appeals to the farmer for the nourishment of his land essentially because of its pronounced proportion of nitrogen or ammonia. Consequently it is incumbent to keep this figure as high as possible and thus secure the advantages of market quotation. Naturally the percentage thereof in the resultant meal will vary strikingly according to the drying process practised. Ammonia is an exceedingly volatile ingredient, its tendency to escape being accentuated as the temperature employed is increased. It is only by keeping the heat factor at a low level consistent with the complete fulfilment of the desired operation, that the ammonia can be retained. Under the vacuum system this end is assured, owing to the low boiling-point due to the reduced pressure or vacuum. A typical analysis of vacuum-dried clot blood may be cited:—

In cases where the albumen is not required separately the whole blood is dried without being separated or “clotted.”

It is obvious from what I have related, that the recovery of by-products from what has always been regarded as waste of a most repulsive character, that is from the popular point of view, can be turned to striking commercial and industrial account. Similarly it is only too apparent that such by-product reclamation as is possible demands a plant of the most complete description, to ensure all and every substance of utilitarian value being secured along the most efficient lines and to the uttermost ounce.

The day has gone when the crude methods which sufficed to satisfy individual or specific requirements should be continued. To endeavour to render it profitable to recover but one article out of many which are reclaimable simultaneously, and for the expenditure of only a little more effort, time and money, may be compared with mining for one hundred carat diamonds and allowing all those of lesser weight to fall back into the earth.