At the moment it is the recovery of the oil, meal, and fertilizer which constitutes the primary objectives of the industry. Of the three possible by-products the meal is doubtless the most remunerative. To a certain degree the contemporary concentration of effort upon the conversion of the offal into meal is due to the fact that this constituted the essence of German endeavour in these islands before the war. This meal was in keen demand in Germany, and the bulk thereof was dispatched to that country and Japan. The interruption of this supply to the former, as a result of the outbreak of hostilities, hit the enemy somewhat severely. Not only was he thus deprived of the crude meal prepared in Britain, but he was also denied the opportunity to turn the waste accruing from the consumption in the Fatherland of the heavy imports of British herring which were also summarily cut off. Doubtless Germany cherishes hopes that her industrious sons, who specialized in this distinctive craft, will be permitted to return to the scene of their former labours and to exploit British fish-scrap once again to the advantage of the German nation upon the conclusion of peace. May the wish become no more than father to the thought. We have not failed to profit from the many lessons taught by the war: we have been forced to recognize the many virtues of fish-meal and have made, and still are making, spirited efforts to repair the losses in this line of trading which, from our indifference and lack of imagination, we lost.
To galvanize British effort the fish-meal and fish-manure (guano) manufacturers have joined hands. Propaganda has been waged vigorously by the association, while agricultural societies and colleges have willingly co-operated to spread the gospel of enlightenment. Farmers have been canvassed sedulously, and the value of these by-products for feeding stock and soil have been brought convincingly before them. As a poultry food fish-meal is declared to be unsurpassable, and this circumstance has been driven well home. The result of this onslaught has been to force the farmer, an admittedly difficult individual to convince, into the admission that these products are possessed of far-reaching potentialities, the result being that, to-day, an increasing demand for fish-meal and guano prevails, which has exercised the obvious effect of stimulating the exploitation of fish-scrap to a very pronounced degree.
During the war circumstances militated against the fulfilment of any impressive programme of development along modern lines. Plant and machinery could not be procured owing to the prior claims advanced by other industries. Consequently the problem became resolved rather into the modernization and adaptation of existing plants, many of which suffered from being woefully inefficient. But even in this direction much was achieved which cannot fail to be of distinct value, since it has served to illustrate what can be done in this field to financial profit. Now that trade is returning to the normal we may safely anticipate a striking advance along the whole industrial line in the installation of comprehensive plants coinciding with the very latest expressions of scientific thought, and which will not fail to conduce to the winning of impressively additional wealth from this hitherto sadly-neglected material.
So far as the white fish is concerned the conversion of the offal into meal represents a straightforward operation. It is merely dried under vacuum along the lines already described, a steam-jacketed drier or concentrator being used for the purpose. If the waste be stale or heavily impregnated with salt it cannot be used as food, the product in this instance being bagged for sale as a fertilizer. But the manufacturer, owing to the enhanced profit to be derived from the sale of the product in the feeding-meal form naturally strives to secure this article, and so, if designed for this use, the meal, after issuance from the drier, is passed through a disintegrator and is then graded through a sifting reel.
It is the exploitation of the herring and the sprat, both in the form of offal, glut catches, and condemned consignments, which presents the most attractive future in these islands. When it is remembered that the annual yield of the sea to the fishermen of Britain represents a round 4,000,000,000 herrings, it will be conceded that here must be a Klondyke of waste. Unfortunately, however, the issue is not so straightforward as it would seem to be. An enormous quantity of the catches are set aside for salting and curing to allow of export to foreign markets. In the past Russia and Germany were our largest customers for this foodstuff, their combined purchases running to a round 800,000,000 lb. and exceeding £4,000,000—$20,000,000—in value. When the fish is salted the treatment of the offal presents a rather teasing problem. Its excessive salt content reacts against its conversion into poultry-meal except in very small quantities which are almost too insignificant to demand attention. When a fish-meal carries salt in excess of 5 per cent. it can be used as a constituent of blended or compounded foods, and then only sparingly. Consequently the possible consumption in this field can only be relatively trifling.
By salting the herring the saline content is increased to 20 or even 25 per cent., and the removal of the added salt offers a supreme obstacle. Fortunately it crops up only at certain seasons, but, at these periods, the quantities of offal and scrap to be treated assume imposing dimensions. As may be imagined, from what has been related, salt is the bugbear to the meal manufacturer and he is hard put to it to bring the figure down to one coinciding with trading requirements. What he desires is a simple, inexpensive process whereby the excessive salt may be eliminated without impairing the other virtues of the material in any way. Needless to say the discovery of such a preliminary treatment, meeting with his desires, will be received with unfeigned delight.
The suggestion has been advanced that the extraneous, or added, salt might be removed by subjecting the offal to a washing process. Undoubtedly, in this way, the desired end could be consummated to a certain degree, but, at the same time, there is the danger that the water would not only carry away the salt but would bear with it an appreciable proportion of the valuable nitrogenous matter which it is imperative should be retained. Unfortunately the salt is not completely free; it permeates the fish through and through and is held by the tissues. In view of the difficulty obtaining the manufacturer, as a rule, converts the heavily salted offal into fertilizer, but the enhanced salt content of the manure is regarded with certain misgivings even by the farmer.
This problem assumed its maximum intensity during the war. Huge quantities of barrelled herrings, destined for export to the countries upon the other side of the North Sea, were held up by the authorities, who feared that they might ultimately find their way into enemy countries. As there was no other outlet for this produce, the salted herrings not being regarded with favour here, these prohibited exports were ultimately thrown upon the hands of the meal manufacturers. Such an instance is decidedly abnormal, but as already mentioned the issue arises to a lesser degree under conditions of ordinary trading, and, consequently, demands a certain amount of attention.
The engineering firm specializing in plants for the exploitation of fish-scrap, to which I have alluded, is attacking this problem in its extensive well-equipped laboratories. The chemist favours the theory that the extraneous salt is capable of ready removal. He also realizes that the perfection of a simple and cheap process to this end will probably accomplish a further beneficial purpose. Traces of blood are occasionally encountered in the offal, and their presence tends to discolour the resultant meal. These might possibly be eliminated contemporaneously with the removal of the added salt.
While I have dealt somewhat at length with the artificial salt problem, as it were, it must not be imagined that it constitutes a constant or inseparable feature of the fish-waste by-product recovery industry: far from it. Herring offal, while extremely varied, falls into certain distinctive classes. There is the scrap, or waste, as well as condemned consignments and surplus incidental to the fresh fish trade, which during the recurring periods undoubtedly touches a very high figure. Then there is the kippering and curer offal, the yield of which is much more formidable and easily recoverable from accumulations at central plants where such work is carried out upon a large scale. The kippering refuse, of course, represents that incurred in the process of kippering the herring and, comprising for the most part the gut of the fish, presents a material having little body or substance.