Millions from Waste

by Frederick Arthur Ambrose Talbot

This waste is difficult to treat except along the most modern lines. For this reason, in pre-war days it was exploited only to a limited degree. Yet its accumulation was enormous. At some plants the piles of such refuse, which were to be seen, contained several hundred tons. It failed to arouse earnest attention until the famine in oil burst upon us during hostilities. Then these dumps created interest because it was realized that such residue is rich in oil, enormous quantities of which were lying dormant. Forthwith plants were erected and equipped with the very latest types of machinery, which augurs well for the continuation of this manifestation of industrial enterprise in the future, owing to the great possibilities attending such reclamation.

Curer offal presents the heads and other waste portions as well as a material quantity of broken fish. This refuse has far more body, and so can be more readily treated to allow the valuable by-products to be recovered.

While we undoubtedly lagged behind our competitors in turning fish-scrap to commercial account it must not be imagined that we completely ignored this potential source of wealth. Nevertheless, for the most part, we were content to conduct operations along obsolete, inefficient lines, obtaining a return far below what might have been recorded. Had these plants been of modern design and equipment fish-waste reclamation would have advanced by leaps and bounds during the war period. As new machinery could not be obtained the main task was to adapt the existing plant to satisfy the demands of the authorities, which proved a task of distinct magnitude in itself, because the majority of the installations in operation possessed no striking feature other than that of being extremely wasteful from every point of view, offering, in fact, the most convincing illustrations of How not to do it!

In some works the practice was to cook the offal in steam-jacketed cookers. Now, when kippering offal, for instance, is being treated, the material, owing to lack of body, tends to coagulate at a certain stage in the process, a large volume of oil being liberated. This oil was skimmed and the residue, resembling a stiff mud, was removed to be wrapped in cloths for submission to extreme pressure in hydraulic presses. This action served to express a certain proportion of the oil remaining in the sludge. The compressed cakes were then transferred to a steam-jacketed drier to be reduced to meal.

This process, which has not yet been completely superseded, suffers from being involved and prolonged, although these do not constitute the most adverse features. The greatest objections to it are the retention of an appreciable quantity of oil in the residue, even after subjection to pressure, which accordingly becomes associated with the meal. The last-named being sold for fertilizing purposes, the presence of the oil is objectionable, while the product also suffers from being low in ammonia. Furthermore, while the sludge is being pressed a pronounced volume of watery liquid is driven out to be lost down the drains. Seeing that this liquid carries valuable manurial constituents its loss is greatly to be deplored, and materially lowers the fertilizing—and financial—value of the meal.

A variation of the foregoing process is made in other works, but it only tends towards greater inefficiency and heavier losses. In this case only the oil resulting from treatment of the material in the hydraulic press is recovered! A third system involves the passage of the pressed cakes through a continuous direct fire-heated drier. This method is particularly objectionable, not only from the offensive odours which are thrown off, but because the ammonia content of the waste undergoes serious depreciation, owing to the high temperature employed. In certain instances the herring offal is even charged into the apparatus without any attempt having been made to separate the oil! Such a system, as will readily be recognized, has nothing whatever to recommend it.

It is the observance of such indifferent and unscientific methods as the foregoing which has been responsible for the commercial possibilities of fish-scrap to be belittled. The oil is undoubtedly ignored intentionally because fish oils are generally held to be worthy of inclusion only among the lowest grades of industrial oils. Nevertheless, were a chemist to be attached to such wasteful plants much needed reforms could be promptly introduced, although it is highly probable that the plants would be scrapped instantly at his instigation because of their lamentable inefficiency.

But we need labour no longer in ignorance. Modern science, as represented by chemistry and engineering, is able to offer an equipment capable of extracting the whole of the oil content down to 1 per cent. In other words, 99 per cent. of the oil contained in the raw offal and scrap can be recovered both cheaply and easily. The loss of such a minute fraction as 1 per cent. undoubtedly represents a remarkable chemico-mechanical achievement.

The new process completely coincides with the dictates of contemporary science. The fundamental features are cooking the refuse under vacuum and the ultimate extraction of the oil by the aid of a suitable solvent such as benzine or other equally volatile spirit, or the benzine extraction system may be used from the very beginning, in a single and complete process. I have described this highly ingenious system in a previous chapter together with the system of operation followed. Obviously while the highest efficiency can only be derived from the installation of the complete plant, the processes being interrelated, the designer found it possible to modernize some of the old-fashioned and wasteful equipments to a very striking degree by the introduction of certain features to meet the exigencies of the moment.

A very convincing illustration of what can be achieved in this connection may be related. A firm specializing in the exploitation of herring offal desired to extend its plant, but was baulked in its intentions owing to the various restrictions which were in force. Accordingly it was compelled to consider the situation of how to derive more from the existing facilities without adding to them, at least only to an insignificant degree. At first sight this may seem to have presented a somewhat intricate, if not actually impossible, undertaking. Yet it was effected.