Millions from Waste

by Frederick Arthur Ambrose Talbot

Steam is turned on and the second stage of the fat reclamation process proceeds. Beneath the wire cage a series of steam jets are radially disposed in such a manner as to allow the steam to impinge upon the cage at an angle. The cage itself is supported freely upon a suitable vertical shaft and so, under the impetus imparted by the steam issuing from the jets, naturally revolves. By varying the volume and pressure of the steam the revolving speed of the cage may be varied within wide limits. Consequently it is possible to give the cage a very high rotary velocity.

The steam, after performing its mission towards rotating the cage, is induced to ascend in such a manner as to permeate the contents of the canvas bag imprisoned within the wire cage. All fatty matter still associated with the organic material, owing to the high temperature of the steam, becomes still more fluid. Under the centrifugal action set up by the high rotary speed of the cage this fat becomes separated from the solids to be expressed through the pores of the canvas container and also the perforations of the outer cage, and to be flung against the inner wall of the extractor. The extreme fluidity of the very hot grease facilitates and expedites this separation, the expelled fat finally dropping to the bottom of the vessel to make its escape through suitable drain holes to pass into the settling tanks previously mentioned.

Under the whirling action of the turbine quite 91 per cent. of the fatty content of the mash is extracted and recovered. The treatment in the turbine extractor is continued until the flow of grease to the settling tanks is observed to cease, when steam is shut off and the extractor is emptied. The mash, somewhat resembling peat in consistency and of a rich chocolate colour, cooked through and through, is spread upon the floor to cool. Unless one has followed the cycle of operations one would never associate this odourless, clean, dry and sterilized product with the repulsive looking slush from the swill-tubs which had entered the mill barely two hours previously.

This residue constitutes an ideal pig-food. It is rich in the essentials for building up the frame and flesh of the porker, and as may be supposed finds a ready sale. It appeals to the farmer because it is clean to handle, is easier to transport than the conventional swill, because it can be bagged, while it possesses excellent keeping qualities. In effect it is a concentrated food, and accordingly can be broken down by blending with ordinary swill to increase the calories of the latter as they affect the pig, or it may be used instead of pig-meal, for which it is an excellent substitute.

Finally, it meets with the farmer’s favour because its fat content, being only about 9 per cent., coincides more closely with the animal’s dietetic requirements. It is not surprising, in these circumstances, that the farmer should be eager to procure as much of this sterilized food as he can obtain at a fair price. Certainly the authorities experience no difficulty in regard to its disposal at a remunerative figure.

The bones, upon reaching the mill, are dumped apart. They represent waste from the cook-house stripped as cleanly of meat and fat as a sharp knife in dexterous practised hands will allow. Their gravy-yielding and other nutritious constituents have been extracted from prolonged sojourn in the stock-pots. When they reach the swill-mill they appear to be as capable of rendering any further contribution to the general scheme as those bones which have passed through the hands of a frugal housewife. They have reached the stage when such refuse is either thrown into the kitchen fire, dust-bin, or handed over to the peripatetic rag-and-bone monger.

Yet they still possess distinct fat value, but it can only be wrung out by drastic effort. The bones are first passed through a crusher to be reduced to small size. At times the bone-dump from the cook-house will be found to be swollen by the dismantled framework of what was once a horse or some other animal, and which is to be passed through the fat reclamation factory. The crushed bones are submitted to the same process as the swill, being passed through the melter and extractor successively. The combined action of cooking and whizzing brings about a far more impressive release of fat than may possibly be imagined. Furthermore, cooking and whirling effectively release all slender strings and shreds of fat which may have escaped the butcher’s sharp knife, while clinging tatters of meat and sinew are also thoroughly cooked. Upon withdrawal from the extractor the bones are thrown over a riddle, this action being sufficient to detach all shreds of fibrous matter which fall through the meshes of the sieve.

The bones are now ready for dispatch to the degreasers. The loose fibrous residue resulting from riddling is collected for subsequent use in the preparation of poultry foods. Seeing that the treatment of the bones in this mill is pursued for the express purpose of reclaiming only the loose and easily secured fat and grease there is no conflict with industry. The degreasers are concerned rather with the recovery of fat resistant to ordinary salvage methods, as well as glue, size, and many other commodities involving the submission of the bone waste to many special processes, the ultimate residue being ground up to form a fertilizer.

The fat, after cooking, clarification, and solidification, presents an attractive, odourless, sterilized mass. This is dispatched to the trade for resolution into tallow, glycerine, and the requisite basic material for the production of soap.

I mentioned that, in the segregation of the wastes at the cook-house, special emphasis is laid upon the necessity to prevent the combination of all green vegetable refuse with the swill. This is essential, because in the subsequent cooking operation the dye from the green waste is extracted as every housewife knows, and, mingling with the fat, will steep the latter a pronounced greenish hue. This detracts very pronouncedly from the value of the fat because the dye, being of vegetable origin, cannot possibly be eliminated in the subsequent manufacturing operations through which the fat is passed. On the other hand, the deep yellow tinge which is likely to result from the presence of curry waste in the swill is not deleterious because it can be readily discharged.