The dry vacuum process, which is essentially adapted to the rendering of edible fat, has many advantages over the wet steam method. Whilst the plant employed is broadly similar to that employed in the process already described, there is one notable difference. The digester is enveloped in an outer shell or jacket, and the steam is circulated through the space between the two walls. It is not brought into contact with the contents of the digester at any stage of the process. The action taking place within the vessel during the operation is precisely the same as when the steam is brought into direct contact with the refuse, the fat being rendered fluid by the heat and the cells undergoing disruption by the creation of the vacuum. A high vacuum is maintained throughout the whole rendering process. Consequently the moisture inherent to the raw material is withdrawn as rapidly as it is converted into steam, resulting in the production of a fine edible fat totally free from moisture. Moreover, the residue withdrawn from the digester at the end of the process, known as “crackling” or “greaves,” is likewise quite free from moisture, although, as in the case of that resulting from the open steam process, an appreciable proportion of fat is held up in the mass which can only be recovered to a pronounced degree by the application of pressure. The dry steam or jacketed vacuum process is especially adapted to the treatment of fresh fat waste, the reclaimed product of which is primarily intended for the preparation of edible foodstuffs, such as oleo-margarine. By carrying out reclamation without bringing the steam into contact with the fat several distinct advantages are obtained, the most important being the retention of the natural properties of the fat, and no loss of glycerine which otherwise is inevitable to a certain degree. Consequently, it is an ideal process for the treatment of the “Premier Jus.” There is no need to mince the fat finely, as in the orthodox rendering process, it being necessary only to cut the waste roughly for charging the digester. A special press has been devised for the treatment of the crackling or greaves. It is of the cage type which allows the fat, during pressure, and which operation is carried out while the residue is very hot, to be expressed between the bars of the cage to fall into a trough for recovery. The cakes, after pressing, are dry, excellent in quality, light in colour and of attractive flavour, a result due to the fact that the tissues have not been scorched or charred in any way during the rendering process. The greaves constitute an excellent ingredient for the preparation of kennel and poultry foods, and enter extensively into the manufacture of dog-cakes. In a few instances the dry greaves, owing to their high nutritive value, are served to the kennel in the straight form as they issue from the press.