Grease Recovery in the Meat Packing Industry E. N. MORTENSON Chemical Engineer, Research Division Swift & Co. Chicago, Illinois The task of finding practicable means to achieve complete recovery of every by-product and utilization of all wastes produced by indus­ trial operations is by no means a simple or easy one. Though there are ways to remove practically every constituent which may be present in the waters discharged from industrial operations, the really big problem we are all wrestling with is how to do the most thorough job of removal in a practicable and economical way. To save and to use every by-product, with sufficient return to make the effort worth­ while, by no means reduces the amount of pollutional material present in the outgoing waste waters enough to obviate the need for some degree of industrial-waste treatment. There are two choices in the manner in which the quality and character of meat industry wastes can be reduced or altered. The first and best way is to minimize losses at the source. If this step proves inadequate, the second recourse is to provide, and to use properly, treatment facilities to recover as much as possible before the waste waters finally leave the plant. Actually, in the meat packing industry we do both. By-product recovery to many of us is synonymous with the meat packing industry. Our complete use of every by-product seems astound­ ing when recounted in full detail to the layman; and he, I believe, appreciates it far more than do we in the meat industry, to whom it seems commonplace. Yet many of us make the mistake of over­ emphasizing in our own minds how well we make use of every by­ product. Often we tend to lull ourselves into the idea that nothing gets away because we do produce a large number of by-products. If we examine very critically every step of the processing of the main products and the by-products, we can readily find many places and ways in which products can be lost. 28 29 It is the purpose of this discussion to re-examine very carefully and critically every possibility where losses of fats, oils, and greases to the waste effluents can occur. Similarly, we wish to consider what can be done to recover these valuable by-product materials in simple and yet effective ways. In considering the industrial wastes which leave meat packing plants, it is readily apparent why the recovery of greases is such an important aspect of the problem. In processing livestock for meat, and for all of the by-products, both edible and inedible, practically every step from the pens to the shipping dock requires water in some amount. Since we have a raw product which contains very appreciable amounts of fat which can get into and be carried away with the water, grease recovery remains an ever-present problem from start to finish. In order that we may have a reasonable perspective of what grease recovery involves and its importance, we should first review some simple facts in regard to the meat business. First of all, it is hard to generalize as to the yields expected of meat, fats, and bones from one particular species of livestock. As an example, consider the fat content in a side of dressed beef of canner quality versus one of choice or prime grade. The canner may have as low as 11 % fat, while a side of choice grade beef may carry over 30%. (1) This is over 250% variation in terms of fat present in the dressed carcass. The actual, rendered fat recovered in the form of edible and inedible tallows from low-grade versus high-grade animals will have a proportionately similar variation. It is equally true that fat yields can vary nearly as much in the other species. Secondly, the volume of livestock processed from day to day and week to week in meat plants has wide variations. There are seasonal flush marketing periods of meat animals similar to flush seasons in other food industries, as in the fruit and vegetable canning field and the milk industry. Along with this variation in volume of raw product rides the equally variable price and demand for the primary product itself and the by-products, the latter oftentimes being in great oversupply with consequently depreciated values. This factor markedly affects the attention which is given to the recovery of such by-products as the inedible tallows and greases. In Table I we have shown published data taken from an Institute of Meat Packing, University of Chicago, publication:(2) 30 TABLE I PROPORTION OF INCOME FROM BY-PRODUCTS IN THE MEAT INDUSTRY Percentage Percentage from Percentage from from meat by-products hide or pelt Hog 96.6 3.+ Sold with carcass Sheep 81.4 4.1 14.5 Calf 92.8 7.2 Sold with carcass Steer 87.3 4.1 8.6 There is no such a thing as a fixed yield figure which can be used with certainty to determine whether a particular meat packing plant is producing a normal amount of a given by-product. Neverthe­ less, we do use for accounting purposes standard yield figures based on data developed in carefully run tests at representative plants. It is impossible to rely on actual yield data measured against standard yield results' to gauge whether losses to the waste effluents are above or below normal in a particular meat packing plant. The use of account­ ing figures to ascertain if the loss of product to the sewers is high ' only measures the grossest kind of loss. A large percentage of the blood or tank water can be lost before we get significant reductions in the animal-feeds yield per unit of live slaughter which will actually indi­ cate losses above normal. What we must keep out of the sewers rep­ resents such small quantities that they make little difference in the accounting yields. To evaluate the fats, oils, and grease loss situation in the meat packing industry, it is first necessary to point out what the normal yields of these products are. Table II illustrates very briefly what these yields may be. TABLE II NORMAL YIELDS OF FATS AND OILS IN THE MEAT PACKING INDUSTRY From beef slaughter* Edible—oleo oil and stearine 23 lb./M live Non-edible — tallow 5.35 lb./M live From pork slaughter* Edible—lard and pork fat 90 lb./M live Non-edible — greases 15 lb./M live In view of the tremendous variation in actual fat content that is available from a carcass of poor quality as compared to one of better quality, it must be realized that the data in the foregoing table are only of an approximate character. In handling various steps of the processing there are general prac­ tices that will reduce the loss of fats, oils, and greases to the sewers. Deviation from good salvage practice at the source can be found and corrected by visual inspection. A little common sense in handling product and the exercise of good housekeeping will go a long way toward reducing the losses of fat or fatty tissue. Obviously, visible losses of fatty tissue or rendered fat either on the killing and cutting floors or in processing sections where cooking and rendering is done, can be pointed out and remedied. Proper gratings over floor drains, making it necessary to shovel up small pieces of tissue rather than to let them be washed away during clean-up, are an obvious precaution which should always be insisted upon. Minimizing leaks through pump glands, valves, and gates in the rendering departments is all a part of good housekeeping and will help hold fat losses at a low level. A marked reduction in the fat loss to the sewer can be made by ex­ cluding from the offal washer all hashed product which does not need washing. There is a tendency to overdo the offal washing in many instances. Sufficient rendering equipment to handle adequately the peak volume of fatty material during heavy kills is a very important factor. Good practice in the rendering sections of a meat packing plant will do more to lessen the load of fatty tissue, protein, rendered fats, oils and greases, and intestinal contents to the sewer than can be done by careful handling in all other departments. This section, besides requiring adequate equipment, should (1) keep its water use at a minimum, (2) prevent souring of raw materials, (3) refrain from overloading melters or rendering tanks, (4) maintain machinery in good condition, (5) evaporate all concentrated cook liquors. This last point (5) in the foregoing list raises the question as to why isn't all rendering done on a dry basis so that we won't have large quantities of tank water? There are several reasons why a substantial amount of wet rendering is still done. Prime steam process­ ing has been the generally accepted method of rendering and some trade indicates a preference for prime steam lard over dry-rendered lard. Some few packers have for many years used the dry method. In recent years, and even more so at the present time, many packers are becoming interested in dry rendering but lack of equipment and the generally expensive layout required will no doubt tend to delay a complete changeover to a dry-rendering basis. Regardless of the attention given to good housekeeping and the efforts made to salvage all utilizable material at the source, to the extent consistent with practical operations, every meat packing plant 32 requires efficient and well cared for grease interceptors and catch basins.