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Food skimmings from DAF (dissolved air flotation) units are major waste materials from food processes such as meat and milk processing and waste water treatment plants. These materials are paste and oily. Land application of skimmings alone or mixture with other by-products for cooking are used currently. Land application potentially cause pollution problems to land, water and air. The mixture and cook with other by-products affect the quality of the final protein and fat by-products. The skimmings have only 10-20 % solid. The dry cost is high for the cooking process. These two current processes are not economically feasible methods.

DAF skimmings have nutritional value with fat, protein, and carbohydrate. A new recovery process has been developed to convert DAF skimmings into usable complex products at lower processing than is presently practiced. A typical complex product from animal meat DAF skimmings in dry form has fat 38 %, crude protein 49 %, ash 3 %, moisture 6 %, fiber 1 %, alanine 3.9 %, aspartic acid 4.8 %, glutamic acid 6.4 %, lysine 4.3 %, leucine 5.9 % and valine 3.7 %. The pepsin digestible protein is 94 %. This new process can convert the nutrients in DAF skimmings to feed and fertilizer ingredients. The dry processing cost can be reduced because the solid level is increased significantly by mechanical methods before the drying process. Also after the skimmings are removed, the values of BOD, COD, FOG and TKN in waste water are decreased after the process. A convenient process includes the following steps: (1) to convert DAF skimmings into a fat complex product, which has no oily physical characteristics; (2) to increase the solid level by mechanical squeezing methods and (3) to dry the product or to blend with other by-products such as feather meal or meat and bone meal. This new process provide an economic solution to resolve the problems related to food DAF skimmings.