# Oil Press-Cakes and Meals Valorization through Circular Economy Approaches: A Review
## 5 Possible Ways to Capitalize the by-Products Obtained from the Oil Industry
### Animal Feedstuff  
A possible valorization of the residues resulted from oil extraction process is in animal feedstuff. Their utilization can be limited by: seasonal production (that can lower spatial and temporal availability), low levels of nutritive components, presence of toxic compounds (with possible negative effect on animal performances), and composition variability (diet formulation becomes difficult). This valorization strategy improves economy, and environment sustainability. Oil cakes rich in fat and proteins can be suitable for feeding omnivores, while those with high cellulose content for ruminants [4; 99]. Soybean oilcake may be used primely in the diet of monogastric species (chickens and pigs), palm oilcake in ruminants, rapeseed, sunflower, and pumpkin oilcakes in pigs [174]. Ensuring durable and economic fish farming involves the use of fishmeal substitutes. Different studies investigate the possibility to use oilcakes as feed in aquaculture. Pellets were produced by replacing 25% of the reference fishmeal with rapeseed, sunflower, soybean, and linseed press-cakes. The products obtained had similar nutritional values to the reference with high sedimentation velocity and less water stability, abrasion resistance, and expansion. This can be improved by using finer milled particles and altering the screw configuration of the extruder [21]. [PERSON] et al. [175] observed that the replacement of fish meal with sesame press-cake (without amino acid supplementation) up to 52% did not reduce rainbow trout growth performances. The feed cost can also be reduced and made more sustainable. The performance of mustard and soybean press-cake in fish production was analyzed. The first cake led to poorer growth and food conversion ratio, but the second one is advantageous for crap breeding [93]. Fish meal can be replaced also with solid state fermented oilcakes, this process increases the levels of amino acids and decreases crude fiber content and antinutritional factors. Fermented soybean meal (200-400 g/Kg), sunflower cake (0-100 g/Kg) and groundnut oilcake (20-50%) were used in different levels as a replacement to fish meal in the diets of shrimps and carps. The inclusion up to 325.1 g/Kg, 32.6 g/Kg and 40% respectively had no adverse effect on growth, carcass composition and feed utilization efficiency in comparison to the reference diets [90; 115]. In ruminants feeding is necessary to cover the nutritional needs (energy, protein and mineral intake) for animal production. [PERSON] et al. [99] investigate the potential use of fifteen oilseeds cake (from hemp, sunflower, tobacco, cardoon and pomegranate) as protein supplements in their feeding. Of all this, hemp and tobacco oilcakes are the most suitable due to the high content in carbohydrate and slow degradable fractions of crude protein. Olive cake contains a low amount of proteins and considerable percentage of tannins, which makes it unpalatable and poorly digestible. In order to remove these antinutritional components and increase the protein content, olive cake was subjected to a biological process (SSF). The cake was inoculated with four fungi (_Beauveria bassiana_, _Rhizodiscina_ cf. _Ignyota_, _Aspergillus niger_ and _Fusarium flocciferum_) for 15 days. Results showed a significant (\(p<0.05\)) increase in proteins (94%) and decrease in phenolic compounds (43%), flavonoids (70%) and condensed tannins (42%) due to the production of enzymes (oxidases, peroxididases) by fungi [176]. In dairy sheep feed concentrate, two levels of oil cake (rapeseed and sunflower) inclusion (50% in winter and 30% in spring) did not affect the cheesemaking (crude fiber/crude protein ratio) or milk production parameters. Analysis on the milk showed that in winter, when the pasture is unavailable, the amount of healthy fatty acid increased [37]. Satisfactory carcass yield and feedlot performance (body weight gain, feed conversion efficiency) also were observed with the addition up to 20% (300g) of groundnut and sesame oilcakes [177; 178].