**4. Conclusions**

Recent research on the functional properties of citrus wastes has added to our knowledge. Due to the low cost and availability of leftover fruit, which if not disposed of as environmental waste, should be seen as a potential source of nutrients capable of providing significant inexpensive nutritional supplements. Good use of citrus peels in the production of polystyrene. Polystyrene is one of the most common thermoplastic polymers used in the production of packaging materials and household and consumer goods. This unwanted manufacturing waste is rich in bioactive constituents and can be recycled as a value-added nutritional supplement that provides beneficial phenols, flavonoids, EOs, and fiber. They function as calorie-free fillers, enhance emulsions, increase water and oil retention, and can prevent a wide variety of ailments. Citrus waste extract holds promise as a source of bioactive constituents in the food industry. Some of the vital compounds extracted from citrus peels such as limonene, pectin, myrcene, and α-Pinene are used for flavor and good smell as safe food additives. Peels are a rich source of micro-nutrients and can be used as a source to improve the growth of agricultural crops and feed animals. According to literature, the biologically active compounds in the citrus peel can effectively prevent or inhibit diseases, enhance immune function, prevent cancer, and have antioxidant activity. In addition, the use of identified citrus waste will also help reduce pollution problems caused by poor residue disposal. Further research is needed to determine the bioavailability of this waste extract *in vivo.*
