Eggs represent one of the most consumed animal products worldwide. In Europe, over 366 million laying hens and 6.1 Mt of derived eggs have been estimated in 2020, and Italy represents the fourth largest producer (41 million hens and 0.79 Mt of eggs). Egg production has been identified as relatively environmental-friendly, but several environmental concerns have been recently raised considering the inefficient spent hens' management. Spent hens are generally euthanized and composted or incinerated, producing greenhouse gases while at the same time significant nutrients are lost. First, the research reviews the egg supply chain characteristics and the alternative spent hens' valorization pathways. Then, using the material flow analysis, the research quantifies and qualifies the consistencies of laying hens and protein content included in spent hens across Italy, providing a comprehensive assessment of the national scenario under an environmental and circular perspective. Furthermore, the research develops an inventory of the spent hens' co-products and by-products in Italy, focusing on the flows of proteins for further environmental studies. The research has highlighted that over 13,948 t of proteins could be extracted, distinguishing between those embedded within offal, feathers and blood. In addition, spent hens can be used for human consumption, as well as for material or energy recovery through anaerobic digestion or microbial fermentation. Results are addressed to farmers, who are required to boost their environmental performances, and public authorities, who must implement sustainable strategies to collect spent hens.
