Environmental assessment of enzymatic protein hydrolysates from farmed gilthead seabream side streams

Seafood industry side streams include non-edible parts such as heads, tails, and trimmings. Utilizing these by-products not only enhances environmental sustainability but also increases economic value. Enzymatic hydrolysis is an effective method for recovering protein ingredients and fish oil, enabling the production of hydrolysates with functional properties. This study aimed to evaluate the environmental impacts of generating fish by-products from farmed gilthead seabream, valorising them through enzymatic hydrolysis, and comparing this process with conventional fishmeal and fish oil production, as well as with steam-hydrolysed feather meal from poultry processing. The allocation method significantly influenced the results, with economic allocation chosen as the fairer approach. Fish production had the highest contribution in the by-product generation phase, as processing large quantities of fish requires relatively few resources, including energy, water, and refrigeration gases. The valorisation phase, particularly enzymatic hydrolysis, emerged as the main environmental hotspot within the fish protein hydrolysate supply chain. Energy use—especially during drying—had the greatest impact. Replacing it with renewable sources or implementing more efficient drying methods could significantly reduce emissions. Although fishmeal and fish oil production showed lower environmental impacts, they offer less added value compared to hydrolysates. Poultry feather hydrolysate production, already industrially optimised, demonstrates that scaling up enzymatic processes can enhance resource efficiency and reduce impacts. Scaling up production and improving energy efficiency are essential steps in advancing circular economy practices and guiding industry stakeholders toward more sustainable decisions.