From feed to fork: life cycle assessment on an Italian rainbow trout (Oncorhynchus mykiss) supply chain

The body of knowledge in trout farming sustainability is still not exhaustive, mainly due to the variability in the production system and in the methodological approach and partly to data quality issues. As such, Life Cycle Assessment (LCA) was applied to a trout supply chain located in Northern Italy, basing the inventory dataset almost entirely on primary data gathered from producers and extending the system boundaries beyond the conventional farm-gate, in order to include: phase 1. feed production; phase 2. trout grow-out in freshwater flow-through systems; phase 3. trout processing into foodstuff; phase 4. fish by-products processing into pet-food ingredients. The results highlight that, while resource sharing in phase 3 is a winning practice and leads to decrease in environmental impacts, the other three phases present crucial aspects which require either technological or methodological improvements. Firstly, the relative contribution of feed ingredients is very high, with respect to all the impact categories considered. Secondly, despite on-farm effluents account alone for 92% of downstream river eutrophication (phase 2), data from rivers environmental monitoring prove this result to be an overestimation, due to the fact that LCA does not adequately cover proximate ecological concerns as yet. Finally, the energy demand for the recovery and recycling of the fish by-products (phase 4) is high, causing a high impact on global warming, terrestrial ecotoxicity, freshwater ecotoxicity and cumulative energy demand. In order to improve the overall sustainability of the supply chain, changes are required mainly in the feed production and by-product processing phases. As far as the former is concerned, a winning strategy would be the formulation of feeds with more sustainable feed ingredients and further improvements in the feed quality (palatability, digestibility, nutritional content). In regard to the latter, more attention should be paid towards the source and amount of energy consumed. For instance, the use of renewable energy sources might be coupled with an improved insulation of the facilities and the use of less energivorous machineries/processes.