Fishmeal partial substitution within aquafeed formulations: life cycle assessment of four alternative protein sources

Purpose: Fed aquaculture has long been based on fishmeal (FM) as the main protein source for carnivorous species, but when its demand and price began increasing, both researchers and the industry started to search for alternative protein sources to meet the challenge of securing aquafeed. Consequently, this study has recourse to life cycle assessment (LCA) methodology to identify any critical points and improvement strategies in the current production of four partial substitutes for FM namely dried microalgae biomass from Tetraselmis suecica (DMB_TETRA) and Tisochrysis lutea (DMB_TISO); insect meal (IM) from Hermetia illucens larvae; and poultry by-product meal (PBM). Methods: System boundaries are from the cradle to the mill gate, thus including the production phase (and the related upstream activities) and the subsequent biomass processing into unpackaged dried meal. One tonne of protein content was chosen as functional unit. The inventory was based on foreground data provided by the industry and complemented by background data sourced from the Ecoinvent v 3.4 and Agribalyse® v 1.3 LCI databases. The environmental effects were assessed considering five impacts namely global warming (kg CO2 eq.), acidification (kg SO2 eq.) and eutrophication (kg PO43− eq.) estimated via the CML-IA method, plus cumulative energy use (MJ) and water use (m3 m−2 month−1). Two alternative scenarios per production chain were considered in order to increase the robustness of the results. Results and discussion: The performance-based ranking indicated the PBM and IM scenarios as the most sustainable options. Both microalgal systems scored the worst performances in four impacts out of five, with eutrophication impact as the only exception. The nutrients provided to poultry and insects (i.e. the feed) as well as to microalgae (the carbon source and the fertilizers) were the main contributors to impacts, together with energy consumption. Despite being cultivated with identical technologies, the two microalgae showed different performances due to their different annual yields and to different consumable goods, water and energy consumptions. Conclusions: The results provided a ranking of these four partial FM substitutes and allowed to make useful considerations on how to improve their environmental sustainability. To this regard, the impacts of IM and DMB production could be reduced by improving nutrient efficiency and reducing energy needs. On the other hand, PBM production is already optimized and is not expected to change substantially in the future years.