STARTING FROM THE BOTTOM: USING LOW TROPHIC SPECIES IN SALMON FEEDS. Assessing the environmental performance of novel salmon feeds with LCA .

Abstract: Over the past 30 years, the formulation of salmon feeds has shifted from being based on marine ingredients like fishmeal and fish oil towards more plant-based ingredients. This shift was caused by limited supply of wild fish and general sustainability concerns related to using forage fish for feed, so they were mainly replaced with vegetable-protein. Previous studies of farmed Norwegian salmon have shown that feed use is the most important sustainability input factor of the whole industry, both economically and environmentally. Using Life Cycle Assessment (LCA), this study compares the resource use and emissions caused by conventional feeds to those caused by novel feed formulations in which a part of the marine inputs, and in some cases soy, were replaced by seaweed or blue mussel silage. Different feed formulations are compared per ton of feed and data from a fish trial done in Norway is then used to estimate emissions for a salmon production scenario using those novel feeds. The analysis of the feeds covers greenhouse gas emissions and agricultural land use. The estimation of the emissions caused by the salmon production covers greenhouse gas emissions and marine eutrophication. The results show that replacing fishmeal with 1-4% seaweed silage in the feed lowered the greenhouse gas emissions marginally by up to 5% compared to the conventional reference feed. The replacement of fishmeal and soy protein with blue mussel silage (up to 11% in the feed) reduced greenhouse gas emissions by up to 10%. Replacing soy protein also results in lower land use. However, applying these feeds in a salmon production scenario shows that the overall emissions increase when replacing common ingredients with novel ingredients, mainly due to an increased feed use. These findings should be considered when applying novel feed formulations in salmon farming for ecological benefit.