Feeding farmed salmon: Is organic better?

Abstract

Feed provision accounts for the majority of material and energetic inputs and emissions associated with net-pen salmon farming. Understanding and reducing the environmental impacts of feed production is therefore central to improving the biophysical sustainability of salmon farming as a whole. We used life cycle assessment (with co-product allocation by gross energy content) to compare the cradle-to-mill gate life cycle energy use, biotic resource use, and global warming, acidifying, eutrophying and aquatic ecotoxiticy impacts associated with producing ingredients for four hypothetical feeds for conventional and organic salmon aquaculture in order to assess the benefits, if any, associated with a transition to organic feed use. Fish and poultry-derived ingredients generated substantially greater impacts than crop-derived ingredients. Despite the fact that organic crop ingredients had markedly lower life cycle impacts compared to equivalent conventional ingredients, substituting organic for conventional crop ingredients therefore resulted in only minor reductions to the total impacts of feed production because the benefits of this substitution were effectively overwhelmed by the much larger impacts associated with animal-derived ingredients. Replacing fish meals/oils from dedicated reduction fisheries with fisheries by-product meals/oils markedly increased the environmental impacts of feed production, largely due to the higher energy intensity of fisheries for human consumption, and low meal/oil yield rates of fisheries by-products. Environmental impacts were considerably lower when feeds contained reduced proportions of fish and poultry-derived ingredients. These results indicate that current standards for organic salmon aquaculture, which stipulate the use of organic crop ingredients and fisheries by-product meals and oils, fail to reduce the environmental impacts of feed production for the suite of impact categories considered in this study. This information should be of interest to feed producers and aquaculturists concerned with improving the biophysical sustainability of their products, and bodies responsible for aquaculture certification, eco-labeling, and consumer awareness programs.