Aquaculture production set a new record in 2020, with over 120 million tonnes of production, whichcorresponds to about half of the global seafood consumption. However, Swedish aquacultureproduction is currently low, but slowly increasing. The global aquaculture sector is predicted tocontinue to grow but needs to reduce its environmental footprint. In intensive aquaculture in whichfeed is used, feed inputs often account for the largest share of environmental impacts, thus feeddevelopment is a priority to increase the sustainability of fed aquaculture.The purpose of this study is to evaluate the environmental sustainability implications of shiftingto more regional and circular feed inputs for rainbow trout, by, as a first step, estimating thegreenhouse gas emissions – or carbon footprint- of the novel feed and fish raised on it compared toconventional production. Fish were produced in net pens in Sweden and fed either a conventionalfeed (reference), or an experimental feed in which 60% of the protein content derives from novelingredients (insects, blue mussels, sea squirts and fava bean protein isolate) sourced from the Nordiccountries to replace land animal by-products (i.e. blood meal and poultry by product meal) and soyprotein concentrate.Results show that the novel feed reduces greenhouse gas emissions of one kg of rainbow troutby around 63 %. Fish fed the experimental feed maintained the same growth and economic feedconversion ratio (eFCR) as fish fed the control feed. The reduction is mainly due to the almost 70%lower emissions of the experimental feed; 1.6 kg CO2eq./kg feed compared to 5.4 kg CO2eq./kg feedof the conventional feed. Feeding fish insects reared on plant-based waste streams from the foodindustry, increases the circularity and reduces emissions. However, the modelling choice that somefeed inputs based on side streams with no economic value are free of environmental burden, has astrong influence on the results. Despite shorter transport distances no lower impact of transportscould be found for the experimental feed due to the utilisation of more climate intensive transportmeans/modes. Further, the novel feed ingredients used in the study come from pilot or test scaleproduction plants, with potential to further decrease emissions with optimised processing. Atpresent, the available volumes of these feed inputs are limited which prevents a rapid large-scaleshift of the aquaculture industry. Other sources of uncertainty include the fact that the FCR is basedon a four-month growth trial which might not reflect a complete production cycle. This studyindicates that there is a potential to reduce the carbon footprint of intensive aquaculture by usingalternative protein sources, an important step that shows that it is worthwhile to continue expandingthe analysis to cover also other environmental aspects to avoid shifting burdens between differenttypes of environmental impact.