Greenhouse gas emissions of rainbow trout fed conventional and novel feeds from the Baltic region evaluated using life cycle assessment

Abstract

Aquaculture production set a new record in 2020, with over 120 million tonnes of production, which corresponds to about half of the global seafood consumption. However, Swedish aquaculture production is currently low, but slowly increasing. The global aquaculture sector is predicted to continue to grow but needs to reduce its environmental footprint. In intensive aquaculture in which feed is used, feed inputs often account for the largest share of environmental impacts, thus feed development is a priority to increase the sustainability of fed aquaculture.

The purpose of this study is to evaluate the environmental sustainability implications of shifting to more regional and circular feed inputs for rainbow trout, by, as a first step, estimating the greenhouse gas emissions – or carbon footprint- of the novel feed and fish raised on it compared to conventional production. Fish were produced in net pens in Sweden and fed either a conventional feed (reference), or an experimental feed in which 60% of the protein content derives from novel ingredients (insects, blue mussels, sea squirts and fava bean protein isolate) sourced from the Nordic countries to replace land animal by-products (i.e. blood meal and poultry by product meal) and soy protein concentrate.

Results show that the novel feed reduces greenhouse gas emissions of one kg of rainbow trout by around 63 %. Fish fed the experimental feed maintained the same growth and economic feed conversion 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 feed of the conventional feed. Feeding fish insects reared on plant-based waste streams from the food industry, increases the circularity and reduces emissions. However, the modelling choice that some feed inputs based on side streams with no economic value are free of environmental burden, has a strong influence on the results. Despite shorter transport distances no lower impact of transports could be found for the experimental feed due to the utilisation of more climate intensive transport means/modes. Further, the novel feed ingredients used in the study come from pilot or test scale production plants, with potential to further decrease emissions with optimised processing. At present, the available volumes of these feed inputs are limited which prevents a rapid large-scale shift of the aquaculture industry. Other sources of uncertainty include the fact that the FCR is based on a four-month growth trial which might not reflect a complete production cycle. This study indicates that there is a potential to reduce the carbon footprint of intensive aquaculture by using alternative protein sources, an important step that shows that it is worthwhile to continue expanding the analysis to cover also other environmental aspects to avoid shifting burdens between different types of environmental impact.

Published in

Mistra Food Futures Report
2023, number: 13
Publisher: Sveriges lantbruksuniversitet

SLU Authors

• Langeland, Markus

  • RISE Research Institutes of Sweden

UKÄ Subject classification

Environmental Sciences
Fish and Aquacultural Science

Publication identifier

• ISBN: 978-91-8046-821-3
• eISBN: 978-91-8046-822-0

Permanent link to this page (URI)

https://res.slu.se/id/publ/131850