Assessing the potential environmental impacts of land-based salmon farming in Iceland through life cycle assessment

Salmon farming has a low feed conversion ratio and provides high-quality protein with relatively low environmental input. In Iceland, production is currently 45,000 t annually and is projected to reach 245,000 t by 2033, over 30 % of which is expected from land-based systems. This study assessed the potential environmental impacts of land-based Atlantic salmon farming using Life Cycle Assessment (LCA), with a functional unit of 1 t of salmon produced in land-based farms in Iceland in 2021. A hypothetical scenario investigated the avoided environmental burdens of utilizing the salmon manure as fertilizer based solely on its nitrogen, phosphorus, and potassium content, instead of producing synthetic fertilizer. In addition, a sensitivity analysis tested four electricity mix scenarios: the default Ecoinvent Icelandic electricity mix (Scenario 0), an LCA-based Icelandic energy mix (Scenario 1), the residual mix accounting for Guarantees of Origin (GOs) certificates (Scenario 2), and the Ecoinvent European mix (Scenario 3). For Scenario 0, impacts per functional unit were: 1.4 t CO 2 eq (Global Warming Potential), 8 kg SO 2 eq (Terrestrial Acidification), 0.6 kg P eq (Freshwater Eutrophication), 582 m 2 a crop eq (Land Use), and 8659 m 3 world eq (Water Scarcity Footprint). These results reflect relatively low environmental burdens compared to similar studies in other countries, largely due to Iceland's renewable energy. However, results from scenario 3 in the sensitivity analysis led to a GWP increase by 377 %, due to its large fossil-based composition. These results stress the importance of energy sourcing in shaping environmental outcomes and can guide impact reduction strategies for future land-based salmon farming in Iceland. • Iceland land-based salmon shows lower environmental impacts than studies overseas. • Feed production is an environmental hotspot in land-based salmon farming in Iceland. • Using salmon manure as fertilizer may avoid certain impacts of synthetic production. • Transparent LCI data, including energy mix and GOs, improves impact accountability.