Footprint cohesion and prevalence of environmental impact categories in blue mussel aquaculture life cycle assessments

Aquaculture is promoted as a solution for strengthening food security. Non-fed organisms like blue mussels have gained interest as feed is a frequent hotspot in aquaculture. In this literature review, all published studies on environmental footprint evaluations with life cycle assessments (LCA) on blue mussel aquaculture, was assessed. Through harmonisation, the studies were enabled numerical comparison of the environmental footprints. It was found that blue mussel aquaculture LCA most frequently study some impact categories, resulting in an average global warming potential of 263 ± 179 (range 9.52 - 627) kg CO 2 eq.; eutrophication potential of 0.13 ± 0.33 (range -0.89 – 0.44) kg PO 4 eq.; and acidification potential of 2.072 ± 1.641 (range 0.71 – 6.5) kg SO 2 eq. per ton whole mussel. Consequently, significant gaps exist in several other impact categories, with some impact estimates varying by factor of thousand between the highest and lowest. Some aspects were found to deviate between the studies like how to handle carbon sequestration in the shell and bioremediation of nitrogen and phosphorous. The most analysed production method was variations of longlines; the most used life cycle impact assessment method was CML; and the most evaluated species was M. galloprovincialis . Many footprints were higher than previously assumed, but is still lower than many alternative food products. Future research should focus on establishing category rules or sector-wide agreements to address specific challenges, such as remediation of nutrients and carbon. Additionally, expanding the range of impact categories evaluated will help distinguish differences across case studies. • Carbon-, eutrophication- and acidification emissions was most commonly assessed • Discrepancies in evaluation of bioremediation and carbon sequestration • Several impact categories are sparsely used and unevenly included across studies • Most footprints were higher than previously assumed • High impacting inputs varied from electricity and diesel to capital goods