Mapping the impacts of farmed Scottish salmon from a life cycle perspective

Abstract

Purpose The European Union relies on seafood imports to supply growing demand that European production has failed to meet. Politically motivated media reports have denigrated competing imports in favour of local production. While life cycle assessment (LCA) measures global impact of value chains, it often fails to contextualise them. Using LCA, this article takes farmed Scottish Atlantic salmon as a case study of Blocal^production to identify and map the contributions to global environmental impact. Methods Data on the Scottish salmon value chain were collected by structured survey from a large international feed mill, six farms and a major processor. Secondary data were collected from available literature on feed ingredients and background data from EcoInvent2.2. A mid-point CML2001 approach was adopted focussing on global warming potential (GWP), acidification potential (AP), eutrophication potential, ozone depletion potential, photo-chemical oxidation potential, consumptive water use and land use. Results were displayed as contribution analyses of materials and processes and mapped geographically using area plots. Results and discussion Far from being a Blocally^produced commodity, nearly 50% of the feed ingredients were sourced from South America and less than 25% originated in the UK.It was found that over 90% of the impact to farm-gate was embodied in feed, apart from eutrophication potential which was high at the farm from direct nitrogenous emissions into the marine environment. The majority of impacts do not occur in Scotland, particularly for land and water use, which occur at a more geographically significant level than GWP or AP, which are more global or regional impacts, respectively. High GWP emissions from vegetable-based ingredients were related to soil management and energy intensive processes such as wet milling to produce gluten from wheat and maize, sunflower and rapeseed oil processing. Conclusions The results show that in an age of globalised commodity trading, concerns around Blocal^production are often misleading. As consumers try to make more responsible purchase choices, they may be misled over the global impacts their choices are having. There are clearly trade-offs between different feed ingredients, especially regarding substitution of marine ingredients with those of vegetable origin. While marine ingredients perform comparatively well, they are highly limited, and biodiversity impacts of different ingredients are less clear and difficult to compare.

Comparing Life Cycle Assessment (LCA) of Salmonid Aquaculture Production Systems: Status and Perspectives

“…For example, in CML-IA, the EP characterization factors (based on Heijungs et al [68]) refer to phosphorus (kg PO4-e) without discerning marine and freshwater nutrient limitation, while ReCiPe expresses the same impacts based on nitrogen (kg N-e) and phosphorus (kg P-e) depending on the emissions medium [72]. In different studies, water dependence is also named water depletion [30], water use [29,59], freshwater footprint [32], and consumptive water use [55]. Land occupation is inconsistent in both naming and units between studies.…”

“…Land occupation is inconsistent in both naming and units between studies. It is alternatively referred to as agricultural land occupation [30], surface use [53], land use [54,55], and land competition [50,60], and is expressed in square meters per year [28][29][30]50,54,55,60] or square-meters [53] alternatively. Finally, biotic resource use is also called net primary production in about one-fifth of the studies [28,29,51,53,59] (see supplementary data, Section 3.1.1).…”

“…Most studies already expressed their results in this format. Six studies used different system boundary and FU combinations [35,36,48,52,55,58]. We performed a small system boundary adjustment of Ayer et al [52] by adding hatchery impacts using contribution analysis results from Pelletier et al [31].…”

“…Cradle-to-farm gate impacts of 1 t FU produced were available in Liu et al [35] and Ziegler et al [48] and part of the secondary results. Newton and Little [55], Silvenius et al [58], and Grönroos et al [36] adjusted impacts were obtained through personal communication with the authors. Grönroos et al [36] adjusted results differ significantly from the published results due to an inventory error discovered by the authors (Section 2.2.3, "adjustment calculations", supplementary data).…”

Emerging trends in aquaculture value chain research

“…One conspicuous gap that requires considerably more attention is the use of aquaculture related wastes and byproduct recovery. Aquaculture processors are already investing heavily in the technology and knowhow necessary to create further value these 'secondary' value chains, to the extent that the output of food fish may become of secondary importance by value in some cases (see for example Newton and Little 2017;Stevens et al 2018). To date, virtually no work has been done on the volume, value, structure, performance or conduct of these secondary chains.…”