Introduction
Globally, aquaculture is the fastest growing agri-food sector and it is increasingly seen as the primary activity to meet the growing consumer demand for fish. Up to now, European seabass (sp. Dicentrarchus labrax) and Gilthead seabream (sp. Sparus aurata) are the most commonly farmed species in the Mediterranean Sea, with a production of 464,000 tons and USD 2.24 billion in 2019 (FAO, 2020). However, intensive fish farming, implies environmental concerns related to the consumption of feed, the emission of nutrients and organic compounds into the water and, sometimes, the consumption of pesticides and antibiotics for pest and disease control (le Feon et al., 2021). Developing sustainable aquaculture is a priority in the current economic and social context. Therefore, aquaculture production systems must change to improve environmental performance and decrease energy consumption. To achieve these objectives, a holistic perspective is needed considering the impacts generated by production, and Life Cycle Assessment (LCA) approach is considered the most suitable tool for analyzing such a wide spectrum. In this study, LCA was applied to assess the environmental impact related to Seabass and Seabream farming of an off-shore plant located in Central Italy.
Materials and method
The selected functional unit (i.e., the reference unit of the study to which all the inputs and outputs should be referred) was 1 ton of Seabass and 1 ton of Seabream at the fish farm gate. Moreover, the different feeds supplied were analysed and the impact of 1 ton of different feeds calculated. The system boundary includes the production of feed and other production factors consumed (e.g., fuel, electricity), the rearing operations and all the emissions related to the process (e.g., phosphorous and nitrogen emissions due to the metabolism of the fish during the entire production cycle). The inventory data was collected in a commercial aquaculture plant in Central Italy. Primary data refers to the consumption of different feeds based on the sizes of fish, energy and fuels while secondary data was used with regard to the emissions of N and P compounds from fish (Cho et al., 1991), fry production (Garcia Garcia et al., 2019) and feed composition (estimated with a centesimal analysis based on the content of proteins and fats). Background data about cages and other capital goods as well as about the component of the feed were retrieved from databases (Ecoinvent® and Agrifootprint). The environmental profile of the production system was analysed with the Recipe Midpoint (H) method, taking into account 12 different impact categories.
Results
For European Seabass and Gilthead Seabream, the environmental results, for most of the considered impact categories, showed that aquafeed is the main environmental hotspots. The species analysed show the same results as regards the analysis of contributions. For the Climate Change impact category, aquafeed impacts about 60% of the total impact, while for marine eutrophication the emissions of N compounds accounts for 95% of impact. Infrastructures have an high impact in the human carcinogenic toxicity (75%) and mineral resource scarcity (59%). Comparing the two species, Seabass has higher impacts in all impact categories than Seabream: this is mainly due to the higher FCR of Seabass than Seabream (respectively 2.4 and 1.9), which also results in higher emissions of nitrogen compounds per kg of fish produced. In addition, Seabass has a higher average mortality rate (20% vs 8% for Seabream): therefore, a greater number of fry is necessary to obtain the same production. Finally, the feeds that contain a greater quantity of fish meal and fish oil, supplied to smaller sized fish, have the highest impacts.
Conclusions
This study confirmed that aquafeeds management is the main responsible for most of the impacts. Measures that optimize the production and use of fish feed are necessary and can positively affect the environmental performances of aquaculture sectors. Similar results, both in absolute terms and in terms of relative contributions, are reported by other studies (Aubin et al., 2009; Abdou et al., 2017). To date, the large amount of protein and lipids required for fish growth is mainly provided by fishmeal and fish oil from freshly caught fish stocks. Therefore, it is essential to optimize and modify diet formulation as well as to study alternative feeding strategies in order to lower FCR. In addition, aquaculture requires a very high consumption of fossil fuels (both for the mobility of ships and for the supply of feed and fry); for this reason, following the example of the SIMTAP system developed during the project SIMTAP (Self-sufficient Integrated Multi-Trophic AquaPonic systems for improving food production sustainability and brackish water use and recycling), new diets characterized by limited transportation impacts and by the use of locally produced raw materials, combined with the maximization of the use of renewable energy (e.g. solar energy) and alternative protein sources (e.g. microalgae) can represent other effective impact mitigation strategies. Finally, besides the environmental performances also the economic and social ones should be evaluated for a more comprehensive assessment of the process sustainability
Acknowledgements
This study was conducted within the framework of PRIMA S2 2018 project SIMTAP. SIMTAP (https://www.simtap.eu/) is part of the PRIMA Programme supported by the European Union.
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