Introduction
The FAO Committee on Fisheries stressed the increasingly key role of aquaculture in fish production for human nutrition and poverty alleviation. Its contribution to world fish production has reached 46% in 2016-2018 (FAO, 2020). Indeed, aquaculture is projected to be the prime source of seafood by 2030, as demand grows from the global middle class and wild capture fisheries approach their maximum take.
Therefore, there is a need to ensure a more sustainable aquaculture development to mitigate the environmental impacts linked to this growth. Considering that the feed production accounts for up to 60% of the total environmental impact linked to an aquaculture product (Cidad et al., 2021), efforts should be focused on reducing the impact generated on that stage. On feed production, animal feed ingredients, such as fish meal or fish oil contribute most to the impacts (up to 60%), followed by the plant-based ingredients as soybean and corn gluten (33%). Thus, more sustainable feed ingredients appear as valuable alternatives in order to reduce significantly the overall environmental impact of aquaculture products. This solution will also reduce the dependence on marine resources (Turchini et al. 2012), as 83% of fish oil and 65% of fish meal annually produced is assigned to aquafeeds (Tacon et al. 2008).
Within this framework, LIFE BREWERY project has demonstrated the environmental benefits of valorising spent grains and yeast produced by the brewery industry, as alternative ingredients for aquaculture feeds. For that purpose, a comparative Life Cycle Assessment (LCA) has been performed following the ISO 14040:2006 specifications.
Methodology
To identify, quantify and compare environmental impacts linked to different alternatives of aquaculture feeds, the LCA method appears as an internationally recognized methodology. According to the ISO 14040:2006, the method consists of 4 steps i) Goal and Scope definition; ii) Life Cycle Inventory, iii) Life Cycle Impact Assessment and iv) Interpretation. The steps are not simply sequential; LCA is an iterative technique that allows to be increased the level of detail in successive iterations.
Results and discussion
Step 1. Goal and scope definition
The goal of the study is to compare 3 different aquaculture feeds in order to assess potential environmental improvement of replacing current aquafeeds ingredients by brewers’ by-products: spent grains and yeast. The functional unit of this study is 1 ton of aquafeed. The system boundary for the aquafeeds considers the collection and manufacturing of conventional and valorised feed ingredients, the transportation to the feed mill and to the final users.
Step 2. Life Cycle Inventory
The aquafeeds analysed are a conventional feed (control) and two feeds including 15% and 20% of brewers´ spent grains (BSG) and yeast (BY) meal, respectively. The data of feeds formulation and the valorisation process of brewery by-products was obtained from the demonstration trials performed during the LIFE BREWERY project (San Martin et al. 2020). The inventory data for the conventional feed ingredients has been obtained from the Ecoinvent 3.5 and Agrifootprint databases. SimaPro 9 software has been used for the assessment. It is important to highlight that the proposed aquafeed alternatives have been tested and validated with 2 aquaculture fish species: Sparus aurata, and Oncorhynchus mykiss, as models of a Mediterranean and freshwater specie, respectively (Nazzaro et al. 2021).
Step 3. Life Cycle Impact Assessment
Climate change, particulate matter, terrestrial and freshwater acidification, land use, eutrophication terrestrial and water scarcity categories are the most representative environmental impacts of the activity for the aquafeed production. In all the selected impact categories, a decrease is observed when comparing the control feed with the two alternatives. Specially, in land use (BSG:25% and BY:32%) and water scarcity (BSG:24% and BY:42%) due to the avoided animal and plant-based ingredients production. In contrast, a 6% reduction is shown in climate change in both new aquafeeds.
Step 4. Interpretation
Environmental impact assessment determined that the proposed aquaculture feeds including brewers´ by-products appear as a sustainable alternative for reducing the impact linked to Mediterranean and freshwater aquaculture.
Conclusion
The LCA of aquafeeds have proved that replacing 15-20% of animal and plant-based ingredients with brewers´ by-products could reduce environmental impacts and obtain a more sustainable feed solution for fish aquaculture world.
Acknowledge
This project is co-funded by LIFE European Environment Programme (LIFE16 ENV/ES7000160), which is the EU’s financial instrument supporting environmental, nature conservation and climate action projects throughout the EU.
References
A.G.J. Tacon, M. Metian. 2008. Global overview on the use of fish meal and fish oil in industrially compounded aquafeeds: Trends and futures prospects. Aquaculture 285:146–158.
FAO. 2020. The State of World Fisheries and Aquaculture 2020. Sustainability in action. Rome. https://doi.org/10.4060/ca9229en
G. Turchini, W.K. Ng, D.R. Tocher. 2012. Fish oil replacement and alternative lipid sources in Aquaculture feeds. CRC Press, Taylor & Francis Group, 551 pp.
D. San Martin, M. Orive, B. Iñarra, J. Castelo, A. Estévez, J. Nazzaro, I. Iloro, F. Elortza, J. Zufía. 2020. Brewers’ spent yeast and grain protein hydrolysates as second- generation feedstuff for aquaculture feed. Waste Biomass Valoriz. https://doi.org/101007/s12649-020-01145-8
J. Nazzaro, D. San Martin, A.M. Perez-Vendrell, L. Padrell, B. Iñarra, M. Orive, A. Estévez. 2021. Apparent digestibility coefficients of brewer’s by-products used in feeds for rainbow trout (Oncorhynchus mykiss) and gilthead seabream (Sparus aurata). Aquaculture 530: 735796
M. Cidad, S. Ramos. 2020. Environmental footprint of seabass production in the Mediterranean Sea. Oral in Aquaculture Europe 2020 conference, Virtual.