UNLOCKING THE WIDER POTENTIAL OF AQUACULTURE IN CIRCULAR FOOD SYSTEMS IN EUROPE

Introduction

Aquaculture is a vital food source around the globe, playing an important role in future food systems, by providing nutrients to the human diet. Yet, its potential to upcycle biomass and contribute to nutrient supply in circular food systems remains largely unstudied. Circular food systems are seen as a promising way forward to reduce the environmental impacts of food systems. A key principle of circular food systems is using biomass effectively by prioritising it as food for humans. Farm animals, including aquaculture species, should consume resources that are inedible for humans, such as grass, food waste and by-products from crops, livestock and fisheries. The availability of these so called low-opportunity-cost feeds (LCF) may constrain aquaculture growth. Aquaculture species vary in their ability to upcycle LCF into food, and the implications for nutrient supply in food systems are unclear. In this study, we provide insight into 1) what nutrients aquaculture can supply to the human diet, 2) how much fish can be produced when animals are fed exclusively with LCF, and 3) which LCF can be recycled into fish feed. Answering these questions allows the quantification of how much aquaculture is needed in circular food systems, and therefore, the discussion of the space required for aquaculture.

Methods

We extended the resource-allocation models of van Hal et al. (2019) and van Selm et al. (2022) to develop FEEDSOM (FEED Systems Optimization Model). FEEDSOM is a linear programming optimization model that allocates LCF across livestock and aquaculture systems to meet human nutrient requirements in Europe (EU-27 plus the United Kingdom, Iceland, and Norway). Livestock and aquaculture species were fed only on LCF. Capture fisheries are represented by the average landings of the twenty most caught species in Europe (2000-2020). Aquaculture is represented by Atlantic salmon and European seabass (carnivorous species) and common carp (omnivorous freshwater species). The model provides insights in how animal-sourced food can complement plant-sourced foods to supply nutrients, including protein, vitamin B12, calcium, and the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The objective of FEEDSOM was to maximise the number of people whose nutritional requirements can be met. We compared a baseline scenario, where aquaculture and fisheries are limited to current production and consumption (Reference), with two alternative scenarios: 1) FarmMore: expanding aquaculture 2) EatMore: all food grade fish is consumed and edible yields are extended.

Results and Discussion

Meeting the nutrient requirements while animals are fed exclusively with LCF resulted in 18 grams of fish per capita per day in the EatMore scenario, which is lower than the EAT-Lancet recommendations (28 g/d) (Willett et al., 2019). Expanding aquaculture increased fish consumption to 31 g/d, but at the cost of reduced livestock production. The carnivorous species, Atlantic salmon and European seabass, were fed high quality animal by-products, such as fishmeal, blood meal and by-product meal. Carp were fed low-quality animal by-products, such as meat and bone meal, and high-quality plant products, such as oil crop meal.

In this study, EPA/DHA were the limiting nutrients and the main driver of aquaculture production. Carnivorous aquaculture species can play an important role in circular food systems by upcycling EPA/DHA from fisheries by-products. However, the dependence of carnivorous aquaculture species on these limited resources limits their capacity to expand production. In contrast, omnivorous aquaculture species do not rely on fisheries inputs to supply EPA/DHA, but their overall contribution to EPA/DHA supply is relatively low.

Under current aquaculture production and consumption, we cannot supply enough EPA/DHA to meet the European nutrient requirements. To reduce this nutrient gap, we could increase aquaculture production (Figure 1, FarmMore scenario). However, expanding aquaculture should not be the priority, as it requires more LCF, production area, and increases environmental pressure. A more efficient strategy is to eat more edible parts of the fish (Figure 1, EatMore scenario). This approach could meet European nutrient requirement, including EPA/DHA, while also producing enough animal-sourced nutrients to help feed an additional 118 million people outside Europe. Figure 1 Contribution of aquaculture and fisheries to nutrient supply in circular food systems in Europe in the Reference, EatMore, and FarmMore scenarios using the Feed Optimisation Model (FEEDSOM). Arrows indicate biomass flows. LCF: low-opportunity-cost feed; EPA: eicosapentaenoic acid; DHA: docosahexaenoic acid

References van Hal, O. van, de Boer, I. J. M., Muller, A., Vries, S. de, Erb, K. H., Schader, C., Gerrits, W. J. J., & Zanten, H. H. E. van. (2019). Upcycling food leftovers and grass resources through livestock: Impact of livestock system and productivity. Journal of Cleaner Production, 219, 485–496. https://doi.org/10.1016/j.jclepro.2019.01.329 van Selm, B. van, Frehner, A., Boer, I. J. M. de, van Hal, O., Hijbeek, R., Ittersum, M. K. van, Talsma, E. F., Lesschen, J. P., Hendriks, C. M. J., Herrero, M., & Zanten, H. H. E. van. (2022). Circularity in animal production requires a change in the EAT-Lancet diet in Europe. Nature Food, 3(1), 66–73. https://doi.org/10.1038/s43016-021-00425-3

Willett, W., Rockström, J., Loken, B., Springmann, M., Lang, T., Vermeulen, S., Garnett, T., Tilman, D., DeClerck, F., Wood, A., Jonell, M., Clark, M., Gordon, L. J., Fanzo, J., Hawkes, C., Zurayk, R., Rivera, J. A., Vries, W. D., Sibanda, L. M., … Murray, C. J. L. (2019). Food in the Anthropocene: The EAT–Lancet Commission on healthy diets from sustainable food systems. The Lancet, 393(10170), 447–492. https://doi.org/10.1016/S0140-6736(18)31788-4