‘Aquafeed 3.0’: creating a more resilient aquaculture industry with a circular bioeconomy framework

As aquaculture continues to grow, so does the requirement for environmentally sustainable and cost-effective aquafeed. With an expected increase in aquafeed demand, it is important (now more than ever) to investigate and utilize new aquafeed ingredients that do not deplete natural resources and, instead, may have positive impacts to help control climate change. Aquaculture has become the largest consumer of global fishmeal (FM) and fish oil (FO) production, accounting for 68% and 89%, respectively (Hua et al. 2019). At the same time, most modern aquafeed are now predominantly composed of terrestrial plant materials and animal by-products [in this issue, you can find a fascinating article describing how aquafeed have evolved and the consequent call for rethinking trophic levels in aquaculture policies (Cottrell et al. 2021)]. This puts heavy reliance on terrestrial agriculture products, which have their own sustainability issues, such as freshwater use, deforestation, areal footprint, pesticide and fertilizer use, irrigation and polluting runoff. Furthermore, the use of terrestrial crops in aquafeed directly compete with human food streams. Besides, many of the terrestrial plant ingredients present certain nutritional challenges for farmed aquatic species. Climate change can exacerbate the situation, hampering the ability to produce crops consistently, in extreme and increasingly unpredictable conditions, and jeopardizing the long-term sustainability of marine products harvesting. The supply, cost, environmental sustainability and social acceptability of raw materials for aquafeed are under threat. The direct consequences for aquafeed, and with a snowball effect, the consequences for global aquaculture economic viability, environmental sustainability and social license to operate are significant. As a result, the industry must develop innovative practices that involve conservation, restoration and/or remediation. This presents new opportunities for next-generation protein and lipid sources for aquafeed that will be more resilient and consistent, in our changing and seemingly unstable world. One such opportunity is the production of nutritional resources that are created through the circular bioeconomy. This encompasses the production of renewable biological resources and converting these resources and their by-products and waste streams into value-added products, such as food, feed, bio-based products and bioenergy. It is all about valorization – and keeping the value of biomass cascading. The extensive organic biomass and waste streams from agriculture, forestry, fisheries, food and feed and organic processing waste should be integrated into a circular, bioeconomy strategy. It also creates opportunities to link very different industries, which is a unique strength of the bioeconomy concept. This allows for greater diversification and resilience, with the ultimate goal of using renewable natural resources to achieve a sustainable balance in food production and ecological conservation. Of course, this demands innovations, new technologies, knowledge-based processes and new applications, as well as a cultural shift. Efforts towards a climate- and ecology-positive economy in aquafeed production will mean moving further away from traditional wild-harvested FM and FO and agricultural crops, shifting towards ingredients produced through the circular bioeconomy. This also has the potential to result in locally sourced aquafeed ingredients, which can reduce transport-related greenhouse gases (GHG) emissions and costs, fuel local economies, create new jobs and overall are more socially accepted and environmentally sustainable. From their infancy, the evolution of aquafeed from being mostly FM and FO-based, to become primarily terrestrial-based, which are the current aquafeed and could be termed ‘Aquafeed 2.0’, has occurred rapidly; essentially within the last 20 years (Cottrell et al. 2021). It is time now to conceive, plan and develop ‘Aquafeed 3.0’. We envisage that Aquafeed 3.0 will use ingredients produced through the circular bioeconomy, which can improve aquaculture's sustainability by reducing its environmental footprint in terms of water and land use, CO2 conversion, GHG emissions, nutrient recycling and wastewater remediation. Aquafeed 3.0 will be based on raw materials that are nutritionally superior and closer to the natural diet of many carnivorous aquatic species than the terrestrial plant and animal by-products currently being used. There are already several examples of new aquafeed ingredients that are produced through circular bioeconomy frameworks, such as insects, microbial single-celled organisms, seaweeds and fishery and aquaculture processing by-products. Moreover, we like to think that many others are just waiting to be discovered. Single-celled organisms, such as microalgae, yeasts, bacteria and fungal protists, can utilize environmentally sustainable nutrient media derived from waste streams and other industrial by-products. [For example, in this issue, an exciting and comprehensive report on a promising microalga suitable for large-scale production, Tetradesmus obliquus (from background taxonomical and morphological information to production, harvesting and processing methods, biochemical and nutritional composition and its environmental and industrial applications), is available (Oliveira et al. 2021)]. Some single-celled organisms can be cultivated in seawater on non-arable land, in land-based enclosed photobioreactor systems. They can utilize cellulosic sugars from industrial by-products, such as those resulting from the pulp and paper industry. Others can remediate wastewaters by utilizing up to 90% of nitrate, sulphate and phosphate and convert them into useful biomass that is rich in lipid, protein and carbohydrate. The resulting single-celled organism biomass products (e.g. meals and oils) can have superior, improvable, modifiable and tailorable, nutritional profiles compared with most terrestrial plant products currently used in aquafeed, mainly containing high levels of essential n − 3 LC-PUFA and essential amino acids. Many studies have evaluated dietary inclusion of various species of single-celled proteins and oils in aquafeed and have shown positive results (Tibbetts 2018). Similarly, cultured macroalgae (seaweeds) also have potential in aquafeed as, after appropriate biorefinery processes, novel raw materials or functional ingredients, with positive effects on gut health and improving innate immunity and resistance to stress and pathogens (Thépot et al. 2021) and can also help to mitigate eutrophication and climate change. [On this topic, in this issue, a remarkable article describing some critical challenges of the kelp aquaculture industry in China, the world's largest kelp cultivation and production sector, is available. Specifically, this review describes how the sector is suffering from declining germplasm diversity, degradation of agronomic traits, the presence of polluted environments, changing ocean conditions and increasing anthropological interference, for then concluding with a series of proposed strategies to tackle these challenges (Hu et al. 2021)]. Another example is insects and derived meals, which have shown a relatively good nutritional profile, feasibility of commercial-scale production, high feed conversion and non-competition with human food production. Successful use of insect meal as a partial or total replacement for FM in aquafeed has been documented in many aquatic species, and often with improved performance and health status when used to replace soybean products (Hua et al. 2019). Insect production has been shown to consume less land and water resources than most crops, and the feedstocks used to grow the insects can come from food waste. As such, this opportunity provides a perfect example of how the circular bioeconomy can result in more sustainable and nutritious aquafeed ingredients. Finally, innovations in achieving better and more efficient circularity within the seafood sector by recovering fishery and aquaculture by-products offer substantial promises for high-value nutrients in aquafeed and waste recovery. After fish processing, 50–70% of the by-products are deemed ‘inedible’, which is increasingly considered a practical solution to replace the use of wild-caught FM and FO. Currently, 20% of FM production is supplied through fishery by-products, and 10% is from aquaculture by-products (Hua et al. 2019). However, this is projected to rapidly increase with greater aquaculture production, which represents an enormous potential to increase FM and FO production volume from by-products. Aquaculture must move towards a new paradigm where the carbon footprint and lower impacts on the environment are equal to production and profitability. Aquafeed ingredients produced through a circular bioeconomy approach will allow for a new revolution, which we are hereto naming ‘Aquafeed 3.0’. Using a trophic level analogy, as described in this issue by Cottrell et al. (2021), we can say that in the last 20 years, when aquafeed evolved into ‘Aquafeed 2.0’, we have shifted our farmed carnivorous species to become far more omnivorous. We now must help the sector further evolve into scavengers, which are essential in any healthy ecosystem, but currently missing in the global food system, by achieving ‘Aquafeed 3.0’. This is the opportunity for sustainable and resilient aquaculture, in the face of a changing climate, constantly turbulent economies and rapidly evolving social dynamics and expectations, to produce healthy and nutritious seafood for all. We hope that the articles in this issue of Reviews in Aquaculture and the other scientific articles published by sector Journals will contribute to this evolution.

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