64 MARCH 2026 • WORLD AQUACULTURE • WWW.WAS.ORG is converted into biogas, primarily methane, that in turn is combusted in a generator to produce heat or electricity (Osipovs et al. 2021; Klein et al. 2024). The generated heat can regulate water temperature in recirculating aquaculture systems (RAS), while the electricity powers essential equipment like pumps and lights. This approach not only generates clean energy but also addresses the problem of waste disposal and reduces environmental pollution. Rio Fish in Kenya is a prime example of the practical application of the waste-toenergy concept in aquaculture. Water heating and cooling are among the most energy-intensive processes in aquaculture. Geothermal energy provides an effective solution by using the earth’s stable underground temperature to maintain optimal thermal stability, a factor which can greatly influence fish growth performance. A case study by Świątek (2025) demonstrated the successful integration of geothermal water in RAS to control temperature. The findings revealed optimal thermal stability for salmon growth and a substantial reduction in energy and operational costs. Sustainable Feed Innovations Following the shift towards sustainable energy, the next frontier in “greening aquaculture” is aquafeed systems, which are the cornerstone of production costs and environmental impacts. Aquafeed represents the largest expense in most forms of aquaculture and its production contributes significantly to environmental impacts. Reducing the dependence on raw ingredients sourced from distant regions is a crucial aspect of sustainability in many countries. To this end, researchers and producers are investigating locally available, low-cost alternative ingredients. There is a global trend towards recycling food and agricultural waste into sustainable protein products. Through technology like microbial processing or fermentation, low-value wastes can be transformed into high-value feed ingredients, increasing protein content and digestibility. These innovations have a dual benefit: providing a cost-effective and locally sourced alternative to imported feed resources, while converting waste into useful resources supporting the long-term circular economy. Among the promising interventions in the field of sustainable protein production are gaseous fermentation projects, which utilize harmful gases as protein sources. For instance, Aerbio converts carbon dioxide into high value protein components while Unibio has developed advanced fermentation approaches to produce protein from biogas and carbon-rich substrates. Such initiatives show how science can transform greenhouse gases into sources of useful feed ingredients which in the end will reduce environmental impacts and lower production costs. Numerous studies, including those by Kalaiselvan et al. (2025) leading to environmental and economic consequences. Repurposing food industry by-products for animal feed can reduce waste, lower feed costs, and improve sustainability in aquaculture. Solid-state fermentation (SSF and Tropea et al. (2021) leading to environmental and economic consequences. Repurposing food industry by-products for animal feed can reduce waste, lower feed costs, and improve sustainability in aquaculture. Solid-state fermentation (SSF support the concept of converting waste into single-cell protein, which reduces environmental burdens and helps secure future feed sustainability. The use of black soldier fly larvae (Hermetia illucens) as a sustainable protein source is a transformative trend in the aquafeed industry. Black soldier fly larvae can consume organic waste and are an integral tool of bioconversion within the context of a circular economy approach through upcycling wastes into a high-value protein source for animal feed. In addition to their protein content, the larvae have a good profile of fatty acids which contribute to the immunity, health, and growth of organisms being cultured. From this perspective, this technology aligns with the goal of “ZeroWaste Aquaculture” by closing the nutrient cycle in an ecologically and economically sustainable method. Circa Biotech has adopted this technology to produce high quality protein meal from BSFL, providing a sustainable and efficient alternative to traditionally used protein sources. Microalgae offer another promising alternative for sustainable feed production. They contain up to 70% protein with a complete profile of essential amino acids (Eilam et al. 2023), as well as concentrated omega-3 essential fatty acids that are crucial for fish growth and overall health. Their cultivation does not require extensive agricultural land or large water resources, making them advantageous in arid regions facing water scarcity. In the Arab region several initiatives such as Algafeed have begun producing microalgae-based feed to support local marine fish farming industries while also improving regional nutritional security. Waste Management and Water Quality Aquaculture sustainability also depends on the ways that waste is managed and how water quality is maintained. Low-cost FIGURE 2. AI-generated illustration showing the circular economy in sustainable aquaculture. The integration of renewable energy, sustainable feed innovation, and waste recycling closes the production loop, supporting farmer empowerment, food security, and community stability.
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