From Waste to Resource: The Circular Economy of Aquaculture By-Products
One of the fundamental principles of a circular economy is that waste should be regarded not as an inevitable end point, but as a potential resource. In conventional production systems, materials are often extracted, transformed into products and ultimately discarded once their primary purpose has been fulfilled. Aquaculture provides an opportunity to challenge this model by recovering value from materials that would otherwise become waste.
Fish offal, shells and excess algal biomass are examples of materials that can be redirected into other productive uses. Seafood-processing waste, for example, contains valuable biological materials that can be transformed into products such as animal feed, fertilisers and biomaterials, reducing the environmental burden associated with disposal while creating additional economic value.¹ Rather than viewing these materials as secondary outputs, circular aquaculture systems can incorporate them into wider production networks.
Bivalve shells are particularly interesting in this respect. Shells are largely composed of calcium carbonate, meaning that the substantial quantities generated by shellfish aquaculture represent a potentially valuable source of mineral material. Morris et al. argue that aquaculture shells should be considered a valuable biomaterial rather than simply a nuisance waste product.² Recovered shell material can potentially be used in applications ranging from agriculture and construction to water treatment, reducing demand for newly extracted mineral resources.
Seaweed provides another example of how aquaculture can generate multiple forms of value from the same production system. When seaweed is integrated with aquaculture, it can absorb dissolved nutrients while producing additional biomass with potential applications in food, agriculture, biomaterials and other industries. Waters et al. further identify the potential for farmed seaweed to contribute to carbon sequestration and emerging carbon markets.³
The significance of this approach becomes clearer when these different outputs are considered as part of a connected system. Waste from one activity can become an input for another: shell material can become a source of calcium carbonate, organic residues can become fertiliser or feed ingredients, and seaweed biomass can provide both commercial products and environmental services. The objective is therefore not simply to reduce waste, but to redesign production so that fewer resources leave the system without generating further value.
This is where circular economics differs from conventional waste management. Recycling generally addresses what happens after a product has reached the end of its intended use. A circular system instead asks a more fundamental question: why should the material become waste in the first place?
For aquaculture, this distinction is particularly important. The profitability of many marine products can be constrained by relatively low prices for primary commodities. Creating additional revenue streams from by-products can therefore improve the economic resilience of an operation while simultaneously reducing its environmental footprint.
The most effective model may ultimately be one in which an aquaculture farm is not viewed as a facility producing a single commodity, but as a resource-generating system. Fish, shellfish and seaweed become the primary outputs, while nutrients, shells, organic residues and biomass are captured and redirected into secondary markets.
This approach does not make aquaculture automatically sustainable. The processing, transport and conversion of by-products still require energy and infrastructure, and markets must exist for recovered materials. Nevertheless, treating by-products as economic resources rather than waste creates an important foundation for a more circular marine economy.
The future of aquaculture may therefore depend not only on producing more from the sea, but on getting more value from everything that is already produced.
Citation List
- Z. Zhao, Y. Li and Z. Du, ‘Seafood Waste-Based Materials for Sustainable Food Packing: From Waste to Wealth’ (2022) Sustainability, 14, 16579.
- J. P. Morris, T. Backeljau and G. Chapelle, ‘Shells from aquaculture: a valuable biomaterial, not a nuisance waste product’ (2019) Reviews in Aquaculture, 11, pp. 42–57.
- T. Waters, R. Jones, H. Alleway, R. Gentry and A. Xu, Analysis of Farmed Seaweed Carbon Crediting and Novel Markets to Help Decarbonize Supply-Chains (The Nature Conservancy, 2023).
Bibliography
Morris, J. P., Backeljau, T. and Chapelle, G., ‘Shells from aquaculture: a valuable biomaterial, not a nuisance waste product’, Reviews in Aquaculture, 11 (2019), pp. 42–57.
Waters, T., Jones, R., Alleway, H., Gentry, R. and Xu, A., Analysis of Farmed Seaweed Carbon Crediting and Novel Markets to Help Decarbonize Supply-Chains (The Nature Conservancy, 2023).
Zhao, Z., Li, Y. and Du, Z., ‘Seafood Waste-Based Materials for Sustainable Food Packing: From Waste to Wealth’, Sustainability, 14 (2022), 16579.