For decades, the Blue Economy has inspired governments, industries, and researchers to rethink humanity’s relationship with the oceans. By promoting sustainable fisheries, aquaculture, maritime transport, offshore renewable energy, coastal tourism, and marine biotechnology, it has demonstrated that economic growth and environmental stewardship can coexist [1–3]. Today, the Blue Economy contributes significantly to global development while supporting millions of jobs and generating substantial economic value across coastal regions. Yet, despite its remarkable achievements, the concept is reaching a new crossroads. The environmental challenges of the twenty-first century extend well beyond the sustainable exploitation of marine resources. They now encompass water scarcity, climate change, energy security, critical raw material supply, marine pollution, and ecosystem degradation issues that cannot be addressed independently.
Every day, coastal infrastructure around the world produces enormous quantities of freshwater, renewable electricity, treated wastewater, concentrated desalination brine, industrial gases, organic residues, and marine biomass. Ironically, these valuable resources continue to be managed as separate outputs of independent sectors. Desalination plants focus on freshwater production while discarding concentrated brine. Wastewater treatment facilities remove pollutants before discharge. Renewable energy installations generate electricity without systematic integration with water infrastructure. Green hydrogen projects are often planned independently from desalination systems, despite their dependence on high-quality water. This fragmented approach reflects the industrial logic of the twentieth century, where each facility was designed to optimize a single objective. It is becoming increasingly inadequate for addressing the interconnected challenges of climate resilience, resource efficiency, and sustainable development [4,5].
The urgency of adopting a more integrated approach is reflected in global trends. Nearly 40% of the world’s population lives within 100 kilometres of the coast, where urbanization, industrial development, tourism, agriculture, and ecosystem conservation compete for increasingly limited water and energy resources [2]. At the same time, freshwater demand is projected to increase by 20–30% by 2050, while climate change is intensifying droughts, sea-level rise, and coastal ecosystem degradation [2,13]. These converging pressures highlight a simple reality: future coastal infrastructure must simultaneously deliver water security, renewable energy, resource recovery, and ecosystem resilience rather than addressing each challenge separately.
The next evolution of the Blue Economy will therefore not be driven by a single breakthrough technology. Instead, it will emerge from the intelligent integration of existing technologies into regenerative coastal systems. The future unit of innovation is no longer the desalination plant, the wastewater treatment facility, the hydrogen electrolyser, or the aquaculture farm. It is the coastal system itself.
This emerging paradigm may be described as Integrated Circular Coastal Systems (ICCS); a framework in which freshwater, renewable energy, materials, nutrients, biological resources, and ecosystem services continuously circulate through interconnected infrastructures that maximize resource efficiency while minimizing environmental impacts. Unlike conventional coastal development, where individual sectors operate independently, ICCS promotes industrial symbiosis, whereby the output of one process becomes the input of another. Wastewater becomes a water resource. Desalination brine becomes a source of strategic minerals. Organic residues become bioenergy or fertilizers. Renewable electricity simultaneously powers desalination, electrolysis, and resource recovery processes. The objective is no longer simply to reduce environmental impacts but to create regenerative coastal economies that continuously recover value from every resource stream.
Few technologies illustrate this transformation better than seawater desalination. Once considered an expensive solution reserved for extremely water-scarce regions, desalination has evolved into one of the world’s fastest-growing sources of freshwater. More than 22,000 desalination plants currently produce over 100 million cubic metres of freshwater every day, supplying drinking water to hundreds of millions of people worldwide [6]. Continuous improvements in reverse osmosis membranes, energy recovery devices, and process optimization have significantly reduced both energy consumption and operating costs over the past two decades [7]. As renewable electricity becomes increasingly available, desalination is progressively evolving into a lower-carbon solution capable of strengthening long-term water security.
However, desalination also exposes the limitations of linear infrastructure. Conventional plants produce two outputs: freshwater and concentrated brine. While freshwater is highly valued, the brine is generally discharged back into the marine environment, where localized increases in salinity may affect sensitive ecosystems [6]. From the perspective of a Circular Blue Economy, this represents an untapped opportunity rather than an unavoidable waste stream. Brine contains commercially valuable elements including sodium, magnesium, potassium, calcium, bromine, and trace quantities of lithium and other strategic minerals that are becoming increasingly important for batteries, renewable energy technologies, and advanced manufacturing [6,8].
Historically, desalination facilities have been evaluated almost exclusively according to freshwater production and operational efficiency. Future plants should instead be assessed according to the total value they generate. Freshwater production, mineral recovery, renewable energy integration, recovered industrial gases, avoided greenhouse gas emissions, and ecosystem protection should all become indicators of performance. In a truly circular coastal economy, success is measured not simply by the volume of freshwater produced, but by the overall value created from every cubic metre of seawater processed.
Green hydrogen represents another cornerstone of this new generation of coastal systems. As countries accelerate their transition toward carbon neutrality, hydrogen produced through renewable-powered electrolysis is emerging as one of the most promising solutions for decarbonizing sectors that are difficult to electrify, including steel production, fertilizers, shipping, aviation, and heavy industry [9,10]. While discussions often focus on renewable electricity, much less attention has been paid to the water required for electrolysis. Producing one kilogram of hydrogen requires approximately nine litres of highly purified water. Although this volume is modest compared with agricultural or municipal demand, reliable access to high-quality water becomes essential as hydrogen production expands to industrial scales [9].
Rather than considering this requirement as a constraint, coastal regions should view it as an opportunity. Renewable-powered desalination can provide a sustainable source of ultrapure water while simultaneously strengthening water security for surrounding communities. Solar and wind electricity can power both reverse osmosis systems and electrolyzers, creating integrated facilities capable of producing freshwater and green hydrogen from the same renewable energy source. Even the oxygen generated during electrolysis, often regarded as a secondary product, can be recovered for hospitals, aquaculture, wastewater treatment, and industrial applications, further improving overall resource efficiency [9,10]. Instead of functioning as isolated facilities, desalination plants and hydrogen production units become complementary components of a single circular coastal system.
This transformation also reflects a broader evolution in industrial design. Coastal infrastructure should no longer be conceived as facilities delivering one product, but as multi-resource platforms capable of simultaneously producing water, clean energy, recovered materials, industrial gases, and environmental services. Such integration increases economic resilience while reducing waste generation and greenhouse gas emissions.
Digital technologies will play a decisive role in enabling this transition. Artificial intelligence can optimize membrane operation, predict fouling before it occurs, and reduce electricity consumption in desalination plants. Digital twins allow engineers to simulate the behaviour of integrated coastal infrastructures under different operating and climate scenarios, while satellite observations and remote sensing technologies provide continuous information on water quality, coastal erosion, and ecosystem health. Together, these technologies create the intelligence necessary to coordinate increasingly complex interactions between water, energy, materials, and ecosystems, transforming conventional infrastructure into adaptive and resilient resource systems.
The principles of circularity extend well beyond desalination and hydrogen production. Around the world, wastewater treatment plants are progressively evolving into Water Resource Recovery Facilities (WRRFs) capable of generating reclaimed water, renewable biogas, phosphorus, nitrogen fertilizers, and biosolids rather than simply treating wastewater before discharge [11]. This transition represents one of the clearest examples of the circular economy in practice. Instead of considering wastewater as a liability, it becomes an alternative source of freshwater, nutrients, renewable energy, and industrial raw materials.
The same philosophy applies to fisheries, aquaculture, and marine biotechnology. Organic residues generated by fish processing industries can be converted into animal feed, biofertilizers, collagen, chitosan, and other high-value bioproducts. Marine algae are increasingly recognized as versatile biological resources capable of producing pharmaceuticals, cosmetics, functional foods, biodegradable plastics, biofuels, and sustainable aviation fuels [12]. Their ability to absorb nutrients and carbon dioxide further strengthens their role within circular coastal systems by simultaneously contributing to wastewater polishing, carbon sequestration, and biomass production.
Similarly, desalination brine is gradually evolving from an environmental challenge into an economic opportunity. Recent advances in selective membranes, electrodialysis, membrane distillation, electrochemical separation, adsorption technologies, and advanced crystallization have significantly improved the feasibility of recovering valuable compounds from concentrated saline streams [8]. Magnesium, bromine, potassium, sodium salts, and, potentially, lithium are increasingly attracting attention as strategic resources needed for batteries, renewable energy technologies, lightweight alloys, pharmaceuticals, and specialty chemicals. Although several recovery technologies remain at pilot scale, they illustrate a profound change in perspective: future desalination plants may become integrated mineral production facilities rather than simple freshwater factories.
Perhaps the most significant implication of this emerging paradigm is that coastal competitiveness will increasingly depend on resource circularity rather than resource abundance alone. Regions capable of recovering materials, reusing water, integrating renewable energy, restoring ecosystems, and creating industrial symbiosis will enjoy substantial economic and environmental advantages over those relying on conventional linear infrastructure. Competitive coastal economies of the future will therefore not necessarily be those endowed with the greatest natural resources, but those managing them most intelligently.
This systems perspective also changes how success should be measured. Traditional performance indicators such as cubic metres of freshwater produced, megawatts generated, or tonnes of hydrogen exported, capture only part of the value created by coastal infrastructure. Integrated circular coastal systems require broader indicators that include water reuse rates, renewable energy integration, resource recovery efficiency, avoided carbon emissions, ecosystem restoration, biodiversity protection, and economic value generated from recovered materials. Such multidimensional evaluation better reflects the true contribution of circular infrastructure to sustainable development.
Increasingly, the objective is no longer to optimize individual facilities but to optimize the interactions among them. Water supports energy production. Energy enables desalination. Brine becomes a source of minerals. Wastewater supplies irrigation and industry. Organic residues produce renewable energy and fertilizers. Marine ecosystems provide carbon sequestration, biodiversity, fisheries, and coastal protection. Every resource flow reinforces another, creating a regenerative network that is significantly more resilient than isolated infrastructure.
The Mediterranean region is uniquely positioned to become a global laboratory for this new model of coastal development. Although the Mediterranean Sea represents less than 1% of the world’s ocean surface, it hosts nearly 10% of global marine biodiversity while supporting more than 500 million people along its coastline [13]. At the same time, the region is recognized as one of the world’s climate change hotspots, warming faster than the global average and facing increasing water scarcity, coastal erosion, biodiversity loss, and growing competition among agriculture, industry, tourism, and urban development for limited natural resources [13]. These interconnected challenges cannot be solved through isolated sectoral policies. They require integrated solutions that simultaneously strengthen water security, accelerate the energy transition, recover valuable resources, and restore coastal ecosystems.
This is precisely where Integrated Circular Coastal Systems can make a transformative contribution. Rather than planning desalination plants, wastewater treatment facilities, renewable energy projects, hydrogen hubs, ports, and industrial zones independently, coastal territories should be designed as interconnected resource systems where water, energy, materials, nutrients, and ecosystem services circulate continuously. Such an approach increases resource productivity while reducing environmental pressures and strengthening climate resilience.
Among Mediterranean countries, Algeria possesses exceptional assets to pioneer this transition. With more than 1,600 km of coastline, one of the highest solar irradiation levels in the world, expanding seawater desalination infrastructure, ambitious renewable energy programmes, and growing interest in green hydrogen exports, the country has many of the ingredients required to develop integrated circular coastal systems. Rather than viewing desalination simply as a source of drinking water, Algeria has the opportunity to transform future plants into multifunctional facilities producing freshwater, ultrapure water for electrolysis, recovered minerals, industrial salts, oxygen, and valuable by-products. Coupled with wastewater reuse, marine biotechnology, and ecosystem restoration, such infrastructure could significantly improve both environmental sustainability and economic competitiveness.
This integrated vision is fully aligned with the Sustainable Development Goals, particularly those related to clean water (SDG 6), affordable and clean energy (SDG 7), sustainable industry (SDG 9), sustainable cities (SDG 11), responsible consumption and production (SDG 12), climate action (SDG 13), and life below water (SDG 14) [2]. It also complements emerging international strategies promoting circular economy principles, industrial symbiosis, nature-based solutions, and low-carbon development pathways [14,15].
However, achieving this transition requires more than technological innovation. It demands new governance models capable of breaking down institutional barriers between water authorities, energy agencies, environmental regulators, industrial operators, and coastal planners. Future investment strategies should encourage projects that maximize resource synergies rather than optimizing individual sectors in isolation. Research institutions and universities also have an essential role to play by developing interdisciplinary knowledge that bridges engineering, environmental science, economics, ecology, and public policy.
Ultimately, the Circular Blue Economy should not be understood simply as the application of circular economy principles to marine sectors. It represents a broader transformation in how coastal territories are conceived and managed. The objective is no longer merely to reduce environmental impacts but to create regenerative systems in which every drop of water, every unit of renewable energy, every kilogram of recovered material, and every ecosystem service contributes to long-term resilience and prosperity.
The Blue Economy has already transformed our understanding of sustainable ocean development. Its next evolution should move beyond the sustainable exploitation of marine resources toward the intelligent integration of coastal systems. Future competitiveness will no longer depend solely on access to natural resources but on the capacity to circulate them efficiently through interconnected infrastructures.
The twentieth century built coastal infrastructure to extract resources from the sea. The twenty-first century must build coastal systems that regenerate them. The future of coastal development will not be defined by isolated desalination plants, hydrogen facilities, wastewater treatment plants, or renewable energy projects, but by the intelligence with which these systems interact. The greatest wealth of the oceans is no longer simply what they contain, it is the capacity of coastal societies to circulate water, energy, materials, nutrients, and ecosystem services within resilient and regenerative systems. This is the true promise of the next generation of the Blue Economy.
References
[1] European Commission. The EU Blue Economy Report 2025. Luxembourg: Publications Office of the European Union; 2025.
[2] United Nations. Transforming Our World: The 2030 Agenda for Sustainable Development. New York: United Nations; 2015.
[3] OECD. The Ocean Economy to 2050. Paris: OECD Publishing; 2016.
[4] Geissdoerfer M, Savaget P, Bocken NMP, Hultink EJ. The Circular Economy – A new sustainability paradigm? Journal of Cleaner Production. 2017;143:757–768.
[5] Ellen MacArthur Foundation. Completing the Picture: How the Circular Economy Tackles Climate Change. Cowes, UK; 2019.
[6] Jones E, Qadir M, van Vliet MTH, Smakhtin V, Kang SM. The state of desalination and brine production: A global outlook. Science of the Total Environment. 2019;657:1343–1356. https://doi.org/10.1016/j.scitotenv.2018.12.076
[7] Elimelech M, Phillip WA. The Future of Seawater Desalination: Energy, Technology, and the Environment. Science. 2011;333(6043):712–717. https://doi.org/10.1126/science.1200488
[8] Panagopoulos A. Recent advances in desalination brine management and resource recovery: A review. Desalination. 2024. (Veuillez vérifier le volume, les pages et le DOI correspondant à l’article exact retenu.)
[9] International Energy Agency (IEA). Global Hydrogen Review 2024. Paris: IEA; 2024.
[10] International Renewable Energy Agency (IRENA). Geopolitics of the Energy Transition: Green Hydrogen. Abu Dhabi: IRENA; 2022.
[11] International Water Association (IWA). The Resource Recovery from Water Cluster. London: IWA; 2023.
[12] UNESCO. The United Nations Decade of Ocean Science for Sustainable Development (2021–2030). Paris: UNESCO; 2021.
[13] MedECC. Climate and Environmental Change in the Mediterranean Basin: Current Situation and Risks for the Future. First Mediterranean Assessment Report. Marseille: UNEP/MAP; 2020.
[14] United Nations Environment Programme (UNEP). Turning the Tide: Circular Economy Solutions for Oceans. Nairobi: UNEP; 2023.
[5] World Bank. The Potential of the Blue Economy: Increasing Long-term Benefits of the Sustainable Use of Marine Resources for Small Island Developing States and Coastal Countries. Washington, DC: World Bank; 2017.
