The Role of Scrap Metal in Sustainable Desalination Plants

As freshwater scarcity becomes one of the most pressing global challenges of the 21st century, desalination—the process of converting seawater into potable water—has emerged not just as an option but as a lifeline for many nations. From Middle Eastern mega-cities to arid coastal towns in California and northern Africa, the demand for desalination is skyrocketing.

However, while desalination is solving one environmental crisis, it risks worsening another. Traditional desalination plants are notoriously resource-intensive. They consume massive amounts of energy and often generate saline effluent—otherwise known as brine—that, if not managed correctly, can harm marine ecosystems.

Enter a new wave of innovation: integrating principles of the circular economy into desalination plant design. At its core, this approach focuses on reducing reliance on virgin resources and minimizing environmental impact from both construction and operation. One promising, yet often overlooked component in this transformation is the strategic use of scrap metal—specifically recycled copper, steel, and aluminum.

This article explores how recycled metals can redefine the sustainability and scalability of desalination technologies, from infrastructure development to brine treatment systems. We’ll dive into tangible benefits such as carbon reduction, cost optimization, and supply chain resilience—while also highlighting compelling case studies and forward-looking trends shaping the future of sustainable water solutions.

Water Scarcity: Why Desalination Is Non-Negotiable

By 2025, the United Nations projects that two-thirds of the global population will live in water-stressed regions. Factors like climate change, industrialization, and population growth are accelerating the depletion of freshwater sources such as rivers, lakes, and aquifers.

Take a real-world example: In Cape Town, South Africa, the city faced a catastrophic drought in 2018 that brought it within days of "Day Zero"—the complete shutdown of municipal water supplies. In parallel, countries like Saudi Arabia and Israel have already turned desalination into a national security priority, relying on it for up to 70% of their drinking water supply.

Currently, over 20,000 desalination plants across more than 150 countries produce upwards of 95 million cubic meters of freshwater per day, yet the industry is not without criticism.

Environmental Consequences of Traditional Desalination

1. High Energy Consumption: Depending on the method—Reverse Osmosis (RO), Multi-Stage Flash (MSF), or Multi-Effect Distillation (MED)—desalination processes can consume between 3 to 25 kWh per cubic meter of water, driving up operational costs and carbon footprints.

2. Brine Disposal Risks: The discharge of hyper-saline brine into marine environments leads to oxygen depletion, increased water temperatures, and sometimes toxic chemical releases, threatening aquatic biodiversity.

3. Infrastructure Emissions: Beyond operations, the construction of desalination infrastructure involves large volumes of high-grade metals and composites, which, if sourced traditionally, significantly contribute to greenhouse gas emissions.

The challenge, therefore, is not whether to build desalination plants—but how to build them sustainably. This is where recycled materials, especially scrap metals, come into play.

The Vital Role of Metals in Desalination Technology

Metals are foundational to desalination plant design and functionality. Whether it's the structural skeleton that holds massive plumbing systems together or the micro-engineering used in filtration devices, metal use in desalination is non-negotiable.

Where Metals Are Used in Desalination Plants

- High-Pressure Pumps: Reverse osmosis processes require pressures up to 1,000 psi (pounds per square inch) to force water through filtration membranes, necessitating durable, corrosion-resistant metals.

- Heat Exchangers: In technologies like MED and MSF, these components must effectively transfer heat while withstanding high thermal loads, favoring metals with high thermal conductivity.

- Intake and Outfall Pipelines: These pipes must resist pressure, salt corrosion, and physical wear over decades of continuous use.

So, what metals dominate the ecosystem?

- Copper – Excellent for heat transfer and electrical applications, often used in tubing and cabling.

- Stainless Steel – Chosen for its strength and resistance to corrosion, perfect for structural components and brine pipelines.

- Aluminum – Its lightweight nature makes it ideal for modular desalination units and corrosion-prone offshore installations.

Traditionally, most of these metals are mined, smelted, and fabricated—a process that consumes significant energy and emits substantial carbon. Transitioning to scrap-sourced metals can make a dramatic difference.

Circular Economy Meets Desalination: The Strategic Power of Scrap Metals

Adopting circular economy principles—reduce, reuse, recycle—can be a game-changer for industrial-scale water treatment. For desalination, incorporating recycled metals represents one of the most impactful circular strategies.

1. Energy Savings & Lower Emissions

Consider the immense energy footprint of metal production:

- Copper: New copper production requires up to 215 GJ/tonne of energy. Recycling uses just a fraction—reducing energy input by up to 90% and resulting in comparable performance.

- Aluminum: Production from bauxite is notoriously energy-intensive, requiring around 14,000 kWh per tonne. Recycled aluminum needs just 5% of that.

- Steel: Producing steel from scrap in an electric arc furnace (EAF) reduces carbon dioxide emissions by up to 1.5 tonnes per tonne of steel.

Given that desalination plants can contain hundreds of tonnes of metal, these differences scale rapidly. For example, incorporating 100 tonnes of recycled steel instead of new could avoid 150 tonnes of CO2 emissions—equivalent to taking 32 cars off the road for a year.

This makes a strong case for incorporating recycled materials into Environmental Product Declarations (EPDs) and Life Cycle Assessments (LCAs) for desalination infrastructure, aligning the industry with Sustainable Development Goals (SDG 6 and SDG 12).

2. Cost Optimization

Volatile commodity markets significantly impact infrastructure budgets. For instance:

- Copper hit a 10-year high at $10,700 per tonne in 2021 due to global supply chain disruptions.

- Steel prices surged in 2022 amid energy price hikes and logistical constraints.

Scrap metal markets, by comparison, tend to fluctuate less dramatically, especially when sourced locally or regionally. This stability translates into budget predictability—a critical concern for governments and private financiers who are increasingly tying funding to ESG performance.

Furthermore, the use of recycled metals can dramatically reduce upfront capital costs. One desalination project in Mexico saw material costs drop by 18% simply by specifying secondary metals.

3. Enabling Scalable Infrastructure

Scalability is crucial in emerging and water-stressed countries. Many nations struggle to finance massive desalination plants but still need smaller systems that can grow incrementally.

Modular desalination units built with lightweight aluminum and corrosion-resistant steel reduced the cost and time-to-deployment of portable facilities in Morocco and Tunisia by over 35%. This was achieved without compromising performance, partly due to the use of high-grade recycled metals.

These units are particularly valuable for humanitarian applications, remote mining operations, and island communities where infrastructure is minimal but water needs are urgent.

Metals and Brine Management: An Overlooked Connection

Beyond building the plant itself, scrap metals play a critical role in managing its waste, particularly brine.

Advancements in Zero-Liquid Discharge (ZLD)

ZLD systems aim to eliminate brine discharge altogether by reprocessing waste brine into usable water and extractable salts. These advanced systems often operate under high pressure and temperature, where only the most durable metals can survive.

Modern ZLD designs are incorporating aluminum and copper alloys made from recycled sources into discharge valves, filtration chambers, and evaporative crystallizers. This helps improve longevity and lowers material costs, all while supporting green procurement goals.

Brine Mining: Turning Waste into Wealth

An emerging trend in desalination is the recovery of valuable minerals like:

- Lithium

- Magnesium

- Potassium

- Rare Earth Elements

Brine mining complexes require specialized components capable of resisting harsh chemical reactions. By deploying recycled metal alloys, operators can lower costs while achieving minimal environmental disruption. According to a 2023 International Water Association (IWA) report, brine mining could offset up to 25% of desalination plant operating costs while creating new revenue streams.

Sustainable Brine Pipeline Design

Pipelines and outfall systems are the most exposed to long-term corrosion, especially at the brine interface. Advanced recycled steel integrated with anti-corrosive coatings like epoxy or fiberglass compounds are now used in major projects across the Middle East and Australia. These upgraded systems have extended pipe lifespans by 40% while cutting material emissions by nearly half.

Scrap Metal Driving Real-World Sustainability

1. Saudi Arabia’s Thermal Desalination Revolution

Saudi Arabia, producing 24 million m³/day of desalinated water, faces severe corrosion in its Multi-Stage Flash (MSF) plants. The Jubail III facility now uses 90-10 copper-nickel (Cu-Ni) alloys from recycled sources for heat rejection tubing and evaporator shells. This scrap-sourced alloy withstands chloride concentrations >50,000 ppm and temperatures up to 120°C, reducing replacement costs by 40% compared to virgin stainless steel. The plant’s brine outfall pipelines—lined with recycled aluminum-bronze—show zero crevice corrosion after 5 years, despite hyper-saline discharge 61.

2. Chile’s Brine-to-Fodder Circular Model

In Chile’s arid Arica region, a reverse osmosis plant produces 86,400 liters/day of brine. Instead of ocean discharge, the brine irrigates 400+ Atriplex nummularia (saltbush) plants—a halophytic fodder crop. The irrigation system uses scrap-aluminum sprinklers resistant to salt-induced corrosion. This circular approach yields 12 tonnes/year of livestock feed, offsets 1.5 tons of CO₂ via photovoltaic-powered pumping, and provides 30% extra income for local farmers. Brine utilization here aligns with 9/11 circular economy strategies 10.

3. Singapore’s Closed-Loop NEWater Integration

Singapore’s Tuas Nexus desalination-plant combines recycled stainless steel (from scrapped ships) in reverse osmosis racks with brine concentration tech. Magnesium recovery units—built using repurposed titanium scrap—extract 98% pure Mg(OH)₂ from brine, sold to battery manufacturers. The plant’s material circularity rate exceeds 87%, slashing lifecycle emissions by 34% while supporting SGD 6.3 (water recycling targets) 712.

Future Outlook: 3 Trends Reshaping Sustainable Desalination

1. AI-Driven Material Optimization

Emerging platforms like DesalOpt use machine learning to match scrap metal grades with corrosion risk profiles. For example:

High-risk zones (e.g., brine heaters): Specify scrap-sourced duplex stainless steel (PREN >40)

Low-risk zones (e.g., pre-treatment): Use recycled aluminum alloys

This reduces virgin material demand by 25% while extending component lifespans 1.

2. Next-Gen Membranes & Brine Mining

2025 Breakthrough: Graphene-enhanced membranes with recycled copper nanowire supports boost flux rates by 60%. Concurrently, "brine refineries" deploy scrap-titanium crystallizers to extract lithium (for EVs) and magnesium (for alloys). A pilot in Israel achieves 92% salt recovery, turning waste into a USD 420/tonne revenue stream 121.

3. Policy-Driven Circular Ecosystems

The EU’s Critical Raw Materials Act (2023) mandates ≥30% recycled content in public infrastructure, including desalination plants. Similar policies in California (SB 245) tie funding to scrap-metal utilization rates, accelerating projects like the Doheny Ocean Desalination facility, which sources 50% of its metals from regional recyclers 37.

Conclusion & Strategic Takeaways

Desalination is inevitable for water security—but its sustainability hinges on decoupling infrastructure growth from resource depletion. Integrating scrap metals isn’t a niche tactic; it’s a strategic imperative. Key actions:

🔧 For Plant Developers & Engineers

Prioritize "Corrosion-Matched" Recycling: Use recycled copper-nickel alloys (C70600/C71500) in high-temperature/brine zones 6.

Design for Deconstruction: Modular joints (e.g., bolted vs. welded) enable future scrap recovery.

Adopt Brine Valorization: Partner with mining firms to co-locate mineral extraction systems.

💼 For Policymakers & Investors

Link Funding to Circular Metrics: Require ≥40% recycled metal content and brine utilization plans.

Scale South-South Knowledge Transfer: Chile’s halophyte model is replicable in Morocco or Australia 10.

🌍 The Big Picture

By 2030, desalination could supply 17% of global freshwater. With scrap metal integration, we can cut the sector’s carbon footprint by 50 million tonnes/year while making water abundance an equitable reality. The technology exists; the scrap is available; the action must begin now.

"No resource is infinite—except human ingenuity."
— Adapted from G. Bateman, Hydro Industries