Desalination

Desalination encompasses a set of physico-chemical processes that remove salts and other minerals from seawater or brackish water to produce freshwater. With 110 million m³/day of installed capacity in 2024, it has become a key solution for water security in arid regions.

Main technologies

• Reverse osmosis (RO): accounts for more than 70% of global capacity thanks to its high energy efficiency (~3 kWh/m³ compared with ~10 kWh/m³ for thermal desalination).
• Multi-stage distillation (MED/MSF): still used in the Middle East where thermal energy is cheap and abundant.
• Innovations: graphene membranes, integrated renewable energy, and hybrid systems combining RO with solar PV or wind power.

Deterministic advantages

• Guarantees a secure supply of drinking water (100% supply in the Canary Islands).
• Reduces coastal aquifer extraction, preventing saltwater intrusion.
• When integrated with photovoltaics, it cuts the carbon footprint by 80%.

Environmental challenges

• Brine: global discharge rate is 1.5× product volume; dilution and diffusers are necessary.
• Marine life intake: intake velocity < 0.15 m/s and 5-mm screens → mortality < 1%.
• Carbon footprint: fossil-based grids raise emissions to 1.6 kg CO₂e/m³; renewable energy reduces this to 0.25 kg CO₂e/m³.

Innovation trends

• Graphene–MXene membranes: +15% permeability, –10% pressure.
• Hybrid floating desalination: NEOM project (Saudi Arabia) 50,000 m³/day with wind + PV.
• Brine mining: recovery of lithium and magnesium improves economic viability.

Costs

• Global average price: €0.50–€1.20/m³.
• 2030 outlook: costs expected to drop by 20% due to more efficient pumps and energy-recovery systems.
• Spain: > 5 million m³/day of installed capacity, the European leader.

Benefits

• Provides 100% of supply in the Canary Islands, avoiding a 250 hm³/year deficit.
• Reduces extraction from coastal aquifers and prevents saltwater intrusion.

Deterministic challenges

• Brine management: salinity increase up to 30% within 500 m of the outfall.
• Carbon footprint: RO powered by the grid → 1.6 kg CO₂e/m³; solar-powered → 0.25 kg CO₂e/m³.

Spain case study 2005–2024

• Installed capacity: 5.2 million m³/day.
• Contribution to supply: 12% of urban water and 20% of agricultural water in the Almería coast.
• Reduced overexploitation of the Campo de Dalías aquifer: 30 hm³/year.

Desalination is viable and scalable when integrated with renewable energy and environmentally responsible brine management, ensuring resilient water supply and reducing water stress.