Desalination: A Thirst-Quenching Future?
The cost of desalination is plummeting, raising the tantalising prospect of a world free from water scarcity. Could this technology transform arid deserts into habitable landscapes and alleviate the plight of the 1.1 billion people currently suffering from water shortages? The answer, while complex, is increasingly positive.
Currently, around 21,000 desalination plants worldwide supply over 300 million peopleâapproximately 4% of the global population. However, the potential impact is far greater, considering that closer to 3 billion people experience water stress. Increased water availability, even at a fraction of current consumption levels, would significantly alter global demographics and economic possibilities.
Desertic regions, currently accounting for roughly 14% of the Earth's landmass, represent a significant opportunity. Making these areas habitable through desalination could expand our livable land by approximately 18%. This transformative potential is already being realised, albeit on a smaller scale.
Reverse osmosis, the most efficient desalination method, involves forcing saltwater through a membrane that filters out salt, leaving behind fresh water. While previously prohibitively expensive, the cost of reverse osmosis has fallen dramatically, and this trend shows no sign of abating. Currently, the cost of desalinating water can be as low as £0.32 per tonne. This figure varies according to factors such as energy prices, construction costs, water source, and plant size, but £0.32 represents a reasonable benchmark for new, large-scale plants.
The primary cost components are energy and capital expenditure (CAPEX). State-of-the-art plants consume as little as 2 kWh of electricity per tonne of water, although some research plants have achieved even greater efficiency. With the decreasing cost of solar photovoltaic energy and battery storage, electricity costs are projected to fall significantly â potentially by 50-65% within a decade. Furthermore, CAPEX costs are consistently reduced with each doubling of installed capacity, currently improving by around 15%. With desalination capacity expanding at an estimated 6% annually, substantial further cost reductions are anticipated.
Combining projected reductions in energy consumption and energy prices, along with decreases in CAPEX and operational costs, suggests that the cost of desalination could fall to approximately £0.23-£0.24 per tonne within ten years.
This price comparison to existing water costs is crucial. In many parts of the world, desalinated water is already, or soon will be, cheaper than current tap water prices. This opens up several possibilities:
Residential use: Desalinated water could replace tap water in many developed nations, significantly reducing reliance on existing freshwater sources.
Industrial use: For water-intensive industries in water-scarce regions, desalination becomes a viable, cost-effective alternative.
Agricultural expansion: The cost of desalinated water is becoming competitive with agricultural water costs in numerous regions, especially considering the potential for water savings through greenhouse cultivation. While some crops remain too water-intensive to be economically feasible, many others are not. The projected reduction in costs could also make previously unaffordable produce viable in arid regions.
The feasibility of transporting desalinated water inland requires consideration. While transport costs add to the overall expense, they remain relatively manageable for significant distances, particularly in low-lying areas.
In conclusion, the decreasing cost of desalination presents a profound opportunity to address global water scarcity. While not a panacea, this technology has the potential to transform arid landscapes, enhance agricultural productivity, and bolster industrial development in regions facing water stress, ultimately shaping a future with greater water security. The next decade will be pivotal in determining the extent of this transformative impact.