Book a Discovery Call
Book a Discovery Call
Desalination has always come with a heavy bill in energy and brine. A new generation of deep-sea water farms lets the weight of the ocean do the hard work.
When I was about seven, I asked my parents why we couldn’t just drink the ocean. We were standing on a beach, looking at more water than I could see the end of, and it seemed like the most obvious fix for every drought I had ever heard about on the news. The answer was that it’s too salty, and taking the salt out costs a fortune. I accepted that for years. It turns out the better question was never whether we could drink the ocean, but whether we could ask it more gently.
The need is real. About four billion people, roughly two thirds of humanity, face severe water scarcity for at least one month every year. Rivers are stretched thin, aquifers are being pumped faster than rain can refill them, and droughts keep getting longer and harder to predict. Meanwhile about 97 percent of the planet’s water sits in the ocean, too salty to use. So it makes sense that desalination, turning seawater into fresh water, has become one of the fastest growing kinds of infrastructure on Earth, with nearly 16,000 plants now running worldwide.
The way we usually do it, though, comes with real costs. Most modern plants use reverse osmosis, which means forcing seawater at enormous pressure through membranes fine enough to hold back the salt. Creating that pressure on land takes a lot of electricity, which makes the water expensive and, depending on the power source, carbon heavy. Then there is the leftover brine. A UN-backed study found that the world’s plants produce about 1.5 liters of salty brine for every liter of fresh water, around 142 million cubic meters a day, and much of it goes straight back into coastal waters, where it can sink and smother life on the seafloor. The giant intake pipes that pull seawater in can also trap fish and swallow larvae and plankton along with the water.
This is where my seven-year-old question finally gets a better answer. A new wave of engineers has started asking what happens if you move the plant instead of fighting the physics. Deep underwater, the weight of the ocean above creates a huge amount of natural pressure. Put a reverse osmosis system hundreds of meters down, and the sea itself does much of the pushing that a land plant has to pay for in electricity. These systems are being designed as modular “water farms,” clusters of pods sitting quietly on the seafloor and sending fresh water up a pipeline to shore, while the coastline above stays a beach instead of becoming an industrial site.
The benefits stack up in a way I find genuinely exciting. Because the ocean supplies the pressure, the energy needed for every gallon can drop significantly compared with a conventional plant. Because the water left behind is only lightly concentrated before it mixes back into the deep current, there is no thick plume of brine building up near the shore. Intakes can be designed to draw water in slowly enough that marine life isn’t pinned against the screens. And because the farms sit far below the surface, they are sheltered from the storms, floods and algae blooms that can force surface plants to shut down. Every one of those is a reason communities have been wary of desalination for decades.
This one is close to home for me, because Edge, the firm behind this page, works with a client building exactly this kind of deep-sea water farm. What strikes me most is that the engineering is only half the story. A first-of-its-kind water system has to show it can run reliably for decades before a city will sign up for its water, and investors want that proof before they commit. Closing the gap takes capital, insurance and patient structuring, the unglamorous work that turns a promising pilot into something a whole region can actually depend on.
My generation is going to inherit the water crisis whether we like it or not. We’ll be the ones voting on new reservoirs, paying the water bills and deciding what gets built along our coastlines. I’d rather we walk into that with curiosity than with fear. The ocean was always the obvious answer for a thirsty planet. It just needed us to stop forcing it and start working with it. Maybe my seven-year-old self wasn’t so naive after all. She was just early.
— Ella Perera
Sources: University of Twente research on global water scarcity (Mekonnen and Hoekstra, 2016); UN University-backed study on desalination brine, Science of The Total Environment (2019).