This article was originally on Hakai magazine, an online publication about science and society in coastal ecosystems. Read more of these kinds of stories hakai magazine. com.
In May 2022, California officials unanimously rejected a plan to build a $1.4 billion desalination plant in Huntington Beach. The plant, officials said, would produce precious water and potentially harm the marine environment. The decision was not an outright rejection of desalination, but it highlighted some of the problems that have made desalination an impractical solution to California’s water problems.
Dragan Tutic, founder and CEO of Oneka Technologies, says large desalination plants powered by fossil fuels are not the only way to extract fresh water from the ocean. His company is preparing to bring what it says is sustainable, practical desalination to the small town of Fort Bragg on California’s northern coast.
Fort Bragg was a logging town until the Georgia-Pacific mill closed in 2002. Today it is a popular tourist spot with untamed beaches wrapped in rocky cliffs, lively tide pools and a beach famous for sea glass.
As in much of California, water is a precious commodity in Fort Bragg. The city has only three surface sources of water: the Noyo River and two small tributaries. In dry years, all three can slow down and the Noyo can become brackish, putting the city at risk of shortages.
“We’re kind of stuck,” said John Smith, Fort Bragg’s director of public works. “That’s why we’re looking at the ocean.”
Desalination is an idea that keeps popping up in the Golden State, where excessive groundwater and shrinking reservoirs are critical issues. On the surface it seems simple: get the salt from the abundant salt water just off the coast. But typical desalination plants are large, expensive to run and environmentally unfriendly, especially when the resource-intensive process is powered by fossil fuels. The Carlsbad desalination plant in Southern California, for example, sits on 2.4 acres of land and uses 246,156 megawatt hours of electricity per year, equivalent to the use of approximately 23,000 households.
Oneka’s experimental water desalination device is not like the other desalination plants in California: it is a 6.5 meter wide buoy. The small footprint is a bonus, but the main advantage of the device is that it is ocean powered. As the buoy moves back and forth with the waves, it pulls water through a filter and then through a reverse osmosis membrane, which removes the salts and other small particles. “Surprisingly simple,” says Smith.
Andrea Achilli, a chemical and environmental engineer at the University of Arizona who is not affiliated with Oneka, mentions devices like these direct desalination systems. Direct desalination can also be achieved with solar energy, which can be converted to heat and used for thermal desalination. Simply put, thermal desalination boils salt water, collects the vapor and leaves the salt behind. Likewise, the Oneka buoy does not take energy from an external source; it has everything it needs on board. “It’s a really good use of the wave energy,” Achilli says.
More established desalination techniques have other environmental problems that the buoy manages to avoid as well. Standard desalination produces brine – the intensely salty slurry that is removed to make saltwater fresh. This brine must be managed and disposed of. But the brine spread by Oneka’s buoy has a low concentration, Tutic says, meaning it can be released back into the ocean, where it has little to no impact on the environment.
Oneka has already deployed this technology off the coast of Florida and Chile, adapting the design when potential problems arose. Tutic says a big challenge was making the buoy robust enough to withstand storms. “Our first version we deployed in 2015 and [2016], we tested it; we broke most of it in the ocean,” he says. “But that’s how we learned it.” Tutic says the latest generation can withstand six-meter waves and can be easily disconnected and moved in anticipation of more extreme conditions.
For now, the Fort Bragg plant will have one device that will produce about 50,000 gallons of fresh water per day. That’s not much — enough for about 43 average households — but Tutic says the purpose of the trial device is to collect water quality and system performance data that will help the company make refinements and adjustments. Ultimately, he says, the company wants to install a range of devices. “It’s modular,” says Tutic. “You can adjust a number of units to make essentially as much water as you need.”
Achilli seems less optimistic. “The energy potential of wave energy… is very big because the ocean is so big,” he says. But renewables are diluted forms of energy, he says, so you need a lot of materials and resources to harness all that potential. In other words, you need a lot of buoys.
As Fort Bragg tries to cope with its water problems, Smith says desalination is just one part of the city’s strategy. It also has a mobile desalination plant to treat brackish water in the Noyo River and plans to build reservoirs.
The Oneka buoys are not a complete solution, says Smith. But the pilot project is about more than just Fort Bragg water. It’s also a proof of concept, a way to show that technology and engineering can help overcome the state’s persistent water problems. “I think this is a good start,” he says.
This article first appeared in Hakai magazine and is republished here with permission.