The project enters a market under mounting pressure from climate-driven water scarcity. More than 20,000 desalination plants operate worldwide, expanding at roughly 7% annually since 2010, but the industry’s own carbon footprint and damage to coastal ecosystems have grown alongside that demand. Whether deep-sea technology can deliver on its cost and environmental promises at commercial scale remains unproven, researchers said.
A Southern California startup is developing technology it says would use the natural pressure of the deep ocean to power seawater desalination, reducing the energy demand and environmental harms that have made conventional plants targets of legal challenges for years.
OceanWell plans to anchor reverse osmosis pods 1,300 feet below the surface of Santa Monica Bay, roughly four miles off the coast, using the ocean’s own weight to force seawater through membranes that strip out salt and impurities. The company says its planned Water Farm 1 would produce up to 60 million gallons of drinking water daily while cutting energy consumption by about 40% compared to land-based plants — and generating far less of the concentrated brine that conventional plants discharge back into coastal waters.
“The freshwater future of the world is going to come from the ocean,” said Robert Bergstrom, OceanWell’s chief executive. “And we’re not going to ask the ocean to pay for it.”
A global boom with mounting costs
More than 20,000 desalination plants operate worldwide, and the industry has been expanding at about 7% annually since 2010 as climate change intensifies droughts and disrupts rainfall patterns. For many countries in the arid Middle East, parts of Africa and Pacific island nations, desalination is not optional — there simply is not enough freshwater to meet demand, according to AP reporting.
The industry’s scale carries its own climate burden. Plants worldwide produce between 500 and 850 million tons of carbon emissions annually, an output approaching the roughly 880 million tons emitted by the entire global aviation industry, the AP reported.
“With aridity and climate change issues increasing, desalination will become more and more prevalent as a key technology globally,” said Peiying Hong, a professor of environmental science and engineering at King Abdullah University of Science and Technology in Saudi Arabia.
Scientists warn that as desalination scales, cumulative damage to coastal ecosystems — many already under pressure from warming waters and pollution — could intensify.
California’s contested record
The Carlsbad Desalination Plant, which came online in 2015 as the largest seawater desalination facility in North America, illustrates the tradeoffs at the center of the debate. The plant can produce up to 54 million gallons of drinking water daily and supplies about 10% of San Diego County’s water — enough for roughly 400,000 households.
San Diego imports roughly 90% of its supply from the Colorado River and Northern California, sources increasingly strained by climate change. Desalination was proposed as a local, drought-proof alternative drawn from the Pacific Ocean.
Environmental groups argued the plant’s seawater intake and brine discharge pose unacceptable risks to marine life. Before it opened, organizations filed more than a dozen legal challenges and regulatory disputes; most were dismissed but some resulted in changes to the project’s design and permits.
“It sucks in a tremendous amount of water, and with that, sea life,” said Patrick McDonough, a senior attorney with San Diego Coastkeeper, which has participated in multiple legal challenges to the project. “We’re not just talking fish, turtles, birds, but larvae and spores — entire ecosystems.”
A 2009 Regional Water Quality Control Board order estimated the plant would entrap some 10 pounds of fish daily and required offsetting those impacts by restoring wetlands elsewhere. Seventeen years later, that restoration remains incomplete, the AP reported. A 2019 study found the plant’s brine discharge raises offshore salinity above permitted levels, though it detected no significant biological changes — likely because the site had already been heavily altered by decades of industrial activity from a neighboring power plant, according to AP reporting.
Those impacts carry particular weight in California, where roughly 95% of coastal wetlands have been lost largely to development, leaving the remaining lagoons as vital habitat for fish and migratory birds.
“When we start messing with these very critical and unfortunately sparse coastal lagoons and wetlands, it can have tremendous impacts in the ocean,” McDonough said.
Michelle Peters, chief executive of Channelside Water Resources, which owns the Carlsbad plant, said the facility uses large organism exclusion devices and one-millimeter screens to minimize marine life uptake and dilutes its brine discharge with additional seawater before releasing it. She said years of monitoring have shown no measurable impacts to surrounding marine life and that the plant has significantly cut its energy consumption through efficiency improvements and operates under a plan aimed at making the facility carbon net-neutral.
Cost as the deciding variable
Gregory Pierce, director of UCLA’s Water Resources Group, said deep-sea desalination appears promising from an environmental and technical standpoint, but warned that cost will determine whether the approach succeeds commercially.
“It’s almost always much higher than you project” with new technologies, Pierce said. “So that, I think, will be the make or break for the technology.”
OceanWell is not the only company pursuing subsea approaches. Norway-based Flocean and Netherlands-based Waterise have tested subsea desalination systems and are working toward commercial deployment. Other companies are powering conventional plants with renewable energy or developing more efficient membrane technology to reduce energy consumption.
For now, OceanWell’s technology remains in development. A single prototype operates at the Las Virgenes Reservoir in western Los Angeles County, which serves about 70,000 residents. Nearly all the reservoir’s water originates in the northern Sierra Nevada and is pumped some 400 miles over the Tehachapi Mountains — a journey requiring massive amounts of energy and leaving communities vulnerable when Sierra snowpack runs low.
OceanWell has also signed an agreement to test its system in Nice, France — another region facing intensifying droughts and wildfires — beginning this year.
Many water experts say recycling and conservation should take priority over desalination, noting that wastewater purification typically uses far less energy than processing seawater and can substantially reduce impacts on marine life. Las Virgenes is pursuing a wastewater reuse project alongside its desalination partnership.
“What we are looking for is a water supply that we can count on when Mother Nature does not deliver,” said Pedersen, a Las Virgenes official quoted by the AP. “Developing new sources of local water is really a critical measure to be more drought and climate ready.”
The Associated Press, which produced the source reporting for this article, receives support from the Walton Family Foundation for coverage of water and environmental policy. The AP is solely responsible for its content.