As the world grapples with increasing water use and climate-driven droughts, countries from the United States to Israel to Australia are building large desalination plants to bolster their water supplies. These plants can create water for thousands of households by extracting the salt from seawater, but they have also drawn harsh criticism from many environmental groups: Desalinizing water requires a large amount of energy, and it also produces a poisonous brine that many plants run straight back into the sea, damaging marine life. Recent desalination plant proposals have drawn furious opposition Los Angeles, Californiaand Corpus Christi, Texas.
But a new startup called Capture6 claims it can solve desalination’s controversial brine problem with another controversial climate technology: carbon capture. The company announced new plans this week to build a carbon capture facility in South Korea that would work alongside a nearby desalination plant, sucking carbon dioxide from the air and storing it in desalination brine, which it would import from the plant. But that’s not all. Capture6 also claims that it can torque new fresh water from the brine, which strengthens the company’s sustainability claims – and its potential profit – even further.
If it works, this facility will deliver a triple benefit. This will reduce the concentration of greenhouse gases in the atmosphere, create a new source of fresh water and limit the polluting effects of desalination. But it’s still a very big “if.”
So-called “direct air capture” facilities use a chemical reaction to pull carbon dioxide from the air and fuse it with another substance, preventing it from leaking into the atmosphere. The greenhouse gas can then be stored in solid compounds such as limestone or in chemical solutions – or, previous studies Showed, in salt brine. Capture6’s innovation is to source that brine from wastewater treatment plants and desalination plants, which have every reason to want to dispose of it in a way that doesn’t open them up to pollution charges.
The newly announced venture in South Korea, known as Project Octopus, takes the process a step further. The facility will be located at the Daesan Industrial Complex, an oil and gas industrial park in a region of the country that has suffered from water shortages due to an ongoing drought. Korean state water supplier K-water is building a seawater desalination plant at the industrial park to supply water to the oil and gas plants, which use thousands of gallons of water to cool their machinery as they operate.
The Capture6 facility will use the brine created by K-water’s desalination plant to capture carbon dioxide, and it will also use the modified brine to extract even more fresh water that the oil and gas plants can then use instead of pumping from less sustainable sources. Carbon6 also says that the solvent produced by its direct air capture operations can then be used for additional point source carbon capture at the nearby oil and gas plants, providing a double emissions benefit before the company buries all the carbon deep underwater. In other words, Capture6 will use the byproduct of water production to create even more water, and it will use the byproduct of carbon capture to capture more carbon.
“This is an interesting example of solvent-based direct air capture, but what’s innovative here is the coupling of direct air capture with the brine from desalination,” said Daniel Pike, the head of the carbon capture team at the Rocky Mountain Institute, a non- partisan climate think tank. “Essentially what’s going on is the company is saying, ‘Hey, where do we get the chemicals for our solvents? We’ll get them to desalination plants.’”
(Capture6 has received funding from Third Derivative, a carbon capture accelerator launched by Rocky Mountain Institute, but Pike himself has no financial relationship with the company.)
The company, which received early funding from several venture capital funds as well as the states of California and New York, announced its first facility in Southern California last year. That facility, known as Project Monarch, will capture carbon dioxide in wastewater from a water treatment plant in the city of Palmdale, then sell fresh water back to the city’s water system.
“What we’re trying to do is really decarbonize the water sector,” said Leo Park, the vice president of strategic development at Capture6. “So we try to integrate our facilities into the easiest thing, which is waste water and desalination plants.”
The company’s initial pilot facility in Korea will operate on a small scale. The test project will capture 1,000 tonnes of carbon per year. That’s equivalent to the annual emissions of about 220 passenger cars, and about as much as is captured at a much-vaunted direct air capture facility that began operating last year in Tracy, California. The company’s carbon capture process will yield around 14 million liters of fresh water, enough to supply around 80 homes.
But when K-water’s desalination plant is up and running at full capacity, Capture6 says it will be able to capture nearly 500,000 tonnes of carbon dioxide each year by 2026. This is many times more storage than other direct air capture facilities have achieved to date. The large-scale plant will also produce about 5 billion liters of fresh water each year, half as much as the Daesan Desalination Plant itself and enough to supply about 30,000 homes.
Pike says that the company’s growth goal is extremely ambitious, and it is unclear whether the facility will have a net negative impact on emissions, as desalination and direct air capture both require a lot of energy. In the case of Project Octopus, that energy will come from initially Korea’s power gridwhich rely heavily on fossil fuels.
“Even assuming you have the solvent, you have an intense energy requirement just to drive a direct air capture process, and a big challenge we have in direct air capture is how to improve energy efficiency,” he said . “Then what they do is they also run a very energy-intensive process to divert the solvent, which moves a lot of water around. That’s a lot of energy, a lot of water. That big picture is the challenge here.”
If Capture6 can prove that its facilities store more carbon than they emit, the company will have no problem monetizing its technology. The oil and gas companies in Daesan will buy its produced water for their cooling needs, and K-water will rely on the company to reduce the environmental damage of desalination, which caused a backlash when the plant was first announced.
“There was a lot of local concern about brine because [locals] were concerned that it would affect the marine ecosystem and fishing activities,” Park said. “Our solution can help reduce brine, so there is an added environmental benefit we can generate. This is one of the reasons why K-water wanted to work with us.”
Even so, the full-size Capture6 facility will absorb only about half of the brine that the K-water desalination plant produces, meaning the utility still has to release a lot of toxic liquid into the ocean. Park says he hopes the company can eventually scale up far enough to absorb all the plant’s brine, but they are not there yet.
Unlike many other direct air capture companies, Capture6 does not need to sell carbon credits to make money. Park hopes to one day sell credits to private companies that want to offset their emissions, but for now, Capture6’s main source of income is the same as any regular desalination plant: water. Park says the company could build future facilities at lithium mines, which also produce brine and require water to operate.
But Ekta Patel, a researcher and doctoral student at Duke University who studies the politics of desalination, said the big question about this business model is how much energy it takes for Capture6 to make the new water.
“My mind immediately jumps to the issue of energy,” she said. “How much more energy does it take to recover the additional water, is it from renewable or non-renewable sources, and what does that do to the cost of the water?” She added that if “addressing challenges related to carbon emissions and water” requires a jump in energy consumption, the solution is just “to shift resource problems.”
