In Perth, a Machine That Turns Toxic Brine Into Drinking Water and Buried Carbon

On Monday, in the northern suburbs of Perth, a ribbon was cut on a facility that tries to solve two crises with one machine. Capture6, a startup from Berkeley, California, switched on Project Tortuga at the Australian Automation and Robotics Precinct: an industrial-scale plant that recovers freshwater from desalination brine while capturing carbon dioxide straight from the air.

Eight containerized units are now running as a single integrated system. This is not a benchtop experiment. The equipment is the same class of hardware that would fill a commercial plant, and the point of running it is to generate the hard operating data, on performance, energy use, and product quality, that future partners need before signing on. The launch drew the Western Australian Minister for Energy and Decarbonization's office and the City of Wanneroo mayor, a sign of how seriously the state takes both halves of the pitch.

The machine that does two jobs

Start with the problem Capture6 is piggybacking on. Desalination plants turn seawater into drinking water, but they are inefficient: at a typical recovery rate of 45%, every liter of freshwater leaves behind roughly 1.2 liters of concentrated saltwater brine. That brine is a liability. It is expensive to dispose of, and when dumped into the ocean it harms marine ecosystems.

Capture6 runs an electric current through that brine, stripping the salt into sodium and chloride ions. The sodium bonds with hydroxide groups from water molecules, forming sodium hydroxide, a solvent that grabs CO2 out of ambient air and locks it into solid, mineralized carbonates. Along the way, the process recovers around half of the freshwater still trapped in the brine and produces green chemicals, such as hydrochloric acid and calcium carbonate, that heavy industry would otherwise import.

The engineering detail that matters: every unit operation at Tortuga uses commercially available, industrial-scale equipment. CB&I served as the primary engineering partner, leading front-end engineering design and commissioning, while ATE/Huber fabricated the balance of the plant. Because nothing is custom, scaling up is a matter of replication rather than redesign, which is what future partners, from mine sites to utilities, will want to hear.

Why Perth is the perfect test site

Perth's water numbers tell you why the company picked Australia. Inflows into the city's dams have fallen from an average of 420 gigaliters a year before the mid-1970s to about 76 gigaliters a year since 2010, according to the Water Corporation. Desalination now supplies around half of Perth's drinking water, and industry accounts for 46% of Western Australia's water allocation. The city is already desalting its way out of a drying climate, which means it is already generating the waste stream Capture6 needs.

Zoom out and the arithmetic gets striking. Across Australia, Capture6 estimates that desalination, energy, and industrial processes generate up to 950 gigaliters of brine each year. Treating that brine could unlock up to 470 gigaliters of additional freshwater annually, equivalent to around 188,000 Olympic swimming pools, with the technical potential to remove approximately 15 million metric tons of CO2 from the atmosphere per year. Tortuga exists to build the operating evidence that turns that potential into something partners will finance.

Perth is already desalting its way out of a drying climate, and every liter of freshwater comes with 1.2 liters of waste. Tortuga treats that waste as the feedstock.

The economics that make it different

Conventional direct air capture has a brutal cost problem: removing and storing a single ton of CO2 can cost as much as $1,000 with today's technology, and revenue depends almost entirely on selling carbon credits into a voluntary market that remains thin and volatile. Capture6's answer is to stack revenue streams: freshwater sales, avoided brine disposal costs, green chemical production, and carbon removal credits all flowing from the same process.

CEO Ethan Cohen-Cole has argued the process could dramatically reduce, or even eliminate, the net cost of carbon removal, because the customer is already paying to deal with the brine. "Australia needs new sources of water and new ways to remove carbon, and Tortuga shows both can come from the same system," he said at the launch. Dan Bull, the WA member for Maylands, made the government's version of the case: "Project Tortuga shows how we can get more out of every liter we desalinate, while tackling climate change at the same time."

The model is already moving on a second front. In Southern California, Capture6 is completing construction of the first phase of Project Monarch for the Palmdale Water District. At full scale, that project would turn roughly 2.6 million liters of brine a day from the district's purification facility into clean water, captured CO2, and green chemicals, saving the district up to 40% compared with alternative brine management and eliminating the need for 68 hectares of evaporation ponds. Construction is scheduled to finish in early 2027, with operations expected in the second quarter. Tortuga itself was supported through Round 1 of Australia's Carbon Capture Technologies Program, and the company is backed by investors including Tetrad Corp, Hyundai Motor Group's ZER01NE Ventures, Energy Capital Ventures, and Elemental Impact.

What Tortuga actually has to prove

The next 12 to 18 months will be about measurement, not headlines: energy consumption per ton of CO2, actual water recovery rates, and verified carbon balances at industrial scale. Capture6 designs each project around a partner's specific brine, water, and carbon profile, and because the units are containerized they can be deployed directly at partner sites, from mine operations to industrial facilities, without disrupting existing operations.

The company is also lining up a wider pipeline. Project Octopus in South Korea will pair the technology with a seawater desalination plant and produce low-carbon chemicals for heavy industry, while Project Wallaby, a partnership with Pilot Energy, would integrate carbon removal and water recovery into the Midwest Clean Energy Project in Western Australia.

Skepticism is warranted. Brine mineralization is one of several direct air capture pathways, and gigaton-scale visions depend on brine availability, cheap clean energy, and rigorous verification of how much carbon is truly, durably removed. But the field's quietest truth is that the chemistry is rarely the hardest part; bankability is. Tortuga is engineered, end to end, to produce the operating data a water utility or a lender needs to sign. That, more than the CO2 tally, is the real experiment.