In the California desert, a new wastewater plant might hold the key to cheap carbon removal

On the edge of the Mojave Desert, 60 miles north of Los Angeles, a new water treatment plant will turn wastewater into drinking water. The plant will also test something new: removing CO2 from the atmosphere at little to no cost.

Right now, using machines for “direct air capture” is an expensive process. Removing and storing a single ton can cost as much as $1,000. With around 40 billion tons of CO2 emitted by humans each year, the nascent industry can’t easily scale up to address the problem. But Capture6, a startup partnering on the new project in Palmdale, California, is taking a different approach.

The new process “has the potential to dramatically reduce or even eliminate the cost of the carbon dioxide removal,” says Ethan Cohen-Cole, Capture6’s CEO.

The company integrates its tech into existing industrial sites. In the new project, which recently broke ground, the tech will also tackle a problem for the water treatment plant. When it processes wastewater, the plant will end up with tons of brine—something that’s usually costly to get rid of. Capture6 will use that brine to create a solvent that captures CO2 from the air.

A new way to suck CO2 from the atmosphere

Most direct air capture technology works by pulling air through a filter or liquid to absorb CO2. Then it uses a lot of energy to get the CO2 out for storage or reuse. But instead of using filters, Capture6 has one main step—the solvent it makes from brine reacts with the CO2 to form a mineralized carbonate. The CO2 doesn’t have to be removed again. Instead, the carbonate can be used to make green chemicals. The water treatment plant will use the product to replace some of the chemicals it normally uses, reducing emissions from its supply chain.

“Our carbon removal system was designed from the beginning as a way to facilitate decarbonization, not just remove carbon dioxide from the atmosphere,” says Cohen-Cole. The water treatment plant will also save emissions by avoiding the need to transport brine waste elsewhere. In total, he says, the process saves so much energy throughout the supply chain that it offsets its own direct energy use. It’s also designed to run on renewable energy.

The tech also generates more drinking water that otherwise couldn’t be extracted from brine. (The water treatment plant will inject all of its clean water underground into aquifers, so it will get into the water supply indirectly rather than being piped into homes.) By generating more water, eliminating the need to dispose of brine, and producing a replacement for chemicals at the plant, the startup may be able to fully fund CO2 removal without relying on selling carbon credits.

“We’re hopeful that voluntary and compliance markets [for carbon credits] continue to grow,” says Cohen-Cole. “But in the absence of those, we also believe that ultimately carbon dioxide removal can scale to its potential by enabling other industries to become more efficient.”

The potential to capture billions of tons of CO2

Water treatment plants produce such a massive amount of brine waste each year that the process could scale up to capture billions of tons of CO2, Cohen-Cole says. In Palmdale, the new plant will capture around 25,000 tons of CO2 a year while purifying 4.5 million gallons of water. The technology can also be used in other industries, like mining, and at decarbonization plants along the coast, where companies often dump brine back into the ocean, harming marine life.

The water utility expects to save 40% of the lifetime cost of treating water at the plant because of the new technology. Because of the cost savings, Capture6 says that it already has a line of interested customers. Other projects will soon break ground in Australia, South Korea, and other parts of the U.S. And because it’s not relying on carbon credits to grow, the company believes it could scale up much faster than others in the industry.

The startup might also get community support more easily than some others, since it can help generate clean water and avoid the environmental impact of dumping brine or injecting it underground. It also avoids the need to transport captured CO2 elsewhere, a process that has risks. And unlike some other direct air capture companies, the startup has no ties to the fossil fuel industry. “A lot of direct care capture solutions are serving the oil and gas industry in a lot of ways, and have the potential for greenwashing in continuing to enable the fossil fuel industry to pollute,” says Danya Hakeem, VP of portfolio at Elemental Excelerator, a nonprofit that invested in the startup. “This solution is totally different.”