Waste from carbon capture helps extract critical minerals

Today’s world runs on critical minerals. The elements are the building blocks of batteries, electronics, and a slew of other technologies and are often key to the economic and national security of a nation. In the US, most of these elements are imported, and researchers have been working for years to find domestic sources of these minerals to avoid supply chain disruptions.

At the American Chemical Society Fall 2025 meeting, Pacific Northwest National Laboratory (PNNL) scientist Chinmayee Subban explained how she and her team extract critical minerals using the waste from a technology capable of tweaking ocean chemistry, to lower the costs of both processes.

Critical mineral recovery processes almost always use acid-base chemistry; it’s precipitation chemistry at scale, Subban said. But industrial acids and bases can be expensive to manufacture and store, so “it’s always valuable if you can find low-grade waste chemicals that you could use for the extraction,” she said.

Electrochemical ocean alkalinity enhancement, or OAE—a process wherein scientists increase the pH of seawater to draw carbon dioxide from the air and counter ocean acidification—offers one such source of acid. Through a public-private partnership with Ebb Carbon, PNNL scientists have deployed an OAE system developed by the company. The system uses electricity and a specialized membrane to separate ocean water into streams of acidic, basic (alkaline), and partially deionized water. But “the benefits of the ocean alkalinity are limited to the alkaline stream,” Subban said. “There’s a lot of acid that’s generated.”

That waste acid can be used to extract minerals from another waste stream: the salty brine left over from desalination, which is the first step of the electrochemical OAE system. “Think of it as Lego blocks,” Subban said. If the steps are in the correct order, scientists can generate a couple of mineral coproducts depending on the starting feed water and local industrial ecology, she explained.

So far, Subban’s team has demonstrated that waste acid can pull lithium from the salty brine produced during desalination. Her team has also pulled uranium from the water, and her future work will focus on extracting strontium, she said.

They’ve also shown that waste acid can extract nickel from locally sourced olivine minerals, flipping the economics of domestic nickel extraction. The scientists showed that, even without accounting for any revenue from CO₂ removal credits, “we were able to get sufficient net positive benefits” on the dollar per ton, she said. In fact, the waste acid digests the olivine faster than a commercial equivalent, Subban said, likely because the low grade acid contains a small amount of salt.

To “take something that is a waste and [use it] to improve aspects of the lithium and nickel extraction will be incredibly beneficial down the road,” said Tyler Bridges, a graduate researcher at Virginia Tech and attendee of the presentation. “There’s a lot of exciting work that’s being done in that field right now,” he added.