Earlier this year, BASF had to delay the opening of a battery materials plant in Finland when a court agreed with environmental groups that the company didn’t have a good plan to deal with its wastewater. 

As battery factories spring up around the world, the specter of wastewater threatens to stall their construction. One startup, though, says the solution isn’t to dispose of it, but recycle it.

Wastewater from these plants emerges laden with sodium sulfate, a byproduct of sulfuric acid and caustic soda, two chemicals used in battery manufacturing, copper refining and other industries. 

“We can totally create a circular economy around these reagent chemicals,” Bilen Akuzum, co-founder and CTO of Aepnus Technology, told TechCrunch.

Akuzum and co-founder Lukas Hackl didn’t set out to create a small circular economy, instead stumbling upon it when touring lithium mining operations in California and Nevada. The pair of chemists, who have been friends since they met in their dorm’s cafeteria, were researching possible startup ideas. 

“We were thinking about lithium extraction or something in the minerals space,” Akuzum said. “Every time we spoke to somebody from the industry, they were like, ‘Well, there are actually solutions for lithium extraction. But we have this waste product that’s coming out of our operations, and we really don’t know what to do with it.’”

After returning from the trip, Akuzum and Hackl turned the idea over in their heads, eventually deciding to refine an existing technology to turn that waste into raw materials that the facilities could use in their operations.

The two founded Aepnus to modernize the century-old chloralkali process, which splits salts like sodium sulfate back into the acids and bases that created them. 

The company uses electrolyzers to zap the salts, coaxing them into splitting. Other companies do the same thing, but they might use pricey metals to help speed the reactions. “We don’t use any expensive catalysts in our electrolyzers,” Akuzum said.

Aepnus is currently shipping half-scale models of its equipment to customers, who can test the devices on their own wastewater streams. Each site’s wastewater is likely to contain different contaminants, some of which need to be filtered beforehand. Once they’re out, the electrolyzers can work on removing the sodium sulfate.

For customers, fully recycling sodium sulfate waste should reduce disposal and material costs. And for those with remote sites, like miners, they’re also saving on transportation. “Rather than mining operations purchasing these chemicals and getting them trucked in from very long distances, we can regenerate those chemicals onsite from the waste,” Akuzum said.

The startup has over 15 customers at various stages ranging from feasibility studies to testing the pilot-scale equipment. Aepnus recently raised an $8 million seed round to ship more pilot-scale electrolyzers and develop the commercial-scale version. The round was led by Clean Energy Ventures with participation from Gravity Climate Fund, Impact Science Ventures, Lowercarbon Capital, Muus Climate Partners and Voyager Ventures.

If Aepnus can commercially produce its electrolyzers, it would mark a milestone for the U.S. “There’s only a handful of companies in the entire world that have the expertise of building these types of electrolyzers,” Akuzum said. “Unfortunately, there’s not a single company in the United States that has that know how.”