While the reactions tend to go faster at high temperature and pressure, the researchers found that ammonia production could be an economically viable process even at 130 °C (266 °F) and a little over two atmospheres of pressure, conditions that would be accessible at depths reachable with existing drilling technology.
While the reactions work in the lab, there’s a lot of work to do to determine whether, and how, the process might actually work in the field. One thing the team will need to figure out is how to keep reactions going, because in the reaction that forms ammonia, the surface of the iron-rich rocks will be oxidized, leaving them in a state where they can’t keep reacting. But Abate says the team is working on controlling how thick the unusable layer of rock is, and its composition, so the chemical reactions can continue.
To commercialize this work, Abate is cofounding a company called Addis Energy with $4.25 million in pre-seed funds from investors including Engine Ventures. His cofounders include Michael Alexander and Charlie Mitchell (who have both spent time in the oil and gas industry) and Yet-Ming Chiang, an MIT professor and serial entrepreneur. The company will work on scaling up the research, including finding potential sites with the geological conditions to produce ammonia underground.
The good news for scale-up efforts is that much of the necessary technology already exists in oil and gas operations, says Alexander, Addis’s CEO. A field-deployed system will involve drilling, pumping fluid down into the ground, and extracting other fluids from beneath the surface, all very common operations in that industry. “There’s novel chemistry that’s wrapped in an oil and gas package,” he says.
The team will also work on refining cost estimates for the process and gaining a better understanding of safety and sustainability, Abate says. Ammonia is a toxic industrial chemical, but it’s common enough for there to be established procedures for handling, storing, and transporting it, says RMI’s Molloy.
Judging from the researchers’ early estimates, ammonia produced with this method could cost up to $0.55 per kilogram. That’s more than ammonia produced with fossil fuels today ($0.40/kg), but the technique would likely be less expensive than other low-emissions methods of producing the chemical. Tweaks to the process, including using nitrogen from the air instead of nitrates, could help cut costs further, even as low as $0.20/kg.
New approaches to making ammonia could be crucial for climate efforts. “It’s a chemical that’s essential to our way of life,” says Karthish Manthiram, a professor at Caltech who studies electrochemistry, including alternative ammonia production methods.
The team’s research appears to be designed with scalability in mind from the outset, and using Earth itself as a reactor is the kind of thinking needed to accelerate the long-term journey to sustainable chemical production, Manthiram adds.
While the company focuses on scale-up efforts, there’s plenty of fundamental work left for Abate and other labs to do to understand what’s going on during the reactions at the atomic level, particularly at the interface between the rocks and the reacting fluid.
Research in the lab is exciting, but it’s only the first step, Abate says. The next one is seeing if this actually works in the field.