Earth’s natural forces could transform underground fertilizer production

MIT researchers use underground heat and pressure to produce ammonia without energy-intensive plants

A chance discovery in West Africa decades ago has led scientists to a potentially game-changing method of producing fertilizer that could reduce the chemical industry’s carbon footprint. By harnessing the Earth’s natural heat and pressure rather than energy-intensive factories, the researchers successfully produced ammonia using only rock and water, without any additional energy input or carbon emissions.

The development, reported by Joule magazine on January 21, 2025, traces its origins to an unusual discovery in Mali in the 1980s, where locals discovered a well mysteriously flowing hydrogen gas. Scientists later determined this was caused by a natural chemical reaction between water and rock beneath the Earth’s surface.

“It was an ‘aha’ moment,” said the study’s senior author, Iwnetim Abate of the Massachusetts Institute of Technology (MIT). “We might be able to use the Earth as a factory, using its heat and pressure to produce valuable chemicals like ammonia in a cleaner way.”

The timing couldn’t be more critical. Current industrial ammonia production is critical for both fertilizer and potential future clean fuel, and consumes approximately 2% of global energy. For every ton of ammonia produced, the process releases approximately 2.4 tons of carbon dioxide, making it the chemical industry’s largest source of carbon dioxide emissions.

To test their “Earth Factory” concept, the research team created a system that mimics underground conditions. They exposed iron-rich minerals to nitrogenous water, triggering a reaction that produced what they called “geological ammonia.” The process works even at room temperature, but efficiency increases significantly at higher temperatures.

When using olivine, a naturally occurring iron-rich rock, and adding a copper catalyst at 300°C (572°F), the team produced about 1.8 kilograms of ammonia per ton of rock in 21 hours.

“These rocks are found all over the world, so this method can be adopted globally,” Abate noted. However, he acknowledged the challenges: “There’s another level of complexity that we need to address.”

The economic outlook looks promising. The cost of producing ammonia through this geological method is approximately US$0.55 per kilogram, compared with traditional production costs of US$0.40 to US$0.80. Abate aims to expand the process through his company Addis Energy, with pilot testing planned for 2026.

The research also opens up unexpected possibilities for solving water pollution problems. “Nitrogen sources are considered pollutants in wastewater, and removing them requires money and energy,” explains Gao Yifan, the study’s first author. “But we might be able to use wastewater to produce ammonia. It’s a win-win strategy. This integration can increase profits by $3.82 per kilogram of ammonia produced.

In addition to practical applications, the discovery also provides interesting insights into geochemistry. As MIT’s Ju Li points out, “Ammonia is very important for life.” Before this discovery, lightning strikes were thought to be the only natural process on Earth other than microorganisms capable of producing ammonia. “That’s why the geological production of ammonia is very interesting when you think about where life came from.”

The road to implementation involves significant engineering challenges, including drilling iron-rich rock formations, managing water injection systems and understanding how rocks interact with gases and liquids under different conditions. But if successful, this approach could provide a sustainable solution for one of the chemical industry’s most energy-intensive processes.