A team of researchers at MIT has now developed a novel approach to producing ammonia without the reliance on traditional fossil-fuel-powered plants, which require high heat and pressure. Instead, they’ve devised a way to harness the Earth itself as a geochemical reactor, leveraging natural heat, pressure, and mineral reactivity found underground to create ammonia in an efficient and emissions-free manner.
Image Credit: Zolak/Shutterstock.com
Ammonia is the world’s most widely produced chemical, primarily used as a key ingredient in nitrogen fertilizers. However, its production is a significant contributor to greenhouse gas emissions—the largest within the chemical industry.
The team’s process involves injecting water into iron-rich subsurface rock formations. The water, which carries a nitrogen source and metal catalyst particles, reacts with the iron to produce clean hydrogen. This hydrogen then combines with nitrogen to form ammonia. A second well pumps the ammonia to the surface for collection.
While this process has been demonstrated in the lab, it has yet to be tested in a natural setting. The team’s findings are published in the journal Joule, with contributions from MIT professors of materials science and engineering Iwnetim Abate and Ju Li, graduate student Yifan Gao, and five other MIT researchers.
When I first produced ammonia from rock in the lab, I was so excited. I realized this represented an entirely new and never-reported approach to ammonia synthesis.
Yifan Gao, Graduate Student, Massachusetts Institute of Technology
The current standard method for ammonia production, the Haber-Bosch process, was developed in Germany in the early 20th century to replace natural sources of nitrogen fertilizers like mined deposits of bat guano, which were becoming scarce.
However, the process is energy-intensive, requiring temperatures of 400 degrees Celsius and pressures of 200 atmospheres. As a result, large-scale facilities are needed to make it economically viable. In regions like sub-Saharan Africa and Southeast Asia, where such plants are scarce or non-existent, fertilizer shortages or high costs have constrained agricultural productivity.
The Haber-Bosch process “is good. It works,” Abate acknowledges. “Without it, we wouldn’t have been able to feed 2 out of the 8 billion people in the world right now,” he adds, referring to the portion of the global population whose food is grown with ammonia-based fertilizers. “But because of the emissions and energy demands, a better process is needed,” he says.
Roughly 20 percent of the greenhouse gas emissions from Haber-Bosch plants come from burning fuel to generate heat, while the other 80 percent comes from hydrogen production. Although NH3 itself is free of carbon, the emissions occur during the production of hydrogen, which typically involves breaking down methane gas with steam. This process releases carbon dioxide as a byproduct.
There are alternative methods for producing hydrogen with low or no emissions, such as splitting water using solar or wind power, but these can be costly. That’s why Abate and his team focused on developing a system to produce what they call geological hydrogen.
Naturally occurring hydrogen is formed underground in certain parts of the world through chemical reactions between water and iron-rich rocks. These hydrogen deposits can be mined, much like natural methane reservoirs, but their locations and extent remain underexplored.
Abate realized that this natural process could be enhanced by injecting water mixed with copper and nickel catalyst particles into areas with iron-rich rocks.
“We can use the Earth as a factory to produce clean flows of hydrogen,” he said.
He recalls his moment of inspiration: “The ‘aha!’ moment for me was thinking, how about we link this process of geological hydrogen production with the process of making Haber-Bosch ammonia?”
This approach addresses one of the key challenges of underground hydrogen production: capturing and storing the gas. Hydrogen molecules are tiny and notoriously difficult to contain. However, by completing the entire Haber-Bosch process underground, the only material that needs to be extracted is ammonia, which is easier to store, transport, and handle.
The system requires only one additional input: a source of nitrogen, such as nitrate or nitrogen gas, added to the water-catalyst mixture before injection. When hydrogen is released from water molecules during reactions with the iron-rich rocks, it can immediately bond with nitrogen atoms carried in the water. The high temperatures and pressures needed for the Haber-Bosch process are naturally provided by the deep underground environment. A second well near the injection site then pumps the ammonia to the surface for collection.
We call this geological ammonia, because we are using subsurface temperature, pressure, chemistry, and geologically existing rocks to produce ammonia directly.
Iwnetim Abate, Professor, Massachusetts Institute of Technology
Transporting ammonia is also significantly easier and cheaper than hydrogen, costing about one-sixth as much. While hydrogen requires expensive equipment to cool and liquefy it, and limited pipelines exist for its transport, ammonia benefits from an extensive infrastructure.
In the US alone, there are over 5000 miles of ammonia pipelines and 10,000 terminals. Additionally, ammonia already has a well-established commercial market, with production projected to increase two- to threefold by 2050. Beyond fertilizer, it is also used as feedstock for numerous chemical processes and as a potential carbon-free fuel for gas turbines, engines, and industrial furnaces. Ammonia is being explored as an alternative fuel for maritime shipping, aviation, and even space propulsion.
Another advantage of geological ammonia is that untreated wastewater, such as agricultural runoff rich in nitrogen, could serve as the water source.
“We can tackle the problem of treating wastewater, while also making something of value out of this waste,” Abate said.
Gao adds that this process “involves no direct carbon emissions, presenting a potential pathway to reduce global CO2 emissions by up to 1 percent.” Reflecting on the journey, he says the team “overcame numerous challenges and learned from many failed attempts. For example, we tested a wide range of conditions and catalysts before identifying the most effective one.”
The project was seed-funded through MIT’s Climate Grand Challenges program, under the Center for the Electrification and Decarbonization of Industry.
I do not think there is been any previous example of deliberately using the Earth as a chemical reactor. That is one of the key novel points of this approach.
Yet-Ming Chiang, Professor and Co-director, Massachusetts Institute of Technology
Despite being a geological process, Chiang stresses that it occurs quickly and not on geological timescales.
Chiang said, “The reaction is fundamentally over in a matter of hours. The reaction is so fast that this answers one of the key questions: Do you have to wait for geological times? And the answer is absolutely no.”
Professor Elsa Olivetti, a Mission Director of the newly established Climate Project at MIT, also commented that, “The creative thinking by this team is invaluable to MIT’s ability to have an impact at scale. Coupling these exciting results with, for example, advanced understanding of the geology surrounding hydrogen accumulations represent the whole-of-Institute efforts the Climate Project aims to support.”
Geoffrey Ellis, Geologist at the US Geological Survey also added to the conversation, saying that, “This is a significant breakthrough for the future of sustainable development. While there is clearly more work that needs to be done to validate this at the pilot stage and to get this to the commercial scale, the concept that has been demonstrated is truly transformative. The approach of engineering a system to optimize the natural process of nitrate reduction by Fe2+ is ingenious and will likely lead to further innovations along these lines.”
Geoffrey Ellis was not associated with this work.
The next step for the team is to test the process in a real underground setting, which Abate believes could happen within one to two years. The team has applied for a patent and is working toward scaling the technology for commercial use.
“Moving forward,” Gao says, “our focus will be on optimizing the process conditions and scaling up tests, with the goal of enabling practical applications for geological ammonia in the near future.”
Journal Reference:
Gao, Y., et al. (2025) Geological ammonia: Stimulated NH3 production from rocks. Joule. doi.org/10.1016/j.joule.2024.12.006.