Researchers from the Massachusetts Institute of Technology (MIT) have discovered a way to harness natural hydrogen production underground to synthesise ammonia, potentially eliminating the need for large-scale chemical plants.
The team says the Earth’s naturally occurring heat and pressure could act as a “geochemical reactor” to produce large volumes of the hydrogen compound.
The team found water – which carries a source of nitrogen and particles of metal catalyst – injected underground into areas of iron-rich subsurface rock reacted to produce hydrogen.
That hydrogen then reacts with the nitrogen embedded in the water to make ammonia.
Using a second well, the team says it could be able to pump the ammonia up to the surface.
“We call this geological ammonia,” said MIT Professor of Material Science and Engineering, Iwnetim Abate, “because we are using subsurface temperature, pressure, chemistry and geologically existing rocks to produce ammonia directly.”
Furthermore, the team says untreated wastewater, including agricultural run off, could be used, due to its nitrogen-rich nature.
However, the process has only been demonstrated in the lab and not in a natural setting.
“When I first produced ammonia from rock in the lab, I was so excited,” said MIT postdoc student, Yifan Goa. “I realised this represented an entirely new and never-reported approach to ammonia synthesis.”
Prof. Yet-Ming Chiang, Co-Director of the MIT Center for the Electrification and Decarbonization, added, “I don’t think there’s been any previous example of deliberately using the Earth as a chemical reactor.
“The reaction is fundamentally over in a matter of hours.”
The findings represent an alternative to the energy-intensive Haber-Bosch which has powered the world’s ammonia production since the 20th century.
While green and blue hydrogen are being eyed as the way to clean up existing ammonia plants, the limited uptake of clean hydrogen has delayed plans, which is what led Abate and the MIT team to work on the process.
It comes as excitement about the potential of natural hydrogen – produced underground – has grown. However, although the natural deposits could be extracted, just like natural gas reserves, the extent and locations of the deposits remain unexplored.
Read more:Is natural hydrogen the next breakthrough or bust?
“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?” Abate explained.
Geoffrey Ellis, a Research Geologist at the US Geological Survey (USGC), who had been supporting the potential of natural hydrogen to US lawmakers, described the MIT findings as a “significant breakthrough.”
“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,” he said.
MIT says the next step will be to prove the process in a real underground site within the next two years.
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