Natural Hydrogen

• The Earth is at the heart of iron oxide redox reactions between ferrous minerals and water percolating in the subsurface to generate H₂ via serpentinization reactions.
  

• Natural hydrogen leakages are estimated by extrapolation at several Mt/y (same order of magnitude as current annual hydrogen consumption ~70 Mt/y).
  

• Hydrogen emissions from rocks containing ferrous minerals in an onshore bassin [1] (see above) or along medio-oceanic ridges [2] (see below).
  

Monitoring allows a more precise evaluation of the quantity of H₂ released at surface level by structures known as fairy circles.

Quantity is estimated at several hundred of kilos per day confirming the high H₂ potential of the São Francisco basin [4]. Researchers are still working to understand this phenomenon [5].

Advantages

• Continuous production: hydrogen could be produced continuously with large volumes permanently replenished.

• Dedicated sensors have been developped to identify prospective areas (TRL 7-8). Existing geophysical data is often used to make the link with the subsurface (TRL 9).

• Exploration & Production tools and technologies can be reused (TRL 9).

• Low cost onshore and low carbon production.

• Low footprint on the ground.
  
  
  

Challenges

• Hydrogen generation and potential trapping needs to be better understood (TRL 3-4).

• The hydrogen system still needs to be proven by drilling wells.

• Rates and volumes may not be economical (TRL 3-4).
  
  
  
  
  
  
  

Challenges to overcome through

• Research programs are necessary in order to better understand mechanisms and model each brick.

• Need to participate in practical projects to demonstrate potential and get a global vision of accumulation mechanisms.