Cerulean Hydrogen
A New Category, Proposed
Hydrogen is usually classified by how it's produced — green (electrolysis), blue and grey (fossil-based), white (naturally occurring, extracted), and orange (stimulated subsurface geochemical production). None of these describe hydrogen produced by engineering the same water–rock reactions that generate hydrogen naturally underground, but doing so above ground, in a controlled, sealed, oxygen-free system.
We're proposing a name for that category: Cerulean Hydrogen.
Definition: Cerulean Hydrogen is proposed to denote hydrogen produced through engineered water–rock redox reactions within a contained, above-ground system — without fossil hydrocarbons as the hydrogen-bearing feedstock, and without subsurface hydrogen extraction or in situ geologic stimulation. Process conditions are actively managed, with the specific operating regime determined by the particular implementation.
This is a structural classification, not a performance claim — it describes a class of systems, not any specific implementation's results.
Pronunciation: suh-ROO-lee-uhn
The Auri Project's proposed implementation is based on accelerated serpentinisation, using iron-bearing mineral feedstock and deoxygenated water, within a sealed reactor. That's one way of realising the Cerulean Hydrogen category — not a requirement of the category itself.
Why propose a new term
The chemistry (serpentinisation) is well established in the geochemical literature. What's new is applying it deliberately, above ground, as an engineered process rather than something drilled for. We think that distinction deserves its own name, so it isn't confused with either electrolysis or subsurface extraction.
Cerulean Hydrogen shares its geochemical reaction domain with white and orange hydrogen, but differs in operating above ground, independent of subsurface access.
The term Cerulean Hydrogen is offered for unrestricted generic use. No permission or licence is required, and The Auri Project asserts no proprietary, trademark, or exclusive ownership over the term.
The Auri Project's patent interests relate to potential apparatus and method, not to ownership of the terminology.
Read the classification paper — preprint, not peer reviewed: https://doi.org/10.5281/zenodo.21390654
The Auri Project's role
The Auri Project is developing one engineered implementation of this category. We are at a pre-commercial research stage:
The chemistry is grounded in the serpentinisation literature.
The Auri Project has not yet completed an Auri-specific bench-scale reactor run.
No production, yield, efficiency, or environmental claims are being made for our process at this time — those are questions for the research ahead, not answers we have yet.
We think engineered serpentinisation is worth investigating as an above-ground approach to hydrogen production that does not rely on subsurface hydrogen extraction or in situ geologic stimulation, and does not use electrolysis as the generating mechanism.