Introduction
The key difference between Blue and Green Hydrogen is the production process.
Historically, Hydrogen is produced from Natural Gas through Steam Methane Reforming. It is what we call Grey Hydrogen.
This process releases massive volumes of CO2 into the atmosphere.
To reduce this carbon footprint, we can capture the CO2 and, either store it or recycle it. If, this Carbone Capture brick is added, the color of the hydrogen becomes Blue.
Green Hydrogen is produced via electrolysis: water is split between Hydrogen and oxygen. For the Hydrogen to be called green, all the electricity used in this process must come from renewable resources (Wind, solar or hydro)
Hydrogen’s role in decarbonisation
Hydrogen plays a key role in decarbonation as a molecule.
It can be burnt directly instead of Natural Gas to generate heat without carbon footprint.
It follows then the equation H2 + 1/2 O2 -> H2O, meaning burning Hydrogen releases only vapor.
Hydrogen can also be combined with CO2 and other carbon molecules, coming from a Carbone Capture process for example, to produce a new carbon chain like alternative fuels.
Blue Hydrogen
Blue hydrogen is Grey Hydrogen, produced via Steam Methane Reforming, where CO2 is captured.
In this Reforming process, natural gas is combined with high-temperature steam in the presence of a catalyst, triggering a chemical reaction that produces hydrogen and carbon monoxide.
For Hydrogen to become Blue, Carbon is captured which creates a low-carbon alternative of Grey hydrogen. This process has the main advantage of being applicable to current grey Hydrogen production facilities and decarbonate them without changing the initial process; Steam Methane Reforming.
Green Hydrogen
Green hydrogen is produced from the electrolysis reaction of water using renewable electricity.
Electrolysis is the process of splitting water (H2O) into Hydrogen and Oxygen. The electricity used for this process must comes from Renewable resources for Hydrogen to be called green.
This method of Hydrogen production has the lowest carbon footprint.
Cost and Technology Comparison
As a reference price, Grey Hydrogen costs vary from 1.5$ to 2.5$/kg.
Blue Hydrogen sees its cost rising to 2$-3.5$/kg while Green Hydrogen costs $3.50–$6.00/kg.
The production costs of Green Hydrogen are extremely dependent from the Electricity price, with the fluctuation of the renewable electricity production.
Blue Hydrogen carbon footprint depends on the efficiency of the Carbon Capture process. Current calculations show a reduction of Carbon footprint, versus Grey Hydrogen, of 70%-85%. Green Hydrogen allows a Carbon Reduction of 90% compared to Grey Hydrogen.
Blue hydrogen is typically produced via steam methane reforming (SMR) or autothermal reforming (ATR) of natural gas, processes that release significant amounts of CO₂ (4kg of CO2 for 1kg of H2).
To mitigate emissions, carbon capture systems are integrated, with capture efficiencies generally ranging between 60–90%. However, upstream methane leakage during natural gas extraction and transport can significantly affect the overall carbon intensity of blue hydrogen.
In contrast, green hydrogen is generated by water electrolysis, most commonly using proton exchange membrane (PEM) or alkaline electrolyzers, powered by renewable energy sources. Green hydrogen production generally achieves 60–70% efficiency for current electrolyzers, with PEM systems offering faster dynamic response but slightly higher energy demand than alkaline units.
When accounting for renewable power generation and grid integration losses, system-level efficiencies can drop to 45–60%.
Market Applications
After a wave of Hydrogen projects announced after the COVID period; of which only a handful materialized, Hydrogen usage in mobility will not happen right away. On the contrary, its usage within the Industry is growing.
Blue and Green Hydrogen are, most of the time, not used directly. Hydrogen is often combined with Carbon molecules to produce alternative fuels (including sustainable aviation fuel). It can also be converted to Ammonia thanks to Nitrogen. All applications of Ammonia are therefore possible (fertilizer, urea…)
Challenges for Each Type
Both, blue and green hydrogen face significant hurdles in progressing from technical maturity to financial viability.
Blue hydrogen depends on large-scale deployment of Carbon Capture, Utilization, and Storage (CCUS), which remains limited in maturity due to capture efficiency constraints, infrastructure requirements, and uncertainty around the long-term integrity of geological storage.
Even when CO₂ is captured, options for its recycling or utilization in synthetic fuels and chemicals are still nascent and insufficient to absorb projected volumes, leaving storage as the dominant pathway for the time being.
Green hydrogen, while technologically proven at pilot scale (~10MW), struggles with scaling due to the high capital cost of electrolyzers and the limited availability of surplus renewable electricity. Achieving financial maturity is further constrained by the intermittency of renewables, which reduces electrolyzer utilization rates and drives up the levelized cost of hydrogen.
In both cases, the pathway to competitiveness requires overcoming not only technical barriers but also fianancial limitations, either in securing reliable CO₂ handling for blue hydrogen or ensuring abundant, low-cost, clean electricity for green hydrogen.
Conclusion
Hydrogen, Blue and Green, is playing a key role for decarbonation of our Industry.
It still needs to overcome two major challenges to reach its full maturity: technical maturity and market maturity.
The first will come with time and experience, like any industrial evolution. The second does not depend on the industrials but on the governments. A legal framework is necessary for a market to exist. Else, the cheapest solution (Grey Hydrogen) will still be preferred. .
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