Brown Vs Grey Vs Blue Vs Green Hydrogen: All hydrogen burns the same, but the different methods of producing it have produced colourful nicknames.
- Hydrogen is an odourless, invisible gas.
Brown Vs Grey Vs Blue Vs Green Hydrogen
- Using water and heat, coal can undergo “gasification”. In this process, the chemicals within coal react to make what was known as “syngas.”
- Syngas contains a mixture of carbon dioxide (CO₂), carbon monoxide (CO), hydrogen, methane and ethylene, along with small quantities of other gases.
- The first two of these gases have no use in power generation. This makes the process very polluting, compared to other methods. However, chemical companies can distil hydrogen from this mixture relatively simply.
- As waste-to-energy incinerators become more common, they increasingly use similar processes to generate brown hydrogen.
- A similar process can produce syngas from biomass and petrochemicals.
- Most hydrogen currently comes from natural gas, but this process also creates a lot of carbon waste.
- The majority of chemicals in natural gas contain large amounts of hydrocarbons – hydrogen chemically bonded with carbon.
- Catalysts can break these bonds, but the excess carbon then creates CO₂.
Blue hydrogen – more technology, less pollution
- Blue hydrogen relies on the same process as grey hydrogen, along with carbon capture and storage (CCS).
- This eliminates the emissions of grey hydrogen, improving the hydrogen’s environmental impact.
- Growth of blue hydrogen has remained slow, as it waits on the development of more large-scale CCS plants.
Why is “green hydrogen” the ultimate goal?
- Green hydrogen cuts out polluting chemicals entirely.
- It requires water and electricity, which create hydrogen using electrolysis.
- Electrolysis is a chemical reaction where an electric current is passed through metal conductors, known as electrodes, in water.
- This separates water into its component elements, hydrogen and oxygen.
- Using electricity originally generated by renewable sources makes this hydrogen carbon-free and consequently “green.”
- Clean hydrogen still costs too much to enable it to be widely deployed.
- At the moment, grey hydrogen is cheaper than the blue and green hydrogen. The main driver of its price is the price of natural gas, which varies around the world.
- The price of blue hydrogen is also mainly influenced by natural gas prices. But its second-most important driver is the cost of capturing and reusing or storing the carbon emissions.
- Total global electrolysis capacity is limited and costly at the moment and hence the green hydrogen.