Types (colours) of hydrogen

Did you know hydrogen is categorised into colours based on how it is produced?

Hydrogen is typically categorised into different colours to describe different production pathways and their associated environmental impact. The three most common types are grey, blue, and green hydrogen.

Grey hydrogen is currently the most common, and cheapest, form of hydrogen production. It is produced from natural gas through steam methane reforming (SMR) and, as the greenhouse gas (GHG) emissions from SMR are released into the atmosphere and not captured, is considered a high carbon emitting process.

Blue hydrogen is similar to grey hydrogen in that it is also produced from natural gas through SMR. However, the GHG emissions released during SMR are significantly reduced using carbon capture, utilisation and storage (CCUS), whereby the GHG emissions released are either captured and either repurposed to produce new materials (such as synthetic fuels), or stored underground in geological formations such as aquifers or depleted oil and gas reservoirs.

However, it should be noted that deployment of CCUS technologies has been slow and they are still being developed and tested to understand if CCUS will work at scale. This IEA report offers a comprehensive perspective on CCUS.

Blue hydrogen is referred to as ‘low-carbon hydrogen’ as the production pathway doesn’t avoid the creation of greenhouse gases – just stores them away so that they are not released into the atmosphere.

Green hydrogen is produced via the electrolysis of water using clean electricity created from renewable energy sources such as wind and solar power. It is considered a zero-emissions hydrogen production pathway (the use of renewable sources eliminate all carbon emissions) however it is currently more expensive to produce than grey hydrogen.

_{Hydrogen colours and there environmental impact (Image based on Henderson, J (12 May 2022) Alberta is banking on hydrogen to lead its green transition, St. Albert Gazette, Alberta, Canada).}

Other hydrogen production pathways that are less discussed, either due to potential environmental impacts or still being at an early stage of development, include:

• Brown/black hydrogen (produced from brown or black coal using gasification).
• Pink hydrogen (produced via electrolysis but powered by nuclear energy).
• Turquoise hydrogen (produced using a process called ‘methane pyrolysis’, where high temperatures are used to decompose fossil fuels into hydrogen and solid carbon, emitting no carbon into the atmosphere).
• Yellow hydrogen (produced via electrolysis using mixed grid energy).
• White hydrogen (naturally-occurring, geological hydrogen found in underground deposits and created as a by-product of industrial processes such as fracking).

Your task

In what production methods of hydrogen do you think investment and development should be focused and why? Share your thoughts.

References

_{Henderson, J (12 May 2022) Alberta is banking on hydrogen to lead its green transition, St. Albert Gazette, Alberta, Canada}