Green, Blue and Grey Hydrogen: A Guide to Their Differences and Role in the Energy Transition

Transformation is required across several sectors for the energy transition to succeed. A move from fossil fuels to renewable energy sources will mean changes to existing industrial processes.

Accordingly, it’s not good enough to talk about hydrogen in general, though. There are different types, and they’re not all environmentally friendly. That’s why understanding the different types matters. Although it’s a colourless gas, the energy industry uses nicknames or colour codes to specify the type of hydrogen. Knowing about those colour codes leads to a deeper understanding of how clean and sustainable each type is. This article explores each colour and how it’s made.

Understanding Hydrogen Colours: What Do They Mean?

There are multiple types of hydrogen with different colour codes. They include black, blue, pink, purple, brown, yellow, white, grey, turquoise and green hydrogen.

The key reason to use these colour nicknames is to understand the type of production involved. There are several ways to make hydrogen, and that involves a range of processes and materials. Certain types, such as black or brown hydrogen, involve production using coal. Others use renewable sources.

Knowing the colour and the production method of the hydrogen becomes crucial when measuring the carbon footprint.

Grey Hydrogen: The Conventional but Carbon-Intensive Option

The most common form of hydrogen in production today. It’s primarily produced through a method known as steam methane reformation (SMR) which involves natural gas or methane.

Grey hydrogen is not an appealing option for the energy transition due to its environmental impact. Not only it is dependent on fossil fuels, but it also has a high carbon footprint.

Black and Brown Hydrogen

Often considered the most environmentally damaging type, black and brown hydrogen are made using black or brown (lignite) coal, through a process called gasification.

They rely on fossil fuels for production, which is why they’re thought of as a subtype of grey hydrogen.

Blue Hydrogen: A Low-Carbon Alternative?

Another type that uses natural gas and steam reforming is blue hydrogen. Like the grey type,is produced through Steam Methane Reforming. However, the key difference is that carbon capture and storage (CCS) is used to contain and store the carbon that’s released as a by-product.

The reason that blue hydrogen is seen as a low-carbon alternative is that greenhouse gases are still created; they’re just not released during production. That’s an environmental improvement over grey, where the carbon emissions are high.

This type is serving as a stepping stone to lower emissions, although the CCS comes at a cost.

Green Hydrogen: The Key to a Sustainable Future

When people talk about hydrogen’s use for clean electricity, they’re referring to green hydrogen. It’s made using renewable energy sources like wind power or solar power. It’s done by water electrolysis. The electrochemical reaction splits it into its components, leaving oxygen and hydrogen behind.

Crucially, the electrolysis process to create green hydrogen emits no carbon dioxide, meaning a significant potential in the energy transition thanks to its zero-carbon footprint, environmentally friendly production process and sustainability.

The production price is linked to the use of renewables. While it is perceived as expensive, the price will go down as the use of renewables becomes more common and technology advances. Economies of scale have a role to play, making green hydrogen the economically sound long-term solution.

Yellow Hydrogen: Harnessing the Power of the Sun

Yellow hydrogen gets its name from how it’s produced, which is through solar power. It’s a relatively new term that’s used to identify a subtype of green hydrogen.

Purple, red and pink Hydrogen: A Nuclear-Powered Solution

Purple hydrogen is produced using nuclear energy. In fact, there are three types of hydrogen produced in that way: purple, red and pink. Purple is produced using nuclear power alongside heat and water. Through electrolysis and thermolysis, hydrogen is produced.

Pink hydrogen uses nuclear power and water through electrolysis. The red type comes about through nuclear heat and water through thermolysis alone. The process results in zero greenhouse gases. It’s a viable option for zero-carbon electricity.

However, there are still environmental impacts to consider. They include uranium mining, radioactive waste disposal and the large quantities of water required for cooling.

Turquoise Hydrogen: The Process of Methane Pyrolysis

It’s made through a process called methane pyrolysis. Heat is added to methane molecules, which results in decomposition. It produces hydrogen and solid carbon, thus limiting CO₂ emissions into the environment.

Being the carbon output solid and not a gas, it doesn’t imply CO2 in the environment. That means there’s no need for CCS, and the solid carbon can be used for other applications. It’s still early days for this type, but it can be used in industries that currently use grey, black or brown hydrogen, such as oil refineries.

White Hydrogen: Found in Nature

White hydrogen, which is sometimes called gold, is the naturally occurring form of hydrogen. This geological hydrogen is found in underground deposits. It’s created by natural geological processes, where water interacts with mineral-rich rocks under high-pressure conditions. It’s also formed by fracking.

Since it’s naturally occurring, it doesn’t require combustion to create it. That means there are no CO2 emissions or use of fossil fuels involved in the production. However, identification and extraction are the issues. As extraction isn’t a common practice yet, methods need to be developed, and the impact on the environment is measured. Extraction processes will need to be sustainable.

Which Type of Hydrogen Is Best for the Energy Transition?

The aim of the energy transition is to move away from a dependence on fossil fuels, greenhouse gases and high carbon footprints. For that reason, the move from grey hydrogen to green hydrogen is vital. At present, it’s the most sustainable and proven option for meeting net-zero goals.

FRIEM provides reliable and efficient solutions for green hydrogen production, supplying high current rectifies system to supply the electrolyzers.

The high-performance converters are tailored for electrolysis production and are suitable for heavy industries. Its reliable rectifier systems enable the conversion of AC power to stable DC power. With over than 70 years of industry experience, it offers green solutions for chemical and aluminium production, heat treatments and metal refining.