The Colors of Hydrogen

Grey hydrogen is produced from natural gas through a process called steam methane reforming (SMR). Although it is currently the most common method, it releases significant amounts of CO₂ into the atmosphere. As a result, grey hydrogen is not considered sustainable and does not align with global emission reduction goals.

An interesting side fact: brown hydrogen is similar to grey hydrogen but is produced from coal, often through gasification. This method is even more carbon-intensive than grey hydrogen and results in very high CO₂ emissions. It is one of the most environmentally harmful methods of hydrogen production and is not suitable for a clean energy future.

Green hydrogen is produced through electrolysis, a process that uses renewable energy sources such as wind or solar power to electrochemically split water into hydrogen and oxygen. This method generates no CO₂ emissions and is therefore considered the most sustainable and environmentally friendly form of hydrogen production. Green hydrogen is widely regarded as the ultimate goal of a clean hydrogen economy.

Blue hydrogen is produced similarly to grey hydrogen, but with the added step of capturing and storing the resulting CO₂ emissions (CCS – Carbon Capture and Storage). It is considered a transitional solution, as it generates lower emissions than grey or brown hydrogen. However, its sustainability depends on the effectiveness and availability of CCS technology and infrastructure.

Pink hydrogen is produced through electrolysis using electricity generated from nuclear energy. The resulting hydrogen is considered low in emissions. However, this method is controversial, as it raises concerns about the safe storage of radioactive waste and the limited public acceptance of nuclear power.

Turquoise hydrogen is produced through methane pyrolysis – a process in which natural gas is split into hydrogen and solid carbon. If powered by electricity from renewable sources, this energy-intensive method results in no direct CO₂ emissions. However, the use of natural gas as a fossil feedstock remains problematic. Environmental concerns focus particularly on potential methane emissions during extraction and transport. Additionally, methane pyrolysis is still in the early stages of technological development, which currently means high costs and limited maturity for widespread application.

White hydrogen refers to naturally occurring hydrogen that is stored in geological formations. So far, its presence is rare and remains insufficiently researched scientifically. Due to the limited data available, there are currently significant uncertainties regarding potential extraction technologies, environmental impacts, and economic feasibility. If a technically and environmentally responsible method of extraction becomes viable in the future, white hydrogen could eventually contribute to the energy mix in the long term.