The Colours of Hydrogen, Part 2: Blue

Blue hydrogen is cited as a suitable transition technology in the revised National Hydrogen Strategy. Image: Forschungszentrum Jülich/Reisen

There has been no change regarding which colour of hydrogen remains the ultimate target: the future is green. This will remain the case after the German federal government amended its National Hydrogen Strategy at the end of July. The revised strategy foresees the path to a green future having a few blue stops along the way. “Blue hydrogen is suitable for a transition period, as it involves a relatively small amount of CO2 emissions being released into the atmosphere and because it can help get the hydrogen economy off the ground more quickly,” says Prof. Dr.-Ing. Andreas Peschel, one of the leading researchers at the Helmholtz hydrogen cluster (HC-H2). “In the long term, however, only green hydrogen makes sense.”

What is blue hydrogen?

Blue hydrogen is actually just grey hydrogen. Greenhouse gases such as CO2 are released in the production of both types of hydrogen, for example when the energy required to divide water into its components – hydrogen and oxygen – comes from fossil fuels like coal, oil, or natural gas. The difference between blue and grey hydrogen is that with blue hydrogen, CO2 is captured before it can be released into the atmosphere. This is a process known as carbon capture. In terms of greenhouse gas emissions, blue hydrogen therefore has advantages over grey hydrogen and can support the transition of the energy system towards a net-zero global economy.

The CO2 released during the production of blue hydrogen is then typically stored under water. “Storage facilities are often used that were previously used for natural gas or oil. This has the advantage that the borehole has already been drilled and is being monitored.”

Prof. Andreas Peschel

The theoretical potential of blue hydrogen

In theory, there are numerous storage possibilities in the Earth’s crust. “In practice, however, most of these storage options have not yet been developed,” explains Peschel. Their development is associated with a great deal of expenditure, years of preparation, and subsequent monitoring that would last at least 100 years. There would also be follow-up costs and subsequent risks because the CO2 can escape if the storage facilities are not leak-proof. “We’re talking about very theoretical storage potential,” Peschel adds. Moreover, there has been a fundamental decision taken in Germany not to store any captured CO2. “In doing so, we are simply passing on the problem of getting rid of our waste to another country.”

A suitable interim solution

Blue hydrogen offers the possibility of quickly reducing the CO2 emissions released during hydrogen production. This enables the hydrogen economy to be ramped up more quickly. The additional costs for storage in existing structures are comparatively low. “Ultimately, however, the risk of storage is usually borne by countries or state-owned companies. These disadvantages do not arise in the first place with green hydrogen. The use of green hydrogen therefore makes sense in the long run. But moving forward, blue hydrogen can be a suitable transition solution in the interim,” says Peschel, who views the revised National Hydrogen Strategy as a good solution for the time being.