United Colors of Hydrogen
Hydrogen is often categorized in colors (green, blue, etc) according to how it is produced. However, this "color coding" is not uniform or standardized. The goal of this open project is to standardize this.
Read about the principles of the code, how to join the project.
Colour codes
Green hydrogen is produced by water electrolysis using renewable electricity (wind, hydro, etc). It is called green because there are no CO2 emissions during production. Water electrolysis uses electricity to break water down into hydrogen gas and oxygen. Hydrogen produced by solar power is sometimes called Yellow.
Blue hydrogen is produced from fossil fuels with carbon sequestration: the CO2 is captured and stored underground. Companies are also trying to use the captured carbon, which is called carbon capture, storage and utilization (CCSU). Utilization is not a requirement for blue hydrogen approval. Since no CO2 is released, the blue hydrogen production process is considered carbon neutral.
Gray hydrogen is produced from fossil fuels and typically uses the methane steam reforming (SMR) process. This process produces CO2 and eventually releases it into the atmosphere.
Black or brown hydrogen is produced from coal. The colors black and brown refer to hard coal (black) and lignite (brown). Gasification of coal is one method of producing hydrogen. However, it is a very polluting process that produces CO2 and carbon monoxide as byproducts and releases them into the atmosphere.
Turquoise hydrogen can be obtained by the thermal cracking ('pyrolysis') of methane. This process, although still in the experimental stage, removes carbon in solid form instead of CO2 gas.
Purple, Pink and Red hydrogen are obtained by using nuclear power:
- The Purple variant uses both the nuclear power and the heath, through combined chemothermal electrolysis and water splitting.
- The pink variant uses the nuclear electricity, produced by electrolysis.
- The red variant uses high-temperature catalytic cracking of water using thermal nuclear power as the energy source.
And lastly, White hydrogen refers to naturally occurring hydrogen. It can be found in underground deposits or as a byproduct of fracking.
Contribute
I'm active in the renewable energy field. I want to use this overview to share my vision on the (hydrogen) future.
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Principles
What are the principles when defining the hydrogen color code?
- Uniform and simple (to be used by the layman)
- Comparable production techniques get similar colors
Interesting reads
(wip)