A recent Infographic by Jeffrey Winters, Editor-in-Chief of ASME magazine, highlighted how the different types of hydrogen are identified using color codes. The different hydrogens are not actually different colors, all are colorless, however since it must be manufactured, the different processes have been given a color code.
For example, “brown” hydrogen is the least expensive to make, using a process to turn coal into a gas then react it with high temperature steam. However, the major byproduct of this process is carbon dioxide. It’s hard to tell whether this process is better than just burning coal.
The “gray” hydrogen process is like the “brown,” except natural gas is used instead of high-temperature steam. However, unwanted greenhouse gases are still produced.
If the unwanted gases from the processes producing either “brown” or “gray” hydrogen are captured and kept from entering the atmosphere, then you have “blue” hydrogen.
The cleanest process is where water is split into oxygen and hydrogen by electrolysis, yielding “green” hydrogen. Lots of variations on ways to produce hydrogen are constantly being investigated, however, as the author says, “Luckily, there are still plenty of colors left. – Dr. Tom
