Though Pure hydrogen is colorless and invisible but why are so many colorful descriptions like pink gray blue green used to refer hydrogen? The main reasons are its way of production, environmental impact and cost.
Pink Hydrogen: Presently Japan is producing Hydrogen by using nuclear waste heat energy and named as Pink hydrogen. Japan is the world leader in both nuclear power and hydrogen technology. Recently Japan brought two together to produce hydrogen without burning fossil fuels. After Fukushima nuclear disaster in 2011 Japan uses helium gas as reactor coolant instead of water which can run up to 1000°C while water cooled reactors can run only to 315°C. This heat energy is used to produce hydrogen by high temperature steam electrolysis (HTSE) process. Pink hydrogen is usually considered as green hydrogen because it does not produce any CO2 emissions during operation.
Gray Hydrogen: Gray Hydrogen is produced from fossil fuels and natural gas. Most of the hydrogen produced today is gray Hydrogen for its low cost and commonly used in fertilizer Iron Steel production & refining oil.
Gray Hydrogen is produced by rearranging the molecular structure of hydrocarbons through chemical reactions. In this process methane is mixed with steam at high temperature to yield hydrogen and carbon dioxide through a catalytic chemical reaction.
Unfortunately almost 10 ton CO2 releases to produce 1 ton of gray hydrogen. This high ratio CO2 emission gives its name as ‘Gray’ hydrogen.
Blue Hydrogen: High purity blue hydrogen is produced by Thermo-Neutral Reforming (TNR) and a catalyst used to convert diesel or methane into hydrogen. The CO2 produced in this process is captured, then recycled to produce methanol. Due to capturing and circular Reforming of CO2 this hydrogen is designated as ‘Blue’ hydrogen. In this process around 80-85% hydrocarbon energy is converted into hydrogen. Presently SABIC Saudi Arabia is producing blue hydrogen on a large scale & exporting to Japan.
Green Hydrogen: This form of hydrogen is produced by separation of hydrogen and oxygen molecules from water through the electrolysis process. The electricity used in this process comes from renewable energy sources like wind and solar energy. Since no CO2 emission is involved in this production process, it’s named as ‘Green’ hydrogen.
Other color Hydrogens:
Black or brown Hydrogen designated when produced from coal.
Red Hydrogen designated when produced from biomass.
Yellow Hydrogen designated if produced solar energy.
White Hydrogen designated to naturally occurring geological hydrogen that might be (rarely) found in underground deposits.
Summary: So, Hydrogen can play a significant role in future clean energy. Since it has the highest energy density after nuclear energy and three time more energy density than any fossil fuels. It is still a long way to go to reach zero- emission potential. Scientists are working hard to gradually shift from gray or blue hydrogen to green hydrogen and reduce emissions.