In this post I would like to introduce green hydrogen, describe what it is, how it compares to the many other colors of hydrogen (did you know it came in colors?).
Let’s start with the name hydrogen. Hydrogen means creator (gen) of water (hydro).
Hydrogen is a colorless, odorless, tasteless, gaseous substance that is the simplest member of the family of elements. It’s number 1! Despite its number 1 status, Hydrogen sounds pretty boring, huh?
But it’s also highly flammable (see video below), which means that any projects (even pilot projects) that work with this not-so-boring gas must include significant risk ID and analysis. And although this ‘boring’ gas it is indeed colorless, a whole spectrum of colors – mainly meant to describe how it is made – has been established. In my research for this post, I have encountered references to white, black, brown, blue, yellow, pink, and turquoise, and of course, green hydrogen.
Below I’ll discuss the “colors” on the hydrogen spectrum individually. Much (but not all) of this comes from a very good National Grid site.
Blue hydrogen is produced mainly from natural gas, using a process called steam reforming, which combines natural gas and steam. This produces hydrogen – but has carbon dioxide as a by-product. To prevent this CO2 from being released, carbon capture and storage (CCS) is essential to trap and store this carbon. Blue hydrogen is sometimes described as ‘low-carbon hydrogen’ as the steam reforming process doesn’t avoid the creation of greenhouse gases – it lowers it.
Grey hydrogen is the currently the most common form of hydrogen production. Grey hydrogen is created from natural gas, or methane, using steam methane reformation but (thus the “grey” name) is produced without capturing the greenhouse gases that are byproducts.
Black and brown hydrogen - Using black coal or lignite (brown coal) in the hydrogen-making process, black and brown hydrogen forms, as the name implies, are the absolute opposite of green hydrogen in the hydrogen spectrum and the most environmentally damaging. In fact, any hydrogen made from fossil fuels, such as carbon, through the process of ‘gasification’ is sometimes also called black or brown hydrogen.
Pink hydrogen is generated through electrolysis powered by nuclear energy. Nuclear-produced hydrogen can also be referred to as purple hydrogen or red hydrogen. We really are covering the entire spectrum here! It should be noted that the very high temperatures from nuclear reactors could be used in other hydrogen production processes by producing steam for more efficient electrolysis or fossil gas-based steam methane reforming.
Turquoise hydrogen is very new and yet to be proven at scale. Turquoise hydrogen is made using a process called methane pyrolysis to produce hydrogen and solid carbon. In the future, turquoise hydrogen may be valued as a low-emission hydrogen, dependent on the thermal process being powered with renewable energy and the carbon being permanently stored or used.
Yellow hydrogen refers to hydrogen made through electrolysis using solar power. Yellow – sun – you get it.
White hydrogen is a naturally-occurring geological hydrogen found in underground deposits and created through fracking. There are no strategies to exploit this hydrogen at present. Seems like a potential for new projects – at least research projects!
Green hydrogen (finally!!) is produced with no harmful greenhouse gas emissions. Green hydrogen is made by using clean electricity from surplus renewable energy sources, such as solar or wind power, to electrolyze water. You remember electrolysis from your science classes, don’t you? Apply electricity to water and it breaks the H2O int H2 and O. As of this writing, green hydrogen currently makes up a small percentage of the overall hydrogen production, because creating it is expensive. Just as energy from wind power has reduced in price, green hydrogen will come down in price as it becomes more common. In my next blog post I will cover the process to create Green Hydrogen and discuss a very recent development – breaking news of sorts - in green hydrogen with a pilot underway in France.