The short answer is: because we’re a consortium specialised in producing green hydrogen. But you didn’t click on this post just for us to tell you the obvious, did you?
The truth is that green hydrogen has become incredibly popular in recent years. It’s one of those concepts that’s somehow slipped into everyday conversations. If you listen carefully, you’ll catch people mentioning hydrogen in your local bakery, coffee shops, even on the bus. But do we actually know what green hydrogen is?
The surname “green” usually tells us that something is environmentally friendly. In the case of hydrogen, it refers to its origin, to the kind of energy that was used to produce it. That’s why hydrogen comes with soooo many colours – and green is, by far, the least common nowadays.
In this short guide we’ll walk you through the different colours of hydrogen and explain why, at ASTERISK, we’re betting everything on green.
As many colours as origins
Hydrogen has an entire colour palette to itself. It’s not really a technical classification; it’s simply an easy way to describe the origin of this energy vector. We often associate hydrogen with clean energy. However, as we’ll see now, that’s not always the case.
Black or brown hydrogen: is the most polluting method, as it requires high temperatures, as well as to burn coal to obtain hydrogen. This process, known as gasification, releases dihydrogen (molecules of hydrogen) and carbon monoxide. Although it’s the one of the oldest methods, it’s also the least recommended due to the amount of energy required and, maybe most importantly, the amount of CO₂ it releases into the atmosphere.
Grey hydrogen: right now, this is the method most widely used by industry. Here, hydrogen is extracted from hydrocarbon molecules, such as methane, using a technique known as steam reforming. This process requires a massive amount of energy, as gases are exposed to extremely high temperatures and pressures.
Blue hydrogen: isn’t really a method on its own, but rather a complementary strategy to make grey or brown hydrogen slightly less pollutant. It involves capturing the carbon dioxide released during the production process and storing it, reducing the environmental impact of hydrogen generation.
Turquoise hydrogen: like blue hydrogen, this complementary technique seeks to limit pollution from processes that use coal or hydrocarbons to obtain hydrogen. In this case, the process is methane pyrolysis. Instead of releasing CO₂ as a by-product, this process generates solid carbon as waste, which isn’t released to the atmosphere and is easier to store.
You may have noticed one key detail: all these methods rely entirely on fossil fuels. While some processes implement measures to limit greenhouse gas emissions, they are still incompatible with the clean energy future we’re trying to build. Blue hydrogen, for example, is considered a low-carbon option in the EU, but it’s not really carbon-free. However, there’s no need to lose hope: there are still other colours on our palette, so let’s take a look at them!
A little bit of light
Another way to produce hydrogen is through electrolysis: applying an electric current to split water into hydrogen and oxygen. The electricity used can come from many different sources.
If it originates from nuclear sources, then the product is referred to as pink hydrogen. The use of solar power, often combined with a mix of fossil fuels and other renewable energy sources, gives us yellow hydrogen, a clear reference to our bright and shiny star – the Sun. Although yellow and pink promote a reduction of greenhouse gas emissions, they are sadly still not sustainable methods to make hydrogen.
There’s also white or natural hydrogen, an option only explored very recently. Researchers discovered deposits of dihydrogen gas underground, which is exceptional, considering it usually occurs combined to other chemical elements, forming minerals and molecules. What makes this kind of hydrogen interesting is that it is a source of energy in itself, instead of an energy vector, meaning that no other source of energy, whether renewable or fossil, is needed to obtain it.
Recent discoveries point to the existence of huge deposits of white hydrogen in regions such as Lorraine, in France, and the Basque Country and Huesca, in Spain. Outside of Europe, companies are beginning to invest in exploration projects in the US, Australia, and Mali. However, designing facilities to obtain hydrogen from these deposits poses major challenges, given the gas’s volatility and flammability.
A new proposal for future
We’ve looked at the different ways hydrogen is produced today –and as we’ve seen, they are rarely environmentally friendly. Most still depend on fossil fuels, making the goal of climate neutrality much harder to reach. With 2050 on the horizon, Europe is aiming to balance the greenhouse gases we emit with the amount we can capture and store.
But there’s one colour on our palette that we haven’t talked about yet. It’s precisely the one that gives this story its title (and the one ASTERISK is fully committed to).
Green hydrogen is produced through electrolysis, just like pink or yellow hydrogen. But for it to be considered green, electricity must exclusively come from renewable energy sources. It’s the method with the lowest environmental impact, and the one receiving a huge collective effort worldwide.
Of course, using clean energy for electrolysis doesn’t automatically make the entire process perfectly green. That would make things much more boring, wouldn’t it? The truth is that in most cases, electrolysers still rely on scarce and polluting materials. In addition, most of commercial electrolysers use purified water, a precious and rare resource on our planet.
At ASTERISK, we want to greenify every part of the process, which is why we are working on a very different type of electrolyser that avoids the use of toxic and polluting compounds while exploring ways to replace rare materials, such as platinum, with more abundant ones. We’re also working with seawater instead of fresh water – a real headache at times, but worth the effort!
ASTERISK was born as a consortium dedicated to green hydrogen because it’s what brings us together, but it became our speciality because we’re convinced that it’s necessary to push for a cleaner and more responsible energy model, both for people and for the planet.
And we have the tools to achieve it.