The Colors of Hydrogen

It is the most abundant element on earth, estimated to make up a 2.5 trillion-dollar industry by 2050. We’re talking about hydrogen – a gas that has the potential to decarbonize sectors that are difficult to electrify, enabling a complete transformation of heavy industries. Today, a variety of colors are used to differentiate between production methods for hydrogen. But it is only green hydrogen, produced by using fossil-free electricity, that will ultimately be able to decarbonize heavy industry.

Green hydrogen currently represents a miniscule share of global production. Instead, black, brown, and gray hydrogen – all fossil-based and responsible for large carbon emissions – are the ones predominantly used. In addition, there are more color codes for hydrogen, and the only difference between them is what energy source is used in the production process. From black and blue to pink and green – these are the many colors of hydrogen.

Black and brown: The largest carbon emitters

As gases transformed from fossil fuels, black hydrogen (made from black coal) and brown hydrogen (made from brown coal) contribute to greenhouse gas emissions. These are considered to be the dirtiest forms of hydrogen, due to the production process of gasifying high-emission coal.

Grey: The most common type of hydrogen

Grey is the most common type of hydrogen today and is produced from natural gas through a steam reforming process. Fossil-based hydrogen – black, brown, and grey – account for nearly all global supply in today’s fast-growing market. Since they are causing significant greenhouse gas emissions, which are equivalent to the combined emissions of the United Kingdom and Indonesia, the importance of finding alternative low-carbon solutions cannot be understated.[1]

Blue hydrogen: A key to net zero or overhyped fad?

The compelling promise of carbon capture and storage (CCS) technologies have generated another form of hydrogen, blue, which has long been touted as a possible emission-reducing piece in solving the climate change puzzle. While blue hydrogen is also produced from fossil fuels, the carbon dioxide emissions are captured and stored underground, preventing it from entering the atmosphere. However, doubts have been cast on the emission-reducing potential of blue hydrogen, especially in regard to the leakage risks of indefinite long-term storage of methane gas. Taking this into account, blue hydrogen may not be able to reduce more than 9-12 percent of emissions compared to grey hydrogen, which would imply that it cannot not have a prominent  role in an actual net zero hydrogen economy.[2]

Turquoise and Biofuel hydrogen: Experimental low pollutants

A more compelling case for future resource-efficient economies is turquoise hydrogen, which utilizes a technique called methane pyrolysis to convert the carbon by-product from hydrogen production into a solid. The solid can then be used in tire manufacturing or for soil improvement.[3] Another compelling source of hydrogen is the reforming of biogas into hydrogen, while lowering emissions with CCS. Both turquoise and biofuel hydrogen are in experimental phases, but could potentially form a part of the 2030 or 2050 hydrogen mix if technological improvements are made. Meanwhile, there are also considerable doubts with all types of CCS technologies which have, so far, overpromised and underdelivered.[4]

Pink and yellow: Non-renewable electrolysis

Another generation of hydrogen is the one produced through electrolysis of water (water-splitting), a process that requires electricity. Yellow hydrogen is produced from a mixed grid, which could include any proportion of electricity generated from fossil fuels, hydro, nuclear, or other power sources. Therefore, greenhouse gas emissions from yellow hydrogen depend on the proportions of various energy sources composing the mixed grid. Pink hydrogen is entirely produced using nuclear energy, which means that it has near-zero carbon emissions. Depending on what the energy mix looks like by 2030 and beyond, pink hydrogen might form a part of the hydrogen supply in order to meet the growing demand for the energy carrier.[5]

Green hydrogen: Unique in producing zero emissions — on an industrial scale

Green hydrogen is, much like its yellow and pink counterparts, generated through electrolysis. What makes it differ from those colors of hydrogen, and all other types for that matter, is that it is entirely dependent on both renewable and fossil-free energy.[6] This can then have spillover effects in industrial applications, for example using hydrogen as a reducing agent in steel production to cut emissions drastically, or as a chemical feedstock in production of ammonia and methanol. These applications, in combination with its unique ability to produce zero emissions, make green hydrogen a key enabler of industrial decarbonization.[7]

The hydrogen economy of the future

Green hydrogen holds great potential in helping cut carbon emissions to fighting climate change – it is hard to overstate its importance. That is why green hydrogen is the only type of hydrogen that H2 Green Steel will produce at its green steel site in Boden, northern Sweden. By 2050, hydrogen is expected to account for a tenth of global energy consumption, utilized not only in heavy industry sectors, but also for transportation, heating, and power generation.[8] By that same year, 130 countries have committed to reach net zero carbon emissions.[9] For that goal to be met, emissions in all sectors will need to be cut drastically, and hydrogen may come to replace existing energy sources in the process. By 2050, hydrogen could contribute to 20% of CO2 emissions reduction, making it a valuable ally the fight against climate change.[10]

Julia Ström