You may have heard of blue hydrogen, gray hydrogen, or green hydrogen. In this context, the color refers to the source. Black hydrogen is made from black coal. Gray and blue hydrogen are made from natural gas. And green hydrogen is made from renewable electricity. 

Green hydrogen, which we will use in our steel plant in Boden, currently represents a miniscule share of global production. Black, brown, and gray hydrogen – all of which generate large volumes of greenhouse gas emissions – make up the vast majority of global supply.  

From black and brown to green and pink, these are the colors of hydrogen. 

As gases transformed from fossil fuels, black hydrogen (made from black coal) and brown hydrogen (made from brown coal) generate significant greenhouse gas emissions. With an emissions intensity of 22 to 26 kg CO2-eq per kg H2, these are the dirtiest forms of hydrogen and currently account for around a fifth of the world’s supply.

Gray hydrogen is produced from natural gas through a steam reforming or autothermal reforming process and accounted for more than three fifths of global supply in 2022. With an emissions intensity of 10-14 kg CO2-eq per kg H2, gray hydrogen also has a large negative climate impact. 

The compelling promise of carbon capture and storage (CCS) technologies have generated another form of hydrogen, blue, which is often touted as a solution for solving the climate puzzle. While blue hydrogen is also produced from fossil fuels, some of the emissions are captured and stored. However, the leakage of fugitive methane, a potent greenhouse gas, always occurs on some level when transporting and storing natural gas, and assumptions about the effectiveness of carbon capture processes today are often overstated. Analyses of potential emissions from blue hydrogen vary widely – the IEA estimates they could be as low as 1.5-6.2 kg CO2-eq/kg H2, while a recent study estimates that blue hydrogen may only be 9 to 12 percent better than gray hydrogen when looking at the full lifecycle. 

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, for example, tire manufacturing or for soil improvement. Turquoise hydrogen does not produce carbon emissions as a byproduct, but it does produce carbon emissions in other ways. Because it is made from methane, there are still concerns about fugitive emissions of the potent greenhouse gas. Pyrolysis also requires a lot of electricity, which may not be green. 

A potentially promising type of hydrogen production is through electrolysis of water (water-splitting), which requires electricity. Yellow hydrogen is produced from a mixed electrical grid, including any proportion of fossil fuels, hydro, nuclear, or other power sources. Thus, greenhouse gas emissions from yellow hydrogen depend on the energy sources in the grid. Pink hydrogen is entirely produced using nuclear energy, which means that it has minimal climate impact. 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 growing demand for the energy carrier. 

Like its pink and yellow siblings, green hydrogen is produced through electrolysis. What makes it different is that it is entirely reliant on both renewable and fossil-free energy.[6] The production of renewable green hydrogen enables the reduction of industrial emissions, for example in steel production or as a chemical feedstock in the production of ammonia and methanol.  

Green hydrogen holds significant potential in helping cut carbon emissions to fighting climate change – in fact, it is hard to overstate its importance. That’s why green hydrogen is the only type that H2 Green Steel will produce at its plant in Boden, northern Sweden. By 2050, hydrogen is expected to account for a tenth of global energy consumption, utilized not only in heavy industrial sectors, but also for transportation, heating, and power generation. More than 70 countries have committed to reaching net zero carbon emissions by that same year. 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 reductions, making it a valuable ally the fight against climate change.