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June 1, 2021

What is turquoise hydrogen?


You might have heard of hydrogen being referred to by different colours. Grey hydrogen, blue hydrogen, turquoise, green - what does it all mean? For starters, under typical temperatures and pressures, hydrogen occurs as a colourless, odourless, non-toxic gas with the molecular formula H2. Unfortunately, there isn’t a rainbow of hydrogen floating around with all these different colours. The colours only refer to the method of hydrogen production.

Grey hydrogen refers to hydrogen produced from fossil fuels with carbon dioxide (CO2) emissions. Today, most of the world’s hydrogen is produced by steam methane reforming, often referred to as SMR. SMR uses high temperatures, most often generated by the combustion of methane, to cause a reaction between methane and water (the “steam” part of SMR) to create hydrogen and carbon monoxide. Additional hydrogen is produced when the carbon monoxide reacts with water to form CO2.  For grey hydrogen, the CO2 is released into the atmosphere. Grey hydrogen is considered “blue” when more than 90% of the emitted CO2 is captured and sequestered via Carbon Capture and Storage (CCS). CCS is often accomplished by transporting CO2 by pipeline to a geologic storage site, where it is injected underground. Grey and blue hydrogen are relatively inexpensive to produce. Still, the impact of CO2 emissions and the limited regional availability of geologic carbon storage are long-term risks for these colours of hydrogen.

On the other end of the spectrum, there is green hydrogen. Green hydrogen typically refers to hydrogen produced by the electrolysis of water. Each molecule of water is made up of two hydrogen atoms and one oxygen atom (H2O). Electrolysis breaks apart the molecular bonds in water, creating hydrogen and oxygen gas. Green hydrogen, in theory, has no carbon emissions; however, the energy required to break the hydrogen-oxygen bonds in water is very high. For this reason, green hydrogen production is very energy-intensive and expensive. If carbon-free electricity is not available, green hydrogen can have a carbon footprint exceeding some other colours of hydrogen.

Turquoise hydrogen is not quite blue, but not quite green either. Turquoise hydrogen uses a hydrocarbon feedstock, such as methane (CH4) in natural gas, as the source of hydrogen atoms. However, turquoise hydrogen uses pyrolysis to create solid carbon particles instead of converting the carbon to CO2, like grey or blue hydrogen. With pyrolysis, methane is heated in the absence of air and water to form hydrogen and solid carbon. Unlike green hydrogen, splitting a methane molecule requires much less energy than splitting a water molecule, so the process is relatively inexpensive. Because it uses a hydrocarbon feedstock and can produce affordable hydrogen, it’s kind of blue. But because there is no CO2 generated, it’s kind of green. When combined, blue and green make turquoise - our favourite colour of hydrogen. 



Aurora Hydrogen is developing a technology that uses efficient microwave energy to heat natural gas in the absence of oxygen and water (pyrolysis) to produce hydrogen and solid carbon while avoiding the generation of CO2. The technology is highly scalable and modular; units can be installed anywhere there is natural gas and electricity. Hydrogen production using Aurora's technology has the potential to reduce global CO2 emissions by over 500 million tonnes per year.