The Colours of Hydrogen...

Hydrogen is a colourless, odourless, tasteless and non-toxic gas that is the simplest of the chemical elements, consisting of a single proton and a single electron. There is currently a huge amount of media attention about hydrogen, which reference it being many different colours such as blue, grey, green, pink etc. As molecular hydrogen doesn’t typically exist in nature so needs to be generated by a process; these hydrogen colours mentioned in the media do not have different characteristics or chemistries but describe the process by which the hydrogen is formed. The hydrogen formed is still completely colourless and it actually burns with a very pale blue flame, which is almost impossible to see with the naked eye in daylight…so what do the different hydrogen colours really mean?

BROWN – Brown hydrogen is produced from coal through a process called gasification, which involves heating the coal in the absence of air and gives off substantial quantities of carbon dioxide as a by-product. Hydrogen produced from coal can also be known as BLACK hydrogen depending on the type of coal used. This process has existed for a long time, with the product often known as town gas (a mixture of hydrogen, carbon monoxide and carbon dioxide), which in the UK was piped to households to be burned for heat and hot water before North Sea discoveries allowed us to rely on natural gas as we do today.

GREY – Grey hydrogen is produced from natural gas, produced by the oil and gas industry. High temperature and pressure steam is mixed with high pressure natural gas (mainly methane, CH4) to split the carbon from the hydrogen in a process called steam reformation (aka SMR). This process gives off substantial amounts of carbon dioxide. A high proportion of hydrogen produced right now is grey.

BLUE – Blue hydrogen is similar to grey hydrogen. It is produced by the same process of steam reformation but the carbon dioxide by-product is captured and stored or utilized rather than being allowed to escape into the atmosphere.

TURQUOISE – Turquoise hydrogen is also produced from natural gas but through a different process called methane pyrolysis. This essentially involves ‘cracking’ the methane by heating it to around 800 – 1000 degrees Celsius in the absence of air and water, which separates the hydrogen and carbon to only give off solid carbon as a by-product of the hydrogen production. Catalysts can lower the required temperature and this method may draw some attention as the hydrogen economy takes hold. The solid carbon by-product could have use in building materials but also in steelmaking or potentially in producing innovative materials such as graphene.

WHITE – Although hydrogen is very rarely found as gas in our atmosphere, it does occasionally exist in nature but in accumulations within geological formations, underground. This can theoretically be produced similar to how natural gas is in the hydrocarbon industry, but we currently don’t have any viable processes to produce it from this source.

GREEN – This is the production of hydrogen from renewable energy sources through electrolysis. Electrolysis is an electrochemical process where electricity splits water into hydrogen and oxygen with zero emissions being produced as by-products. If the electricity source is solar, this can also be know as YELLOW hydrogen. Have a read of our last blog about electrolysis

PINK – Pink hydrogen is also produced through electrolysis but the source of the electricity is nuclear rather than renewables.

Much is being made of a hydrogen economy in the media and a growing amount of politicians, experts and personalities are promoting blue and green hydrogen as big contributors in the global fight against climate change. At HydroGenesis we believe blue hydrogen will play a big part in developing the hydrogen economy but our focus is on green hydrogen as we believe this to be the ultimate answer to energizing our society in an environmentally friendly way. Using hydrogen as an energy storage medium for renewable energy sources, which are intermittent in their energy production, is in our opinion the best way to maintaining our energy intensive way of life and creature comforts while protecting the planet.