Malin Marine Services are currently investigating low emission technologies as part of our Low Emissions Workboats in the Aquaculture Sector (LEWAS) project and we thought we would share some of the interesting facts we have learned. This article is a very brief and basic introduction into the colours of Hydrogen and why green Hydrogen is critical to our green recovery. 

Hydrogen is viewed as a major fuel source of the future, when used for energy generation in a fuel cell, the only emission is water.  However the production of Hydrogen isn’t always as green as the fuel itself.  In fact, there are an array of colours used to describe Hydrogen production, namely, green, blue, grey, brown, pink and turquoise.  Currently most of the world’s Hydrogen production is grey, followed by brown, with green Hydrogen making up only a fraction of a percentage of global production.  The colour has nothing to do with the gas itself, Hydrogen is a colourless gas, the colours are assigned as a result of the production method. 

Grey Hydrogen makes up the most significant proportion of the world’s supply today, perversely the green fuel of the future is actually derived from somewhat less green fossil fuels.  Typically, grey Hydrogen is produced from natural gas which, when processed produces Hydrogen and Carbon Dioxide as a waste by-product.  Blue Hydrogen is produced by the same industrial process as grey Hydrogen but importantly the Carbon Dioxide is separated and captured for storage, deep underground.  The second major source of Hydrogen is coal.  When heated with water coal produces a mixture of gasses one of which is Hydrogen.  Other waste by-products include Carbon Dioxide and Carbon Monoxide which are the very pollutants eliminated through using hydrogen as a fuel directly. 

This then brings us to green Hydrogen; this has the greatest potential for completely eliminating Carbon emissions.  However, Green Hydrogen makes up only a fraction of a percentage of the global production figure.   Green Hydrogen is produced by passing an electric current through water (electrolysis).  When the electricity used in this process comes from renewable sources, wind, solar, wave etc. the Hydrogen produced is categorised as green Hydrogen.  When the electricity used in electrolysis is a result of nuclear energy the resulting hydrogen is said to be Pink Hydrogen.   Interestingly turquoise Hydrogen is produced from thermally splitting methane to produce Hydrogen and solid Carbon as a waste by-product.  To be categorised as Turquoise Hydrogen, the energy input into the process needs to come from renewable sources. 

The only renewable and therefore sustainable source of hydrogen is green Hydrogen.  Utilising the growing renewable energy supply chain enables the excess electricity provided by renewable sources to be used to generate green Hydrogen, this can then be stored and the energy that would otherwise be lost when supply exceeds demand, continues to be useful.  For that reason, the colour of Hydrogen really does matter…