Decarbonisation Technology - November 2022

If hydrogen is the answer to energy security, let’s talk carbon, not colour We are on the brink of a clean-hydrogen revolution, but we need a change of language and the development of a global clean hydrogen market

Maurits van Tol CTO, Johnson Matthey

T he simplest and most abundant element in the universe is key to tackling Earth’s most challenging problem – climate change. It is an oft-repeated joke that ‘hydrogen is the fuel of the future, and always will be’, but its time really has come at last. Soon we will see hydrogen working alongside other green technologies – cutting carbon emissions and helping to achieve net zero. Hydrogen can help decarbonise activities that electrification cannot. Think shipping, HGV trucks and buses, and industrial processes that need very high temperatures, such as steelmaking. We cannot reach net zero without it. The hydrogen colour naming convention has now run its course. It has been an engaging and memorable way to classify what is, ironically, a colourless gas, but what is needed now is a more nuanced approach Technological advances in this field are everywhere. Johnson Matthey’s HyCOgen process, for example, uses clean hydrogen and atmospheric or waste CO₂ to produce syngas, which can be upgraded into sustainable aviation fuel, for example, and dropped into existing supplies (Johnson Matthey, 2022a). As a fuel, hydrogen leaves behind only water, and none of the CO₂ or pollutants associated with fossil fuels. But before we can really declare this to be a clean-energy vector, we need to consider the carbon footprint associated with

its production, and it is here that things start to get complicated. Front-runners Right now, most hydrogen is made by reforming natural gas – a process that creates so-called ‘grey hydrogen’. But this process also yields CO₂, making it ripe for replacement. We will rely on two technologies in the future: the first is ‘blue hydrogen’ – created in the same way as grey, but with the troublesome CO₂ captured and stored. Second, there is green hydrogen, produced by the electrolysis of water using electricity from renewable sources, such as wind or solar. There is a rainbow of colours, too, including pink (nuclear), turquoise (methane pyrolysis), and even white (naturally occurring and mined from rock). However, I believe the hydrogen colour naming convention does not tell the full story. Though an engaging and memorable way to classify what is, ironically, a colourless gas, what is needed now is a more nuanced approach to hydrogen nomenclature. Let’s talk carbon It is more appropriate to talk about the carbon intensity of hydrogen. The ease of the colour- naming convention tends to invite simplistic comparisons of hydrogen production routes. For instance, it is common to see arguments favouring green hydrogen (electrolysis from renewable electricity) over blue hydrogen (natural gas + CCS) because the blue variant still produces CO₂ and uses a fossil fuel (natural gas) as a feedstock, and dealing