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    There has been a lot of well-known public figures talking about the role that hydrogen may play in the global shift to a more sustainable future. Some have expressed skepticism about the usefulness of hydrogen but many think it could help reduce emissions in a number of sectors, including transportation and heavy industry. There has been a lot of media debate recently about hydrogen and its importance as a tool in securing a low-carbon future. However, the vast majority of its current production is still based on fossil fuels. According to a September 2022 tracking report from the international Energy Agency, low-emission hydrogen production in 2021 accounted for less than one percent of global hydrogen production. If hydrogen is going to have any role in the planned energy transition, then hydrogen generation needs to change in a big way.
     Rachael Rothman is co-director of the Grantham Centre for Sustainable Futures at the University of Sheffield. She said, “The first thing to say is that hydrogen doesn’t really exist naturally, so it has to be produced. It has a lot of potential to help us decarbonize going forwards, but we need to find low-carbon ways of producing it in the first place.” Hydrogen production methods are identified by different colors. “About 95% of our hydrogen today comes from steam methane reforming and has a large associated carbon footprint, and that’s what’s called ‘grey’ hydrogen.”
     According to the energy firm National Grid, grey hydrogen is created from natural gas or methane. The greenhouse gases associated with the process are not captured. This constitutes the big carbon footprint that Rothman refers to. The dominance of such a method of hydrogen production is clearly not in keeping with net-zero goals. As a result, an array of sources, systems and colors of hydrogen are now being suggested as alternatives.
      These methods include green hydrogen, which refers to hydrogen produced using renewables and electrolysis in which electric current splits water into oxygen and hydrogen.
     Blue hydrogen indicates that natural gas was used in generation with carbon capture utilization and storage. There has been an intense debate about the role that blue hydrogen could play in the decarbonization of society.
      Pink hydrogen has been attracting attention lately. Its process incorporates electrolysis. However the key difference between it and green hydrogen is that pink generation depends on nuclear power.
      Rothman said, “If you split … water, you get hydrogen and oxygen. But splitting water takes energy, so what pink hydrogen is about is splitting water using energy that has come from nuclear. This means that the whole system is low carbon, because … there’s no carbon in water … but also the energy source is also very low carbon because it’s nuclear.”
     Rothman pointed out that while electrolysis could be used with nuclear power, something called a thermochemical cycle could also be driven by nuclear power. She explained that the thermochemical cycle uses extreme temperatures to split water into oxygen and hydrogen.
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