The predominate proportion of current hydrogen production is made up of blue hydrogen, according to an ISS Insights report. The report’s hydrogen rainbow is composed of green, blue, grey and black/brown hydrogen, with green covering the cleanest and most sustainable production, whereas black/brown is the most emissions intensive. Hydrogen’s key limitations are energy being lost at each stage of the supply chain process to various degrees depending on the production method, with the losses sometimes being substantial, the report said, noting that hydrogen is a less efficient solution than electrification. Further, despite hydrogen being branded a “Swiss Army knife”, there are cheaper, safer and simpler alternatives to it. Green hydrogen produces no emissions but is prohibitively expensive in many cases, meaning grey hydrogen – through which hydrogen is separated from natural gas via steam methane reforming – currently produces the majority of hydrogen. Carbon dioxide is released into the atmosphere from the production of grey hydrogen and has an approximate 9.9kgCO2eq/kgBH2 emissions intensity, and while blue hydrogen has been seen as ‘clean’ or ‘low-carbon’, the report quoted an academic study suggesting blue hydrogen is in fact only 9-12% less emissions-intense than grey hydrogen in a best-case scenario. Methane emissions associated with natural gas extraction are uncaptured and substantial for both blue and grey hydrogen. While a sequestration rate of 80-90% is theoretically possible with carbon capture and storage technology, this is a rate which has yet to be achieved at a commercial scale, ISS Insights said.