Labelling hydrogen by colour is a popular way of differentiating its production process. The hydrogen ‘rainbow’ includes brown hydrogen, made using coal, and grey hydrogen, produced from natural gas. Blue hydrogen is grey or brown hydrogen produced using carbon capture and storage (CCS) to cut carbon dioxide emissions, while green hydrogen, produced from water through electrolysis fuelled by renewable power, offers the potential for near zero emissions.

As momentum builds around low-carbon hydrogen, the industry is having to look past colour labels. The future of low-carbon hydrogen hinges on governments putting in place regulations, subsidies and other incentives that are increasingly tied to the carbon intensity ‒ rather than the colour ‒ of the hydrogen produced.

Calculating hydrogen’s carbon intensity is complex. For green (electrolytic) hydrogen, emissions can range from almost zero to levels beyond those of brown hydrogen. Green hydrogen is, in principle, made using 100% renewable energy. In practice, however, what is described as ‘green’ can also be produced using power from a grid that relies heavily on fossil fuels.