Britain should invest in turquoise hydrogen

sir – Ambrose Evans-pritchard covers much of the ground in the debate on Britain’s future manufacture of hydrogen (“Green fundamentalists are wrong to call for a ban on ‘blue’ hydrogen”, City, August 26).

Blue hydrogen is made from a process of steam methane reforming, where methane is chemically reacted with high-pressure steam. Unfortunately, this process produces lots of carbon dioxide – around 5.5 tons for every ton of hydrogen. This is where the need arises for carbon capture and sequestration/storage. It is envisaged that these huge amounts of carbon dioxide would be compressed and pumped underground into empty old oil caverns.

It’s not just Extinction Rebellion that is sceptical of this idea. There has long been scepticism because not only will (at best) only 95 per cent of the carbon dioxide be captured and stored, but questions remain whether it can be kept in underground chambers at very high pressure without any leaks for hundreds, if not thousands, of years.

So an alternative to steam methane reforming should be considered, and the obvious one is methane pyrolysis. Here hydrogen is dissociated in a high-temperature furnace into its elemental components: hydrogen (termed turquoise hydrogen) and solid carbon. No carbon dioxide is emitted. Solid carbon can be easily sequestered or commercially used without environmental impact.

The energy required for this is less than for steam methane reforming. And of course no energy will be needed to transport and compress vast quantities of carbon dioxide in underground chambers.

One might expect, therefore, that in the near future turquoise hydrogen will be a serious alternative to the blue variety. The Government should beware committing itself to the latter.

Dr John Philip Nicholson

Retired lecturer in physics, University of Strathclyde

Glasgow