The gas could provide the critical missing piece in decarbonising the global economy. But can the hydrogen itself be sourced cheaply and carbon-free?

One exciting new application could be to replace the coal used in steel-making. Manuela Saragosa speaks to Martin Pei, chief technical officer at Swedish steel company SSAB, which is collaborating on a pilot scheme for the new technology. He says hydrogen produced from renewable energy can generate the intense heat needed in many heavy industries like his, that is currently only achieved by burning fossil fuels.

Could hydrogen also be used to replace the natural gas currently used for winter heating in many homes in northern latitudes? That is the contention of Marco Alvera, chief executive of Italian gas pipeline operator Snam.

The key question is whether the cost of producing hydrogen from solar and wind energy can be brought down to a competitive level. Pierre Etienne Franc of French industrial gas company Air Liquide says they're working on it.

Producer: Laurence Knight

(Picture: High pressure hydrogen fuel filler nozzle for refueling hydrogen powered commercial vehicles; Credit: Stephen Barnes/Getty Images)

Outside The Walls - Part 2