Appearing first as a dot on the horizon, the remote Nini oil field on Europe’s rugged North Sea slowly comes into view from a helicopter.

Used to extract fossil fuels, the field is now getting a second lease on life as a means of permanently storing planet-warming carbon dioxide beneath the seabed. In a process that almost reverses oil extraction, chemical giant INEOS plans to inject liquefied CO2 deep down into depleted oil reservoirs, 1800 metres beneath the seabed.