CO2 is a powerful warming gas but there's not a lot of it in the atmosphere - for every million particles of air, there are 410 of CO2.

The gas is helping to drive temperatures up around the world, but the comparatively low concentration means it is difficult to design efficient machines to remove it.

But a Canadian company, Carbon Engineering, believes it has found a solution.

Air is exposed to a chemical solution that concentrates the CO2. Further refinements mean the gas can be purified into a form that can be stored or utilised as a liquid fuel.