As a handwavy intuition pump, water expands 1,000 times when it boils and turns to steam. Boil 1 litre of water, get 1,000 litres of steam. To go backwards here

As a handwavy intuition pump, water expands 1,000 times when it boils and turns to steam. Boil 1 litre of water, get 1,000 litres of steam. To go backwards here means sucking in 1,000 litres of pure steam and paying the cost of chilling it to condense it and get 1 litre of water back out. After that, air is not pure steam, it's about 4% water vapour, or 25x less concentrated. To go from air to water means sucking in 25,000 litres of air, and paying the cost of chilling it, to have enough air going through to contain 1,000 litres of water vapour, to get 1 litre of liquid water back out. Carbon is not 4% of the air, it's 0.04%, a thousand times less concentrated again. To get "1 litre of carbon solid"[1] out means sucking in and paying the cost of processing 2,500,000 litres of air. [1] as if that means anything sensible here, lol.