> The obvious answer is the atmosphere. That's also the premise of carbon sequestration. The problem is that CO2 isn't actually particularly abundant. It's curr

> The obvious answer is the atmosphere. That's also the premise of carbon sequestration. The problem is that CO2 isn't actually particularly abundant. It's currently hovering around 400 parts per million - that's about 0.04% of air. To make a kg of hydrocarbon you need to process an awful lot of air to get enough CO2. That all takes energy. A lot of energy. Suddenly your round trip efficiency is practically zero. If these guys have cracked that problem, it would be fantastic. I hope they have, but I suspect they haven't. Isn’t biofuel precisely this?