The US navy is planning on introducing the ability to generate jet fuel from seawater on its nuclear aircraft carriers in the 2020s. The process works, it just

The US navy is planning on introducing the ability to generate jet fuel from seawater on its nuclear aircraft carriers in the 2020s. The process works, it just takes a tremendous amount of energy (hence the nuclear carrier part) and it requires a lot of water to create a gallon of jet fuel (20,000 gallons I believe for a singe gallon of jet fuel). The toughest part, however, is that the process would release methane gas into the air. So it's unclear if it's really greenhouse-gas neutral. In theory, though, if you could trap the methane and then sequester the hydrocarbons you made, you'd have a way to pull CO2 out of the atmosphere.