End of oil company's, page-13

Every process that separates hydrogen and carbon dioxide from sea water requires more energy than is produced. If it didn't it would be the chemical equivalent of a fabled perpetual motion machine! In short the stored energy to make a fuel has to come from somewhere.

In the case of nuclear it is produced when a star dies, with coal and oil the production has been natural geology and involves billions of years. Wind and waves up to decades of sunlight is required, and with Solar it is direct from the Sun.

In the end making fuel this way would be far from green or economic - as it will waste useable energy. The energy input would be better used elsewhere unless running a war machine is the best use we can find for our energies.