Assuming that a carbon neutral fuel for cars has to be used, what would be most practical and efficient? (Assumption: there is electricity from hydropower/nuclear or possibility to grow plants for biofuels) 1) Hydrogen from water hydrolysis? (If I get it right, production is simple but the challenge starts with storage of liquid hydrogen) 2) Go next step and get methane from Sabatier reaction? http://en.wikipedia.org/wiki/Sabatier_reaction 3) Go even a step further and get a liquid fuel through steam reforming? http://en.wikipedia.org/wiki/Steam_reforming#SMR 4) Biomass gasification and get fuel a liquid fuel from it? 5) Or maybe just produce biofuels from crops / algae / whatever? Which of those process would be worth using? With contemporary technology, but some serious adjustments in infrastructure are possible. I mean not only energy loses at production but also practicality of easy to transport and storage of fuel.