BINGO!!! That is whole point of this thread. Materials to make consumer goods just dont fall from the sky and recycling isn't all it's cracked up to be, it's still very dirty. The only "Green" vehicle is you and a pair of good shoes.
Anytime 'work' is being done something gets changed and the 'by-product' is dirty. The best you could do to is make that pile as small as possible. That would be be burning hydrogen and oxygen together. Today that would be called hho gas but you need power to produce it but it would be made on demand so it would be non-explosive in it's raw form, water.
If efficiency is important so is the supply end, in Canada NG is the biggest commodity we have in that class (fuel for transportation). That is what we should be developing, get the box you want it wrapped in would still be possible, new ($$$) or from a kit ($$) or shared expenses ($). If there is an existing e-car available then something already past the R&D phase should just be backed to make the transition as cheap and as fast as possible. Use the gas to make electricity as in the home model below and power your home via that, not free but it might be better for you as if the grid went down you could still charge your car and run your house. If the NG quit it could most likely be converted to run on propane. Nor is it pollution free as it has by-products not desired and getting it to your place is going to be dirty work somewhere.
Residential Fuel Cells – Natural Gas | mapawatt
My favorite is still the salt water battery, add the brine (best % to still be determined) is added and the power is on, since it does not produce high amps it would be used as a 'trickle charger' and just stay on 24/7 if need be. Anybody with access to the ocean would have power, pump some onto land, let some water evaporate till you get the best solution and then start mining/recycling whatever two metals work best. It may work out that many variations work, some just work better than others but you have to use what you have access to. (getting a fine layer of salt everywher will exterminate life as it kill all green things, a small price to pay for social advancement)
Wind turbines have access to unlimited energy it just doesn't work as advertised. Solution, make some wind by making the prop and genset much smaller in size and put up a very large sail/windsock that directs all the wind it catches onto that small dia fan. The sail and mast would be good for 20 yrs with little or no maintenance to the table it would have to be swiveling on to maintain the best angle of attack for the wind conditions.