I remember back in the 80's some work was done on cars using Stirling engines.  If that had been kept up, by now there would be cars that could run on anything that burns.
You can go one better.  Plug-in hybrids will run on anything that generates electricity; you can't burn wind or hydropower, but you can charge batteries with it.
EP, you've been pounding the table for many months on the viability of plug-in hybrids, and I think you are spot-on.  The future of auto transport in the developed world, IMHO, lies in electric hybrid (or perhaps one day fully electric) vehicles.  Battery life and charging times may improve dramatically as a result of nanotechnology.


We don't need radically improved batteries either; we can do one heck of a lot with old, cheap lead-acid.  We'd have to redesign our vehicles to make good use of them, though; this prevents e.g. Toyota from turning an Echo into a plug-in Prius with 50 miles of gas-free range.